#11
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Commercial Crew
JF Mezei wrote on Tue, 25 Jun 2019
22:57:25 -0400: When was the last time Boeing had a new manned vehicle with ejection capability? Never. And they still won't, since Starliner doesn't have "ejection capability", either. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#12
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Commercial Crew
"Fred J. McCall" wrote in message
... "Greg \(Strider\) Moore" wrote on Tue, 25 Jun 2019 15:51:12 -0400: "JF Mezei" wrote in message ... Dragon had a failure in a critical system which prevents the test of this critical system (abort in flight). Starliner hasn't had any failures because it is behind and hasn't even had unmanned test. Assuming SpaceX has found the cause and knows how to fix it, Dragon could be back in business and still be quite ahead. SpaceX appears have a new policy of not letting Musk say much, so I don't know that one can derive a conclusion from lack of news. When Boeing starts its tests, it could work flawlessly or not. We have to wait. Will they also have a max-Q abort test? That would seem to require at least 2 test flights right? I have not seen a max-Q abort test for Starliner planned. I may have missed it, but I don't think so. I think NASA is still treating Boeing as "they've done this before, we can trust them a bit more." And perhaps after the recent SpaceX explosion, they might be right. I tend to put it more down to relative cost of the two boosters. I suspect it was SpaceX's choice to do a 'live test' for a Max-Q abort. Yeah, I guess I didn't add the comment I thought I had, but I suspect SpaceX feels it's cheaper to do a live test because for them it's a fairly small incremental cost (fuel and if there's overtime added to the workflow). For Boeing, it's a much steeper cost and they probably are comfortable enough saying it's cheaper to do ground testing than "waste" a booster. Wikipedia shows that test as scheduled for late July using a previously flown booster, but I wonder if the abort test will destroy the booster. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net IT Disaster Response - https://www.amazon.com/Disaster-Resp...dp/1484221834/ |
#13
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#14
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#15
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"Jeff Findley" wrote in message
... In article , says... Yeah, I guess I didn't add the comment I thought I had, but I suspect SpaceX feels it's cheaper to do a live test because for them it's a fairly small incremental cost (fuel and if there's overtime added to the workflow). For Boeing, it's a much steeper cost and they probably are comfortable enough saying it's cheaper to do ground testing than "waste" a booster. Wikipedia shows that test as scheduled for late July using a previously flown booster, but I wonder if the abort test will destroy the booster. The abort test will reportedly use an actual fueled upper stage but no flight worthy Merlin vacuum engine. And from what I've read, SpaceX does not believe that the booster will survive the test. Some reports have said they don't even plan on trying to recover the booster. So they're planning on expending an entire Falcon 9, minus one Merlin vacuum engine, for this test. That's got to be hardware worth tens of millions of dollars. True, I had overlooked the cost of the upper stage! That is not a small chunk of change, though without the engine, they're definitely saving some money there. As for the booster, yeah, assuming they can't recover it, it's a loss, but still cheaper than ULA because they're both cheaper to start with and they can afford to lose a re-used stage since in a sense it's already been paid for. Jeff -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net IT Disaster Response - https://www.amazon.com/Disaster-Resp...dp/1484221834/ |
#16
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Commercial Crew
On 19-06-27 13:55 , Jeff Findley wrote:
The [SpaceX Dragon-2] abort test will reportedly use an actual fueled upper stage but no flight worthy Merlin vacuum engine. Do you have a link/reference for that? The descriptions I've found say no upper stage, and only three Merlins on the first stage. -- Niklas Holsti Tidorum Ltd niklas holsti tidorum fi . @ . |
#17
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JF Mezei wrote on Thu, 27 Jun 2019
11:47:09 -0400: On 2019-06-27 06:55, Jeff Findley wrote: flight worthy Merlin vacuum engine. And from what I've read, SpaceX does not believe that the booster will survive the test. Some reports have said they don't even plan on trying to recover the booster. Recovery would be interesting from a forensic point of view. at Max Q altitude, are videos of the craft precise enough that recovering the wreckage would not yield much info? What info do you need? Would it be correct to state that there are 2 scenarios where in-flight capsule eject would be triggered: -catastropic failure of lower stages. (eg: explosion) -failure of guidance and stack headed for downtown Manhattan and capsule gets to eject just before self destruct for stack is activated ? In the second case, is there a choreography challenge to ensure the ejected capsule doesn't end up colliding with the rocket that is still under power until detonation? No. The capsule accelerates away from the stack. That's sort of the point. So they're planning on expending an entire Falcon 9, minus one Merlin vacuum engine, for this test. That's got to be hardware worth tens of millions of dollars. SpaceX undoubtedly has a "max re-use of X times" for Falcon 9s at this point. (X may increase later on). If they have a rocket which has has its X reached, it has no commercial value left and could be used for such a test. And with such a test, help validate Faklcon9 for X+1 re-uses. They have no such rockets. Nothing is anywhere near flight limits. I suspect SpaceX chose this route because it's really the only way to actually test it. Simulations are nice and all, but the data you get from them is no better than the accuracy of the simulation. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#18
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"JF Mezei" wrote in message ...
Say the stack explodes violenty. On the pad, assuming capsule ejects at same time, one would hope that its speed would at least match that of debris flying towards it so that debris won't damage capsule. Right? That's the ideal, yes. After launch, would Max-W be the safest time from a debris point of view because this is where debris would be slowed the most? Or would the capsule eject at an equally slower speed and the risk is the same? You are launching into Max-Q, so that's an issue. But overall, the aerodynamics are tougher. At the pad level, there's no real airflow so the capsule will mostly go where the rockets direct it (as seen in SpaceX's pad abort test). But at Max-Q, I suspect if you misjudge something, the airstream risks causing a tumble or other issue. Just curious if Max-Q is the most difficult/dangerous ejection solely from the point of view of debris from explosion underneat hitting capsule? Probably not, in part you've got a lot less fuel driving the explosion. But the aerodynamics are trickier. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net IT Disaster Response - https://www.amazon.com/Disaster-Resp...dp/1484221834/ |
#19
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In article ,
lid says... On 19-06-27 13:55 , Jeff Findley wrote: The [SpaceX Dragon-2] abort test will reportedly use an actual fueled upper stage but no flight worthy Merlin vacuum engine. Do you have a link/reference for that? The descriptions I've found say no upper stage, and only three Merlins on the first stage. This isn't a very recent article, but it's based on a document submitted to the FAA for the test, so I'm betting it's as accurate as we're going to get before the actual test. How SpaceX Will Conduct an Inflight Abort Test for Crew Dragon November 28, 2018 Doug Messier http://www.parabolicarc.com/2018/11/...duct-inflight- abort-test-crew-dragon/ From above (which I believe are excerpts from the document submitted to the FAA: The booster would include nine M1D engines and be configured to perform an ascent abort shutdown. Each engine is propelled by liquid oxygen (LOX) and rocket fuel (RP-1; highly refined form of kerosene) and produces 190,000 pounds of thrust at sea level (for a total of 1.71 million pounds of thrust from all nine engines). The booster would carry the standard set of flight instrumentation. The second stage would be a standard Falcon 9 second stage, with the exception of the M1D vacuum engine. The components essential to propellant loading operations would be carried, but the thrust chamber, turbopump, thrust vector control actuators, and other components required for performing second stage burns, would be omitted, as the mission concludes part- way through the first stage ascent burn. Propellant loading would follow standard loading operations for the second stage. So, this sounds like a very high fidelity test. Very little would be different from this Falcon 9 and a Falcon 9 used to launch Dragon 2 to ISS. 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. |
#20
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