Is it possible for to use hot-staging in order for an upper stage to gain extra delta-V by effectively springboarding off the lower stage?What are the limits to the extent of which this can be done? What are the considerations here?Why doesn't everybody do it?
The other benefit is that you may be able to avoid adding ullage motors for propellant settling, since the stage ignites while it is under acceleration.
Quote from: Sam Ho on 06/21/2017 11:01 pmThe other benefit is that you may be able to avoid adding ullage motors for propellant settling, since the stage ignites while it is under acceleration.Doesn't help much on stages that need 3-axis RCS/ACS already, since they double as ullage thrusters.
Quote from: envy887 on 06/22/2017 12:40 amQuote from: Sam Ho on 06/21/2017 11:01 pmThe other benefit is that you may be able to avoid adding ullage motors for propellant settling, since the stage ignites while it is under acceleration.Doesn't help much on stages that need 3-axis RCS/ACS already, since they double as ullage thrusters.But it does eliminate the chicken-egg problem of ensuring that RCS/ullage thruster propellants are also settled.
But it does eliminate the chicken-egg problem of ensuring that RCS/ullage thruster propellants are also settled.
Let's not forget the ultimate Fire in the Hole staring, the N-1. Dan shame we never got to see if it would have worked.
Quote from: JAFO on 06/23/2017 07:45 pmLet's not forget the ultimate Fire in the Hole staring, the N-1. Dan shame we never got to see if it would have worked.Wrong - we did see that it (N1) didn't work. (Not for such staging.)Could it have been made to work? Eventually.
The main problem is exhaust impingement. To get any "springboard" effect, the exhaust from the upper stage has to impinge twice: first on the booster, then again on the upper stage.
The first design to use this technique was Titan I