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


Vlk
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What I meant to say is that if it were at least *slightly different* than the turbojet, then there would be interesting design niches. What if the RAPIER had worse performance than the turbojet at mid altitudes but better performance at high altitudes? What if they nerfed the turbojet to lose thrust at 1,500 m/s?

It would be nice, as a designers, for there to be some 'crossover' speeds/altitudes where we could play with the benefits/costs of carrying multiple engine types around.

Sort of like what they did with the Basic Jet. It could go Basic Jet < Turbojet < RAPIER.

The turbojet is about right. If you use FAR+DRE, you will find out HOW limited that thing really is. Around mach 3.5 it becomes weaker, and by mach 5 you might as well get out and push. The RAPIER and SABRE are great for those applications that need to go MUCH faster.

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Here is a tip if you do not like it you do not HAVE to use it, since this is a single player game being overpowered is kind of irrelevant honestly.

Tell that to the devs who spend hours ensuring that parts are balanced in relation to each other since clearly balance isn't an issue in single player games.

Also, you have proven that KSP isn't single player by posting this message on the forums, and hence interacting with other players.

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What I meant to say is that if it were at least *slightly different* than the turbojet, then there would be interesting design niches. What if the RAPIER had worse performance than the turbojet at mid altitudes but better performance at high altitudes?

The problem with this is that you just wouldn't use turbojets on your designs, then. Just like right now you don't see a lot of people using basic jets, since you're spending so little time below ~2000m that its low-altitude benefits just aren't useful for anything other than VTOL landers. I'm just not sure there are enough variables to make the RAPIER truly unique; they could tweak things like the air:fuel ratio, the speed at which it ramps up the thrust, vectoring ability, heat generation, and so on, but if they make it any more or less viable at high altitude then you'll have people either use it constantly, and never touch the turbojets, or go back to the old turbojet+rocket combos. I'm just not sure they can maintain that balance using those minor variables.

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I take back my earlier comments about the RAPIER killer app being NERVA powered planes. There's a much better way to get those working. Just use the standard turbojets, but take off with most of the fuel tanks empty (yay tweakables!), making the plane much lighter and giving the NERVA less to do.

Right now, I'm struggling to find a use for the RAPIER in my space programme. Tweakables and the fixed intake system make NERVA planes/larger craft more practical with the good old turbojet and no other rocket engines (just refuel in orbit at a space station - you no longer have to design a plane that can haul its full weight up to orbital speed), and for small stuff, the turbojet+2 LV 48-7S cluster owns.

This engine really is not unbalanced. It's a not very good alternative to the turbojet + A.N. Other engine(s), where the other engines depend on your requirements.

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Just use the standard turbojets, but take off with most of the fuel tanks empty (yay tweakables!), making the plane much lighter and giving the NERVA less to do.

That's fine for taking off from Kerbin, but it doesn't really help you as much taking off from somewhere like Laythe. Sure, you could drain most of your tanks at whatever space station you put in Laythe orbit, but it's not quite the same thing, and it's not really feasible until you have a station there in the first place.

The fact is, I've run into a lot of situations where having an extra burst of rocket power, above and beyond what an LV-N produces, keeps my spaceplanes from crashing into whatever airless moons they're landing on if I misjudge the descent. In 0.22 I'd use the same rocket engines needed to get to Kerbin orbit to do that; in 0.23, a single RAPIER fills the same niche, for only a minor 0.55-ton mass increase and a slight reduction in turbojet thrust. Like I said before, you don't need to replace ALL turbojets with RAPIERs, but they're very handy to mix together on larger designs.

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That's fine for taking off from Kerbin, but it doesn't really help you as much taking off from somewhere like Laythe. Sure, you could drain most of your tanks at whatever space station you put in Laythe orbit, but it's not quite the same thing, and it's not really feasible until you have a station there in the first place..

It doesn't need to. Orbital speed at Laythe is much lower. Don't need to suck on tenuous atmosphere while fighting gravity quite so much. Hell, just climb at 30 degrees under full power, never level off, go suborbital and circularise using the NERVA. Won't work on Kerbin, but Laythe doesn't need all the delta vees.

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My opinion on the RAPIER engines is kinda so-so. They're fun from a "Shoot this into LKO" standpoint, but they take a lot of the fun out of the attempt to make good spaceplanes.

Not SSTO's. Spaceplanes. SSTO's are fun, but once you build two or three of 'em, there's no need to really keep doing it. One of the things I hate about the RAPIER, and I'll say it now, is that there's no power generation. At all.

Now I know what you're thinking. "Mad, that's not a problem, use RTG's and Solar Panels."

