Quote from: Ike17055 on 07/11/2018 03:43 pmnobody knows where these contractors stand in regard to completion.We do now.
nobody knows where these contractors stand in regard to completion.
To better understand the propellant loading procedures, the program and SpaceX agreed todemonstrate the loading process five times from the launch site in thefinal crew configuration prior to the crewed flight test. The five eventsinclude the uncrewed flight test and the in-flight abort test. Therefore,delays to those events would lead to delays to the agreed upondemonstrations, which could in turn delay the crewed flight test andcertification milestone.
nobody knows where these contractors stand in regard to completion. SpaceX has encountered plenty of delays so the previous post is incorrect. the ideas regarding vertical integration being naturally fsater is a theory that may or may not be true. The idea that using proven components should be a faster development approach is likewise a theory that may or may not be true. both hypotheses are going to be put to the test, so we will know which hypothesis is more valid - in this case - within a few months, most likely.
It's not clear whether Boeing or SpaceX is more prepared for commercial crew certification than the other. But what seems increasingly clear to me is that NASA is less prepared than either of the providers.
Quote from: butters on 07/11/2018 04:28 pmIt's not clear whether Boeing or SpaceX is more prepared for commercial crew certification than the other. But what seems increasingly clear to me is that NASA is less prepared than either of the providers.So this would mean that if (big if) the providers could pull off crewed missions in the first half next year, they would have to wait a year to fly again on a certified mission?
Quote from: envy887 on 07/11/2018 04:04 pmQuote from: Ike17055 on 07/11/2018 03:43 pmnobody knows where these contractors stand in regard to completion.We do now.No we don't. The information in that table has been outdated for months.It provides a snapshot of the status as it was at the start of the second quarter of calendar year 2018.We now are in the third quarter of calendar year 2018.The CCP contractors are closer to completion than this table suggests.
I'm not too familiar with risk analysis, so correct me if I'm wrong. Won't flying the uncrewed demonstration missions successfully retire a significant amount of schedule risk? In other words, the range of expected certification dates should shrink. As an example the current average dates from the risk assessment are end of year 2019/early 2020. If the uncrewed demonstrations come off successfully at the end of the year(ish), might we not expect the risk assessment average to move up into the middle of the second half of 2019?
Quote from: rockets4life97 on 07/12/2018 01:32 pmI'm not too familiar with risk analysis, so correct me if I'm wrong. Won't flying the uncrewed demonstration missions successfully retire a significant amount of schedule risk? In other words, the range of expected certification dates should shrink. As an example the current average dates from the risk assessment are end of year 2019/early 2020. If the uncrewed demonstrations come off successfully at the end of the year(ish), might we not expect the risk assessment average to move up into the middle of the second half of 2019?I might be behind the times but I believe at this point the sticking point on the risk analysis has to do with the time in orbit more then the launch. Objects in LEO get hit by micrometeorites which can cause damage that turns fatal upon reentry.
I have not been following closely the development of crew capsules, but the possible delay of another year or two does not make any sense to me. These capsules are not that complicated, and the current Dragon has been flying for years without, I think, major problems that would have threatened the survival of a live passenger (animal, or human). Capsules from Mercury and Apollo to the current Dragon have accumulated an impressive number of successful flights, and I think much is known of the unbreakable Soyuz capsules, so the requirements should be well documented. Are the developers facing continuing changes of specs from NASA in search of ever increasing reliability, after the Shuttlle fiasco ( much more dangerous than thought at the time?). In my career I faced several times the problem of project managers less competent than developers that simply did not have the knowledge and the brains for judging solutions and to develop clear and final specs, the balls for pulling the trigger, or the honesty to admit that the technical issues were over their heads and hence constantly chasing windmills...
Dragon 1 has accumulated lots of time in the exact same orbital environment in which Dragon 2 will operate. My understanding is that NASA has decided not to include empirical data on MMOD from CRS missions into its theoretical risk analyses for CCP. My assumption is that they're justifying this on the grounds that Dragon 2 is not identical to Dragon 1 and therefore nothing about the observed reliability of Dragon 1 can be used to inform the risk assessment for Dragon 2.
Quote from: butters on 07/12/2018 04:55 pmDragon 1 has accumulated lots of time in the exact same orbital environment in which Dragon 2 will operate. My understanding is that NASA has decided not to include empirical data on MMOD from CRS missions into its theoretical risk analyses for CCP. My assumption is that they're justifying this on the grounds that Dragon 2 is not identical to Dragon 1 and therefore nothing about the observed reliability of Dragon 1 can be used to inform the risk assessment for Dragon 2.Which is odd, since they should be able to use actual MMOD data from all the flights to date to help validate their models for predicted strikes, since Dragon 1 is very close in size to Dragon 2.
Quote from: johnfwhitesell on 07/12/2018 01:40 pmQuote from: rockets4life97 on 07/12/2018 01:32 pmI'm not too familiar with risk analysis, so correct me if I'm wrong. Won't flying the uncrewed demonstration missions successfully retire a significant amount of schedule risk? In other words, the range of expected certification dates should shrink. As an example the current average dates from the risk assessment are end of year 2019/early 2020. If the uncrewed demonstrations come off successfully at the end of the year(ish), might we not expect the risk assessment average to move up into the middle of the second half of 2019?I might be behind the times but I believe at this point the sticking point on the risk analysis has to do with the time in orbit more then the launch. Objects in LEO get hit by micrometeorites which can cause damage that turns fatal upon reentry.Dragon 1 has accumulated lots of time in the exact same orbital environment in which Dragon 2 will operate. My understanding is that NASA has decided not to include empirical data on MMOD from CRS missions into its theoretical risk analyses for CCP. My assumption is that they're justifying this on the grounds that Dragon 2 is not identical to Dragon 1 and therefore nothing about the observed reliability of Dragon 1 can be used to inform the risk assessment for Dragon 2.
(snip)Hell, the area-time product of ISS as a whole only barely approaches a statistically significant sample for a lot of the relevant particles.