/sci/ - Science & Math

[Anonymous No.5765239]

Alright /sci/, I'm a dumbass motherfucker, so can someone explain the following to me.

Why can't we throw a nuclear power plant in space, strap two engines to it and start exploring the solar system?

[Anonymous No.5765241]

>>5765239
what kind of engines?
steam turbines? propellers?

[Anonymous No.5765243]

>>5765241

Well, you already threw that nuclear power plant in space, you can use it to power the engine.

[Anonymous No.5765244]

>>5765239
We did. We called it Voyager. Shit's powered by plutonium, yo.

[Anonymous No.5765245]

>>5765244

So why not do it to the international space station? Or something you can put humans in?

[Anonymous No.5765246]

>>5765241
This.
>>5765239
Energy != Propulsion
And how do you put a stable nuclear power plant in space?

[Anonymous No.5765248]

>>5765246
>And how do you put a stable nuclear power plant in space?

I don't know, I'm just thinking of some powerful and lasting power source that can give the most bang for your buck.

[Anonymous No.5765250]

>>5765248
well then you want an atomic bomb, not atomic power plant
most nuclear plants I know convert heat into kinetic energy using steam turbines and that's not really most BANG money can buy.
we can do the same shit with dead dinosaurs

[Anonymous No.5765252]

>>5765245
Two reasons:

1. Space is really big. I mean vastly, hugely, mindbogglingly big. I mean, you may think it's a long way down the road to the chemist's, but that's peanuts compared to space. It took Voyager about 35 years to get from here to the edge of the solar system, and that's a one way trip.

2. Powering a spacecraft with nuclear fuel generally means you're going to make your spacecraft increasingly radioactive the longer it operates. Not conducive to long term survival of humans.

[Anonymous No.5765254]

>>5765248
>>5765250
Powering a spacecraft via the shockwaves of atomic bomb explosions is currently a theoretical idea, which hasn't been tested mostly on account of it being batshit crazy.

[Anonymous No.5765255]

>>5765252
>Space is really big. I mean vastly, hugely, mindbogglingly big. I mean, you may think it's a long way down the road to the chemist's, but that's peanuts compared to space. It took Voyager about 35 years to get from here to the edge of the solar system, and that's a one way trip.

I'm not saying put colonists in there. Just send scientists on five year missions to Saturn or Venus.

[Anonymous No.5765256]

>>5765248
Solarrrrrrrrr

But yeah nuclear would be a neat idea, it was heavily considered and developed. Loop up project Orion. Only problem is heat dissipation and making sure it doesn't explode on the way up.

[Anonymous No.5765260]

>>5765250
OP probably thinks nuclear power plants create electricity with contained nuclear explosions

[Anonymous No.5765261]

>>5765255
5 year missions to Mars/Venus are perfectly viable. They just lack funding. In part because people are wusses and don't see the advantage of going to Mars when they can just send some robots. (Although those missions are low on funding too.)

[Anonymous No.5765259]

>>5765239

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

Expense is really the only reason.

[Anonymous No.5765267]

>>5765261
>They just lack funding

So how much would it cost to build and maintain a vehicle like that (optimal build, no need to be nuclear powered) something like that? 60 Billion? 120 Billion?

[Anonymous No.5765273]

>>5765267
No idea. Try getting in contact with NASA and asking their engineers.

[Anonymous No.5765292]

>>5765267
getting 15 metric tons of shit to high orbit costs on average 225 million dollars

for reference single RBMK reactor weighs something around 17,000 tons

have fun

[Anonymous No.5765324]

>>5765239

The biggest reason I can think of is heat dissipation. Nuclear power stations generate a lot of heat, more so than coal fire or anything else. Since space is a vacuum, there is *no way* to cool the damn thing, the space craft would essentially be stuck inside of a thermos, holding all of the heat from the nuclear power source. `

[Anonymous No.5765325]

>>5765245
Mars One.

[Anonymous No.5765327]

>>5765244

That is not a nuclear reactor, its lump of by product from enrichment process that has a lot of alpha decay, which is useful for long lasting low power applications, like powering systems on and hall effect thrusters. What OP was talking was a nuclear reactor generating in excess of 100MWe and powering something with high thrust to weight ratio (for example something like the upcoming VASIMR plasma rocket).

