SpaceX concluded that it was a bad strut while NASA and the FAA never reached the same conclusion. The found several issues that fit the available data just as good as the failed strut. So in the eyes of NASA and the FAA, the CRS-7 mission failure is still "unexplained".
Launch News [Sep.1, 2016] Falcon 9 explodes on the Launch Pad
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MaverickSawyer
Acolyte of the Probe
Looks like NASA was right to question the SpaceX conclusion, then. Because that's twice they've blown up the second stage LOX tank from a failed helium system.
Yes and also bad news for SpaceX as this shows that they can't be trusted in their failure analysis and also like to hurry things along at the expense of safety and reliability. For SpaceX the best option now is to make sure everyone agrees on the failure analysis. Otherwise no-one will take them seriously again.
Kyle
Armchair Astronaut
If that's the case then it's pretty ridiculous that they're already saying as soon as November for a RTF. Honestly, if we see a Falcon 9 fly before April I'd be impressed.
GLS
Well-known member
To me it is clear that they are going +/- blind ever since they had a pad shutdown a while back, and within a hour so they changed the offending redline and tried again. :uhh:
Thunder Chicken
Resident Lua Script Rabble-Rouser
Installing the He pressurization tank inside the LOX tank is something that even NASA (IIRC) hasn't tried yet, though they apparently have looked at doing it for Constellation and maybe the SLS:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080009730.pdf
There seems to be very little knowledge of the lifetime of these COPV tanks when pressurized in this sort of temperature environment. I suspect that SpaceX is running into the tail of a poorly-understood failure probability curve of composite materials at cryogenic temperatures - a failure that they extrapolated from limited data to be a 0.00001% probability is actually a 1% or worse probability.
I think everyone must be wondering if CRS-7 was really a strut problem, or the tank was really the problem and they just happened to catch during the investigation that the struts were marginal. Nothing says only one thing can be wrong.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080009730.pdf
There seems to be very little knowledge of the lifetime of these COPV tanks when pressurized in this sort of temperature environment. I suspect that SpaceX is running into the tail of a poorly-understood failure probability curve of composite materials at cryogenic temperatures - a failure that they extrapolated from limited data to be a 0.00001% probability is actually a 1% or worse probability.
I think everyone must be wondering if CRS-7 was really a strut problem, or the tank was really the problem and they just happened to catch during the investigation that the struts were marginal. Nothing says only one thing can be wrong.
Urwumpe
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Which material was used for previous Helium bottles in rocket tanks? The Saturn V for example also had most of its Helium stored inside the tanks, which is the natural way to go since the outside wall of a rocket is the tank wall and only the limited intertank space could otherwise be used for storing helium.
RGClark
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Anyone know if these problems with the helium pressurization system coincided with SpaceX going with supercooled propellant or did they happen before?
Bob Clark
---------- Post added at 03:51 AM ---------- Previous post was at 03:32 AM ----------
Yes. That report Thunder Chicken cited on determining the effectiveness of helium bottles using composites must have been written because it was uncertain of their effectiveness at cryogenic temperatures.
Helium bottles were kept inside the LOX tank of the Saturn V first stage but were made of aluminum:
SP-4206 Stages to Saturn.
7. The Lower Stages: S-IC and S-II.
During the countdown, pressurization was supplied by a ground source, but during flight, a helium pressurant was supplied from elongated bottles stored, not on the fuel tank, but submerged in the liquid oxygen (LOX) tank. In this medium, the liquid helium in the bottles was in a much more compatible environment, because the cold temperature of the liquid helium containers could have frozen the RP-1 fuel. There were additional advantages to their location in the colder LOX tank. Immersed in liquid oxygen, the cryogenic effect on the aluminum bottles allowed them to be charged to higher pressures. They were also lighter, because the cryogenic environment permitted manufacture of the helium bottles with one-half the wall thickness of a noncryogenic bottle. Produced by the Martin Company, the four helium bottles, 6 meters long and 56 centimeters in diameter, were aluminum extensions of unique length. Ducts carried the cooling helium down through heat exchangers on the F-1 engines, then carried heated, expanded gaseous helium back to the top of the fuel tank for ullage pressure.
http://history.nasa.gov/SP-4206/ch7.htm
Bob Clark
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Thunder Chicken
Resident Lua Script Rabble-Rouser
CRS-7 was a Falcon 9 v1.1, but AMOS-6 was a Falcon 9 FT.
Col_Klonk
Member
RGClark... I wouldn't cite/assume anything from the Apollo moon program while NASA has the means to prove it, but refuses to do so.
Col_Klonk
Member
Well .. when you hear how great the Saturn V F1s were.. and all you hear nowdays at launch sites.. RD-this RD-that RDs-everywhere...... Oh yes... :thumbup:
We all know the shuttle didn't use a F1, or next generation engine.... we all know the F1 engineering details were misteriously misplaced :thumbup:
We all know the shuttle didn't use a F1, or next generation engine.... we all know the F1 engineering details were misteriously misplaced :thumbup:
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Col_Klonk
Member
New engines.. no problem.
Back to RGClarks reference
Back to RGClarks reference
Urwumpe
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New engines.. no problem.
Back to RGClarks reference
I would not call the RS-25 new. Or the RS-68. Well, maybe the AJ-26.
Also.... The F-1A engine had been used in MANY scientific papers in the recent decades, without flying... NASA still used it in research.
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Col_Klonk
Member
What's the latest resolution of the moon that we're (as in hi-tech) capable of ?
Andy44
owner: Oil Creek Astronautix
How does this question relate to the Falcon 9 accident?
Notebook
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Generic question, sort of.
I understand the strong-back is there to support the various tanks before they are pressurised?
Any reason they don't use the longtitudinal tension system as in Blue Streak?
http://i89.photobucket.com/albums/k207/Notebook_04/Blue Streak/File0031.jpg
N.
I understand the strong-back is there to support the various tanks before they are pressurised?
Any reason they don't use the longtitudinal tension system as in Blue Streak?
http://i89.photobucket.com/albums/k207/Notebook_04/Blue Streak/File0031.jpg
N.
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