Here's the thing: I only need that electrical generation when I'm under active engine power. After that point, I'm in orbit, where it's now safe to deploy my folded panels, rather than covering my plane in those obnoxious little panels. So as I'm ascending to orbit, I'm bleeding power the whole way up because where my Jet Engine or Turbojet might be providing some charge, the RAPIER is saying NOPE! to that.

I took care of the low thrust on the runway issue with a simple Sepratron Assisted Take Off. They don't weigh much when empty and have just enough kick to send you screaming off the runway faster than Jeb can eat the snacks in the cockpit. I can handle the fuel-hungry nature. Most of my designs use the LV-T45 engine to get into orbit, so I have fuel to spare. Autoswitching makes my life easier with not having to waste two action groups, one to switch jet, and one to switch rocket, as well as not having to time the transition from jet, to hybrid, to rocket only, and back again.

So in the end, I kinda like the RAPIER, but I might go config-bashing and throw a generator on the bloody thing, because it's rubbish that both the Jet and the Rocket side of the engine produce nothing useful. A jet makes electricity, and my tried and true LV-T engines produce electricity. So where's the juice?

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Tried simple SSTO now.

This new RAPIER engine combines strengths of turbojet and aerospike without any of their weaknesses.

It's powerful. It's gimballed. It's have no thrust lag. It's lighter than jet+rocket with 150kN thrust. It's short. It allows mounting things on its surface.

And it have nice humming sound in place of nasty jet yowl :)

So using it looks almost like cheating. SSTOs are ultra-easy to build now.

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Also, I have a strange feeling that air consumption is broken somehow when tweakable thrust limiter is used.

(look at engine mode, intake air, thrust and throttle)

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Edited by koshelenkovv
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Tried simple SSTO now.

Also, I have a strange feeling that air consumption is broken somehow when tweakable thrust limiter is used.

(look at engine mode, intake air, thrust and throttle)

Air breathing engines now have a second limiter, apart from the tweakables, that responds automatically to available intake air. Hence the thrust that your engine is generating is less than the full value displayed in engineer readout. The intake air value in the resource tab is only displaying the stored air in the intakes, not how much they are generating.

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Air breathing engines now have a second limiter, apart from the tweakables, that responds automatically to available intake air. Hence the thrust that your engine is generating is less than the full value displayed in engineer readout. The intake air value in the resource tab is only displaying the stored air in the intakes, not how much they are generating.

I understand now why Engineer says 100.678 kN and right-click popup says 94.5 kN.

And right, IntakeAir resource shows that there is no air available, but obviously, there is no depletion or replenishment occurs (last 0.00 of three).

My fault, I was confused by zero air amount in storage.

So there is just an equilibrium of inflow and comsumption.

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I understand now why Engineer says 100.678 kN and right-click popup says 94.5 kN.

And right, IntakeAir resource shows that there is no air available, but obviously, there is no depletion or replenishment occurs (last 0.00 of three).

My fault, I was confused by zero air amount in storage.

So there is just an equilibrium of inflow and comsumption.

Right.

I think a lot of the people complaining that Rapiers are overpowered have not noticed that this second limiter applies to all airbreathing engines. I think that they go down to 10% thrust before they flame-out.

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Right.

I think a lot of the people complaining that Rapiers are overpowered have not noticed that this second limiter applies to all airbreathing engines. I think that they go down to 10% thrust before they flame-out.

But they do it asymmetrically, if you have more than one, so use a GREAT BIG RUDDER O' DOOM on your twin-engined planes, people!

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But they do it asymmetrically, if you have more than one, so use a GREAT BIG RUDDER O' DOOM on your twin-engined planes, people!

An easy way to have them switch all at the same time is to action group your intakes -- just like you would on normal SSTO. Just shut the intakes and both engines will switch modes at the same time.

It is like regular SSTO, but you don't have to action group the engines.

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I am not a new player. I started in .17. I have tried dozens and dozens of times to build a functioning SSTO before .23 and had a single success (with a single-Kerbal SSTO with no docking port and barely enough fuel to deorbit). I can now build functional SSTOs and SSTO spaceplanes thanks to the RAPIER and I couldn't be happier. I think that the lack of an electrical generator and their propensity to overheat/explode more than a Mainsail makes up for their ease of use. Hooray! Thanks, SQUAD!

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Here's the thing: I only need that electrical generation when I'm under active engine power.

But what do you need it FOR? Seriously, I'd like to know. Flywheels use a bit of power, sure, and so do lights, but it's not like you've got a tremendous energy drain going on your way up. Those small draws don't require much; stick a single inline battery on your design and you're fine all the way to orbit, and even a single fixed solar panel should be enough to feed those. My own design has an RTG hidden inside the cockpit, so that I can't get completely stranded somewhere if I leave the lights on, but you don't even need that in practice. The only reason my own design has a metric buttload of solar panels and batteries is that I use hybrid ions from a mod instead of the LV-Ns, and I've got ion engines on the wingtips (which I obviously don't use in-atmosphere). But a stock version of the same design needs almost no electricity at all.

