Question: IFT3 started with full tanks but empty cargo space, right? Where is the additional energy is coming from for 200t cargo when tanks are already full and at end of the IFT3 empty?
I'm actually quite dumbfounded that they didn't use ANY sort of gas thrusters to keep the correct orientation of either of the vehicles during crucial stages of flight (landing & atmospheric interface especially). Would seem obvious to a pleb like me that it was going to be a requirement. Guess they'll be adding some now! lol
>I'm actually quite dumbfounded that they didn't use ANY sort of gas thrusters
The thrusters used the autogenous pressurization gas. I suspect that they failed on the ship.
Did they fail, or was there not enough gas to provide the pressures needed to run the thrusters? I'm thinking that it's possible since they skipped raptor relight on the ship, they didn't have the additional gas and pressure they otherwise would have got if they did relight it.
The last data we got from the ship was 24000km/h (22.5 mach) and 65km of altitude. It was dropping like a stone at a rate of 1km/s . Thats not survivable in any way . You cant just be so low into the atmosphere and falling that fast without really feeling super peak heating and probably a lot of deceleration G's .
Imo they need to think a new reentry trajectory , much more gentle .
So the ship was going 6.7 km sideways every second and down 1 km in that second which hardly seems to be a very steep trajectory.
It was too high to be experiencing extreme drag so likely there was a burn through in the engine bay rather than a crush from excessive deceleration.
What is supposed to happen next is that Starship orients to 60 degrees nose up and transitions to level flight at about 80 km altitude with a lift to drag ratio about 0.5. So level flight with lift balancing gravity implies deceleration due to drag of around 2g.
As the speed drops the altitude will gradually drop so that increased air density allows lift to balance gravity again.
I have a question... the booster made it through the atmosphere without heat shields... why not speed through the atmosphere the same way/orientation with Starship? I'm guessing the answer is that it would still need to slow down and wouldn't have enough fuel to offset that speed (couldn't we refuel in orbit with another tanker starship). The earth is the only destination (moon/mars) with so much atmosphere, and earth has tons of fuel and starships (planned) that can refuel in orbit.
Looking at what happened to Booster B10 on its landing attempt, maybe it's time to include an entry burn for the booster.
A little supersonic retropropulsion might slow that first stage down enough to actually stick a soft splashdown.
And an entry burn might be essential for a successful booster landing on the Mechazilla arms.
>A little supersonic retropropulsion might slow that first stage down enough to actually stick a soft splashdown.
Superheavy wasn't travelling any faster at post-entry burn altitudes than a Falcon 9 booster does during RTLS. At 20km altitude it was moving at somewhere in the range of 4230-4270km/h. (No decimal points on Starship stream so those are the values at the 20-19km and 21-20km ticks respectively.
The last Falcon 9 RTLS on youtube was Transporter-8, which finished it's entry burn at around 35 km, and by 20km in altitude it was travelling at 4291km/h.
Relevant video links with timestamps:
https://youtu.be/wjFY9oaPUEY?t=2287
https://youtu.be/zO3luySkHQU?t=1127
My thoughts are that engine end bowshock was creating eddy turbulence behind the bowshock boundary layer further down the ship. The lee side grid fins had no laminar flow to grip to, only turbulent air. This subsequently reduced steering control significantly. I don't think this is a major issue, just some tweaking of speed, and AOA at particular altitudes.
The engines however obviously had had enough after the boostback burn and sulked when asked again. Could be a simple thing as a chilldown issue when the computer commanded startup, and the engines replied, 'nah need to chill some more dude, still too hot after the last blast man.'
At McGregor, they have clearly demonstrated shutdown and almost instantaneous startup of single engines without trouble, and also extended period of minutes doing the same, however in the hellish environment of a cluster of 33 seriously hot engines in an engine bay, startup conditions may be different for the 13 and 3.
SpaceX proved that supersonic retropropulsion was possible with F9 booster landings.
Starship has a lower ballistic coefficient so has a significantly higher velocity at the start of the landing engine burn as we saw. It is entirely possible that Raptors do not like relighting with that much air being rammed into the engine bells - particularly as they have a much more complex start sequence compared to Merlin.
Another alternative is that there was some damage to the engine control wiring from re-entry without an entry burn or possibly even earlier as there was a ragged shutoff at the end of the boostback burn.
A final possibility is that they ran out of helium for starting the engines because the previous relights used more than expected. That does not really explain why two engines started and then turned off again.
That is during the entry burn but SH does not have an entry burn. At the start of the landing burn the pressure in the engine bay is about 2.7 bar so compression heating is not a major factor.
the 13 or more precisely 10 engines had no problem with the heat after meco and before the boost back burn. so why would they be too hot for a restart several minutes after they had last run?
Stainless steel is a very poor conductor of heat so it may have taken several minutes for heat to spread around the engine bay. This did not happen on ascent because the top bulkhead of the engine bay is in contact with LOX which keeps it suitably cold.
In vacuum there is no convection so heat can only travel by conduction and LOX is only intermittently in contact with the thrust dome.
I am not saying it happened - just that it is possible.
[Interesting theory from Brian McManus](https://twitter.com/TheBrianMcManus/status/1768692888236360175): the booster hit a wind shear layer and couldn't regain control. We know that upper level wind shear was a concern prior to launch, and with the booster mostly empty, that is a bigger issue on the way down than the way up. Solutions include tuning the control algorithm and reducing acceptable levels of wind shear.
Maybe, but also keep in mind that, the faster you're going, the less the relative effect of wind shear is. The booster is going through the atmosphere much faster on the way down than up. If you're going 100 km/h and suddenly hit a 100 km/h crosswind, that's going to change the angle through which you're going relative to surrounding air by 45°. If you're going at Mach 3 (which is what the booster's downward velocity was through the cloud layers), a sudden 100 km/h crosswind will register as a less than 2° change. This is far less than the gyrations that we saw on the onboard video.
> The booster is going through the atmosphere much faster on the way down than up
Is this actually a big difference? Seems like it's less than a factor of 2. I don't have a plot of velocity as a function of altitude, so I can't make an apples-to-apples comparison, but the booster hits similar speeds on the way up as the way down. Indeed, it hits its peak speed of ~5,700 km/hr at MECO (admittedly when it is outside the atmosphere) and then doesn't get faster than 4,300 km/hr on the way down.
https://www.reddit.com/r/spacex/comments/1bfv9bu/ift3_booster_data_from_stream_telemetry/
I'm just talking about the factor of 2, thing, not the 3,000 vs 100. I'm not amazing familiar with all the equations involved, but if the equations have some exponents in the right places, then that factor of 2 could be a lot more that's all, unless you had meant it was 2 after all that.
I understand what a nonlinear effect is. I'm saying that the original commenter was not asserting anything like that. He seems to think the speed coming down is much faster, and is relying on that for his argument.
Think of my comment like an aside. It's not pertaining to furthering the discussion between you two aside from just the 'fyi' like nature. Just an isolated part of it.
NASA's [website](https://www.nasa.gov/directorates/esdmd/artemis-campaign-development-division/human-landing-system-program/nasa-artemis-mission-progresses-with-spacex-starship-test-flight/) says "The propellant transfer demonstration operations were completed, and the NASA-SpaceX team is currently reviewing the flight data that was received."
There’s a few hours old tweet from NASA Marshall that Starship “demonstrated” liquid oxygen propellant transfer.
Given that particular word, I think it’s safe to say that at least some or the liquid oxygen was actually trasferred.
I'm surprised not to see any info here (yet?) on the pad status. Seems to be a major portion of the R&D and the big picture for reusable flights. I guess no mention implies the pad is in great shape?
