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

[Vlk]

Personally - at first glance not as good as i expected. But this may be a good sign too: a new part that just replaces the others is not a good addition, it is better if you have to learn how to make use of its full potential. I just hope that i will find a better use

For my first experiment, i remade my favorite ssto. To be honest, judging by the numbers, i was able to expect the result. Its too heavy, and the thrust for the rocket mode is too big, compared to the thrust of the airbreathing mode. Maybe if i combine it with jet engines, and build a bigger ship?

old ssto:

rapier:

[AlexanderB]

Hm, I think they're great, for small SSTO's. 1 engine, 2-3 intakes, 1 or 2 fuel tanks, a capsule, some wings and wheels if you want a plane, or a decoupler and chutes for a jet-missile..

- Lift off runway (Thats the hard part, the thrust at low altitude is not so good.)

- Go to 23-30 km, build up horizontal speed. (Depends on intakes, really..)

- Nose-up and rocket power to a nice AP

- Circularise.

So typical SSTO, really. Its just an 'easy' 1-part solution for small craft, that otherwise demands multiple engines.. Its not super-efficient, but it works well enough.

[Peppe]

1.1 tons heavier (rapier vs lv-909 + 2 turbo jets).

I don't believe rapier is more efficient burning fuel at either stage. Though it is simpler to fly without having flame-out risk.

[Vlk]

So maybe it is just a way for casual gamers to taste the joy of sstoing?

Although, as i am thinking, this may be a bit more effective if you dont spam air intakes. - but until squad will not force me to stop the intake spamming, i will spam them (without part clipping)

[regex]

It is very easy to build a two-RAPIER SSTO with enough delta-V for some light LKO operations (makes a good crew shuttle) but I have a feeling that the old methods with multiple different engines will still be the way to go for anything larger.

[Stargate525]

It's... interesting. I'm a little surprised how much of a tail it produces without making power.

[Dispatcher]

I made a medium sized (3 engine) SSTO using the RAPIERs; worked pretty well. Prior to that I tested the engine using the same tests I'd done on all the other engines previously. I've updated the results and you may find them interesting. I also swapped out part size for electric charge generated. Note that the chart has two entries for it (the RAPIER): air and vac. See my sig line for the chart link.

Edit: Columns shifted; need to fix that.

Edit again: fixed.

Edited December 18, 2013 by Dispatcher

[oberlerchner123]

Not sure how good they are, but they're certainly a fun new toy to play around with.

First time I tryed them I used a Probe, orange tank, cubic octagonal struts, air intakes and 8 Rapiers, all in 1 stage, and I ended up in a orbit between Duna and Dres...

Then again you could do that before with intake spam.

They are pretty cool to use on small and simply built SSTOs though.

[Murph]

Great concept, great potential, but sadly the current implementation is mediocre at best.

They are horribly underpowered compared to turbojets, at all air-breathing altitudes. They are also worse for fuel efficiency than turbojets and aerospikes, in their respective modes, so any weight saving is negated by needing more fuel for the same overall capability. All of the testing I've done has shown them to be significantly worse than turbojets and aerospikes in pretty much every regard, at least for small spaceplanes (but I can't see how they would be any better for big spaceplanes). I'm very disappointed with them, can't see myself using them as-is for any practical purpose. Auto mode switching doesn't come remotely close to making up for their poor performance and fuel efficiency.

They do work, but you're just better off using turbojets and aerospikes, or use the B9 SABREs instead.

[Epthelyn]

They seem to require less IntakeAir before having to switch to the rocket mode. I was flying in level flight 29km with one R.A.P.I.E.R at maximum throttle and two intakes with a small SSTO. Going that high results in less thrust than ~20-25km up, but I wanted to push past the 15-18km ceilings I've achieved in the past.

The difference in power between existing jet engines and the R.A.P.I.E.R is definitely noticeable, but it's great not to have to worry about flaming out; I got my 2nd and 3rd ever SSTO aircrafts into orbit today within 20 minutes of each other, which implies that using the new engine is going to be better for small aircraft in Kerbin's vicinity, but nothing more; the single R.A.P.I.E.R struggled to push past 1.3km/s at the highest altitude, but the rocket is fairly efficient.

EDIT: @Murph

You say the R.A.P.I.E.R is underpowered, but all jet engines in KSP are ridiculously overpowered and require a manual switch, albeit a fairly simple one if you know what you're doing, from jet to rocket using multiple engines. Multiple engines = Bigger, which isn't always desired.

Edited December 18, 2013 by Epthelyn

[Darkeldar]

I had designed, made corrections and had successfully taken off with a two Rapier engined spaceplane in less than a half hour. So far seems a lot more stable than any of my Spike series craft, and actually doesn't need the entre runway to takeoff. I'm only using a single RAM intake per engine so far, but I won't know if I need more till later. But I had to cut the flight off quickly, as my lunch time was over, so I'll see if I can get 'er to altitude later.

