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Pares #8381 Érdekességek:
Eric Berger
@SciGuySpace
20h20 hours ago
Source says "full panic has ensued" as NASA realizes commercial crew may not be ready in first half of 2020; and Gerstenmeier is no longer around to help the companies along, or negotiate with Russians for more Soyuz seats. Focus on Artemis may put ISS program in real danger.
Elon Musk
@elonmusk
Replying to @SciGuySpace
For what it’s worth, the SpaceX schedule, which I’ve just reviewed in depth, shows Falcon & Dragon at the Cape & all testing done in ~10 weeks
7:36 AM - 8 Oct 2019
twitter
A Crew Dragon anomáliáról, mi okozta, és hogyan oldották meg:
Host: Now, I know, after Demo One, you know, the mission wasn't over. I know this was something that was in the news. Was the anomaly that happened, right after -- I guess, shortly after splashdown. So, what happened there?
Benji Reed: Yeah. So, what was going on there, as we talked about, is our launch escape system, our launch abort system. And what we wanted to do; is we want to go into our inflight abort test. So, just a little bit of background on that first. The inflight abort test is where we take Dragon and we put it on top of a rocket, launch the rocket. And basically, we kind of get to your worst-case conditions, what we call max q or your maximum dynamic conditions on launch. And at that point, then you initiate the launch escape system. And make sure, again, that you could get the crew away safely, in that situation. So, we were getting ready to do that. And we were going to use that same capsule that we used for Demo One, for that launch escape test. And as part of the preparations, before that test, we did some refurbishment on the Dragon. Just a little bit we needed to do to kind of get ready to fly again. And we put it on a test stand, down at the Cape. And we did an initial test of those 12 Draco engines, which went great. Everything came out nominally. And then we were going to do an initial firing of the SuperDracos, the SuperDracos. And just as we were about to initiate that, just as we were initiating that, those SuperDracos, there was an anomaly. And it resulted in explosion. And we lost the vehicle. Obviously, that was kind of a big shock for all of us. Very, very unexpected. But also, kind of really the reason of why we test, right? And I talked earlier a little bit about all the kinds of testing that you do. And all the kinds of analyses that you do, to make sure that you're going to do things right. But at the end of the day, a full system level test, is just really hard to beat that. And that's what that was. It was a full system level test. And so, we learned a lot. We learned a ton from it. And kind of the bottom line of what happened there, is that what we discovered was -- so, let me actually back up and give a little bit of a background. So, there's kind of multiple systems, right, as part of our propulsion system. As part of our -- the Draco, and SuperDraco engines. There's the liquid system, the fluid system, right? With your fuels in there. And there's also the gas system. So, the helium, the high-pressure helium system. And you use that high-pressure helium system to keep pressures up as you need to, as you're actually operating those engines. So, for example, when you're going to operate the SuperDraco engines, you actually need to feed the fuel through those engines at a high rate and a very high pressure. So, you use this high-pressure helium system to push that fuel through, at the rate that you need. And so, what we discovered, was that there was a valve that -- between those two systems. That was allowing a little bit of the fluid to leak back into the gas system. And that fluid, just the right amount of fluid, had leaked in. And kind of had made a little slug, if you will, of liquid. Just a little bead of the liquid in the tubing in the piping of that -- of the gas system. And so, then -- and that had been -- that had happened at some point previous to when we were going to do the testing. And then when we initiated that test, basically, went to open up and pressurize that helium system. It accelerated that slug of fluid a lot. And that slug of fluid impacted one of the valves at high speed. And basically, had enough energy to initiate an explosion. And that was -- that was eye opening. And the reason particularly, was because over all the years and all the spacecraft that use the same fluids, these same fuels. And use the same kinds of materials. In this case, titanium, for the lines. Nobody had ever predicted that you could be able to get that kind of reaction. At least it was not commonly thought that that was possible. And so, it was actually kind of industry leading knowledge that we all gained from this. And have been sharing with NASA and with others. Because it's really important that we understand the behavior of this. Now, the key here is that it was accelerated at a really high rate. And so, that's part of what we needed to figure out, was how do we prevent that from happening again? And we've already been doing a lot of design -- redesign work. And implementation of those mitigations of those fixes. And the simplest thing that we've done, and it's always often the best thing -- the best solution is the simplest solution. And in this case, it turns out to be what we call a burst disk. So, instead of having a valve in place of trying to hold back or kind of separate the two systems. We now added a burst disk that will prevent -- kind of hermetically seals the two systems from each other. So, that there's no way that liquid can kind of slowly leak in and create that little slug of propellant. And then when you're ready to actually use the system, when you get up to the right pressure, that burst disk does what it sounds like it does, it just bursts. And let's the gas through, so that you can pressurize the rest of the system appropriately. And we've been doing a significant amount of testing on that, on the ground, as well. And then we look forward to doing another test of the SuperDracos on the ground again, before we do our inflight abort test.
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