Thread: Nuclear spaceship : possible?

Forgive me if I am posting this in the wrong section of the forum.
I've heard that an ordinary nuclear reactor can power a city for 2 years without requiring new radioactive material to be added to it.
So I'm thinking, is a nuclear spaceship possible? Uranium is one of the most abundant metals in the world. A normal reactor uses 35 kg/day, and produces 12.2 billion kilowatt-hours for that price, which seems very efficient.
So if we could make use of uranium to power a spacecraft, it would be really nice.
I have two theories of mine about how such a system could work.
1. Electrolysis of water : We could fill the fuel tank of a space ship with water and KOH, and it would keep producing an explosive gas, which could then be expelled out of the ship along with blasts, which could theoretically propel it, atleast when in Earth, as I dont know if such a system would work in the microgravity and vacuum environment of space. We could use a nuclear reactor to make the electricity for the electrolysis.
2. Since we have billions of kWh, we could maybe build a special kind of tesla coil which expels electricity in the same way as a shuttle does fire, and use that to propel.
So would any of this be practically possible?

Absolutely. Or even an alternate design- check out the Orion Spaceship.

Look, too, at the international arms treaty that banned the use of nuclear in space...


Hmmm...

Stupid humans...

Why would you use electrolysis of hydogen id use ion thrusters

This idea goes back to the 1950s. I think the main reason it didn't pan out was fear of having a nuclear reactor crash somewhere on earth.

NERVA (Nuclear Engine for Rocket Vehicle Application)

Westinghouse Astronuclear Laboratory - Wikipedia, the free encyclopedia

http://www.personal.psu.edu/djm5200/NERVA.html

Originally Posted by fiveworlds

Why would you use electrolysis of hydogen id use ion thrusters

That is not nuclear power, fiveworlds.


Sigh...

Originally Posted by fiveworlds

Why would you use electrolysis of hydogen id use ion thrusters

You still need something to ionize, and hydrogen is easiest to ionize. If your ship is manned, you're going to need the water and the oxygen anyways.

Originally Posted by AlexG

Originally Posted by fiveworlds

Why would you use electrolysis of hydogen id use ion thrusters

You still need something to ionize, and hydrogen is easiest to ionize. If your ship is manned, you're going to need the water and the oxygen anyways.

Ok.. clue my dumb@$$ in; what did I miss there?
Electrolysis of hydrogen is not a nuclear reaction.

Correct but ion thrusters NASA - Ion Propulsion use electricity nuclear reactors create electricity. Of course you could also use solar etc.

Originally Posted by Neverfly

Originally Posted by fiveworlds

Why would you use electrolysis of hydogen id use ion thrusters

That is not nuclear power, fiveworlds.


Sigh...

You could use the reactor to supply power for the ship. NASA uses plutonium-238 to power it probes.

Wow, I really am stupid. I didn't think of that, at all... Of course they use decay as an energy source for probes far from the Sun.
I really should refrain from posting in this thread for a while and go see about a strawberry flavored foot wash.

Nuclear thermal rockets have impressive performance potential but the risks seem to be higher than the public is willing to accept. Chemical rockets blow up with alarming regularity, is there really a lot of reason to believe nuclear rockets would be more reliable? Several tons of enriched uranium or plutonium being scattered across the landscape would be the result, a disaster potentially rivaling Chernobyl.

An Orion type spacecraft seems to be quite workable from an engineering standpoint, but even I, a lifetime nuclear advocate, quail at the thought of deliberately setting off nuclear warheads as a form of spacedrive, particularly anywhere near the earth.

Nuclear ion drives have potential, and seem to be less resisted by the public so long as they are activated a good distance away from the earth's surface. But there doesn't seem to be a lot of advantage over solar powered ion drives, which don't have all the political baggage associated with nuclear power.

To me the most urgent need of the world's space industry is to find a technology that substantially reduces the cost of getting payload into orbit. The preferred low cost solution today is the single use chemical rocket booster, a technology that has not changed much since the 1960s. Nuclear powered rockets do have the theoretical potential to lower those costs, but getting the public to accept using such rockets in the earth's atmosphere seems like a political near-impossibility.

Ehm, yeah, what do you think the Curiosity and the Voyagers work on?

Still, you'd need a way to propel yourself. This is, theoretically, possible by the emittance off light. So yeah, you could make a space-ship that flies without a propellant. But it wouldn't be much better then a solar-sail ship.

I am very sorry for the late response.
The orion spaceship uses nuclear blasts, I am thinking about harnessing nuclear energy in some other way.
The international arms treaty is for interplanetary wars, right?
Ion thrusters take years to develop enough thrust to lift a rocket.
We could coat the reactor in something anti-radioactive?
Politics stopping innovation again :/

Originally Posted by dhamaniasad

Ion thrusters take years to develop enough thrust to lift a rocket.

Ion thrusters are not capable of getting anything off the planet. But once you are off the planet and pointed it the right direction, they add a constant small acceleration that will cut our travel time around the solar system by quite a bit. I would say that the more powerful you can make those ion engines the faster we will get things done within our solar system.

However getting off the planet will be a problem for some time to come. I'd bet on a space elevator, before I'd think of trying nuclear blasting to get off planet.

I don't think we'll go very far with nuclear power spaceships. Nuclear reactors are heavy, big and dangerous, specially in a spaceship.

NASA currently uses nuclear power to provide electricity for it's satellites. They're not that big and bulky.

nice! i'll go check that out rigth now. maybe i'm a little out of date...

