Jet engines overpowered?

[Comrade Jenkens]

I've been playing around with spaceplanes recently and I've noticed that the jet engines seem to be much more powerful than their real life counterparts. While making a jet fighter the thrust to weight ratio is often 3 or 4 while the best modern fighters have a trust/weight ration of just over 1. Is this an intentional balance choice or will it be changed in future versions?

[entaran]

TV Aerospace fixes this. They're definitely way OP.

[TheDarkStar]

It's a balance choice, since the aerodynamics are not that good yet.

[Autochton]

I would suggest Ferram's Aerospace Research with TV Aerospace. Installation if tricky, however, as the newest FAR uses ModuleManager, and TVAero need some changes to it to be fully compatible. However, once installed, jet engines (and wings and everything else aerodynamic) behave in much saner ways.

[afranius]

I've been playing around with spaceplanes recently and I've noticed that the jet engines seem to be much more powerful than their real life counterparts. While making a jet fighter the thrust to weight ratio is often 3 or 4 while the best modern fighters have a trust/weight ration of just over 1. Is this an intentional balance choice or will it be changed in future versions?

Modern jets have TWR about 1.0, and engines with about 100 kN of thrust. The KSP engines have 100 kN of thrust (150 for turbojet), so that's pretty close. I guess they are a little bit light, but the way KSP handles jet engines is a little weird anyway, since the "engine" is just the nozzle, and the engine itself seems to just be hidden somewhere... maybe that's why it has such strange TWR?

[Whackjob]

Do the engine parts (air scoop, turbine, thruster) have to be connected in any particular way to function? I know almost nothing about setting up these things. And the few craft I've made with wings appear to never have any lift.

[GJames]

Do the engine parts (air scoop, turbine, thruster) have to be connected in any particular way to function? I know almost nothing about setting up these things. And the few craft I've made with wings appear to never have any lift.

The air intakes can go anywhere on the plane. Then just stick a jet engine on the back and your good to go. Best bet is too start small and take it from there once you can get into the air.

[UmbralRaptor]

Yeah, stock jets are a tad overpowered. Over a large chunk of their range, effective Isp is >20,000 s, and effective TWR (even including ram intake spam) is >8. Also, there's the whole reasonable efficient operation while hypersonic thing, so you can fly east until you hit orbit...

Do the engine parts (air scoop, turbine, thruster) have to be connected in any particular way to function? I know almost nothing about setting up these things. And the few craft I've made with wings appear to never have any lift.

IntakeAir sort of like RCS or Xenon in that engines can use it from anywhere on the craft. For lift, I think you always need a non-zero angle of attack.

[Whackjob]

How about that radial engine looking thing? Are those requred?

#EDit: Radial Engine body. I assumed one of those was needed along with the air intake. But it IS an air intake. Correct?

Edited June 25, 2013 by Whackjob

[UmbralRaptor]

How about that radial engine looking thing? Are those requred?

#EDit: Radial Engine body. I assumed one of those was needed along with the air intake. But it IS an air intake. Correct?

The radial engine body is purely a structural part; it's the engine nacelle that's an intake, and neither are required.

[rodion_herrera]

This is precisely why you see those insane lifter designs with tons of jet engines and intakes on them *snicker* They actually work!

[Jason_25]

Modern fighter TWR can be way over one. F-22's empty TWR is closer to 1.6. I would hate to see the jet engines become less powerful. We don't even have an afterburning turbofan yet!

Already it is very hard to make a heavy fighter with low lift that has good low altitude performance with 2 engines or less. It's almost a requirement to make some big winged WW2 piece of crap. We need some engines that are powerful enough to lift a heavy fighter straight off the runway vertically.

To me, the jet engines are pathetically weak right now.

[UmbralRaptor]

I would hate to see the jet engines become less powerful. We don't even have an afterburning turbofan yet!

