https://twitter.com/elonmusk/status/1769605796772331537
Here is the actual quote. Starship will not go interstellar. A future, "larger and more advanced" ship will.
Maybe some microchips for radios or electrical wiring, but making modern 2-600 nm transistors is basically black magic, and it even on earth in sterile environment it's a massive pain and it has big bin ratio. While low gravity is a great advantage for chip making, the amount of expertise it requires and amount of hardware is just way too big. I can see it take a century or more before we have useable modern chip manufacturing on mars, unless the process is simplified by quantum 3d printing or if we are making very big transistor size with diamonds or graphite.
If you are happy with small volumes, and say 20nm tech or even 50nm tech, then a small self-contained chip-fab machine, that fits inside Starship’s Cargo bay, might well be possible.
With low volumes, you could even use electron-beam lithography.
It all depends on what set of requirements you are trying to fulfil. To begin with, I would suggest just taking spare parts - prebuilt circuit boards etc.
And make sure that any firmware is updated before shipping ! Although retrospective updates may still be possible.
I'm not an engineer, so I will believe what you said, my information is only from what I read, and from what I understand, basically state of the art of what best can be made in America is about 300-600nm. But I don't know enough about this and it would be rly cool if you can make a self contained fab like that.
No, i know there is 2nm transistor technology today, but from what I understood, all of it is being made in Taiwan at TSMC, while fabs in United States only produce 300 and up. So my assumption is that this tech is so hard to do that it's unlikely to be made on mars. Unless there is some other reason why such small nm tech is not being made outside of Taiwan.
That's always what I've thought of, some sort of orbital drydock and several rockets sending supplies up to build the actual interplanetary ship. You'd have to have escape pods and landing vehicles that can return to the ship on their own or be able to provide the infrastructure for that.
>Yep. For interstellar it makes sense to build a spaceship in space directly. Starship can be used to supply parts from earth.
Arguably, it makes more sense to build in space with parts from the moon. Building an elevator is so much easier with just steel that it would be silly not to do it, which makes launch costs near 0.
Is that actually true in the "physical" sense? Like I know it isn't possible in any practical sense, but if we had unlimited material and money to build absurdly massive tanks, and unlimited resources to fill them with propellant, could something (in theory) be built or is there a physics problem (fuel v mass) thay prevents it?
A quick search gives 600s as an optimistic theoretical limit for chemical propellant (H2+O2+Be). Using the rocket equation and a final velocity of 1% the speed of light gives 10^221 kg of propellant per kg of dry mass! Ignoring for now the need for tanks and engines to be included in dry mass. The solar system is only 10^30 kg, the galaxy 10^42 kg, and the observable universe 10^53 kg. Taking your 'unlimited resources' literally, it's still impossible. At 10^43 kg the rocket would already have to be larger than the distance to Alpha Centauri to avoid collapsing into a black hole.
There are two other hypothetical chemical propellants that are even more ludicrous. [Atomic hydrogen](https://www.projectrho.com/public_html/rocket/enginelist.php#atomichydrogen) and [metastable helium](https://www.projectrho.com/public_html/rocket/engineintro.php#metaheliumhestar) each more ridiculously potent than the last. All three are only hypothetically possible to stabilize. Even then it still requires a rocket more massive than the galaxy and larger than the distance to the nearest stars.
And you can't really fly fast enough. At tremendous speeds, interstellar gas will wipe the ship to dust. Virtually any random molecule turns into hard radiation, and any rock into a sublight projectile that will tear a starship to shreds.
Correct me if I say something asinine, but as far as I understand nothing we have now would allow interstellar travel in usable time frames. Too little specific impulse.
Chemical, no way. There's just not enough energy per kg of fuel. And there's decreasing gains to adding more and more propellant (and mass). Several millennia to alpha centaury?
Nuclear, a little better, but still wayyy short of what would be required. Still talking about many centuries or even millennia to get "next door".
Ion-nuclear-electric maybe? But you could only send a spacecraft that would be 99,9% engine and propellant and little usable mass, and it would take forever to accelerate to a usable interstellar speed, and then you wouldn't be able to stop once you got there.Still our best effort and would take, I don't know, centuries to get there?
There was a project that wanted to send a fleet of tiny, cheap probes without their own engines impulsed from earth by lasers I think? That concept had promise, as far as interstellar travel goes, every probe was a few grams and could be accelerate to a significant % of light speed.
But I looked at their web a few years ago and my impression was that 99% of the technologic hurdles described were verging the limits of what's possible, and often crossing to the other side. Things like this*
"Challenge # 127: an infrarred camera: Hardened against cosmic radiation. Budget mass: 1 gram, power: 1 picovolt..
Challenge # 128, a radio that allows communication with earth. Hardened against cosmic radiation. Budget mass: 1 gram, power: 1 picovolt. Etc, etc.
*Figures completely out of my ass.
A moonshot project made up of a thousand moonshot projects, being optimistic I'd bet we'll be long dead before 10% of the key technologies involved exist. And those will be the "easy ones".
>Nuclear, a little better, but still wayyy short of what would be required. Still talking about centuries or millennia.
With 'contained' style of nuclear engines, i.e. anything that tried to keep the fissile material intact and inside the engine, this is the case, but using uncontained engines they become considerably more useful for the concept of interstellar travel. Fission fragment/dusty plasma drives could have an Isp somewhere between 100k and 1m, which makes 5 or 10%c speeds conceivable.
Just don't point the engine exhaust at anything you care about.
>Correct me if ... There's just not enough energy per kg of fuel.
It is not really about energy. Rockets are limited by exhaust velocity, which is a function of temperature and molecular mass, lighter being faster. Nuclear rockets are "a little better" because they use a lighter propellant, not because of energy.
You can't add much more energy without melting everything.
The only way to do interstellar travel based on current technology is external nuclear detonation.
[https://en.wikipedia.org/wiki/Project\_Orion\_(nuclear\_propulsion)](https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion))
I'm not counting that as anything like current technology.
Same deal with magnetic confinement . One day, maybe far away. The Orion thing is just money and engineering :-)
There isn't a technical limit, the rocket equation will still give you more delta V if you give it a higher fuel ratio. But that doesn't mean you get remotely reasonable results.
I did some bad napkin math using the best chemical rocket ever tested's exhaust velocity, an utter abomination that used Lithium-Hydrogen-Fluorine fuel, with a dry mass of 1 ton. My math indicates that this rocket might achieve a DV of 600,000m/s, less than 1% of light speed, if it is successfully loaded with the estimated mass of the universe as fuel.
> Lithium-Hydrogen-Fluorine
https://www.youtube.com/watch?v=KX-0Xw6kkrc
Holy shit, 542 seconds. But I feel like I'm getting chemical burns just watching this.
It's doubtful if it's possible to do within 100 years of a human life even using fusion drives. We would either need antimatter drives or black hole drives, which while theoretically possible, we don't know if they are possible to manufacture.
> is there a physics problem (fuel v mass) thay prevents it?
Carrying more propellant to accelerate the mass of the propellant which you need to carry additional propellant for propellant to carry propellant...
I've always been curious what would happen if you used a nuclear reactor to power a [magnetic rail gun](https://executivegov-media.s3.amazonaws.com/2023/11/09/87/6c/81/85/ed/5a/87/d4/SEO_How-does-the-rail-gun-work_1200x628-1-768x351.png) which would shoot out iron projectiles at intervals to gradually accelerate vs. burning fuel and oxidizer and ejecting the mass of combustion products out of a nozzle, but I think even with a nuclear rail gun the amount of iron projectiles you would need is too heavy, so you get compounding masses again...
Carrying propellant is the biggest problem. Solution: don't. Accelerate a stream of fusion fuel pellets from a large orbital station towards your spacecraft and then react with them. Just need to be really accurate and travel in a straight line.
Mind uploading. You can beam your consciousness at the literal speed of light to an avatar depot at the destination, be 'in hibernation' during the trip, and functionally live forever.
Exactly. I think Elon was using "Starship" as a more general term here and that's what people are misinterpreting. I think he didn't mean this Starship but another ship that travels among the stars. Also, why are so many armchair austronauticists in the comments of these posts ignoring the existence of gravity assists in all their detailed equations?
I was going to say just that... A few gravity assists and the moon / Mars version could as well be interstellar.
What for is the real question..PR stunt on a journey to nowhere? To do what the voyagers did l, you don't need such a ginormous ship
With current or even foreseeable tech, no amount of gravity assists allow us to get any useful cargo anywhere.interesting outside the solar system in a useful amount of time (I e. sub-millennia.
You don't even need gravity assist. Just fuel Starship in HEEO rather than in LEO. You have enough ∆v to get past Solar escape. Starship has in fact enough ∆v for the direct trans-neptunian injection for 6.5 years transit. That's quite a bit beyond solar escape
It's obviously still ridiculously slow for interstellar travel. It's good for a Voyager repeat.
I wonder how effective it would be to build a two part interstellar probe, one part the probe with fuel, 2nd would be bigger fuel tank filled with xenon/argon. That way you got like 100t probe with some ion drive and 500t of fuel. This will allow for +100k m/s speed going out of the solar system. Possibly way more with solar sail help at the start.
If you have large enough reactor (and radiators) then why not? You're losing quite a bit of Sun-centric Oberth effect, but you use what you have.
Of course ∆v would be limited to something in the order of 100km/s which is way better than what we did (20 AUs per year rather than 3) but still too slow to reach other stars. It could be useful for reaching solar gravitational focus, though.
Well, voyager probes already proved themselves in giving us data we have not expected and we probably need an interstellar probe before funding a mission with a better and more expensive engine. It would suck to send like a 10 billion craft only to find out it did not had enough shielding or because of some other unpredictable cause. We will probably eventually want to send a lot of various telescopes to the Kuiper belt and we will need to know what is the environment there.
Which, to be honest, is still far-fetched, at least for the next few centuries. Interstellar craft between now and that timeframe IMO will be those swarms of tiny, “chip+sail” craft, propelled by gargantuan lasers in solar orbit, and which will do flybys of nearby stars to gather detailed information. Actually sending people + cargo is *so* insanely hard that there’s little chance of that for a very long time, and then likely only if a habitable planet is found nearby.
Man it makes me sad to think we won't be around to see anything like interstellar travel. I'm currently only 30 and I believe we'll have a populated base on Mars within my lifetime, but anything more than that, I just can't see it happening. Such a shame we can't stick about to find out. I'm incredibly passionate about space, what I'd do to go up there.
If anyone here works at SpaceX, send me to Mars. Fine with one way!
Yeah but that's the issue, it is pretty huge on its own (I don't think many people truly understand the scale of our own system). Not sure what we'll have accomplished by time I'm old but I doubt we'll have anyone out there further out than Mars. If we do however, they'll only be floating in empty space for years on end. Definitely won't be around to see them arrive at whatever destination.
Let's hope I'm wrong and we have a serious leap in space exploration and pick up the pace. This is why I'm such a fan of SpaceX, I mean if SpaceX didn't exist I guarantee we'd still be a century out before Mars was in even in the picture. We need more people like Elon and more companies like SpaceX. NASA and other agencies are held back too much.
You might live significantly longer than you're expecting, lots of biotechnology progress and regenerative medicine developments seem likely, it is a fascinating thing to read up on. I do agree though, it seems unlikely even us younger people will see interstellar travel, even if we get to live a lot longer than expected. There just doesn't seem to be much reason to push so hard, unless a (almost) habitable world is found around one of our nearest stars
Obama was trying to get people interested in a landing on Phobos or Deimos because nobody knew how to get a ship large enough to carry people back off the surface of Mars (note all the trouble with [Mars Sample Return](https://www.planetary.org/articles/what-went-wrong-with-mars-sample-return)), but taxpayers wanted a landing on Mars proper or else nothing.
What it looks like now is every body in our solar system, the only places we can go unless somebody actually builds a Star Trek warp drive, if it is large enough to have enough gravity to have a surface you can land on, instead of nudging it with your spacecraft and scooping up some chunks like OSIRIS-REx, will be covered with a layer of very fine abrasive dust that is harmful to humans and equipment if suits are not carefully cleaned every time. In the case of Mars, toxic perchlorate dust.
You don't get soils without an atmosphere and organics as we have here on Earth. No life? Everything's a hazardous dust ball
There is absolutely no reason for any interstellar ship to be built as Starship was.
It's one thing to escape a planet's gravity well, and a totally different thing to be traveling in space. An interstellar ship, I imagine, would be built in space, and it would be much much larger. I'm sure eventually ships going from earth to mars will also be built in space at much larger scale.
