/sci/ - Science & Math

[Anonymous No.7269537]

I'm probably asking too much of 4chan, but just for the hell of it lets play with this idea:

If a planned spacecraft was constructed with an on-board nuclear fission reactor inside(solely for power generation, not propulsion) how would you design the reactor to minimize exposure and the dispersal of radioactive materials in the event of an explosion or crash?

[Anonymous No.7269541]

>>7269537
Exposure to what? The rest of the spacecraft? Put up a radiation shield and a way to vent the radioactive fluids in emergencies.

[Anonymous No.7269550]

>>7269537
Is a spacecraft ever unplanned?

[Anonymous No.7269551]

>>7269541
>Exposure to what? The rest of the spacecraft? Put up a radiation shield and a way to vent the radioactive fluids in emergencies.

Right that's a given. I meant if the craft crashes and some guy decided to walk up to the debris field and collect pieces for souvenirs, or to reduce environmental damage.

[Anonymous No.7269554]

>>7269550
Shutup

[Anonymous No.7269560]

>>7269551
Ah that's pretty difficult to do, I don't think there's any way you can ensure 100% that you keep the radioactive contained on impact, you can put a lot of inertial dampening and shielding around it, but it's probably not going to survive impact/explosions regardless. If the reactor is still in tact and you can eject it into orbit or give it a separate back up shoot that might help.

[Anonymous No.7269562]

>>7269550
Ha ha cute.

>>7269554
I was just about to direct him to /lit/

[Anonymous No.7269567]

>>7269560
Definitely not easy, is there some way to calculate the force of likely explosions though so you can at least incorporate that into the design?

I don't know if some sort of encapsulation would even be possible or light enough on the scale needed, just wondering.

[Anonymous No.7269569]

>>7269551

Not him but you wouldn't design the reactor itself to do that.

If "crashing" is an issue, then your goal should be to design the vehicle itself in such a manner so crashes aren't extremely likely to occur

For example, this could mean making the vehicle itself space-only (aka, it can't enter a planet's atmosphere) and has to use shuttles to get things from it to the ground

If that's impossible, then you could potentially (and I say, potentially, depending on what type of reactor you're using and what it's being used for) have it connected to a separate booster/section that could jettison during a crash and have much more shielding/insulation than other sections/boosters. I only bring this up because a regular fission reactor is different then the Project Pluto ones that could be used in a propulsion system.

But really, there's no reason to shield it that much. In the real world, if a naval sub were to have a meltdown the navy would literally just leave it on the floor of the ocean where it can't effect anyone. In deep space, or just space in general, the same is true. It would continue to be critical an kill the entire crew until it's just a metal shell flying through space, until it hits something nobody will ever live on.

[Anonymous No.7269570]

>>7269569

>In the real world, if a naval sub were to have a meltdown the navy would literally just leave it on the floor of the ocean where it can't effect anyone.

proofs:

https://en.wikipedia.org/wiki/List_of_sunken_nuclear_submarines

Russia especially is known for doing this, because at 4000 fathoms nobody can make a scandal over faulty equipment or poor training.

[Anonymous No.7269572]

>>7269537
>>7269570
>>7269569

[Anonymous No.7269575]

>>7269567
Explosion "force" depends on the pressure build up, so it would be the pressure at the tensile strength and wall thickness of your reactor.

[Anonymous No.7269579]

>>7269569

>If "crashing" is an issue, then your goal should be to design the vehicle itself in such a manner so crashes aren't extremely likely to occur

This op.

This is also partially why we don't use nuclear fission reactors in space yet, because they're incredibly complicated and fragile (mind you, they're effectively steam engines, because the reactor has to heat a boiler that turns a turbine). Hence why NASA uses betavoltaic radioisotope batteries in many instances, because despite being incredibly inefficient and low-power it has no moving components and will discharge enough power for a radio and computer over 50-500 years depending on what source you use (sr90 has a shorter life but is dirt cheap compared to u238 or plutonium).

[Anonymous No.7269582]

>>7269569
I know the Soviets made a few uranium powered satellites, one of which reentered in Canada in the '80s.

[Anonymous No.7269585]

>>7269582

They do, so does nasa. As this guy explained >>7269579 they still use them, iirc the recent mars rover has a nuclear backup battery on it. Many satellites do to because sr90 is commercially available for a few thousand dollars.

[Anonymous No.7269589]

Treacle in a box yo
Gives me the p to the hd

[Anonymous No.7269593]

>>7269537
Once the dangerous material is in orbit and out of the atmosphere earth would be a lot safer. There are some methods of non-rocket spacelaunch that seem like they may be particularly reliable. Using a space gun to lift the most dangerous materials and then assembling in space is a possibility.

