[1.0.5] Advanced Jet Engine v2.6.1 - Feb 1

[Dhan]

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Got some pretty sweet results with a basic ramjet design

[Hodo]

http://imgur.com/a/xHg4L

Got some pretty sweet results with a basic ramjet design

With the stock sized Kerbin I can launch a brick into space using a ramjet and enough SRBs.

[Hodo]

Hodo: Thrust was not greater than drag. Since you had the FAR Flight Data window up, we can prove it.

In pic 5, the ramjets are creating 328.4 kN each, for a total thrust of 656.8 kN. As for drag:

D = Q * Cd * A

D = 218,680 Pa * 0.035 * 133.7 m²

D = 1023.3 kN

So in pic 5 you've got a 366.5 kN deficit.

In pic 6, the ramjets are creating 289.8 kN each, for a total thrust of 579.6 kN. ANd your drag:

D = 162,330 Pa * 0.035 * 133.7 m²

D = 759.6 kN

So in pic 6 you've got a 180 kN deficit.

In both cases, FAR's drag overpowers the engine's thrust and you should decelerate. I'm curious, what method were you using to calculate drag that gave you answers less than your thrust?

Whatever the case, you're flying way too low in both of those cases. Frankly, the fact that you got a plane that big up to Mach 2 at those altitudes is astounding in itself, considering the only plane of comparable size was the Concorde, and that needed to get above the altitudes you're at before it even went supersonic.

Still doesn't explain why the engines are losing power.

When the pressure is over 200kpa and the velocity is well over 600ms, the engines should not lose power.

[NathanKell]

Of course it's losing power; ramjet power is dependent on airflow into the intake, so every m/s of speed you lose (flow = area * velocity * density), that's lost thrust, then you lose more speed, and thus more thrust, until thrust and drag are equal, your speed stays constant, and thus your thrust stays constant.

[Tidus Klein]

Of course they use LH2+LOx, are you sure you have all mods correctly installed, including MM?

Yes every thing is installed right,

I changed all the mm files to use stock fuel because I hated real fuels

So Lh2 engines use more fuel then LOx?

Well that's something KSP lied to me about.

I guess I'm just used to the way KSP engines work:)

Which we all know don't really follow real life

Edited April 28, 2014 by Tidus Klein

[MAKC]

@camlost

Ignore my "bug" report, it was a MM problem. HotRockets effects show up now and the D-30F6 works like a dream and does indeed overheat past Mach 2.8, just like the real thing. Great job!

[camlost]

Yes every thing is installed right,

I changed all the mm files to use stock fuel because I hated real fuels

So Lh2 engines use more fuel then LOx?

Well that's something KSP lied to me about.

I guess I'm just used to the way KSP engines work:)

Which we all know don't really follow real life

The problem with KSP is a bug with fuel flow calculation that makes airbreathing engines 16x more effective than its nominal Isp. The SABREs should use a lot of LH2, because of its low density. So converting SABRE to LiquidFuel/Oxidizer is acturally a buff.

[Tidus Klein]

the problem with ksp is a bug with fuel flow calculation that makes airbreathing engines 16x more effective than its nominal isp. The sabres should use a lot of lh2, because of its low density. So converting sabre to liquidfuel/oxidizer is acturally a buff.

still sucks down the fuel thou

[ialdabaoth]

I have a pair of requests for this mod:

1. Currently, air intakes check for whether the incoming air has oxygen, and refuse to intake air if it does not contain oxygen. (This can be disabled with a cfg change).

This is clearly wrong; the engine itself should be what's doing the check for oxygen. Could you please add a checkForOxygen flag, which causes the engine to produce no thrust (but still consume fuel) if this.vessel.mainBody.atmosphereContainsOxygen is false?

2. Could the mod check for fuel density, and change the engine's thermal and performance characteristics if (for example) liquid hydrogen is being used instead of kerosene?

Edited April 29, 2014 by ialdabaoth

[camlost]

I have a pair of requests for this mod:

1. Currently, air intakes check for whether the incoming air has oxygen, and refuse to intake air if it does not contain oxygen. (This can be disabled with a cfg change).

This is clearly wrong; the engine itself should be what's doing the check for oxygen. Could you please add a checkForOxygen flag, which causes the engine to produce no thrust (but still consume fuel) if this.vessel.mainBody.atmosphereContainsOxygen is false?

2. Could the mod check for fuel density, and change the engine's thermal and performance characteristics if (for example) liquid hydrogen is being used instead of kerosene?

1. That's hard-coded already. The air intakes has no physical meaning in AJE. I assume 100% total-pressure recovery for all intakes at all conditions, which is overpowered, I know.

