tag:blogger.com,1999:blog-8628325.post112629893001132342..comments2024-03-15T05:59:53.929-07:00Comments on Ambivalent Engineer: Falcon 9 Upper Stage RecoveryAmbivalent Engineerhttp://www.blogger.com/profile/16491915174390340818noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-8628325.post-1126311468345832092005-09-09T17:17:00.000-07:002005-09-09T17:17:00.000-07:00Iain,There are dangers in running too much gas out...Iain,<BR/>There are dangers in running too much gas out of your nozzles for reentry cooling. Apparently, IIRC the research they did on the topic showed that it greatly decreases drag due to the shock changing (ie it simulates having a pointy instead of blunt reentry shape). While the vehicle is keeping a bit cooler at first, you end up going a lot faster in the lower atmosphere, which either defeats the purpose by causing worse heating and G-loads, or even could lead to lithobraking if you're not careful.<BR/><BR/>But a little gas is probably a good thing.<BR/>~JonJon Goffhttps://www.blogger.com/profile/10960488857253480586noreply@blogger.comtag:blogger.com,1999:blog-8628325.post-1126307693661421312005-09-09T16:14:00.000-07:002005-09-09T16:14:00.000-07:00Jon says that they're going to try a tail-first re...Jon says that they're going to try a tail-first reentry. Seems reasonable, that's the heavy end of an empty rocket stage, and the nozzles are used to very high temperature operation.<BR/><BR/>Bleeding a little gas into the back side of the shock would give them a way to get some heat out of that area. I don't think they'd need a lot of gas, maybe just run the gas generator for one of the turbopumps of one engine. This would cost fuel mass only, as everything else necessary is already there (and the fuel is snugged down against the fuel pickup because it's a tailfirst entry and we're decelerating).<BR/><BR/>The extra gas might even make the front of the shock a bit wider and help get it past the bottom edge of the rocket. I wonder if you could push the idea farther and get a gas-phase parachute effect like the thrust reversers on a modern jet.Ambivalent Engineerhttps://www.blogger.com/profile/16491915174390340818noreply@blogger.comtag:blogger.com,1999:blog-8628325.post-1126300375586535432005-09-09T14:12:00.000-07:002005-09-09T14:12:00.000-07:00Iain,I discuss a little about this in my recent Se...Iain,<BR/>I discuss a little about this in my recent Selenian Boondocks post. Basically, I heard a little bit about the approach they are currently noodling, and I think that they'll likely make some attempts at seeing if it'll work, and trying to take data to improve the concept until it is eventually ready for prime-time. While I highly doubt they'll pull it off without a hitch the first time, I give them decent odds of getting at least some data, and if the idea isn't unworkable, eventually getting it figured out.<BR/><BR/>Somewhere else, Elon mentioned that they were designing all the parts on the Falcon V first stage (and thus the Falcon IX too) for up to 100 flights, not just 3-4. Whether they can acheive this or not, and if it makes economic sense or not is anyone's guess at this point.Jon Goffhttps://www.blogger.com/profile/10960488857253480586noreply@blogger.com