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Loiter time on orbit of Dragon
I see they are bringing Dragon down quite quickly compared to other cargo
delivery craft, and I wondered if this was just due to it being an early test flight, or whether there is an issue over prolonged time on orbit. Brian -- -- From the sofa of Brian Gaff - Blind user, so no pictures please! |
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Loiter time on orbit of Dragon
"Brian Gaff" writes:
I see they are bringing Dragon down quite quickly compared to other cargo delivery craft, and I wondered if this was just due to it being an early test flight, or whether there is an issue over prolonged time on orbit. Sane thing to do with a craft that never was in orbit for longer than a few hours before. Dragon has lots of hypergolic fuels on board, lots of valves and plumbing... You certainly don't want it do develop a leak somewhere or a connector corroding while docked to the ISS. Getting it down as soon as it has done its job at the ISS and going over it with a fine comb afterwards is just sensible I'd say. Jochem -- "A designer knows he has arrived at perfection not when there is no longer anything to add, but when there is no longer anything to take away." - Antoine de Saint-Exupery |
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Loiter time on orbit of Dragon
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Loiter time on orbit of Dragon
JF Mezei writes:
[...] How did the russians arrive at 6 months for Soyuz ? Testing on earth ? Empirical testing on Mir ? Or just mathematical calculations ? It's actually somewhat longer (around 210-220 days). They have tested it (unmanned) for that long. I've heard several reasons for the lifetime: seals in the propulsion system degrading, and hydrogen peroxide (used for attitude control for the descent module during reentry) decomposing over time. |
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Loiter time on orbit of Dragon
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Loiter time on orbit of Dragon
In article ,
says... In article m, says... Say Dragon had been designed for 6 months in space. Wouldn't they want it to stay long enough to gauge whether they can see any degradation ? Not necessarily. This is only Dragon's second flight! Traditionally, aerospace programs expand the flight envelope in increments. The reasoning is that it's better to get your vehicle back in one piece, so you can inspect it and correct any defects, than it would be to push your luck a bit too far, too early, and get the vehicle back in tiny bits and pieces. Perhaps longevity testing is scheduled for he next flight. How did the russians arrive at 6 months for Soyuz ? Testing on earth ? Empirical testing on Mir ? Or just mathematical calculations ? Soyuz is reportedly limited by the decomposition of the H2O2 used in the descent module's reaction control system. I'm not sure about Progress, but I'm guessing it's limited more by operational issues, like freeing up a docking port for the next Progress that wants to dock. In this respect, all visiting US commercial cargo and crew vehicles will be limited in the same way. Since crews are rotated every six months for Soyuz, it wouldn't surprise me that six months becomes the requirement for a US crewed vehicle as well. Having the same rotation schedule as Soyuz would seem to make planning ISS crew rotations easier. In an online article (see my other post), it said that DragonLab could stay in orbit up to two years, so it would seem that a Dragon could stay docked to ISS for an equal amount of time. Jeff -- " Ares 1 is a prime example of the fact that NASA just can't get it up anymore... and when they can, it doesn't stay up long. " - tinker |
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Loiter time on orbit of Dragon
Brian Gaff presented the following explanation :
I see they are bringing Dragon down quite quickly compared to other cargo delivery craft, and I wondered if this was just due to it being an early test flight, or whether there is an issue over prolonged time on orbit. And it's down (as AE noted in the STS group). From Spaceflight Now: quote THURSDAY, MAY 31, 2012 1549 GMT (11:49 a.m. EDT) SpaceX founder and chief designer Elon Musk just tweeted: "Splashdown successful!! Sending fast boat to Dragon lat/long provided by P3 tracking planes." The recovery team includes a 185-foot barge, an 80-foot crew boat, and two 25-foot fast boats for dispatch to the capsule when it splashes down. /quote and quote THURSDAY, MAY 31, 2012 1820 GMT (2:20 p.m. EDT) Speaking with reporters from SpaceX headquarters in California, Elon Musk says recovery crews are in the process of attaching cables to the Dragon spacecraft to hoist it on the deck of a ship for the trip back to port. Dragon's re-entry and splashdown were very accurate, he said. "It appears as though we were really hitting the bullseye in accuracy, perhaps less than a mile," Musk said. "In baseball terminology, this would be a grand slam," Musk said. "This was bigger success than we had a reasonable right to expect." /quote (P3/submarine jokes elided) http://spaceflightnow.com/falcon9/003/status.html /dps -- Who, me? And what lacuna? |
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