Or an aft mounted toroidal inflatable skirt using similar technology to HIAD, and a forward mounted Pica-X heatshield.
Entering nose first, shuttlecock style?
. Hope someone answers the ion thruster/photovoltaic panel deorbit idea that someone upthread suggested.
Isn't that what they showed in their 2011 reusability video? TPS covering the top of the stage and partially down one of the sides...
That video also showed an extending/retracting engine bell to create clearance for the legs, IIRC.
Quote from: Kaputnik on 04/01/2017 02:23 pmOr an aft mounted toroidal inflatable skirt using similar technology to HIAD, and a forward mounted Pica-X heatshield.Quote from: nacnud on 04/01/2017 02:27 pmEntering nose first, shuttlecock style?Isn't that what they showed in their 2011 reusability video? TPS covering the top of the stage and partially down one of the sides.That video also showed an extending/retracting engine bell to create clearance for the legs, IIRC.
They couod just keep a heap of residual propellant in the stage and enter nose first- this would significantly affect the CG and increase stability.Or, thinking this through, add ballast (shudder) to the top of the stage...
Quote from: Clueless Idiot on 04/01/2017 05:55 amHi 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.maybe instead of grid they could do simple flat fins like blue origin
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.
Quote from: dorkmo on 04/01/2017 06:07 amQuote from: Clueless Idiot on 04/01/2017 05:55 amHi 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.maybe instead of grid they could do simple flat fins like blue originI think that's a bad idea. Grid fins are far more efficient in terms of control authority/lift per unit mass. That's why people use them. Blue may reconsider their thinking on flat fins, we'll see.. Flat fins may heat less though... except at the leading edge. Grid fins are ALL leading edge :)
You can waste performance on the Falcon Heavy demo mission.
Quote from: Robotbeat on 04/01/2017 05:45 amYou can waste performance on the Falcon Heavy demo mission.True. And he's hinted at something ... surprising. Here's how you might use that (but for a lot of reasons its unlikely).You could either loft an entire, fueled stage in the fairing ... or tanks to refill the second stage, including excess for boil-off.In effect you'd want to end up on orbit with a fully loaded US that has a Dragon heat shield on top.The autonomous program would check out the refuel, and orient/phase the stage for a grazing entry precisely.The US RCS would control buffeting as EI occured, getting the stage as low as possible given CG, with perhaps a cooled/vented heat shield. Then, before aerodynamic pressure built up too high, the stage would flip and RCS would maintain orientation. You'd go as low as you could heating the engine bell, then ignite and burn for an extended entry burn, likely wiggling the gimbal to increase drag, and likely burning to exhaustion. Hopefully making it to transonic.Passive CG would keep you from tumbling. Assuming you survive to free fall velocities, you pop the chutes around 5K feet, and perhaps there's something floating on the surface for a little while to be admired.You
Is SpaceX conducting super secret testing such as a black ops program for future designs away from the public eye.
Clearly SpaceX already has a second stage prototype ready to go. You just don't slap things on to an existing stage. This brings up an important point. Is SpaceX conducting super secret testing such as a black ops program for future designs away from the public eye.
New designs take years to develop.
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?[1] https://en.wikipedia.org/wiki/Merlin_(rocket_engine_family)#Merlin_1D_Vacuum[2] http://www.spacelaunchreport.com/falcon9ft.html[3] https://en.wikipedia.org/wiki/Newton_(unit)#Definition
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.