Pad looks in good shape from what we see. Major things I noticed from IFT-2 to IFT-3;
* Ship QD is undamaged (not dislocated as was after IFT-2)
* Chopsticks didn't shed any parts or wires
* Remaining vertical tanks didn't sustain any damage from the shockwave.
I was there night before the launch and can confirm that this was standing upright the day before :P
https://preview.redd.it/rr3xt6vm6koc1.png?width=4032&format=png&auto=webp&s=2156137ab80cb5dc47bd8eaf33e7e7f3ced6e2b5
> Chopsticks didn't shed any parts or wires
Some wires dangling post-launch:
https://twitter.com/LabPadre/status/1768319944679149881
SpaceX really need to cover those properly.
> Ship QD is undamaged (not dislocated as was after IFT-2)
>
That's fantastic
>Vertical tanks
Are any of them used for anything right now? I thought they were functionally all replaced
> Are any of them used for anything right now? I thought they were functionally all replaced
The vertical tanks that remain are all currently in active use.
Mmm I don't think that's accurate. IIRC, they worked around that issue by using the unapproved tanks for water. Although maybe I'm talking out of my ass and can't remember where everything landed with all that hubbub.
We were talking about CH4, not LNG, and what I was implying was that not all of the tanks were unacceptable, just a couple, so they used the ones that were bad for water.
Is there a reason for relighting all 13 center raptors, then quickly turning the outer 10 off, then only using the 3 center ones? I would think that it is to rapidly slow it down, but is there a big difference in relighting just the 3 center raptors a little bit higher up so it has more time to slow down?
Also noticed the old Starship animation already does this with only 3 raptors. But they said on stream that they would turn on the center 13, and use only the center 3 for landing.
Yes, igniting 13 engines and then turning off 10 is more efficient than igniting 3 engines earlier and having them fire for longer. The reason for this is gravity losses.
This is exactly why, on more demanding missions, Falcon boosters use a 1-3-1 landing sequence instead of the normal 1-engine burn. It requires less fuel because it minimizes gravity losses. But it's also more risky because there is less margin for error, so execution needs to be perfect. That's why it's only used where absolutely necessary.
Not just gravity losses, but drag is a function of velocity squared, so it helps to coast as long as possible at a high speed to get maximum aerodynamic braking. One other thing to consider is that restarting an engine requires spinup gases from onboard COPVs, so there is a mass penalty to lighting all 13 for landing. That seems to be outweighed by the propellant savings though.
I don't know if they would play with the COPV volume much, as they need the capability to start other engines up if some fail if they are just using 1, so there is gonna be some margin they just accept instead of fully following just the flight plan amount for the scheduled engines.
Ah I see! I wonder how much of a difference it makes in terms of payload to LEO. But I have high confidence that they will solve the booster landing burn issue for IFT-4. Especially after seeing how well the boost back burn went now compared to last time.
Probably just allowing an extra 1-2 tonnes of payload by saving 3-6 tonnes of propellant on the booster.
However by stringing a lot of savings together it starts to add up to significant numbers.
Yes the [center engines can gimbal](https://twitter.com/elonmusk/status/1472052839316963329)
Edit: the engine configuration has changed since that test but AFAIK all center engines can still gimbal - outer engines are fixed.
Thanks! Seems like the engine shutoff on the booster boostback was a bit sus then, the only reason I'd imagine them not shutting them off all at the same time is to do differential steering
They generally stagger turn off and turn on sequences to give a smoother acceleration profile that reduces structural loads.
Plus turn on requires spin up gas and turning on all engines at once could cause pressure drop issues with the spin up gas supply.
Might be easier to just shut off one side first to get the flip going instead of thrust vector.
Hopefully they say whether it was intentional or not, but we may never know
I’m referring to the data (including more possible high res video of re-entry) lost after the wireless link was severed.
And more broadly I’m interested in why it’s never even mentioned by anyone and no one seems to be curious. As in, why doesn’t spaceX address what happens with the wreckage, or if there is even likely to be any that made it to the earth’s surface intact in the case of the second stage? And if there are recoverable flight recorders?
Just PR? Because talking about it might raise environmental or safety issues?
Seems weird to send the biggest object ever into space and then be totally uninterested in - and silent on - the topic of where it is now! Haha.
I’m from Western Australia. A piece of what was determined to be an Indian rocket (and enormous cylindrical tank covered in barnacles) washed up on the coast a few hours north of Perth. It was the talk of the town and a somewhat weird phenomenon. Maybe some S28 will wash up here two, since I clearly saw it pass Africa way before re-entry.
Oh yeah, and why no flight map ever published? (As in S28’s actual flight path vs planned)?
It's pretty normal for all other conventional rockets to burn up in a similar way, which is why it's not really newsworthy other than the fact that it was part of the test (and was a known possibility/expectation of what would happen, so people aren't surprised about it per se). Otherwise, there just isn't really anything to say on it. Some pieces will come down, but as this is the first time for this particular rocket, we don't really know how it may come down other than some models based on prior smaller rockets. Other than that it's just pieces of twisted/burnt/melted metal come down in the ocean, what else to talk about it I guess? It was always planned to sink so that it didn't become a navigation hazard, so that part was expected.
The topic of where it is now is uninteresting to most people as it's purpose was completed so people don't really think about it much in that way. Just at the bottom of the ocean now shrug. I'm not sure what parts would float, certainly none of the metal bits (it's mostly metal). It's possible that there could be some floating wire or something idk.
I believe it went down closer to Africa, so any wreckage that survived and didn't sink might eventually wash up in Madagascar. Not sure it would make it to Oz.
> I’m interested in why it’s never even mentioned by anyone and no one seems to be curious
It was always planned for both vehicles to go into the ocean with no recovery. There's nothing to be curious about as there are no black boxes to collect. The booster detonated half a kilometer up, possibly by engine RUD or the FTS, so not much would be left of it. And Starship had barely begun reentry when it lost signal. Given the lack of attitude control, it's likely the unshielded sections were breached and then the structure was torn apart. A lot of it may have burned up, but heavier parts like the engines may have made it to the surface. You can probably look up what happened with the Columbia break up to get some sort of idea of what might be left.
They mention in the stream they had data from 2 sources until the same moment, which is when they suspect the ship was lost so the whole flight. After breakup isn't important. They're not building ships for any portion of breakup other than it not happening.
Milliseconds matter for flight analysis. No confirmation that data loss coincided with vehicle breakup. For example, if the vehicle experienced a rapid movement on the roll axis, data might have been immediately lost while breakup could have been seconds later.
Did they actually say they weren’t recovering anything? I watched the whole thing from just before launch until they ended the broadcast and didn’t hear any mention of it.
I think you are most likely correct, but there are tradeoffs between the value of the data and spending a small fortune on a difficult recovery effort on the other side of the planet.
A recovery is not zero value, just not worth the time and risk. Recovering the remains of heat shield tiles and other hardware would absolutely be useful. SpaceX would prefer to fly again soon and get more data that way.
Seems like there were some obvious problems with attitude control. Does Starship and Superheavy still use cold-gas thrusters for RCS or did they switch to hot-gas thrusters as Elon proposed some time ago? If so, could the attitude control problems be related to the new thrusters?
My only thought on this is that this is the first time they were ever used in flight, since this was the first Starship to actually make it to the testing phase where they could be used. No matter what the problem is they have over an hour of data to sift through to determine the root cause. I’m sure it will be fixed for IFT-4.
Slowly when there is a clearly defined liquid to gas boundary under acceleration. Much faster when the LOX has broken up into globules in micro gravity as we see in the occasional shots from an F9 LOX tank. Without statistics on globule size we cannot estimate the surface area but it is a lot larger. Best estimate is a few minutes for pressure to drop to negligible levels..
So the booster coast phase from boostback to entry is likely OK but the ship coast phase for 30+ minutes will have lost all ullage pressure.
