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SpaceX Plan To Fuel Rockets With People Aboard Raises Alarm Bells (fortune.com)
Several space industry experts that advise NASA have told the US space agency there are safety risks in a proposal by Elon Musk's SpaceX to fuel its rockets while astronauts are on board. From a report on Fortune: "This is a hazardous operation," Space Station Advisory Committee Chairman Thomas Stafford, a former NASA astronaut and retired Air Force general, said during a conference call on Monday. Stafford said the group's concerns were heightened after an explosion of an unmanned SpaceX rocket while it was being fueled on Sept. 1. The causes of that explosion are still under investigation. Members of the eight-member group, which includes veterans of NASA's Gemini, Apollo and space shuttle programs noted that all previous rockets that have flown people into space were fueled before astronauts got to the launch pad. "It was unanimous ... Everybody there, and particularly the people who had experience over the years, said nobody is ever near the pad when they fuel a booster," Stafford said, referring to an earlier briefing the group had about SpaceX's proposed fueling procedure.
SpaceX is using densified (highly cooled) LOX to increase peformance by cramming more fuel into the same-sized tank. That super-cooled LOX will only sit in the tank for so long before it starts to warm up and expand, so for best performance they need to be fueling up until just a few minutes before launch.
Probably the Falcon 9 could still lift the Dragon without supercooled LOX, but it would have lower launch margins.
NASA may have done the bulk of the fueling before loading astronauts, but they kept topping up the tanks against boil-off right up until a few minutes before launch, so there's a bit of an exaggeration here.
Too bad the payload on that last rocket didn't have the Dragon escape system, to provide some real world data. Has any escape system ever deployed in practice?
Soyuz 7K-ST in 1983. Its launch escape system saved the crew; the rocket blew up on the launch pad.
Especially when there's no fucking reason to fuel up while crew are aboard.
Actually there are a number of reasons to fuel right before launch, some specific to SpaceX/Falcon 9 and some in practice.
1) If you fuel the rocket you have a lot of people that are working in and around the rocket when it's in a hazardous state for a long period of time, with no means of escape. Think of all the technicians in the white-room who are strapping the astronauts into the capsule etc... The astronauts, when strapped into the capsule, have a good escape system that will get them away from the fireball.
2) In the old days, it did take hours to load propellant into the rocket, and having your astronauts strapped into their seats that long was lunacy. With the Falcon 9, that process is down to 40 minutes.
3) The Falcon 9 requires this. The design as it stands depends on sub-chilled propellants to achieve the required performance. This means that the rocket can't sit for long on the pad fully loaded, certainly not long enough to strap in the astronauts.
All in all, with the way that the Falcon 9 works, and the reliability of the launch escape system, it's actually safer to load the propellants when the astronauts are already packed in.
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