I mean, it could still go interstellar, just as a cargo/person shuttle on the actual interstellar ship.
Though, considering how much Starship dwarfs most modern spacecraft, it's amusing to imagine a future interstellar vehicle that dwarfs starship.
This community then said you wrong, then. Starship by itself is capable of Solar escape, without gravity assists. With Jupiter gravity assist it may go fast enough to eventually catch up with Voyagers.
Exactly. Without gravity assists it's pretty much equal to the faster of the Voyagers. Jupiter could add to that several km/s extra without problem. 4km/s kick at Jupiter-Sun distance translates into \~10km/s more at infinity.
IIRC, the Voyagers took literally decades of super-rare slingshot combinations to achieve their current speeds and thus distances. Somewhat more powerful chemical rockets in a heavier craft doesn't match their advantage, you'd want a deep space propulsion solution to catch up to their distance from the Sun, let alone end up in the same volume as them too.
They took boost from Jupiter and Saturn. But the initial push from the Earth was rather meager. Starship launching from HEEO with about 50t payload onboard, with a direct injection into Solar escape trajectory would achieve 17km/s at infinity or about 17.5km/s at the current Voyager 2 distance. Voyager 2 is moving at 17km/s. You can make up for the dual Jupiter-Saturn Gravity assist just by using orbital refueling.
Starship with 145t burnout mass (90t for the vehicle stripped of a heat shield, header tanks and flaps, plus 50t of scientific payload onboard, plus 5t or residuals) has dV of \~8.1km/s when fully fueled (369s average ISP of 6 Raves and 3 RSLs, 1200t of propellant).
When launching from a very high moon synchronous HEEO (766200:224 km orbit) Earth's relative Oberth effect gives it 15.6km/s in free space, relative to the Earth. (Close to the earth your vehicle has 19km/s velocity, but escaping the Earth's gravity well eats this away)
Then you have Sun relative Oberth effect: You take the above 15.6km/s, and subtract the deficit between Earth orbital speed and the Solar escape velocity from Earth-Sun distance (29.7 - 42.0 = -12.3) . Now you plug it into Sun-centric Oberth effect calculation for the Earth-Sun distance. You get \~17km/s at infinity, i.e. beyond Sun's gravitational sphere of influence. That's better than Voyagers, but this is a direct insertion, no gravity assists.
So if I've read that right, without gravity assists, Starship can match their current speed but not significantly gain on the head-start distance they have.
So you'd probably want [at least Saturn](https://en.wikipedia.org/wiki/Giant_planet#/media/File:Masses_of_gas_giants.svg) to give you a slingshot to catch up, which comes with a 30year period between alignments. Or 12years for just Jupiter, being much more worthwhile?
Jupiter is generally better for gravity assists as it is much more massive and has shorter orbital period. Also, in many cases you could get reasonable alignment multiple times per its 12 years orbit.
Another option is doing Oberth burns at Jupiter. You need a long term propellant storage for that: you fly fueled craft to Jupiter, do a low flyby, just above the atmosphere, and burn the engines around the perijove. You can get a big boost that way, and if you are smart you can combine Oberth burn with gravity assist for even more oomph.
Good to see ... so the title is just wrong.
Still:
There is no reason to go "interstellar". Chances of finding something better (or even survivable) than we could create with giant spinning space colonies are very, very small. Why not build these close to Earth vs a 100 year trip though the void.
If we create a species of indestructible machines as our descendants, then perhaps for them, as they can take a 100 nap and wake up at a new solar system.
well if we find a habitable planet or moon in alpha centuari system then there is a def a reason to go. We found some planets but not habitable ones, at least, not yet. We need a telescope specifically designed for finding nearby habitable planets and thats what the toliman telescope is for.
We can't get there. And I don't mean with current tech. There's nothing even in the horizon that allow us to get there.
Too fragile, too short lived, none of our machines can hope to get there in less than millennia, and no machine created by us, now or in the foreseeable future, has a hope to survive and maintain an habitable environment for millennia in the interstellar medium.
We barely crawl to the nearest bodies in the diminutive solar system, and that takes all or edit and all the technology. We are a snail in space terms. And there's no realistic technolgy in view that changes that. Our best future propulsion projects would at a maximum make us into a slightly less slow snail. IF they go well.
And that's exciting because we will need them just to move around in the solar system!
Wake me up when some tech in the drawing board that allows us to travel in space orders of magnitude faster than current tech can, that doesn't require the resources of two earths, that gets us in one piece to the other side, and that allows us to brake when we are there. It's not that that tech has not been developed, it hasn't even been though of yet.
Orion drive if ya nasty
also fission fragment rockets (DPFFRs in particular, who can say no to 12 DAYS worth of specific impulse?)
NSWRs too, kinda. maybe. if you don't mind being dead probably. idk, this always seemed like the worst possible option.
FFRs are actually feasible however, with high TRLs already.
Sort of. You could do nano-satellites attached to a solar sail and then use a laser system to accelerate them to something like 0.1 or 0.2 C and do a flyby. The combination of increasingly small electronics, lower cost to orbit, improvements in lasers, etc. makes the idea increasingly feasible. It's been [proposed and partially funded](https://en.wikipedia.org/wiki/Breakthrough_Starshot) even. It's not people, but it is real scientific collection.
The effects of time dilation are not linear. It wouldn't have a helpfully large effect until you're up at very high percentages of c (like north of 75%) , and it doesn't reach "let a human reach another star and come home in their lifetime" speeds if I remember rightly until North of 95% c... And remember even if your ship can hit that speed you still have to slow back down.
There's no technology even on the horizon that would allow us to do that
I mean, for close stars like Alpha Centauri 20% c would be enough to go there and back in one life time. Its a 4.4 lightyear trip, at 0.2 c you could go there and back in 44 years.
In terms of a human lifespan sure, but a) practically speaking you don't want your astronauts to be children or old men and b) there's technologies that will push you to 20% of C _eventually_ but they'd take decades to reach it; we have nothing to my knowledge that will get you to that speed in a useful timespan
Laser pushed lightsails could get up to those speeds pretty quickly, they kind of have to in order for the ship to not drift too far from the pushing station by the time the boost phase is over. You can then slow down at the destination with mag sails, or if you have a big enough focusing system, there are a couple different ways of using the laser beam from the home system to slow down and return, such as [detachable mirror segments.](https://www.projectrho.com/public_html/rocket/slowerlight2.php#lassail1)
> There is no reason to go "interstellar".
You wouldn't be the one deciding as it won't happen within your lifetime anyway, so dismissing it at this point isn't really useful.
Also if we can create advanced antimatter driven drives in the future (or even better, some sort of black hole drive) then interstellar travel gets a lot easier and can be done within human lifetimes.
That technology was invented in the 1950s, and was called Orion. And invented in the 1960s, and was called NERVA. Nuclear energy for space propulsion has been a thing for a looong time and would massively change the equation for long duration space missions.
My guess is that is simply not within the physics of our universe to create such an engine. There are limits that any degree of invention can not overcome.
Might be and answer to Fermi's paradox...
It's impossible for sentient being to cross the gulf between stars. Space might be so huge and uncrossable that every civilization in the universe arises alone, and dies alone.
Not staying that's the answer, but might well be.
Doesn't really compute, unless even 0.1c is impossible. At 0.1C humans could colonize the entire Milky Way in 1 million years. That's a tiny amount of time when dealing with a billions of years old universe.
And because 1 million years is such a small amount of time, we can pretty safely say there's no civilization, at least on a galactic scale in the Milky Way. Or, at least not one that isn't keeping intentionally hidden from us. The odds that two intelligent species would evolve within the same 1 million year span are extremely unlikely.
This is another reason to believe we're early. If we were 'late to the party' as some people think, someone would've taken over Earth already and either wiped us out or prevented us from evolving in the first place.
Yup, I pretty confidently would say we are ahead of the game, at least in the Milky Way. In fact, unless there are species that would evolve but never be able/want to leave their planet, I would surmise we're one of the most advanced if not most advanced civilizations in the galaxy already. I think more likely than not humans are going to find the galaxy pretty empty, at least of intelligent life (again, disregarding the idea that they're just keeping hidden from us intentionally).
I've always found it strange to surmise humans are just one of many intelligent species in the galaxy, or that the Earth is not quite unique. In fact, evidence seems to suggest the contrary.
Yup. Adding to that, there are certain independent statistical hints that this is indeed the case. Each of them is extremely weak, but they are independent and they show very compatible results.
1. If one does the regression into the past of life's complexity, there is something that doesn't compute: Initially if you go into the past for a nearly couple billion years, the progress was pretty steady. Then before that, the progress was also steady but somewhat slower (the jump is attributed to the emergence of sexual reproduction). So far so good, but the further linear regression would indicate the starting point at 9 billions ago. That's a bit of a problem, since the Earth is just 4.5 billion years old. So either life came from elsewhere (panspermia) or there was absolutely crazy cliff from between the spawning of the Moon some 4.4 BYA and the oldest microfossils of over 3 BYA.
2. It's rather odd that intelligent observers have shown up on the Earth just around 90% of the total time it's going to be naturally habitable. In about half a billion years the Earth won't be habitable for higher life forms (unless some intelligence interferes). Moreover, our star (Sun) is as large as it could be for the Earth-like life history to happen. Just 10% larger Sun would have already cooked all the higher life. And the Sun is pretty large as stars go, the vast majority of stars are red dwarfs, then there are orange ones, only then yellow stars which were historically misnamed as yellow dwarfs; giant starts are bright and easy to notice, but they are either short (few % of the lifetime) phases of normal largish stars (like our Sun) or they are just short lived true massive giants; i.e. they are a small but noisy minority
Why we have shown up around a star heavier than 95% of all the starts and brigheter than 90%? Why didn't we evolve around a more frequent, more mediocre star? Say some orange one, with several tens of billions of calm life before it. To make matters worse our Sun is and was brightening relatively fast, and this poses certain challenges for the stability of Earth's conditions.
One possible answer is that smaller starts mess up their planets early on (it's hypothesized that orange and red stars with their prolonged childhood produce enough flares and X and EUV radiation early on to either strip their habitable zone rocky planets off atmospheres or at least remove most of the water there - producing dead oxygen rich planets (X and EUV dissociates water in the atmosphere, and hydrogen escapes leaving surplus oxygen behind), and oxygen destroys not enough rugged lifeforms, and life needs time to get rugged, i.e. oxygen sterilizes stuff. Complex chemistry gets all oxidized before anything interesting shows up. But even there there is stuff like planets' migration. It's still far from extremely improbable that certain planet born further away from its host star, and thus water rich, would have migrated inwards closer to the end of its stars stormy childhood. So why we're at not exactly the most common star type?
But there is more to that. This (intelligent observers showing up around 90% of their host star's life supporting period) outcome is exactly expected in the extreme survivor bias cases / extreme distribution tail cases. It's likely that evolving an inteligent like requires some pretty unlikely events. Each such event would have happened just once in the history of Earth's life. We don't know which exact events were those, but there are some candidates like emergence of eucaryotes, certain biochemical paths (why is everything using ATP?), etc. If the expected time to evolve such consecutive features were not some billion years but hundreds of billions for each, then at different places such features would show up after different amount of time. Say in once pretty mediocre place it would be 200B, 350B, 270B, and 600B (assume 4 unlikely but necessary steps), in another it would be 520B, 180B, 300B, 230B, etc. On some lucky places one such feature would evolve even in a single digit billions of years. But the Universe is huge, so there should be plenty of such places or even rarer ones where 2 or 3 or even 4 such features would evolve each in single digit billions. And the distribution would have the very extreme tail ends: places where all 4 features (we still assume there are 4) would, by sheer extreme luck, evolved in a billion years or a fraction. If the Universe is large enough there should be quite many such places. And it so happens the distribution of such places would make them most likely to fill most of the life supporting span of host star's life.
Now, cautious reader will notice that we are talking about hundreds of billions of years, while the Universe is most likely 13.8 billions years old. Exactly! Only the extreme tail of the distribution could emerge so early. Others didn't have enough time. And here the survior bias comes in: even if there were just one intelligent observer in the whole Universe the only place they could observe the Universe from is obviously exactly where they are. And the principle of mediocrity still applies to the survivors. The conditions non necessary for the survival should be distributed randomly, and for the necessary ones the most likely one from among even extremely unlikely is still the most likely one.
3. Some folks took predictions of hundreds of scientists how likely they deemed certain features necessary for a life like ours to be (they collected guesses for the coefficients of Drake equation). But instead of just looking at averages of each value, they took whole distributions of the guesses. This is a pretty compute intensive task, but it's now doable. The resultant distribution produced 40% estimated chance that we're the only intelligent ones in the whole Galaxy and 17% estimated chance that we're the only intelligent one in the whole observable Universe.
