Should jet engines be fixed or not,ever?

[Red Iron Crown]

But then you would lack a curve to scale ISP for designs that need ISP scaling - hence eventually you again would end up with a 3rd curve.

The Isp curve would still work for that.

[juanml82]

What you described is basically AJE: the over heating ,ramjet, etc. SSTO is still easy on Kerbin, and something like Skylon is possible on Earth.

The thing is: should it be easy if we're discussing realism? We won't know if Skylon works until it works. And we know none attempted to make an SSTO which carried the extra weight of engines unable to work in space, nor with large wings as it's usual in KSP - everything which was planned or went to space with wings (save Skylon, which isn't even at prototype stage yet) took off vertically. The wings were only to help with the landing, the typical KSP spaceplane ascend profile was never attempted IRL

[cantab]

Absolutely I think they warrant a rework.

The Isp issue is well known to be buggy, making that work properly should be fairly straightforward.

The speeds are also too high. If we were going by realism I would put the "basic jet" as not going much above Mach 1, and rename it the turbofan while I'm at it. The turbojet maybe Mach 2-3, so fighter jet or getting on for SR-71 levels of performance. The RAPIER needs to sit around the same level even though its prototype is expected to run on air up to Mach 5, unless one wants the jets to be totally uncompetitive for spaceplanes.

One more big issue that hasn't been mentioned much: the jet engines have way too high a TWR. They need it to push through the current soup, but it means they're as good as the rockets (which have a poor TWR compared to reality) and thus see use in vertical launchers. With the new aerodynamics hopefully being much less draggy the jets can be given a TWR nerf. Aircraft will still fly similar in level flight, but building vertical jetrockets will be much harder.

[NathanKell]

Fixing the Isp bug would only make jets even *more* broken, since their Isp curves have higher Isp at lower pressure, whereas in actuality they should have *less* thrust at lower pressure.

[NERVAfan]

The thing is, IRL you can't make an SSTO including jet engines.

And here's the deal with all the "realism" discussions. IMHO, there are people whose idea of "realism" ends up being "mods I like", be it FAR, DRE, TAC-LS or something else. But if we want to get into realistic air breathing engines, players shouldn't be able to make an SSTO with them, period.

The thing is: should it be easy if we're discussing realism? We won't know if Skylon works until it works. And we know none attempted to make an SSTO which carried the extra weight of engines unable to work in space, nor with large wings as it's usual in KSP

On Earth, yeah, but Kerbin orbital velocity is only like Mach 7-8.

[chaos_forge]

So would fixing the ISP code (and possibly giving jets a more realistic ISP curve) actually fix jets, or would we need a separate thrust/atmo pressure curve?

[juanml82]

On Earth, yeah, but Kerbin orbital velocity is only like Mach 7-8.

And on Earth you need some 9 km/s to make it to orbit, so many real life rockets probably wouldn't even need staging, or only two stages, to make it to LKO - yet staging rockets it's part of the game, and people are expecting rockets to be staged.

So yes, Kerbin is smaller (and unrealistically dense). Should "realism", however, scale down the parts so they behave in Kerbin in a fashion similar to how real rockets are expected to work on Earth?

[camlost]

Simply making thrust scale with Isp will not solve problem #1 mentioned in OP. Also I don't think that adding a third curve would suffice. Some kind of hard cap would be needed to nerf the thrust at low altitude, AJE users would know what I mean. And then, the key thing is that IntakeAir as a resource must be get rid of.

[Kegereneku]

I don't think we "need" to entirely get rid of that "intake resources", but simplify/rebalance it, definitely.

My though is that 1 intake should suffice for 1 engines, as long as it is at its nominal altitude.

If you use intake smaller than the engine then obviously you would need to put more of them to balance out.

Yet, this could be achieved by static limit.

The use as a dynamic resources would be for engine used outside their optimal parameter as a balance mechanism.

For example : to not make VTOL too easy without nerfing the engine (although this is a possibility) you would need more than 1 intake per engines (meaning needing to compress more air) to produce more thrust (up to an amount).

Obviously it might require other limit to avoid the same kind of intake spam we have now.