Launch News SpaceX SN10

[Marijn]

The speed at touchdown was too high. I think that's what caused the landing gear to fail and possibly also the leak.

 

[Sunhillow]

The speed at touchdown was too high. I think that's what caused the landing gear to fail and possibly also the leak.

At least two of the tiny legs were flapping mid-air instead of being locked in vertical position. Also I think their spring excursion should be increased.

 

[N_Molson]

unless you invest into a airport fire engine like robot.

They'll have to anyways if they want to do anything beyond engineering tests with those rocket-zeppelins, if they plan to put someone alive inside it will require a super-ready army of robot firefighters to secure the landing in CO2 foam, even when nominal, just in case. But again even that might not be enough to fight a LOX-fueled fire, because as soon LOX evaporates any spark will start a self-sustaining inferno. And those rockets are tall, the crew couldn't like jump and run.

 

[Urwumpe]

They'll have to anyways if they want to do anything beyond engineering tests with those rocket-zeppelins, if they plan to put someone alive inside it will require a super-ready army of robot firefighters to secure the landing in CO2 foam, even when nominal, just in case. But again even that might not be enough to fight a LOX-fueled fire, because as soon LOX evaporates any spark will start a self-sustaining inferno. And those rockets are tall, the crew couldn't like jump and run.

Well, I think first of all, they should prevent fires. Right now, the engine shut-offs are massive fire hazards because they vent lots of unburned gases in the process. For landing on Earth, there should be better a system to purge the engines with enough force from those gases in a short time.

 

[N_Molson]

For landing on Earth, there should be better a system to purge the engines with enough force from those gases in a short time.

Which means generous Helium or Nitrogen tanks, which means taller and heavier rockets because even liquefied those gases take some volume.

 

[Urwumpe]

Which means generous Helium or Nitrogen tanks, which means taller and heavier rockets because even liquefied those gases take some volume.

And? It is sure cheaper than needing a few new astronauts.

 

[Marijn]

At least two of the tiny legs were flapping mid-air

Indeed. A̶s̶ ̶i̶f̶ ̶t̶w̶o̶ ̶s̶y̶s̶t̶e̶m̶s̶ ̶a̶r̶e̶ ̶f̶i̶g̶h̶t̶i̶n̶g̶ ̶e̶a̶c̶h̶ ̶o̶t̶h̶e̶r̶ ̶a̶n̶d̶ ̶d̶e̶p̶l̶o̶y̶i̶n̶g̶ ̶a̶n̶d̶ ̶r̶e̶t̶r̶a̶c̶t̶i̶n̶g̶ ̶t̶h̶e̶ ̶g̶e̶a̶r̶.̶ Not sure what to think of such problems at this stage.

It seems to me this new problem, possibly, also the leak problem, come on top of the touchdown which cannot be called a success yet imo.

 

[APDAF]

Apparently three landings legs didn't lock correctly atleast according to Scott Manley
Also the "explosion" seems to mostly be pressure related and not an uncontroled combustion.

 

[N_Molson]

With all the respect I have for Scott Manley he is quite an self-proclaimed expert... I'd be cautious.

 

[Urwumpe]

With all the respect I have for Scott Manley he is quite an self-proclaimed expert... I'd be cautious.

AFAIR he has an engineering background, so at least not the worst expert to pick.

Also, if all experts would have that competence that he shows in his videos, this planet would be much better.

 

[Marijn]

I'd be cautious.

Everyone is speculating. I think there is essentially nothing wrong with that. It was a test flight. Not an accident where a process of truth-seeking would be started. As far as I am aware, SpaceX can say whatever they want about this flight, including lies to discourage competitors's from copying their concept and learning from their mistakes. Right? I think any exchange of information with the FAA is confidential.

 

[Thunder Chicken]

For the money it's probably cheaper and safer to have a damaged prototype Starship just self-immolate and collapse on the pad, especially if it has damaged fuel plumbing. After the landing and before the explosion I wasn't envying any of the riggers that would have had to try to recover that teetering mess. Bulldoze it off the pad and set up SN11.

