Re:SpaceX Launches Super-Heavy Communications Satellite
by neolefty on Monday May 15, 2017 @11:59PM
(#14347281)
They've made some amazing progress! However, a landable booster can't put itself into orbit -- its engine cutoff is always well under 3000 m/s (today's was about 9800 kph according to the YouTube broadcast, or about 2700 m/s, and that was with no fuel margin left for landing), but about 7800 m/s is required for orbit.
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Re:SpaceX Launches Super-Heavy Communications Satellite
by ChuckMcM on Tuesday May 16, 2017 @12:15AM
(#14347316)
Elon's tweet today (https://twitter.com/elonmusk/status/669132749500887040) was that a booster with no payload could put itself into orbit. And that certainly supports your statement. It clearly would not be possible to launch a second stage and have the booster stage make it all the way into orbit. But it isn't as far out of whack as it might be.
Re:SpaceX Launches Super-Heavy Communications Satellite
by wolf550e on Tuesday May 16, 2017 @01:44AM
(#14347623)
Tsiolkovsky is very clear about the propellant mass fraction needed for single stage to orbit, and it is unachievable with current materials, i.e. you can't build a useful SSTO using Al-Li tanks.
https://en.wikipedia.org/wiki/Single-stage-to-orbit#Design_c...
Re:SpaceX Launches Super-Heavy Communications Satellite
by Symmetry on Tuesday May 16, 2017 @08:49AM
(#14349115)
The first stage has a fuel mass fraction of 95.5%. Propellant densification and high thrust to weight ratio engines buy you lot. That should be enough to make orbit.