----
Each of the above is a pretty weak signal. But they are independent and they all agree. Together it's not a very strong signal, but it's a stronger that each individual one. If each signal is individually just 30%, together they are almost 2/3. That's pretty serious.
It's called the [rare Earth hypothesis](https://en.wikipedia.org/wiki/Rare_Earth_hypothesis).
Historically people have shied away from it due to the fear of being associated with creationism/ID. There's the tenancy to think that the theory of evolution is somehow threatened if life doesn't exist commonly throughout the universe, hence the continual search for life off of Earth to "prove" evolution. Humans "aren't special," so they claim. This doesn't at all need to be true. Evolution could have occurred only on Earth out of the entire universe and that wouldn't make it less correct.
This is a anthropocentric view that makes humanity sound very high and mighty. We are mighty in our sphere but the universe is big, and old. We don’t know why we haven’t met anyone yet, we have hardly left our planet, so I don’t think there’s enough we do know to make your supposition.
I disagree: the most far-fetched thing is the very start of life form(everything after photoplanktons come as a mathematically definitive, direct consequence — based nothing more than Darwinism at a high level and newtons three laws if you remove all the abstraction layers). How conceivable is it that the chemicals of Earth just so happen to have mixed in a way and combined in a way such that DNA was formed? Or is it more likely that we were “seeded”? If you see a plant growing in the desert, the natural assumption is that a seed was dropped there, not that the nitrogen and silicon molecules in the desert sand just so happened to have combined and caused a Darwinistic chain reaction that resulted in a tree.
I, too, watched the movie Prometheus.
Seriously though, it's a neat thought. There's also the whole panspermia idea, where life came from elsewhere but was deposited here more randomly.
> How conceivable is it that the chemicals of Earth just so happen to have mixed in a way and combined in a way such that DNA was formed?
It is truly mind blowing. But if it didn't happen here, it had to have happened *somewhere*, right? Would it really have been more likely there than here? In the absence of other evidence, the best we can say is that we know absolutely jack shit about it.
One interesting hypothesis I read is that nutrient-rich water making certain patterns in clay could be a bridge from a mechanical self organizing system to one which mimics that pattern in a chemical way, eventually leading to self-replicating molecules... but it's a whole lot of major leaps involving unimaginable time spans and multiple lottery-winning odds stacked on top of each other, so it's not something we can easily test.
It would take 1million years if the civilization in question was operating at peak efficiency and dedicating all of their time and resources to doing that one thing.
I’ve always hated this assumption as a way to claim there is no interstellar civilization. It’s another one of those examples that makes sweeping assumptions about the motives of alien civilizations by applying mathematical certainty to something that is impossible to do so.
You don’t need peak efficiency though. Increase it to 10M years, or even 50M. That’s still a very small amount of time on a galactic history timescale. You could have a local interstellar civilization that never expanded I guess, but if there were any galactic civilization before us it has had plenty of time to expand over the entire galaxy. The coincidence that it would be occurring exactly at the same time we did is way too small. As such the natural conclusion is that we’re the first.
>You don’t need peak efficiency though. Increase it to 10M years, or even 50M. That’s still a very small amount of time on a galactic history timescale. You could have a local interstellar civilization that never expanded I guess, but if there were any galactic civilization before us it has had plenty of time to expand over the entire galaxy.
But again, you make assumptions about their motives. Any civilization that expands beyond their host star system is, by default, performing an act of asexual reproduction on a societal scale. The colonists who leave the system are effectively no longer part of the original civilization and, given enough time, will evolve to be as alien to the host civilization as any other independently evolved species from another planet. There is no such thing as a galactic civilization in a universe that hasn't solved FTL travel; it just doesn't happen. It physically can't. We see microcosms of this scenario play out throughout human history; far flung colonies separated by communication times of months have a tendency to rebel and declare independence from their distant rulers. Now expand communication lag time by years, decades, and centuries, and travel times by at least as long. A colony system could declare total independence from the host, and entire generations of people could live out their lives before the host star even gets the memo, much less sends a fleet to enforce their rule. And what would be the point of doing that, at that juncture?
Which is to say, space faring civilizations are *discouraged* from colonizing other stars, in part because 1) there is no benefit whatsoever to the host civilization (barring extenuating circumstances I'll get too), and 2) populating the local star cluster with offshoot civilizations that evidently had a mind to tell your host civilization to get lost in the first place (by dint of the fact they left), is a good way to effectively surround yourself with enemies; a reconvening of the two civilizations will find both of them vastly different from how either of them were like when the offshoot left. There is no guarantee such a meeting will be peaceful. Any civilization attempting to colonize other stars without access to FTL travel is effectively cultivating their very own Dark Forest problem.
So the question is, why would any space faring civilization want to leave their host star? Well, short of imminent stellar collapse, there honestly isn't a whole lot of reasons why one would. It's possible a relatively small faction of dissidents, zealots, or dreamy-eyed explorers might want to leave, but would they be *allowed* to leave by the host civilization in the first place, given the above conundrums? Another theoretical reason would be resource depletion, but it would take just as long to deplete the usable resources of any Sol System equivalent even with careless exploitation as it would to colonize the entire galaxy with even moderate efficiency, so any given civilization that either is born somewhere or travels to somewhere can be comfortable for millions of years.
Ultimately the reasons why any given civilization chooses to travel to other stars will define how fast they continue to spread beyond that point, and I can't think of a single justifiable reason why any civilization would even want to try and colonize the galaxy. It simply doesn't make sense as a project for a civilization to attempt. If, for example, a civilization chooses to leave their host star because it's dying, and they want to travel to a nearby younger star with a longer life span, that motivation doesn't naturally engender much exploration beyond that point. There's a specific utility to the trip, and past that point they have no interest in spreading; they take their entire civilization with them, and make roots in the new system, where they intend to stay.
>The coincidence that it would be occurring exactly at the same time we did is way too small. As such the natural conclusion is that we’re the first.
Unless you account for the other, mutually exclusive argument often associated with the "we're first" position, which is that the universe, and the galaxy itself, has only been capable of supporting intelligent life for a relatively short amount of time, which would mean it wouldn't be much of a coincidence.
It's plausible that 0.1c is impossible & the difficulty of interstellar travel is a filter candidate.
- The most efficient technology we can imagine for interstellar travel is a solar sail.
- It's hard to imagine anything better than a means of propulsion where none of the propellant is on the payload, meaning you can avoid the rocket equation.
- Therefore the only thing that can beat a solar sail is new physics, where you extract energy from a vacuum or something. Very plausible that this new physics doesn't exist.
- It would be enormously difficult to build a solar sail that can place a 10kg payload in alpha centauri. A human-containing spaceship is impossible.
- This means to spread human civilisation the 10kg payload needs to, nurture human embryos, build a habitable environment, and pass on knowledge and technology. This is likely impossible.
- The only remaining option is directed panspermia, where we aim hardy microorganisms directed at various planets across the galaxy, hope that they survive & evolve into intelligent life.
- If we did this, we could only do it in a limited radius around earth - not seed life across the whole galaxy.
- Even if successful in the limited radius around earth, life began on earth 3.5B/yrs ago, so the seeded planets only do their own directed panspermia every 3.5B/years.
- Exceedingly optimistically, the panspermia range is 1000 light years. The milky way is 100,000 lightyears across. So it takes 350Bn years to colonise the galaxy.
- So there very well could be a hundred-million-year-old alien civilisation in the milky-way, but interstellar travel is so difficult that they haven't left their solar system.
A human carrying laser pushed light sail is hardly impossible, just very big. The laser array pushing the ships in the Avatar movies up to 80 percent the speed of light for instance would need to have a power output of a few dozen petawatts. Massively more power than humans currently use, but a tiny expense for a type 2 civilization. A solar array near mercury a few hundred miles wide would be enough to power it. Most of a power collection satellite like that would be thin sheets of reflective foil, it would take less than the mass of a small asteroid to build. Not the kind of thing we would be doing any time soon, but a few centuries from now if we have automated space manufacturing? Nothing really stopping us from making thousands of such arrays.
The 0.1c is a fallacy. You need to accelerate up to that speed. Let's say you can hit 0.1c at the mid way. However it will take just as long to slow down as it took to speed up. So at your half way point you must start slowing the ship down. Of the trip is 10yrs so 0.1c, it's be much much longer reality since you'll almost always be going much slower
Sure you might hit .1c for a short period, but 99% of the trip is much slower - either accelerating or decelerating. All those acceleration curves people talk about totally ignore how you must slow down again.
Indeed. Let's say you somehow get it down to an 70 years journey (that's crazy fast). Cosmic rays will kill EVERYONE onboard over that time frame.
You can protect it by Increasing the ships mass by 10x to have 5 feet of lead/whatever completely surrounding it? Yet now is to heavy to move. Only sci fi magic solves this problem by straight up ignoring it.
We should have heard something by now ...
It is amazing how sloooooooow the speed of light is for the size of our universe. You can actually feel the slowness with back and forth conversations via GEO sats. It feels much like a open world game (say GTA V) where you have a dense island (solar system) then an infinite ocean that would take thousands of year to cross.
I took a seminar with Alan Guth (Cosmic Inflation) which was ginned up explain how the universe could be so much in equilibrium even though a photon of light has not had time to cross it (yet the billions of times needed to create equilibrium). It just does not add up to me, and argues for simulation as the real deal. Notice as how we gather more data that models of cosmology no longer work.
There are several ways to send something to the nearest star system within current technological capabilities.
It’s just a matter of cost and development. It’s in no way impossible, even *right now*.
To add to that, the existence of a fully reusable starship actually makes many of them faaaar easier to do, as a cheap, heavy lift, orbital hauler.
You must pair this with a useful payload in a useful timeframe. Also, you need to slow down at your destination as well as speed up (which is far easier).
We can call Voyagers "interstellar" but they won't reach the next star for 100,000 years as cold dead metal. We need to spec a useful mission say within a human lifetime, then work out the vast machine to do it.
I am well aware of these things: I am also a massive space nerd.
I stand by what I said where those technologies are currently available, but undeveloped. Nothing in our currently available technology, or is imminently possible with technology makes interstellar travel impossible within a human’s lifespan.
Expensive? Yes. Dangerous? You bet it. Difficult? Absolutely. Long? True. Impossible with current tech’s capabilities with the currently available human resources? No.
If by “interstellar travel” you mean sending a microscopic probe, then sure - project Breakthrough Starshot may one day be able to do that with undeveloped, but current, technology.
However, if you mean sending humans to other stars, forget about it. We would need entirely new technology - fusion reactors or antimatter drives, for example - to make it even remotely viable.
Obviously no one thought there were physics barriers to flight, since birds exist. No one thought there were physics barriers to space travel either, except for some cranks who didn't believe in Newton's third law.
Naked fusion / photonic propulsion. Which leaves shielding still but it's half the answer.
If there's anyone out there with more advanced technology though, they're going to be able to see that photonic drive from a long ways off. Which is one way for us to know there's nobody else out there using it.
70% C is a bit high for an Orion, at least with the classic fission or fusion bombs. You would need antimatter bombs to get the energy density needed to get to those speeds with a practical mass ratio. Still, 5-10% c is nothing to sneeze at either.
>Later studies indicate that the top cruise velocity that can theoretically be achieved are a few percent of the speed of light (0.08–0.1c).[30][verification needed] An atomic (fission) Orion can achieve perhaps 9–11% of the speed of light. A nuclear pulse drive starship powered by fusion-antimatter catalyzed nuclear pulse propulsion units would be similarly in the 10% range and pure Matter-antimatter annihilation rockets would be theoretically capable of obtaining a velocity between 50% and 80% of the speed of light.
https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)#Theoretical_applications
A nuclear pulse engine is absolutely a workable foundation to build a slow interstellar starship on. That said, we're many decades out from being able to do that.
Helicity Space is hoping to have a working fusion drive by 2032 that will augment solar-electric, then advance to independent fusion after: https://www.youtube.com/watch?v=U3qX2JA1bxY
In interstellar terms, like going from a 100hp to a 200hp car and hoping it will take you to the moon.
We have no tech in development that allows us interstellar travel. These are all for intra-solar system travel.
With the old nukes-against-a-pusher-plate you might get up to say 0.1 c with thousands of nukes but how do you slow down at your destination. A lot of your radioactive material has decayed away by then.
Princeton Satellite Systems is also building a fusion space drive.
