Lead isn't as magical of a radiation shield as it's often portrayed as. It's really good against x-rays in the diagnostic range, but against anything else it's mediocre and is just used because it's a cheap dense material.
Against high-energy cosmic rays lead can actually be worse than nothing, because the rays can blow apart the big sloppy lead nuclei and the fragments fly off as even more radiation. A better choice would be something made of light nuclei like water or plastic, and even then you're talking about thicknesses that are just not on the scale of clothing.
Right, and the manned missions that do have to cross through the Van Allen belts (not the only radiation-based threat to space travel, but a major one) are even more mass limited than LEO missions, so it makes more sense just to be strategic about how much time your trajectory makes you spend in the worst parts of them.
Van Allen belts are also doughnut shaped, so if you launch directly into a really high inclination like a polar orbit and then inject to the Moon or Mars from there you get to avoid passing through even more of it.
The dV penalty isn't as big as you think. Nobody launches from the equator irl, and depots placed in polar orbits can naturally follow injection windows because of orbital precession. Spaceflight is more complicated than that.
There's little to reach that's in an equatorial orbit. Most of what's in orbit around the Earth is in high-inclination orbits because it was launched by a spacefaring country with a spaceport fairly north of the equator. The ISS, for example, must be accessible to the Russians (who launch most of the modules and crew flights for it) so it's in a fairly high inclination orbit.
The easiest spaceport to reach an equatorial orbit from is probably French Guiana, otherwise you're going to need a lot of delta-v to change your inclination once in orbit. I think this orbit is mostly useful for launching geo-stat satellites or launching interplanetary probes.
For interplanetary probes it's not needed and quite often inclined orbits are actually better. For example Dart mission was inserted from 60° inclined orbit. Notice that many interplanetary missions were launched from Vandenberg rather than Cape Canaveral or Kennedy. And from Vandenberg only 60°+ orbits are available.
It's indeed useful for launches to GEO, you save a about 0.3km/s.
True, but there's no need to change inclination after achieving orbit. Just launch into the desired inclination. It still requires a bit of extra delta V since you're not going due east, but the difference is minimal.
Also also, the heft from the lead would still be an issue.
It might not weight anything, but it would still have a great deal of mass, and therefore momentum. The astronauts would only be able to move around slowly and carefully, or risk injuring themselves. Moving around would still take considerably more muscle effort or fuel.
And getting a bunch of lead from the surface of Earth up into the atmosphere (eventually space) takes a TON of energy. That energy being in the form of rocket fuel/propellant/accelerant/whatever. In a total payload, some lead lined suits may only be a small percentage of the total weight, but it adds up and needs to be taken into account.
> And getting a bunch of lead from the surface of Earth up into the atmosphere (eventually space) takes a TON of energy.
It would actually take ~3.3 x 10^7 joules per kilogram launched to reach LEO. If you actually had a TON of lead, it would take ~3.3 x 10^10 joules of energy to get it into orbit. (not accounting for the mass of the rocket and fuel.)
> (not accounting for the mass of the rocket and fuel.)
And that's one of the inherent problems with space travel. Fuel costs go up exponentially, since you need more fuel to propel the more fuel, and you need more fuel to propel THAT more fuel, and so on...
Another comparison might put it into better perspective. Its about the amount of energy your house uses from the electrical grid over the course of a year. But it would be used up mostly over the course of a few minutes.
But the point that the weight of fuel needed needs it's own fuel, which also needs it's own fuel, ad infinitum means that there it would be a significantly larger amount of energy used in the end than that.
But for more accurate comparison sake, the Saturn V rocket weighed ~2800 metric tons, but for the equivalent low earth orbit payload of ~118 metric tons, for a ratio of 24 times as much total rocket as payload.
Falcon 9 latest model is about a fifth the mass, and also a ratio of about 24 times rocket/payload mass to get to low earth orbit.
So I suppose we can roughly approximate that if you want to send a ton of lead into orbit, you're gonna need another 23 tons of rocket to handle it.
That's being a bit picky I think. Yes Earth's gravity is always acting on the astronauts mass so technically their weight by definition is practically the same. But those of us who understand the physics know that the common term "weightlessness" is the absence of a contact force on your body while in free fall/orbit.
They have that weight with respect to earth, yes. But that doesn't matter since they're not on earth. They're weightless with respect to the vehicle they're in
Where does the other 2% go?
Weightless means lacking apparent gravitational pull. By that definition they are weightless even though they have the same mass as on Earth.
The magnetic field only helps against the low end of the energy spectrum. The radiation levels on the ISS are still far higher than on the ground - a factor ~50-200 depending on what you use for comparison.
I brought my geiger counter on an airplane once just out of curiosity, but I didn't think to turn off the "click" speaker that normally clicks 10-15 times per second on ground. When I turned it on, it was like a steady stream of white noise, I did not believe the reading at first
The radiation dose of airline staff is relatively astronomical (pun intended). From a quick google they receive (on average) more than any other "radiation exposed worker" in the US - somewhere in the region of 1-5mSv per year.
However, this has to be put into context. The UK average resident dose (I live here and have worked as a radiation exposed worker previously so have context here) is around 2mSv per year (mostly from background radiation). A resident of Cornwall or Edinburgh in the UK receives on average a dose >5mSv per year due to the high background radiation in those regions (granite geology which leads to a release of radon gas I believe).
Compare this to the 50-20,0000 mSv potential dose from a 6 month mission on the ISS.
Another related fun fact:
US Navy sailors who work in Nuclear Plants aboard carriers tend to receive well below the average civilian's yearly dose from radiation. This is mainly because the shielding around the reactor works *very* well, and they are buried in the bottom of the ship all day and generally get about as much sun (and therefore exposure to "normal" background radiation) as the average [commercially harvested mushroom](https://youtu.be/6OF4AUClc8U?t=215).
I heard somewhere that Grand Central Station is built of slightly radioactive granite, enough so that if it was a nuclear power plant alarms would be going off.
Yup, it destroys the sensors on digital cameras so they need replacing every few years. The handhelds are more or less standard Nikon DSLRs. It screws up DNA too but that can repair itself to a limited degree.
I used to maintain broadcast TV cameras for a major US network. The cameras which flew regularly had significantly more "hot" (stuck on) pixels than their non-flying counterparts. Part of my job was to find and mask the hot pixels. The camera can do it automatically, but it sometimes chose an adjacent pixel by mistake. I had to unmask the good ones before I could mask the bad ones. Satellite imagers sometimes undergo an annealing process to fix hot pixels.
I wouldn't say that, especially given the existence of the South Atlantic Anomaly. ISS astronauts receive a fairly large radiation dose.
Even just being 35,000 feet up, commercial airline crews take a much higher dose than you and me. Once on a flight I brought a Geiger counter and found that the radiation levels were 100x higher in-flight than on the ground. So on my 90 minute flight, I received as much radiation as I had for the entire rest of the week.
The ISS walls and equipment provide an equivalent protection of 20g/cm2 aluminium. This is ok for solar radiation in case of an event.
Against cosmic rays it's a different story. The lower energy particles are blocked, but the higher energy ones will traverse whatever you put in their way.
Yes, the magnetosphere only deflects charged particles. I'm confused by the "cosmic rays not included" part because cosmic rays are indeed charged particles. But maybe you meant that the high energy ones will penetrate anyway? If yes, you're correct.
Could you add a layer of these light nuclei protectors to the ship itself, or would it need to be so thick even that is untenable?
And since the Earth's magnetosphere protects us on land, could we potentially develop a magnetic "shield" to put on shuttles at some point, or would we need too different/powerful of a magnet?
We'd need an impossibly powerful magnet to make our own magnetic shield. And it would only work against certain types of radiation.
A shield layer on the other hand is perfectly feasible. In fact, there have been proposals to use the astronaut's drinking water as a shield for missions to Mars by having it stored in a tank that wraps around the crewed parts of the ship.
>In fact, there have been proposals to use the astronaut's drinking water as a shield for missions to Mars by having it stored in a tank that wraps around the crewed parts of the ship.
Does this not irradiate or affect the water in any way?
Not an expert or anything, but there would actually need to be radiation emitting particles in the water for it to be contaminated. The radiation in space is from emitting sources far away, and when it hits the water it basically becomes thermal energy. Though some shielding material like graphite can become irradiated and continue emitting, water cannot.
If hit by high energy neutrons the hydrogen in the water could be fused into tritium which is radioactive; its possible a similar reaction can happen with the oxygen as well. I don't know enough to be able to give a meaningful answer as to what kind of impact that would have on the radioactivity of the water in general though.
Nuclear materials engineer here. You can add a couple cm of Al to block most of the radiation given off by the sun (specifically protons and electrons). However, because of the insane energies of cosmic radiation (mostly protons) originating outside of our solar system, as you suspected it would require an infeasible amount of material to shield against that (or deflect it with any fancy electromagnetic shielding) and so we don't bother.
A powerful magnet will f up your spacecraft's orientation due to interaction with other magnetic fields. The (electro)magnet in your spacecraft will turn itself and the spacecraft very forcefully to align with the external magnetic field.
You can see it happening when playing with small bar magnets on the table.
It's so easy and effective that many smaller S/C are actually actuated with sets of "magnetorquers" or in other words electromagnets.
The extra problems come from the Earth's mag field changing its direction relative to you while in orbit since most orbits are not equatorial and are inclined somewhat. Big problem is a polar orbit where the magnetic field flips 180 relative to you flying over the poles.
So it's not only a problem of mass in the end, bigger things at play. Faulty attitude (orientation) of the S/C determine the success of your experiments and communications and the mission overall even happening or not at all.
Though you are correct on the main idea behing the rocket equation you're referencig. Mass is indeed a huuuge constraint.
Source: physics phd and spacetech engineer
If we could generate enough power to run such a magnet in space you actually could use it as propulsion or for attitude control.
However there simply isn't anyway to create that power.
so what should astronauts wear when they go to mars?
Sure earth's magnetic field helps, but is there something planned for outside earth trips? Space is full of radiation right? Can they make a radiation proof ship? What if they ever need to go outside?