[Anonymous No.7269598]

>>7269593

imo the better method would be just sending up each individual part and building it in space

only issue is that you need a physical boiler for a nuclear reactor, which needs a large amount of space for a midsized reactor and needs a lot of thermal shielding so it doesn't freeze in space

[Anonymous No.7269599]

>>7269579
>>7269585
An RTC is different from a fission reactor with a steam driven turbine, and unfortunately even if the spacecraft was never intended to land an accident during launch would still need to be considered.

[Anonymous No.7269608]

>>7269599

I know it's different, it's used specifically because it's basically a battery and not an actual reactor.

> and unfortunately even if the spacecraft was never intended to land an accident during launch would still need to be considered.

not really, given that nasa never makes plans for what happens when satellites crash. Things burn up in the atmosphere and then maybe the frame hits earth as unrecognizable debris. "crashes" only need to be considered when you have humans onboard, but even then most of your crashes are going to be with other spacecraft (say, a satellite you're trying to repair or with another ship/station you're trying to dock with). When it comes to that, your main issues are going to be maintaining hull integrity so that the pressure doesn't cause it to rupture. Submarines have similar issues.

[Anonymous No.7269611]

Safety is nice to think about and all, but is a reactor the best thing to use in the first place?

A serious design consideration with nuclear reactor powered spacecraft is the dissipation of heat. The only way to dissipate is radiation, which is very slow compared to the ways we're used to on Earth.

I have no doubt a submarine-sized reactor would be totally unsuitable without a bunch of downsizing. Subs have whole oceans to cool them, so dissipating heat isn't much of a concern.

There are better ways to power a spacecraft. If you're inside the astroid belt, solar panels work pretty well. RTGs are also an option. Also, a reactor and associated components is _heavy_as_fuck_, and the more weight, the less dV.

>>7269585
As far as I know they used Pu-239 for the RTGs, no? Cold War era RTGs used Pu, not sure if they've switched yet.

pic related, a tiny SNAP-10A reactor used for powering satellites in Earth orbit. Check the wiki out OP.

[Anonymous No.7269621]

>>7269611

>As far as I know they used Pu-239 for the RTGs, no? Cold War era RTGs used Pu, not sure if they've switched yet.

NASA I know switched to sr90 as do many commercial satellites because it's cheaper than Pu or Ur. Only issue is that you get a shorter life and require more of it. But given that many satellites only had/have an expected lifespan of 10-20 years (at least many commercial ones) it's considered good enough.

[Anonymous No.7269624]

>>7269593
Space guns only get you near earth orbit and you need a rocket capable of taking the acceleration to finish. Doesn't sound too reliable to me. Try one of the other technologies.
>>7269598
You don't need a nuclear reactor to make use of fissionable material. At the very least, nuclear thermal rockets are promising.

[Anonymous No.7269648]

>>7269624
>At the very least, nuclear thermal rockets are promising.

but that's irrelevant if propulsion was not the main reason you wanted the power from a nuclear reaction

[Anonymous No.7269666]

>>7269648
Use the dirty technology in space rather than to achieve orbit. Because gotta go fast.

[Anonymous No.7269679]

>>7269666
i recommend hydrogen fuel cells for power generation

[Anonymous No.7269716]

>>7269570
Fuck that was one of the most beautiful wikis I've seen.

[Anonymous No.7269805]

>>7269716

it's called "english wikipedia" aka "wikipedia"

[Anonymous No.7269829]

>>7269537
http://en.wikipedia.org/wiki/Nuclear_thermal_rocket
In January 1965, the U.S. Rover program purposely placed a Kiwi Reactor (KIWI-TNT) on fast excursion to simulate a worst-case scenario of a fall from altitude into the ocean such as might occur in a booster failure after launch. The rocket was positioned on a railroad car in the Jackass Flats area of the Nevada Test Site, with the reactor specially modified so as to go prompt critical.

The radiation released would have caused fatalities out to 600 feet and injuries out to 2000 feet.[7]

Current solid-core nuclear thermal rocket designs may greatly limit the dispersion and break-up of potentially radioactive fuel elements and thereby confine the overall hazard from the elements to near the launch site and reduce it to a level that would be lower than the many open-air nuclear weapons tests of the 1950s.

[Anonymous No.7270370]

>>7269537

I think even the smallest naval reactor(the Alfa's reactor AFAIK) would be way too big

but both the soviets and the US have sent small NaK cooled reactors into space

NASA has been developing heat pipe cooled fast reactors

they've came up with the SAFE-400 400 KWt reactor, HOMER-15 15 KWt reactor and most recently the KiloPower 4 KWt reactor

https://www.youtube.com/watch?t=171&v=KobRfGqlpGc

pretty cool tbh

[Anonymous No.7270383]

>/sci/ trying to talk about anything not related to popscience, pseudoscience and freshman level math
holy fuck you people are dumb

[Anonymous No.7270647]

>>7270383
u wot m8?

