@elonmuskConsidering trying to bring upper stage back on Falcon Heavy demo flight for full reusability. Odds of success low, but maybe worth a shot.https://twitter.com/elonmusk/status/847882289581359104
Hi all,Now I just cant imagine a tube flying aerodynamically through the atmosphere without grid fins, theres no way S2 wont have grid fins will it? Can grid fins survive reentry without burning up, imagine grid fins covered in pica-x.
Why does it need to quickly de-orbit and land. That requires lots of fuel mass.What about doing something the new sats are doing?Like putting on some small lightweight ion engines and a ring of solar cells somewhere on the stage?Would there be a problem taking months to get into a de-orbit situation?
My maths and physics is very rusty but...According to Wikipedia[1], the Merlin 1D can throttle to 360 kN (81,000 lbf).According to Space Launch Report[2], the F9 second stage dry mass is ~4.5t We know F=m.a[3] where F=force in N, m=mass in Kg and a=acceleration in m/s/sWe also know g=acceleration-due-to-gravity=9.8m/s/s so at 1g F=4500.9.8/1000=44kNand 360/44=8.16so it seems that a Merlin 1Dvac could land a second stage with an ~8g hoover slam.Two question for the experts on NSF: 1) Is this calculation correct?2) Could the stage survive 8g?
Quote from: NX-0 on 03/31/2017 07:03 pm@elonmuskConsidering trying to bring upper stage back on Falcon Heavy demo flight for full reusability. Odds of success low, but maybe worth a shot.Any ideas how they might go about achieving this? Parachute landing, or propulsive landing? Deployable heat shield, or ablative-covered tanks? Probably going to need some serious heat protection as Stage 2 will need to re-enter at much faster than LEO speeds if it's sent a sat to GTO. Will need bigger batteries and maybe other consumables, too, to be able to still have power 4.5 hours or so after launch when it will be re-entering from a GTO mission...
@elonmuskConsidering trying to bring upper stage back on Falcon Heavy demo flight for full reusability. Odds of success low, but maybe worth a shot.
Elon MuskCompte certifié @elonmusk 13 hil y a 13 heuresEn réponse à @BadAstronomerWe can def bring it back like Dragon. Just a question of how much weight we need to add.
Because of the time constraints, I proposed that they could try a system on the Falcon Heavy Demo mission with 4 legs in the payload fairing. Splay them out and perform re-entry from LEO. Spreading the heat over the larger area would be interesting and might inform the development of a fairing/heat-shield combo to protect the second stage. It might be something like a 3 part fairing with two parts recoverable and the 3rd part sliding into position downward to protect the stage. How it would land? Deployable paraglider 'chute like the fairing onto a "bouncy castle" (air-bag like) barge.
If i'm visualising this correctly, it puts too much surface area ahead of the centre of gravity, and the stage would be extemely unstable and want to fly backwards.