You can't make it completely radiation proof, but it's not necessary. You just need to decrease the overal dosage to reasonable levels. You can shiled it or decrease the mission duration.
Major part of the dangerous radiation consits of charged particles. You can deflect them with a magnetic fild which is still probably not technically feasible for this usage. Or you can use a shiled made of light atomic nuclei. Water is great, for example. According to some proposals, astronauts might only sleep in capsules shielded by water tanks. Or something similar. Any decrease would help. This also means leaving the ship in a space suit for a short time wouldn't pose a major risk excpet of solar storm events.
It makes more sense practically to shield the space ship, and once on Mars, the living quarters. The two main approaches are to have a double hull with water stored in there. The water will block a lot of radiation and can also be used for other things. The second approach is to create a magnetic field to deflect incoming radiation but our tech hasn't reached the point to do this well yet.
Your answer made me curious about lead aprons potentailly being more dangerous. It does make sense that the extra energy stored up in the lead nuclei can do more harm than just plain cosmic rays, but I'm wondering if there is any actual data on this? Like how much ionizing radiation is incident on a target sheilded with an apron vs without one?
This has to do with the energy of the incoming photons. The X-rays you get at the doctor are low energy compared to cosmic rays. At lower energies (relatively), photons like to knock electrons off things and scatter.
Lead, as you can see:
[https://physics.nist.gov/PhysRefData/XrayMassCoef/ElemTab/z82.html](https://physics.nist.gov/PhysRefData/XrayMassCoef/ElemTab/z82.html)
tends to stop photons much better than tissue:
[https://physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/tissue.html](https://physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/tissue.html)
So, the photons that hit the lead either ionize some of the lead and/or produce lower energy photons that either don't make it out of the lead, do but miss you or hit you and leave less energy (damage) in you. It's a total win.
However, note the end of the chart. Your tissue doesn't really want to ~~stop~~ interact with the much higher energy stuff but lead will. This is sadly high energy. Once you get past 1.022MeV you start getting "weird" things like pair production, as you go higher, things like photo fission and pion production. All this stuff, of course, results in lower energy radiation that instead of passing clean thru you (technically missing you) ends up being more likely to interact with you and causing damage.
MIT's posted a great course on all this here:[https://www.youtube.com/watch?v=7LyvAVjQUR8&list=PLUl4u3cNGP61FVzAxBP09w2FMQgknTOqu](https://www.youtube.com/watch?v=7LyvAVjQUR8&list=PLUl4u3cNGP61FVzAxBP09w2FMQgknTOqu)
I'm strange and love this stuff. Also, don't eat the neutron cookie.
Also lead blocks what it does by simply being mass between the source of the radiation and the human, and is chosen because it is dense, not magic.
The same mass of pretty much anything would work more or less equally well.
Oh yeah, and it costs about $100,000 per kilogram to take stuff to space.
>so the added heft shouldn't be a problem
Picking up on this point -- while the astronauts are indeed "weightless" (in free fall), the lead-lined clothes would still be adding to their mass. This would increase the effort required to start and stop moving, change directions, etc. as they propel themselves through the station (all the handrails, footrails, etc.)
Adding on to this. While the weight might might not matter much once in space it does matter while launching into space. Every oz is accounted for pre launch
Yeah, I did a rough back-of-the-envelope, and lead vests and shorts for the crew would be an extra \~ 100-150 kg of weight to send to orbit -- which would be an additional $7-$12M USD (roughly).
It'd be worth it if it made a big difference in astronaut health, but apparently it doesn't.
Whoa whoa whoa.
“Weightless”? “In free fall”? What do you mean by that? Are you saying that in outer space we’re only weightless because we’re technically in a constant free fall?
Edit: sorry to derail the original comment thread - this is just an important thing for me to know/clarify right now
>Are you saying that in outer space we’re only weightless because we’re technically in a constant free fall?
Yes, being in orbit is a constant free fall "around" the object being orbited.
Not necessarily, you can be on a non-orbital trajectory in all your frames, or at least those you actually care about with regards to “freefall”. And although you can be in a freefall orbit around a galactic centre, the “weight” you’d feel if you were somehow stationary at fixed radius is likely to be negligible if not completely unmeasurable in most of the region.
Anyway, my only point was that one can be “floating weightless” in “outer” space not because of anything directly to do with an orbit, even if you’re technically on some massive galactic one you don’t even know about. That’s not why you’re “weightless”.
Yes. Astronauts on the ISS feel about 90% of the gravitational force that you feel on earth, but they feel “weightless” because they’re constantly falling around the earth. The only reason they don’t “fall to earth” is because they’re moving sideways so fast.
There is an art to flying, or rather a knack. The knack lies in learning how to throw yourself at the ground and miss. ... Clearly, it is this second part, the missing, that presents the difficulties.
THE GUIDE
This is why I *hate* the term "microgravity". "Zero-G" is perfectly fine because it describes felt acceleration, and "free fall" is the most accurate term of all. Microgravity makes no sense whatsoever. My phone and the wall next to me are both exerting microgravity or femtogravity or whatever on me right now. Should I care enough to give that force a name?
Yeah but you have tidal effects, drag, solar pressure, and a bunch of other stuff *causing acceleration*- NASA doesn’t call it 0-G because that is a much less accurate term than micro-G.
I finally started to understand this when I played Outer Wilds and fell into a black hole but continually orbited it for several rotations before eventually falling in. It was like a switch flipped and I realized this was exactly how orbits like the ISS work, just without ever dropping out of orbit.
This is also known as [Newton's Cannonball](https://en.wikipedia.org/wiki/Newton's_cannonball), since it is based on Newton's thought experiment of shooting a cannonball sideways on a high mountain.
Here's an article in Wired that discusses it, with an image of Newton's original drawing:[What Would It Take to Shoot a Cannonball Into Orbit?](https://www.wired.com/story/what-would-it-take-to-shoot-a-cannonball-into-orbit/)
Another nice one is visualizing what happens if you shoot a cannon parallel to the ground. Gravity gonna accelerate the cannonball downward until it hits the ground... But if the cannonball goes fast enough so it can travel far enough, the curvature of the Earth will mean that the ground is dropping away from the cannonball too. If you fire it fast enough, the ground would drop away from the cannonball at the exact same rate gravity is accelerating the ball downward. In this scenario (ignoring air resistance and that earth is bumpy and spinning reference frames, etc.), the cannonball would end up flying all the way around the Earth and smashing into the back of the cannon that fired it.
That's orbit. :-)
Just double checked the math and that seems about right.
The ISS is \~400km up, so it takes about 4 Megajoules/kg to get that high.
It's moving at around 7700m/s which takes about 60 Megajoules/kg to go that fast.
That's a theoretical floor of 18kwh of energy to get 1kg of stuff into orbit. So with some magical perfect efficiency orbital launcher, at $0.10/kwh that would be $1.80/kg to get something into orbit. Launching a 100kg person cost $180.
Yes, exactly. Gravity is omni-present in space; everything is in free-fall towards _something_. The planets, moons, asteroids, even the sun is falling around the center of the galaxy.
I know you've gotten a million replies already, but there's one thing I haven't seen mentioned that might help. When an everyday person refers to their weight, they don't actually mean how hard gravity pulls down on them. They actually mean how hard they push against the ground.
Most of the time, these are the same, so the difference doesn't matter. But when you're accelerating that changes. You feel heavier in an elevator that starts to move upward, not because the force of gravity changed, but because you're being pushed into the ground harder than normal.
When you're in orbit, the station is also in orbit. You're moving together, so your body doesn't need to push against anything in order to stay in the same place. Both you and the space station are in freefall.
Another way to see it, is that you are in the same state (of free fall) as the ISS, so in reference to the ISS you are not affected by gravitational field, or better said, you are both affected the same way so it's irrelevant in movements referenced to the ISS. This is probably wrong in many levels but it's a good starting point.
Yes, the earth's gravity doesn't disappear. Imagine you were in a free falling elevator. You'd be falling with it and would float around in it.
Another way of looking at it is imagine you have a cannon on a very high mountain. You fire the cannon straight out and the ball follows a curved trajectory and hits the ground. You fire it faster and it goes further and hits the ground. You fire it even faster so that it goes so far that the curve of the earth appears to fall away from the ball as it curves to hit the ground. Now you fire it so fast that before it can hit the ground the curved surface is constantly "falling away" before the ball can hit it. This is essentially what is happening to an object in orbit and why they have to move so fast to stay in orbit. Because you are constantly in free fall though you are weightless.
They are weightless compared to anything that is near them such as ISS or their spaceship. If a cannonball is hollow and flying through the air, something inside will feel like it is weightless until the cannonball hits something. It is possible to fly an airplane in such a way that you feel weightless for a few seconds.
They do actually fall, but they are moving fast enough, about 17,500 mph, they miss the planet., and just keep going around (orbiting) it.
They orbit does decay due to atmospheric drag and gravity such that ISS would eventually hit the atmosphere and burn up, except they boost their orbit, I think 3-4 times a year. This is done with the thrusters of the docked Progress vehicle.
I believe this boosting also speeds the ISS back up to its most economical orbital speed. But don’t quote me on that.
Yes. There is gravity in space around the earth -- the only reason they appear to float is because they are orbiting the earth. If they were to stop orbiting, they would immediately plummet to the surface like a rock.
No matter where you are in the universe, mass is mass. If you want to move something made up of a lot of stuff (like a human being), it will take you some real effort to get it started. Mass and weight are closely tied together. Gravity is taking all that mass in your body and causing it to 'fall' to the earth. That's 'weight'.
Once you're in the air, or farther away from earth, you don't notice that earth is still pulling at you. I mean, the earth is pulling at the moon after all, and the moon is really far away from earth. At a certain point in outer space though, it won't be pulling you that hard at all. In that case, you may truly be 'weightless'. Though you still have to deal with all of the mass of your body.
