SSTO with the new RAPIER engine

[SpenSpaceCorp]

I am just wondering what everyone thinks of the new RAPIER engine in terms of its thrust and efficiency compared to the previous method of switching between jet and rocket engines. For my experience so far, a small SSTO with RAPIER engines typically needs at least two of them due to the reduced thrust. What do you guys think of it in terms of SSTO design changes and such?

[Tada]

Well, I´ve tested Sparrow by Zombiphylax in both RAPIER and classical version with turbojet and 2 LV-909 and performance is pretty similar.

Main advantage of RAPIER engine is, that it doesn´t need as much intake air as a turbojet, so you can get much higher much more speed without spaming intakes.

[Hodo]

To add to what Tada said, the RAPIER if run in FAR, also runs a lot faster than the turbojet, you can push it to Mach 6 with ease, but the stock turbojet is struggling at mach 6... trust me I managed to get one to mach 6.4 and it was only making 5kn of thrust.

[SpenSpaceCorp]

So if the RAPIER engine indeed requires less intake air, it would be better suited for say, Laythe?

[Hodo]

So if the RAPIER engine indeed requires less intake air, it would be better suited for say, Laythe?

It flames out the same as the turbojet, at 10% air required. But the difference is the RAPIER like all SABRE engines will switch over to closed cycle to turn into a rocket on its own, so there is little to no chance at a flame-out.

RAPIER/SABRE engines also continue to generate a decent amount of thrust at mach 6, or around 1900m/s, unlike a turbojet which is struggling to make thrust at those speeds.

[capi3101]

Haven't used it for a spaceplane, but I did make a proper SSTO probe with a RAPIER (swapped it out for a 48-7S and added a quad of intakes). Pretty neat getting it up to orbital speed at 28,000. I still wound up in orbit with moar fuel left with the 48-7S, though the RAPIER got me there faster.

[Grover]

ive got it well past this, flying horizontally at around 22km ALT, i cant remember the exact figure but i was pretty damn close to orbital velocity, at least 1700m/s (and burning like a kerbal barbeque)

i also only had two ram intakes and one rapier engine, so it wasnt a typical clipped intake cheater

[tavert]

Main advantage of RAPIER engine is, that it doesn´t need as much intake air as a turbojet, so you can get much higher much more speed without spaming intakes.

This is not correct in the stock game. The Rapier has the same Isp-vs-pressure curve as the turbojet, and requires the same ratio of intake air per unit liquid fuel. So for a given amount of thrust, the Rapier uses the exact same amount of intake air as a turbojet. The intake mechanics did change between 0.22 and 0.23, so turbojet aircraft don't need as many intakes as they used to.

[Dispatcher]

In real simulation terms, I've found that its easier for me to design and successfully orbit SSTO planes with RAPIER engines than is my use of a combination of jet and rocket engines.

For those interested, I've updated my engine comparison chart by adding the two RAPIER modes (see the sig line).

Edit: some people might be wanting their air engines to provide an electric charge. The RAPIER does not do this, in either mode.

Edited December 31, 2013 by Dispatcher

[bsalis]

I found a single RAPIER works just fine for an SSTO. Just need to match the weight to the available thrust.