Stock nuclear air-breathing engines

[goduranus]

Hell, 0.24 messed up visual effects of Interstellar's thermojet engines.

But in any case, nuclear jet engine should be a part of the stock game, as they are real-world technologies that would aid the exploration of inert atmospheres. In terms of technical feasibility, nuclear jets(real world counterparts prototyped and successfully tested but never put into operation) would be no less practical than the LV-N.

While nuclear jets would probably have ISP in the hundreds of thousands, their awesome power could be counterbalanced by weight, high cost, and possibly a reputation hit and credits costs if they crash on Kerbin, which I also suggest should be the case for all nuclear parts.

Real world examples of nuclear jets:

http://en.wikipedia.org/wiki/WS-125 Prototype engines built in 1956

http://en.wikipedia.org/wiki/Project_Pluto Prototype engines built in 1961

In fact, given the popularity of KSP, I suspect that such an implementation of nuclear jets for the exploration of Eve might prompt the real world to propose using nuclear jets for extended exploration of Venus. Which would be one step forward for science.

Edited August 4, 2014 by goduranus

[goduranus]

another nuke-jet picture to add some flavor

Just imagine if all the payload were SCIENCE!

Edited August 4, 2014 by goduranus

[JMBuilder]

Yes! This is very much needed for planets like Duna and Eve.

[CaptRobau]

I've looked at the wiki article for these kinds of aircraft, but I don't see it mentioning not needing air for combustion. Instead it seems to use the nuclear reactor to heat up the air enough to get thrust, instead of burning jet fuel.

[M3tal_Warrior]

I've looked at the wiki article for these kinds of aircraft, but I don't see it mentioning not needing air for combustion.

Quite correct. The fuel in normal jet engines is used to heat up the incoming air (requiring oxygen to burn the fuel), producing pressure that's ejected through the nozzle (despite contrary believe it adds only little to the amount of molecules, where 1 mol is at normal pressure/temperature equal to 22.4 litres - if it wasn't for the heat it wouldn't work). There it propels a turbine which in return shoves more air into the combustion chamber, creating a self-sustaining air flow and thus thrust.

Nuclear engines replace liquid fuel (kerosene) by a thermonuclear reactor core - it heats the air (to even higher temperatures than normal jet fuel, where higher temperatures and pressures propel at some point the creation of bigger molecules to reduce the amount and thus the pressure, diminishing the effectivity), the rest is the same as above. It would work in every atmospheric environment, even with noble gases (Helium would be best I guess, since there is no such thing as combination reaction even for insane temperatures/pressures). I'm not entirely sure if it would work in fluids, but if you'd adjust the turbines or use pumps for injection I reckon this would even work there - injecting small amounts of liquid in the core, heating that until it vaporizes and let it shoot out of a back nozzle. Only drawback would be the intense density and thus resistance/drag of a fluid compared to gases. So I guess you wouldn't be very fast, and look like having a serious flatulence problem.

Edited August 5, 2014 by M3tal_Warrior

[Laie]

I've looked at the wiki article for these kinds of aircraft, but I don't see it mentioning not needing air for combustion. Instead it seems to use the nuclear reactor to heat up the air enough to get thrust, instead of burning jet fuel.

This kind of engine doesn't need to combust anything. It needs some gas to work with, though. In principle it could function in any sufficiently dense atmosphere, be it oxidizing or not.

[RuBisCO]

Would certainly be nice on Eve. Is there a nuclear air-breathing engine mod?

[UberFuber]

In this case, won't it be a bit OP given the current design for nuclear engine (aka, infinite nuclear fuel)?

For an air-breathing engine, that means 0 need for any fuel (just fly into atmosphere, boom, free thrust).

[Stargate525]

In this case, won't it be a bit OP given the current design for nuclear engine (aka, infinite nuclear fuel)?

For an air-breathing engine, that means 0 need for any fuel (just fly into atmosphere, boom, free thrust).

Yes, but it's a ramjet. That means it can't accelerate you from zero, and its efficiency decreases with speed. It also calls for a nuclear reactor, which is very heavy. And since it is indeed a turbojet it doesn't produce massive amounts of thrust.