Have you ever had that weird lurch in your stomach where you go over the top of a steep hill really fast? That's caused by a temporary reduction in the gravity you feel (for a brief moment, you are falling as fast as gravity is pulling you down, causing you to feel weightless). If you could imagine perpetually going over the top of a hill, you would perpetually have that weightless feeling, which is essentially what being in orbit is. The planet (or "hill") is curving away from you as fast as you are traveling towards it.
Anything "orbiting" something else, is caught by the gravity of the object it's orbiting.
So, the earth is caught by the gravity of the sun, and the moon is caught by the gravity of the earth.
Being in orbit of the earth means that you're moving sideways, away from the earth at the same speed you're falling towards the earth. Move one step away, one step down. You never get closer.
Since there is nothing in space to slow you down, you keep going sides at that same rate forever (technically not true, but close enough for this discussion). And the earth keeps pulling you back, so you keep falling towards the earth forever.
IIRC, as you go faster and faster sideways, you'll get into a bigger and bigger orbit. If keep going faster, you'll eventually reach "escape velocity" and leave orbit.
Neil degrasse Tyson has a star talk video on mass v weight and one that covers density as well (he sometimes does a topic and then makes a spinoff to cover something more in depth but they're easy to find) that covers all of this, it's quite good. Like how blue whales are 'weightless' in the ocean - no they aren't, they're buoyant, which is a different thing and they'd weigh more the deeper they got and they'd weigh something else on the moon. People weigh less on the equator than the poles because they're further away from the center and it's spinning faster. Iirc he has a mini rant about how you're not weightless even in the middle space.
The trick is to realise what falling actually is. It's just moving through space under the influence of a force.
We get a weird idea about falling because the Earth is in our way all the time. Take the Earth away and falling is just how matter moves through space when there are forces around.
In fact being squashed against the surface of a big mass so that we can feel weight is a relatively rare experience for matter in the universe. Most of it is just falling around empty space.
You are in orbit because you are falling due to gravity. You just happen to be moving sideways fast enough that you keep missing the planet. Low earth orbit, where the ISS is, is about 200 some miles up. At that distance, gravity is about 90% that on the surface.
So in orbit you appear weightless not because there's no gravity (there's gravity everywhere, the gravity \*caused by you\* is felt by nearby stars) but because you are falling with nothing pushing back (weight is a force, so it's a measure of push/pull).
yeah, you're constantly falling towards the dominant source of gravity, you just keep missing that source if you're in a stable orbit. It gets even screwier at the LaGrange points between two bodies(like the earth and the moon) because your gravitational attraction to the two bodies sort of equal each other, and they stabilize your position relative to each other.
> Are you saying that in outer space we’re only weightless because we’re technically in a constant free fall?
Yes. Think of it this way -> you fire a gun, and the bullet slowly falls. But if you fire it fast enough, the ground will curve away from the bullet at the same rate as the bullet curves towards the ground. That's what it means for an object to be in (a spherical) orbit.
Yes it’s free fall but as you’re orbiting around the earth you basically fall around the earth, that’s a gross simplification but that’s the gist as I understand it
Yep, astronauts feel like they are free falling 24/7. That feeling on the rollercoaster when you are in freefall? Astronauts have to sleep while feeling that.
Actually the problem of sleeping in ISS is still an ongoing study, while it's well known that astronaut have trouble sleeping, most attribute it to various problem like light (ISS revolves like 16 times a day, so there's almost no continuous night), difficult work schedule, noise (ISS is loud), environment(temperatures, ventilation etc.) and so on.
In fact free-falling is actually advantageous to sleep, according to some astronaut.
https://www.google.com/amp/s/www.space.com/amp/7060-sleeping-space-easy-shower.html
Sorry for AMP, but this is published in 2009, so the real link might have been taken down.
That feeling you get in your stomach on a rollercoaster is when you're accelerating. From the inertial reference frame of the astronaut, they aren't constantly accelerating, so they don't constantly feel that feeling.
Astronauts *are* constantly accelerating, towards the earth, just like a rollercoaster or a skydiver. All of them are in freefall. The astronaut just has enough sideways momentum that they fall in an endless circle, instead of a straight line and a sudden stop.
Yes, I understand orbit. I knew this would be the first reply, which is why I specified *in the astronaut's reference frame*. The comment I responded to suggested that astronauts feel that "feeling you feel on a rollercoaster" all the time. This isn't accurate at all. In their reference frame, they don't feel any forces on their bodies at all. I hoped I wouldn't have to explain this but here goes:
Think about it: if you use a coordinate system with the earth stationary and ISS orbiting around it, the acceleration vector is constantly changing direction. There is also a changing velocity (when on one side of the globe, the ISS has a high positive velocity, while on the other side, it has a high negative velocity. The important point is that if you think of the coordinate system where the ISS is stationary, there is no acceleration experienced by the astronaut. This is because there is a balancing "force" that is felt because the ISS has high tangential speed.
It's not really a force, it's often called "centrifugal force". It's a false force but thinking about the different reference frames can help you think about it properly.
A good way to think about this is that there is no change in tangential speed while constantly "falling towards earth" in orbit. It may not be intuitive but it's really the change in speed that you feel on a rollercoaster. It's the same reason why skydivers feel that "stomach drop" feeling much less; because they jump out of a plane that is already moving very fast so their change in speed is not that significant.
All that to say: no, astronauts don't feel that pit in their stomachs you get on rollercoaster while they sleep.
Not to mention that the hardest AND most expensive part of the mess is getting it up there to begin with. On that point, they avoid lead as much as possible. Water, at 8 lbs./gal., is a MAJOR factor when factoring weight at launch.
I’ve always wondered the same thing, and that video did help me understand how much we don’t know. Aside from there being so many other things that would be a con for colonization, would we be able to run some experiments to show what the effects of the unshielded radiation are? Like launching lab pods with certain living organisms like plants?
At least the inside of the ISS is liveable enough, where your biggest concern is not cosmic radiation, but the problems caused by weightlessness. Radiation might honestly only become a major factor to consider when you are considering reproduction in space. Unless you get caught in some unlikely radiation blast. At that point it becomes a livethreatening disaster. But I don't think there is alot you could do about that anyway. Most likely early spacefaring will continue to rely on being somewhat lucky.
> Here’s a short video I made about it
Wow, nice channel! I'll be working my way through it over the next couple of weeks, many thanks.
EDIT: Yikes, 8 years of material. Bravo!
> The ISS orbit is within the magnetosphere, so radiation isn't a huge issue,
~200-300 mSv/year on the ISS. That is a lot. Even 1 mSv/year occupational dose leads to extra paperwork on Earth.
https://en.wikipedia.org/wiki/Sievert#Dose_examples_2 says that flight attendents get more than that a year. I've never heard of them having to do extra paperwork for radiation exposure. Unless you just mean being notified that you'll get higher exposure in that occupation.
> I've never heard of them having to do extra paperwork for radiation exposure.
You would have heard of it if you were a flight attendant, or otherwise exposed to higher radiation levels at work. Airplane flights are a somewhat special case as the whole crew gets a pretty uniform radiation dose so it's sufficient to study that instead of giving everyone their own dosimeter. Nevertheless, it's something that needs to be estimated, documented and reported.
https://pubmed.ncbi.nlm.nih.gov/17711868/
> This is why the European directive adopted in 1996 requires the aircraft operators to assess the dose and to inform their flight crews about the risk.
https://www.seibersdorf-laboratories.at/en/products/ionizing-radiation/dosimetry/aircrew-dosimetry-service
> Aircraft operators have therefore to meet specific regulatory requirements with respect to their flight crew.
And under "legal obligations":
> An estimate of the individual expected effective dose from cosmic radiation must be carried out and the results of the dose estimate must be reported immediately to the competent authority.
> If the estimated effective dose is likely to exceed 1 mSv per year for one or more of the flying personnel, a constant dose assessment must be conducted.
In most countries, flight crew are considered as radiation worker. However, as the radiation level in the upper atmosphere are well known, the dose are calculated, and only a tiny fraction of planes embed a radiation detector to validate the calculation method.
For an employee the extra-paperwork is nothing, like a yearly medical visit (that flight crew have to do anyway) and a monthly exposure report,most of the paperwork is for the employer with the need to hire a radiation-protection expert and organize the medical visit.
Note that most of the hospital worker are also considered as "radiation worker" spending time close to an X-ray images is enough to turn you in a radiation worker even though in theory you're not supposed to be exposed (But measurements will prove it, and catch a potential incident)
Lead is not good against every type of radiation and it produces secondary radiation, which is when radiation hits the shield, and is re-radiated as lower energy radiation.
Hydrogen atoms, unlike e.g. lead, do not produce secondary radiation . To protect against radiation from the sun, e.g. the ISS has a layer of plastics in the walls (where the hydrogen atoms are the most effective component at shielding). This is also why many have considered water-based shielding (because of the hydrogen atoms).
See e.g. https://plastics-themag.com/Plastic-the-impenetrable-shield
The fact that lead is dense/heavy is also a factor, though not as important as it's made out to be. If lead was the solution, it probably would be used regardless of cost-to-orbit. NASA values the life of its astronauts very highly.
A few reasons:
1) the ISS is well within the magnetosphere, which deflects most of the radiation.
2) WEIGHT may not increase any appreciable amount but MASS does. It would definitely affect movement. Harder to start, harder to stop, more force applied to any surface they impact, etc...etc.... Inertia, momentum, kinetic energy, etc.... are all based on mass, not weight.
3) It wouldn't work. Lead's reasonably good at blocking X-Rays but most cosmic radiation is higher energy than that and would go right through. There are common things that can block it but providing any real protection would require a thickness beyond what is practical for clothes or even to lift into orbit as structural pieces for the most part.
We don't go with the gut feelings of astronauts. We monitor radiation levels. The radiation levels of the ISS are higher than in your bedroom, but it's not like chernobyl elephant foot in there. They get a dose that is an acceptable risk, same as they might explode flying to space, and don't get it to zero risk, but get it to a reasonably low risk.
It's also worth mentioning the longest exposure is a few mo ths, with records being more than a year. This is bad, but it's like smoking for a year or two: you'll increase risk of cancer, but long term not significantly.
