A big disadvantage for SSTO, which will never go away, is that its
off-nominal performance intrinsically sucks. It makes sense for high
traffic to a low equatorial orbit, but not higher inclinations or
altitudes.
On 2016-09-27 08:43, Henry Spencer wrote:
On Tue, 27 Sep 2016, Peter Fairbrother wrote:
I hope you haven't joined the SSTO club though :)I hate to disappoint you, but I'm a lifetime member. :-)
Oh dear -perhaps you might explain?
To cut a very long story short: (a) it would have major operational
advantages; (b) although it's not easy, it shouldn't be impossibly
hard either, despite the superstitions (the performance levels needed
for *expendable* SSTO were achieved in production hardware fifty years
ago; the only serious challenge is making it reusable); (c) the main
reason it has never been done is that nobody has ever been able to get
adequate funding to *try*.
...I think it means you'll need rocket thrust vectoring (or a
very hefty RCS) for control. I don't think that's ever been done in a
rocket aircraft before; the X-15 high-altitude flights were all
ballistic trajectories, with the noisy flamey part :-) finishing at much
lower altitude where aerodynamic controls still worked...
Didn't the X-15 have a HTP RCS? Perhaps they didn't use it for high altitude flights, though I can't think why.
The X-15 indeed had an HTP RCS, for the *ballistic* part of the
high-altitude flights. It was nowhere near beefy enough to be used
for attitude control during a main-engine burn in vacuum (something
the X-15 never did).
Spacecraft with solid-fuel kick motors often were spin-stabilized for
kick-motor burn, but the ones that weren't, typically had two sets of
RCS thrusters: little ones for normal operations, big ones for
attitude control during kick-motor burn. Something like that might be
needed for a rocketplane that's going to do major thrusting in air too
thin for aerodynamic control.
Henry