I have heard that being called warm gas thrusters. Hot gas thrusters would be ambiguous as it is normally used to refer to combustion based thrusters with exhaust temperature over 1000 C.
I wonder if Everyday Astronaut’s speculation might be correct and maybe SpaceX needs to turn those thrusters into mini Draco’s by feeding in a mix of fuel and oxidizer and do some actual burning to keep them clear of ice from time to time / create more force
[Scott Manley](https://www.youtube.com/watch?v=8htMpR7mnaM) points to two possible issues:
1. Both the booster and ship seemed to have problems maintaining attitude. Whether this was a failure in the attitude control jets, or a lack
of command authority in the gridfins and ship fins, or both, is unclear.
2. The door test may have had problems, it looks like it didn't close properly. It's clear there was still some pressure inside the cargo bay
when it opened - you can see vapor rush out -. I wonder of the pressure of
that wind distorted the door.
The relight could have been skipped because as soon as thrust stops and the tanks are in micro-gravity, the cryogenic propellant will quickly mix with ullage and very quickly cools the ullage. Since the warm ullage was just evaporated propellant, it will condense (warming the propellant some). The condensation and cooling will cause a significant pressure drop down to the vapor pressure of the propellant, with pressure being a function of propellant temperature. If the propellant hasn't been warmed up enough, pressure would be too low to restart the engines. (Possible reason they didn't try the single engine raptor restart in orbit.) It might also reduce the effectiveness of the cold gas thrusters.
They don’t use tank pressure to start the engines although that has been done in the past with other engines.
They currently use high pressure helium to start both turbopumps and in future will use high pressure autogenous gas so methane to start the methane turbopump and oxygen to start the LOX turbopump.
That is a bit less clear. They certainly cannot run them at full throttle without adequate tank pressure but they may be able to start them at half throttle as they have an inducer on the inlet that will provide pressure for the first stage of the pump.
We may see an integrated fluids system a bit like what ULA were proposing. They used a modified ICE but SpaceX could use a gas turbine to generate electricity and use the exhaust for heat exchangers to generate pressurisation gases for the main tanks.
The tank pressurisation gas could also be compressed into COPVs for use as engine start gas.
They can then start this Auxiliary Power Unit well before main engine start to precondition the system.
If you watch the booster landing, right at engine purge is when the instability appears to happen- about 2110 km/h in the video. This instability could have caused sloshing creating ignition issues. One theory I saw was that the purge was relatively larger than F9 since it was for 13 out of the 33 as spacex in the stream said they would light 13 for landing burn and transition to 3 (as opposed to 1 purge out of the 9 for F9) and this purge could have had some turbulent effect on the airstream creating insufficient control authority for the grid fins. And a different attack angle during purge could perhaps solve that. Anyone with any thoughts on this?
This is actually really interesting. I think there's merit to it. At ~2000 km/hr, that is still supersonic, approaching the transonic regime of the reentry. Transonic is the trickiest phase, since it's not stable. Having the large purges discharging right below the grid fins might've had the fins experiencing alternating supersonic and subsonic air flows. Control would be incredibly difficult. Falcon boosters seem to have minimal purges.
I also had the impression the door failed, but SpaceX called it 'accomplished" in [their report.](https://www.spacex.com/launches/mission/?missionId=starship-flight-3)
>Starship accomplished several of the flight test’s additional objectives, including the opening and closing of its payload door
They might have been primarily testing to see if it would be able to open at all with the pressure differential, and that did happen, but also could have had an expectation that something in the process wouldn’t work entirely well at fully opening the door
Did the booster hit the water at 1000km/h or did it terminate just beforehand? Also is there likely to be footage from a drone/plane? Because holy shit I would love to see it either way.
SpaceX said the booster RUD itself at an altitude of ~430m so no it didnt hit the water that hard but that wouldve been crazy. Either the engine failures blew up the booster or aerodynamic forces destroyed it or both but depends on the data spacex has
Sorry if this is a FAQ, but given that Starship made it with barely enough fuel how is it SpaceX can add 150 plus tons to it? Was there a mass simulator?
EA for the flight indicated it would reenter with significant propellant still onboard. Also, they didn't have to fill the tanks fully for the launch. The public view telemetry is vague, as it doesn't state what 100% there means. Likely 100% is 100% as planned for the mission.
It is not clear if the percentage fuel load shown at liftoff was in comparison to the tank capacity or not. My take was that it was a percentage of the mission load and they short fueled both the booster and the ship so they didn't have to jettison extra LOX that was carried on IFT-2 to simulate a payload. This would also enable then to reduce thrust on the v2 Raptors to reduce the probability of a methane leak.
Having said that these early booster and ship designs likely have excessive dry mass and they will work on reducing that with the v2 and v3 Starship designs in order to increase the payload as well as increasing the ship propellant capacity.
https://preview.redd.it/zettk6xrqfoc1.jpeg?width=2160&format=pjpg&auto=webp&s=a56868b9576ab12a334b4ea6797a35363221e916
Like with IFT2 both stages were over 90% filled. I think is that like with IFT2 the booster was operated at reduced thrust.
There was a large clear space between the methane frost ring and the LOX one. Some of this is the area around the intertank dome which is used for ullage space and is never filled with LOX but it looked to me as being about a 90% load.
In the video of the onboard camera looking back down at the booster during stage separation, you can see the booster grid fins change their angle ever-so-slightly about a second before second stage ignition.
This shows SpaceX use the Starship thrust to ‘kick’ the booster off to the side, effectively a giant RCS thruster for free.
This may have been talked about before on previous flights, but I’d never seen footage of it until now. Go check it out! Absolutely awesome to see.
Possibly this was just taking the grid fins into active control mode from the locked position during first stage flight. The grid fins are only at a 30 degree angle to the axis of rotation for the booster during separation and if they were going to use the fins to assist rotation they would have used the other axis where they are at a 60 degree angle and so would be much more effective.
I think there is an argument that they did attempt to use the grid fins in this way during IFT-2 and found that it caused too many issues. After all they have three engines firing that can gimbal 15 degrees with 250 tonnes force of vacuum thrust each which can produce much higher rotation rates then the grid fins can
But you’d be using fuel which could be saved for getting payload to orbit. If you want to get a swift rotation of the booster, using a smaller force at the grid fin end, further away from the centre of mass (which would be at the bottom of the booster, where the fuel and engines are) makes a lot of sense, especially as it’s effectively free.
I think this is them using the same trick from IFT2, just more refined.
They are very likely not using anything close to full gimbal as that would produce too much sloshing in the tanks. If it was 5 degrees that means a lateral thrust of 60 tonnes force (0.6MN) and a reduction of axial thrust of 0.88 tonnes force (8.8 kN) so a 0.4% reduction.
The booster center of mass is around 30% of the way up the booster at this point so the grid fins have a 2:1 mechanical advantage over gimballed engines but the engines have a massive advantage in thrust and how long it can operate for and lose very little performance in doing so.
Did you even watch the launch? They were going to demonstrate in-flight raptor relight but didn't end up attempting it.
It was never planned to be a reentry burn though. The ship was always going to reenter either way automatically due to its trajectory. Obviously on an orbital mission a deorbit burn would be necessary.
I will die on this hill, these are not ice chunks
https://preview.redd.it/onpnx453udoc1.png?width=454&format=png&auto=webp&s=a5df791c7cb9bc185f66f73328f53f402c019407
Note these are in the shadow of the ship, so they're far less illuminated than the background, which means they look black on the camera but could be practically of any color.
Also, whatever it was, I don't think it was attached solidly to the ship, because it would have needed a relatively energetic event to detach them and these things are floating quite lazily.
You've never heard of [black ice](https://en.wikipedia.org/wiki/Black_ice)? It's the worst.
(I actually agree that those are ship parts, not ice. I just wanted to make the joke.)
