Opinion from roleplayers: Does the LV-N release "radioactive" exhaust?

[r4pt0r]

I was designing a Duna lander today, and wanted to use the LV-N, but then thought about possibly irradiating Duna's atmosphere in the act. So I looked into "Nuclear thermal rockets" as the ksp wiki called them.

Seems there are 3 types: Solid core, Liquid core, and Gas core

http://en.wikipedia.org/wiki/Nuclear_thermal_rocket#Types_of_Nuclear_Thermal_Rockets

Now, the last type, Gas, runs off a hypothetical concept called a "nuclear lightbulb" http://en.wikipedia.org/wiki/Nuclear_lightbulb

That design releases no radioactive material in operation, no matter in atmosphere or not.

Which type do you think the LV-N is?

And I know there is no "radiation" in stock ksp, this is just a question for those who like to add their own rules.

Edited April 21, 2014 by r4pt0r

[Captain Sierra]

Solid core has actually been test fired in reality, and the model most reflects modern renditions of solid core engines. How you treat NTRs is entirely up to you. I personally don't fire them in atmosphere under the assumption that they are solid core and would irradiate the atmosphere and landing site.

[khyron42]

Any NTR is a unshielded nuclear reactor. Most proposed designs rely on a "shadow shield," between the ship and the engine, to keep the crew itself from being fried. That shielding also keeps critical spaceship parts from becoming brittle due to radiation, electronics board from malfunctioning due to radiation, etc. In all other directions, it emits a dangerous amount of neutrons. However, aside from that narrow angle directly above the reactor, standing next to it is just like standing inside an active nuclear reactor; bad for your health.

Operating it within an atmosphere allows those neutrons to reflect off the atmosphere and give the crew a higher dose than they get in the vacuum of space. It would also convert atoms of the atmosphere itself into various radioactive isotopes. The quantities of those would be small, but you were asking specifically about contamination.

In general, if you're going for roleplaying realistic handling of them, they should be reserved for deep space use and actively shut down during any docking activities; even then they'll be putting out a smaller dose of radiation, so you should still try to keep the ship (and therefore shadow shield) between the docking craft and the engine at all times. Bring in another craft from the side and not only are you hitting that other craft with way too many neutrons, but many of those neutrons will reflect off the other craft and hit yours.

More information on nyrath's excellent website: http://www.projectrho.com/public_html/rocket/radiation.php#id--Radiation_Shielding--Shadow_Shield

[SRV Ron]

The nuke, in reality, is a mono propellant engine. It gets its efficiency from heating that propellant, usually hydrogen, to extremely high temperature. That provides a much higher thrust then just burning hydrogen with oxygen. That extra energy is provided by the nuclear fuel. While limited in reality, KSP assumes unlimited nuclear fuel in its engine and treats the engine as burning conventional fuel in the extra heat of the nuke at over twice the efficiency.

As far as using them in an atmosphere, their efficiency drops way down.

Just role play the engine as you see fit. I use them for interplanetary flight but don't use them for landing and return as an LV-909 or smaller is far more efficient for that task due to their much lighter mass.

[Rus-Evo]

Maybe Kerbals are radiated-mutated humans?

[r4pt0r]

no one can be right or wrong here, i just like hearing how others use them and their "rules" for them.

ive always only used them for out of atmosphere interplanetary tugs until i thought about a Duna lander (which worked fine with 2 small srbs to boost me out of the bulk of dunas thin air )

[theend3r]

Yes, it releases dangerous radiation but the impact a few of those engines have on an atmosphere of a planet is zero. My RP is that I don't fire them near populated areas such as my stations or bases.

[Canopus]

If the LV-N would be a Nuclear lightbulb, you wouldn't have to care to build any complex multistage rockets anymore. As everyone else said, it is modeled after a solid core NTR in which case the reaction mass flows around the fuel rods and gets contaminated.