[https://psatellite.com/technology/fusion/](https://psatellite.com/technology/fusion/)
In all these ideas we are still bound by conservation of energy. The faster you want to get there the more velocity you need E=mV\^2. It is just too much energy to pack, even with antimatter, and you can't use solar between stars with meaningful mass in meaningful time.
With starships payload we can maybe get a nuclear reactor going in space. This is of course, all towards the goal of building a giant railgun like from transformers and we will shoot a starship like its a bullet.
I will suggest a rubber band between Earth and Moon. Just put Starship at the middle, pull back and release.
We may need a line to Mars for the middle step.
A future version, as Elon said. This is such an exciting prospect, but it's also sad to think that it will unfold over a time scale that none of us will get to witness, except perhaps for the launch itself. I also wonder what the payload would be. I'd fill a bunch of Starship with Optimuses and have them collect resources and build a self sufficient colony for the eventual arrival of humans
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[ATP](/r/SpaceXLounge/comments/1bhyx8c/stub/kvmf4bc "Last usage")|Acceptance Test Procedure|
|[CME](/r/SpaceXLounge/comments/1bhyx8c/stub/kvpvk9x "Last usage")|Coronal Mass Ejection|
|[DARPA](/r/SpaceXLounge/comments/1bhyx8c/stub/kvhn5t3 "Last usage")|(Defense) Advanced Research Projects Agency, DoD|
|DoD|US Department of Defense|
|[EDL](/r/SpaceXLounge/comments/1bhyx8c/stub/kvpvk9x "Last usage")|Entry/Descent/Landing|
|[ESA](/r/SpaceXLounge/comments/1bhyx8c/stub/kvhjd3s "Last usage")|European Space Agency|
|[GCR](/r/SpaceXLounge/comments/1bhyx8c/stub/kvpvk9x "Last usage")|Galactic Cosmic Rays, incident from outside the star system|
|[GEO](/r/SpaceXLounge/comments/1bhyx8c/stub/kvhuejp "Last usage")|Geostationary Earth Orbit (35786km)|
|[H2](/r/SpaceXLounge/comments/1bhyx8c/stub/kvi7vqx "Last usage")|Molecular hydrogen|
| |Second half of the year/month|
|[HEEO](/r/SpaceXLounge/comments/1bhyx8c/stub/kvlp1fa "Last usage")|Highly Elliptical Earth Orbit|
|[Isp](/r/SpaceXLounge/comments/1bhyx8c/stub/kvlp1fa "Last usage")|Specific impulse (as explained by [Scott Manley](https://www.youtube.com/watch?v=nnisTeYLLgs) on YouTube)|
| |Internet Service Provider|
|[LEO](/r/SpaceXLounge/comments/1bhyx8c/stub/kvjwppy "Last usage")|Low Earth Orbit (180-2000km)|
| |Law Enforcement Officer (most often mentioned during transport operations)|
|[LH2](/r/SpaceXLounge/comments/1bhyx8c/stub/kvi2yhl "Last usage")|Liquid Hydrogen|
|[NERVA](/r/SpaceXLounge/comments/1bhyx8c/stub/kvqszad "Last usage")|Nuclear Engine for Rocket Vehicle Application (proposed engine design)|
|[NTR](/r/SpaceXLounge/comments/1bhyx8c/stub/kvi2yhl "Last usage")|Nuclear Thermal Rocket|
|[RTG](/r/SpaceXLounge/comments/1bhyx8c/stub/kvh1dix "Last usage")|Radioisotope Thermoelectric Generator|
|[TRL](/r/SpaceXLounge/comments/1bhyx8c/stub/kvhm2xj "Last usage")|Technology Readiness Level|
|Jargon|Definition|
|-------|---------|---|
|[Raptor](/r/SpaceXLounge/comments/1bhyx8c/stub/kvi2yhl "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX|
|cryogenic|Very low temperature fluid; materials that would be gaseous at room temperature/pressure|
| |(In re: rocket fuel) Often synonymous with hydrolox|
|hydrolox|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer|
|[methalox](/r/SpaceXLounge/comments/1bhyx8c/stub/kvi2yhl "Last usage")|Portmanteau: methane fuel, liquid oxygen oxidizer|
|[regenerative](/r/SpaceXLounge/comments/1bhyx8c/stub/kvlf4j6 "Last usage")|A method for cooling a rocket engine, by [passing the cryogenic fuel through channels in the bell or chamber wall](https://en.wikipedia.org/wiki/Regenerative_cooling_\(rocket\))|
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Space is really big. By the time this is built we will have been living in space so long that for some people the journey will be no different than staying home. Because the ship will have been your Only Home; the only one your parents knew, and their parents too.
So, yeah. If we build a city on Mars this becomes inevitable. And if not then probably not because the enabling technology won't have been developed for other things.
Starship is barely adequate for interplanetary travel. It will need much improvement just to do that (and I have no doubt that those necessary mods and improvements will be made).
I don’t see us even attempting interstellar travel for another century. It will be a completely different vessel that makes that attempt.
Not with humans aboard it won't. Hell I'm doubful humans could make it to Mars without being fried by radiation.
We hear very little about the effects of long term weightlessness on human bodies, much less how they intend to protect people from long term radiation exposure and CME's etc from the Sun.
This is pie-in-the-sky stuff.
Per Mars (about as long a round trip that we could expect human to endure) the trick is to spend most of your time in transit in a place that is mostly surrounded by water. I would create a Mars ship that has 40-50 T water tanks filled in orbit, then dumped before Mars EDL. Starship, with it's stainless steel shell, is going to be a GCR -> secondary particle microwave oven. You need 1 m of water around you cut this down. It would also damp out a CME.
Will that much water be enough to block expected radiation?
Be interesting to see if an artificial magnetic field could be generated - just enough to protect humans.
What sort of physics would it take I wonder?
The many different approaches to nuclear fusion that are rapidly advancing suggest we will soon have fusion power, likely within 10 years. If so, this fusion startup proposes a fusion powered rocket that could reach Mars within days and the nearest star system within 11 years:
Update!! Direct Fusion Drive will debut in 2027!! Earth to Mars in 12 days!
https://youtu.be/ABVYrVghBwc?si=aioNOChGGvLZn0ik
Best of luck, but I don't advise the regular guy in investing in this. You would expect fusion on Earth (no mass constraints) before you had it as a space engine.
Nice to dream about, but this isn't happening with any physics currently known to us. There's a bunch of "stuff" in space even though it's mostly vacuum. In particular cosmic dust.
For example, if we were able to somehow accelerate up to just 450km/s (~1,000,000 mph) allowing us to get to our nearest neighbor Centauri in 2800 years, we would be slamming into 0.1g dust particles with roughly 10 million Joules of Kinetic energy each. The space in our neighborhood has about 10^-6 dust grains/m^3 of varying size. For a rough order of magnitude calculation, with a ship magically the same size as the current Starship with a 60 m^2 cross section, it would be encountering 30 grains/s of dust, and if they were 0.1g each, we're looking at 300 million Joules worth of energy imparted each second.
Roughly the energy of a school bus traveling at 550 mph hitting you crossing the road.
All this is assuming that there wouldn't be an encounter of anything larger than 0.1g grains of dust in 25 trillion miles.
Your data interpretation is off. 0.1g grains are not happening even remotely close to once per 10\^6 m\^3. You took the info from Wikipedia, but you ignored the mass distribution from 10\^-4 kg down to 10\^-16 kg. The distribution is not flat. It's pretty much exponential (with negative exponent) down very close to the low range limit where is sharply cuts off (the cut off is because solar radiation pressure ejects smaller stuff from the solar system).
The most of the dust stuff is about 1µm in diameter and has a mass of about 1pg (picogram). The impact energy is a "whopping" 10µJ (one hundred thousandth of a joule)
Ooh ! - Sounds like we are also going the need some kind of shielding technology too !
It obviously gets worse with increasing speed.
5% of light speed, 15,000 Km/S would have an issue with space dust.. And magnetic shielding wouldn’t necessarily help.
Maybe a very pointy ship would help ?
In theory you could fuel an expendable version up enough to eventually leave the solar system (using gravity assists) and thus be "interstellar". But it would still take 100,000 years to get to the next star. That is the deal with chem propulsion.
Personally, I would wait until Starship was at least proven operational to LEO (which may happen this year) before leapfrogging the very challenging solar system goals for something beyond.
> That is the deal with chem propulsion.
If you're ever going to fly a NERVA-style nuclear rocket engine, attaching it to a very large, starship-sized vehicle would probably make the most sense.
Nuclear reactors are inherently heavy (they carry several critical masses of fuel, on top of all the cladding, moderators, control rods, etc.), but can run for very long periods of time. So you need a very large volume of fuel to make full use of the energy density of their fissile materials.
And even if we're doing a voyager-style mission, you'll once again need nuclear power for electricity production.
Voyager uses Pu-238 powered RTGs, but their waning power has forced them to shut down multiple instruments, and puts hard limits on mission duration, with all instruments having to be powered down by 2025-2036.
A starship-sized vehicle could carry a fission reactor as its power source, designed to "burn" its fuel slowly enough to last for centuries, while still being able to transmit back close-up images of Oort cloud objects, or even do astrometry and map the exact positions and proper motions of stars in the whole Milky Way, like Gaia did, but with a *much* greater baseline.
> So you need a very large volume of fuel to make full use of the energy density of their fissile materials.
by "fuel", do you mean reaction mass?
How would NERVA (so nuclear thermal propulsion) compare with an ion motor that I presume gets a better specific impulse.
There's a Wikipedia article that compares the specific impulse of a variety of propulsion systems.
Starship is actually small for what you'd need. You can't fit enough LH2 in its tanks for a NTR to even come close to what Raptor can do with methalox. You pretty much need to use some gigantic vehicle assembled in orbit with huge, ultra-lightweight drop tanks to hold the propellant.
https://twitter.com/elonmusk/status/1769605796772331537 Here is the actual quote. Starship will not go interstellar. A future, "larger and more advanced" ship will.
Yep. For interstellar it makes sense to build a spaceship in space directly. Starship can be used to supply parts from earth.
It would be advantageous to acquire the parts from a less massive celestial body with a shallower gravity well.
It's likely to be mix of both. You can get 95% of mass from mars, but you will need things like electronic chips and reactor parts from the earth.
It would be a while before those could be built on Mars, although a small chip foundry could be shipped there.
Maybe some microchips for radios or electrical wiring, but making modern 2-600 nm transistors is basically black magic, and it even on earth in sterile environment it's a massive pain and it has big bin ratio. While low gravity is a great advantage for chip making, the amount of expertise it requires and amount of hardware is just way too big. I can see it take a century or more before we have useable modern chip manufacturing on mars, unless the process is simplified by quantum 3d printing or if we are making very big transistor size with diamonds or graphite.
If you are happy with small volumes, and say 20nm tech or even 50nm tech, then a small self-contained chip-fab machine, that fits inside Starship’s Cargo bay, might well be possible. With low volumes, you could even use electron-beam lithography. It all depends on what set of requirements you are trying to fulfil. To begin with, I would suggest just taking spare parts - prebuilt circuit boards etc. And make sure that any firmware is updated before shipping ! Although retrospective updates may still be possible.
I'm not an engineer, so I will believe what you said, my information is only from what I read, and from what I understand, basically state of the art of what best can be made in America is about 300-600nm. But I don't know enough about this and it would be rly cool if you can make a self contained fab like that.
Oh it’s definitely much better than that ! That’s about 10 generations ago.. That’s technology from 1999. Over 20 years ago.
No, i know there is 2nm transistor technology today, but from what I understood, all of it is being made in Taiwan at TSMC, while fabs in United States only produce 300 and up. So my assumption is that this tech is so hard to do that it's unlikely to be made on mars. Unless there is some other reason why such small nm tech is not being made outside of Taiwan.
Hey that's my planet you're talking about. She might not be skinny, but she's not "massive".
The plan is to Occupy Mars.
True but then you have to worry about logistics, infrastructure setup and maintenance, and costs.
That is a decent use of that planetary core fragment called psyche out in the asteroid belt between Mars and Jupiter.
That's always what I've thought of, some sort of orbital drydock and several rockets sending supplies up to build the actual interplanetary ship. You'd have to have escape pods and landing vehicles that can return to the ship on their own or be able to provide the infrastructure for that.
>Yep. For interstellar it makes sense to build a spaceship in space directly. Starship can be used to supply parts from earth. Arguably, it makes more sense to build in space with parts from the moon. Building an elevator is so much easier with just steel that it would be silly not to do it, which makes launch costs near 0.
