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

[Tellion]

After struggling for quite some time with making an SSTO in 64k with AJE, I finally did it today! Even delivers a kerbal into orbit, and what a nice twr it has. So proud...

Now, seriously, how do people do this? I read here and there that some gifted individuals succeeded, but have hardly found any screenshots that would help identify issues with craft design. Every once in a while I will try it again, only to give it up frustrated a few days later, so I seem to be doing something very wrong...

I was mostly using B9/stock mk3 parts lately and noticed that many of them have dry mass fractions of ~60% when filled with LH2, so no wonder there - however RealFuels went over those, so I am not quite so sure about it. Working with PP yields much friendlier mass fractions, but disallows using DRE alongside it, so I would love to avoid that as well. Coming to the point, I would love to see some screenshots of successful (horizontal takeoff) SSTOs in 64K and above to c̶o̶p̶y̶ ̶s̶h̶a̶m̶e̶l̶e̶s̶s̶l̶y̶ humbly learn from.

Oh, and great mod by the way, some things just can not be said often enough.

[FreeThinker]

After struggling for quite some time with making an SSTO in 64k with AJE, I finally did it today! Even delivers a kerbal into orbit, and what a nice twr it has. So proud...

http://i.imgur.com/bB17fKh.jpg

Now, seriously, how do people do this? I read here and there that some gifted individuals succeeded, but have hardly found any screenshots that would help identify issues with craft design. Every once in a while I will try it again, only to give it up frustrated a few days later, so I seem to be doing something very wrong...

I was mostly using B9/stock mk3 parts lately and noticed that many of them have dry mass fractions of ~60% when filled with LH2, so no wonder there - however RealFuels went over those, so I am not quite so sure about it. Working with PP yields much friendlier mass fractions, but disallows using DRE alongside it, so I would love to avoid that as well. Coming to the point, I would love to see some screenshots of successful (horizontal takeoff) SSTOs in 64K and above to c̶o̶p̶y̶ ̶s̶h̶a̶m̶e̶l̶e̶s̶s̶l̶y̶ humbly learn from.

Oh, and great mod by the way, some things just can not be said often enough.

With 64k, you need about 7500m/sec delta V to get into orbit. Your not going to achieve that in a SSTO with chemical jet engine/rockets. Your best bet is using more efficient and therefore more powerfull propulsion engines.

I'm currently trying to make KSPI more friendly for SSTO. The Idea is it allows you to put a reactor somewhere in the center of the SSTO which should give you the power to efficently get into an orbit around 6.4x sized Kerbin.

Edited March 5, 2015 by FreeThinker

[Northstar1989]

I concur with FreeThinker. You're not going to have an easy time building a HTHL (Horizontal Takeoff, Horizontal Landing- i.e. a spaceplane) SSTO in RSS 64K with conventional technology. In fact, without at least using RealFuels, FAR, and SABRE (not RAPIER- which runs on Kerosene instead of Hydrogen) engines you don't stand a chance. With them, you could build something like Skylon- but you should still only expect a 2-3% mass-fraction... (so a spaceplane massing at least 500 tons or so on the Runway just to get a 2-ton Mk2 cockpit into orbit...) Without Realism Overhaul scaling-up, you can pretty much forget about something that big actually getting off the runway though...

Even with KSP-Interstellar, if you stick to near-future tech (Molten Salt and Particle Bed Reactors, and Microwave Beamed Power) you're going to have an extremely hard time. Your best bet is probably to build something that relies on Microwave Thermal Turbojets to get to about 27 km and Mach 3-4 (similar to Skylon but a bit higher relative to atmospheric height) and then switches over to Microwave Thermal Rockets to make it the rest of the way to orbit... Even so, while you may double your maximum ISP and eliminate the need for fuel until you switch to rocekts- and thus more than double your mass-fraction, expect a spaceplane of at least 200 tons with LH₂ alone (which with the low fuel-density of Hydrogen means an enormous spaceplane- even larger in volume than the 500-ton behemoth discussed earlier) and easily 400 tons (but with higher fuel-density) for a combination of LH₂, HydroLOX, MethLOX, and pure Methane... (manageable with RealFuels as it's really only 3 resources you need to manage here- Hydrogen, Oxygen, and Methane...)