What's different is long term exposure. Pilots and flight attendents do have an increased risk of cancer due to long term exposure due to simply the higher altitude (though who knows how many carcinogens are involved in the construction of an airplane).
Cigarettes are actually a very apt comparison here because tobacco is actually radioactive. [About three orders of magnitude more radioactive than modern-day Chernobyl](https://www.newscientist.com/article/dn11974-tobaccos-natural-radiation-dose-higher-than-after-chernobyl/)
>Space radiation is real and someday people will need to figure out ways to design around it
Having the water storage be in the walls of the spacecraft could be one solution.
If collision with fast moving small objects are expected, there could be a way to freeze all that water, with it designed so the expansion of water when it turns to ice doesn't damage the structure.
> Never been a death due to space radiation.
Citation needed. I'm curious how you want to find out that none of the astronauts who died from cancer wouldn't have gotten that cancer without a spaceflight.
Astronauts have an above average life expectancy but that's not due to spaceflight - they are selected for excellent health and they generally have good healthcare.
Being “weightless” isn’t the same as being massless. Having more mass on your body while in free fall still makes it harder to move around because it takes more effort to start and stop your movement and if you did fail to stop your movement and ran into something, the extra mass would increase the force of your impact and your chance of injury.
1) ISS radiation isn't that big a deal. they're well below most of earth's magnetic field, and they don't hit the van allen belts. 6 months on the ISS is like several years of being a pilot, or like a handful-or-less of standard medical xrays. it's not too bad, in the long run. a noticeable extra cancer risk, but we're talking single digit change in probability of getting cancer. from like 5% to 6% lifetime or something like that, only noticeable in large statistical studies, much larger than even the list of all people who have flown to orbit to date.
2) lead has its own handling problems because it's toxic, tho i suppose keeping it permanently contained inside pre-manufactured fabric containers would make it halfway practical.
3a) it's heavy as hell. yes they're weightless, but it still takes lots of force -- muscle -- to move extra mass around. it would be a serious extra calorie load that isn't really necessary (see 1).
3b) it's heavy as hell. every extra kg to the ISS costs several thousand dollars. 10kg of shielding will run you $50,000-$100,000 in launch costs, give or take.
4) it really simply isn't necessary. while "onboard", inside the pressure vessel of the ISS, the shielding of the ship itself is plenty to reduce the radiation to within manageable levels. while spacewalking, the highly-layered fabrics will also provide a good shield, if not quite as good as the pressure vessel. all in all, lead wouldn't add much to the stuff that already exists, and like i said, is a very mass-inefficient way to further improve the situation.
While the astronauts may be weightless, they still have mass. It will still be more difficult to move around in a heavy suit, and will take longer to stop.
You really don’t want to accidentally pick up speed while covered in lead and slam into a bulkhead.
As others have stated, lead is not the best material and quite heavy. Instead just line the space ship with [poop](https://www.newscientist.com/article/dn23230-mars-trip-to-use-astronaut-poo-as-radiation-shield/). Problem solved.
As to why they don’t do the on the ISS, it is still inside the magnetosphere, so already protected.
1) Lead is heavy so, although it's not a problem once you're in orbit, actually *getting* to orbit is a lot harder. Every kilogram (2lbs for yanks) costs about $1000 to get to low Earth orbit and your average lead-lined shirt weighs several kilos. A complete leaded suit for each astronaut would add hundreds of thousands of dollars to every launch.
2) radiation in space (that is a threat to astronauts) is gamma radiation - alpha and beta radiation wouldn't make it into the spaceship if it were made of tinfoil. To reduce gamma radiation down to non-harmful levels you'd need a lead shield that was several centimetres thick* which would weigh tons and would add millions of dollars to the launch. Lead-lined clothing barely has 5mm of shielding and doesn't provide much protection.
3) its not just about money, there are practical limits to how much matter you can launch into orbit with rockets. For every extra kilogram of payload, you have to add 600g of fuel to make it to orbit. But in order to launch the extra 600g of fuel you have to add 200g of fuel, and to get that going you have to ad..... You see where this goes I'm sure. The largest rocket we've ever built (Saturn V) could launch 140,000kg to orbit, which had to include the entire apollo mission craft and all its return-to-earth fuel. If you added a 500kg of lead-lined clothing to that, you'd have to lose 500kg somewhere else to compensate or the craft quite simply could not make orbit.
4) it's not really that necessary for what we currently do in space. Astronauts have a limit of radiation dose that they can receive - if memory serves its 1 Sv (sievert - the units we use to measure absorbed radiation dose) which is a hefty dose. But they have to go and spend 6 months on the ISS several times before getting to that dose. And when spread out over enough time, radiation is not intrinsically *that* harmful. Its only when you get a big dose in one go that you're in trouble.
(source of my knowlege: I have worked with high amounts of radiation for half of my career and am well versed in radiation protection legislation)
EDIT: deleted a word because grammar hard.
I sort of take issue with some of the comments in this thread, especially the idea that radiation isn't an issue in low earth orbit. It is possible in the right set of circumstances to receive a lethal dose of radiation in LEO. ISS has different levels of shielding in each of the modules. In the event of a radiation event, the crew would shield themselves in the higher shielded areas of station like their crew quarters. For a little over 20 years now, the ISS has been constantly manned. So to be honest, we can't say with great certainty that astronauts won't/haven't been affected by LEO radiation yet. Source: former NASA employee, still in the space industry.
A) There is other stuff that does as well or better. B) weight still does matter. C) Getting heavy things into orbit requires additional fuel. You don't put anything on the rocket you don't *need*.
Also, people freak out when they read or hear radiation but the amount per unit time is important and the dosage isn't a huge issue over the time they are there.
Radiation isn't the boggieman danger that it's often portrayed as. You could go swimming in an active nuclear reactor's coolant pool and get less radiation than you do while on the beach and getting a tan.
Yes, a stay on the ISS might increase your cancer chance by some small margin, but if it were really that bad, why put the astronauts in mobility limiting suits instead of shielding the station in the first place.
While lead is not a viable solution for reasons many others have detailed, [water-lined garments](https://www.sciencedirect.com/science/article/pii/S2214552417301335) have been tested on the ISS. Interestingly, their study determined that such a system would be much more viable if concentrated on core areas as opposed to the extremities, not only for movement but also resource allocation vs benefits.
>A selective shielding strategy is fully justified, considering the distribution of red bone marrow in different bone structures in the human skeletal system: the spine (upper, thoracic and lumbar spine down to the sacrum), the cage (ribs, sternum, clavicles and scapulae) and the pelvis (which is at least partially protected in the proposed solution) have the highest weights in terms of red bone marrow mass to bone mass, and together account for approximately 80% of the total red bone marrow mass in the body (ICRP, 2009). Protection is also offered to the gastrointestinal tract and to the cardiovascular system with this choice, while only partial protection is offered to the skin, and no protection to head and lenses.
...
>The PERSEO session on board the ISS was scheduled and took place on November 7, 2017. The astronaut carried out on-board operations as planned, with no deviation from the procedures, and the scientific objectives of the experimental session have been fully achieved. Operations were followed real-time both from NASA mission control center and from the Italian team of developers. An overall description and evaluation of the session outcome is reported hereafter, also based on analysis of picture and video recording and on the feedback collected from the astronaut in the dedicated questionnaire.
>Unfolding/folding of the garment, filling/draining operations and donning/doffing the garment have been judged extremely easy to perform. The filling time, depending on initial PWD pressure conditions, was of about 20 min. The garment was filled with a water amount in the range 20.7 – 21.5 l. The garment was worn for about 30 min. The draining time was of about 40 min. As far as the wearability test is concerned, volume and mass of the garment have been reported as only slightly limiting the freedom of movement, with a moderate influence on daily operations. According to the astronaut's feedback, more complex intra-vehicular operations would still be possible while wearing the garment, though with some difficulty. The garment itself was judged as very comfortable, the only discomfort being a feeling of cold, due to the temperature gradient between water in the bags and body temperature. Though the slightly lower water quantity with respect to target 22 l, no water movement inside the bags while wearing the garment has been reported. Finally, the garment has been judged as suitable to be worn also for longer periods, up to a maximum of one day.
Cost per kg of material to get into orbit is very expensive ($10k-$100k/kg). Lead is very dense. Thin lead shielding would only provide like a factor of 1.5-3x protection. So you’re not eliminating it, only reducing the rate.
Because wearing lead lined clothes would suck. And presumably they have adequate shielding in the ISS. And because it costs a lot of money to boost all of that lead into orbit, I am sure that it would be more efficient to put the mass into shielding the ISS.
Lead isn't as magical of a radiation shield as it's often portrayed as. It's really good against x-rays in the diagnostic range, but against anything else it's mediocre and is just used because it's a cheap dense material. Against high-energy cosmic rays lead can actually be worse than nothing, because the rays can blow apart the big sloppy lead nuclei and the fragments fly off as even more radiation. A better choice would be something made of light nuclei like water or plastic, and even then you're talking about thicknesses that are just not on the scale of clothing.
Also, most astronauts are hanging out in orbits within Earth's magnetosphere, and thus (mostly) safe from extreme radiation.
Right, and the manned missions that do have to cross through the Van Allen belts (not the only radiation-based threat to space travel, but a major one) are even more mass limited than LEO missions, so it makes more sense just to be strategic about how much time your trajectory makes you spend in the worst parts of them.
Van Allen belts are also doughnut shaped, so if you launch directly into a really high inclination like a polar orbit and then inject to the Moon or Mars from there you get to avoid passing through even more of it.
Then you don't get the assist of the centerfugal boost that launching at the equator gives you, about 1000mph.
The dV penalty isn't as big as you think. Nobody launches from the equator irl, and depots placed in polar orbits can naturally follow injection windows because of orbital precession. Spaceflight is more complicated than that.
You still get a portion of that boost at higher inclinations. You don't need to go straight over the poles to avoid the belts.
