Quote from: abaddon on 02/27/2019 06:31 pmMax drag is the most difficult in-flight regime in which to abort, your opinion not withstanding.Okay, but why exactly? MaxQ is max drag. After separation the streamlined Dragon will have less aero drag than the uncapped F9. Wouldn't that increase the acceleration difference between the two? And if any debris was thrown out by F9 disintegrating, that debris will also have max drag and be much less likely to catch up to Dragon.I just want to understand better exactly why MaxQ is worst case when the forces seem to be working against it.
Max drag is the most difficult in-flight regime in which to abort, your opinion not withstanding.
If the S1 engines are shut down prior to abort, relative acceleration isn't minimum. At MaxQ, S1 thrusting acceleration is not yet maximum. And with MaxQ having maximum drag, the F9 will have maximum deceleration following separation.
Quote from: whitelancer64 on 02/27/2019 05:08 pmIf the Falcon 9 booster breaks up in flight, then it won't meet all of the desired test criteria (i.e. the capsule won't experience the dynamic pressure it was supposed to). It would mean, most likely, another in-flight abort test, at great cost and a big schedule delay for SpaceX.Disagree. It would mean, more likely, that SpaceX would apply the findings to their simulation and just simulate the max-q abort, as Boeing is doing (without any flight data of the stack with the capsule at all). Depending on how close it got to max-q, if it blows up early in the flight it would generate little valuable data in that regard.Of course, it would also mean that SpaceX experienced an unexpected Falcon 9 failure that would need to be root-cause analyzed and set the progress of the program way back, frankly more than conducting another in-flight abort would likely result in on its own. Little Joe failing on its own had no implication on the Apollo stack.
If the Falcon 9 booster breaks up in flight, then it won't meet all of the desired test criteria (i.e. the capsule won't experience the dynamic pressure it was supposed to). It would mean, most likely, another in-flight abort test, at great cost and a big schedule delay for SpaceX.
Quote from: abaddon on 02/27/2019 05:16 pmQuote from: whitelancer64 on 02/27/2019 05:08 pmIf the Falcon 9 booster breaks up in flight, then it won't meet all of the desired test criteria (i.e. the capsule won't experience the dynamic pressure it was supposed to). It would mean, most likely, another in-flight abort test, at great cost and a big schedule delay for SpaceX.Disagree. It would mean, more likely, that SpaceX would apply the findings to their simulation and just simulate the max-q abort, as Boeing is doing (without any flight data of the stack with the capsule at all). Depending on how close it got to max-q, if it blows up early in the flight it would generate little valuable data in that regard.Of course, it would also mean that SpaceX experienced an unexpected Falcon 9 failure that would need to be root-cause analyzed and set the progress of the program way back, frankly more than conducting another in-flight abort would likely result in on its own. Little Joe failing on its own had no implication on the Apollo stack.Emphasis mine.Yes, this.People here have to remember that none of the abort flight-tests were required by NASA. Under the CCiCAP and CCtCAP contracts NASA only required the CCP contractors to model the abort regime, along with extensive ground-testing of the abort motors.Boeing added a pad-abort flight test as a voluntary milestone to its CCtCAP contract.SpaceX added both a pad-abort flight test and a Max-Q ascent abort test as voluntary milestones to its CCiCAP contract.If any of those tests fail the CCP contractor in question will revert back to the default NASA requirment: modeling only of the abort regimes. No repeat or reflights of failed abort test flights.
But both get payed for the voluntary milestones, right? So if the test fails, no milestone money. I guess doing the abort tests was a financial decision for both companies, not the need for information necessarily. Its good to have the real world data, but if simulations are fine for NASA, its hard to believe that SpaceX or ULA wouldnt be fine with that as well. So I guess SpaceX just thinks they can make a profit from the inflight abort test and that is the primary motivation for doing it.
Quote from: Semmel on 02/28/2019 11:18 amBut both get payed for the voluntary milestones, right? So if the test fails, no milestone money. I guess doing the abort tests was a financial decision for both companies, not the need for information necessarily. Its good to have the real world data, but if simulations are fine for NASA, its hard to believe that SpaceX or ULA wouldnt be fine with that as well. So I guess SpaceX just thinks they can make a profit from the inflight abort test and that is the primary motivation for doing it.Unless the payment has increased a lot from the last time we saw those contract numbers, it's not likely SpaceX could make money on the abort test even with a reused booster. It's also not likely that much (maybe not any) of the payment would be tied to the complete success of the test.
Is it time to split this thread into updates vs discussion?
The update clock starts the moment DM-1 splashes down and is sent back to Hawthorne for refurb. That's the pacing item. More so than the F9 that they already sent back to the barn.
Quote from: rcoppola on 02/28/2019 02:03 pmThe update clock starts the moment DM-1 splashes down and is sent back to Hawthorne for refurb. That's the pacing item. More so than the F9 that they already sent back to the barn.Are you sure it's being sent back to Hawthorne for the refurb? I thought I saw something that indicated for the Iin-Flight Abort test, that the Crew Dragon would stay at the Cape for all In-Flight Abort test preparations.
At the NASA social briefing just now for DM-1, Benji Reed from SpaceX (Director of Crew Management) was asked about the in-flight abort test. He said that SpaceX would ideally like to bring the booster home. So maybe they'll equip it for a return (although as Elon recent said it may well not survive).
Quote from: FutureSpaceTourist on 02/28/2019 03:35 pmAt the NASA social briefing just now for DM-1, Benji Reed from SpaceX (Director of Crew Management) was asked about the in-flight abort test. He said that SpaceX would ideally like to bring the booster home. So maybe they'll equip it for a return (although as Elon recent said it may well not survive).If they hope to recover it, it’s not a MAYBE that they will include recovery hardware. It is a CERTAINTY. (Assuming that intention does not change)
