SpaceX launches Starship Flight 9 to space in historic reuse of giant megarocket (video)

[Admin]

SpaceX's Starship megarocket launched on its ninth-ever test flight today (May 27), an important mission that aimed to break a two-flight upper-stage failure streak.

SpaceX launches Starship Flight 9 to space in historic reuse of giant megarocket (video) : Read more

 

[Unclear Engineer]

Well, they did manage to get to upper stage engine shutoff without a leak causing an explosion.

But, while coasting in space, the upper stage did develop a leak that caused the stage to spin/tumble, which still caused the destruction of the ship and prevented getting data on the Raptor engine restart in space and all of the data on the heat shield during reentry and the flight dynamics with the new flap design and location.

So, in my opinion, a disappointment that SpaceX seems to have taken a step backward on the upper stage between flight 6 and 7, with repeated leaks causing failures that had not previously occurred on fights 4, 5 and 6.

I am wondering what is going on with these leaks. Did the manufacturing process change in some way between the ships for flights 6 and 7?

 

[contrarian]

Is SpaceX's Starship methane fuel a problem with all these failures?

Google AI tell us that "Methane, when mixed with liquid oxygen, can be prone to leaks and fires, especially if the system isn't designed robustly." No doubt they are trying a "robust" system, but the results are not looking too good.

Perhaps they should be looking at Rocketdyne's engines or equivalent. The Saturn V, using their F-1s, never had a launch failure in 13 launches, and it was burning RP-1 and LOX.

Don't know enough about this to make a call.

 

[Classical Motion]

Every flight and every failure instructs them how to re-tune. Once they find the proper tune, they will sing. He has several good tunes now. With other songs.

There is persistence(Edison) and there is genius(Tesla), having both is a real advantage.

Lots of failure means lots of learning.

 

[contrarian]

Lots of failure means lots of learning.

The Saturn V had no failures on its learning curve.

Just now reading that the second and third stages of the Saturn V burned H2 and LOX.

The Starship burns methane and LOX on all stages, and is apparently on a steep learning curve. The last three failures are largely attributed to fuel leaks.

 

[Unclear Engineer]

First, liquid propane methane is much easier to deal with than liquid hydrogen. It isn't much harder to deal with then liquid oxygen.

Second, the flights 4, 5 and 6 did not have these leak problems and successfully reentered and effectively "landed" at the ocean water's surface.

So, this looks like some sort of fabrication or maybe hardware design problem, not a basic design or conceptual problem.

The odds of it happening are now 0.5 for the last 6 flights. But, they are distributed as 3 successes followed by 3 failures. The odds of that sequence happening if nothing changed for all 6 flights is only 1 in 64. But, if something changed between flights 6 and 7 to increase the probability of failure, that increases the odds of getting the 3 failures following 3 successes. For example, if the failure probability only doubled, say from 1/3 to 2/3, then the odds of seeing this sequence would become about 1 in 11. Bigger increases in the probability of failure between flights 6 and 7 give even better odds for seeing this sequence. That is why I (and probably SpaceX) think this is being caused by some change they made between those 2 flights.

 

[contrarian]

First, liquid propane is much easier to deal with than liquid hydrogen. It isn't much harder to deal with then liquid oxygen.

It actually burns liquid methane, which is very cryogenic and much more difficult to handle than propane.

Also of concern are those 33 engines with the first stage. The more engines, the greater the risk of failure due to defects. The Saturn V had only five engines, without a single failure.

It is noted their Falcon 9 rocket uses the same fuels as the Saturn V, and only 9 engines, and has a success rate of >99% on around 500 launches. Time will tell if they can make these Starships reliable, or revise the basics.

 

[Unclear Engineer]

I don't understand how the previous post said "propane" when I intended and think I did write "methane".

Anyway, the statements in my previous post are correct for liquid methane.

As for the 33 rocket motors on SuperHeavy, that actually increases vehicle reliability, because it can still meet its mission goals with even a few engines prematurely shut down. Some of the testing being done is already looking at flight parameters with some engines our of service. Same for the heat shield, which is not planned to be replaced after every flight.

 

[contrarian]

I don't understand how the previous post said "propane" when I intended and think I did write "methane".

Anyway, the statements in my previous post are correct for liquid methane.

As for the 33 rocket motors on SuperHeavy, that actually increases vehicle reliability, because it can still meet its mission goals with even a few engines prematurely shut down. Some of the testing being done is already looking at flight parameters with some engines our of service. Same for the heat shield, which is not planned to be replaced after every flight.

I understand your mistake. It happens to me from time to time, sadly..........

And I understand the use of so many engines. But it makes for a much more complex assembly, which may be why they are having so much trouble. It is established that fuel leaks are the primary cause of the last three failures.

To be honest, I was not sure how reliable the Falcon 9 is. Quite remarkable. And it does not burn methane!

 

[Unclear Engineer]

The leak problems are in the second stage, which has 6 engines. That is only one more than the Saturn 5 1st stage that you keep citing.

Liquid methane boils at -259 F, and liquid oxygen boils at -297 F. so, those 2 are much more similar in temperature in spacecraft propellant tanks than RP1 which is liquid at normal temperatures or liquid hydrogen, which boils at -423 F.

So, I am just not seeing that using methane is the basic reason for having leakage problems in the second stage plumbing.

 

[contrarian]

So, I am just not seeing that using methane is the basic reason for having leakage problems in the second stage plumbing.

One possible reason is a hardware problem in one of the engines may have caused excessive "harmonic response" in the upper stage. This apparently resulted in stress on the engine structures, leading to a propellant leak in the attic, which lead to failure of this stage. In the final analysis, a propellant leak was at fault.

I can't help but recall the concerns that using methane requires very robust hardware. It seems likely a number of issues caused the last three failures, but all ultimately related to fuel leaks, or so I am reading.

They need to do some serious evaluations of these issues in order to proceed.