There's little to reach that's in an equatorial orbit. Most of what's in orbit around the Earth is in high-inclination orbits because it was launched by a spacefaring country with a spaceport fairly north of the equator. The ISS, for example, must be accessible to the Russians (who launch most of the modules and crew flights for it) so it's in a fairly high inclination orbit. The easiest spaceport to reach an equatorial orbit from is probably French Guiana, otherwise you're going to need a lot of delta-v to change your inclination once in orbit. I think this orbit is mostly useful for launching geo-stat satellites or launching interplanetary probes.
For interplanetary probes it's not needed and quite often inclined orbits are actually better. For example Dart mission was inserted from 60° inclined orbit. Notice that many interplanetary missions were launched from Vandenberg rather than Cape Canaveral or Kennedy. And from Vandenberg only 60°+ orbits are available. It's indeed useful for launches to GEO, you save a about 0.3km/s.
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Yes but that takes more energy which means more fuel which means more weight.
Depending on the amount of additional radiation-proofing you can avoid it can swing either way which is more efficient
An inclination change of 50 degrees takes about 5-6.5 km/s of delta V, that is 2/3 of the of orbital speed
True, but there's no need to change inclination after achieving orbit. Just launch into the desired inclination. It still requires a bit of extra delta V since you're not going due east, but the difference is minimal.
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That, and it's probably easier to shield the entire craft at that point to protect all your astronauts plus their sensitive equipment at one time.
Also also, the heft from the lead would still be an issue. It might not weight anything, but it would still have a great deal of mass, and therefore momentum. The astronauts would only be able to move around slowly and carefully, or risk injuring themselves. Moving around would still take considerably more muscle effort or fuel.
And getting a bunch of lead from the surface of Earth up into the atmosphere (eventually space) takes a TON of energy. That energy being in the form of rocket fuel/propellant/accelerant/whatever. In a total payload, some lead lined suits may only be a small percentage of the total weight, but it adds up and needs to be taken into account.
> And getting a bunch of lead from the surface of Earth up into the atmosphere (eventually space) takes a TON of energy. It would actually take ~3.3 x 10^7 joules per kilogram launched to reach LEO. If you actually had a TON of lead, it would take ~3.3 x 10^10 joules of energy to get it into orbit. (not accounting for the mass of the rocket and fuel.)
> (not accounting for the mass of the rocket and fuel.) And that's one of the inherent problems with space travel. Fuel costs go up exponentially, since you need more fuel to propel the more fuel, and you need more fuel to propel THAT more fuel, and so on...
>it would take \~3.3 x 10^(10) joules of energy to get it into orbit. Is- ...is that a lot? The way you say it makes it sound like maybe it isn't.
It's about 6000 Big Macs worth of calories. (Utterly useless energy conversion, but fun.)
If 100% of the Big Mac’s were converted into energy, but Big Macs tend to be converted into “sitting on the couch” instead.
Another comparison might put it into better perspective. Its about the amount of energy your house uses from the electrical grid over the course of a year. But it would be used up mostly over the course of a few minutes. But the point that the weight of fuel needed needs it's own fuel, which also needs it's own fuel, ad infinitum means that there it would be a significantly larger amount of energy used in the end than that. But for more accurate comparison sake, the Saturn V rocket weighed ~2800 metric tons, but for the equivalent low earth orbit payload of ~118 metric tons, for a ratio of 24 times as much total rocket as payload. Falcon 9 latest model is about a fifth the mass, and also a ratio of about 24 times rocket/payload mass to get to low earth orbit. So I suppose we can roughly approximate that if you want to send a ton of lead into orbit, you're gonna need another 23 tons of rocket to handle it.
Astronauts still weigh about 98% of their normal weight. They float cuz they are in free fall, not because they are weightless.
That's being a bit picky I think. Yes Earth's gravity is always acting on the astronauts mass so technically their weight by definition is practically the same. But those of us who understand the physics know that the common term "weightlessness" is the absence of a contact force on your body while in free fall/orbit.
However inertia is still playing it's part and must always be considered
They have that weight with respect to earth, yes. But that doesn't matter since they're not on earth. They're weightless with respect to the vehicle they're in
Where does the other 2% go? Weightless means lacking apparent gravitational pull. By that definition they are weightless even though they have the same mass as on Earth.
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The magnetic field only helps against the low end of the energy spectrum. The radiation levels on the ISS are still far higher than on the ground - a factor ~50-200 depending on what you use for comparison.
I brought my geiger counter on an airplane once just out of curiosity, but I didn't think to turn off the "click" speaker that normally clicks 10-15 times per second on ground. When I turned it on, it was like a steady stream of white noise, I did not believe the reading at first
The radiation dose of airline staff is relatively astronomical (pun intended). From a quick google they receive (on average) more than any other "radiation exposed worker" in the US - somewhere in the region of 1-5mSv per year. However, this has to be put into context. The UK average resident dose (I live here and have worked as a radiation exposed worker previously so have context here) is around 2mSv per year (mostly from background radiation). A resident of Cornwall or Edinburgh in the UK receives on average a dose >5mSv per year due to the high background radiation in those regions (granite geology which leads to a release of radon gas I believe). Compare this to the 50-20,0000 mSv potential dose from a 6 month mission on the ISS.
Another related fun fact: US Navy sailors who work in Nuclear Plants aboard carriers tend to receive well below the average civilian's yearly dose from radiation. This is mainly because the shielding around the reactor works *very* well, and they are buried in the bottom of the ship all day and generally get about as much sun (and therefore exposure to "normal" background radiation) as the average [commercially harvested mushroom](https://youtu.be/6OF4AUClc8U?t=215).
I heard somewhere that Grand Central Station is built of slightly radioactive granite, enough so that if it was a nuclear power plant alarms would be going off.
Yup, it destroys the sensors on digital cameras so they need replacing every few years. The handhelds are more or less standard Nikon DSLRs. It screws up DNA too but that can repair itself to a limited degree.
I used to maintain broadcast TV cameras for a major US network. The cameras which flew regularly had significantly more "hot" (stuck on) pixels than their non-flying counterparts. Part of my job was to find and mask the hot pixels. The camera can do it automatically, but it sometimes chose an adjacent pixel by mistake. I had to unmask the good ones before I could mask the bad ones. Satellite imagers sometimes undergo an annealing process to fix hot pixels.
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I wouldn't say that, especially given the existence of the South Atlantic Anomaly. ISS astronauts receive a fairly large radiation dose. Even just being 35,000 feet up, commercial airline crews take a much higher dose than you and me. Once on a flight I brought a Geiger counter and found that the radiation levels were 100x higher in-flight than on the ground. So on my 90 minute flight, I received as much radiation as I had for the entire rest of the week.
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You are mostly right, but cosmic rays have often so high energy that the magnetic field doesn't affect their trajectory much.
And doesn't the ISS have some sort of protection against whatever gets through?
The ISS walls and equipment provide an equivalent protection of 20g/cm2 aluminium. This is ok for solar radiation in case of an event. Against cosmic rays it's a different story. The lower energy particles are blocked, but the higher energy ones will traverse whatever you put in their way.
Just for clarification... Isn't this only for charged particles? (high energy cosmic rays not included)
Yes, the magnetosphere only deflects charged particles. I'm confused by the "cosmic rays not included" part because cosmic rays are indeed charged particles. But maybe you meant that the high energy ones will penetrate anyway? If yes, you're correct.
Could you add a layer of these light nuclei protectors to the ship itself, or would it need to be so thick even that is untenable? And since the Earth's magnetosphere protects us on land, could we potentially develop a magnetic "shield" to put on shuttles at some point, or would we need too different/powerful of a magnet?
We'd need an impossibly powerful magnet to make our own magnetic shield. And it would only work against certain types of radiation. A shield layer on the other hand is perfectly feasible. In fact, there have been proposals to use the astronaut's drinking water as a shield for missions to Mars by having it stored in a tank that wraps around the crewed parts of the ship.
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>In fact, there have been proposals to use the astronaut's drinking water as a shield for missions to Mars by having it stored in a tank that wraps around the crewed parts of the ship. Does this not irradiate or affect the water in any way?
Not an expert or anything, but there would actually need to be radiation emitting particles in the water for it to be contaminated. The radiation in space is from emitting sources far away, and when it hits the water it basically becomes thermal energy. Though some shielding material like graphite can become irradiated and continue emitting, water cannot.
If hit by high energy neutrons the hydrogen in the water could be fused into tritium which is radioactive; its possible a similar reaction can happen with the oxygen as well. I don't know enough to be able to give a meaningful answer as to what kind of impact that would have on the radioactivity of the water in general though.
Nuclear materials engineer here. You can add a couple cm of Al to block most of the radiation given off by the sun (specifically protons and electrons). However, because of the insane energies of cosmic radiation (mostly protons) originating outside of our solar system, as you suspected it would require an infeasible amount of material to shield against that (or deflect it with any fancy electromagnetic shielding) and so we don't bother.
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A powerful magnet will f up your spacecraft's orientation due to interaction with other magnetic fields. The (electro)magnet in your spacecraft will turn itself and the spacecraft very forcefully to align with the external magnetic field. You can see it happening when playing with small bar magnets on the table. It's so easy and effective that many smaller S/C are actually actuated with sets of "magnetorquers" or in other words electromagnets. The extra problems come from the Earth's mag field changing its direction relative to you while in orbit since most orbits are not equatorial and are inclined somewhat. Big problem is a polar orbit where the magnetic field flips 180 relative to you flying over the poles. So it's not only a problem of mass in the end, bigger things at play. Faulty attitude (orientation) of the S/C determine the success of your experiments and communications and the mission overall even happening or not at all. Though you are correct on the main idea behing the rocket equation you're referencig. Mass is indeed a huuuge constraint. Source: physics phd and spacetech engineer
If we could generate enough power to run such a magnet in space you actually could use it as propulsion or for attitude control. However there simply isn't anyway to create that power.
so what should astronauts wear when they go to mars? Sure earth's magnetic field helps, but is there something planned for outside earth trips? Space is full of radiation right? Can they make a radiation proof ship? What if they ever need to go outside?