Regards,

Northstar

[Northstar1989]

Yeah, now that I look at it again, I think the RAPIER's (and SABRE's) rocket thrust could probably use a buff - in AJE, you're typically lower in the atmosphere when you switch to rocket mode, meaning much more drag to overcome in order to get into orbit, so the rocket thrust should reflect that reality. According to REL's data, the real SABRE's rocket thrust will be something like 2.5x it's static air-breathing thrust, so maybe that's a good starting point.

Based on the implementation of the RAPIER engine in RealFuels (Kerosene-airbreathing and Kero/LOX rocket) I'm not sure it is actually meant to be a SABRE analog... And since many players using AJE are probably also using RealFuels...

Now, B9 Aerospace has an engine which is actually called SABRE, and even looks like the real SABRE. It even uses Hydrogen and HydroLOX in RealFuels. What about balancing this to be the SABRE engine, and leaving the RAPIER as a lower-ISP Kerosene-burning alternative? (which couldn't possibly make orbit on a HTHL SSTO in RSS, of course- due to the much lower ISP of Kero/LOX than HydroLOX, and is mostly limited to stock-sized systems for spaceplane use)

Also, regardless of what RAPIER is meant to represent, it really should have higher thrust in rocket-mode than in air-breathing mode. Anything else just seems silly to me from a realism-perspective: though of course it's not my mod (in fact, I don't even use AJE in my saves), and you're free to do whatever you want with it. Your users will love you either way.

Regards,

Northstar

[Elbe]

Hello KSP-Community,

I tried this mod together with Davons Throttle Control mod from PrivateFlip and noticed that they dont work together (or i missed something, but DTC is quiet simple so i dont think so). I build an airplane and tried to start with two normal jet engines, gain a bit of altitude and then switch to the hypersonic ramjet engine. But i cant control the thrust of these engines with DTC. I know i can switch them on and off with control groups but i think it would be nice if i could slowly throttle the normal engines down and the ramjet up.

[kcs123]

Haven't time to recreate planes with AJE for v0.90, but I in 0.25 they performed well. Those I have made for 0.90 are done with heavy payload, so crafts should perform well with AJE with more reasonable payload.

I'm also using B9, so if you are looking for examples, check links in my signature.

For SSTO with AJE is just to put more fuel on plane, find sweet spot how many air intakes you need that provide needed air without much drag and finding optimal ascent path.

[camlost]

Hello KSP-Community,

I tried this mod together with Davons Throttle Control mod from PrivateFlip and noticed that they dont work together (or i missed something, but DTC is quiet simple so i dont think so). I build an airplane and tried to start with two normal jet engines, gain a bit of altitude and then switch to the hypersonic ramjet engine. But i cant control the thrust of these engines with DTC. I know i can switch them on and off with control groups but i think it would be nice if i could slowly throttle the normal engines down and the ramjet up.

If DTC sets engine thrust dynamically like AJE, there's the conflict. Try another mod that sets thrust limit instead of max thrust.

[blowfish]

So after some fiddling with the equations I think I've created a working thermodynamic model of the SABRE, including the helium loop and the ramjet bypass. Compared to the existing model, thrust seems to grow a bit more speed and efficiency is higher at low mach numbers. Some aspects don't quite agree with REL's data but that data is inconsistent anyway. Integrating it into AJE would take some work, since it would require a new module and various other changes, but it should be possible in the long run

[Mad Rocket Scientist]

What do all those sliders in the right click menu of piston engines mean?

Love this mod, by the way, adds so much more strategy to building planes!

[NathanKell]

Don't touch Heat Mult or the *Tweaks, they're for engine tuning. As for the others:

• Prop RPM should be self-explanatory; engine RPM will be this divided by the gear ratio.
  
• Prop Pitch is the pitch, in degrees, beyond feathered. I suggest looking up "constant speed propeller" for more information, basically the governor varies the incidence of the blades to achieve a set RPM. Will be constant for fixed-pitch propellers.
  
• Prop Thrust should be self-explanatory.
  
• Manifold Pressure (Manifold Absolute Pressure, MAP) is the pressure, in inches of Mercury, in the manifold of the engine. Most engines are supercharged and thus MAP will be > 29.92. When it starts to drop below its constant level, your supercharger (or turbocharger) is no longer providing enough boost; the highest altitude where it can is known as "critical altitude" (US) or "full throttle height" (UK). If the engine has a two-stage supercharger (or a turbosupercharger), however (and that will be noted in the description), there will be two of these altitudes. For best speed, you want to fly at the higher of the two critical altitudes (or one if only one); note that some engines take advantage of ram air and thus flying faster (and increasing ram air intake) will yield a higher base pressure and thus a higher critical altitude.
  
