> So it doesn't matter if it makes up 10% of the mass consumed - what matters is how much impulse it provides.
Minimizing the final dry mass at the end of the burn is also very important to maximize delta-v, according to the Tsiolkovsky rocket equation. So it's not just about the impulse provided by the fuel.
Yes, the cool thing about this approach is that you can reach extreme vehicle mass ratios without staging. So for example, it could make a single stage to orbit vehicle feasible, on re-entry you replace the cheap consumable "body" and you are ready for another launch.
But it's only an improvement if the fuselage is actually effective in containing the propellant, or is the propellant (imagine a long stick of rocket candy burning at the end, mechanically drawn by a closed nozzle). Otherwise, what you gain in mass ratio you use lose in useful impulse because you need to lift this large mass of mostly inert plastic at launch.
It’s been said that there’s no new ideas in rocketry. Even the most cutting edge stuff was theorized and probably even tested in some rudimentary way by some crazy aerospace engineers in the 50s. They just watched it explode and gave up because rocketry was as much art as science back then - literally throwing stuff against the wall and seeing what explodes (and what explodes a little longer and more usefully).
You also need something that can transfer the thrust to the payload. If you’re burning this thing as an SSTO, it needs to survive being shoved forward at rather more than 1g with payload attached, presumably at the end opposite the nozzle.
I suppose one could attempt a truly exotic design in which the fuel tank gets gasified, piped past the payload, and then burned, thus allowing the tank to be on top, but these seems unlikely to work very well.
>I suppose one could attempt a truly exotic design in which the fuel tank gets gasified, piped past the payload, and then burned, thus allowing the tank to be on top, but these seems unlikely to work very well.
I've been thinking of this design for a long time, but so far it sounds a bit preposterous even for a sci-fi enthusiast with no rocketry knowledge :)
Minimizing the final dry mass at the end of the burn is also very important to maximize delta-v, according to the Tsiolkovsky rocket equation. So it's not just about the impulse provided by the fuel.