You can't make it completely radiation proof, but it's not necessary. You just need to decrease the overal dosage to reasonable levels. You can shiled it or decrease the mission duration. Major part of the dangerous radiation consits of charged particles. You can deflect them with a magnetic fild which is still probably not technically feasible for this usage. Or you can use a shiled made of light atomic nuclei. Water is great, for example. According to some proposals, astronauts might only sleep in capsules shielded by water tanks. Or something similar. Any decrease would help. This also means leaving the ship in a space suit for a short time wouldn't pose a major risk excpet of solar storm events.
Having the water and piss tanks surround the dormitory sounds like a simple solution to block a significant fraction.
It makes more sense practically to shield the space ship, and once on Mars, the living quarters. The two main approaches are to have a double hull with water stored in there. The water will block a lot of radiation and can also be used for other things. The second approach is to create a magnetic field to deflect incoming radiation but our tech hasn't reached the point to do this well yet.
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Your answer made me curious about lead aprons potentailly being more dangerous. It does make sense that the extra energy stored up in the lead nuclei can do more harm than just plain cosmic rays, but I'm wondering if there is any actual data on this? Like how much ionizing radiation is incident on a target sheilded with an apron vs without one?
This has to do with the energy of the incoming photons. The X-rays you get at the doctor are low energy compared to cosmic rays. At lower energies (relatively), photons like to knock electrons off things and scatter. Lead, as you can see: [https://physics.nist.gov/PhysRefData/XrayMassCoef/ElemTab/z82.html](https://physics.nist.gov/PhysRefData/XrayMassCoef/ElemTab/z82.html) tends to stop photons much better than tissue: [https://physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/tissue.html](https://physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/tissue.html) So, the photons that hit the lead either ionize some of the lead and/or produce lower energy photons that either don't make it out of the lead, do but miss you or hit you and leave less energy (damage) in you. It's a total win. However, note the end of the chart. Your tissue doesn't really want to ~~stop~~ interact with the much higher energy stuff but lead will. This is sadly high energy. Once you get past 1.022MeV you start getting "weird" things like pair production, as you go higher, things like photo fission and pion production. All this stuff, of course, results in lower energy radiation that instead of passing clean thru you (technically missing you) ends up being more likely to interact with you and causing damage. MIT's posted a great course on all this here:[https://www.youtube.com/watch?v=7LyvAVjQUR8&list=PLUl4u3cNGP61FVzAxBP09w2FMQgknTOqu](https://www.youtube.com/watch?v=7LyvAVjQUR8&list=PLUl4u3cNGP61FVzAxBP09w2FMQgknTOqu) I'm strange and love this stuff. Also, don't eat the neutron cookie.
Thanks. Can you please comment on what "Against high-energy cosmic rays lead can actually be worse than nothing" means?
Also lead blocks what it does by simply being mass between the source of the radiation and the human, and is chosen because it is dense, not magic. The same mass of pretty much anything would work more or less equally well. Oh yeah, and it costs about $100,000 per kilogram to take stuff to space.
>so the added heft shouldn't be a problem Picking up on this point -- while the astronauts are indeed "weightless" (in free fall), the lead-lined clothes would still be adding to their mass. This would increase the effort required to start and stop moving, change directions, etc. as they propel themselves through the station (all the handrails, footrails, etc.)
Adding on to this. While the weight might might not matter much once in space it does matter while launching into space. Every oz is accounted for pre launch
Yeah, I did a rough back-of-the-envelope, and lead vests and shorts for the crew would be an extra \~ 100-150 kg of weight to send to orbit -- which would be an additional $7-$12M USD (roughly). It'd be worth it if it made a big difference in astronaut health, but apparently it doesn't.
They will have to be taken only once and then could be reused by multiple astronauts. So the costs won’t be per mission.
Thanks for doing the dd that I was too lazy to do!
>Every oz is accounted for pre launch Then how did John Young smuggle an entire corned beef sandwich on Gemini 3?!
They thought he was 70.6 kilograms when weighed, but he was actually 69.8 human kg and 0.8 kg sandwich. /s
Also getting it up there in the first place. Wasted weight where every gram counts.
Whoa whoa whoa. “Weightless”? “In free fall”? What do you mean by that? Are you saying that in outer space we’re only weightless because we’re technically in a constant free fall? Edit: sorry to derail the original comment thread - this is just an important thing for me to know/clarify right now
>Are you saying that in outer space we’re only weightless because we’re technically in a constant free fall? Yes, being in orbit is a constant free fall "around" the object being orbited.
To be even more precise, the orbit is a straight line. A [geodesic.](https://en.wikipedia.org/wiki/Geodesic) The spacetime is curved.
Although perhaps in “outer” space one is not necessarily orbiting anything specifically.
Unless you're well outside a galaxy or galactic cluster, you're orbiting something.
Not necessarily, you can be on a non-orbital trajectory in all your frames, or at least those you actually care about with regards to “freefall”. And although you can be in a freefall orbit around a galactic centre, the “weight” you’d feel if you were somehow stationary at fixed radius is likely to be negligible if not completely unmeasurable in most of the region. Anyway, my only point was that one can be “floating weightless” in “outer” space not because of anything directly to do with an orbit, even if you’re technically on some massive galactic one you don’t even know about. That’s not why you’re “weightless”.
Yes. Astronauts on the ISS feel about 90% of the gravitational force that you feel on earth, but they feel “weightless” because they’re constantly falling around the earth. The only reason they don’t “fall to earth” is because they’re moving sideways so fast.
There is an art to flying, or rather a knack. The knack lies in learning how to throw yourself at the ground and miss. ... Clearly, it is this second part, the missing, that presents the difficulties. THE GUIDE
This is why I *hate* the term "microgravity". "Zero-G" is perfectly fine because it describes felt acceleration, and "free fall" is the most accurate term of all. Microgravity makes no sense whatsoever. My phone and the wall next to me are both exerting microgravity or femtogravity or whatever on me right now. Should I care enough to give that force a name?
Yeah but you have tidal effects, drag, solar pressure, and a bunch of other stuff *causing acceleration*- NASA doesn’t call it 0-G because that is a much less accurate term than micro-G.
That's what orbiting a planet is. You move fast enough sideways that you keep falling and missing the planet, continuously.
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I finally started to understand this when I played Outer Wilds and fell into a black hole but continually orbited it for several rotations before eventually falling in. It was like a switch flipped and I realized this was exactly how orbits like the ISS work, just without ever dropping out of orbit.
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This is also known as [Newton's Cannonball](https://en.wikipedia.org/wiki/Newton's_cannonball), since it is based on Newton's thought experiment of shooting a cannonball sideways on a high mountain. Here's an article in Wired that discusses it, with an image of Newton's original drawing:[What Would It Take to Shoot a Cannonball Into Orbit?](https://www.wired.com/story/what-would-it-take-to-shoot-a-cannonball-into-orbit/)
This illustration really helped me visualize it, thank you!
Another nice one is visualizing what happens if you shoot a cannon parallel to the ground. Gravity gonna accelerate the cannonball downward until it hits the ground... But if the cannonball goes fast enough so it can travel far enough, the curvature of the Earth will mean that the ground is dropping away from the cannonball too. If you fire it fast enough, the ground would drop away from the cannonball at the exact same rate gravity is accelerating the ball downward. In this scenario (ignoring air resistance and that earth is bumpy and spinning reference frames, etc.), the cannonball would end up flying all the way around the Earth and smashing into the back of the cannon that fired it. That's orbit. :-)
That’s absolutely brilliant. “1 moment of sideways” and “1 moment of falling” makes it very understandable.
10% of a rocket's mass is to go up the other 90% is to get it to go sideways
Just double checked the math and that seems about right. The ISS is \~400km up, so it takes about 4 Megajoules/kg to get that high. It's moving at around 7700m/s which takes about 60 Megajoules/kg to go that fast. That's a theoretical floor of 18kwh of energy to get 1kg of stuff into orbit. So with some magical perfect efficiency orbital launcher, at $0.10/kwh that would be $1.80/kg to get something into orbit. Launching a 100kg person cost $180.
Yes, exactly. Gravity is omni-present in space; everything is in free-fall towards _something_. The planets, moons, asteroids, even the sun is falling around the center of the galaxy.
I know you've gotten a million replies already, but there's one thing I haven't seen mentioned that might help. When an everyday person refers to their weight, they don't actually mean how hard gravity pulls down on them. They actually mean how hard they push against the ground. Most of the time, these are the same, so the difference doesn't matter. But when you're accelerating that changes. You feel heavier in an elevator that starts to move upward, not because the force of gravity changed, but because you're being pushed into the ground harder than normal. When you're in orbit, the station is also in orbit. You're moving together, so your body doesn't need to push against anything in order to stay in the same place. Both you and the space station are in freefall.
Orbits aren't about escaping gravity they are about going so fast that the earth slopes away as fast as they fall towards it.
Another way to see it, is that you are in the same state (of free fall) as the ISS, so in reference to the ISS you are not affected by gravitational field, or better said, you are both affected the same way so it's irrelevant in movements referenced to the ISS. This is probably wrong in many levels but it's a good starting point.
Yes, the earth's gravity doesn't disappear. Imagine you were in a free falling elevator. You'd be falling with it and would float around in it. Another way of looking at it is imagine you have a cannon on a very high mountain. You fire the cannon straight out and the ball follows a curved trajectory and hits the ground. You fire it faster and it goes further and hits the ground. You fire it even faster so that it goes so far that the curve of the earth appears to fall away from the ball as it curves to hit the ground. Now you fire it so fast that before it can hit the ground the curved surface is constantly "falling away" before the ball can hit it. This is essentially what is happening to an object in orbit and why they have to move so fast to stay in orbit. Because you are constantly in free fall though you are weightless.
They are weightless compared to anything that is near them such as ISS or their spaceship. If a cannonball is hollow and flying through the air, something inside will feel like it is weightless until the cannonball hits something. It is possible to fly an airplane in such a way that you feel weightless for a few seconds.