[Anonymous No.5765328]

>>5765244

That is not a nuclear reactor, its lump of by product from enrichment process that has a lot of alpha decay, which is useful for long lasting low power applications, like powering systems on small probes and hall effect thrusters. What OP was talking was a nuclear reactor generating in excess of 100MWe and powering something with high thrust to weight ratio (for example something like the upcoming VASIMR plasma rocket).

[Anonymous No.5765334]

>>5765245
>So why not do it to the international space station?

Because solar power works great. And because launching radioactive material into orbit is very dangerous.

[Anonymous No.5765337]

>>5765254
batshit crazy and mother fucking awesome. bet that thing would haul ass. we need to make one now.

[Anonymous No.5765359]

>>5765241

Electric Plasma propulsion.

[Anonymous No.5765369]

Holy shit, /sci/ it's my day to shine!

Atomic Rockets are. the. shit.
They kick chemical rockets' collective asses from here to... wherever you want to go!

Okay, so for starters, here's a crash course in rocket terminology/design:

Fuel vs Remass

Fuel is what a rocket uses for energy, and Reaction mass is what a rocket throws out the back of itself to make itself move in the opposite direction.

With chemical rockets (like what the Saturn V and Space Shuttle launch vehicles used), your fuel and your remass are the same thing. You burn your fuel, and the exhaust gets thrown out the back as remass.

It's a good design! It's good because we humans are pretty good at making energy-dense fuels to burn. But there's a better way: Atoms.

In an atomic rocket, your fuel is plutonium or uranium fuel rods, bars of radioactive material that gets hot from the radioactive decay it continuously undergoes. Your remass is some kind of material that expands at high temperatures, so you can expose it to the heat from your fuel and throw it out the back to make your rocket move forward. You wouldn't think the process would be much more efficient than chemical rockets, because you have to lug all your fuel around with you the whole time, even as your remass dwindles. This makes for heavier "empty" ships, and heavier ships are less efficient. BUT: Radioactive material is *tremendously* energy dense!

Burning a metric ton of liquid hydrogen will net you about 8,000 kilowatt hours of energy, which we can write down as having an energy density of 8,000 kWh/ton. That's a lot! Coal is under 7,000, and coal is so energy dense we use it to make most of the electricity the world uses. But uranium kicks both coal and hydrogen's ass, it has an energy density of 2,000,000 kWh/ton.

[Anonymous No.5765383]

>>5765369
Continued

Now if atomic rockets are so great, why don't we use them for everything?

Two reasons:

1.) Radiation
2.) Radiation

Okay, the first reason is that atomic rockets use radioactive fuel, and so if they crash or explode, the fuel goes all over the place in what is practice is no different than a "dirty bomb." Radioactive debris (and dust, don't forget dust!) is terribly hazardous to almost all forms of life, humans definitely included.

The second reason is that even if the rocket doesn't explode and the rocket doesn't crash and it's a perfect launch and the news stations can a ten-second clip of the lift-off set to the national anthem for two days straight, the rocket exhaust is still likely to be mildly radioactive (or not mildly at all, depending on the design!). Even slightly radioactive exhaust simply is a terrible choice for your launch vehicle unless you're launching from a planet you don't intend to return to for a few thousand years.

Atomic rockets are, however, *excellent* for interplanetary craft, and should always be used! And so of course they're not. Why? Because building them in orbit would require launching large amounts of radioactive material, and the public generally does not like the idea of that. To their minds, it sounds like some idiot throwing a nuclear power plant into space.

[Anonymous No.5765389]

>>5765246
Tecnically energy is mass and mass can cause propulsion. Even though the thrust is incredible small you can power a spaceship with a flashlight.

[Anonymous No.5765390]

>>5765383
awesome explanation. it seems the health/damage factor is the biggest deterrent

a fictitious situational question: if robots/intelligent cockroaches finally replace us, do you think they'd send atomic rockets (because they're not particularly susceptible to the risk factor and all)

[Anonymous No.5765395]

Isn't nuclear just steam 3.0?