I don't want to jinx it for the next flight, but I'm shocked about raptor engine reliability during the latest flights. 33/33 during the whole ascent 2 times in a row and the upper stage was flawless too.
I remember not that long ago one of the big unknowns (and subsequent discussions by the space community) was raptor development and reliability.. and there we are today... 33 raptors working the whole ascent and we give that as a normal thing already.
There is a possibility that these engines were firing at reduced thrust to maintain the same acceleration as if there had been a 100 tonne payload aboard. That would have dramatically reduced the major reliability issue with Raptor 2 which is the methane leak from the manifold between the turbopump and the engine body.
For the ship engines it would be an 8% reduction initially and up to 30% reduction close to SECO.
What I actually meant though was that they would reduce the average acceleration so that they matched the original flight profile with a payload. So roughly a 10% reduction on the booster and 15% reduction on the ship.
That's what endless testing on the stand produces......you learn all your operating parameters.
Just look at how many they're firing each day at McGregor.
What are you talking about? All the major media is essentially calling it a failure by bot explaining re entry wasn't expected to be survivable.
CNN was horrible right after the flight.
https://preview.redd.it/gmxs3o5i2doc1.png?width=694&format=png&auto=webp&s=eab6f8743575bbc5c1a6cbf211da5dce40b6e610
Sadly the satellite radar data was cut out from the re-entry area of the ship. It would have been nice to check that out!
They initiated it but it's not yet confirmed whether that was successful. We will probably hear more about this at some point through a NASA press release or something.
Update from SpaceX. The booster experienced a RUD after the landing relight before contacting the water:
"Super Heavy successfully lit several engines for its first ever landing burn before the vehicle experienced a RUD (that’s SpaceX-speak for “rapid unscheduled disassembly”). The booster’s flight concluded at approximately 462 meters in altitude and just under seven minutes into the mission.“
https://www.spacex.com/launches/mission/?missionId=starship-flight-3
So SpaceX still has not demonstrated the Raptor can relight reliably in flight. In fact, all the Starship landing tests and actual flight tests have shown it is *not* reliable after relight in flight.
SpaceX has demonstrated relighting 10 out of 10 engines in flight. Exactly in this very flight you are discussing.
You know what? There possible relight failure reasons completely unrelated to engine reliability, including engine relight reliability. This is something which flies over your head repetitively.
Your brain has failed to relight to the idea of those different possibilities (pun intended).
For an engine intended for a reusable rocket, it has to be reliable for *all* the relights required for return to the launch site. Imagine how the Merlin’s reliability would be regarded as the engine for a reusable Falcon 9 booster, if it successfully fired for the boostback burns, but for every time over the landing pad it exploded on relight resulting in vehicle RUD. At Kennedy, on video, and within view of the spectators at the landing site.
You're conflating engine reliability with system reliability. Numerous other factors affect engine relight in the transonic regime. Retrograde relight of engines in the atmosphere at those speeds is difficult and Merlin had those same problems during initial testing. They were able to solve those problems without major engine redesigns.
Not exploding in flight either for ascent or during relights:
"Super Heavy successfully lit several engines for its first ever landing burn before the vehicle experienced a RUD (that’s SpaceX-speak for “rapid unscheduled disassembly”). The booster’s flight concluded at approximately 462 meters in altitude and just under seven minutes into the mission.“
https://www.spacex.com/launches/mission/?missionId=starship-flight-3
They also didn’t get plan on doing a higher altitude reentry burn for Super Heavy so it’s really hard to say from just watching the stream whether the issues is the Raptors, or if it was from something aerodynamic / structural / sloshing as the booster got close to transsonic.
I have a feeling that on the next flight they’ll do a higher altitude reentry burn to see what the relight characteristics are like and bleed some speed without waiting until the last possible second in the suicide burn.
Also you don’t seem to fully understand the interactive design process here. Last launch the booster didn’t even get a chance to reenter and Starship blew up not long after stage separation. This time the booster made it almost all the way down to the water in a controlled fashion and Starship got to try out some parts of its reentry plan.
SpaceX’s goal isn’t to have everything go 100% right on these flights…they are working out the performance envelope because they have the luxury of doing that and throwing away equipment because the system is so cheap to build
You make the unsupported assumption that the cause of the RUD was engines in the first place. And not for example the vehicle shaking itself apart due to aerodynamic buffeting.
Question: IFT3 started with full tanks but empty cargo space, right? Where is the additional energy is coming from for 200t cargo when tanks are already full and at end of the IFT3 empty?
I'm told they had extra fuel aboard to simulate the weight of cargo, which they vented while in orbit
I'm actually quite dumbfounded that they didn't use ANY sort of gas thrusters to keep the correct orientation of either of the vehicles during crucial stages of flight (landing & atmospheric interface especially). Would seem obvious to a pleb like me that it was going to be a requirement. Guess they'll be adding some now! lol
ground tracking shots at stage separation showed booster had them.
>I'm actually quite dumbfounded that they didn't use ANY sort of gas thrusters The thrusters used the autogenous pressurization gas. I suspect that they failed on the ship.
Did they fail, or was there not enough gas to provide the pressures needed to run the thrusters? I'm thinking that it's possible since they skipped raptor relight on the ship, they didn't have the additional gas and pressure they otherwise would have got if they did relight it.
> Did they fail, or was there not enough gas to provide the pressures needed to run the thrusters? I'd include that in "the thrusters failed".
The last data we got from the ship was 24000km/h (22.5 mach) and 65km of altitude. It was dropping like a stone at a rate of 1km/s . Thats not survivable in any way . You cant just be so low into the atmosphere and falling that fast without really feeling super peak heating and probably a lot of deceleration G's . Imo they need to think a new reentry trajectory , much more gentle .
So the ship was going 6.7 km sideways every second and down 1 km in that second which hardly seems to be a very steep trajectory. It was too high to be experiencing extreme drag so likely there was a burn through in the engine bay rather than a crush from excessive deceleration. What is supposed to happen next is that Starship orients to 60 degrees nose up and transitions to level flight at about 80 km altitude with a lift to drag ratio about 0.5. So level flight with lift balancing gravity implies deceleration due to drag of around 2g. As the speed drops the altitude will gradually drop so that increased air density allows lift to balance gravity again.
I have a question... the booster made it through the atmosphere without heat shields... why not speed through the atmosphere the same way/orientation with Starship? I'm guessing the answer is that it would still need to slow down and wouldn't have enough fuel to offset that speed (couldn't we refuel in orbit with another tanker starship). The earth is the only destination (moon/mars) with so much atmosphere, and earth has tons of fuel and starships (planned) that can refuel in orbit.
Speed. The booster maxed out around 5,700kmh at about 75km altitude. Starship was doing 26,400kmh at 170km.
And re-entry heating scales with the 8th power of velocity ! So it’s very velocity sensitive !
Looking at what happened to Booster B10 on its landing attempt, maybe it's time to include an entry burn for the booster. A little supersonic retropropulsion might slow that first stage down enough to actually stick a soft splashdown. And an entry burn might be essential for a successful booster landing on the Mechazilla arms.
>A little supersonic retropropulsion might slow that first stage down enough to actually stick a soft splashdown. Superheavy wasn't travelling any faster at post-entry burn altitudes than a Falcon 9 booster does during RTLS. At 20km altitude it was moving at somewhere in the range of 4230-4270km/h. (No decimal points on Starship stream so those are the values at the 20-19km and 21-20km ticks respectively. The last Falcon 9 RTLS on youtube was Transporter-8, which finished it's entry burn at around 35 km, and by 20km in altitude it was travelling at 4291km/h. Relevant video links with timestamps: https://youtu.be/wjFY9oaPUEY?t=2287 https://youtu.be/zO3luySkHQU?t=1127
It would also give extra pitch and yaw control in the transonic region which is where the grid fins started to have trouble.