[Geschosskopf]

To answer the title question: "Does the LV-N release radioactive exhaust"....

The answer there is "NO!", at least in my universe. Maybe actual LV-N designs do things differently, but I at least pretend it's perfectly possible to make the exhaust clean. See, just like in a typical nuclear power plant, the hot nuclear stuff is in its sealed containment vessel and if it needs any cooling fluid, that's also in a close system separate from the fuel/exhaust system. So, the fuel never comes into contact with anything radioactive. Either it flows over the outside of the containmente vessel, or it goes through a heat exchanger where it picks up the heat from the cooling fluid. But either way, the exhaust gases at exit contain no more radioactive atoms when they come out the nozzle than they did in the fuel tanks. And because no radioactive particles are coming out the back, there's no reflecting of them back at ship, so no need for a "shadow shield".

Now, the whole engine itself is of course a radiation source. But it's got enough shielding inside (which is why the engine is so heavy) to keep that from causing any problems. I mean, space is totally filled up with huge amounts of extremely nasty hard radiation from Kerbol and all the other stars in the sky. Any ship that has enough shielding to deal with this radiation on a long-term mission can easily shrug off what little comes from its LV-Ns. And even if it can't, from the crew's POV, the LV-N's radiation is the LEAST of their problems .

So, in my game, LV-Ns pose no problems to the crew or planets during normal operation. But what if they crash on the surface? I just don't worry about that. During actual NERVA testing, they had one malfunction and vomit out its radioactive guts. Analysis showed this was pretty close to what you could expect from a crash. Anyway, IIRC, it only contaminated an area about 1/2 an acre, and this was cleaned up fairly easily. So I figure, no problem.

[jalapen0]

Who cares if it does? Space is full of radiation.

[eurybaric]

Who cares if it does? Space is full of radiation.

Space is, yes, but he's talking in an atmosphere for example, or near ground crew (e.g. imagine an Orion type spacecraft blasting mini nukes behind it all the way up earth's atmosphere!).

I consider them to be radioactive. But like @theend3r , I also wouldnt't care using them on Duna if i'm not near any base.

Cheers!

[Sirrobert]

It releases some radiation, sure

But it does not release radiactive material.

And releasing some radiation in the upper atmosphere, noone gives a crap about that.

I don't fire them in lower atmosphere because they are inefficient

[Xaelath]

In my opinion, I'd rather not fire it near my Kerbals. In space maybe yes.

[Kasuha]

Earth models of nuclear propulsion use radioactive material to generate heat. No material of the radioactive core is ejected, only working medium which is not radioactive (as there's no need for it to be). So the only radiation that could potentially be released by such engine (without crashing it) may be caused by secondary radiation - the radiation of the heated core having some effect on the working medium and that becoming radioactive on its own. But that radiation is very limited (the working medium stays in the engine for very short time) and it can be estimated that total radiation dose the fuel receives from interplanetary space (and potential effects of it) is way higher than those from the radioactive core.

So if you don't hesitate to release "conventional" rocket exhaust in Duna atmosphere after carrying it around in interplanetary space for months, there's no need to worry about it getting any extra radiation by passing through your nuclear engine.

[Remkeau]

Despite the big scary trefoil painted onto the side of this engine, its radioactive exhaust, and tendency to overheat, the LV-N Atomic Rocket Motor is harmless. Mostly.

The original part description states it would have radioactive exhaust, so I guess that would be "canon". And yes, I also exclusively fire them on interplanetary voyages.

[r4pt0r]

The original part description states it would have radioactive exhaust, so I guess that would be "canon". And yes, I also exclusively fire them on interplanetary voyages.

oh....right....forgot about that haha

[SpaceSphereOfDeath]

I think they do emit radiation, but the kerbals don't care

[Hotblack Desiato]

but kerbals aren't honeybadgers...

in my universe I pretend that they are quite expensive and therefore I should use them carefully and that also means that they should not be disposed on some rock out there. the absolute no-go is: crash it onto kerbin, especially with deadly reentry, where the nuclear fallout could even cover a small state.

by the way, there are some nuclear fission reactors up there. the soviets placed them in radar satellites (solar power wasn't powerful enough). any idea when they will crash?

