SpaceX Starship - Orbital Test Flight - Starbase TX

Launch Date: April 20
Launch Window: 8:28am CDT (6:28am PDT, 13:28 UTC) - 62 minute window
Launch site: LC-1? - Starbase, Boca Chica Beach, Texas
Core Booster Recovery: Expended in Gulf
Starship Recovery: Water landing near Hawaii
Booster: Super Heavy Booster 7
Starship: Starship 24
Mass: No mass simulator mentioned
Orbit: LEO-ish
Yearly Launch Number: 26

A SpaceX Super Heavy and Starship launch vehicle will launch on its first orbital test flight. The mission will attempt to travel around the world for nearly one full orbit, resulting in a re-entry and splashdown of the Starship near Hawaii.

Webcast:

 

[Grendal]

This applies to all rockets but I'm sure Manley put this out now because of the issues with Starship's FTS.

 

[ecarfan]

Thanks for posting the link to the twitter spaces discussion.

So the booster was using autogenous pressurization (not helium) and they got good data about the performance of that system. It “looked quite good”. Which is great news!

One thing I don’t understand, “We initiated the flight termination system but it took way too long to rupture the tanks.” “On the order of 40 secondish”. “Need a longer detonation cord”. But when the FTS is commanded to detonate, why did it take so long? An explosion should be essentially instantaneous.

At T+00:27 there was an event that ”liberated the outer heat shields” from the engine 17/18/1920 area. So that explosion was not an HPU but came from inside the vehicle? They don’t know what caused that explosion.

At T+00:62 “we see additional aft heat shield damage near engine 30 but the engine continued to run”.

At T+00:85 “things hit the fan”. “Engine 6 lost communication to thrust vector control”. That is what I heard him say. Which is very different from saying that all TVC was lost. But then he says that from that point on TVC was lost. Maybe it was lost gradually? I’m not clear.

The regeneratively water cooled “massive steel pancake” with holes in the top surface (to handle the booster exhaust at liftoff) will be connected to the OLM legs. He says the damage to Stage Zero was “minor”. I know that hole looks pretty dramatic but he seems to think it can be fixed quickly and there is nothing else major to deal with besides replacing some of the GSE tanks.

When he talked about “stage separation being different from Falcon” I wish he had explained in some detail how it was different.

And when asked which ship number will be used for test flight 2 he did not commit, only saying that they want a ship with TPS. So maybe not S28. TBD.

 

[Electroman]

If the engines were not damaged by concrete debris, then what was the root cause of those engine failures ?

 

[ecarfan]

If the engines were not damaged by concrete debris, then what was the root cause of those engine failures ?

That has not been publicly revealed, and possibly SpaceX doesn’t know yet. Or they do know and aren’t saying. Elon only said that the engines ignited and then were quickly shut down because they weren’t “healthy” enough to ramp up to full throttle for liftoff.

 

[mongo]

One thing I don’t understand, “We initiated the flight termination system but it took way too long to rupture the tanks.” “On the order of 40 secondish”. “Need a longer detonation cord”. But when the FTS is commanded to detonate, why did it take so long? An explosion should be essentially instantaneous.

The explosion happened instantaneous, but did not cause enough damage to destroy the rocket. Longer detcord = bigger hole.

When he talked about “stage separation being different from Falcon” I wish he had explained in some detail how it was different.

Starlink like pitch manuver, then release the clamps.
Scott Manley made a potential simulation

https://twitter.com/x/status/1651031623859843073

 

[Electroman]

Wow the 2nd animation looks so convoluted and so complex it is almost SciFi’sh. I can’t fathom how that will work reliably. So much drama.

Would rather the traditional design of two side boosters with Starship in the middle might be simpler ?

 

[ecarfan]

Starlink like pitch manuver, then release the clamps.
Scott Manley made a potential simulation

https://twitter.com/x/status/1651031623859843073

Wow, that is dramatic! In that animation, MECO occurs after the pitch change is initiated. So I assume the change is initiated by the center engines and then MECO occurs which causes Starship to separate. At that point it is angled 90 degrees to the flight path so it has to use it’s sea level Raptors to reverse the pitch change and then the R Vacs ignite?

The animation by @Lezzyl_ seems implausible to me, a totally not-a-rocket-scientist.

 

[mongo]

Wow, that is dramatic! In that animation, MECO occurs after the pitch change is initiated. So I assume the change is initiated by the center engines and then MECO occurs which causes Starship to separate. At that point it is angled 90 degrees to the flight path so it has to use it’s sea level Raptors to reverse the pitch change and then the R Vacs ignite?

The animation by @Lezzyl_ seems implausible to me, a totally not-a-rocket-scientist.

Yeah, Scott's seems more realistic. More angle relative to trajectory means higher differential aero between booster and Starship, but also more energy lost. Ideally, Starship would be inline with (thin) airstream and booster would angle out into it.

 

[JB47394]

I read somewhere that the idea was to rock the ship to one side, then rock it back again. As it's rocking back, cut the engines. It's the same as Scott's approach, but it leaves Starship better aligned with the direction of travel.

I originally thought that was being attempted on the Starship flight, and that the thicker air was preventing a rock back movement.

 

[mongo]

I read somewhere that the idea was to rock the ship to one side, then rock it back again. As it's rocking back, cut the engines. It's the same as Scott's approach, but it leaves Starship better aligned with the direction of travel.