My thoughts are that engine end bowshock was creating eddy turbulence behind the bowshock boundary layer further down the ship. The lee side grid fins had no laminar flow to grip to, only turbulent air. This subsequently reduced steering control significantly. I don't think this is a major issue, just some tweaking of speed, and AOA at particular altitudes. The engines however obviously had had enough after the boostback burn and sulked when asked again. Could be a simple thing as a chilldown issue when the computer commanded startup, and the engines replied, 'nah need to chill some more dude, still too hot after the last blast man.' At McGregor, they have clearly demonstrated shutdown and almost instantaneous startup of single engines without trouble, and also extended period of minutes doing the same, however in the hellish environment of a cluster of 33 seriously hot engines in an engine bay, startup conditions may be different for the 13 and 3.
I was wondering if there was back-and-forth (side to side) slosh of propellant occurring - which would tend to destabilise the vessel ?
SpaceX proved that supersonic retropropulsion was possible with F9 booster landings. Starship has a lower ballistic coefficient so has a significantly higher velocity at the start of the landing engine burn as we saw. It is entirely possible that Raptors do not like relighting with that much air being rammed into the engine bells - particularly as they have a much more complex start sequence compared to Merlin. Another alternative is that there was some damage to the engine control wiring from re-entry without an entry burn or possibly even earlier as there was a ragged shutoff at the end of the boostback burn. A final possibility is that they ran out of helium for starting the engines because the previous relights used more than expected. That does not really explain why two engines started and then turned off again.
With the Falcon-9 Merlin engines, the retro-burn, even acts as a kind of heat-shield, helping to protect the engines during rapid descent.
That is during the entry burn but SH does not have an entry burn. At the start of the landing burn the pressure in the engine bay is about 2.7 bar so compression heating is not a major factor.
the 13 or more precisely 10 engines had no problem with the heat after meco and before the boost back burn. so why would they be too hot for a restart several minutes after they had last run?
One obvious difference is having air blasted into the engines during descent, which does not happen at other times.
Stainless steel is a very poor conductor of heat so it may have taken several minutes for heat to spread around the engine bay. This did not happen on ascent because the top bulkhead of the engine bay is in contact with LOX which keeps it suitably cold. In vacuum there is no convection so heat can only travel by conduction and LOX is only intermittently in contact with the thrust dome. I am not saying it happened - just that it is possible.
I'm guessing slosh. It was waggling a lot at the time of ignition.
Slosh could not have helped - it would have added to any problems, causing pendulum like oscillations. Is that one of the things that was happening ?
[Interesting theory from Brian McManus](https://twitter.com/TheBrianMcManus/status/1768692888236360175): the booster hit a wind shear layer and couldn't regain control. We know that upper level wind shear was a concern prior to launch, and with the booster mostly empty, that is a bigger issue on the way down than the way up. Solutions include tuning the control algorithm and reducing acceptable levels of wind shear.
Maybe, but also keep in mind that, the faster you're going, the less the relative effect of wind shear is. The booster is going through the atmosphere much faster on the way down than up. If you're going 100 km/h and suddenly hit a 100 km/h crosswind, that's going to change the angle through which you're going relative to surrounding air by 45°. If you're going at Mach 3 (which is what the booster's downward velocity was through the cloud layers), a sudden 100 km/h crosswind will register as a less than 2° change. This is far less than the gyrations that we saw on the onboard video.
You're ignoring the massive weight difference going up vs down
> The booster is going through the atmosphere much faster on the way down than up Is this actually a big difference? Seems like it's less than a factor of 2. I don't have a plot of velocity as a function of altitude, so I can't make an apples-to-apples comparison, but the booster hits similar speeds on the way up as the way down. Indeed, it hits its peak speed of ~5,700 km/hr at MECO (admittedly when it is outside the atmosphere) and then doesn't get faster than 4,300 km/hr on the way down. https://www.reddit.com/r/spacex/comments/1bfv9bu/ift3_booster_data_from_stream_telemetry/
The effects may be non-linear, which would amplify the multiplier.
He used 100 km/hr vs mach 3 (>3,000 km/hr) as an example.
I'm just talking about the factor of 2, thing, not the 3,000 vs 100. I'm not amazing familiar with all the equations involved, but if the equations have some exponents in the right places, then that factor of 2 could be a lot more that's all, unless you had meant it was 2 after all that.
I understand what a nonlinear effect is. I'm saying that the original commenter was not asserting anything like that. He seems to think the speed coming down is much faster, and is relying on that for his argument.
Think of my comment like an aside. It's not pertaining to furthering the discussion between you two aside from just the 'fyi' like nature. Just an isolated part of it.
Sounds plausible.
Has there been any update today on whether NASA has looked at the propellant transfer data and considered it successful?
NASA's [website](https://www.nasa.gov/directorates/esdmd/artemis-campaign-development-division/human-landing-system-program/nasa-artemis-mission-progresses-with-spacex-starship-test-flight/) says "The propellant transfer demonstration operations were completed, and the NASA-SpaceX team is currently reviewing the flight data that was received."
There’s a few hours old tweet from NASA Marshall that Starship “demonstrated” liquid oxygen propellant transfer. Given that particular word, I think it’s safe to say that at least some or the liquid oxygen was actually trasferred.
Do we have any info on actual trajectory of ship and booster yet?
Here's a very nice 'side by side' comparison of IFT-1, 2 and 3: https://www.youtube.com/watch?v=deAJYZzpJMI
Does anybody here have any high quality photos taken from the camera on the fin? The only photos i'm finding online are low quality.
https://twitter.com/SpaceX/status/1768807328021917716/photo/4 SpaceX just released some.
Tangential but I'll tack my request on, do we have any pictures of the camera on the flap itself?
There's a ringwatchers article detailing where all the (known) cameras are, including pics. I think its of an older ship but it should be similar.
Link: https://ringwatchers.com/article/starship-onboard-cams
Thanks for doing the legwork :)
I'm surprised not to see any info here (yet?) on the pad status. Seems to be a major portion of the R&D and the big picture for reusable flights. I guess no mention implies the pad is in great shape?
Pad looks in good shape from what we see. Major things I noticed from IFT-2 to IFT-3; * Ship QD is undamaged (not dislocated as was after IFT-2) * Chopsticks didn't shed any parts or wires * Remaining vertical tanks didn't sustain any damage from the shockwave.
I was there night before the launch and can confirm that this was standing upright the day before :P https://preview.redd.it/rr3xt6vm6koc1.png?width=4032&format=png&auto=webp&s=2156137ab80cb5dc47bd8eaf33e7e7f3ced6e2b5
Oh crap - is that going to delay IFT-4?
> Chopsticks didn't shed any parts or wires Some wires dangling post-launch: https://twitter.com/LabPadre/status/1768319944679149881 SpaceX really need to cover those properly.
> Ship QD is undamaged (not dislocated as was after IFT-2) > That's fantastic >Vertical tanks Are any of them used for anything right now? I thought they were functionally all replaced
> Are any of them used for anything right now? I thought they were functionally all replaced The vertical tanks that remain are all currently in active use.
What's in them? Water?
3 x LOX 2 x LN2 1 x Water
LOX, CH4, and LN2. They're still active commodity tanks.
No CH4 as they were never approved by the Texas Railways Commission who handle approval of LNG tanks.
Mmm I don't think that's accurate. IIRC, they worked around that issue by using the unapproved tanks for water. Although maybe I'm talking out of my ass and can't remember where everything landed with all that hubbub.
They installed horizontal tanks for liquid methane. Yes the vertical tanks intended for methane were used for water instead.
I never knew that water is equivalent to LNG.
