A new paradigm for air-breathing engines

[pincushionman]

Well, it appears they moved the center of mass of the jets forwards, which makes much of the need for this go away, at least in terms of the initial reason I suggested it. I think I'm going to look into making a proof-of-concept mod along these lines starting next week or so anyway; this may add more flexibility at the cost of complexity. If anyone is interested in being involved in that with me, PM me.

[DundraL]

Well, it appears they moved the center of mass of the jets forwards, which makes much of the need for this go away, at least in terms of the initial reason I suggested it. I think I'm going to look into making a proof-of-concept mod along these lines starting next week or so anyway; this may add more flexibility at the cost of complexity. If anyone is interested in being involved in that with me, PM me.

It definitely HASN'T!

Having the COM farther forward helps only certain craft sizes, just moves the problem to different size craft.

Try building a compact UAV with a jet engine and you wont be able to pull up. There is now a minimum size to jet aircraft.

On longer aircraft where the engines are at the back, the changes HURT, as the movement foreward of the engines mass is outweighed by their increase in weight.

We need a way to CONTROL where the COM is, not have it moved forward by some fixed amount.

So, I stand by what I said earlier in this thread, that either your or my solution to this problem would work, and that there IS a problem.

Edited May 1, 2015 by DundraL

[pincushionman]

Slooooow down, partner. "engine cores" as a solution are still going to add bulky, heavy components. If your problem is your planes aren't big enough to hold the engines, the fix isn't necessarily the engine concept, it's that we don't have good small engine parts. Which I agree with, by the way.

[DundraL]

Heavy and bulky I have no problem with. Be it new engine cores or or shifting weight from engines to intakes, what I want is to be able to control CoM instead of having it chained to a single part with placement restrictions.

As for the craft that was too small, it functions as a rover, tug, resource recon probe. when docked with my mining shipit functions as a main engine and stabilizing/control fins. Very fun to use except it currently has its rapier mounted on a stick to pot CoM in a reasonable spot.

[BmB]

Simple solution: make jet engine parts long. Nobody stores fuel inside of the engine anyway. Minimal effort, and the same result as a more complicated solution.

I'd make a part like that but I don't know how to mod KSP.

[Solarspaceprobe]

I still wish this thread was a mod...besides, as someone noted toward the start, aren't these jet engines unrealistically heavy?

[viila]

as someone noted toward the start, aren't these jet engines unrealistically heavy?

No, they were, uh, completely confused by units. For example, the Rolls-Royce Pegasus engine (used in Harrier Jump Jet) that someone linked earlier masses 1.8 tonnes, which is exactly the same mass as the J-X4 Turbo Ramjet we have now. The mass is just distributed oddly, because ours is concentrated entirely on the outlet. The P&W J58 which powers the SR-71 which is more in-line to what our advanced jet can do masses almost twice as much at 2.7 tonnes.

[NathanKell]

The mass is no longer concentrated on the outlet. Check it out ingame or examine the cfg, an offset was added.

And no, the J58 is actually much weaker than the TRJ. 150kN vs 180kN static thrust doesn't tell the whole story; our TRJ reaches a higher peak thrust and provides useful thrust at faster speeds than ([best guesses at) the J58's performance. And that's not counting the fact that the TRJ's Isp is about 10x higher.

Basically, KSP jets have about 2-3x the TWR real jets have, and about 10x the Isp. Compare that to KSP rocket engines, which have 1/8 the TWR of real ones and about the same Isp.

[pincushionman]

I still wish this thread was a mod...

I'm actually looking into the moddability of this right now - I'll post in the mod development forum when I've made some progress and put a link in this thread as well.

And yeah, I was doing some real-world comparisons and the KSP engines are some ungodly powerful sonabi-…guys.

Edited May 4, 2015 by pincushionman

[allmhuran]

The CoM of some parts is no longer related to the visual CoM, but I'm not sure that's a very good solution. It's quite confusing when building craft, and it's a bit of a "weird hack"... the CoM of an engine is a point in space somewhere forward of the engine which makes no sense *except that* it seems "necessary" to keep aircraft balanced. I think actual engine bodies being separate from nozzles is a more intuitive and elegant solution.

It would also make for some interesting new options for game mechanics. Can you add several engine bodies but still only use one exhaust? If you try to add too many engine bodies for a single exhaust, does something explode? How do intakes relate to engine bodies... do two engine bodies inline always require two intakes, or does it depend on the intake? Things like this sound like "complications" but I actually think they'd be fun to play with. Look at the amount of cool threads from pre 1.0 days as people tried to figure out the "optimum" number and type of air intakes for various flight regimes.