I originally thought that was being attempted on the Starship flight, and that the thicker air was preventing a rock back movement.

There was no separation attempt on the recent test flight due to not reaching activation criteria.

 

[bxr140]

I read somewhere that the idea was to rock the ship to one side, then rock it back again.

Scandinavian flick.

 

[ecarfan]

I read somewhere that the idea was to rock the ship to one side, then rock it back again.

Yes, yawing the vehicle rather than pitching it would seem intuitively to make more sense but maybe either would work.

During the livestream, when John said “continuing to fly at 2 minutes 40 seconds let’s get ready for main engine cutoff” it appeared by that point that TVC was already lost. At T+02:51 he said “beginning the flip for stage separation” but the vehicle looked out of control. It was tumbling.

It was as if John was reading from a script and not making allowances for what was actually happening.

I originally thought that was being attempted on the Starship flight, and that the thicker air was preventing a rock back movement.

@mongo clarified that, and Elon said later that stage sep was never commanded. See upthread.

 

[ecarfan]

Eric Berger has posted his summary of Elon’s twitter spaces discussion of the test flight. Nothing really new for those who have been following what he said, but a nice summary.

 

[Electroman]

So far no insight on why engines failed.

Also no confirmation if the rest of the engines performed & gave adequate thrust as expected throughout

 

[Dan D.]

I read somewhere that the idea was to rock the ship to one side, then rock it back again. As it's rocking back, cut the engines. It's the same as Scott's approach, but it leaves Starship better aligned with the direction of travel.

I originally thought that was being attempted on the Starship flight, and that the thicker air was preventing a rock back movement.

There's a good video on stage separation here: Says it spins them using the gimbling engines on the Super Heavy and they float apart. If the visual at 3:15 is accurate, it's a very gentle amount of spin, but this video is from 2021, so could be old news. I have also heard they are yawing it and flicking - which sounds like a slightly different maneuver, maybe something new they have come up with recently. In any case it's not very much motion, certainly not a loop. I didn't find anything official from SpaceX yet on how they visualize the separation, so I'm not sure exactly what was intended.

 

[ecarfan]

Eric Berger reports: Environmental groups sue the FAA over SpaceX launch from Texas

I was expecting that. It is unclear to me whether or not such a suit is likely to effect Starship launches this year unless the litigants can persuade a judge to issue an emergency injunction banning the FFA from issuing any more launch licenses. But given that US Fish & Wildlife has stated that no animals were killed or injured by the test flight, and that cleanup is already underway, I think the risk of that is low.

 

[ecarfan]

There's a good video on stage separation here: Says it spins them using the gimbling engines on the Super Heavy and they float apart.

Thanks for posting that video. The precise technique SpaceX plans to use is still not clear to me. That video says that the booster will gimbal its engines to “rotate itself” and “introduce angular momentum” moments before MECO and then the latches will be opened.

But during the Starship test flight webstream John talked about a “flip maneuver“ before stage sep.

Rotating the vehicle around the long axis is not a “flip” to me. A flip is a pitch change, though I suppose it could also be a yaw.

Perhaps the planned maneuver combines a pitch change and a rotation?

 

[Dan D.]

Thanks for posting that video. The precise technique SpaceX plans to use is still not clear to me. That video says that the booster will gimbal its engines to “rotate itself” and “introduce angular momentum” moments before MECO and then the latches will be opened.

But during the Starship test flight webstream John talked about a “flip maneuver“ before stage sep.

Rotating the vehicle around the long axis is not a “flip” to me. A flip is a pitch change, though I suppose it could also be a yaw.

Perhaps the planned maneuver combines a pitch change and a rotation?

It may not involve rotation at all. That video from 2021 does not really seem to match what was being described during the launch, so it might be obsolete information.

I also heard the flip maneuver described as like a hinge between Super Heavy booster and Starship allowing flexing in the yaw direction - like a trailer fishtailing, but with the trailer doing the pushing. I guess they release certain latches first.

The Super Heavy booster gimbles its thrust to one side, this creates an angle between the booster and the Starship section. Then it gimbles the thrust the other way and straightens the angle. All latches are released at the correct time so the two sections push apart on their own. SpaceX intends that this gives enough force to Starship that when they fire its engines it is far enough away to not damage the earth-returning booster.

If they haven't actually tested this separation for real then perhaps it's not proven how well it will work. You certainly don't want to disrupt the Starship section's path too much, but they can correct that with course adjustments. Also you need to make sure the sections separate smoothly and without any damage.

I'm piecing this description together from bits I read about. It's just a guess.

 

[Electroman]

Here is a dumb idea. Why not do MECO and then release latches and then g-e-n-t-l-y fire one Starship engine at say 10% power just enough for it move away and then blast all the engines.

 

[JB47394]

Here is a dumb idea. Why not do MECO and then release latches and then g-e-n-t-l-y fire one Starship engine at say 10% power just enough for it move away and then blast all the engines.

Minimum Raptor throttle is 20% and they may not be able to start them at that level. It wouldn't do the top of the methane tank of the booster (a reusable vehicle) much good. Along similar lines, they could run the turbopumps to create gas pressure, but the Raptor may only be able to pump both species, resulting in a potential for an explosion.

Hmmm. Pump some methane and oxygen into the cavity between stages, set it off and Bob's Your Uncle. Conflagration staging.