[Anonymous No.5765398]

>>5765390

Assuming they use rockets, then yes, that sounds reasonable, especially for trips where Earth is both the start and end point, i.e., using an ICBM as a means of transportation (ideally, you land it at the end rather than crash it in to your destination). This is because Earth has large amounts of liquid water on it surface. You could fill an atomic ship with ordinary seawater for reaction mass, turn it into slightly (or not-so-slightly) radioactive steam, and fly yourself to the other side of the planet in no time at all. Refill and repeat. Depending on the level of technology, however, there may be even more efficient ways of reaching orbit, especially if g-force is not a factor (for artificial life forms and the like). A Verne Gun, uses an atomic bomb detonation in an underground shaft to fire a huge (ten international space stations huge) payload into orbit. It's like an Orion drive, except several order of magnitudes more efficient, because all the energy gets put into your payload instead of only the part of the blast that hits your pusher plate.

[Anonymous No.5765406]

>>5765395

In nuclear reactors, yes. In space they often use direct heat-gradient-to-electricity designs, which use something called a thermocouple to exploit the second law of thermodynamics. Basically, you make something hot, and because heat always flows from areas of high concentration to areas of lower concentration, you make it do work for you as it does so. This is NOT "heat into electricity," rather this is *heat gradient* into electricity.

[Anonymous No.5765418]

>>5765398
awesome. thanks men. gonna dream of intelligent space-faring roaches tonight.

hmm i guess they'd like that. I mean, no more danger of getting stuck on your back in space, right? haha

[Anonymous No.5765428]

>>5765426

info* derp

[Anonymous No.5765426]

>>5765418
My pleasure. Please go here for more atomic rocket into than you'll ever, ever need:

http://www.projectrho.com/public_html/rocket/index.php

[Anonymous No.5765465]

I find it sad that nobody here has actually explained yet how your average nuclear reactor works.

They're basically a modification of the steam engine. This basic technology hasn't increased by leaps and bounds in hundreds of years. You still pump steam into an engine to generate energy.
The difference with nuclear energy, is you use the heat of nuclear processes to create massive amounts of steam.
THE REASON we can't do it in space is because for this to operate you need a constant flow of massive amounts of water. That doesn't exist in space. Also, the water has to be treated and monitored for hardness and things like that, which compared to finding the water wouldn't be that hard, but still presents a barrier.

I'm not sure where we're at on the cutting edge of this technology, if there are ways to get around using water and still maintaining high energy output or whatever. I'd say look at nuclear submarines for how to keep it contained in a small vessel.

[Anonymous No.5765477]

>>5765465
I find it sad that you assume bullshit without reading the thread

[Anonymous No.5765486]

>>5765465

Not exactly. The reason you don't want to put a nuclear reactor in space is because in space it's pretty hard to get rid of heat, which you must do to prevent your spacecraft from melting. Radiating it away is about the best you can do, and radiators are often large, flimsy, finicky things.

The bit you said about about massive amounts of water: I think for some reason you think that once the water gets used once it cannot be used again. This is obviously untrue. You could use radiators to cool the water down until it can be used again. The water that leaves a power plant has to be more closely monitored because it will rejoin the water table.

But all of this misses the point of a spacecraft. The *real* reason why you don't want to do it in space is that turning heat into electricity only to turn that electricity into propulsion is an absurd waste of energy and mass. Just use the heat to accelerate your remass, as described above. Take your uranium rods, arrange them around a tube, let it get good and hot, run a jet of liquid hydrogen through it, and bam: Propulsion. You don't even have to bring oxygen to combust it.

[Anonymous No.5765503]

>>5765369
>material that expands at high temperatures
Is there a limit or limit of diminishing returns when expanding such a matierial with heat? Is it possible to increase the heat supplied to proportionally increase the increase in volume indefinitely?

I'm not particularly knowledgeable about this topic, but I'd imagine that the remass's electrons would absorb the infrared wavelength energy, escape and turn the remass into a plasma that no longer behaves the right way.

[Anonymous No.5765538]

That uranium-heated hydrogen reaction mass idea sounds excellent, until you realise that both the uranium fuel rods and any hydrogen you collect and compress during the journey is all going to generate heat, which is a big issue on habitable tin cans moving through vacuum.
You'd need fragile radiators all over the engines to keep it at a reasonable temperature, and if they're damaged then you'll need to replace them or fry. Replacements would require additional mass to be carried. Thermocouples would break down and need replacing eventually, which requires additional mass to be carried. There's just no way to get rid of the heat fast enough to keep a spaceship habitable.