So the pros:

-near-infinite fuel in atmospheres

cons:

-weak thrust

-very heavy

-very expensive

-useful only at speed

[Clockwork_werewolf]

I can actually see a place for this in the tech tree. If the engine is given a thrust to weight of less than 1 then you have to build a plane rather than a rocket making it less over powered. It's cost must also be more than the cost of a turbo jet plus a lot of fuel. I'm not sure how to enforce the speed requirement without a module. lugging a heavy engine to Duna or Eve (say 4 tons) would be enough of a cost in fuel to make it balanced by the infinite fuel. Could be an interesting end tech air engine, and I usually think things like this are overpowered.

[UberFuber]

I can actually see a place for this in the tech tree. If the engine is given a thrust to weight of less than 1 then you have to build a plane rather than a rocket making it less over powered. It's cost must also be more than the cost of a turbo jet plus a lot of fuel. I'm not sure how to enforce the speed requirement without a module. lugging a heavy engine to Duna or Eve (say 4 tons) would be enough of a cost in fuel to make it balanced by the infinite fuel. Could be an interesting end tech air engine, and I usually think things like this are overpowered.

The "minimum speed" could be implemented as the nuclear engine having horrific thrust at low velocity that only ramps up to some reasonable thrust level at high enough speed. I think you can implement this by using the velocityCurve property.

Note, I'm taking the Turbo Jet number and tweaking it.

velocityCurve
	{
		key = 0 0.01 0 0
                key = 200 0.1 0 0
		key = 1000 1 0 0
		key = 2000 0.5 0 0
		key = 2400 0 0 0
	}

Note, I don't know whether the engine can handle a thrust ratio of <0.1.

In the above, the nuke engine will have the following thrust profile.

From standing still, the engine only generates 1% of its maximum thrust (if you want to be a bit sadistic, you can put that at 0).

At 200 m/s, the engine will generate 10% of its max thrust.

At 1000 m/s the engine will generate 100% of its max thrust.

Beyond that, the engine once against start to lose thrust until 2400 m/s (0% thrust).

Also in theory, nuclear engine don't need "intake air", since it doesn't need to combust anything to generate thrust (it just heats up a working fluid/gas). Therefore it doesn't need a minimum "Intake Air" amount to operate.

So that may require a new module written for it, since current setting for atmosphereCurve deals with Isp, not thrust.

Nuke engine, it could, in theory, consume very tiny amount of Intake such that a single Intake can supply all its need until it reach vacuum. The thrust curve can be adjusted against the atmosphere, with 0 thrust in vacuum.

Edited August 5, 2014 by UberFuber

[Laie]

Yes, but it's a ramjet. That means it can't accelerate you from zero, and its efficiency decreases with speed. It also calls for a nuclear reactor, which is very heavy. And since it is indeed a turbojet it doesn't produce massive amounts of thrust.

That cruise missile / unmanned bomber pictured in the OP was supposed to be launched with boosters to bring it up to speed. Then I could have cruised for weeks, or a Mach3 attack run in low-level flight. "Low-level" as in "below the radar". Would have required some technological breakthrough or another, though -- materials science wasn't quite up to the task. Insofar, it is a cousin of the space elevator: the concept is sound, but there's nothing to build it with.

http://en.wikipedia.org/wiki/Supersonic_Low_Altitude_Missile

Then again, if you are content with saner speeds and/or higher altitudes, this could probably be made to work with current technology. That thing has more than enough thrust to move it's own weight and much else besides. Did someone say OP? I think we'd need an entirely new category, "OP" isn't enough.

[Stargate525]

That cruise missile / unmanned bomber pictured in the OP was supposed to be launched with boosters to bring it up to speed. Then I could have cruised for weeks, or a Mach3 attack run in low-level flight. "Low-level" as in "below the radar". Would have required some technological breakthrough or another, though -- materials science wasn't quite up to the task. Insofar, it is a cousin of the space elevator: the concept is sound, but there's nothing to build it with.

http://en.wikipedia.org/wiki/Supersonic_Low_Altitude_Missile

Then again, if you are content with saner speeds and/or higher altitudes, this could probably be made to work with current technology. That thing has more than enough thrust to move it's own weight and much else besides. Did someone say OP? I think we'd need an entirely new category, "OP" isn't enough.