2. That can be done by changing Kerosene to LiquidH2 and use fhv=48900

[NathanKell]

camlost: re 2, the point that ialdaboath is making is asking whether you can make AJE check that.

Let's say I have an engine with Kerosene.

AJE should detect the propellant is kerosene, and use kero's fhv.

If I switch the propellant to LH2, AJE should detect it's LH2 and use fhv=48900.

The use case: adding RF switchable-fuel-mode support to AJE engines.

[camlost]

camlost: re 2, the point that ialdaboath is making is asking whether you can make AJE check that.

Let's say I have an engine with Kerosene.

AJE should detect the propellant is kerosene, and use kero's fhv.

If I switch the propellant to LH2, AJE should detect it's LH2 and use fhv=48900.

The use case: adding RF switchable-fuel-mode support to AJE engines.

Sure that can be done, but I think that's non-existent in reality

[NathanKell]

It absolutely is, yes.

Although IIRC wasn't one of the proposed engines for OXCART originally LH2 and then reconfigured for kero? So maybe not.

(The point is that it's nice to be able to model more engine types with fewer parts, basically; and hey, the LR-87 is a nice example of how not-too-hard it is to switch fuel modes for a RL rocket engine.)

[camlost]

A proof that the rotary wings handle well. Much better and more realistic than the original model. Feels sorta like flying in ArmA

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[Phredward]

Hi! I'm trying out this mod with RSS, and I notice that the jet engines are no longer gimbalable. I was wondering if you would consider adding some gimbaling back in.

Obviously "gimbal" isn't quite the realistic term, but I imagine that some of these engines are thrust vector capable, or could be made so if someone had a real-world need. In KSP, I definitely have that need: I'm trying to use jets as my first stage lifter, and the vehicles quickly flip over if there's nothing to stabilize them. Even with regular RSS one would need to be careful during an ascent, but without any thrust vectoring it's impossible.

[Guest]

How about some winglets for control. Few jets have TVC IRL, and only a handful of them in both axes.

[MAKC]

Hi! I'm trying out this mod with RSS, and I notice that the jet engines are no longer gimbalable. I was wondering if you would consider adding some gimbaling back in.

Obviously "gimbal" isn't quite the realistic term, but I imagine that some of these engines are thrust vector capable, or could be made so if someone had a real-world need. In KSP, I definitely have that need: I'm trying to use jets as my first stage lifter, and the vehicles quickly flip over if there's nothing to stabilize them. Even with regular RSS one would need to be careful during an ascent, but without any thrust vectoring it's impossible.

I think it should be possible to do yourself. Not sure how it works with HotRockets but you can look at rocket engines using HotRockets and copy their gimbal code to the jet engines.

[MAKC]

A proof that the rotary wings handle well. Much better and more realistic than the original model. Feels sorta like flying in ArmA

Does it have some sort of plugin for automatic tail rotor thrust & yaw control? Or do you have to set tail rotor throttle manually?

[camlost]

@PhredWard, F-119 from B9 has gimbal, others have none. But it's very easy to add it by yourself. Besides with AJE's engine performance it's generally a bad idea to use jets for a lower stage, especially with RSS. Welcome to try, but I'm sure you'll reach the same conclusion

@MAKC, there's no shaft torque yet, hence no need for tail rotors. But they're still useful for yaw control.

[MAKC]

Ah, OK. Ten characters.

[Phredward]

@PhredWard, F-119 from B9 has gimbal, others have none. But it's very easy to add it by yourself. Besides with AJE's engine performance it's generally a bad idea to use jets for a lower stage, especially with RSS. Welcome to try, but I'm sure you'll reach the same conclusion

Thanks for the info, I'll give it a shot. So far my results, as you expect, have been less than spectacular.

In 0.23 (and without your plugin) I managed to get a Kerbal to LEO and back in a vehicle massing in at just 8.4t. I'm curious what I can do with .23.5, the updated RSS (including 180km atmosphere), and AdvancedJetEngine.

[camlost]

VTOL works nice too

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[NathanKell]

Thanks to this I have working

J58s with Mach 4 performance (if the heat shielding can take it)

J57 giving the F-100 its barely-760kts top speed

Avon 301R powering the JRC Mk III to a wopping M2+ at sea level and M2.7 at 14km (accelerating in climb, no less).

Edited May 4, 2014 by NathanKell

[camlost]

Wat? show me the J58 config pleeease

And what's that diamond shock? Don't seem to recall such an effect in HotRockets?

[MAKC]

Thanks to this I have working

Impressive aircraft. Where'd you get the cockpit for the JRC?