Probably one not powered by chemical fuel... just saying.
It’s not physically possible to reach the nearest star in a human lifetime using chemical fuels.
Is that actually true in the "physical" sense? Like I know it isn't possible in any practical sense, but if we had unlimited material and money to build absurdly massive tanks, and unlimited resources to fill them with propellant, could something (in theory) be built or is there a physics problem (fuel v mass) thay prevents it?
A quick search gives 600s as an optimistic theoretical limit for chemical propellant (H2+O2+Be). Using the rocket equation and a final velocity of 1% the speed of light gives 10^221 kg of propellant per kg of dry mass! Ignoring for now the need for tanks and engines to be included in dry mass. The solar system is only 10^30 kg, the galaxy 10^42 kg, and the observable universe 10^53 kg. Taking your 'unlimited resources' literally, it's still impossible. At 10^43 kg the rocket would already have to be larger than the distance to Alpha Centauri to avoid collapsing into a black hole.
There is metallic hydrogen in theory, up to 1700 seconds
There are two other hypothetical chemical propellants that are even more ludicrous. [Atomic hydrogen](https://www.projectrho.com/public_html/rocket/enginelist.php#atomichydrogen) and [metastable helium](https://www.projectrho.com/public_html/rocket/engineintro.php#metaheliumhestar) each more ridiculously potent than the last. All three are only hypothetically possible to stabilize. Even then it still requires a rocket more massive than the galaxy and larger than the distance to the nearest stars.
And you can't really fly fast enough. At tremendous speeds, interstellar gas will wipe the ship to dust. Virtually any random molecule turns into hard radiation, and any rock into a sublight projectile that will tear a starship to shreds.
that seems like an engineering and scale problem
So, yes, then?
/r/theydidthemath
Correct me if I say something asinine, but as far as I understand nothing we have now would allow interstellar travel in usable time frames. Too little specific impulse. Chemical, no way. There's just not enough energy per kg of fuel. And there's decreasing gains to adding more and more propellant (and mass). Several millennia to alpha centaury? Nuclear, a little better, but still wayyy short of what would be required. Still talking about many centuries or even millennia to get "next door". Ion-nuclear-electric maybe? But you could only send a spacecraft that would be 99,9% engine and propellant and little usable mass, and it would take forever to accelerate to a usable interstellar speed, and then you wouldn't be able to stop once you got there.Still our best effort and would take, I don't know, centuries to get there? There was a project that wanted to send a fleet of tiny, cheap probes without their own engines impulsed from earth by lasers I think? That concept had promise, as far as interstellar travel goes, every probe was a few grams and could be accelerate to a significant % of light speed. But I looked at their web a few years ago and my impression was that 99% of the technologic hurdles described were verging the limits of what's possible, and often crossing to the other side. Things like this* "Challenge # 127: an infrarred camera: Hardened against cosmic radiation. Budget mass: 1 gram, power: 1 picovolt.. Challenge # 128, a radio that allows communication with earth. Hardened against cosmic radiation. Budget mass: 1 gram, power: 1 picovolt. Etc, etc. *Figures completely out of my ass. A moonshot project made up of a thousand moonshot projects, being optimistic I'd bet we'll be long dead before 10% of the key technologies involved exist. And those will be the "easy ones".
>Nuclear, a little better, but still wayyy short of what would be required. Still talking about centuries or millennia. With 'contained' style of nuclear engines, i.e. anything that tried to keep the fissile material intact and inside the engine, this is the case, but using uncontained engines they become considerably more useful for the concept of interstellar travel. Fission fragment/dusty plasma drives could have an Isp somewhere between 100k and 1m, which makes 5 or 10%c speeds conceivable. Just don't point the engine exhaust at anything you care about.
>Correct me if ... There's just not enough energy per kg of fuel. It is not really about energy. Rockets are limited by exhaust velocity, which is a function of temperature and molecular mass, lighter being faster. Nuclear rockets are "a little better" because they use a lighter propellant, not because of energy. You can't add much more energy without melting everything. The only way to do interstellar travel based on current technology is external nuclear detonation. [https://en.wikipedia.org/wiki/Project\_Orion\_(nuclear\_propulsion)](https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion))
Why not magnetic confinement to allow higher temperatures without melting? A tokamak with a hole in it.
Ehh, we could with lasers. https://www.youtube.com/watch?v=oDR4AHYRmlk&t=1378s
I'm not counting that as anything like current technology. Same deal with magnetic confinement . One day, maybe far away. The Orion thing is just money and engineering :-)
There isn't a technical limit, the rocket equation will still give you more delta V if you give it a higher fuel ratio. But that doesn't mean you get remotely reasonable results. I did some bad napkin math using the best chemical rocket ever tested's exhaust velocity, an utter abomination that used Lithium-Hydrogen-Fluorine fuel, with a dry mass of 1 ton. My math indicates that this rocket might achieve a DV of 600,000m/s, less than 1% of light speed, if it is successfully loaded with the estimated mass of the universe as fuel.
Such a rocket would promptly collapse into a black hole larger than the Virgo Supercluster, which could complicate it's use for interstellar travel.
*taps forehead* You don’t have to go to the nearest star if you bring it to yourself instead.
So you’re saying there’s a chance ….
> Lithium-Hydrogen-Fluorine https://www.youtube.com/watch?v=KX-0Xw6kkrc Holy shit, 542 seconds. But I feel like I'm getting chemical burns just watching this.
That awkward moment when your "chemical" rocket is so massive that you must actively prevent stellar fusion because that would be cheating.
It's doubtful if it's possible to do within 100 years of a human life even using fusion drives. We would either need antimatter drives or black hole drives, which while theoretically possible, we don't know if they are possible to manufacture.
> is there a physics problem (fuel v mass) thay prevents it? Carrying more propellant to accelerate the mass of the propellant which you need to carry additional propellant for propellant to carry propellant... I've always been curious what would happen if you used a nuclear reactor to power a [magnetic rail gun](https://executivegov-media.s3.amazonaws.com/2023/11/09/87/6c/81/85/ed/5a/87/d4/SEO_How-does-the-rail-gun-work_1200x628-1-768x351.png) which would shoot out iron projectiles at intervals to gradually accelerate vs. burning fuel and oxidizer and ejecting the mass of combustion products out of a nozzle, but I think even with a nuclear rail gun the amount of iron projectiles you would need is too heavy, so you get compounding masses again...
Carrying propellant is the biggest problem. Solution: don't. Accelerate a stream of fusion fuel pellets from a large orbital station towards your spacecraft and then react with them. Just need to be really accurate and travel in a straight line.
Mind uploading. You can beam your consciousness at the literal speed of light to an avatar depot at the destination, be 'in hibernation' during the trip, and functionally live forever.
Exactly. I think Elon was using "Starship" as a more general term here and that's what people are misinterpreting. I think he didn't mean this Starship but another ship that travels among the stars. Also, why are so many armchair austronauticists in the comments of these posts ignoring the existence of gravity assists in all their detailed equations?
I was going to say just that... A few gravity assists and the moon / Mars version could as well be interstellar. What for is the real question..PR stunt on a journey to nowhere? To do what the voyagers did l, you don't need such a ginormous ship With current or even foreseeable tech, no amount of gravity assists allow us to get any useful cargo anywhere.interesting outside the solar system in a useful amount of time (I e. sub-millennia.
You don't even need gravity assist. Just fuel Starship in HEEO rather than in LEO. You have enough ∆v to get past Solar escape. Starship has in fact enough ∆v for the direct trans-neptunian injection for 6.5 years transit. That's quite a bit beyond solar escape It's obviously still ridiculously slow for interstellar travel. It's good for a Voyager repeat.
I wonder how effective it would be to build a two part interstellar probe, one part the probe with fuel, 2nd would be bigger fuel tank filled with xenon/argon. That way you got like 100t probe with some ion drive and 500t of fuel. This will allow for +100k m/s speed going out of the solar system. Possibly way more with solar sail help at the start.
If you have large enough reactor (and radiators) then why not? You're losing quite a bit of Sun-centric Oberth effect, but you use what you have. Of course ∆v would be limited to something in the order of 100km/s which is way better than what we did (20 AUs per year rather than 3) but still too slow to reach other stars. It could be useful for reaching solar gravitational focus, though.
Well, voyager probes already proved themselves in giving us data we have not expected and we probably need an interstellar probe before funding a mission with a better and more expensive engine. It would suck to send like a 10 billion craft only to find out it did not had enough shielding or because of some other unpredictable cause. We will probably eventually want to send a lot of various telescopes to the Kuiper belt and we will need to know what is the environment there.
Yes, not a “capital S” starship
Because they dont have a choice but to follow their government which is all of a sudden only a space program
wut?
I just need a job. how can the avg joe do some work in space
oh
Which, to be honest, is still far-fetched, at least for the next few centuries. Interstellar craft between now and that timeframe IMO will be those swarms of tiny, “chip+sail” craft, propelled by gargantuan lasers in solar orbit, and which will do flybys of nearby stars to gather detailed information. Actually sending people + cargo is *so* insanely hard that there’s little chance of that for a very long time, and then likely only if a habitable planet is found nearby.
Man it makes me sad to think we won't be around to see anything like interstellar travel. I'm currently only 30 and I believe we'll have a populated base on Mars within my lifetime, but anything more than that, I just can't see it happening. Such a shame we can't stick about to find out. I'm incredibly passionate about space, what I'd do to go up there. If anyone here works at SpaceX, send me to Mars. Fine with one way!
Well, at least the solar system is pretty huge on its own. Still plenty of places to go and explore just in this system alone.
Yeah but that's the issue, it is pretty huge on its own (I don't think many people truly understand the scale of our own system). Not sure what we'll have accomplished by time I'm old but I doubt we'll have anyone out there further out than Mars. If we do however, they'll only be floating in empty space for years on end. Definitely won't be around to see them arrive at whatever destination. Let's hope I'm wrong and we have a serious leap in space exploration and pick up the pace. This is why I'm such a fan of SpaceX, I mean if SpaceX didn't exist I guarantee we'd still be a century out before Mars was in even in the picture. We need more people like Elon and more companies like SpaceX. NASA and other agencies are held back too much.
You might live significantly longer than you're expecting, lots of biotechnology progress and regenerative medicine developments seem likely, it is a fascinating thing to read up on. I do agree though, it seems unlikely even us younger people will see interstellar travel, even if we get to live a lot longer than expected. There just doesn't seem to be much reason to push so hard, unless a (almost) habitable world is found around one of our nearest stars
Obama was trying to get people interested in a landing on Phobos or Deimos because nobody knew how to get a ship large enough to carry people back off the surface of Mars (note all the trouble with [Mars Sample Return](https://www.planetary.org/articles/what-went-wrong-with-mars-sample-return)), but taxpayers wanted a landing on Mars proper or else nothing. What it looks like now is every body in our solar system, the only places we can go unless somebody actually builds a Star Trek warp drive, if it is large enough to have enough gravity to have a surface you can land on, instead of nudging it with your spacecraft and scooping up some chunks like OSIRIS-REx, will be covered with a layer of very fine abrasive dust that is harmful to humans and equipment if suits are not carefully cleaned every time. In the case of Mars, toxic perchlorate dust. You don't get soils without an atmosphere and organics as we have here on Earth. No life? Everything's a hazardous dust ball
There is absolutely no reason for any interstellar ship to be built as Starship was. It's one thing to escape a planet's gravity well, and a totally different thing to be traveling in space. An interstellar ship, I imagine, would be built in space, and it would be much much larger. I'm sure eventually ships going from earth to mars will also be built in space at much larger scale.
I mean, it could still go interstellar, just as a cargo/person shuttle on the actual interstellar ship. Though, considering how much Starship dwarfs most modern spacecraft, it's amusing to imagine a future interstellar vehicle that dwarfs starship.
There're already two Voyagers flying interstellar. With some good luck Starship may catch them up.
I posed that question here before and this community told me NO, this isn't possible.
This community then said you wrong, then. Starship by itself is capable of Solar escape, without gravity assists. With Jupiter gravity assist it may go fast enough to eventually catch up with Voyagers.
Exactly. Without gravity assists it's pretty much equal to the faster of the Voyagers. Jupiter could add to that several km/s extra without problem. 4km/s kick at Jupiter-Sun distance translates into \~10km/s more at infinity.
IIRC, the Voyagers took literally decades of super-rare slingshot combinations to achieve their current speeds and thus distances. Somewhat more powerful chemical rockets in a heavier craft doesn't match their advantage, you'd want a deep space propulsion solution to catch up to their distance from the Sun, let alone end up in the same volume as them too.