Yes, because SQUAD has implemented all of its engines using precise, real-world numbers for its statistics...

Seriously. Very heavy, very expensive, terrible thrust at low speeds and low atmospheres, and it's an engine for getting about on a planet quickly. Considering there's very little to gain by doing this, contracts/science/career-wise, why NOT let it happen?

[UberFuber]

Yes, because SQUAD has implemented all of its engines using precise, real-world numbers for its statistics...

Seriously. Very heavy, very expensive, terrible thrust at low speeds and low atmospheres, and it's an engine for getting about on a planet quickly. Considering there's very little to gain by doing this, contracts/science/career-wise, why NOT let it happen?

Probably can be added as a mod. The behavior would be somewhat similar to the Firespitter propeller (except much bulkier, heavier, low thrust at low velocity, and consume no resources). In fact, the Firesplitter propeller mod could probably be adapted to implement the nuke jet engine.

[M3tal_Warrior]

Also in theory, nuclear engine don't need "intake air"

Just to clarify: Nuclear jet engines need quite a lot of intake gas, it just doesn't have to have oxygen in it (for the reason you named). Also the idea to do a turbojet/turbofan engine with nuclear reactor isn't really impossible - the research on it was killed too early and with inferior materials at that time. Modern materials (ceramics, carbon (nano) fibers and other alloys) would probably circumvent or solve the initial problems of those early engines (one should not forget jet engines were 20 years old when those nuclear engines were stopped - we know a lot more now about them). As for the drop in efficiency at high velocities: I'm not sure if mach 7 actually is a deadline for those engines. Press enough air into the reactor chamber and give it only a small nozzle it won't cool the reactor down too much and still have insane outlet velocities. Within game I know it's not a deadline for turbojet engines (broke that with a test jet once), although they are not able to produce as much heat as a nuclear engine.

I pretty much support the idea of a nuclear ramjet engine, but I'd like to see a nuclear turbojet engine as well (which then would be able to produce thrust with no initial velocity)

Just an idea to reduce it's use in Kerbin atmosphere (for the reason it being overpowered): Forbid it. Seriously, forbid the usage in Kerbin atmosphere, for safety reasons, and drain reputation massively if it is actually used. Also one could add a reputation threshold for buying them - one has to have a certain reputation, otherwise no one would trust you with these materials.

Edited August 5, 2014 by M3tal_Warrior

[zarakon]

The engine also acted as a secondary weapon for the missile: direct neutron radiation from the virtually unshielded reactor would sicken, injure, and/or kill living things beneath the flight path

huh, wonder why we abandoned these things..

[nli2work]

KSP Interstellar Mod.

[Jouni]

Just an idea to reduce it's use in Kerbin atmosphere (for the reason it being overpowered): Forbid it. Seriously, forbid the usage in Kerbin atmosphere, for safety reasons, and drain reputation massively if it is actually used. Also one could add a reputation threshold for buying them - one has to have a certain reputation, otherwise no one would trust you with these materials.

There's no need for such artificial restrictions. Assuming that the engine would have similar TWR as the LV-N, turbojets would beat it with a clear margin on Kerbin. Because of the bug in the fuel usage of airbreathing engines, a turbojet with more than enough fuel to reach orbit would weight less than the nuclear jet, while generating much more thrust.

[M3tal_Warrior]

Okay, that's a method too.

[RuBisCO]

KSP Interstellar Mod.

I don't think Interstellar Mod has a air-breathing nuclear engine in it.

[goduranus]

I don't think Interstellar Mod has a air-breathing nuclear engine in it.

It does, but unlike antimatter or moon-mining, nuclear jet is probably one of the most realistic technologies in that mod, where working prototypes were actually built in the real world.

I think you need to connect a reactor to a thermo jet in Interstellar. One of Scott Manley's interstellar quest episodes shows how to put it together.

Edited August 6, 2014 by goduranus