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]

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

Like the Russians do...

 

[Electroman]

… or perhaps cold gas thrusters which are there for belly flop maneuver can come in handy. Dual purpose, for staging and belly flop

 

[mongo]

… or perhaps cold gas thrusters which are there for belly flop maneuver can come in handy. Dual purpose, for staging and belly flop

No discrete cold gas, just tank vents. Flip is mostly (all?) engines.
Could vent O2 through engines, but there needs to be more force than the aero drag difference between Starship and Super Heavy to cause separation.

 

[JohnnyEnglish]

No discrete cold gas, just tank vents. Flip is mostly (all?) engines.
Could vent O2 through engines, but there needs to be more force than the aero drag difference between Starship and Super Heavy to cause separation.

Difficult to see how Starship gets human rated with a separation mechanism that requires the booster to remain fully operational and controlled. It does not seem to have any fault tolerance.

 

[mongo]

Difficult to see how Starship gets human rated with a separation mechanism that requires the booster to remain fully operational and controlled. It does not seem to have any fault tolerance.

Well, if you don't care about the booster surviving, nor reaching the intended orbit, there are other options.

 

[JB47394]

Difficult to see how Starship gets human rated with a separation mechanism that requires the booster to remain fully operational and controlled. It does not seem to have any fault tolerance.

I think you're getting a little bit ahead of things. The human-rated Starship is going to need to be a very different type of vehicle. For one, it'll need to be able to separate from the booster even at maxQ in the case of booster failure. The cargo variant doesn't have many safety requirements on it, so they're going to do everything they can to get as much mass into space as possible on each flight. One way of doing that is to eliminate any system that isn't absolutely needed. This flick maneuver is used to eliminate a traditional separation system.

 

[Electroman]

No discrete cold gas, just tank vents. Flip is mostly (all?) engines.
Could vent O2 through engines, but there needs to be more force than the aero drag difference between Starship and Super Heavy to cause separation.

Aero drag? I thought at MECO they are well above any aero drags. Atleast not to the extent it makes any difference.

 

[mongo]

Aero drag? I thought at MECO they are well above any aero drags. Atleast not to the extent it makes any difference.

It's pretty thin up there (60km, 64m^2, 0.2 drag, 500kph is only 800 lbs); however, with Starship in the lead, if its total drag is more than Booster, the mating surfaces won't part.
At time of separation, they want Booster to slow faster than Starship to avoid collision. Releasing clamps when Starship is aligned with (minimal) airstream would help with that.
Ah, light bulb in the ol' grey matter. If they hinge opposite a clamp (3 total), then there is minimal binding potential. More risk of sliding though...

 

[ecarfan]

I wish that SpaceX would make public a detailed description of Starship stage sep and put us all out of our speculation misery…

 

[mongo]

I wish that SpaceX would make public a detailed description of Starship stage sep and put us all out of our speculation misery…

Where's the fun in that?

 

[Bobfitz1]

I think you're getting a little bit ahead of things. The human-rated Starship is going to need to be a very different type of vehicle. For one, it'll need to be able to separate from the booster even at maxQ in the case of booster failure. The cargo variant doesn't have many safety requirements on it, so they're going to do everything they can to get as much mass into space as possible on each flight. One way of doing that is to eliminate any system that isn't absolutely needed. This flick maneuver is used to eliminate a traditional separation system.

I expect SpaceX is stuck with using this flip maneuver to separate for the next launch or two. I hope the as yet untested maneuver doesn't become the second missed attempt to reach orbit. I'm sure they are already in progress designing the moon landing variant's top of ship mini engines to land and take back off. Not close to an enginee, but if one variant is already going to have them, perhaps they could be used for a much simpler separation mechanism for the other variants? Of course they would have to be positioned or protected in some way for earth reentry, which if difficult/complicated, would make the idea a non starter.

 

[bxr140]

Like the Russians do...

FWIW their separation (at least on Proton's since that's the only one I've flown on...but I'm pretty sure Soyuz is the same...and also The Chinese...) is to simply start up the second stage motors before shutting down and releasing the first stage. There's a ~conical flame diverter on the top of the first stage and the interstage truss structures are wide open so as to not build up pressure between the two stages. Obviously those first stages are destined to smash into The Steppe rather than be reused (their sheet metal skins definitely are not quickly repurposed into shelter walls and roofs by The Local Kazakhs That Aren't In The Drop Zone Because Nobody Lives In The Drop Zone) so there's no concern over damage to the first stage by the second stage plume.

