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U.S. astronauts are climbing back into space capsules. Here's how they've improved over the past 50 years
In message
Jeff Findley wrote: This has changed somewhat recently. Reportedly SpaceX is the one who shelved development of Dragon V2 vertical landing. The reasons for this aren't terribly clear, but there are hints from SpaceX that this is because they've decided to change the (Mars) landing mode of their (eventual) Mars vehicle. Also apparently NASA weren't happy about cargo flights being used for testing powered landings. Also, SpaceX is supposed to have a press briefing about the changes in their Mars program sometime this fall. Hopefully we'll get more information then which will allow us to "connect the dots". Elon is giving another presentation at IAC in Adelaide on the 29th, cyrrently due to start talking at 04:30 UTC. Speculation is for a not-quite-so-BFR that can be built in existing SpaceX facilities and which won't require major strengthening of HLC-39A. Anthony |
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U.S. astronauts are climbing back into space capsules. Here's how they've improved over the past 50 years
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U.S. astronauts are climbing back into space capsules. Here's how they've improved over the past 50 years
Anthony Frost wrote:
In message Jeff Findley wrote: This has changed somewhat recently. Reportedly SpaceX is the one who shelved development of Dragon V2 vertical landing. The reasons for this aren't terribly clear, but there are hints from SpaceX that this is because they've decided to change the (Mars) landing mode of their (eventual) Mars vehicle. Also apparently NASA weren't happy about cargo flights being used for testing powered landings. Why would they care? They get their cargo on the way up, not the way down. I think it's funny that NASA lets astronauts ride on Soyuz, which relies on power at landing on dirt for them to survive, yet is being obstructionist to safety certify Dragon V2 for fully powered landings on dirt. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
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U.S. astronauts are climbing back into space capsules. Here's how they've improved over the past 50 years
JF Mezei wrote:
On 2017-09-23 13:33, Fred J. McCall wrote: down. I think it's funny that NASA lets astronauts ride on Soyuz, which relies on power at landing on dirt for them to survive, yet is being obstructionist to safety certify Dragon V2 for fully powered landings on dirt. A rare instance where I agree with you. But being devil's advocate: At the time NASA started to purchase seats on Soyuz, it had already proven itself and it ability to land. Also, they had no choice since Soyuz was also the escape pod in case of emergency. And during post Columbia stand down and after permanent shutdown of Shuttle, NASA had no choice either. True, but doesn't address the issue. Why not let SpaceX prove powered landing? Had SpaceX insited on doing land landings for dragon from the get go, NASA's reaction might have been to not bring back important cargo until after a few flights when the capsule had proven itself. Just how much cargo do you think comes back down? Most cargo vehicles are used to dispose of trash by doing uncontrolled reentries. But because the option to land on water remained available, NASA saw this as a much simpler way to get commercial cargo going, and once this happens, it is easier to just insist on it continuing. True, but what about all the flights that aren't bringing anything back? Why obstruct development? Note: for researchers, landing on land has HUGE advantages as they can get to experiments much faster. To some extent, but not all that much. Question: for a "newbie" company like Space-X, and considering the USA does not have vast areas of undevelopped land that is flat and easy to land on, how difficult is it to fairly precicely target a landing site and what are the implications if re-entry isn't perfect (as has happened on Soyuz a few times) ? If you're coming down under power (as opposed to Soyuz which comes down on parachutes and just uses power to 'soften' the landing enough to be survivable), you're not going to 'miss' by more than a handful of meters. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
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U.S. astronauts are climbing back into space capsules. Here's how they've improved over the past 50 years
In article ,
says... Anthony Frost wrote: In message Jeff Findley wrote: This has changed somewhat recently. Reportedly SpaceX is the one who shelved development of Dragon V2 vertical landing. The reasons for this aren't terribly clear, but there are hints from SpaceX that this is because they've decided to change the (Mars) landing mode of their (eventual) Mars vehicle. Also apparently NASA weren't happy about cargo flights being used for testing powered landings. Why would they care? They get their cargo on the way up, not the way down. Because Dragon is the only way that NASA can get things like EMUs back to earth for refurbishment. There have been articles on how few functioning EMUs are left. Sorry for the word-wrap on the cites: NASA is running out of space suits and it?s years away from having new ones ready https://www.theverge.com/2017/4/27/1...ut-space-suit- development-deep-space NASA Won't Have New Spacesuits For Years - Despite $200 Million Investment https://www.forbes.com/sites/bridain.../nasa-running- out-of-spacesuits/ I think it's funny that NASA lets astronauts ride on Soyuz, which relies on power at landing on dirt for them to survive, yet is being obstructionist to safety certify Dragon V2 for fully powered landings on dirt. That's the rumor. Another rumor says Dragon V2 propulsive landings are being dropped because SpaceX is going to be changing its landing mode for Mars missions. I'm not sure how much stock I put in that, but we'll just have to wait and see. SpaceX isn't afraid to change directions when something isn't working out or when another more promising approach surfaces. Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
