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Elon Musk appeared on CNBC and offered a definitive explanation for his company's recent launch explosion:
SpaceX CEO Elon Musk says that his company has finally gotten to the bottom of the September 1st Falcon 9 explosion — claiming it was the "toughest puzzle" they've ever had to solve. And now that the problem is known, he expects SpaceX to return to flight in mid-December.
Speaking on CNBC yesterday, Musk said "it basically involves liquid helium, advanced carbon fiber composites, and solid oxygen. Oxygen so cold that it actually enters solid phase." So what does that mean exactly? Musk gave some hints a little while ago during a speech he gave to the National Reconnaissance Office. According to a transcript received by Space News, he argued that the supercooled liquid oxygen that SpaceX uses as propellant actually became so cold that it turned into a solid. And that's not supposed to happen.
This solid oxygen may have had a bad reaction with another piece of hardware — one of the vehicle's liquid helium pressure vessels. Three of these vessels sit inside the upper oxygen tank that holds the supercooled liquid oxygen propellant. They're responsible for filling and pressurizing the empty space that's left when the propellant leaves the tank. The vessels are also over wrapped with a carbon fiber composite material. The solid oxygen that formed could have ignited with the carbon, causing the explosion that destroyed the rocket.
Musk called the issue one that had "never been encountered before in the history of rocketry." One of SpaceX's customers, Inmarsat, may find an alternative for one of its upcoming satellite launches. SpaceX launches could resume mid-December.
For comparison's sake, at standard pressure:
- Liquid Helium: 4 K (about −269 °C or −452.2 °F).
- Solid Oxygen: 54.36 K (−218.79 °C, −361.82 °F).
- Solid Nitrogen: 63.15 K (−210.00 °C, −346.00 °F)
- Liquid Nitrogen: 77.355 K (−195.795 °C, −320.431 °F)
- Liquid Oxygen: 90.19 K (−182.96 °C; −297.33 °F)
- Dry Ice (Solid CO2): 194.65 K (−78.5 °C; −109.3 °F).
(Score: 2) by ledow on Monday November 07 2016, @08:18PM
Good links.
"I'd be surprised if this is the first time someone blew up a carbon fiber tank with liq O2."
In which case, why would you try it?
(Score: 2) by VLM on Monday November 07 2016, @10:30PM
I should have searched NTRS before even posting.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010020209.pdf [nasa.gov]
To summarize our tax dollars at work, it takes some effort to blow up liq O2 and carbon fiber, but it most certainly can be done and the paper was full of wiggle words about if theres no source of ignition energy (like a helium tank banging the hell around inside it) then it should probably behave most of the time.
Also they didn't test solid O2 and generally nice dense solid O2 was more of a headache for the explosives.
So... Liq O2 by itself doesn't spontaneously cook off, but solid O2 with a tank in the middle being Fed with is less healthy.
Waaaay back when it blew up there was some talk from spacex about it all being an operational procedure thing, so yeah, just don't make an O2 slushie and let the liq helium sit there for hours beforehand.
I donno if you can man-rate a rocket with slush O2 and a CF helium tank inside it... even if operationally you're really careful about not slushing the tank more or less.