Alternative propellant.

I propose Sodium as an alternative fuel because it puts out yellow flames /s

Bad everything else though.

On a more serious note, I think I saw someone using Pentane in a design but I haven't gotten around to checking it out.

Neon is my preferred MPD propellant due to its excellent cheapness and performance. (251 km/s @ 100GW)
 
Sulfur dioxide outperforms xenon with nearly the same density and greatly reduced cost.

Both of these are on the standards thread already as MPD propellants.


All the hydrocarbons between methane and decane are usable for NTRs; they form a spectrum of increasing density and decreasing exhaust velocity.
They form a similar spectrum of increasing utility in resistojets.


Theoretically, diborane should be similar to methane in all respects. But we don't have it in-game (yet?).

I think butane and pentane can be alternative fuel for having balanced attribute in between exhaust speed of methane and density of decane.

They are after all, hydrocarbons except with longer and shorter chain.

Also, if you are using neon as MPD fuel, use resistojet instead of NTR for higher thrust burn because resistojet give a slightly higher exhaust speed (2.83 kmps)

Same but you can't get it hot enough to get into blue, everything melts.

I tried replacing my F+CH₄ rockets with F+NH₃ and kept them roughly the same size.

I converted a 27.4 Kg, 3.38 km/s, 355 kN, 9:1 F+CH₄ Rocket into a 34.8 kg, 2.64 km/s, 285 kN, 5.58:1 F+NH₃ rocket. With the F+NH₃ being slightly smaller, how it's heavier might have to be with the pump.

The drone lost about 3 km/s and 2g acceleration although is now heavier and ever so slightly smaller. Dropping its cross section from 5.03 m² to 4.99m²


I might have to tinker around more with the ammonia engines size and shape to get the velocity higher, but so far it's not looking good. If the rocket has to get bigger, the gains in velocity might be offset in adding more armor to a longer/wider drone. Although, in capital application, its performance might not be so bad, but I would assume a methane NTR would outperform the F+NH₃ combustion rocket easily.

Final Final Final Edit: Got the NH3 rocket to 2.97 and 401 kN, and quite a bit smaller than the CH4 rocket... things are looking bright. The drone has increased acceleration but it still lacks delta-v. Perhaps F+NH3 rockets would be good for short range high acceleration missiles, but doesn't LOX+LH2 still have the highest thrust over all combustions?

Edit the Sixteenth: Sort of what I've learned from working with the NH3 I improved the CH4 and optimized it further. Now smaller, lighter, higher velocity, and more thrust than the NH3. Don't know if I can improve either further.

Guess I need to back and look at exhaust colors again lol. As for adding things I don't think qswitched would be too focused on letting us trick out our engine colors.

Does that mean Methane has better exhaust velocity over pentane?

Got around to Pentane NTR's looks like you loose around 0.7 km/s for 2 MN added

messed around with other -anes looks like RP-1/dodecane has more thrust for even less velocity, Butane is roughly the same as Pentane but less dense and cheaper, to minor hits to both velocity and thrust. Same goes for Ethane, but even larger hit hits to velocity and thrust but again cheaper and less dense.