To me, the lack of electricity generation is an utterly trivial drawback of the RAPIER, far less important than its flexibility and vectoring. The 15% thrust loss and higher weight are significant drawbacks, of course, but depending on your design those might still come out ahead overall.

(Also, a long time ago there was a mod that added a very nice larger fixed solar panel; 7 times the weight of the dinky little panel, for 5.5 times its electricity. I use those quite a bit.)

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To me, the lack of electricity generation is an utterly trivial drawback of the RAPIER, far less important than its flexibility and vectoring. The 15% thrust loss and higher weight are significant drawbacks, of course, but depending on your design those might still come out ahead overall.

The lack of electricity from them is indeed the most trivial defect with them, but it's also pretty stupid for them not to generate, IMO. You also forgot their relatively poor fuel efficiency in the list of flaws with them. As for vectoring, that's not a major feature from my point of view, not actually needed with a reasonably balanced plane design. I'd gladly trade vectoring for thrust and fuel efficiency to make them a useful alternative to turbojets+aerospike.

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An easy way to have them switch all at the same time is to action group your intakes -- just like you would on normal SSTO. Just shut the intakes and both engines will switch modes at the same time.

Ooh, clever!

Alternatively, you could just set an action to switch modes...

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Ooh, clever!

Alternatively, you could just set an action to switch modes...

I believe if you switch the modes the intakes are still on, and if you do it manually you will have to remember that it won't switch back on their own after that. The second part I know as I did that when I first tried them, but if the intake is toggled I believe it would switch itself once they are back on. I could be wrong though as I honestly tried to do that as I stopped messing with my SSTO for now.

Tell that to the devs who spend hours ensuring that parts are balanced in relation to each other since clearly balance isn't an issue in single player games.

Also, you have proven that KSP isn't single player by posting this message on the forums, and hence interacting with other players.

As what you brought up about the devs is different than what the player believes is overpowered. If a dev came out tomorrow and said "Hey we fudged the code making the engine too strong/weak" I would not have an issue with it as they have a better understanding of how they want their game to work....not the players. As for forums being the multiplayer aspect for gaming I find it a bit harder to agree with, though to me I would classify more as a chat room than a game mechanic. I can choose to stop coming here and it has zero effect on what I do in game. On the flip side though if I stop going into a multiplayer game (where no other feature is available like League of Ledges) I have no game to play.

Hopefully that makes sense tired and medicated is not helping my thought process tonight at all. ;.;

Edited by Liowen
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Base on my own test flight, the new engine has a very high tolerance to the low air intake condition. Even 0.03 air allow the engine maintain power with air breathing mode. This is excellent! An old jet engine will be shut down when air drop below 0.10 if thrust is on max but the rapier will not. However, it seems if you have dual rapier and let them running in a low dense atmosphere, they sometimes have different thrust and may change your direction. They are still running but with different output. I really like the light effect when they are running at full thrust but the sound effect sound quite odd to me. I don't like it. Never mind, Rapier is a good engine and it provide us many new possibilities on both rockets and spaceplanes design .

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An old jet engine will be shut down when air drop below 0.10

Not true in 0.23. Turbojets and RAPIER are pretty close, if not identical, in terms of intake air starvation. The resource flow system changed significantly between 0.22 and 0.23, so all air breathing engines have had their air starvation behaviour improved. Also, the number shown in the resources tab isn't actually the intake air available, it's the stored intake air (you can think of that as positive pressure in the air system, more or less). The available intake air is more hidden, and based on the external air speed, angle of attack (orientation of the intakes relative to prograde), and altitude. The number in the resources tab does give you a clue that you're getting close to starvation, but it's not quite the same as the fuel hitting 0.

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Not true in 0.23. Turbojets and RAPIER are pretty close, if not identical, in terms of intake air starvation. The resource flow system changed significantly between 0.22 and 0.23, so all air breathing engines have had their air starvation behaviour improved. Also, the number shown in the resources tab isn't actually the intake air available, it's the stored intake air (you can think of that as positive pressure in the air system, more or less). The available intake air is more hidden, and based on the external air speed, angle of attack (orientation of the intakes relative to prograde), and altitude. The number in the resources tab does give you a clue that you're getting close to starvation, but it's not quite the same as the fuel hitting 0.

I have not yet test the jet in 0.23. If what you said is true, it would be a great improvement. Thanks for the information, I will test the jet ASAP.

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