Between 0 and 2 km/s, the stock turbofan puts out 112.5-225 kN. At worst, this is slightly better than the non-afterburning thrust of various high performance engines. At best, it beats the afterburning ones. (compare with the Soloviev D-30, Pratt & Whitney J58, and Pratt & Whitney F119). I suspect that the actual issues are with how poor lift is with stock aerodynamics and perhaps how massive some stock parts are.

To me, the jet engines are pathetically weak right now.

You do realize that the current airspeed record in KSP is ~2350 m/s, right? And that a single turbofan can lift ~7 tonnes of payload into a 30 x 70 km orbit?

[Themohawkninja]

While compared to real life engines, they are much more powerful, as far as game balance is concerned, they seem to be alright.

[Jason_25]

Between 0 and 2 km/s, the stock turbofan puts out 112.5-225 kN. At worst, this is slightly better than the non-afterburning thrust of various high performance engines. At best, it beats the afterburning ones. (compare with the Soloviev D-30, Pratt & Whitney J58, and Pratt & Whitney F119). I suspect that the actual issues are with how poor lift is with stock aerodynamics and perhaps how massive some stock parts are.

You do realize that the current airspeed record in KSP is ~2350 m/s, right? And that a single turbofan can lift ~7 tonnes of payload into a 30 x 70 km orbit?

Good points on the poor lift and awkward parts. I would still like to see a better variety in jet engines. From long thin turbo ramjets like the SR-71's J-58 to the huge 747 turbofans.

Yes I know about the insane high atmosphere performance. My Ghost Next will probably do that speed. It's the low altitude performance that is lacking but all that could actually be fixed with the addition of an afterburner.

[Ganymede]

The engines seem to work along with the aerodynamics of the game. When the aerodynamics get updated, the engines' power will change too.

F-22's empty TWR is closer to 1.6.

How do you have an empty TWR? You need fuel to get any thrust.

[arq]

Yeah the main issue right now for me is the pathetic lift provided by aerodynamic surfaces. To make any non-micro craft (even a small SSTO) requires an inordinate number of wings, to the point where I often have a hard time finding places to put them (without clipping). The craft comes out looking like a weird hairstyle than a plane.

You can judge the lift of a plane by your angle of attack (angle between heading and prograde) in steady flight. As it stands now, the high-TWR is necessary for jets because (without massive numbers of wings) they fly as much like rockets as planes, the larger planes that I make regularly have 20+deg AoA at low altitudes (where the TWR is low because of altitude effects on the engines).

EDIT: To be clear, when I say 'massive' numbers of wings, I mean more than the 14 already there...

I've started using the procedural wings mod and that helps a little with the aesthetic/partcount issues (though really partcount is rarely an issue for planes because they're typically pretty small), just make a few really big ones and you're in better shape. Though with stock aerodynamics it's still pretty underwhelming.

Edited June 26, 2013 by arq

[Fel]

TurboJet Engines have their velocities defined in the cfg file...

It is all very confusing, but the turbo-jet engines seem to have some kind velocity table which limits at 2400.

It only follows that turbojets are designed to "magically change into super fast physics defying objects to enable spaceplanes"

I mean, near 2400m/s in "pea-soup-atmosphere" is saying something.

[Jason_25]

The engines seem to work along with the aerodynamics of the game. When the aerodynamics get updated, the engines' power will change too.

How do you have an empty TWR? You need fuel to get any thrust.

That's obvious, but if you check the Wikipedia article it shows around 1.2 with half fuel AND a weapons load. Earth is bigger than Kerbin so planes have larger tanks generally and we have no weapons to load in the stock game.

[karolus10]

Jet engines TWR is larger than IRL, also Rocket engines TWR is 4-5x worse than IRL engines.

[Ganymede]

That's obvious

I'm just saying that it's pointless to use an aircraft's empty weight in a TWR since it will never be usable.

[Jason_25]

I'm just saying that it's pointless to use an aircraft's empty weight in a TWR since it will never be usable.

I see what you are saying, but I wanted to retort with a dramatically large number.