Starship 26 Potential Usage Theories

[JohnsterSpaceProgram]

I'm not sure if anyone has thought of this before, but what if SpaceX is planning on using Ship 26 (which I'll refer to as S26 for the rest of this post) as the first full-scale Human Landing System (HLS) mockup? As we currently know, HLS vehicles will be flap-less, and S26 also doesn't have any flaps. We also know that SpaceX has decided to modify the S22 nosecone into an HLS prototype of sorts, so what if they end up also modifying S26 at some point in the future as their next step in the development of HLS prototypes and hardware ahead of the first Artemis demonstration missions?

Such as painting it to look like an HLS vehicle along with the addition of a human sized door to it, like what has been done on the S22 nosecone. It would also give them something else to show NASA that they are making progress in the development of their HLS vehicle for the future Artemis lunar missions. And maybe one of the reasons they are likely going to be testing S26 soon is that if they want to use it on an HLS prototype flight (maybe that would just be to LEO to prove it can function properly in space), it would have already completed most or all of the necessary testing before undergoing HLS-related modifications and then being launched on a future starship flight.

Now, it could also end up being that they just use S26 as an expendable starship protype without making HLS modifications to it, and that's definitely a possibly. Or they could just end up scrapping the ship at some point (like what happened to S27) once it becomes obsolete or is replaced by newer and improved bare-bones starship prototypes that also lack the heat shield tiles and flaps, and maybe they would end up using one of those for an HLS mockup instead.

I would also like to hear what your theories are on what S26 could end up being used for. Maybe I'll end up being totally wrong about this HLS usage theory for S26, but we'll have to wait and see what happens to the ship.

[eriblo]

The main structure of HLS will most likely be different enough from a standard Starship that it will be harder to modify one than to build it new:

HLS will likely have expanded tank capacity (top and common dome moved, longer fuel transfer tube).
Crew compartment aft pressure bulkhead.
Landing thrusters with associated reinforcement and plumbing.
Possibly larger header tanks inside the main tanks for propellant management on the surface.

S26 could do some limited test of longer duration handling on orbit and response to the environment in LEO with the benefit of being more (but far from fully) demisable in the case of an uncontrolled reentry.

[DanClemmensen]

SpaceX has a contract with NASA to demonstrate cryofluid transfer. The contract is separate from Artemis, I think, and transfer from tank to tank on a single ship satisfies the contract. I think that S26 will be used for this. It flies as a very simple SS as part of the early Starship test campaign, EDL is not required, and SapceX collects the $50 M as a side benefit. It probably needs to actually achieve a stable orbit to do a sufficiently long test, so it must be able to do a controlled de-orbit. This disqualified it from being the IFT SS, since the IFT calls for a well-targeted deorbit even if the SS engines fail.

[wannamoonbase]

SpaceX has a contract with NASA to demonstrate cryofluid transfer. The contract is separate from Artemis, I think, and transfer from tank to tank on a single ship satisfies the contract. I think that S26 will be used for this. It flies as a very simple SS as part of the early Starship test campaign, EDL is not required, and SapceX collects the $50 M as a side benefit. It probably needs to actually achieve a stable orbit to do a sufficiently long test, so it must be able to do a controlled de-orbit. This disqualified it from being the IFT SS, since the IFT calls for a well-targeted deorbit even if the SS engines fail.

I agree that this is S26's purpose.  I think it will fly when SpaceX has confidence in SH and possibly once they are recoverying and reflying SH.

Getting to the point that they recover and reuse SH will truly jumpstar the SS development and flight cadence.  I think will likely happen in the second half of 2024.

[JohnsterSpaceProgram]

SpaceX has a contract with NASA to demonstrate cryo-fluid transfer. The contract is separate from Artemis, I think, and transfer from tank to tank on a single ship satisfies the contract. I think that S26 will be used for this. It flies as a very simple SS as part of the early Starship test campaign, EDL is not required, and SpaceX collects the $50M as a side benefit. It probably needs to actually achieve a stable orbit to do a sufficiently long test, so it must be able to do a controlled de-orbit. This disqualified it from being the IFT SS, since the IFT calls for a well-targeted deorbit even if the SS engines fail.

