Jet engine documentation

[SiliconPyro]

I am working on a jet engine and I'm having trouble finding documentation for setting up the .cfg file. I'm talking about settings specific to to jet engines, I've made them for other parts. I'm sure I can get it sorted myself with a little experimentation, but I'll take any help I can get.

[nli2work]

stock jet engines use standard ModuleEngine or ModuleEngineFX. for engine performance behaviour they are the same. EngineFX has more robust FX capabilities.

three section that matter for jet engines are

This puts a lag on engine's actual thrust and your throttle setting. higher the value the quicker the response. I believe the scale is 0~1. 1 is instant response. same as setting unseEngineResponseTime = false.

	useEngineResponseTime = True
	engineAccelerationSpeed = 0.2
	engineDecelerationSpeed = 0.35

This is common to all ModuleEngine and ModuleEngineFX; determines ISP based on atmospheric pressure. 1st value is Atmosphere pressure; 2nd value is ISP. separated by space.

0 is vacuum; 1 is 1 atm, sea-level on Kerbin. planets with lower or higher atmosphere pressure will affect the engine ISP differently than on Kerbin, still based on this curve you define. You can set as many keys as you like, KSP generates a graph based on the keys you set. generally 3 to 4 is enough.

atmosphereCurve
 	{
		key = 0 1200
		key = 0.3 2500
		key = 1 800
 	}

works similar to AtmosphereCurve. thrust as dependent on velocity. 1st value is velocity, 2nd vale is thrust multiplier. thrust multiplier can be any value; generally between 0 to 1.2.

useVelocityCurve = True
velocityCurve
{
	key = 0 0.5 0 0
	key = 1000 1 0 0
	key = 2000 0.5 0 0
	key = 2400 0 0 0
}

Edited August 14, 2014 by nli2work

[SiliconPyro]

Man, once again you show up worth exactly what I need. Thank you again.

Is this documented anywhere publicly, in a wiki or something?

[nli2work]

Man, once again you show up worth exactly what I need. Thank you again.

Is this documented anywhere publicly, in a wiki or something?

it's documented in the forums. but burried pretty far back and in different threads.. sometimes it's easier just to answer it than to dig up the old links.

there's a mod called Advanced Jet Engines that is designed to give much more realistic performance characteristics for jet engines. but I have no idea how to use it.

[Justin Kerbice]

There in a doc on air breathing engines in general/tutorials (a detailled look at jet engines).

FYI, 0 of atmo curve is not strictly speaking "vacuum" (atmos. density/pressure very low), maybe a more accurate description would be "no oxygen" (Duna ground level = vacuum with the standard, Kerbin-oriented, definition)

[SiliconPyro]

I wish we had a better modding wiki.

I'm trying to do as much as possible without relying on plugins, but thanks. I'll look into that one if I'm not satisfied with what I can do

[nli2work]

IIRC NathanKell mentioned for atmosphere curve 1 = atmospheric pressure at Kerbin sea level; roughly 101 Pascal. 0 is outside Kerbin atmosphere, above 69km. This would mean Duna sea level is about 0.4 on the atmospheric curve. An engine would have higher ISP at sea level on Duna than on Kerbin.

Oxygen requirement is controlled by this block in ModuleEngine; in this case, IntakeAir consumption is 15x LF consumption. if you remove this propellant requirement from the jet engine config; you would have a jet engine that works in vacuum and does not require oxidizer. if you remove all propellant blocks, you'd have a magic engine that runs forever.

PROPELLANT
	{
		name = IntakeAir
		ratio = 15
	}

There is a relevant tag in ModuleIntake checkForOxygen = true; I think this restricts jet engines to run on planets with oxygen rich atmosphere, Kerbin and Laythe; if you set it false, the engine will probably run in any atmosphere. I haven't tested so can't confirm 100%.

MODULE
{
  name = ModuleResourceIntake
  resourceName = IntakeAir
  checkForOxygen = true
  area = 0.01
  intakeSpeed = 10
  intakeTransformName = Intake  
}

The compilation of modding info sticky thread is still good source of information, even though it's somewhat out of date. Much of it is still applicable. I recommend bookmarking it and look there first for basic information.

Edited August 14, 2014 by nli2work

[ABZB]

if you remove all propellant blocks, you'd have a magic engine that runs forever.

That is false, I believe - unless you have at least one resource that has mass (so not electriccharge) the engine will not function. An engine with only electriccharge as a fuel will list a fuel consumption of infinity/sec and will provide 0 thrust when launched.

There is a relevant tag in ModuleIntake checkForOxygen = true; I think this restricts jet engines to run on planets with oxygen rich atmosphere, Kerbin and Laythe; if you set it false, the engine will probably run in any atmosphere. I haven't tested so can't confirm 100%.

MODULE
{
  name = ModuleResourceIntake
  resourceName = IntakeAir
  checkForOxygen = true
  area = 0.01
  intakeSpeed = 10
  intakeTransformName = Intake  
}

I can confirm that this is true. [i did this for the sake of some electric engines [propellers] that logically should function on eve and Jool (and are more convenient for the viability of return trips)]

[nli2work]

That is false, I believe - unless you have at least one resource that has mass (so not electriccharge) the engine will not function. An engine with only electriccharge as a fuel will list a fuel consumption of infinity/sec and will provide 0 thrust when launched.

Interesting. To the test pad!

[Justin Kerbice]

Interesting. To the test pad!

And also to ABZB: I test with a very low-density resource (0.00000001 and even lower) with quite "high" (ie: non human technology ) Isp, the flow is high too and the best way is to add a generator which feed the engine while running.

You can try the solaronite powered engine I've made with my flying saucer, I put a fair generator on it, so only thurst <= 11% can work, higher and the engine runs out of propellant.

But on all I only try low thrust (20-50 kN), but I think I've made a 200 kN but 4 of them on a light probe was far too crazy (it can reach 2000 m/s in a short time from Kerbin ground and go over 10000 m/s then there is no place to go anyway).