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U.S. astronauts are climbing back into space capsules. Here's how they've improved over the past 50 years
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U.S. astronauts are climbing back into space capsules. Here's how they've improved over the past 50 years
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U.S. astronauts are climbing back into space capsules. Here's how they've improved over the past 50 years
In article om,
says... On 2017-09-24 08:43, Jeff Findley wrote: itself during descent, even when the Super Dracos aren't firing. This is quite similar to Falcon 9 first stage landings where the Merlin engines only fire briefly for boost back, reentry, and landing. And how many stage 1s were lost before SpaceX got it right? The aerodynamics of Dragon are easier and well known at this point. Dragon V2 isn't much different aerodynamically from the current cargo Dragon. For the initial test flights for Dragon, NASA should have let SpaceX try landings on land. SpaceX could have debugged it and gotten something trustworthy by the time they switched to "production" flights. Propulsive landings nixed from SpaceX?s Dragon spaceship July 19, 2017 Stephen Clark https://spaceflightnow.com/2017/07/1...gs-nixed-from- spacexs-dragon-spaceship/ From above article: "The reason we decided not to pursue (powered landings) heavily is it would have taken a tremendous amount of effort to qualify that for safety, particularly for crew transport," Musk said. "And then there was a time when I thought that the Dragon approach to landing on Mars, where you've got a base heat shield and side-mounted thrusters, would be the right way to land on Mars, but now I'm pretty confident that is not the right way, and that there's a far better approach." So, since it's not as important to Mars as SpaceX once thought it was, it's just not worth the effort to qualify it for manned landings. This was a management/engineering trade-off and appears to be SpaceX's call, not NASA's. In terms of landing accuracy, can landing from a full orbit altitude be as accurate as landing after a 3 minute flight where speed during re-entry is much lower so minute deviations in angles etc have far lesser impact? Yes. Dragon flies a lifting reentry and therefore has some cross-range capability. This was also true of both Gemini and Apollo (and Russian Soyuz and Chinese Shenzhou). I know that guidance can bring a ship over the "X". But running out of fuel before you land doesn't let guidance do much, and unless you do like Batman and land on a mattress factory, the landing will be rather harsh if you run out of fuel. After the deorbit burn, the fuel remaining in the reaction control system is only used to maintain the proper attitude. The "lift" of the craft is provided by aerodynamics and an offset center of gravity. There would be little worry about "running out of fuel". And if that were the case (e.g. a launch abort), then the plan was for Dragon V2 to land using parachutes, not propulsion. Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
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U.S. astronauts are climbing back into space capsules. Here's how they've improved over the past 50 years
Jeff Findley wrote:
In article , says... Anthony Frost wrote: In message Jeff Findley wrote: This has changed somewhat recently. Reportedly SpaceX is the one who shelved development of Dragon V2 vertical landing. The reasons for this aren't terribly clear, but there are hints from SpaceX that this is because they've decided to change the (Mars) landing mode of their (eventual) Mars vehicle. Also apparently NASA weren't happy about cargo flights being used for testing powered landings. Why would they care? They get their cargo on the way up, not the way down. Because Dragon is the only way that NASA can get things like EMUs back to earth for refurbishment. There have been articles on how few functioning EMUs are left. Sorry for the word-wrap on the cites: But most flights aren't carrying those (or anything else) back down. So why is NASA apparently being obstructionist about landing the 'empties' propulsively? I think it's funny that NASA lets astronauts ride on Soyuz, which relies on power at landing on dirt for them to survive, yet is being obstructionist to safety certify Dragon V2 for fully powered landings on dirt. That's the rumor. Another rumor says Dragon V2 propulsive landings are being dropped because SpaceX is going to be changing its landing mode for Mars missions. I'm not sure how much stock I put in that, but we'll just have to wait and see. SpaceX isn't afraid to change directions when something isn't working out or when another more promising approach surfaces. Well, they could get smaller by removing the outer ring of engines. That would reduce thrust to 1/4 of the original concept, which is about four times what a Falcon Heavy delivers. But is that big enough to support a real Mars colony? -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
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