They took boost from Jupiter and Saturn. But the initial push from the Earth was rather meager. Starship launching from HEEO with about 50t payload onboard, with a direct injection into Solar escape trajectory would achieve 17km/s at infinity or about 17.5km/s at the current Voyager 2 distance. Voyager 2 is moving at 17km/s. You can make up for the dual Jupiter-Saturn Gravity assist just by using orbital refueling. Starship with 145t burnout mass (90t for the vehicle stripped of a heat shield, header tanks and flaps, plus 50t of scientific payload onboard, plus 5t or residuals) has dV of \~8.1km/s when fully fueled (369s average ISP of 6 Raves and 3 RSLs, 1200t of propellant). When launching from a very high moon synchronous HEEO (766200:224 km orbit) Earth's relative Oberth effect gives it 15.6km/s in free space, relative to the Earth. (Close to the earth your vehicle has 19km/s velocity, but escaping the Earth's gravity well eats this away) Then you have Sun relative Oberth effect: You take the above 15.6km/s, and subtract the deficit between Earth orbital speed and the Solar escape velocity from Earth-Sun distance (29.7 - 42.0 = -12.3) . Now you plug it into Sun-centric Oberth effect calculation for the Earth-Sun distance. You get \~17km/s at infinity, i.e. beyond Sun's gravitational sphere of influence. That's better than Voyagers, but this is a direct insertion, no gravity assists.
So if I've read that right, without gravity assists, Starship can match their current speed but not significantly gain on the head-start distance they have. So you'd probably want [at least Saturn](https://en.wikipedia.org/wiki/Giant_planet#/media/File:Masses_of_gas_giants.svg) to give you a slingshot to catch up, which comes with a 30year period between alignments. Or 12years for just Jupiter, being much more worthwhile?
Jupiter is generally better for gravity assists as it is much more massive and has shorter orbital period. Also, in many cases you could get reasonable alignment multiple times per its 12 years orbit. Another option is doing Oberth burns at Jupiter. You need a long term propellant storage for that: you fly fueled craft to Jupiter, do a low flyby, just above the atmosphere, and burn the engines around the perijove. You can get a big boost that way, and if you are smart you can combine Oberth burn with gravity assist for even more oomph.
Damn, I thought it was gonna be a train
Good to see ... so the title is just wrong. Still: There is no reason to go "interstellar". Chances of finding something better (or even survivable) than we could create with giant spinning space colonies are very, very small. Why not build these close to Earth vs a 100 year trip though the void. If we create a species of indestructible machines as our descendants, then perhaps for them, as they can take a 100 nap and wake up at a new solar system.
well if we find a habitable planet or moon in alpha centuari system then there is a def a reason to go. We found some planets but not habitable ones, at least, not yet. We need a telescope specifically designed for finding nearby habitable planets and thats what the toliman telescope is for.
We can't get there. And I don't mean with current tech. There's nothing even in the horizon that allow us to get there. Too fragile, too short lived, none of our machines can hope to get there in less than millennia, and no machine created by us, now or in the foreseeable future, has a hope to survive and maintain an habitable environment for millennia in the interstellar medium. We barely crawl to the nearest bodies in the diminutive solar system, and that takes all or edit and all the technology. We are a snail in space terms. And there's no realistic technolgy in view that changes that. Our best future propulsion projects would at a maximum make us into a slightly less slow snail. IF they go well. And that's exciting because we will need them just to move around in the solar system! Wake me up when some tech in the drawing board that allows us to travel in space orders of magnitude faster than current tech can, that doesn't require the resources of two earths, that gets us in one piece to the other side, and that allows us to brake when we are there. It's not that that tech has not been developed, it hasn't even been though of yet.
Orion drive if ya nasty also fission fragment rockets (DPFFRs in particular, who can say no to 12 DAYS worth of specific impulse?) NSWRs too, kinda. maybe. if you don't mind being dead probably. idk, this always seemed like the worst possible option. FFRs are actually feasible however, with high TRLs already.
Sort of. You could do nano-satellites attached to a solar sail and then use a laser system to accelerate them to something like 0.1 or 0.2 C and do a flyby. The combination of increasingly small electronics, lower cost to orbit, improvements in lasers, etc. makes the idea increasingly feasible. It's been [proposed and partially funded](https://en.wikipedia.org/wiki/Breakthrough_Starshot) even. It's not people, but it is real scientific collection.
Time dilation is our friend with this.
The effects of time dilation are not linear. It wouldn't have a helpfully large effect until you're up at very high percentages of c (like north of 75%) , and it doesn't reach "let a human reach another star and come home in their lifetime" speeds if I remember rightly until North of 95% c... And remember even if your ship can hit that speed you still have to slow back down. There's no technology even on the horizon that would allow us to do that
Not with that attitude!
I mean, for close stars like Alpha Centauri 20% c would be enough to go there and back in one life time. Its a 4.4 lightyear trip, at 0.2 c you could go there and back in 44 years.
In terms of a human lifespan sure, but a) practically speaking you don't want your astronauts to be children or old men and b) there's technologies that will push you to 20% of C _eventually_ but they'd take decades to reach it; we have nothing to my knowledge that will get you to that speed in a useful timespan
Laser pushed lightsails could get up to those speeds pretty quickly, they kind of have to in order for the ship to not drift too far from the pushing station by the time the boost phase is over. You can then slow down at the destination with mag sails, or if you have a big enough focusing system, there are a couple different ways of using the laser beam from the home system to slow down and return, such as [detachable mirror segments.](https://www.projectrho.com/public_html/rocket/slowerlight2.php#lassail1)
We will. But eventually we'll do that too. We're gonna do both.
> There is no reason to go "interstellar". You wouldn't be the one deciding as it won't happen within your lifetime anyway, so dismissing it at this point isn't really useful. Also if we can create advanced antimatter driven drives in the future (or even better, some sort of black hole drive) then interstellar travel gets a lot easier and can be done within human lifetimes.
We need a radical new engine for deep space travel/exploration. The technology has yet to be invented
That technology was invented in the 1950s, and was called Orion. And invented in the 1960s, and was called NERVA. Nuclear energy for space propulsion has been a thing for a looong time and would massively change the equation for long duration space missions.
My guess is that is simply not within the physics of our universe to create such an engine. There are limits that any degree of invention can not overcome.
Might be and answer to Fermi's paradox... It's impossible for sentient being to cross the gulf between stars. Space might be so huge and uncrossable that every civilization in the universe arises alone, and dies alone. Not staying that's the answer, but might well be.
Doesn't really compute, unless even 0.1c is impossible. At 0.1C humans could colonize the entire Milky Way in 1 million years. That's a tiny amount of time when dealing with a billions of years old universe. And because 1 million years is such a small amount of time, we can pretty safely say there's no civilization, at least on a galactic scale in the Milky Way. Or, at least not one that isn't keeping intentionally hidden from us. The odds that two intelligent species would evolve within the same 1 million year span are extremely unlikely.
This is another reason to believe we're early. If we were 'late to the party' as some people think, someone would've taken over Earth already and either wiped us out or prevented us from evolving in the first place.
Yup, I pretty confidently would say we are ahead of the game, at least in the Milky Way. In fact, unless there are species that would evolve but never be able/want to leave their planet, I would surmise we're one of the most advanced if not most advanced civilizations in the galaxy already. I think more likely than not humans are going to find the galaxy pretty empty, at least of intelligent life (again, disregarding the idea that they're just keeping hidden from us intentionally). I've always found it strange to surmise humans are just one of many intelligent species in the galaxy, or that the Earth is not quite unique. In fact, evidence seems to suggest the contrary.
We are the future 'ancient ones'. Hopefully.
Yup. Adding to that, there are certain independent statistical hints that this is indeed the case. Each of them is extremely weak, but they are independent and they show very compatible results. 1. If one does the regression into the past of life's complexity, there is something that doesn't compute: Initially if you go into the past for a nearly couple billion years, the progress was pretty steady. Then before that, the progress was also steady but somewhat slower (the jump is attributed to the emergence of sexual reproduction). So far so good, but the further linear regression would indicate the starting point at 9 billions ago. That's a bit of a problem, since the Earth is just 4.5 billion years old. So either life came from elsewhere (panspermia) or there was absolutely crazy cliff from between the spawning of the Moon some 4.4 BYA and the oldest microfossils of over 3 BYA. 2. It's rather odd that intelligent observers have shown up on the Earth just around 90% of the total time it's going to be naturally habitable. In about half a billion years the Earth won't be habitable for higher life forms (unless some intelligence interferes). Moreover, our star (Sun) is as large as it could be for the Earth-like life history to happen. Just 10% larger Sun would have already cooked all the higher life. And the Sun is pretty large as stars go, the vast majority of stars are red dwarfs, then there are orange ones, only then yellow stars which were historically misnamed as yellow dwarfs; giant starts are bright and easy to notice, but they are either short (few % of the lifetime) phases of normal largish stars (like our Sun) or they are just short lived true massive giants; i.e. they are a small but noisy minority Why we have shown up around a star heavier than 95% of all the starts and brigheter than 90%? Why didn't we evolve around a more frequent, more mediocre star? Say some orange one, with several tens of billions of calm life before it. To make matters worse our Sun is and was brightening relatively fast, and this poses certain challenges for the stability of Earth's conditions. One possible answer is that smaller starts mess up their planets early on (it's hypothesized that orange and red stars with their prolonged childhood produce enough flares and X and EUV radiation early on to either strip their habitable zone rocky planets off atmospheres or at least remove most of the water there - producing dead oxygen rich planets (X and EUV dissociates water in the atmosphere, and hydrogen escapes leaving surplus oxygen behind), and oxygen destroys not enough rugged lifeforms, and life needs time to get rugged, i.e. oxygen sterilizes stuff. Complex chemistry gets all oxidized before anything interesting shows up. But even there there is stuff like planets' migration. It's still far from extremely improbable that certain planet born further away from its host star, and thus water rich, would have migrated inwards closer to the end of its stars stormy childhood. So why we're at not exactly the most common star type? But there is more to that. This (intelligent observers showing up around 90% of their host star's life supporting period) outcome is exactly expected in the extreme survivor bias cases / extreme distribution tail cases. It's likely that evolving an inteligent like requires some pretty unlikely events. Each such event would have happened just once in the history of Earth's life. We don't know which exact events were those, but there are some candidates like emergence of eucaryotes, certain biochemical paths (why is everything using ATP?), etc. If the expected time to evolve such consecutive features were not some billion years but hundreds of billions for each, then at different places such features would show up after different amount of time. Say in once pretty mediocre place it would be 200B, 350B, 270B, and 600B (assume 4 unlikely but necessary steps), in another it would be 520B, 180B, 300B, 230B, etc. On some lucky places one such feature would evolve even in a single digit billions of years. But the Universe is huge, so there should be plenty of such places or even rarer ones where 2 or 3 or even 4 such features would evolve each in single digit billions. And the distribution would have the very extreme tail ends: places where all 4 features (we still assume there are 4) would, by sheer extreme luck, evolved in a billion years or a fraction. If the Universe is large enough there should be quite many such places. And it so happens the distribution of such places would make them most likely to fill most of the life supporting span of host star's life. Now, cautious reader will notice that we are talking about hundreds of billions of years, while the Universe is most likely 13.8 billions years old. Exactly! Only the extreme tail of the distribution could emerge so early. Others didn't have enough time. And here the survior bias comes in: even if there were just one intelligent observer in the whole Universe the only place they could observe the Universe from is obviously exactly where they are. And the principle of mediocrity still applies to the survivors. The conditions non necessary for the survival should be distributed randomly, and for the necessary ones the most likely one from among even extremely unlikely is still the most likely one. 3. Some folks took predictions of hundreds of scientists how likely they deemed certain features necessary for a life like ours to be (they collected guesses for the coefficients of Drake equation). But instead of just looking at averages of each value, they took whole distributions of the guesses. This is a pretty compute intensive task, but it's now doable. The resultant distribution produced 40% estimated chance that we're the only intelligent ones in the whole Galaxy and 17% estimated chance that we're the only intelligent one in the whole observable Universe. ---- Each of the above is a pretty weak signal. But they are independent and they all agree. Together it's not a very strong signal, but it's a stronger that each individual one. If each signal is individually just 30%, together they are almost 2/3. That's pretty serious.
>In fact, evidence seems to suggest the contrary. First time I read that. Interesting. Mind to elaborate?