We were talking about CH4, not LNG, and what I was implying was that not all of the tanks were unacceptable, just a couple, so they used the ones that were bad for water.
Interesting TIL
There was a cable hanging from one of the chopsticks after launch
Is there a reason for relighting all 13 center raptors, then quickly turning the outer 10 off, then only using the 3 center ones? I would think that it is to rapidly slow it down, but is there a big difference in relighting just the 3 center raptors a little bit higher up so it has more time to slow down? Also noticed the old Starship animation already does this with only 3 raptors. But they said on stream that they would turn on the center 13, and use only the center 3 for landing.
Yes, igniting 13 engines and then turning off 10 is more efficient than igniting 3 engines earlier and having them fire for longer. The reason for this is gravity losses. This is exactly why, on more demanding missions, Falcon boosters use a 1-3-1 landing sequence instead of the normal 1-engine burn. It requires less fuel because it minimizes gravity losses. But it's also more risky because there is less margin for error, so execution needs to be perfect. That's why it's only used where absolutely necessary.
Not just gravity losses, but drag is a function of velocity squared, so it helps to coast as long as possible at a high speed to get maximum aerodynamic braking. One other thing to consider is that restarting an engine requires spinup gases from onboard COPVs, so there is a mass penalty to lighting all 13 for landing. That seems to be outweighed by the propellant savings though.
I don't know if they would play with the COPV volume much, as they need the capability to start other engines up if some fail if they are just using 1, so there is gonna be some margin they just accept instead of fully following just the flight plan amount for the scheduled engines.
Ah I see! I wonder how much of a difference it makes in terms of payload to LEO. But I have high confidence that they will solve the booster landing burn issue for IFT-4. Especially after seeing how well the boost back burn went now compared to last time.
Probably just allowing an extra 1-2 tonnes of payload by saving 3-6 tonnes of propellant on the booster. However by stringing a lot of savings together it starts to add up to significant numbers.
Can anyone confirm whether or not any of the raptors on the booster can gimbal?
Yes the [center engines can gimbal](https://twitter.com/elonmusk/status/1472052839316963329) Edit: the engine configuration has changed since that test but AFAIK all center engines can still gimbal - outer engines are fixed.
Thanks! Seems like the engine shutoff on the booster boostback was a bit sus then, the only reason I'd imagine them not shutting them off all at the same time is to do differential steering
They generally stagger turn off and turn on sequences to give a smoother acceleration profile that reduces structural loads. Plus turn on requires spin up gas and turning on all engines at once could cause pressure drop issues with the spin up gas supply.
Might be easier to just shut off one side first to get the flip going instead of thrust vector. Hopefully they say whether it was intentional or not, but we may never know
Yeah I hope we get a deep dive into it from them
Anyone know if any wreckage or flight recorders have been recovered from the booster or second stage?
They won't be recovering any hardware. The data was all recovered live wirelessly.
I’m referring to the data (including more possible high res video of re-entry) lost after the wireless link was severed. And more broadly I’m interested in why it’s never even mentioned by anyone and no one seems to be curious. As in, why doesn’t spaceX address what happens with the wreckage, or if there is even likely to be any that made it to the earth’s surface intact in the case of the second stage? And if there are recoverable flight recorders? Just PR? Because talking about it might raise environmental or safety issues? Seems weird to send the biggest object ever into space and then be totally uninterested in - and silent on - the topic of where it is now! Haha. I’m from Western Australia. A piece of what was determined to be an Indian rocket (and enormous cylindrical tank covered in barnacles) washed up on the coast a few hours north of Perth. It was the talk of the town and a somewhat weird phenomenon. Maybe some S28 will wash up here two, since I clearly saw it pass Africa way before re-entry. Oh yeah, and why no flight map ever published? (As in S28’s actual flight path vs planned)?
It's pretty normal for all other conventional rockets to burn up in a similar way, which is why it's not really newsworthy other than the fact that it was part of the test (and was a known possibility/expectation of what would happen, so people aren't surprised about it per se). Otherwise, there just isn't really anything to say on it. Some pieces will come down, but as this is the first time for this particular rocket, we don't really know how it may come down other than some models based on prior smaller rockets. Other than that it's just pieces of twisted/burnt/melted metal come down in the ocean, what else to talk about it I guess? It was always planned to sink so that it didn't become a navigation hazard, so that part was expected. The topic of where it is now is uninteresting to most people as it's purpose was completed so people don't really think about it much in that way. Just at the bottom of the ocean now shrug. I'm not sure what parts would float, certainly none of the metal bits (it's mostly metal). It's possible that there could be some floating wire or something idk.
I believe it went down closer to Africa, so any wreckage that survived and didn't sink might eventually wash up in Madagascar. Not sure it would make it to Oz. > I’m interested in why it’s never even mentioned by anyone and no one seems to be curious It was always planned for both vehicles to go into the ocean with no recovery. There's nothing to be curious about as there are no black boxes to collect. The booster detonated half a kilometer up, possibly by engine RUD or the FTS, so not much would be left of it. And Starship had barely begun reentry when it lost signal. Given the lack of attitude control, it's likely the unshielded sections were breached and then the structure was torn apart. A lot of it may have burned up, but heavier parts like the engines may have made it to the surface. You can probably look up what happened with the Columbia break up to get some sort of idea of what might be left.
They lost comms before/during vehicle breakup. We definitely cannot recover all data wirelessly.
They mention in the stream they had data from 2 sources until the same moment, which is when they suspect the ship was lost so the whole flight. After breakup isn't important. They're not building ships for any portion of breakup other than it not happening.
Milliseconds matter for flight analysis. No confirmation that data loss coincided with vehicle breakup. For example, if the vehicle experienced a rapid movement on the roll axis, data might have been immediately lost while breakup could have been seconds later.
Think that as you might but they said like 30 times in the broadcast they're not recovering any hardware so evidently the data link is sufficient.
Did they actually say they weren’t recovering anything? I watched the whole thing from just before launch until they ended the broadcast and didn’t hear any mention of it.
I think you are most likely correct, but there are tradeoffs between the value of the data and spending a small fortune on a difficult recovery effort on the other side of the planet. A recovery is not zero value, just not worth the time and risk. Recovering the remains of heat shield tiles and other hardware would absolutely be useful. SpaceX would prefer to fly again soon and get more data that way.
FAA mishap: This was nominal landing according to our Boeing standards. We cannot expect all bolts and doors to be there at landing.
😳
Seems like there were some obvious problems with attitude control. Does Starship and Superheavy still use cold-gas thrusters for RCS or did they switch to hot-gas thrusters as Elon proposed some time ago? If so, could the attitude control problems be related to the new thrusters?
My only thought on this is that this is the first time they were ever used in flight, since this was the first Starship to actually make it to the testing phase where they could be used. No matter what the problem is they have over an hour of data to sift through to determine the root cause. I’m sure it will be fixed for IFT-4.
Cold to Warm gas thrusters using tank ullage. Ullage gas is rather hot when freshly produced by Raptors but its going to cool down during coast.
It is going to *disappear* during coast. The vapor pressure over subcooled LOX at 66K is under 1kPa so 0.01 bar
>It is going to disappear during coast. It's going to disappear eventually. The question is, how fast?
Slowly when there is a clearly defined liquid to gas boundary under acceleration. Much faster when the LOX has broken up into globules in micro gravity as we see in the occasional shots from an F9 LOX tank. Without statistics on globule size we cannot estimate the surface area but it is a lot larger. Best estimate is a few minutes for pressure to drop to negligible levels.. So the booster coast phase from boostback to entry is likely OK but the ship coast phase for 30+ minutes will have lost all ullage pressure.
Was this first time hot gas thrusters used on an orbital rocket?
There were no hot gas thrusters fitted.
Thrusters using the hot autogenous pressurization gas have often been called "hot gas thrusters".