[Anonymous No.5765554]

>>5765503

Ignoring the bit about electrons, even as plasma it will have mass, and so will function fine as reaction mass. Doesn't matter it it's frozen or plasma; throw it out the back at high speed and you will move forward.

Now there are some reaction products from more exotic engines (fusion engines!) which we would have trouble making do work for us. Many fusion reactions produce neutrons, which, being uncharged, can't be reflected by a charged field in order to rob them of their kinetic energy and use it to accelerate our ship. Instead we need tons of heavy shielding (or a little shielding and a lot of distance, which is generally a better solution as distance doesn't weigh much) to protect us from energy that we should be using to make our spacecraft go. There are equally exotic solutions to this exotic problem, as well. Aneutronic fusion, chiefly. By choosing our fusion reagents and reaction well, we can limit the amount of products which won't contribute to forward movement. Of course all of this is still hundreds of years away (probably hundreds, anyway. though fancy new computers might help us squeak one out in our lifetime... assuming we live to be very old).

[Anonymous No.5765557]

Because of a UN convention against the use of Nuclear weapons in space.

That is the only reason it's not been done.

[Anonymous No.5765566]

>>5765557
Oh christ, not this again. Weapons-grade nuclear material is drastically different from reactor-grade material. As a result nuclear reactors are simply incapable of being anything worse than a dirty bomb (such as in the worst-case scenario of Chernobyl, where the reactor operators pretty much removed every single safety at once and the reactor itself was using a then-obsolete carbon mediator block that caught fire due to said negligence and puffed uranium-laced smoke into the skies of Europe).

http://en.wikipedia.org/wiki/Weapons-grade
http://en.wikipedia.org/wiki/Reactor-grade

[Anonymous No.5765567]

And on a related side note we are already doing that on a small scale, by using thermocouples strapped to little bits of decaying material ( not sure what the material actually is ) you can then turn the heat straight into electricity with no moving parts. It's called an RTG, and the Soviets were using them to power lighthouses and shit back in the day because they're pretty reliable and predictable. Mars Science Laboratory and New Horizons both use RTGs because they are too far away from the sun for Solar Panels to work. But they don't generate enough power to power an ion engine or whatnot, so they're not really feasible for powering engines in space, more for just keeping instruments running and the excess heat they generate is also useful in stopping shit from freezing up.

Anyway, until they actually come up with an electric engine which is powerful enough to rival chemical rockets ( VASIMIR? I was told that's a hoax though ) any electricity you have in space to use as propulsion is pretty useless. And until then chemical rockets will always be king.

[Anonymous No.5765569]

>>5765538

Not true as all. Radiator fins would be more than sufficient, and it's unlikely they would be damaged by anything that wouldn't destroy a spacecraft regardless of the sort of engine it's using. Again, I agree that the radiators would be one of the weakest and most vital parts of the ship, but you only need them for such a short time: the time your engines are running, and the res of the time they just sit there doing nothing. Also, there's not much to go wrong with them, assuming they're mounted externally on a ship not designed for atmospheric flight. The ones on the space shuttle were trouble because they were mounted on the inside of the cargo bay doors, which meant that if the doors couldn't be opened, the ship would melt (and yes, the situation really was always that serious. Space is dangerous).

Also, I feel there are some people who thing I'm talking about the kind of radiators that heat your house, with a liquid being pumped through them. But space radiators are big, shiney, blocks of metal which shine with infrared (and if you're really pumping out the heat, visible light) radiation. It can get hit by micrometeorites and keep working just fine. Design a ship that works with three and then build it with four, and you'll be fine.

[Anonymous No.5765586]

>>5765567
>And until then chemical rockets will always be king.

Oh, it is to laugh. Undeniably, atomic rockets are not beloved by the public. But math dictates rocket design. When a pound of anything costs $30,000 to lift to orbit, and a pound of chemical propellant gets you X delta-v and a pound of atomic fuel and reaction mass gets you a thousand X delta-v, you hire a PR firm to convince the public to embrace atomic rocketry. I don't have to argue my point further. The future of space exploration will be evidence enough.