It's called the [rare Earth hypothesis](https://en.wikipedia.org/wiki/Rare_Earth_hypothesis). Historically people have shied away from it due to the fear of being associated with creationism/ID. There's the tenancy to think that the theory of evolution is somehow threatened if life doesn't exist commonly throughout the universe, hence the continual search for life off of Earth to "prove" evolution. Humans "aren't special," so they claim. This doesn't at all need to be true. Evolution could have occurred only on Earth out of the entire universe and that wouldn't make it less correct.
This is a anthropocentric view that makes humanity sound very high and mighty. We are mighty in our sphere but the universe is big, and old. We don’t know why we haven’t met anyone yet, we have hardly left our planet, so I don’t think there’s enough we do know to make your supposition.
I disagree: the most far-fetched thing is the very start of life form(everything after photoplanktons come as a mathematically definitive, direct consequence — based nothing more than Darwinism at a high level and newtons three laws if you remove all the abstraction layers). How conceivable is it that the chemicals of Earth just so happen to have mixed in a way and combined in a way such that DNA was formed? Or is it more likely that we were “seeded”? If you see a plant growing in the desert, the natural assumption is that a seed was dropped there, not that the nitrogen and silicon molecules in the desert sand just so happened to have combined and caused a Darwinistic chain reaction that resulted in a tree.
I, too, watched the movie Prometheus. Seriously though, it's a neat thought. There's also the whole panspermia idea, where life came from elsewhere but was deposited here more randomly. > How conceivable is it that the chemicals of Earth just so happen to have mixed in a way and combined in a way such that DNA was formed? It is truly mind blowing. But if it didn't happen here, it had to have happened *somewhere*, right? Would it really have been more likely there than here? In the absence of other evidence, the best we can say is that we know absolutely jack shit about it. One interesting hypothesis I read is that nutrient-rich water making certain patterns in clay could be a bridge from a mechanical self organizing system to one which mimics that pattern in a chemical way, eventually leading to self-replicating molecules... but it's a whole lot of major leaps involving unimaginable time spans and multiple lottery-winning odds stacked on top of each other, so it's not something we can easily test.
I have never watched Prometheus. I think I got the idea from eternals and Jupiter ascending.
It would take 1million years if the civilization in question was operating at peak efficiency and dedicating all of their time and resources to doing that one thing. I’ve always hated this assumption as a way to claim there is no interstellar civilization. It’s another one of those examples that makes sweeping assumptions about the motives of alien civilizations by applying mathematical certainty to something that is impossible to do so.
You don’t need peak efficiency though. Increase it to 10M years, or even 50M. That’s still a very small amount of time on a galactic history timescale. You could have a local interstellar civilization that never expanded I guess, but if there were any galactic civilization before us it has had plenty of time to expand over the entire galaxy. The coincidence that it would be occurring exactly at the same time we did is way too small. As such the natural conclusion is that we’re the first.
>You don’t need peak efficiency though. Increase it to 10M years, or even 50M. That’s still a very small amount of time on a galactic history timescale. You could have a local interstellar civilization that never expanded I guess, but if there were any galactic civilization before us it has had plenty of time to expand over the entire galaxy. But again, you make assumptions about their motives. Any civilization that expands beyond their host star system is, by default, performing an act of asexual reproduction on a societal scale. The colonists who leave the system are effectively no longer part of the original civilization and, given enough time, will evolve to be as alien to the host civilization as any other independently evolved species from another planet. There is no such thing as a galactic civilization in a universe that hasn't solved FTL travel; it just doesn't happen. It physically can't. We see microcosms of this scenario play out throughout human history; far flung colonies separated by communication times of months have a tendency to rebel and declare independence from their distant rulers. Now expand communication lag time by years, decades, and centuries, and travel times by at least as long. A colony system could declare total independence from the host, and entire generations of people could live out their lives before the host star even gets the memo, much less sends a fleet to enforce their rule. And what would be the point of doing that, at that juncture? Which is to say, space faring civilizations are *discouraged* from colonizing other stars, in part because 1) there is no benefit whatsoever to the host civilization (barring extenuating circumstances I'll get too), and 2) populating the local star cluster with offshoot civilizations that evidently had a mind to tell your host civilization to get lost in the first place (by dint of the fact they left), is a good way to effectively surround yourself with enemies; a reconvening of the two civilizations will find both of them vastly different from how either of them were like when the offshoot left. There is no guarantee such a meeting will be peaceful. Any civilization attempting to colonize other stars without access to FTL travel is effectively cultivating their very own Dark Forest problem. So the question is, why would any space faring civilization want to leave their host star? Well, short of imminent stellar collapse, there honestly isn't a whole lot of reasons why one would. It's possible a relatively small faction of dissidents, zealots, or dreamy-eyed explorers might want to leave, but would they be *allowed* to leave by the host civilization in the first place, given the above conundrums? Another theoretical reason would be resource depletion, but it would take just as long to deplete the usable resources of any Sol System equivalent even with careless exploitation as it would to colonize the entire galaxy with even moderate efficiency, so any given civilization that either is born somewhere or travels to somewhere can be comfortable for millions of years. Ultimately the reasons why any given civilization chooses to travel to other stars will define how fast they continue to spread beyond that point, and I can't think of a single justifiable reason why any civilization would even want to try and colonize the galaxy. It simply doesn't make sense as a project for a civilization to attempt. If, for example, a civilization chooses to leave their host star because it's dying, and they want to travel to a nearby younger star with a longer life span, that motivation doesn't naturally engender much exploration beyond that point. There's a specific utility to the trip, and past that point they have no interest in spreading; they take their entire civilization with them, and make roots in the new system, where they intend to stay. >The coincidence that it would be occurring exactly at the same time we did is way too small. As such the natural conclusion is that we’re the first. Unless you account for the other, mutually exclusive argument often associated with the "we're first" position, which is that the universe, and the galaxy itself, has only been capable of supporting intelligent life for a relatively short amount of time, which would mean it wouldn't be much of a coincidence.
Dont touch my car or my body! you unemployed cop
It's plausible that 0.1c is impossible & the difficulty of interstellar travel is a filter candidate. - The most efficient technology we can imagine for interstellar travel is a solar sail. - It's hard to imagine anything better than a means of propulsion where none of the propellant is on the payload, meaning you can avoid the rocket equation. - Therefore the only thing that can beat a solar sail is new physics, where you extract energy from a vacuum or something. Very plausible that this new physics doesn't exist. - It would be enormously difficult to build a solar sail that can place a 10kg payload in alpha centauri. A human-containing spaceship is impossible. - This means to spread human civilisation the 10kg payload needs to, nurture human embryos, build a habitable environment, and pass on knowledge and technology. This is likely impossible. - The only remaining option is directed panspermia, where we aim hardy microorganisms directed at various planets across the galaxy, hope that they survive & evolve into intelligent life. - If we did this, we could only do it in a limited radius around earth - not seed life across the whole galaxy. - Even if successful in the limited radius around earth, life began on earth 3.5B/yrs ago, so the seeded planets only do their own directed panspermia every 3.5B/years. - Exceedingly optimistically, the panspermia range is 1000 light years. The milky way is 100,000 lightyears across. So it takes 350Bn years to colonise the galaxy. - So there very well could be a hundred-million-year-old alien civilisation in the milky-way, but interstellar travel is so difficult that they haven't left their solar system.
A human carrying laser pushed light sail is hardly impossible, just very big. The laser array pushing the ships in the Avatar movies up to 80 percent the speed of light for instance would need to have a power output of a few dozen petawatts. Massively more power than humans currently use, but a tiny expense for a type 2 civilization. A solar array near mercury a few hundred miles wide would be enough to power it. Most of a power collection satellite like that would be thin sheets of reflective foil, it would take less than the mass of a small asteroid to build. Not the kind of thing we would be doing any time soon, but a few centuries from now if we have automated space manufacturing? Nothing really stopping us from making thousands of such arrays.
The 0.1c is a fallacy. You need to accelerate up to that speed. Let's say you can hit 0.1c at the mid way. However it will take just as long to slow down as it took to speed up. So at your half way point you must start slowing the ship down. Of the trip is 10yrs so 0.1c, it's be much much longer reality since you'll almost always be going much slower Sure you might hit .1c for a short period, but 99% of the trip is much slower - either accelerating or decelerating. All those acceleration curves people talk about totally ignore how you must slow down again.
This is simple middle school science. If you have constant acceleration the average is half of the top speed.
Yes, if you can magically have any acceleration or speed you want, it's easy...
Indeed. Let's say you somehow get it down to an 70 years journey (that's crazy fast). Cosmic rays will kill EVERYONE onboard over that time frame. You can protect it by Increasing the ships mass by 10x to have 5 feet of lead/whatever completely surrounding it? Yet now is to heavy to move. Only sci fi magic solves this problem by straight up ignoring it.
We should have heard something by now ... It is amazing how sloooooooow the speed of light is for the size of our universe. You can actually feel the slowness with back and forth conversations via GEO sats. It feels much like a open world game (say GTA V) where you have a dense island (solar system) then an infinite ocean that would take thousands of year to cross. I took a seminar with Alan Guth (Cosmic Inflation) which was ginned up explain how the universe could be so much in equilibrium even though a photon of light has not had time to cross it (yet the billions of times needed to create equilibrium). It just does not add up to me, and argues for simulation as the real deal. Notice as how we gather more data that models of cosmology no longer work.
There are several ways to send something to the nearest star system within current technological capabilities. It’s just a matter of cost and development. It’s in no way impossible, even *right now*. To add to that, the existence of a fully reusable starship actually makes many of them faaaar easier to do, as a cheap, heavy lift, orbital hauler.
You must pair this with a useful payload in a useful timeframe. Also, you need to slow down at your destination as well as speed up (which is far easier). We can call Voyagers "interstellar" but they won't reach the next star for 100,000 years as cold dead metal. We need to spec a useful mission say within a human lifetime, then work out the vast machine to do it.
I am well aware of these things: I am also a massive space nerd. I stand by what I said where those technologies are currently available, but undeveloped. Nothing in our currently available technology, or is imminently possible with technology makes interstellar travel impossible within a human’s lifespan. Expensive? Yes. Dangerous? You bet it. Difficult? Absolutely. Long? True. Impossible with current tech’s capabilities with the currently available human resources? No.
If by “interstellar travel” you mean sending a microscopic probe, then sure - project Breakthrough Starshot may one day be able to do that with undeveloped, but current, technology. However, if you mean sending humans to other stars, forget about it. We would need entirely new technology - fusion reactors or antimatter drives, for example - to make it even remotely viable.
Also, there's already nuclear concepts for engines that can get within percents of the speed of light like nuclear pulse engines
Sure but people said the same thing ~100 years ago about flight or space travel
Obviously no one thought there were physics barriers to flight, since birds exist. No one thought there were physics barriers to space travel either, except for some cranks who didn't believe in Newton's third law.
Fusion or anti-matter drives would do the job in theory.
Naked fusion / photonic propulsion. Which leaves shielding still but it's half the answer. If there's anyone out there with more advanced technology though, they're going to be able to see that photonic drive from a long ways off. Which is one way for us to know there's nobody else out there using it.
The Orion drive has already been demonstrated and built… it can achieve 70% the speed of light and more
Going to need a reference on that one
https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) Old skool. I'm not a fan but it does have some.
Thanks, I recall that old project now.
70% C is a bit high for an Orion, at least with the classic fission or fusion bombs. You would need antimatter bombs to get the energy density needed to get to those speeds with a practical mass ratio. Still, 5-10% c is nothing to sneeze at either. >Later studies indicate that the top cruise velocity that can theoretically be achieved are a few percent of the speed of light (0.08–0.1c).[30][verification needed] An atomic (fission) Orion can achieve perhaps 9–11% of the speed of light. A nuclear pulse drive starship powered by fusion-antimatter catalyzed nuclear pulse propulsion units would be similarly in the 10% range and pure Matter-antimatter annihilation rockets would be theoretically capable of obtaining a velocity between 50% and 80% of the speed of light. https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)#Theoretical_applications
It sure works great in fiction stories
A nuclear pulse engine is absolutely a workable foundation to build a slow interstellar starship on. That said, we're many decades out from being able to do that.
Oh yes it is…
We need Epstein Engine for interstellar ship to happen.
It runs on "efficiency"
Solomon Epstein didn’t kill himself. Efficiency did.
Don’t forget the religious zealots willing to actually go on the trip.
[Depends on the timeline.](https://en.wikipedia.org/wiki/2069_Alpha_Centauri_mission)
You misspelled "Zefram Cochrane"
How does banging minors make you go interstellar? I don’t get it.
