FAA closes investigations into Blue Origin landing fail, Starship Flight 7 explosion The US Federal Aviation Administration (FAA) is closing its investigations into both the SpaceX Starship Flight 7 explosion and Blue Origin New Glenn-1 landing failure. The causes of the Starship Flight 7's "rapid unscheduled disassembly" in January this year are well documented. In a nutshell, there were stronger-than- …
Pump-fed rocket engines really dislike air bubbles. Turbo pumps have a tendency to detonate if they're fed air bubbles. This makes it not so much an engine issue, but a propellant issue and might require some redesign of the rocket to be able to settle the fuel and oxidizer as well as purge air from the system before trying to relight engines. Way back, SpaceX released some video from inside one of the propellant tanks and you can see how the liquid becomes a volume of globules which is a big problem. Since Lox and liquid CH4 are too cold to use a rubber bladder, another way must be found that works reliably and doesn't add too much mass.
Yep, and that's why the centre engines keep burning at stage separation so the booster doesn't get into free-fall before the boost-back burn starts, with cold-gas thrusters being used to keep it on track when it is coasting to re-entry. The re-entry burn happens when there is enough deceleration for the tanks to have settled.
"Yep, and that's why the centre engines keep burning at stage separation so the booster doesn't get into free-fall before the boost-back burn starts, "
That means there will be mitigation needed so the booster isn't damaged during the hot stage such as a staging ring. A rocket engine is a mighty blow-torch.
"Though, during the re-entry and landing phases, the booster will be decelerating due to atmospheric drag and the propellant should be at the bottom of the tanks."
The design of the New Sheppard booster is very clever in the way that the aerodynamics work one way going up (nice and sleek) and provide drag from the top of the airframe coming down. I'm surprised there isn't more of that approach with New Glenn. Boosting back cross-range is an issue, but perhaps that could be accomplished from smaller pressure fed engines until the booster is back in enough atmosphere to fire the main engines. It puts limits on cross-range returns, but could remove risk. Even a small dedicated propellant settling engine could be useful.
Aerodynamics for New Shepherd are virtually useless for any orbital class vehicle. NS goes up vertically and comes pretty much straight back down to the same stop. There is no horizontal velocity which is what you need to go orbital. In order to maintain stability with engine down orientation so retro burn to slow down can do its job requires grid fins or aero surfaces.
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Apparently, as they make it bigger they need to make it lighter otherwise you need more fuel to lift the structure and the extra fuel you put in, so even though flight 8 had a lighter payload since it was bigger the vibration issue remains. Making it sturdier will reduce the payload size so much that there is actually a negative payoff.
They also said that they haven't done any test flights with scale models which would have revealed these issues, but they are now so embedded into NASA plans that SpaceX can keep sucking the government teat.
They have done several test flights with scale models. It's just that the scale is 1:1. They've chosen that scale to avoid the issues that smaller scales produce, like not having parts that fit and that mass doesn't scale the same as length or volume.
Not entirely true, the whole point of Block2 and eventually Block3 starship is that Raptor 3 engines have a lot more thrust (And have less mass) than the Raptor 2 currently in use. Thus they could increase ship size without losing mass to orbit. Raptor 3 is apparently not yet available in sufficient quantity so they've been using Raptor 2 for Block 2-ish starships used in flight 7 and 8. The bigger problem that I see is that they apparently had in flight structural oscillation problems on flight 7 and they thought they could test those by doing differing levels of thrust on a static fire. Which completely ignores that a free-flying body is going to behave completely differently than one clamped down from the thrust bearing structure at the bottom end to a test stand. They simply couldn't test the issues they had with Flight 7 (if indeed it was destructive oscillations) that way and ANY engineer worth their salt should have been able to tell them that.
If the problem is resonance, a scale model would not have revealed it. Hopefully they can alter the shape enough for it to not resonate with whatever frequencies are hitting it, without adding too much mass.
Or maybe Starship will never work. If that is the case, how else will we get hundreds of tons to the lunar surface?
I don't know which 'rocket scientist' you are referring to but I am guessing they don't work for SpaceX.
You either need to make it lighter or you make it more powerful and add more fuel. SpaceX have Raptor 3 coming which adds more power. There are some reports saying Block 3 may have 35 engines as well.
We have no idea what they will do to resolve the issues, its not always about making it sturdier, you really need to understand what is causing the issues. The solution might not be making the stage stiffer.
Scale testing, very time consuming and expensive. You would be designing a different rocket, how do you scale down a raptor do you can still fit 6 of them. If you use a different engine then is that a good test ? Remember before block 2, it looked like SpaceX had cracked the ascent portion of the flight.
As for government teat, they have one contract and that is for HLS and its fixed price so any increase in development cost is at SpaceX dime.
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