• Fuel flow is self-explanatory, it's in liters/sec (if using Real Fuels).
  
• Charge Air Temperature is the temperature of the 'charge', what the turbo/supercharger passes on to the engine to go in the manifold.
  
• Exhaust Thrust is the additional thrust provided by ejector exhausts. Only some engines feature ejector exhausts, and of varying efficiency.
  
• Meredith Effect is the additional thrust provided by careful radiator design. Only some aircraft (in AJE, only some engines) take advantage of the Meredith Effect, and at varying strengths.
  
• Brake Horsepower is the horsepower your engine is currently delivering to the propeller (any supercharger losses have already been factored in).
  
• Boost is your boost lever, it controls the supercharger: When it is at 1.0, you're running your engine at maximum possible boost, and any additional charge pressure beyond the max MAP will be vented; as you lower this, the (turbo/)supercharger provides less and less boost, and at 0.0 any boost beyond ambient pressure is vented.
  
• RPM Lever is your RPM lever (for constant speed propellers); at 0.0 your engine runs at its minimum RPM, and at 1.0 it runs at its maximum RPM (the pitch of the propeller is varied to ensure the desired RPM is hit). Will not work when fixed-pitch propellers are used.
  
• Mixture is your mixture lever, it controls how rich or lean the mixture is. It comes "pre-loaded" at the mixture that delivers maximum power, but you can lean it for higher efficiency or (especially when taking off) rich it for lower heat.

The tweaks (which you shouldn't touch):

• Heat Mult is a multiplier to the heat the engine produces.
  
• CtTweak is a multiplier to the propeller's thrust coefficient.
  
• CpTweak is a multiplier to the propeller's power coefficient.
  
• VolETweak is a multiplier to the engine's volumetric efficiency (a multiplier to how much air and be pumped).
  
• MachPowTweak is an exponent for the compressibility effects a propeller starts to encounter when its tips break into the high transonic or go supersonic.

camlost, fuel flow reminds me: All piston engines should be using AvGas, not kerosene. It's what it's there for.

Edited March 23, 2015 by NathanKell

[Mad Rocket Scientist]

Wow,

Thanks a lot! that's really useful, I can't wait to try some piston engines with these adjustments!

[blowfish]

Hey camlost, should static thrust be calculated with an ideal TPR=1, or with more realistic values?

[Mecripp]

Anyone have a fix for this with the Skylon mod http://forum.kerbalspaceprogram.com/threads/49756-WIP-R-E-L-Skylon-C2-Alpha-Released-FAR-config-broken-%2808-Dec-2014%29 has it changes one of the fuels the skylon uses ?

[Rothank]

Encountered a strange problem with KAX prop engines. I recently updated my mods and now said engines have no thrust curve, they just throttle like if they weren't modded. I tried reverting back to older version of AJE, but it didn't work. Other mods that I updated are RO, RP-0, FAR. Could one of them be causing this?

This engine really shouldn't have that much power, should it? It used to go to <30kN max...

EDIT: Jet engines work fine, it's only prop engine issue. Downloading additional prop engine pack (Real Airplanes) to check if it's global or KAX related.

EDIT2: All Real Airplanes engines produce fixed 5kN of thrust, so it's not only KAX propellers, all my prop engines are bugged and behave like stock rocket engines. Any ideas what's causing this?

Edited April 5, 2015 by Rothank

[blowfish]

Anyone have a fix for this with the Skylon mod http://forum.kerbalspaceprogram.com/threads/49756-WIP-R-E-L-Skylon-C2-Alpha-Released-FAR-config-broken-%2808-Dec-2014%29 has it changes one of the fuels the skylon uses ?

There's a config node in AJE/zFinal/zzWildcards.cfg:

@PART[*]:NEEDS[!RealFuels]:FINAL
{
	@MODULE[ModuleEngin*],*
	{
		@PROPELLANT[LiquidOxygen]
		{
			@name = Oxidizer
		}
		@PROPELLANT[LiquidH2]
		{
			@name = LiquidFuel
		}
		@PROPELLANT[Kerosene]
		{
			@name = LiquidFuel
		}
	}
}

Which is causing the problem. I don't _think_ anything will mess up if you remove it but keep a backup just in case.

[Mecripp]

Thanks blowfish that helps

[CaptainKipard]

Hello camlost. Is there anything you or I can do to definitively remove this conflict for good? Could you maybe check in your MM config whether an engine uses stock resources and only apply the patch if it does?