I also think that this could be a likely potential use for Ship 26 as well. Because rather than SpaceX having to build another Ship prototype and go through all of the testing for it before attempting a cryo-fluid transfer in orbit as part of their contract for NASA, they could just use S26 instead since it has already done some cryo-proof testing and should hopefully have completed a static fire soon as well, which would then likely wrap up most (if not the rest) of it's testing before a flight.

[Brigantine]

Not discounting potential on-orbit uses for S26, but I want to point out that S26 will be the first time they get any aerodynamic data on expendable / flapless ships above 10 km. They're gonna want that data before they launch any customer missions with flapless ships. Also data on re-entry of expendable ships (with no control surfaces) for safe disposal.

So if S26 makes it out of the atmosphere in one piece, they could call it a success on that basis.

Also I could point out that when S26 began production, they didn't know S24 would make it through Max-Q, so they might have wanted an alternative (to get orbital development started) in case the flaps needed a redesign the same way staging ultimately did.

As for a HLS mockup... I wouldn't have expected raptors and a static fire for a mockup

[ThatOldJanxSpirit]

This should be the first orbital flight. As well as tank transfer they could use it to validate thermal models, rcs gas usage, and engine re start.

[OTV Booster]

Does anybody remember is S26 has a nose header tank?


If it launches they can't expect it to do EDL, so the header can be empty. A little added plumbing and it could well be for testing in ship propellant transfer. Then it's available for testing EDD (Entry, Descent & Destruction)


Alternatively, it could be used for FTS testing. Lack of tiles & fins shouldn't matter for this.

[Okie_Steve]

In addition to all of the above they might want to explore longer term on-orbit behavior with tankers in mind. It would probably take some sort of radiator and additional electrical source such as Dragon Trunk style solar cells, an APU or maybe a fuel cell. Not real likely I suspect but doable with more or less existing technologies.

[Nevyn72]

Didn't ship 26 get a Pez dispenser and working payload door?

Maybe it's time to try launching some Starlink V2 full size sats...

[edzieba]

Didn't ship 26 get a Pez dispenser and working payload door?

No, it did not. It doens't even have the cutout in the tank skin.

[StarshipTrooper]

Not discounting potential on-orbit uses for S26, but I want to point out that S26 will be the first time they get any aerodynamic data on expendable / flapless ships above 10 km. They're gonna want that data before they launch any customer missions with flapless ships. Also data on re-entry of expendable ships (with no control surfaces) for safe disposal.

If the intention of the flight was aerodynamic data, wouldn't it being half covered with tile pegs affect the data? It certainly wouldn't be clean.

[OTV Booster]

In addition to all of the above they might want to explore longer term on-orbit behavior with tankers in mind. It would probably take some sort of radiator and additional electrical source such as Dragon Trunk style solar cells, an APU or maybe a fuel cell. Not real likely I suspect but doable with more or less existing technologies.

Good point. We had a lot of LEO tank thermo modeling in the Refueling thread but IMO they had too many unsubstantiated assumptions. SX probably has tighter assumptions but long duration behavior is most likely on their todo list.


Fuel cells or APU would be a longer reach than photo cells or even a load of batteries for ballast. If the goal is to characterize the tank thermo behavior, a radiator would muddy things. Maybe.

[DanClemmensen]

In addition to all of the above they might want to explore longer term on-orbit behavior with tankers in mind. It would probably take some sort of radiator and additional electrical source such as Dragon Trunk style solar cells, an APU or maybe a fuel cell. Not real likely I suspect but doable with more or less existing technologies.

My guess: no, S26 will not try for anything fancy. It serves as a cheap SS for reaching orbit, cryotransfer test, controlled reentry, and nothing else. It's obsolete and we have no evidence of any additional fancy features.

