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

[Hans Dorn]

After reading up on the nuclear salt water rocket I came to the conclusion that it's way more kerbal than the NERVA.

http://en.wikipedia.org/wiki/Nuclear_salt-water_rocket

[Immashift]

Sure it does. My logic: Kerbals are green anyway. A healthy glow is just gonna make 'em happier.

[Rainbow-Dashie]

In my roleplay: Yes, it does release Radioactive exhaust, however, judging by the safety protocols in place by the KSP (absolutely none what so ever) nobody gives a care in the world if it pollutes anything

[architeuthis]

Radiation? Yes. Lord yes.

Radioactivity? Unless the fuel elements are leaking, or neutron activated stuff is ablating in the exhaust stream, then no.

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.

Kerbals? Safety features? The NERVA integral shadow shield (not including the external shield) is a thick disk of beryllium and tungsten. Its got a planar density of around 3500kg/m^2, and the the Kerbal LV-N is about 1 meter in diameter. The LV-N only weighs 2.25 tons, which means it is %122 shielding by mass:) Lets face it, the only thing between those poor kerbonauts and the atomic gorgon is the propellant tanks... you've got propellant tanks between the kerbals and the reactor right?

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

Not because safety, the radiation is probably not much compared to levels typical in many space environments

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.

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 .

Space radiation consists mostly of protons from the solar wind, solar storm protons, x-rays and cosmic rays. NASA expects astronauts on a 360 day round trip to Mars to accumulate close 1 Sievert of absorbed radiation. As a chronic dose this is associated with a 3% increased risk of cancer. For sure, space is radioactive.

If however, you are unfortunate enough to be EVA'ing about 1.5 meters from the immediate vicinity of an operating NERVA type engine you would be raking in over 200 billion Sieverts per second! At this rate of abosorbed radiation you would get an acute fatal dose in roughly 0.375 trillionths of a second. Simply put, space radiation doesn't compare with this (unless you are orbiting a neutron star or something). I'm not at all against NERVA, they are probably quite safe (and obviously incredibly useful) when used correctly. (Frankly I'm impressed NASA even bothered doing the analysis for the operating absorbed radiation environment at that resolution, who would be stupid enough to bear hug an operating nuclear reactor core? Kerbals I guess?)

As soon as the fission reaction is stopped, neutron and gamma flux decay exponentially, to roughly safe levels within 4-10 hours (depending on the length of the burn). The gradual build up nasty fission products in LV-N will also put out residual gamma depending on the reactor's operational history (e.g. how many times it has lit for a burn), at a roughly constant rate irregardless of how recently the reactor was in operation.

If you want to roleplay the LV-N these I think make good rules of thumb: don't run the LV-N within 50-100km of a space station or an EVA'd kerbal (use RCS for docking maneuvers). If you want to get fancy, always keep the LV-N pointed away from your docking targets as you approach them. Never put a Kerbal within a clear line of sight of the reactor. And for the sweet love of god don't use them for landing stages.

Of course, rockets never fail during launch, and what are the chances that a nuclear powered satellite would undergo an uncontrolled re-entry, scattering nuclear material over a wide area?

People get worked up about this, but ironically this probably the safest time for a nuclear reactor. As brotero already mentioned earlier in the thread, nuclear reactors emit lots of gamma and neutron radiation when they are actively running because of the fission reaction. If they are not running they are just a lump of uranium, and uranium is not particularly radioactive. A launch failure with an inert reactor wouldn't be a "space Chernobyl", it would probably be less environmentally devastating than the unfortunately routine chemical spills which happen hundreds of times a year all over the Earth. The Kosmos satellite was more dangerous because it was an uncontrolled reentry of an old reactor. Old reactors will have built up fission byproducts which are much more highly radioactive.

Edited April 22, 2014 by architeuthis

[shizophrenic]

never take me wrong, radioaktivity is dangerous and should be used very carefully.

Here is much talk about radioactivity and it seems some are struck by fear just reading the word. we all are always hit by Radiation (cosmic, clinical and from trace isotopes around us). if you ignore the ionising part you can define the light from a simple light bulb as extremly low energy Gamma Radiation (electromagnetic wave).

no nuclear plant (or engine) would want Gamma Radiation since you can't easily extract the energy like you want. the nuclear plants aim a high Ratio for alpha, beta or Neutron (prefered) Radiation. the energy of these Radiation lies mainly in movement of their particels, whats equal to a theoretical (very high) temperature. To other Atoms they lose this energy through collision or electromagnetic interaction (this not for Neutrons), their movement is slowed down and the surrounding matter heats up (gaining Speed). as the mass for Neutron is almost equal to hydrogen, hydrogen Atoms are best for slowing down. for shielding purposes the rocket fuels fits that criteria perfect

for Gamma Radiation you want high density materials (e.g. lead) to raise the probability for interacting with their electrostatic and magnetic fields.

Alpha and beta Radiation can be completely shielded with quite thin metal Sheets, and are only problematic if they are incorporated.

for a nuclear enigne follws:

1. mainly Neutron Radiation

2. Neutrons should have lost most of their energy in the engine (most People Forget that Point)

3. between engine and 'fragile' parts would be usually the fuel tank

4. reflection on other ships shouldn't be a Problem due to 2, 3 and Radiation density should go down with ~ 1/r^3

5. the isotopic Generation through the Neutrons, for the fuel Atoms there wouldn't be a significant raise in their natural Distribution. leaves the engine parts which are fixed. depending on the materials used (half time, Radiation emmited) they are be deposited.

as stated by others the cosmic Radiation from the sun and all other sources outside the solar System since the energy in way up higher. a nuclear fission results usually in particles with energy about 2*10^6 eV. nuclear Fusion like in the sun starts at 14*10^6eV. Cosmic Radiation is measured up to 10^22eV.

for health reasons Radiation in itself isn't the Problem, it is the deposited energy (the energy loses during the passage) in Body/cells.

here you have to differate the three possiblitys

1. deposited energy is to low to do something (like raise temperature in a cell a Little). no Problems here.

2. deposited energy leads to a chemical reaction through collsion, temperature or ionisation. this part can lead to a genetic modification, which usually kills the cell, gets the cell killed by the own immune system or with lower probability to cancer/Mutation (cell must still function, be accecpted by the immune System and be able to reproduce).

3. deposited energy is so high that the cell dies instantly (loss of lots of cells leads to Radiation sickness, death). this would be bad and you have 2. too.

again.

never take me wrong, radioaktivity is dangerous and no one should suffer through it.

if you Interpret it zynical you can see Point 2. :

Mutation isn't bad and happens all the time. It is the engine of Evolution.

Mutation through artifical Radioaktivity is like an additional Mutation on top of the normal. Ist like an accelerated Evolution. (well for those who suffer from it sounds hollow)

knowing kerbals they are fine with that.

[NERVAfan]

It doesn't matter where it lands. It's a big hassle dealing with a reactor that isn't meant to fly. Launch something nuclear from KSC, let it explode over the Atlantic, and watch public opinion and political fallout wrap you in enough red tape to keep you from attempting another launch for a decade.

Sure. I'm just saying the difficulties are (irrational) politics not the (small) actual risk.

[cantab]

Radiation? Yes. Lord yes.

Radioactivity? Unless the fuel elements are leaking, or neutron activated stuff is ablating in the exhaust stream, then no.

Thank you for drawing the distinction.

[SDIR]

Looking at the ISP readings, it seems that the LV-N is most likely solid core, since liquid cores would make any nuclear vehicle absolutely overpowered by the games standards.