[blowfish]

I suspect that particular config node will cause conflicts with NearFuture too so it might be a good idea to change it.

[camlost]

Hello camlost. Is there anything you or I can do to definitively remove this conflict for good? Could you maybe check in your MM config whether an engine uses stock resources and only apply the patch if it does?

What is the concept of Skylon mod? Does it use custom fuel types but requiring RF?

[NathanKell]

camlost: I screwed up with my PR, thought I sent it in a week ago, but it's only now gone through (thanks pjf!) -- that has some compatibility fixes for interaction with Realism Overhaul.

Also, AJE needs a new build for the prop engines to work with the new FAR (the references have to be updated--AJE expects 14.6 and FAR is 14.7, that gets updated automatically on build if you have the new FAR dll referenced...)

[blowfish]

What is the concept of Skylon mod? Does it use custom fuel types but requiring RF?

It uses CRP LiquidHyrdogen and LiquidOxygen.

[Wolf_rt]

So i have been trying to make an F-104 with the J79 turbojet. I think there is something wrong with the thrust i'm getting.

I wasnt actually aware that i had AJE installed... CKAN must have helped me out there...lol, i origionaly asked this question in the B9 thread, thinking it was an issue with that.

I am using FAR and B9.

the model i have made is the correct weight (6000kg dry) and the J79 supposedly supply's the correct amount of thrust (79KN) However it just wont go fast enough, or climb...

On takeoff thrust reaches 62Kn

At very low altitude flying level, thrust reaches almost 70KN at about Mach 0.45

As soon as i initiate a gentle climb at 10deg or less, thrust rapidly falls of (along with airspeed)

You can see here, at a rate of climb of under 15m/s thrust has dropped to 40KN by 3000m

At this point i have to level out, or the thrust will continue to decrease to around 20KN, at which point i fall out of the sky.

Even after leveling out though, the thrust doesn't recover very fast, and i cant get airspeed above Mach 0.5... the plane eventualy runs out of fuel without thrust ever going over 50KN

Anyone know what is going on here? The plane should be able to hit Mach 1 with only 55KN of thrust. I thought these engines were balanced with FAR & realistic performance specifically in mind?

Is this a bug or a conflict? or some other issue?

EDIT: So i have made some progress by reducing the drag of the craft. in the photos above the cd was 0.058 now it is a 0.02 very close to the actual F-104 at 0.017

This allows the aircraft to get up to 100KN of thrust at sea level, which quickly pushes it to Mach 0.95, however as soon as i initiate a climb, the thrust drops massively, and i'm still stuck at the 3000m ceiling. where thrust drops to 40KN, and i either dive to regain thrust, or climb further and thrust drops below 20KN.

[ThorBeorn]

Wolf_rt: While the J79 may underperform in AJE I suggest building a plane with the same TWR and the same type of wing without the clipped parts in the fuselage, just as a test. FAR can not yet detect clipped parts and applies too much drag to them (as if they were out in the open). Also, I don't know about the F-104, but some of those early supersonic planes had to dive a bit to pass through the high drag transonic region before they could climb/level out again.

Edited April 12, 2015 by ThorBeorn
spelling

[Wolf_rt]

ThorBeorn, there is defiantly something going wrong... i uninstalled AJE and B9 and i can still only get 50% thrust from the stock turbojet.

There was an issue with drag as you mentioned, but i fixed it and the cd is now identical to the real plane, see edit in last post.

I am installing a fresh copy with only FAR and procedural tanks, to asses the stock turbojet. I will then add AJE, to see if it is some conflict.

Edited April 12, 2015 by Wolf_rt

[ThorBeorn]

Wolf_rt: What exactly is the problem you are having? You need to be very specific. 50% thrust when? During flight or on the ground standing still? Using what mods? AJE changes jet engines behaviour completely.

FAR without AJE only changes the thrustcurve of the basic jet engine (squad), making it produce less power at speed. Its maxthrust remains the same standing still. The turbofan on the other hand gets its power reduced by ~50% at a slower thrustcurve.

If that is what bothers you, don't use FAR, or edit the maxthrust and thrustvurve yourself in FerramAerospaceResearch.cfg, or make a MM patch. That discussion should take place in the FAR thread though.

Edit: Note that there is not likely any conflict going on in your install. Everything seems to be working as intended.

Edited April 12, 2015 by ThorBeorn