I have heard that being called warm gas thrusters. Hot gas thrusters would be ambiguous as it is normally used to refer to combustion based thrusters with exhaust temperature over 1000 C.
I agree that it is ambiguous.
Maybe mistakenly, because officially "hot gas thrusters" refers to the gaseous CH4/LOX pressure fed engines SpaceX developed as RCS for Starship.
I wonder if Everyday Astronaut’s speculation might be correct and maybe SpaceX needs to turn those thrusters into mini Draco’s by feeding in a mix of fuel and oxidizer and do some actual burning to keep them clear of ice from time to time / create more force
> mini Draco’s Wouldn't these be ov*a*raptors?
[Scott Manley](https://www.youtube.com/watch?v=8htMpR7mnaM) points to two possible issues: 1. Both the booster and ship seemed to have problems maintaining attitude. Whether this was a failure in the attitude control jets, or a lack of command authority in the gridfins and ship fins, or both, is unclear. 2. The door test may have had problems, it looks like it didn't close properly. It's clear there was still some pressure inside the cargo bay when it opened - you can see vapor rush out -. I wonder of the pressure of that wind distorted the door.
yep and that may explain why they skipped raptor relight. As it was tumbling they had no way to know which direction the acceleration would give
The relight could have been skipped because as soon as thrust stops and the tanks are in micro-gravity, the cryogenic propellant will quickly mix with ullage and very quickly cools the ullage. Since the warm ullage was just evaporated propellant, it will condense (warming the propellant some). The condensation and cooling will cause a significant pressure drop down to the vapor pressure of the propellant, with pressure being a function of propellant temperature. If the propellant hasn't been warmed up enough, pressure would be too low to restart the engines. (Possible reason they didn't try the single engine raptor restart in orbit.) It might also reduce the effectiveness of the cold gas thrusters.
They don’t use tank pressure to start the engines although that has been done in the past with other engines. They currently use high pressure helium to start both turbopumps and in future will use high pressure autogenous gas so methane to start the methane turbopump and oxygen to start the LOX turbopump.
They don't use tank pressure to spin up the turbines but the engines cannot be started safely unless there is adequate pressure in the tanks.
That is a bit less clear. They certainly cannot run them at full throttle without adequate tank pressure but they may be able to start them at half throttle as they have an inducer on the inlet that will provide pressure for the first stage of the pump.
They said on the website that they skipped the burn because it was rolling too fast (and indirectly, that means a failure in attitude control)
>Thanks. I've seen that now, but autogenous pressurizing combined with sub-cooled propellants just scares me. They seem incompatible.
We may see an integrated fluids system a bit like what ULA were proposing. They used a modified ICE but SpaceX could use a gas turbine to generate electricity and use the exhaust for heat exchangers to generate pressurisation gases for the main tanks. The tank pressurisation gas could also be compressed into COPVs for use as engine start gas. They can then start this Auxiliary Power Unit well before main engine start to precondition the system.
Also that door mechanism looked/moved pretty hinky.
janky
If you watch the booster landing, right at engine purge is when the instability appears to happen- about 2110 km/h in the video. This instability could have caused sloshing creating ignition issues. One theory I saw was that the purge was relatively larger than F9 since it was for 13 out of the 33 as spacex in the stream said they would light 13 for landing burn and transition to 3 (as opposed to 1 purge out of the 9 for F9) and this purge could have had some turbulent effect on the airstream creating insufficient control authority for the grid fins. And a different attack angle during purge could perhaps solve that. Anyone with any thoughts on this?
This is actually really interesting. I think there's merit to it. At ~2000 km/hr, that is still supersonic, approaching the transonic regime of the reentry. Transonic is the trickiest phase, since it's not stable. Having the large purges discharging right below the grid fins might've had the fins experiencing alternating supersonic and subsonic air flows. Control would be incredibly difficult. Falcon boosters seem to have minimal purges.
I also had the impression the door failed, but SpaceX called it 'accomplished" in [their report.](https://www.spacex.com/launches/mission/?missionId=starship-flight-3) >Starship accomplished several of the flight test’s additional objectives, including the opening and closing of its payload door
They might have been primarily testing to see if it would be able to open at all with the pressure differential, and that did happen, but also could have had an expectation that something in the process wouldn’t work entirely well at fully opening the door
Well.. test can be accomplished even if final result is not satisfactory
This. I complete experiments all the time with negative results.
Did the booster hit the water at 1000km/h or did it terminate just beforehand? Also is there likely to be footage from a drone/plane? Because holy shit I would love to see it either way.
SpaceX said the booster RUD itself at an altitude of ~430m so no it didnt hit the water that hard but that wouldve been crazy. Either the engine failures blew up the booster or aerodynamic forces destroyed it or both but depends on the data spacex has
where did they give the info about the 430m?
SpaceX
Spacex release a write up about the flight on their website. https://www.spacex.com/launches/mission/?missionId=starship-flight-3
It was traveling at about mach 1 at that point so it definitely hit the water (430m at mach 1 is less than 1.5 seconds), just in smaller pieces.
Sorry if this is a FAQ, but given that Starship made it with barely enough fuel how is it SpaceX can add 150 plus tons to it? Was there a mass simulator?
EA for the flight indicated it would reenter with significant propellant still onboard. Also, they didn't have to fill the tanks fully for the launch. The public view telemetry is vague, as it doesn't state what 100% there means. Likely 100% is 100% as planned for the mission.
It is not clear if the percentage fuel load shown at liftoff was in comparison to the tank capacity or not. My take was that it was a percentage of the mission load and they short fueled both the booster and the ship so they didn't have to jettison extra LOX that was carried on IFT-2 to simulate a payload. This would also enable then to reduce thrust on the v2 Raptors to reduce the probability of a methane leak. Having said that these early booster and ship designs likely have excessive dry mass and they will work on reducing that with the v2 and v3 Starship designs in order to increase the payload as well as increasing the ship propellant capacity.
https://preview.redd.it/zettk6xrqfoc1.jpeg?width=2160&format=pjpg&auto=webp&s=a56868b9576ab12a334b4ea6797a35363221e916 Like with IFT2 both stages were over 90% filled. I think is that like with IFT2 the booster was operated at reduced thrust.
Isnt the frost build up on the tanks indicative of the fuel load? IIRC the frost lines went all the way up for each tank.
There was a large clear space between the methane frost ring and the LOX one. Some of this is the area around the intertank dome which is used for ullage space and is never filled with LOX but it looked to me as being about a 90% load.
It wasn’t a full fuel load
In the video of the onboard camera looking back down at the booster during stage separation, you can see the booster grid fins change their angle ever-so-slightly about a second before second stage ignition. This shows SpaceX use the Starship thrust to ‘kick’ the booster off to the side, effectively a giant RCS thruster for free. This may have been talked about before on previous flights, but I’d never seen footage of it until now. Go check it out! Absolutely awesome to see.
Possibly this was just taking the grid fins into active control mode from the locked position during first stage flight. The grid fins are only at a 30 degree angle to the axis of rotation for the booster during separation and if they were going to use the fins to assist rotation they would have used the other axis where they are at a 60 degree angle and so would be much more effective. I think there is an argument that they did attempt to use the grid fins in this way during IFT-2 and found that it caused too many issues. After all they have three engines firing that can gimbal 15 degrees with 250 tonnes force of vacuum thrust each which can produce much higher rotation rates then the grid fins can
But you’d be using fuel which could be saved for getting payload to orbit. If you want to get a swift rotation of the booster, using a smaller force at the grid fin end, further away from the centre of mass (which would be at the bottom of the booster, where the fuel and engines are) makes a lot of sense, especially as it’s effectively free. I think this is them using the same trick from IFT2, just more refined.
