Oct 19, 2018 02:50
Take a set of linear aerospike engines, say 5-11 opposed pairs (they'll drop off in pairs as you go up)
Mount them on a large piston that can slide up into the tank, engines and all
Put a common bulkhead in the tank, also able to slide like a piston
Take a pair of plasma cutting torches and mount them to opposite sides of a ring that's slowly rotating around the central propellant manifolds, and mount another pair on another ring that counter-rotates
Finally, arrange for cables or something to tension the ends of the rocket together
The result is a rocket that drops its engines (and associated turbomachinery) as soon as their thrust is not needed, and literally cuts off and drops tankage as it goes
(specifically, the counter-rotating torches cut intersecting spirals in the tank, dropping diamond-shaped chunks at intervals)
Plasma torches can, with sufficient amperage, cut thin plating fast enough that I think this would work OK