For SS--and this may have been covered in other content already--it seems like the primary problem SX is trying to solve with any kind of off-axis separation sequence is to create useful separation between S and B before firing up S, for the primary purpose of not damaging B with S's plume. Traditionally rocket (and satellite) separations are done with basic coil springs which more or less impart a coaxial force between the separating bodies...maybe some are done with pneumatics (not sure what the F9 mvac pusher uses, TBH). I'd guess the issue is that S and B are so massive that a traditional-ish concept would mass, and/or complicate, and/or timeline out to an untenable, or at least very undesirable solution. Old Newt #1, as it were. And #3 I guess...

With an off axis separation you don't need coaxial distance between the two bodies, you just need enough angular separation that S's plume won't fry B's noggin on startup.

<Insert closing Michel Jackson joke>

 

[JB47394]

I hope the as yet untested maneuver doesn't become the second missed attempt to reach orbit.

As the booster won't be reused, I'm sure they can try the Russian approach as a fallback.

I'm sure they are already in progress designing the moon landing variant's top of ship mini engines to land and take back off. Not close to an enginee, but if one variant is already going to have them, perhaps they could be used for a much simpler separation mechanism for the other variants?

I can see them being used for separation when the moon landing variant is launched from Cape Canaveral, but it's a huge mass penalty for use only as a separation system.

not sure what the F9 mvac pusher uses

Pneumatics.

I wonder how much damage would be inflicted on the booster top by pushing off on-axis, waiting for a little separation, then firing the gimbaling engines while vectoring the thrust off-axis. That's assuming that they can be started while vectored. The vectored thrust would miss the booster and Starship could be quickly oriented however desired.

And now I'm half-seriously pondering the damage due to firing a single Starship engine before separation, but rapidly vectoring in a circle in order to keep the heating across the top of the booster to a minimum. Or how about a flame diverter on top of the booster? So many silly notions to explore.

 

[HVM]

Elon Musk pushes for orbital goal following data gathering objectives during Starship debut - NASASpaceFlight.com

Following the maiden launch of the world’s most powerful rocket, SpaceX hopes to conduct a…

www.nasaspaceflight.com

 

[Electroman]

I hope the as yet untested maneuver doesn't become the second missed attempt to reach orbit.

Exactly what I am worried too.

Just close & seal the top of the Methane/LOX tanks with a metal disk layered with heat tiles. Fire one SS engine at lowest power for one second. Hopefully that should be enough to gently separate them. Once they have drifted far away, fire all the SS engines and off we go.

 

[mongo]

Exactly what I am worried too.

Just close & seal the top of the Methane/LOX tanks with a metal disk layered with heat tiles. Fire one SS engine at lowest power for one second. Hopefully that should be enough to gently separate them. Once they have drifted far away, fire all the SS engines and off we go.

No worries about starting a methane oxygen engine into a closed space?
Raptor 2 is 250 tons of thrust, even at 20% that's 100,000 pounds-force at near zero distance from a flat plate.
Could get thrust/ separation force by venting O2 into the space from the 3 sea level Raptors. Or aft facing vent/thrusters.

 

[Bobfitz1]

I can see them being used for separation when the moon landing variant is launched from Cape Canaveral, but it's a huge mass penalty for use only as a separation system.

I'm sure there are a plenty of reasons for not using moon variant upper engines for a stage separation. But my guess is huge mass penalty would not be one of them. I don't know if SX has yet released details of the size, weight,, thrust or number of the moon variant landing thrusters. We do know a SuperDraco engine can produce 15,000 + lbs of thrust and is small and light enough for eight to fit in the Dragon capsule.
Starship is 100 tons dry weight and moon is 1/6 earth gravity. I'd think 3 or 4 of them might supply sufficient thrust to lift off moon. In any event it will be interesting to learn what they've decided to use for this and their specs.

 

[Electroman]

at least on Proton's since that's the only one I've flown on

??? What ?

 

[bxr140]

??? What ?

Lol. We can get a little possessive sometimes about our satellites.

 

[Grendal]

Lol. We can get a little possessive sometimes about our satellites.

As the moderator, I try to read everything and get a general idea of where everyone is coming from. I got your reference immediately. Plus, I'm almost certain that Proton is not human rated.