[OTV Booster]

In addition to all of the above they might want to explore longer term on-orbit behavior with tankers in mind. It would probably take some sort of radiator and additional electrical source such as Dragon Trunk style solar cells, an APU or maybe a fuel cell. Not real likely I suspect but doable with more or less existing technologies.

My guess: no, S26 will not try for anything fancy. It serves as a cheap SS for reaching orbit, cryotransfer test, controlled reentry, and nothing else. It's obsolete and we have no evidence of any additional fancy features.

All they really need for a baseline on tank behavior is some extended time on orbit with some leftover propellant. To extend orbit time all they need is RCS and electricity.


A rotisserie rotation minimizes the RCS requirements. The thermal environment might keep the tanks pressurized, keeping cold gas RCS available as long as the methane lasts. Worst case, there are COPVs and/or electricity to vaporize propellant.


Batteries would do for electrical. As a WAG I'd say that somewhere between three days and a week would tell them everything they need to know about tank thermal properties. They'd still be free to do a propellant transfer and EDL test.


The closest it would come to fancy would be a large battery pack and maybe some extra RCS gas. It also has its own logic. The ship is built as we've envisioned a depot and a depot relies on propellant transfer and knowledge of tank thermal characteristics. If they name it the SS Shelby I'll go to sleep with a smile.

[Keldor]

I suspect that S26 is a backup in case S25 fails during the ascent.  Being stripped of reentry equipment made it fast to manufacture, so that they would be able to return to flight and test ascent issues sooner than later.  Of course, the pad failure on the first flight probably delayed things far enough that S26 is no longer relevant, but such is life.

If S25 reaches orbit successfully, I would expect S26 to be scrapped.

[OTV Booster]

I suspect that S26 is a backup in case S25 fails during the ascent.  Being stripped of reentry equipment made it fast to manufacture, so that they would be able to return to flight and test ascent issues sooner than later.  Of course, the pad failure on the first flight probably delayed things far enough that S26 is no longer relevant, but such is life.

If S25 reaches orbit successfully, I would expect S26 to be scrapped.

A backup for S25 it may be but if so, it'd be force of circumstances.


IIRC, they stripped the tiles off 26 and left the pins. It looks as if they had a specific offbeat use intended when they did that. Maybe that use dropped out of the plans but we have no info either way.


Isn't there another ship almost ready to go?

[Barley]

I suspect that S26 is a backup in case S25 fails during the ascent.

Is "backup" appropriate for rapid prototyping and testing?  Every test is unique depending on what you have learned so far and what you think you can do.  Even if you lose a mission to an external event like a hurricane you probably learn something through the passage of time, and would rarely want a repeat mission.   For example the test of the flip separation was never done but no backup is being run.

[edzieba]

I suspect that S26 is a backup in case S25 fails during the ascent.

Is "backup" appropriate for rapid prototyping and testing?

Yes, as we have seen in the past with ships being mothballed & scrapped after successful tests. Since many of SpaceX's changes break compatibility (between Ship and Booster, between Ship or booster and GSE, with handling equipment or assembly processes, etc) then having 'duplicates' with the same compatibility means that random non-flight-related failures - for example, a crane rolls into a vehicle and pokes a hole in a tank, or a lifting strap fails and drops a vehicle, etc - you have a backup to achieve test objectives without a significant delay. It also means that in the event of a software-related issue you have a hardware twin to make a re-attempt with, or at the very least test with.

[catdlr]

https://twitter.com/kmreed/status/1860115503601320078

Kevin Michael Reed
@kmreed
Our farewell to Ship 26.
#Ship26FanClub
#Ship26IsForever

Video by
@NASASpaceflight
 Contributors / Edited by @thenasaman
  / Music by @sunomusic
 / Inspiration by @SpaceX
,
@elonmusk
 and the NSF Ship 26 Fan Club. / Produced by me.