Any interest in a 'canned air' mod so jets work in vacuum?

[PooPooTron]

So my basic idea with this is that 'IntakeAir' becomes a portable resource just like liquid fuel or oxidizer so you can use it outside the atmosphere or just at super high altitudes. All I plan to do is edit a pre-existing part. Would anyone else be interested in this? It would obviously be pretty OP since the jet engines ISP are pretty crazy, but maybe I could make the part heavy or something...

[Greys]

Jets have two curves; one determines their ISP relative to atmospheric density; one determines their thrust relative to surface velocity.

In orbit jets produce 0kN of thrust at almost infinite efficiency.

Regardless of if you have intake air to run them on, Jets don't work in orbit. (theoretically they would work while landed on the mun, but the efficiency thing will be problematic)

[Whirligig Girl]

I tried this once for testing purposes. It doesn't work too well. The jets don't really like running for more than two seconds in space.

[nli2work]

sure, but standard ratio is LF:IntakeAir ratio is around 1:15; you'd need a lot of IntakeAir... at that point, it's practically Oxidizer (liquid oxygen). then it's not very different than increasing the ISP for a standard rocket engine

[kerbiloid]

There was already such mod  several KSP releases ago.

And if you have a look at KSP/GameData/Squad/PartsEngine/rapierEngine/rapierEngine.cfg, you can see that Rapier engine has two module definitions  every with its on curve and propellant.

So, I guess if you replace "Oxidizer" with any another resource, you can use even a Water, not only IntakeAir.

But this way you just reinvent Rapier with IntakeAir instead Oxidizer, which probably makes too little sense.

[RainDreamer]

Well. If you are compressing the intake air to the point liquidfication and take it into space, it is no different than just hauling oxidizer, the difference is that you gain weight while flying, not shedding it away like usual.

And actually in stock game, I believe if you close all the intakes before you go outside atmosphere, you keep all the air inside the intake. Though you will probably only burn for a very, very short time. Barely makes a blip, since there would be so little air left.

[Kerbart]

Isn't this why we have rocket engines in the first place?

[nli2work]

I suppose something more interesting is a converter to extract oxygen from IntakeAir into Oxidizer. so a mixed mode craft can dive into the atmosphere to replenish oxidizer, assuming some excess of liquid fuel

[Goozeman]

The more interesting (and realistic) vision of something like this would be a ducted fan driven off of rocket propellants. Jet engines don't work on extraterrestrial bodies even if they have atmospheres (with the possible exception of Laythe) because there is no Oxygen. One could conceivably make what is a turbofan engine driven by fuel/ox mix instead of fuel/intake air mix. It would be far more efficient at low speeds than a rocket. Such a propulsion method has been proposed for use on a Mars airplane.

[Van Disaster]

I suppose something more interesting is a converter to extract oxygen from IntakeAir into Oxidizer. so a mixed mode craft can dive into the atmosphere to replenish oxidizer, assuming some excess of liquid fuel

I did an easy MM config to take IntakeAtm ( common resource definition for neutral atmosphere ) and add Oxidizer to produce IntakeAir in an existing engine intake, so - in my case your piston prop engines - could work on a planet with an atmosphere ( I didn't try one with flow rates suitable for jets, I think that'd be quite large and a bit boring ) via a Karbonite converter, that was really useful, and closed cycle piston engines are pretty old tech. Made a request for always-on converters, so that might be a practical addition to something in future.

Engines in methane-rich atmosphere might be interesting, you'd possibly just have to take the oxidizer with you.

-

Using jets in space is not a thing. You have a tube with oxidizer and some liquid combustible with some rotors that don't have any mass to work with, so basically you've got a bad rocket with some useless metal bits in the way to burn up - might as well use a rocket. There's been discussion in the past about extracting Oxidizer from air and the likely costs, probably worth a search on that.

[Guest]

Liquefaction of air in bulk quantities is an energy-intensive process, not mentioning you have to carry big factory with you.

[camlost]

Too much magic, too much

[MeateaW]

The problem with Jet engines in space:

The fuel isn't being used as the mass to be expelled out the back, it is used as the chemical energy to spin the turbine. The turbine then grabs air from in front of the engine, and pushes it out the back. (Sure, it uses some of this air as part of the burning process - the oxidizer) but it is the actual air itself forming the reaction mass (the thing you "push away" to then gain speed).

In space, there is no reaction-mass for a turbine to use. In addition to no oxidizer. The reason rockets are less efficient is due to the Rocket-fuel+Oxidizer mix must also constitute your reaction mass.

So, there is little physical reason for the jet engines to work in space (well, except as a really weird rocket engine - RAPIER?) But, As others have said, the use of non-oxygen rich atmospheres as reaction mass (combined with some oxidizer) actually sounds really interesting. I'd say a high-tech level Jet Engine that has a "closed cycle-Jet" mode (as opposed to closed-cycle rocket mode), which injects fuel and oxidizer, could operate much more efficiently in inert atmospheres, it would be less "efficient" than in oxygen-rich atmospheres (since it would need oxy in addition to your liquid fuel), but you could theoretically use the atmosphere as your reaction mass to massively reduce fuel requirements.

[RainDreamer]

I think the RAPIER is based on experimental tech for hybrid air breathing/closed cycle rocket engine, called SABRE.

[Las-pen]

I think I saw Oxidizer to IntakeAir converter mod somewhere sometime. Pretty sure it is outdated.

[Fireheart318]

KSP makes jets work ONLY in atmosphere, they can't push off vacuums for this and some other reasons. I'm not entirely sure why but they don't. I made a mod that let me change engine modes on jets to use oxidizer (mainly for Even, Dunian, Joolian and high altitude Kerbal flight) and put one in orbit. Didn't work

[Dire_Squid]

Ya know, I actually HAVE thought of Exo-planetary "Air" intakes... MIND YOU, this is more science fiction than science fact (but also remember that Jules Verne DID predict submarines, jet planes, and rockets LONG before they were invented, and he was a fiction writer.  ).

My thoughts, however, either could have partial air or, logically, use no "air" at all, but instead find ways to utilize the atmospheres, beit finding ways to burn atmosphere at the molecular level via convection-based intake (thoughts for Eve atmosphere usage, being thick and dense, being heated and 'boiled' to something thinner and possibly more manageable), or using some means to ionize the atmosphere that enters the intake (Duna's thin atmosphere). So yes, to repeat, this IS more science fiction than fact, but the parts have some means of ability balance, in-game. The FIRST being: "You are unable to use them in Kerbin-like oxygenated atmopsheres... or in space"; that's right, they won't work on Kerbin (or Laythe, for that matter) or in space, which adds to the challenge of getting them to atmosphere planets. The second... I WANT to say that, since the technology isn't perfect, that I want to imagine that these molecular-converting intakes create a LOT of heat, and are prone to overheating and exploding if used recklessly, for long bouts of time. A third being that they aren't as efficient as traditional oxygen-based intakes and engines (complimenting the whole heating up thing); probably chewing through fuel faster than typical Jet engines and intakes.

Mind you, this is a VERY LOOSE idea I have, and it's more science fiction than science fact (and most likely, realistically, these ideas are mere "fanciful quackery")... but I am VERY willing to go over ways that my ideas could be tweaked to be more believable (if at all: Like I said, I know my idea is glorified sci-fi). If you feel my ideas are more impractical then a "Solar-powered Ion-glider", hey, you're more than entitled to spit out the facts. My idea is not totally grounded in fact... but with the right tweaks could make it more believable (for "quackery").

Edited May 8, 2016 by Dire_Squid