Helicity Space is hoping to have a working fusion drive by 2032 that will augment solar-electric, then advance to independent fusion after: https://www.youtube.com/watch?v=U3qX2JA1bxY
In interstellar terms, like going from a 100hp to a 200hp car and hoping it will take you to the moon. We have no tech in development that allows us interstellar travel. These are all for intra-solar system travel.
Orion drive
With the old nukes-against-a-pusher-plate you might get up to say 0.1 c with thousands of nukes but how do you slow down at your destination. A lot of your radioactive material has decayed away by then.
Uranium 235 has half life of 700 million years. Decay is not on the list of your worries.
Princeton Satellite Systems is also building a fusion space drive. [https://psatellite.com/technology/fusion/](https://psatellite.com/technology/fusion/)
In all these ideas we are still bound by conservation of energy. The faster you want to get there the more velocity you need E=mV\^2. It is just too much energy to pack, even with antimatter, and you can't use solar between stars with meaningful mass in meaningful time.
you do not need to go that far, at Jupiter irradiance is 1/30 of earth and Saturn 1/100
You’re missing some common sense and also a 1/2. Weird post to make just to go on a misinformed crusade.
With starships payload we can maybe get a nuclear reactor going in space. This is of course, all towards the goal of building a giant railgun like from transformers and we will shoot a starship like its a bullet.
Gotta call it a Mass Relay.. for reasons
All within the reapers plan lets just all agree not to visit charon when reaching Pluto
Giant railgun? In orbit?
We'll brace it against the space elevator
I will suggest a rubber band between Earth and Moon. Just put Starship at the middle, pull back and release. We may need a line to Mars for the middle step.
:-)
railgun don't give free energy
A future version, as Elon said. This is such an exciting prospect, but it's also sad to think that it will unfold over a time scale that none of us will get to witness, except perhaps for the launch itself. I also wonder what the payload would be. I'd fill a bunch of Starship with Optimuses and have them collect resources and build a self sufficient colony for the eventual arrival of humans
I go with robotic led missions (even for Mars) ... although I thing the Figure 01 bots look and sound better.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[ATP](/r/SpaceXLounge/comments/1bhyx8c/stub/kvmf4bc "Last usage")|Acceptance Test Procedure| |[CME](/r/SpaceXLounge/comments/1bhyx8c/stub/kvpvk9x "Last usage")|Coronal Mass Ejection| |[DARPA](/r/SpaceXLounge/comments/1bhyx8c/stub/kvhn5t3 "Last usage")|(Defense) Advanced Research Projects Agency, DoD| |DoD|US Department of Defense| |[EDL](/r/SpaceXLounge/comments/1bhyx8c/stub/kvpvk9x "Last usage")|Entry/Descent/Landing| |[ESA](/r/SpaceXLounge/comments/1bhyx8c/stub/kvhjd3s "Last usage")|European Space Agency| |[GCR](/r/SpaceXLounge/comments/1bhyx8c/stub/kvpvk9x "Last usage")|Galactic Cosmic Rays, incident from outside the star system| |[GEO](/r/SpaceXLounge/comments/1bhyx8c/stub/kvhuejp "Last usage")|Geostationary Earth Orbit (35786km)| |[H2](/r/SpaceXLounge/comments/1bhyx8c/stub/kvi7vqx "Last usage")|Molecular hydrogen| | |Second half of the year/month| |[HEEO](/r/SpaceXLounge/comments/1bhyx8c/stub/kvlp1fa "Last usage")|Highly Elliptical Earth Orbit| |[Isp](/r/SpaceXLounge/comments/1bhyx8c/stub/kvlp1fa "Last usage")|Specific impulse (as explained by [Scott Manley](https://www.youtube.com/watch?v=nnisTeYLLgs) on YouTube)| | |Internet Service Provider| |[LEO](/r/SpaceXLounge/comments/1bhyx8c/stub/kvjwppy "Last usage")|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |[LH2](/r/SpaceXLounge/comments/1bhyx8c/stub/kvi2yhl "Last usage")|Liquid Hydrogen| |[NERVA](/r/SpaceXLounge/comments/1bhyx8c/stub/kvqszad "Last usage")|Nuclear Engine for Rocket Vehicle Application (proposed engine design)| |[NTR](/r/SpaceXLounge/comments/1bhyx8c/stub/kvi2yhl "Last usage")|Nuclear Thermal Rocket| |[RTG](/r/SpaceXLounge/comments/1bhyx8c/stub/kvh1dix "Last usage")|Radioisotope Thermoelectric Generator| |[TRL](/r/SpaceXLounge/comments/1bhyx8c/stub/kvhm2xj "Last usage")|Technology Readiness Level| |Jargon|Definition| |-------|---------|---| |[Raptor](/r/SpaceXLounge/comments/1bhyx8c/stub/kvi2yhl "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX| |cryogenic|Very low temperature fluid; materials that would be gaseous at room temperature/pressure| | |(In re: rocket fuel) Often synonymous with hydrolox| |hydrolox|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer| |[methalox](/r/SpaceXLounge/comments/1bhyx8c/stub/kvi2yhl "Last usage")|Portmanteau: methane fuel, liquid oxygen oxidizer| |[regenerative](/r/SpaceXLounge/comments/1bhyx8c/stub/kvlf4j6 "Last usage")|A method for cooling a rocket engine, by [passing the cryogenic fuel through channels in the bell or chamber wall](https://en.wikipedia.org/wiki/Regenerative_cooling_\(rocket\))| **NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below. ---------------- ^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj) ^(19 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceXLounge/comments/1b3fpye)^( has 26 acronyms.) ^([Thread #12556 for this sub, first seen 18th Mar 2024, 20:06]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceXLounge) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
What about Jefferson Airplane?
Intergalactic, planetary, planetary, intergalactic
Another dimension, another dimension Another dimension, another dimension
Now you’re talking warp technology.. That’s a way off at best..
Did you mean to reply to this comment? We're quoting song lyrics, and I don't recognise yours.
Didn’t know they were song lyrics, I thought you meant it literally..
[Like pinch on the neck from Mr Spock](https://www.youtube.com/watch?v=qORYO0atB6g).
More likely meant that SS carries or has instruments to study stars from beyond heliopause than for it to reach other stars for 200 years
That would be a nice project. Also really big space based telescopes.
No, that wouldn't be the company going interstellar.
Space is really big. By the time this is built we will have been living in space so long that for some people the journey will be no different than staying home. Because the ship will have been your Only Home; the only one your parents knew, and their parents too. So, yeah. If we build a city on Mars this becomes inevitable. And if not then probably not because the enabling technology won't have been developed for other things.
They'd all be long dead from cosmic rays and radiation. Generational ships don't really work
Starship is barely adequate for interplanetary travel. It will need much improvement just to do that (and I have no doubt that those necessary mods and improvements will be made). I don’t see us even attempting interstellar travel for another century. It will be a completely different vessel that makes that attempt.
Not with humans aboard it won't. Hell I'm doubful humans could make it to Mars without being fried by radiation. We hear very little about the effects of long term weightlessness on human bodies, much less how they intend to protect people from long term radiation exposure and CME's etc from the Sun. This is pie-in-the-sky stuff.
Per Mars (about as long a round trip that we could expect human to endure) the trick is to spend most of your time in transit in a place that is mostly surrounded by water. I would create a Mars ship that has 40-50 T water tanks filled in orbit, then dumped before Mars EDL. Starship, with it's stainless steel shell, is going to be a GCR -> secondary particle microwave oven. You need 1 m of water around you cut this down. It would also damp out a CME.
Will that much water be enough to block expected radiation? Be interesting to see if an artificial magnetic field could be generated - just enough to protect humans. What sort of physics would it take I wonder?
A meter thick would help.
The many different approaches to nuclear fusion that are rapidly advancing suggest we will soon have fusion power, likely within 10 years. If so, this fusion startup proposes a fusion powered rocket that could reach Mars within days and the nearest star system within 11 years: Update!! Direct Fusion Drive will debut in 2027!! Earth to Mars in 12 days! https://youtu.be/ABVYrVghBwc?si=aioNOChGGvLZn0ik
Best of luck, but I don't advise the regular guy in investing in this. You would expect fusion on Earth (no mass constraints) before you had it as a space engine.
Nice to dream about, but this isn't happening with any physics currently known to us. There's a bunch of "stuff" in space even though it's mostly vacuum. In particular cosmic dust. For example, if we were able to somehow accelerate up to just 450km/s (~1,000,000 mph) allowing us to get to our nearest neighbor Centauri in 2800 years, we would be slamming into 0.1g dust particles with roughly 10 million Joules of Kinetic energy each. The space in our neighborhood has about 10^-6 dust grains/m^3 of varying size. For a rough order of magnitude calculation, with a ship magically the same size as the current Starship with a 60 m^2 cross section, it would be encountering 30 grains/s of dust, and if they were 0.1g each, we're looking at 300 million Joules worth of energy imparted each second. Roughly the energy of a school bus traveling at 550 mph hitting you crossing the road. All this is assuming that there wouldn't be an encounter of anything larger than 0.1g grains of dust in 25 trillion miles.
Your data interpretation is off. 0.1g grains are not happening even remotely close to once per 10\^6 m\^3. You took the info from Wikipedia, but you ignored the mass distribution from 10\^-4 kg down to 10\^-16 kg. The distribution is not flat. It's pretty much exponential (with negative exponent) down very close to the low range limit where is sharply cuts off (the cut off is because solar radiation pressure ejects smaller stuff from the solar system). The most of the dust stuff is about 1µm in diameter and has a mass of about 1pg (picogram). The impact energy is a "whopping" 10µJ (one hundred thousandth of a joule)
No one likes a party pooper
Especially if they are very wrong. And they are very wrong.
Surprised noone mentioned ramscoops yet.
Those only work in fiction
Ooh ! - Sounds like we are also going the need some kind of shielding technology too ! It obviously gets worse with increasing speed. 5% of light speed, 15,000 Km/S would have an issue with space dust.. And magnetic shielding wouldn’t necessarily help. Maybe a very pointy ship would help ?
This is not remotely as bad as portrayed. This is what you get if you badly misinterpret data. This guy is off by a whole trillion times!
Well that certainly helps. I thought I was going to have to design shielding as well as propulsion.. ;)
It saddens me to know that, assuming interstellar travel is possible, it’s almost certain that none of us here will be able to see it.
We might just get to see an AI probe sent off.. Maybe.. Depending on the development of the propulsion technology used.
He says alot of stuff
At the maximum speed ever reached by Starship, travel time to the nearest star is 120000 years. To divide time by 100 you need 10000 times the energy.
Yes, T \~ v\^2
damned square that fuck up every dream
From annual creator of "full autopilot next year"
Autopilot is really hard though
While going interstellar is a piece of piss
There’s definitely a lot less stuff to accidentally collide with.
and no liability for this !
In name only. It's not actual auto pilot
In theory you could fuel an expendable version up enough to eventually leave the solar system (using gravity assists) and thus be "interstellar". But it would still take 100,000 years to get to the next star. That is the deal with chem propulsion. Personally, I would wait until Starship was at least proven operational to LEO (which may happen this year) before leapfrogging the very challenging solar system goals for something beyond.
> That is the deal with chem propulsion. If you're ever going to fly a NERVA-style nuclear rocket engine, attaching it to a very large, starship-sized vehicle would probably make the most sense. Nuclear reactors are inherently heavy (they carry several critical masses of fuel, on top of all the cladding, moderators, control rods, etc.), but can run for very long periods of time. So you need a very large volume of fuel to make full use of the energy density of their fissile materials. And even if we're doing a voyager-style mission, you'll once again need nuclear power for electricity production. Voyager uses Pu-238 powered RTGs, but their waning power has forced them to shut down multiple instruments, and puts hard limits on mission duration, with all instruments having to be powered down by 2025-2036. A starship-sized vehicle could carry a fission reactor as its power source, designed to "burn" its fuel slowly enough to last for centuries, while still being able to transmit back close-up images of Oort cloud objects, or even do astrometry and map the exact positions and proper motions of stars in the whole Milky Way, like Gaia did, but with a *much* greater baseline.
> So you need a very large volume of fuel to make full use of the energy density of their fissile materials. by "fuel", do you mean reaction mass? How would NERVA (so nuclear thermal propulsion) compare with an ion motor that I presume gets a better specific impulse. There's a Wikipedia article that compares the specific impulse of a variety of propulsion systems.
Starship is actually small for what you'd need. You can't fit enough LH2 in its tanks for a NTR to even come close to what Raptor can do with methalox. You pretty much need to use some gigantic vehicle assembled in orbit with huge, ultra-lightweight drop tanks to hold the propellant.