[Anonymous No.5765608]

>>5765586

Well there's no denying that Atomic Rockets are more powerful, but the fact is that they are banned and that's a ban that doesn't look like it's going to be lifted any time soon. If it wasn't there, we'd certainly have gone further than me have now, I don't deny; but all the technology we have at the moment is geared for Chemical and Electric rockets, nobody is researching for Nuclear rockets, and nobody is lobbying the UN for their ban to be lifted.

Unless there is a breakthrough in Electric rockets, or nuclear rockets are made legal then we will be using chemical rockets. Additionally consider the following; if humanity does start mining asteroids, as well as the large amounts of metal found in them; there will also be large amounts of H2 and O2, and that's when going beyond earth orbit really starts getting economical. Because that's when we can cache rocket fuel in LEO or wherever you like, and you only need a rocket capable of launching to the cache that can then be refueled with fuel which has never had to have been lifted into space, thus a saving a great deal of Delta-V and greatly increasing the economic viability of Chemical rockets, which given their current dominance are already becoming cheaper and cheaper, and will continue to do so unless we find an alternate means of propulsion, which for the near future at least doesn't look like Nuclear rockets. No matter how good they are. I would say it's more likely to be electric rockets.

[Anonymous No.5765681]

Forgive me if i show any lack of knowledge
What are the problems with mass drivers and orbital elvators being used to launch payloads from space then?

[Anonymous No.5765694]

>>5765681
>What are the problems with mass drivers and orbital elvators being used to launch payloads from space then?

Well for one thing, they don't exist.

[Teichii !!+Ic1HejArqD No.5765709]

>>5765337
You won't like "Evacuate earth"
I fucking raged so bad when they were considering antimatter explosions underneath the ship with a big parabolic disc to deflect the energy at the spaceship so it leaves orbit.

[Anonymous No.5765726]

>>5765681
Orbital elevators require a significant proof mass in geo-stationary orbit. In order for the orbit to be stable (Not needing persistant thrust control to maintain orbit) it would need to be placed at one of the Earths Lagrangian points. Obviously, this one of the key challenges as a large proof mass would require powerful (hungry) thrusters. But one of the biggest challenges is our material capabilities. The mass of the elevator would be so great (cost, structural forces), and the tensile and compressive strengths required so great (support it's own weight, potential changes in orbit/failures in thrust control, terrestrial weather, etc), and the costs of maintaining such a massive project (maintenance for structural fatigue, environmental wear and tear, corrosion) are all prohibitive. There may be breakthroughs in materials in the coming years as nanomanufacturing allows us to produce materials near their theoretical strengths that could change this dynamic.

mass drivers; I'm not sure. I remember reading a proposal for building one on the moon at one point. It didn't seem to have nearly as many problems as the elevator, with current technologies.

[Anonymous No.5765752]

>>5765239
I read somewhere long ago the idea of using nuclear bombs to propel ourselves forward in space.

[Anonymous No.5765765]

>>5765752
That's the Orion drive.
The same concept gave birth to the concept of the Casaba Howitzer.

See:
http://www.projectrho.com/public_html/rocket/spacegunconvent.php#id--Nukes_In_Space--Nuclear_Shaped_Charges

And:
http://www.projectrho.com/public_html/rocket/enginelist.php#id--Pulse--Orion

[Nuka-Cola; Alpha Apple No.5767263]

concerns about losing your fuel in a rocket accident and it spreading all over.

which is kind of unfounded, if it's atomized that stuff with spread basically everywhere.
and of course you'd be firing the actual fuel up on its OWN rocket in a VERY WELL SHIELDED re-entry pod that can survive a catastrophic rocket failure.
and once it's in space, the reactor needs to be very well shielded as well as detachable for exactly these reasons.

even if you have one incident every 5 years of a couple pounds of MOX burning up in the atmosphere, the radioactive hazard would be basically undetectable, there's just too much atmosphere

[Anonymous No.5767325]

>>5767263
we all know that even trace amounts of nuclear material in the air will eventually kill off all life in earth and mutate all the rest.

[Anonymous No.5767327]

>>5767325
Mutate, don't you mean "makes all the insects grow twenty meters tall"?

[Anonymous No.5767352]

>>5765259
And hippy liberal faggotry.

[Anonymous No.5769525]

Holy hell, I visit Atomic Rockets all the time. Is it possible that Winchell Chung browses /sci/?