So... what do you think of the RAPIER engines?

[Shiftyeyesshady]

Possibly for micro-planes, but I'm not convinced that they are even remotely competitive for small planes. The testing I've been doing is on a close-to-stock Aeris 4A, which I'd call fairly small. For non-RAPIER, I've been using a twin turbojet + single aerospike config. For RAPIER, twin with no middle engine. In practical terms, the RAPIER version has about half the spare fuel once it is established in a 100x100 orbit, so significantly less overall capability. I guess their winning case might be something tiny enough that a single 100kN engine works well for atmospheric flight.

I would not call a three engine SSTO a small SSTO, or even most two engine SSTOs.

[Murph]

I would not call a three engine SSTO a small SSTO, or even most two engine SSTOs.

It's small by my reckoning, fighter-style/size/weight. Medium to me is 50-100t, large 100-250t, huge 250t+.

[The Jedi Master]

So. Underpowered.

Seriously, I had SIX, with a mainsail in the middle, on one of my rockets, and it took a couple seconds to even get up to 1 meter per second!

[Rocket Farmer]

@jedi master

You do know it takes a couple of seconds for air breathing engines to spool up to full power right? They aren't instant 100% power like rockets......

[The Jedi Master]

@jedi master

You do know it takes a couple of seconds for air breathing engines to spool up to full power right? They aren't instant 100% power like rockets......

...

I feel so stupid now...

[leax256]

built a stto with them on my first try.

[Zephram Kerman]

It seems to me the Rapier engine is a game design decision. It's an easy way for new players "how to SSTO" without flameout, complicated action group schemes, etc. If the Rapier outperformed all other engines, we would never use anything else. But this way, there is room to increase performance by trying harder.

[Duxwing]

I see great Laythe applications for the RAPIER: reducing craft size by reducing the number of necessary engines and fuel tank types decreases payload mass and thereby greatly increases tug dV.

-Duxwing

[Aragosnat]

A little thing I have found out or at least noticed is that the new engines will use the Jet fuel tank. So if one wanted to just use jet fuel the jet aspect (not like anyone would want to), one can. Or if you did like I have done in this picture:

Then one can have it so they don't need to worry about having excess Oxi fuel.

Edit: This ship can make it to orbit with plenty of rocket fuel to spare.

[Wheffle]

In some situations I think they'll be more efficient or just as efficient as traditional aerospike + turbojet combos, but they seem to eat about the same amount of fuel for me as the traditional setup. I think there's some value in the simplicity, though. You don't have to worry about fuel lines and two different sets of engines.

[Zephram Kerman]

Gratuitous screenshot...

[Brotoro]

Cool plane, Zephram.

[Zephram Kerman]

Cool plane, Zephram.

Thanks Brotoro!

[Mephane]

I was pleasantly surprised how little intake air it needs to still operate. I managed to still run on air at ~30km altitude with 4 radial intakes on full throttle, that's like 0.05 intake air available, maybe less. Normal jet engines flame out at 0.1.

[Murph]

I was pleasantly surprised how little intake air it needs to still operate. I managed to still run on air at ~30km altitude with 4 radial intakes on full throttle, that's like 0.05 intake air available, maybe less. Normal jet engines flame out at 0.1.

That's not so much a feature of the RAPIER. The resources system was re-worked to fix the case where the last few units didn't drain out of tanks properly (intakes are self-refilling fuel tanks, effectively). The result is that flame out from intake air starvation is at higher altitude for all engine types, as long as you have good air speed driving the intakes (and a small angle of attack).

I'm not certain, but I think the air/fuel ratio for RAPIERs is either the same or roughly the same as for jets.

[Boamere]

The only change i want them to make is that they make the rapiers a little more powerful at launch and more powerful at high altitudes, e.g 120 at low level and 200 at high level (or at least something like that)

[El wonso]

I think rapiers are great, I choose them over jets + rockets design.

[Liowen]

The only change i want them to make is that they make the rapiers a little more powerful at launch and more powerful at high altitudes, e.g 120 at low level and 200 at high level (or at least something like that)

While that sounds good I believe there could be small problems with doing that. It could become a direct replacement for a turbo jet motor or more powerful space engine, the RAPIER is more of a meeting in the middle. It is good, but not great, as a standard jet motor while also being good, again not great, as a rocket engine. If you increase the takeoff speed it would have to be balanced on the higher end thrust being lowered, this is why I like it as a slower engine to start and it builds up its thrust as it goes.

[longbyte1]

Quite frankly, the model looks an SAS module strapped glued to a sawed-off radial engine body (the one with cowls). I think the model should look a bit more dynamic in shape so that it doesn't look like a big cylinder.

Also, it doesn't sound very good at 100% throttle.

Edited December 19, 2013 by longbyte1

[zekes]

Anyone here replace the engines on the Debulist with a Rapier? I will, see if it helps or hurts....

[lammatt]

it's OP

needs to be a lot heavier

[panfish5]

I actually love it. Maybe it would be cool if they were 2 tons maybe but anything more just makes them inferior to their use.

[Armchair Rocket Scientist]

Cockpit + rapier + 2 ram air intakes = 2060 m/s at over 30 km (with manual mode switching and engine throttled down to prevent flameouts). The plane had around 800 m/s once in a 100 km orbit... and a 4:1 TWR. Admittedly, I could probably have done the same thing with a turbojet and 2 48-7S engines.

I can see these getting a lot of use on "rocket-style" SSTOs, but a spaceplane has no need for that much thrust outside the atmosphere. The Aeris 4A has about half as much thrust in rocket mode as jet mode, and there are people out there using RCS, nuclear engines, or ion engines as their entire "non-airbreathing" power source.

[Pds314]

Yes, they are heavy engines. But they are not as heavy as the equivelant thrust LV-T+turbojet combination. They are somewhat heavier than the equivalent 48-7S+turbojet combo, but they have a better Isp.

[Stargate525]

I've heard people screaming that they're OP, and others yelling that they need to be buffed before they'll even consider trying them again.

Which tells me that they are probably spot on.