To bad the story about out-gassing on the Dragon hadn't been known a couple of days earlier. Would like to have seen the response to questions on this from NASA and SpaceX at the CRS-16 press conference.
Quote from: Brovane on 12/05/2018 02:23 pmTo bad the story about out-gassing on the Dragon hadn't been known a couple of days earlier. Would like to have seen the response to questions on this from NASA and SpaceX at the CRS-16 press conference. It's been known for a while, there are probably previous posts somewhere on the site.
After the eleventh Dragon arrived, one contamination-monitoring package’s frequency steadily shifted, according to a presentation posted on September 1 to NASA’s Technical Reports Server, a database of documents created or funded by the agency.
ncb, you are assuming a 1.81 mT payload vs. Lou is using a 6mT payload. Which one is it?
I think the final 6 in that equation should be a 1.81 (perhaps confused the theoretical c3 of 85 payload with Europa Clipper's nominal mass), payload shouldn't lose mass while second stage is burning. That gives a loss of ~ 878 m/s for a net gain of ~ 1165 m/s
But I think Jupiter direct is more like a C3 of 80, not 85 (at least if you optimize launch timing for lower C3). Which according to the LSP performance query, Falcon Heavy can do 2195 kg to. That should mean about 3,340 kg with a Star 48 BV stage as that is about where stack delta v without the kick stage and 2195 kg of payload matches with it.
Quote from: gongora on 12/05/2018 02:38 pmQuote from: Brovane on 12/05/2018 02:23 pmTo bad the story about out-gassing on the Dragon hadn't been known a couple of days earlier. Would like to have seen the response to questions on this from NASA and SpaceX at the CRS-16 press conference. It's been known for a while, there are probably previous posts somewhere on the site.This is in the article:QuoteAfter the eleventh Dragon arrived, one contamination-monitoring package’s frequency steadily shifted, according to a presentation posted on September 1 to NASA’s Technical Reports Server, a database of documents created or funded by the agency.The article has a link to this presentation from September.https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10748/1074805/Analysis-of-observed-contamination-through-SAGE-IIIs-first-year-on/10.1117/12.2321982.short?SSO=1
SpaceX, meanwhile, is looking at its ingredients. “SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,” says the company, adding that NASA pre-approved all the materials used in the first Dragon design.
Also noted in the article:Quote from: Sarah ScolesSpaceX, meanwhile, is looking at its ingredients. “SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,” says the company, adding that NASA pre-approved all the materials used in the first Dragon design.
Quote from: woods170 on 12/06/2018 09:37 amAlso noted in the article:Quote from: Sarah ScolesSpaceX, meanwhile, is looking at its ingredients. “SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,” says the company, adding that NASA pre-approved all the materials used in the first Dragon design.Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.
Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.
Quote from: niwax on 12/06/2018 10:09 amNot only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.. Outgassing waste deposition of tens of times the allowable limits for the world-class scientific instruments the Station is supposed and mandated to host is no small issue, IMO.The numbers of how many FOIA requests were denied by NASA and the immediate conclusions the author draws from it aren't negligible either.
Quote from: niwax on 12/06/2018 10:09 amQuote from: woods170 on 12/06/2018 09:37 amAlso noted in the article:Quote from: Sarah ScolesSpaceX, meanwhile, is looking at its ingredients. “SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,” says the company, adding that NASA pre-approved all the materials used in the first Dragon design.Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.The conspiratorial vibe that "We asked questions and NASA pulled the report!!!!" was also not a welcome facet of the article.
Quote from: eeergo on 12/06/2018 10:53 pmQuote from: niwax on 12/06/2018 10:09 amNot only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.. Outgassing waste deposition of tens of times the allowable limits for the world-class scientific instruments the Station is supposed and mandated to host is no small issue, IMO.The numbers of how many FOIA requests were denied by NASA and the immediate conclusions the author draws from it aren't negligible either.Anybody with knowledge on the subject can tell you that placing world-class scientific instruments on a station, that is regularly being visited by manned and un-manned vehicles, is not the optimal thing to do. NASA found this out early in the shuttle program when some of the instruments flying on Spacelab missions suffered badly from outgassing effects, as well as deposits from RCS bursts.Why do you think both NASA and ESA originally proposed to have free-flyer platforms, associated with the space station?They were intented for hosting contamination-sensitive payloads and instrument.However, the free-flyer platforms fell to the budget axe. So NASA and ESA ended up putting the instruments directly on the ISS structure. That necessitated minimizing outgassing from ISS structures, as well as non-propulsive attitude control of the ISS.But make no mistake; every time the ISS is visited by a vehicle (be it Shuttle, HTV, Soyuz, Progress, Cygnus or Dragon) the station gets shrouded in a blanket of RCS by-products and outgassing products from said vehicles.Its not just Dragon polluting the ISS environment. The other craft have that effect too.