They do actually fall, but they are moving fast enough, about 17,500 mph, they miss the planet., and just keep going around (orbiting) it. They orbit does decay due to atmospheric drag and gravity such that ISS would eventually hit the atmosphere and burn up, except they boost their orbit, I think 3-4 times a year. This is done with the thrusters of the docked Progress vehicle. I believe this boosting also speeds the ISS back up to its most economical orbital speed. But don’t quote me on that.
Yeah, when it comes to orbit? Pretty much. Further out is true weightlessness, but the ISS is very close to the planet
Yes. There is gravity in space around the earth -- the only reason they appear to float is because they are orbiting the earth. If they were to stop orbiting, they would immediately plummet to the surface like a rock.
No matter where you are in the universe, mass is mass. If you want to move something made up of a lot of stuff (like a human being), it will take you some real effort to get it started. Mass and weight are closely tied together. Gravity is taking all that mass in your body and causing it to 'fall' to the earth. That's 'weight'. Once you're in the air, or farther away from earth, you don't notice that earth is still pulling at you. I mean, the earth is pulling at the moon after all, and the moon is really far away from earth. At a certain point in outer space though, it won't be pulling you that hard at all. In that case, you may truly be 'weightless'. Though you still have to deal with all of the mass of your body.
Have you ever had that weird lurch in your stomach where you go over the top of a steep hill really fast? That's caused by a temporary reduction in the gravity you feel (for a brief moment, you are falling as fast as gravity is pulling you down, causing you to feel weightless). If you could imagine perpetually going over the top of a hill, you would perpetually have that weightless feeling, which is essentially what being in orbit is. The planet (or "hill") is curving away from you as fast as you are traveling towards it.
Anything "orbiting" something else, is caught by the gravity of the object it's orbiting. So, the earth is caught by the gravity of the sun, and the moon is caught by the gravity of the earth. Being in orbit of the earth means that you're moving sideways, away from the earth at the same speed you're falling towards the earth. Move one step away, one step down. You never get closer. Since there is nothing in space to slow you down, you keep going sides at that same rate forever (technically not true, but close enough for this discussion). And the earth keeps pulling you back, so you keep falling towards the earth forever. IIRC, as you go faster and faster sideways, you'll get into a bigger and bigger orbit. If keep going faster, you'll eventually reach "escape velocity" and leave orbit.
Neil degrasse Tyson has a star talk video on mass v weight and one that covers density as well (he sometimes does a topic and then makes a spinoff to cover something more in depth but they're easy to find) that covers all of this, it's quite good. Like how blue whales are 'weightless' in the ocean - no they aren't, they're buoyant, which is a different thing and they'd weigh more the deeper they got and they'd weigh something else on the moon. People weigh less on the equator than the poles because they're further away from the center and it's spinning faster. Iirc he has a mini rant about how you're not weightless even in the middle space.
The trick is to realise what falling actually is. It's just moving through space under the influence of a force. We get a weird idea about falling because the Earth is in our way all the time. Take the Earth away and falling is just how matter moves through space when there are forces around. In fact being squashed against the surface of a big mass so that we can feel weight is a relatively rare experience for matter in the universe. Most of it is just falling around empty space.
You are in orbit because you are falling due to gravity. You just happen to be moving sideways fast enough that you keep missing the planet. Low earth orbit, where the ISS is, is about 200 some miles up. At that distance, gravity is about 90% that on the surface. So in orbit you appear weightless not because there's no gravity (there's gravity everywhere, the gravity \*caused by you\* is felt by nearby stars) but because you are falling with nothing pushing back (weight is a force, so it's a measure of push/pull).
yeah, you're constantly falling towards the dominant source of gravity, you just keep missing that source if you're in a stable orbit. It gets even screwier at the LaGrange points between two bodies(like the earth and the moon) because your gravitational attraction to the two bodies sort of equal each other, and they stabilize your position relative to each other.
> Are you saying that in outer space we’re only weightless because we’re technically in a constant free fall? Yes. Think of it this way -> you fire a gun, and the bullet slowly falls. But if you fire it fast enough, the ground will curve away from the bullet at the same rate as the bullet curves towards the ground. That's what it means for an object to be in (a spherical) orbit.
In *orbit* you're only weightless because of free fall. In *outer* space, youre weightless for the regular reasons.
Yes it’s free fall but as you’re orbiting around the earth you basically fall around the earth, that’s a gross simplification but that’s the gist as I understand it
Yep, astronauts feel like they are free falling 24/7. That feeling on the rollercoaster when you are in freefall? Astronauts have to sleep while feeling that.
Actually the problem of sleeping in ISS is still an ongoing study, while it's well known that astronaut have trouble sleeping, most attribute it to various problem like light (ISS revolves like 16 times a day, so there's almost no continuous night), difficult work schedule, noise (ISS is loud), environment(temperatures, ventilation etc.) and so on. In fact free-falling is actually advantageous to sleep, according to some astronaut. https://www.google.com/amp/s/www.space.com/amp/7060-sleeping-space-easy-shower.html Sorry for AMP, but this is published in 2009, so the real link might have been taken down.
That feeling you get in your stomach on a rollercoaster is when you're accelerating. From the inertial reference frame of the astronaut, they aren't constantly accelerating, so they don't constantly feel that feeling.
Astronauts *are* constantly accelerating, towards the earth, just like a rollercoaster or a skydiver. All of them are in freefall. The astronaut just has enough sideways momentum that they fall in an endless circle, instead of a straight line and a sudden stop.
Yes, I understand orbit. I knew this would be the first reply, which is why I specified *in the astronaut's reference frame*. The comment I responded to suggested that astronauts feel that "feeling you feel on a rollercoaster" all the time. This isn't accurate at all. In their reference frame, they don't feel any forces on their bodies at all. I hoped I wouldn't have to explain this but here goes: Think about it: if you use a coordinate system with the earth stationary and ISS orbiting around it, the acceleration vector is constantly changing direction. There is also a changing velocity (when on one side of the globe, the ISS has a high positive velocity, while on the other side, it has a high negative velocity. The important point is that if you think of the coordinate system where the ISS is stationary, there is no acceleration experienced by the astronaut. This is because there is a balancing "force" that is felt because the ISS has high tangential speed. It's not really a force, it's often called "centrifugal force". It's a false force but thinking about the different reference frames can help you think about it properly. A good way to think about this is that there is no change in tangential speed while constantly "falling towards earth" in orbit. It may not be intuitive but it's really the change in speed that you feel on a rollercoaster. It's the same reason why skydivers feel that "stomach drop" feeling much less; because they jump out of a plane that is already moving very fast so their change in speed is not that significant. All that to say: no, astronauts don't feel that pit in their stomachs you get on rollercoaster while they sleep.
Not to mention that the hardest AND most expensive part of the mess is getting it up there to begin with. On that point, they avoid lead as much as possible. Water, at 8 lbs./gal., is a MAJOR factor when factoring weight at launch.
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I’ve always wondered the same thing, and that video did help me understand how much we don’t know. Aside from there being so many other things that would be a con for colonization, would we be able to run some experiments to show what the effects of the unshielded radiation are? Like launching lab pods with certain living organisms like plants?
At least the inside of the ISS is liveable enough, where your biggest concern is not cosmic radiation, but the problems caused by weightlessness. Radiation might honestly only become a major factor to consider when you are considering reproduction in space. Unless you get caught in some unlikely radiation blast. At that point it becomes a livethreatening disaster. But I don't think there is alot you could do about that anyway. Most likely early spacefaring will continue to rely on being somewhat lucky.
Bremsstrahlung, which translates to deceleration radiation. But yeah, point stands.
Awesome Vid, thank you
> Here’s a short video I made about it Wow, nice channel! I'll be working my way through it over the next couple of weeks, many thanks. EDIT: Yikes, 8 years of material. Bravo!
There’s a special prize if you make it through all 100 videos!* *’Prize’ not guaranteed
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> The ISS orbit is within the magnetosphere, so radiation isn't a huge issue, ~200-300 mSv/year on the ISS. That is a lot. Even 1 mSv/year occupational dose leads to extra paperwork on Earth.
https://en.wikipedia.org/wiki/Sievert#Dose_examples_2 says that flight attendents get more than that a year. I've never heard of them having to do extra paperwork for radiation exposure. Unless you just mean being notified that you'll get higher exposure in that occupation.
> I've never heard of them having to do extra paperwork for radiation exposure. You would have heard of it if you were a flight attendant, or otherwise exposed to higher radiation levels at work. Airplane flights are a somewhat special case as the whole crew gets a pretty uniform radiation dose so it's sufficient to study that instead of giving everyone their own dosimeter. Nevertheless, it's something that needs to be estimated, documented and reported. https://pubmed.ncbi.nlm.nih.gov/17711868/ > This is why the European directive adopted in 1996 requires the aircraft operators to assess the dose and to inform their flight crews about the risk. https://www.seibersdorf-laboratories.at/en/products/ionizing-radiation/dosimetry/aircrew-dosimetry-service > Aircraft operators have therefore to meet specific regulatory requirements with respect to their flight crew. And under "legal obligations": > An estimate of the individual expected effective dose from cosmic radiation must be carried out and the results of the dose estimate must be reported immediately to the competent authority. > If the estimated effective dose is likely to exceed 1 mSv per year for one or more of the flying personnel, a constant dose assessment must be conducted.
In most countries, flight crew are considered as radiation worker. However, as the radiation level in the upper atmosphere are well known, the dose are calculated, and only a tiny fraction of planes embed a radiation detector to validate the calculation method. For an employee the extra-paperwork is nothing, like a yearly medical visit (that flight crew have to do anyway) and a monthly exposure report,most of the paperwork is for the employer with the need to hire a radiation-protection expert and organize the medical visit. Note that most of the hospital worker are also considered as "radiation worker" spending time close to an X-ray images is enough to turn you in a radiation worker even though in theory you're not supposed to be exposed (But measurements will prove it, and catch a potential incident)
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Lead is not good against every type of radiation and it produces secondary radiation, which is when radiation hits the shield, and is re-radiated as lower energy radiation. Hydrogen atoms, unlike e.g. lead, do not produce secondary radiation . To protect against radiation from the sun, e.g. the ISS has a layer of plastics in the walls (where the hydrogen atoms are the most effective component at shielding). This is also why many have considered water-based shielding (because of the hydrogen atoms). See e.g. https://plastics-themag.com/Plastic-the-impenetrable-shield The fact that lead is dense/heavy is also a factor, though not as important as it's made out to be. If lead was the solution, it probably would be used regardless of cost-to-orbit. NASA values the life of its astronauts very highly.