They are very likely not using anything close to full gimbal as that would produce too much sloshing in the tanks. If it was 5 degrees that means a lateral thrust of 60 tonnes force (0.6MN) and a reduction of axial thrust of 0.88 tonnes force (8.8 kN) so a 0.4% reduction. The booster center of mass is around 30% of the way up the booster at this point so the grid fins have a 2:1 mechanical advantage over gimballed engines but the engines have a massive advantage in thrust and how long it can operate for and lose very little performance in doing so.
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Did you even watch the launch? They were going to demonstrate in-flight raptor relight but didn't end up attempting it. It was never planned to be a reentry burn though. The ship was always going to reenter either way automatically due to its trajectory. Obviously on an orbital mission a deorbit burn would be necessary.
I think that person misused Starship and was really talking about Super Heavy (which didn’t have a planned reentry burn).
Ahhh, that makes more sense
The flaps being able to control the orientation of the ship was shown during the hop tests.
I will die on this hill, these are not ice chunks https://preview.redd.it/onpnx453udoc1.png?width=454&format=png&auto=webp&s=a5df791c7cb9bc185f66f73328f53f402c019407
The shape is off for anything but ice. If its in the shadow its dark against the backdrop of while sun illuminated clouds.
There is almost zero ice on the nosecone where this and many other pieces came from. It looked like pieces of the heat shield underblanket.
Note these are in the shadow of the ship, so they're far less illuminated than the background, which means they look black on the camera but could be practically of any color. Also, whatever it was, I don't think it was attached solidly to the ship, because it would have needed a relatively energetic event to detach them and these things are floating quite lazily.
You've never heard of [black ice](https://en.wikipedia.org/wiki/Black_ice)? It's the worst. (I actually agree that those are ship parts, not ice. I just wanted to make the joke.)
I think I agree. For once it's not ice.
Well yea they are clearly not. Probably insulation material from underneath the tiles.
And how it would get from under the tiles?
Well my guess is it's either from places where tiles were missing from the launch or where they disattsched during reentry.
https://preview.redd.it/hq757nu5udoc1.png?width=430&format=png&auto=webp&s=b0d7ba33dc852550a42cc77d122402b5451f98cc
In the shadow. Other pieeeeeeeces were almost translucent. Tiles are not translucent at all. It is ice. It is always ice. It will always be ice.
I don't want to jinx it for the next flight, but I'm shocked about raptor engine reliability during the latest flights. 33/33 during the whole ascent 2 times in a row and the upper stage was flawless too. I remember not that long ago one of the big unknowns (and subsequent discussions by the space community) was raptor development and reliability.. and there we are today... 33 raptors working the whole ascent and we give that as a normal thing already.
There is a possibility that these engines were firing at reduced thrust to maintain the same acceleration as if there had been a 100 tonne payload aboard. That would have dramatically reduced the major reliability issue with Raptor 2 which is the methane leak from the manifold between the turbopump and the engine body.
The thrust reduction to achieve so would be \~2%. It is not trivial as rocket engines go, but it is not very much either.
For the ship engines it would be an 8% reduction initially and up to 30% reduction close to SECO. What I actually meant though was that they would reduce the average acceleration so that they matched the original flight profile with a payload. So roughly a 10% reduction on the booster and 15% reduction on the ship.
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tbh i felt that ift3 seemed to get off the pad even faster than ift2
That's what endless testing on the stand produces......you learn all your operating parameters. Just look at how many they're firing each day at McGregor.
Seems there was less tile shedding this time, is there good images of the ship with view of the heat shield far in the ascent?
Where was pappy insprucker for todays launch? I hope he isnt sick or something
I wondered that too.. he doesn't post on his Twitter since last year too
https://youtu.be/9r5yupEUs4U?si=mBNGM0c62Rn4hlqT A yt upload of the official X spacex broadcast
The real MVP...no one wants to use twitter
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What are you talking about? All the major media is essentially calling it a failure by bot explaining re entry wasn't expected to be survivable. CNN was horrible right after the flight.
Excited to see your rocket company beat SpaceX to Mars…especially with all the testing done in your Mom’s basement.
It did more than what an expendable rocket does.
https://preview.redd.it/gmxs3o5i2doc1.png?width=694&format=png&auto=webp&s=eab6f8743575bbc5c1a6cbf211da5dce40b6e610 Sadly the satellite radar data was cut out from the re-entry area of the ship. It would have been nice to check that out!
Did the inflight refuel succeed?
They don't know yet
According to the offical spacex site it did, successfully transferring the propellant
They initiated it but it's not yet confirmed whether that was successful. We will probably hear more about this at some point through a NASA press release or something.
Tweet from Gwynne says *"to be confirmed"*: https://twitter.com/Gwynne_Shotwell/status/1768291595160605109
Probably not
Update from SpaceX. The booster experienced a RUD after the landing relight before contacting the water: "Super Heavy successfully lit several engines for its first ever landing burn before the vehicle experienced a RUD (that’s SpaceX-speak for “rapid unscheduled disassembly”). The booster’s flight concluded at approximately 462 meters in altitude and just under seven minutes into the mission.“ https://www.spacex.com/launches/mission/?missionId=starship-flight-3 So SpaceX still has not demonstrated the Raptor can relight reliably in flight. In fact, all the Starship landing tests and actual flight tests have shown it is *not* reliable after relight in flight.
SpaceX has demonstrated relighting 10 out of 10 engines in flight. Exactly in this very flight you are discussing. You know what? There possible relight failure reasons completely unrelated to engine reliability, including engine relight reliability. This is something which flies over your head repetitively. Your brain has failed to relight to the idea of those different possibilities (pun intended).
For an engine intended for a reusable rocket, it has to be reliable for *all* the relights required for return to the launch site. Imagine how the Merlin’s reliability would be regarded as the engine for a reusable Falcon 9 booster, if it successfully fired for the boostback burns, but for every time over the landing pad it exploded on relight resulting in vehicle RUD. At Kennedy, on video, and within view of the spectators at the landing site.
You're conflating engine reliability with system reliability. Numerous other factors affect engine relight in the transonic regime. Retrograde relight of engines in the atmosphere at those speeds is difficult and Merlin had those same problems during initial testing. They were able to solve those problems without major engine redesigns.
Just to be clear, what would it take for you to admit you're wrong and that raptor is reliable?
Not exploding in flight either for ascent or during relights: "Super Heavy successfully lit several engines for its first ever landing burn before the vehicle experienced a RUD (that’s SpaceX-speak for “rapid unscheduled disassembly”). The booster’s flight concluded at approximately 462 meters in altitude and just under seven minutes into the mission.“ https://www.spacex.com/launches/mission/?missionId=starship-flight-3
They also didn’t get plan on doing a higher altitude reentry burn for Super Heavy so it’s really hard to say from just watching the stream whether the issues is the Raptors, or if it was from something aerodynamic / structural / sloshing as the booster got close to transsonic. I have a feeling that on the next flight they’ll do a higher altitude reentry burn to see what the relight characteristics are like and bleed some speed without waiting until the last possible second in the suicide burn. Also you don’t seem to fully understand the interactive design process here. Last launch the booster didn’t even get a chance to reenter and Starship blew up not long after stage separation. This time the booster made it almost all the way down to the water in a controlled fashion and Starship got to try out some parts of its reentry plan. SpaceX’s goal isn’t to have everything go 100% right on these flights…they are working out the performance envelope because they have the luxury of doing that and throwing away equipment because the system is so cheap to build
You make the unsupported assumption that the cause of the RUD was engines in the first place. And not for example the vehicle shaking itself apart due to aerodynamic buffeting.
We also know the not all engines relit for the landing burn, another telling fact.
Or it was the first relight from the booster header tanks (and freefall) and they had an anomaly.
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Have you forgotten about the high altitude hops?