Quote from: programmerdan on 12/06/2018 01:18 pmQuote from: niwax on 12/06/2018 10:09 amQuote from: woods170 on 12/06/2018 09:37 amAlso noted in the article:Quote from: Sarah ScolesSpaceX, meanwhile, is looking at its ingredients. “SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,” says the company, adding that NASA pre-approved all the materials used in the first Dragon design.Not only that, but the whole article is odd. From the headline you'd think SpaceX was gassing crew members. This feels like someone taking some random safety study from Crew Dragon and claiming "Commercial crew is killing our astronauts!". It's a known issue that is being worked on by NASA, just like about a hundred other small things on the space station. It's not better or worse than other things that are happening and there's no reason to be suddenly very concerned.The conspiratorial vibe that "We asked questions and NASA pulled the report!!!!" was also not a welcome facet of the article.Welcome or not, it happened. It's not even on the non-public NTRS anymore.
If not, what does Dragon do wrong (from the article: paint?), what long-term effects will it have on instruments sensitive to such outgassing if allowed to go on, should the limits be relaxed for certain compounds, should ...?
Although I'm with you on the first part and it's true that Soyuz and the rest of the other vehicles create some of the contamination, Dragon is by far the one that contaminates the most with high rates right at the times when a Dragon is on station while when other vehicles go and stay there the contamination rises only a bit. However... it's true this is not a big issue and can be corrected so that Dragon stays on the same levels as the other vehicles, this is totally normal to happen in this industry, there are always unknowns even when more than 10 dragons have flown into space and back, we just have to wait and see what they do and what can be done, I'm confident they'll get it right
QuoteAlthough I'm with you on the first part and it's true that Soyuz and the rest of the other vehicles create some of the contamination, Dragon is by far the one that contaminates the most with high rates right at the times when a Dragon is on station while when other vehicles go and stay there the contamination rises only a bit. However... it's true this is not a big issue and can be corrected so that Dragon stays on the same levels as the other vehicles, this is totally normal to happen in this industry, there are always unknowns even when more than 10 dragons have flown into space and back, we just have to wait and see what they do and what can be done, I'm confident they'll get it right One question is there a difference between a New Dragon and a recently refurbished Dragon? Are the procedures to re-paint, re-PICA-X and re-SPAM not baking out the VOC's effectively or does the heat of re-entry affect the process. someone will need to pull which the offending Dragons and correlate..EDIT: https://en.wikipedia.org/wiki/SpaceX_DragonThe following are CRS missions using Re-flown DragonsCRS-11CRS-13CRS-14CRS-15CRS-16
Quote from: Wolfram66 on 12/07/2018 10:04 pmQuoteAlthough I'm with you on the first part and it's true that Soyuz and the rest of the other vehicles create some of the contamination, Dragon is by far the one that contaminates the most with high rates right at the times when a Dragon is on station while when other vehicles go and stay there the contamination rises only a bit. However... it's true this is not a big issue and can be corrected so that Dragon stays on the same levels as the other vehicles, this is totally normal to happen in this industry, there are always unknowns even when more than 10 dragons have flown into space and back, we just have to wait and see what they do and what can be done, I'm confident they'll get it right One question is there a difference between a New Dragon and a recently refurbished Dragon? Are the procedures to re-paint, re-PICA-X and re-SPAM not baking out the VOC's effectively or does the heat of re-entry affect the process. someone will need to pull which the offending Dragons and correlate..EDIT: https://en.wikipedia.org/wiki/SpaceX_DragonThe following are CRS missions using Re-flown DragonsCRS-11CRS-13CRS-14CRS-15CRS-16The original Wired article, paraphrasing the SAGE III presentation, said that CRS-11 showed 21x over the contamination limits and CRS-12 at 32x over. So, it's clearly not an issue limited to only the first flights of Dragons. I don't believe that the currently public information is sufficient to determine whether the difference in outgassing between "new" and "reflown" vehicles is statistically significant.
I remember Elon once commented that an F9 booster could more or less do SSTO just not with any payload. Using two stages made much more sense. So, my question is, what could an F9 stack with no payload do? Would lunar free return be a possibility? That could make one heck of a TPS test.