Jet-Rocket Hybrid (Not a RAPIER)

[JMBuilder]

RAPIERs are great for SSTOs, and Toroidal Aerospikes are good for compact landers for other planets. However, we could use a little something for larger landers.

My idea is basically a jet that works in atmospheres without oxygen and even outside of the atmosphere. It's a combination of jet and rocket technology, usually called an air-augmented rocket, or ramrocket. It takes in air like a jet, and the exhaust from an internal rocket nozzle compresses the air, greatly increasing atmospheric thrust and efficiency.

In-game, the ramrocket part would need an intake to work to its full potential. It would work without one, but not very efficiently at all. It would have better efficiency than the aerospike engine inside of an atmosphere, and its efficiency would gradually decrease as air pressure got thinner, eventually reaching a somewhat low minimum efficiency similar to that of the half-size rockets. It would be somewhat heavy and would take up quite a bit of space, similar to the RAPIER.

Is this a good suggestion, or just another vague thought that I had?

[Rakaydos]

It would probably be easiest to simpy make it a rocket that has better atmo ISP (say, 800, to make it comparable with the NERVA) but crapp space ISP. That way it doesnt need any special coding as far as intake air on non-oxygen worlds.

[Scoundrel]

Didn't you already make a thread on this subject? Or are there subtle nuances between your old thread and this new thread that I'm not grasping?

[JMBuilder]

It's a refined version of another post, yes.

Perhaps the ramrocket could have its own special intake?

[GreeningGalaxy]

It would probably be easiest to simpy make it a rocket that has better atmo ISP (say, 800, to make it comparable with the NERVA) but crapp space ISP. That way it doesnt need any special coding as far as intake air on non-oxygen worlds.

Eh, this would work, but not super well. The thrust and Isp of the engine will change not only with altitude but with speed, and will certainly be affected differently by different atmosphere compositions - for instance, you could run it on only liquid fuel low in Kerbin's atmosphere and use the local O2 as oxidizer, or, in some environment like Jool with lots of ambient hydrogen, run it on only liquid oxidizer. In places like Eve (maybe; Eve's atmosphere isn't reactive enough for rocket burning, is it?) or Duna, it'll need both fuel and oxidizer, using the ambient air only as a inert propellant mass.

At the very least, this sounds like a cool idea for a mod, if one doesn't already exist.

[MKI]

My only question is how does it compare to he Rapier? Or balanced against other staple SSTO setups?

what exactly do you mean by "half sized rockets"?

Are you talking about the LV-t45 size parts?

If your saying its atmosphere mode is rocket just slightly better than the Areospike AND its low end ISP once in space is comparable to say hat of an LV-T45 than this thing is OP in Kerbins atmosphere, let alone the fact it could work elsewhere such as Duna.

[JMBuilder]

The smallest rockets have relatively low efficiency.