RAPIERs don't suck!: A complete performance evaluation

[Levelord]

With 1000's of hours of gamplay under my belt, I find that I prefer the Rapiers in most of my craft. If that makes me a newb, then so be it. Many also refer to grenade launchers in 1st person shooters as newb tubes. 1 on 1 sure, but if you manage to wipe out 2-3 in one hit, that is the proper and efficient application of ordinance.

The RAPIER is an excellent tool for new players. ≠ If you use the RAPIER you are a newb.

similarly,

The calculator is an excellent tool for people who are beginners in math. ≠ If you use a calculator you are bad at math.

I feel the need to make that clear because you are making a very large leaps in reasoning when you are reading my responses. From my calculator analogy it is a good tool for people like myself who are rusty in math, but calculators are also used by accountants, actuaries, physicists and other professionals to make their lives easier. However if you can do math calculations in your head, which while slightly harder, is a lot more efficient than punching in numbers in a calculator.

edit: Anyway to close my statements about the RAPIER, I simply said that it is used for different situations and craft demands than the Turbojet. It's weaker in small SSTOs, but it has its strengths for heavier craft and as an introductory engine. However, my main gripe was the unscientific/biased nature of how the comparisons were carried out, with proponents of the RAPIER deliberately pairing up the Aerospike engine (one of the least powerful engine with a terrible TWR) with the Turbojet, which basically cancels out any benefit the Turbojet engine provides in a spaceplane. I find it very odd that other engine combos like the LV-T30 and lv-909 were deliberately left out of their tests, because they synergize so well with the jet engines.

Edited February 3, 2014 by Levelord

[Wahgineer]

Maybe the space planes we're using with the RAPIER are too small? Or maybe, since we lack the proper parts to make practical space planes (sorry, but a 1 man space plane isn't really practical), the situation that will allow the rapier to come into its own hasn't yet arisen?

[Brotoro]

I've also used RAPIER engines on the SSTO rocket shown below (named the RASSTO), and they worked great for that application. This rocket was designed to ferry crew from Laythe surface to Laythe orbit (refueled in orbit), but I initially tested it at Kerbin and it managed to (barely) fly to Low Kerbin Orbit and back. It carries four kerbels in a Hitchhiker can. The ship uses two ram intakes for each of its four RAPIER engines.

The initial boost was done in air-breathing mode, of course (and I didn't experience the overheating problems at slow speeds that I've had with regular jet engines on SSTO rockets). The gravity turn was begun fairly early so that horizontal speed could be picked up while in jet-powered mode…but I didn't try to fly this long distances horizontally like a spaceplane. By the time I got it to flameout altitude (21 km on Laythe), it was flying at about 50 degrees from vertical and had about 550 m/s of horizontal speed. Then I switched over to closed-cycle mode and flew the rest of the way to orbit on rocket power.

The ship reached orbit with 540 m/s of delta-V remaining…so way more than needed to rendezvous with the space station.

The ship lands using parachutes and a little jet-assist. Because it has its fuel in orbit (the opposite of what you'd do on Kerbin) it is heavy when it lands. The side tanks are tweaked to have less oxidizer than liquid fuel to account for the fuel used during the air-breathing phase.

The RAPIER engines are particularly good for this application because there is no need to have other rocket engines on the ship...and the rocket engines required for this application would be fairly hefty ones (like two or three LV-T45 engines) …this is a rocket, not a spaceplane that only needs a little push from its rocket motors to make orbit. That's a lot of weight saved over my previous SSTO rocket design that combined jet engines and LV-T45 engines. Plus, this leaves the base of the rocket uncluttered so that an inflatable heat shield could be added there if reentry ever gets deadly (I did tests a while back with an inflatable heat shield on my SSTO rocket, and it was difficult because all the jet and rocket engines needed to be located radially instead of having the rocket engines in the center as I was used to doing).

So…I quite like the RAPIER engines for this application.

Edited February 4, 2014 by Brotoro

[numerobis]

You can view the rapier as being two parts in one:

1. A turbojet, scaled down to 1t and slightly nerfed (top speed 2200 rather than 2400, doesn't affect many planes at all).

2. A rocket with a mass of 0.75t, thrust of 175 kN, Isp 360s. That gives it the third-highest TWR, after the 48-7S and the mainsail.

The TWR and Isp of the rocket are fine; it's just much bigger than it needs to be. Consider that your plane got off the ground using 95 kN.

Brotoro: you should be able to fly at a much lower pitch to build up a lot more speed off your jets, and thus need almost nothing from your rockets -- I bet your lander can get back to Kerbin.

Edited February 4, 2014 by numerobis

[AmpsterMan]

I like the simplicity of using the rapier. I find trying to engineer around having to use multiple parts in other setups a bit of a headache.