The main issue I can see with the idea is that it might constrain aircraft design. On real aircraft the engine is, of course, often inside of something else. If we want engine bodies to be parts, then you need a whole slew of different engine bodies to match the various shapes of craft people might want to make.

Edit:

Although... we actually kinda have "auto-clipping" parts already. Docking ports, for example, have a skirt that clips into the part to which the docking port is attached. It's only short, but it does demonstrate a precedent for this behaviour in KSP.

So a solution might be to extend the geometry of the engine nozzles so that the overall part is much longer, incorporating an actual engine body. Move the CoM of the part to a sensible position with respect to that new geometry, but have most of the part "autoclip" into the part to which the node is being attached with the exclusion of the nozzle itself, which would contain the attachment node and extend from the parent part exactly as it does now.

Edited May 4, 2015 by allmhuran

[NWM]

Some notice for it:

There is no need of extra parts, only a new flag for some parts with a center of mas translation algorithm.

now the engine looks like a short cylinder on the back, but it should be a long cylindric part, containing a short outher (output or nozzle), and a longer but smaller in diameter insider section (engine core). The insider section can be fit in some special part, like nacelles or tweaked adapters having flag to fit these engines in.

This is more simle and doesn't need extra parts....

[Slam_Jones]

I would like very much to see this suggestion become a mod. Is it possible to make it so that the engine just produce torque that can be directed thru wheels? I'm trying to make an internal combustion engine for a rover without just sticking jet engines on the back.

[Red Iron Crown]

I would like very much to see this suggestion become a mod. Is it possible to make it so that the engine just produce torque that can be directed thru wheels? I'm trying to make an internal combustion engine for a rover without just sticking jet engines on the back.

Have you tried the fuel cells that were added in 1.0?

[Slam_Jones]

Have you tried the fuel cells that were added in 1.0?

Yes, and I "made" a new one by copying and tweaking the cfg so it uses only LF and Intake Air (so it's more suitable for non-vacuum vehicles), but it's not exactly what I'm looking for. Working with it that way basically makes my rover a hybrid of sorts... instead, I want a fire-spitting (yes I posted on Firespitter mod page too), fuel-thirsty beast that uses the raw power of the LF to turn the wheels, rather than producing electricity, then using that to turn the wheels.

I'm thinking I may have to brush back up on my C# skills and make my own mod.

[thereaverofdarkness]

The electric motor seems unrealistic, and I don't even understand how it's supposed to work. I'd rather have a basic turbine engine and a later tech turbine engine optimized for high speed at high altitudes.

The RAM intake should have better functionality at high altitude and speed, and should actually get less intake air on the runway. The shock cone intakes should offer a high price tag and mass cost in exchange for a much wider range of optimum operating altitudes and speeds. These should be optimized to also have poor intake on the runway but allow planes to get air even higher and faster than RAM intakes, much like the SR-71 Blackbird's shock cone intakes.

Lastly, the exhaust ports could have an aerospike option to increase mass while also increasing efficiency, or an afterburner to increase thrust, or just a basic exhaust port that's cheap and lightweight and low-tech.

But I LOVE this suggestion! Not only is it difficult to balance the lift on planes, they jar strongly with my experience as a turbojet engine mechanic.

[pincushionman]

I would like very much to see this suggestion become a mod. Is it possible to make it so that the engine just produce torque that can be directed thru wheels? I'm trying to make an internal combustion engine for a rover without just sticking jet engines on the back.

Assuming I get the concept to work, you could use EnginePower to run any "output." I mentioned jet nozzles and propellers, but there's no reason that wheels couldn't take that as their input resource rather than ElectricCharge. Or electrical generators. Or winches. Or resource drills…

Experiments are ongoing to get the basic concept working first, though. It's not as simpleas defining a resource and using it in the parts configs. I'm going to need to make new modules to handle the conversions.

Edited May 5, 2015 by pincushionman

[Slam_Jones]

Assuming I get the concept to work, you could use EnginePower to run any "output." I mentioned jet nozzles and propellers, but there's no reason that wheels couldn't take that as their input resource rather than ElectricCharge. Or electrical generators. Or winches. Or resource drills…

Experiments are ongoing to get the basic concept working first, though. It's not as simpleas defining a resource and using it in the parts configs. I'm going to need to make new modules to handle the conversions.

Right on, good to know. I'm going through some theory right now myself, working on it from a slightly different angle. My modding experience is limited to some C#/Unity knowledge (which I'm brushing up on) and some cfg file editing; but really not much beyond that.

The ideas I'm going through are a little more complicated than just producing EnginePower, but they're not quite ready for show-and-tell yet.