[Brotoro]

The LV-N looks like a NERVA nuclear rocket engine, so I assume that's what it is (also because KSP uses 'realistic' engine technology, and not much in the way of projected engine technologies, so that also points to the LV-N being a NERVA-style engine, which was developed in real life to the point where the next step was to built actual flight hardware).

The NERVA was a solid-core nuclear rocket engine design. The fission products of the nuclear reactions (the highly radioactive isotopes in a reactor's core) are contained in the reactor's fuel elements. The radioactive elements are not spewed out into space like some proposed nuclear engine designs. The reaction mass of the engine (hydrogen for the real-life NERVA…and apparently both oxidizer and fuel in KSP) passes through the engine, gets heated, and is expelled at high velocity…it doesn't hang around to get radioactive. I suppose you would get some materials from the fuel flow tubes that might get neutron-activated over time and some of that could get eroded away by the fuel flow and carried off with the exhaust…but I wouldn't expect that to be highly radioactive, although I would expect this effect to increase as the engine gets very old.

The NERVA does not have much in the way of shielding, so when it is operating it will be spraying out neutrons…so I would not put my manned pods alongside a nuclear engine. Best to put them on the other end of the rocket so there can be shielding (in the form of propellant tanks and other structures) in between the operating engine and your kerbals. I often include a radiation shadow shield in my designs (such as in my standard nuclear tug) to protect manned pods. Also, I assume that a nuclear engine that has been run for many minutes of firing time will be more radiaoctive than a fresh LV-N (since an un-fired solid core nuclear reactor need no be very radioactive at all)… so I tend to keep my EVAing kerbals away from old LV-Ns.

I do mount my LV-N engines so that they can be separated and recovered by parachute in the case of launch failures. I will use a fresh LV-N in the upper atmosphere, but generally not in the lower atmosphere where neutron backscatter could be a problem.

[aleis]

Another thing to consider would be Duna's magnetic field. If it isn't very strong or non-existent then the plant gets hit by ton of stellar radiation already and the little bit coming or the rocket probably doesn't matter

[jalapen0]

A kerbal's life is shorter than anything the effects of radiation would cause anyways.

[Felsmak]

Yes, and I enjoy every second of it.

[NERVAfan]

Earth models of nuclear propulsion use radioactive material to generate heat. No material of the radioactive core is ejected, only working medium which is not radioactive (as there's no need for it to be). So the only radiation that could potentially be released by such engine (without crashing it) may be caused by secondary radiation - the radiation of the heated core having some effect on the working medium and that becoming radioactive on its own. But that radiation is very limited (the working medium stays in the engine for very short time) and it can be estimated that total radiation dose the fuel receives from interplanetary space (and potential effects of it) is way higher than those from the radioactive core.

So if you don't hesitate to release "conventional" rocket exhaust in Duna atmosphere after carrying it around in interplanetary space for months, there's no need to worry about it getting any extra radiation by passing through your nuclear engine.

Right. The LV-N is a solid core NTR (you can tell because a gas core NTR would have much higher specific impulse), it is only releasing radioactive material if something has gone wrong and the reactor elements are being eroded away. If it is working as intended the uranium (or whatever) is staying in the reactor.

They would be fine to use in real life except that people are irrationally paranoid about radiation.

I think the comment about radioactive exhaust in the part description is a joke... unless the designers got it confused with some other engine, not sure.

[Othuyeg]

Kerbals are green, therefore they are resistant to radioactivity. This has been proven in scientific studies conducted in the University of Madeuplandia.

[Tex]

I would assume that yes, the LV-N is radioactive simply because the descriptions and such actually reference the engine's radioactive nature multiple times.