[Anonymous No.7270771]

>>7269537
is this a strictly orbital craft or are you talking about something that you launch from the ground?

in a midair rapid deconstruction a reactor would be in a very bad place really no matter what unless you have an LES specifically for it

[Anonymous No.7270789]

>>7270771
not OP but a shuttle that could land on the ground would be interesting

[Anonymous No.7270830]

>>7269537
>>7270771
>tfw no SSTO nuclear powered RL S-F spaceship

[Anonymous No.7270911]

>>7270383

[Anonymous No.7270917]

>>7270911
>not using liquid methane

pleb

[Anonymous No.7270980]

>>7270911

[Anonymous No.7271005]

>>7269611
Use a helium Brayton cycle. You'll still hit about 20% efficiency in radiative only heat exchangers.

[Anonymous No.7271021]

>>7271005
Are you a nuclear engineer?

[Anonymous No.7271077]

it would be easier to build a fusion reactor fusing deuterium and 3helium.

fusion is currently stuck on
1) plasma bursts damaging the containment
this can / will be fixed by switching from tokamaks to stellerators. check wendelstein 7x.
2) part of the energy released is high energy neutrons, wich wreck containment material and decay afterwards i.e. radioactive blanker has be replaced after 20y
fixed cause we use D-3He instead of D-T
3) tritium is radioactice and needs to be produced by spammin Li with neutrons
fixed by D-3He
4) people suck at manufacteroing these things i.e. it takes long and is expensive
practice i guess
5) inadequate funding, political meddling
i dont see a cure besides goimg private asap.

the provlem inspace fusion faces is heat dissapation. rogue heat capture has to be near perfect.


one of the cooler things you can do with it is wiki VASIMIR. i.e. plasma rocket.
tl;dr accelleration not limited to a chemical eeaction. uses magnets powered by elecrricity to push ions (from a plasma) out.
can go really fast. if enough electricity.

[Anonymous No.7271403]

>>7271077
>it would be easier to build a fusion reactor fusing deuterium and 3helium.

No it wouldn't, because sustainable fusion reactors that produce more energy than consumed do not exist yet.

1 through 5 are not small issues.....

[Anonymous No.7271778]

>>7269537
With current nuclear fission reactor technologies, one in space will never work until we have the capability of providing large amounts makeup water.

So it's kind of a moot point.

[Anonymous No.7272410]

>>7271403
ITER will produce 500mw with 50mw input. for 300seconds. the reason i cant run longer is because its not a stellerator. and also because its not an eneegy plant but a very larfe experiment. i.e. they do mostly testing there.

I provided solutions for all the points. maybe work on your reading comprehension

[Anonymous No.7272415]

>>7271077
>>7271403
>>7272410
lel i just love it when people just mindlessly repeat shit theyve heard at one point in their lives without any actual knowledge about the subject

[Anonymous No.7272428]

>>7271778
Gas-cooled reactors aren't news. The problem is shielding and heat rejection

[Anonymous No.7272431]

>>7271778
>one in space will never work until
>http://en.wikipedia.org/wiki/Nuclear_power_in_space

>Russia has sent about 40 reactors into space and its TOPAZ-II reactor can produce 10 kilowatts.
>The United States tested a nuclear reactor in space for 43 days in 1965

[Anonymous No.7272594]

>>7272415
Do you love irony as well?

[Anonymous No.7272733]

>>7272415
behold the PhD in applied fusion plasma physics
that makes 0 arguments and instead posts a 1liner insulting people

[Anonymous No.7272777]

>>7272594
>>7272733
lel ask me anything about fusion power

[Anonymous No.7272783]

>>7272777
post your degree with timestamp faggot

[Anonymous No.7272785]

>>7272783
that's not a question

[Anonymous No.7272872]

>the more I work in the nuclear industry the more I realize it's a giant cash cow for the engineering consultors involved
This shit is the fucking best

[Anonymous No.7272883]

>>7272777
Ok god. How much energy was released when my purple throbbing cock fused with your mom's fertile womb last night?

[Anonymous No.7272896]

>>7272883
>implying his mom is still fertile
Not likely

[Anonymous No.7272976]

>>7271021
Yes, actually.

[Anonymous No.7272988]

>>7272976
>all of a sudden everyone on /sci/ is a nuclear engineer
i know theres the purdue guy and the nc state guy but shit, i cant tell if everyones just full of shit or what