self- consuming rocket

[wildspace]

there are two main ways to increase the veocity of a rocket
one increase the Isp of propellants.
two or increase the effective mass ratio . traditionally this is done by staging in sequence or in side by side. But I have been kicking around another form of staging. where the tankage of the rocket is also the fuel, in a hybrid motor system. picture a long plexiglass thin walled tube ( banded with narrow carbon fiber reenforcments. The tube contains a solid plug-spike motor pulled forward by a steel-kevlar cable attached to pressure driven wench anhored to the nose. When in operation the Tube is pressurizes with liquid n2o. the oxidizer sprays against the plexglass in the combustion region of the spike and is ingnited as the fuel walls are burned the motor is pulled forward in the end all that remains is the motor and the nose of the rocket. this is a oversimplifation but it seem one could have mass ratio of 20 to 1 or better, any thoughts .

[SANEAlex]

It sounds like an interesting idea but as i see it the motor that you would be pulling would have to be slightly wider than your fuel source (the plexiglass) which would cause turbulence and if it burnt/melted unevenly you would get burn thru above the engine causing more problems.

[MisterQED]

I might be misunderstanding but does the plug have the nozzle on the end?
In any case, hybrids are not end burners, they burn relatively evenly from the core out.
I don't see how the nozzle end burns away fast enough to keep the end nearest the nose from blowing out?
There was an idea similar to this on the HB:
This also reminds me of ribbon rockets:

If you replaced the plexiglass tube with plexi rod and then ran the oxidizer down the side to be injected at the end of the rod it might help.
But the seal on the rod would be a challenge.
Also the tension necessary to pull the nozzle towards the nose would be significant.
It would have to be balanced by the plexi tube or rod which would be dicey and diceyer as the rod got hot.

Interesting though,
MisterQED

[Monroe]

Hahaha a Road Flair that's what you get. What we need is a crawling nozzle that can climb the fuel tank and contain the combustion chamber.

Monroe

[wildspace]

Good input, My thought is that the nozzle being a spike could be internal to the tank and pulled forward internally. The ideal contour of this plug nozzle is a long tapering 'spike' with a long combustion chamber situated at the base because of the slow regression rate of hybrids. getting the wall material to burn at just the right rate might be impossible an external sliding sleeve(fin can?) pulled forward at the same rate as the motor might be needed to prevent premature burn though and on the other hand if the wall burned to slowly it could be made to shed off in rings if not totally burned weak points could be designed to fail between renforcement bands.
the tension required to pull against the high pressure oxidizer would be offset to a degree by the thrust since the pressure in the combusion chamber would be equal to the feed pressure.

[wildspace]

A couple of very simular ideas pat# US4723736 and US3127739

[ZiraldoAerospace]

I don't know, it sounds overly complicated to me, I would think that separate stages would be easier, and you won't be losing weight as the motor climbs. Keep the ideas coming though!