[Franklin]

They are horribly underpowered compared to turbojets

Yeah, but the other jet engines are massively overpowered, so RAPIERs are more in line with a balanced model.

[Liowen]

Hmmm I put it on my small SSTO and I have to say the results are better than with the turbo jet/aerospike combo I had before. While I lack the initial speed the turbo jets offer at takeoff, I find it more fuel efficient than my previous version (Same overall design just swapped the turbos for RAPIERS and removed the aerospike and reversed the fuel lines). My orbit now is 100KM with more fuel and oxidizer than I had before, I bet my orbit could be even higher if I really wanted to push it.

This was my first orbit with it last night after I patched

And here is after a similar orbit and successful landing (my first successful landing!) note the fuel is still at a decent level.

What I have done is as I level out and get closer to the engine switch over I reduce throttle to half and put the nose up a bit. The speed does not drop, in fact it continues to gain speed and altitude at a good clip.

[Murph]

You say the R.A.P.I.E.R is underpowered, but all jet engines in KSP are ridiculously overpowered and require a manual switch, albeit a fairly simple one if you know what you're doing, from jet to rocket using multiple engines. Multiple engines = Bigger, which isn't always desired.

The turbojets may be a little overpowered, but not ridiculously so. Look up the numbers for the 1960s RR Olympus 593s used on Concorde, for example. Even if the turbojets are overpowered, they are what the RAPIER has to compete with in air-breathing mode, and it just doesn't come close to competing. As far as bigger/smaller, lighter/heavier goes, I'm not convinced that the RAPIER actually wins there, or even comes close to competing, since you're going to need more fuel for the same overall capability. The mode switching is irrelevant to me, as it's so simple and easy to get right once you know how to fly your plane.

[Eric S]

I think a lot of the fuss over the RAPIER engine has to do with people not realizing how many behind the scenes changes there were that affect all spaceplanes. My 0.22 spaceplane is doing far better in 0.23 than it did in 0.22 and even better than my first RAPIER spaceplane does. I was at about 30 km altitude, 2300 m/s, and both gaining altitude and accelerating off of a turbojet engine. I'm positive I've never seen that happen before.

[Xetalim]

These crafts all are over-engineered, one big 1.5 meter tank, 1 rapier, 1 command pot and 4 intakes are enough for LKO.

[Silverchain]

This RAPIER spaceplane worked first time, up to orbit and back (apart from a slight problem with the wing falling off on landing, but Jeb walked away...)

Much less finicky than using multiple engines, and it only needed a single ram intake. So easy to use, I like it!

Spaceplane Poignant Folly coming in to land.

[Liowen]

These crafts all are over-engineered, one big 1.5 meter tank, 1 rapier, 1 command pot and 4 intakes are enough for LKO.

If that is all you like in a your space planes that is fine, other like making things they like as well. Yours though I feel would have the problem of not being able to land or fly since you have no wings or landing gear.....but that might be over engineering in your eyes

[Shiftyeyesshady]

The thing I've discovered with it, and what a lot of people seem to have figured out as well, is that the RAPIER makes very small SSTOs possible when they really weren't before. They seem to work best on Small to Medium craft, but the older methods seem to work best once you start going big.

[Calorypher]

RAPIERs are perfectly balanced and totally not overpowered.

(rapierized Aeris 4A)

[Calorypher]

RAPIERs are perfectly balanced and totally not OP.

Modified stock Aeris 4A.

Accidentally double-posted :/

Edited December 18, 2013 by Calorypher

[Murph]

The thing I've discovered with it, and what a lot of people seem to have figured out as well, is that the RAPIER makes very small SSTOs possible when they really weren't before. They seem to work best on Small to Medium craft, but the older methods seem to work best once you start going big.

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.

[Stargate525]

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.

But the trade-off it that's it's impossible to get an asymetric flameout on the RAPIERs. You're gaining stability and ease-of-use in exchange for a performance hit. Which I think is fair. If you're comfortable using two engine types and swapping, then do that. For people like me, who hate having to monitor that (or have had no luck doing so), we can get SSTOs into orbit as well.

[SkyRender]

Definitely the best thing to happen to spaceplanes.

A vessel like this is far more complicated to pull off without the RAPIER engines, that's for sure!

[Vlk]

The thing I've discovered with it, and what a lot of people seem to have figured out as well, is that the RAPIER makes very small SSTOs possible when they really weren't before. They seem to work best on Small to Medium craft, but the older methods seem to work best once you start going big.

I have an ssto that uses ion engines once in atmosphere, inspired by this:

http://forum.kerbalspaceprogram.com/threads/48822-Flea-SSTO-(Jet-Fuel-to-LKO-or-Jet-Ion-to-anywhere-in-the-Kerbol-system)

I think just the mass of the rapier engine is almost the same as these micro-SSTOs