SpaceX Pressure Hammers Stuck Valves; Dragon's ISS Mission Back On Track 170
SpaceX's Dragon launch to the ISS earlier today went off smoothly, but the mission encountered trouble shortly after: three sets (of four) of the craft's maneuvering thrusters didn't work. CNET quotes SpaceX founder Elon Musk: "It looks like there was potentially some blockage in the oxidizer pressurization (system). It looks like we've been able to free that blockage, or maybe a stuck valve. We've been able to free that up by cycling the valves, essentially pressure hammering the valves, to get that to loosen. It looks like that's been effective.
All the oxidizer tanks are now holding the target pressure on all four (thruster) pods. I'm optimistic we'll be able to bring all four of them up and then we'll work closely with NASA to figure out what the next step is for rendezvousing with space station," and follows up with the good news that
"Shortly after the briefing concluded, engineers reported all four sets of thrusters were back on line and that testing was underway to verify the health of the system." Barring further problems, Dragon could reach the ISS as soon as Sunday.
Re:What is the worst that could happen (Score:5, Informative)
I don't know the details of this system, but pressurisation valves probably open once and... that's it. Typically you want the thruster tanks unpressurised until orbit and pressurised from there until the end of the mission.
The good news is that, because they'll get the Dragon back, they should be able to dismantle the thrusters on Earth and find out why they didn't work properly.
Re:What is the worst that could happen (Score:5, Informative)
Re:LOX Valve Icing Stikes Again? (Score:5, Informative)
Dracos use hydrazine and nitrogen tetroxide. No cryo.
Re:My iPod has a great battery life (Score:4, Informative)
Re:What is the worst that could happen (Score:4, Informative)
I'd say down voted because people here haven't a clue about how NASA deals with things concerning the ISS. If you believe they have given any sort of green light on docking then you are greatly mistaken. $20B+ dollars, 10+ years making, and no room for error they will take no chances over a little more than half a ton of cargo. I've been in meetings and seen them pontificate of completely benign things for a week. They take nothing more seriously than the safe being of the ISS. I'm not saying they won't give it a go, but I would be shocked if they have already given SpaceX the go ahead. Not saying they aren't planning, but I will say there are a lot of people who have some decisions to make and they wo't be done lightly.
Yeah, it's actually more like $100-200 billions depending on how you count, or about the cost of ten to twenty Large Hadron Colliders. And there are six people on board who would have to try to make an emergency escape if something went terribly wrong, so I would imagine everyone involved takes it rather seriously, including SpaceX. SpaceX would become pariahs in the space industry if their hardware did major damage to the ISS or if someone died.
Re:LOX Valve Icing Stikes Again? (Score:5, Informative)
He's AC so won't see your question, so I'll answer.
TVAC: Thermal Vacuum
NASA: National Aeronautics and Space Administration
COTS: Commercial Off The Shelf
LOX: Liquid Oxygen
Re:Why can't they make valves that don't stick? (Score:5, Informative)
The problem is with what you are using the valves for. Holding back dangerous things like Hydrogen and hypergols require very low leak rates when closed. You don't want to work around these things if they have a potential to leak. If you worked around the Space Shuttle on every RCS (Hypergol Thruster) nozzle there was a cover that had a desiccant pack that would absorb any leaks and turn color to indicate a leak. It's a giant pain in the ass to work with this stuff.
When you make valves that can close this tight they sometimes get stuck. Also with spaceflight you need to optimize mass so you can't put a huge valve on everything or it will add up quickly. One thing some satellites do is use a pyrotechnic burst disk right off the tank. This was it stays perfectly sealed until you blow the disk. This is a problem with reusable crafts because you would have to replace them every flight.