When it gets operational, they will have hopefully had many interesting and informative failures and RUDs that will guide their decisions on ground handling equipment and safety systems to invest in.

 

[N_Molson]

Interesting video on mess cleaning :

The engines themselves don't look that bad. The nozzles are completely "pinched".

Also for those interested in engineering, this is quite an interesting "autopsy".

 

[Thunder Chicken]

Interesting video on mess cleaning :

The engines themselves don't look that bad. The nozzles are completely "pinched".

Also for those interested in engineering, this is quite an interesting "autopsy".

Keeping the Jawas busy down in Texas

 

[4throck]

Musk tweet (

https://twitter.com/i/web/status/1368016384458858500

):
"Thrust was low despite being commanded high for reasons unknown at present, hence hard touchdown. We’ve never seen this before. Next time, min two engines all the way to the ground & restart engine 3 if engine 1 or 2 have issues."

It shows that the after the flip they are encountering unforeseen conditions and just guessing.
On each flight the engines seem to perform differently and there are always some issues...
Good part is that they are changing the landing Autopilot to take this into account. It's an interesting approach.

Yet I think that test conditions need to be simpler in order to isolate the problem.
I'd go back to short straight up / down flights to nail down engine relights and landing legs.

 

[GLS]

Good part is that they are changing the landing Autopilot to take this into account. It's an interesting approach.

No, that's basic testing: try-> learn -> change -> try -> learn -> change -> try.... until it does what you want.

 

[Arvil]

Or as we said in lean manufacturing . . .Plan, Do, Check, Act . . .

 

[Thunder Chicken]

Yet I think that test conditions need to be simpler in order to isolate the problem.
I'd go back to short straight up / down flights to nail down engine relights and landing legs.

This method only works if the issue occurs in simpler test conditions. They flew (and did not explode) the Starhoppers looking at these simple conditions. The problems they are having now are because they have an extremely dynamic flight profile, fuel sloshing all about, and they are trying to get reliable shut down and relight on all the engines without using a TEA/TEB system.

What they are doing is hella hard and they need to get it ALL to work together in actual flight conditions. Best way to do that is to keep launching rockets and data gathering until the explosions stop. They ARE doing the simplest test for this now.

 

[N_Molson]

The question is more : can it be done with the tech they have ?

 

[Urwumpe]

The question is more : can it be done with the tech they have ?

Well, the layman in me wants to say no, that is FAR, FAR away from what was ever done before and usually avoided at all costs.

But, the systems engineer in me says: Its just a few constraints more, some more requirements in certain situations and nothing that suggests that these requirements contradict each other or might do so in further iterations. Hell, even the fuel combination used has so many favorable properties to solve the problem, that it should be no showstopper.

It MUST be possible with current tech.

Also, I don't think igniting the engines is the problem, because they seem to have worked it out with brute force. A more elegant solution might be including closed-loop control over the engine already early during ignition, instead of the transition to main stage - but that requires flight test data. Brute force is fine for that now.

The main problem they have IMHO is shutting those engines off in a safe way. Its way easier with gas generator cycle engines, with full flow staged combustion, you need to stop the full flow - which can't be done suddenly without killing the engine. I think this could end in a redesign of the Raptor engine. They need to keep the engine cooled without venting methane - so one half of the engine would need to be capable of switching into a limited gas generator-cycle operation without venting methane rich exhaust into the main combustion chamber or the world around the engines. Or additional pumps take over - for example, how painful would it be, to add a small gas generator and turbine to the fuel pump shaft, to permit pumping methane at reduced flow rates and/or pressure until the engine has safely reached the parameters that can permit a full cutoff? This wouldn't need to be very heavy or long-lasting, since we talk about <10 seconds until the engine is really cold (and not a fire-hazard until ignition).

Maybe such a solution is heavier, but simpler to implement as further reducing the minimum throttle settings of the gas generator.

Also, a method of inerting the chamber after each shutdown is needed. Without, moisture could freeze into ice INSIDE the engine and make reignition more dangerous.