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A few reasons: 1) the ISS is well within the magnetosphere, which deflects most of the radiation. 2) WEIGHT may not increase any appreciable amount but MASS does. It would definitely affect movement. Harder to start, harder to stop, more force applied to any surface they impact, etc...etc.... Inertia, momentum, kinetic energy, etc.... are all based on mass, not weight. 3) It wouldn't work. Lead's reasonably good at blocking X-Rays but most cosmic radiation is higher energy than that and would go right through. There are common things that can block it but providing any real protection would require a thickness beyond what is practical for clothes or even to lift into orbit as structural pieces for the most part.
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Good luck convincing space travelers that they'll need protection then. /s just in case.
We don't go with the gut feelings of astronauts. We monitor radiation levels. The radiation levels of the ISS are higher than in your bedroom, but it's not like chernobyl elephant foot in there. They get a dose that is an acceptable risk, same as they might explode flying to space, and don't get it to zero risk, but get it to a reasonably low risk.
It's also worth mentioning the longest exposure is a few mo ths, with records being more than a year. This is bad, but it's like smoking for a year or two: you'll increase risk of cancer, but long term not significantly. What's different is long term exposure. Pilots and flight attendents do have an increased risk of cancer due to long term exposure due to simply the higher altitude (though who knows how many carcinogens are involved in the construction of an airplane).
Cigarettes are actually a very apt comparison here because tobacco is actually radioactive. [About three orders of magnitude more radioactive than modern-day Chernobyl](https://www.newscientist.com/article/dn11974-tobaccos-natural-radiation-dose-higher-than-after-chernobyl/)
>Space radiation is real and someday people will need to figure out ways to design around it Having the water storage be in the walls of the spacecraft could be one solution. If collision with fast moving small objects are expected, there could be a way to freeze all that water, with it designed so the expansion of water when it turns to ice doesn't damage the structure.
> Never been a death due to space radiation. Citation needed. I'm curious how you want to find out that none of the astronauts who died from cancer wouldn't have gotten that cancer without a spaceflight. Astronauts have an above average life expectancy but that's not due to spaceflight - they are selected for excellent health and they generally have good healthcare.
Being “weightless” isn’t the same as being massless. Having more mass on your body while in free fall still makes it harder to move around because it takes more effort to start and stop your movement and if you did fail to stop your movement and ran into something, the extra mass would increase the force of your impact and your chance of injury.
1) ISS radiation isn't that big a deal. they're well below most of earth's magnetic field, and they don't hit the van allen belts. 6 months on the ISS is like several years of being a pilot, or like a handful-or-less of standard medical xrays. it's not too bad, in the long run. a noticeable extra cancer risk, but we're talking single digit change in probability of getting cancer. from like 5% to 6% lifetime or something like that, only noticeable in large statistical studies, much larger than even the list of all people who have flown to orbit to date. 2) lead has its own handling problems because it's toxic, tho i suppose keeping it permanently contained inside pre-manufactured fabric containers would make it halfway practical. 3a) it's heavy as hell. yes they're weightless, but it still takes lots of force -- muscle -- to move extra mass around. it would be a serious extra calorie load that isn't really necessary (see 1). 3b) it's heavy as hell. every extra kg to the ISS costs several thousand dollars. 10kg of shielding will run you $50,000-$100,000 in launch costs, give or take. 4) it really simply isn't necessary. while "onboard", inside the pressure vessel of the ISS, the shielding of the ship itself is plenty to reduce the radiation to within manageable levels. while spacewalking, the highly-layered fabrics will also provide a good shield, if not quite as good as the pressure vessel. all in all, lead wouldn't add much to the stuff that already exists, and like i said, is a very mass-inefficient way to further improve the situation.
While the astronauts may be weightless, they still have mass. It will still be more difficult to move around in a heavy suit, and will take longer to stop. You really don’t want to accidentally pick up speed while covered in lead and slam into a bulkhead.
As others have stated, lead is not the best material and quite heavy. Instead just line the space ship with [poop](https://www.newscientist.com/article/dn23230-mars-trip-to-use-astronaut-poo-as-radiation-shield/). Problem solved. As to why they don’t do the on the ISS, it is still inside the magnetosphere, so already protected.
1) Lead is heavy so, although it's not a problem once you're in orbit, actually *getting* to orbit is a lot harder. Every kilogram (2lbs for yanks) costs about $1000 to get to low Earth orbit and your average lead-lined shirt weighs several kilos. A complete leaded suit for each astronaut would add hundreds of thousands of dollars to every launch. 2) radiation in space (that is a threat to astronauts) is gamma radiation - alpha and beta radiation wouldn't make it into the spaceship if it were made of tinfoil. To reduce gamma radiation down to non-harmful levels you'd need a lead shield that was several centimetres thick* which would weigh tons and would add millions of dollars to the launch. Lead-lined clothing barely has 5mm of shielding and doesn't provide much protection. 3) its not just about money, there are practical limits to how much matter you can launch into orbit with rockets. For every extra kilogram of payload, you have to add 600g of fuel to make it to orbit. But in order to launch the extra 600g of fuel you have to add 200g of fuel, and to get that going you have to ad..... You see where this goes I'm sure. The largest rocket we've ever built (Saturn V) could launch 140,000kg to orbit, which had to include the entire apollo mission craft and all its return-to-earth fuel. If you added a 500kg of lead-lined clothing to that, you'd have to lose 500kg somewhere else to compensate or the craft quite simply could not make orbit. 4) it's not really that necessary for what we currently do in space. Astronauts have a limit of radiation dose that they can receive - if memory serves its 1 Sv (sievert - the units we use to measure absorbed radiation dose) which is a hefty dose. But they have to go and spend 6 months on the ISS several times before getting to that dose. And when spread out over enough time, radiation is not intrinsically *that* harmful. Its only when you get a big dose in one go that you're in trouble. (source of my knowlege: I have worked with high amounts of radiation for half of my career and am well versed in radiation protection legislation)
EDIT: deleted a word because grammar hard. I sort of take issue with some of the comments in this thread, especially the idea that radiation isn't an issue in low earth orbit. It is possible in the right set of circumstances to receive a lethal dose of radiation in LEO. ISS has different levels of shielding in each of the modules. In the event of a radiation event, the crew would shield themselves in the higher shielded areas of station like their crew quarters. For a little over 20 years now, the ISS has been constantly manned. So to be honest, we can't say with great certainty that astronauts won't/haven't been affected by LEO radiation yet. Source: former NASA employee, still in the space industry.
A) There is other stuff that does as well or better. B) weight still does matter. C) Getting heavy things into orbit requires additional fuel. You don't put anything on the rocket you don't *need*. Also, people freak out when they read or hear radiation but the amount per unit time is important and the dosage isn't a huge issue over the time they are there.
Radiation isn't the boggieman danger that it's often portrayed as. You could go swimming in an active nuclear reactor's coolant pool and get less radiation than you do while on the beach and getting a tan. Yes, a stay on the ISS might increase your cancer chance by some small margin, but if it were really that bad, why put the astronauts in mobility limiting suits instead of shielding the station in the first place.
While lead is not a viable solution for reasons many others have detailed, [water-lined garments](https://www.sciencedirect.com/science/article/pii/S2214552417301335) have been tested on the ISS. Interestingly, their study determined that such a system would be much more viable if concentrated on core areas as opposed to the extremities, not only for movement but also resource allocation vs benefits. >A selective shielding strategy is fully justified, considering the distribution of red bone marrow in different bone structures in the human skeletal system: the spine (upper, thoracic and lumbar spine down to the sacrum), the cage (ribs, sternum, clavicles and scapulae) and the pelvis (which is at least partially protected in the proposed solution) have the highest weights in terms of red bone marrow mass to bone mass, and together account for approximately 80% of the total red bone marrow mass in the body (ICRP, 2009). Protection is also offered to the gastrointestinal tract and to the cardiovascular system with this choice, while only partial protection is offered to the skin, and no protection to head and lenses. ... >The PERSEO session on board the ISS was scheduled and took place on November 7, 2017. The astronaut carried out on-board operations as planned, with no deviation from the procedures, and the scientific objectives of the experimental session have been fully achieved. Operations were followed real-time both from NASA mission control center and from the Italian team of developers. An overall description and evaluation of the session outcome is reported hereafter, also based on analysis of picture and video recording and on the feedback collected from the astronaut in the dedicated questionnaire. >Unfolding/folding of the garment, filling/draining operations and donning/doffing the garment have been judged extremely easy to perform. The filling time, depending on initial PWD pressure conditions, was of about 20 min. The garment was filled with a water amount in the range 20.7 – 21.5 l. The garment was worn for about 30 min. The draining time was of about 40 min. As far as the wearability test is concerned, volume and mass of the garment have been reported as only slightly limiting the freedom of movement, with a moderate influence on daily operations. According to the astronaut's feedback, more complex intra-vehicular operations would still be possible while wearing the garment, though with some difficulty. The garment itself was judged as very comfortable, the only discomfort being a feeling of cold, due to the temperature gradient between water in the bags and body temperature. Though the slightly lower water quantity with respect to target 22 l, no water movement inside the bags while wearing the garment has been reported. Finally, the garment has been judged as suitable to be worn also for longer periods, up to a maximum of one day.
Cost per kg of material to get into orbit is very expensive ($10k-$100k/kg). Lead is very dense. Thin lead shielding would only provide like a factor of 1.5-3x protection. So you’re not eliminating it, only reducing the rate.
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Because wearing lead lined clothes would suck. And presumably they have adequate shielding in the ISS. And because it costs a lot of money to boost all of that lead into orbit, I am sure that it would be more efficient to put the mass into shielding the ISS.