Originally Posted by snak

I don't think we'll go very far with nuclear power spaceships. Nuclear reactors are heavy, big and dangerous, specially in a spaceship.

Is there anything about being in a spaceship that isn't dangerous? Anyway, we do have an example of nuclear power being used in small inclosed spaces (Submarines). They have a remarkably good safety track record.

However, like you I don't see nuclear spaceships being used for more than a few years in any event. I'm hoping for fusion power or anti-matter powered spaceships to do anything really useful, but to keep moving forward you have to use the best available tech at the time.

Ps - Welcome to the forum

Originally Posted by AlexG

NASA currently uses nuclear power to provide electricity for it's satellites. They're not that big and bulky.

Providing electricity is different that providing thrust to leave the atmosphere. The nuclear reactor in a ship can only provide electricity so we would need an additional engine that uses electricity to provide thrust and I can't think of any engine that runs on electricity and provides enough thrust to leave the atmosphere.
Of course there's also the disadvantage of the combustion engine used in the spaceships: the ship has to carry it's own huge fuel tank which is very heavy and without it making spaceships would be much cheaper.

Originally Posted by Bad Robot

Originally Posted by snak

I don't think we'll go very far with nuclear power spaceships. Nuclear reactors are heavy, big and dangerous, specially in a spaceship.

Is there anything about being in a spaceship that isn't dangerous? Anyway, we do have an example of nuclear power being used in small inclosed spaces (Submarines). They have a remarkably good safety track record.

However, like you I don't see nuclear spaceships being used for more than a few years in any event. I'm hoping for fusion power or anti-matter powered spaceships to do anything really useful, but to keep moving forward you have to use the best available tech at the time.

Ps - Welcome to the forum

In a submarine there are no tremendous vibrations at launch and there is no worry with the weigh of the submarine cause the impulsion force in the water makes it lighter.
I'm just wondering how we could launch a spaceship with nuclear fission or fusion or antimatter power? Where does the thrust come from? Maybe someone will figure out a genius way of making a engine that runs on electricity and provides enough thrust to leave the atmosphere.

And also here's a great vid where theoretical physicist Michio Kaku speaks around this theme: Michio Kaku: Why We Can't "Fire the Photon Torpedoes" - YouTube

Originally Posted by dhamaniasad

Forgive me if I am posting this in the wrong section of the forum.
I've heard that an ordinary nuclear reactor can power a city for 2 years without requiring new radioactive material to be added to it.
So I'm thinking, is a nuclear spaceship possible? Uranium is one of the most abundant metals in the world. A normal reactor uses 35 kg/day, and produces 12.2 billion kilowatt-hours for that price, which seems very efficient.
So if we could make use of uranium to power a spacecraft, it would be really nice.
I have two theories of mine about how such a system could work.
1. Electrolysis of water : We could fill the fuel tank of a space ship with water and KOH, and it would keep producing an explosive gas, which could then be expelled out of the ship along with blasts, which could theoretically propel it, atleast when in Earth, as I dont know if such a system would work in the microgravity and vacuum environment of space. We could use a nuclear reactor to make the electricity for the electrolysis.
2. Since we have billions of kWh, we could maybe build a special kind of tesla coil which expels electricity in the same way as a shuttle does fire, and use that to propel.
So would any of this be practically possible?

I think the guy is on to something because I have the same idea he does, basically.
You could build the ship piece by piece and send it up into space to be assembled on a space station.
1.It would need a stable, safe, shielded nuclear reactor to make electricity.
2.There would need to be a large storage tank for lots of H2O
3.Electrical current running through water makes hydrogen and oxygen molecules (electrolysis). You can speed the process up by finding the right catalyst, electrolytes to use, and temperature.
4.The hydrogen and oxygen would need to be sucked out and separated somehow and put into storage tanks.
5. The hydrogen and oxygen would need to be cooled down with a freezer so that they are in liquid form and are better rocket propellants.
6. The liquid hydrogen and oxygen could be pumped out of thrusters of the ship and ignited with an electric spark.
7. If there was enough water on board the ship could accelerate at 9.8m/s/s which is 1 G. Earth's gravity. If it kept accelerating at this rate it would reach the speed of light in less than a year.
8.If the ship accelerated at 9.8m/s/s this would mimic earth's gravity inside the ship, but the thing is the fake gravity would pull everything toward the butt or bottom end of the ship.
9. So the ship would have to be designed so that the thrusters would be the bottom or the fake surface of the earth and the head of the ship would be like the top of a tower or high rise, so you would have to climb ladders or stairs to get to the top where the control room would be. Provided that the ship was accelerating at 9.8m/s/s.

Something like this:
ship:
fake top of tower: things will fall down toward the bottom
^ head of ship or control room
9 computer and navigation compartment
8 living compartment
7 gym and movie theater
6 ecosystem compartment
5 labritory compartment
4 storage and chemical storage
3 water storage compartment (needs to be huge)
2 nuclear reactor compartment (lined with lead at top)
1 refrigerator liquid propellant compartment
^ bottom of ship(thrusters)
fake bottom of the tower or surface of the earth

To make something like this possible that space nuclear treaty would have to be renegotiated, and the U.N. would have to get involved. If it were a joint operation where a lot of countries participated then other nations would be willing to participate and make it possible because it would make them look good to their people too. If something bad does happen and the reactor crashes to Earth and it wasn't turned on yet, it will most likely land in the ocean and no radiation will seep out. But say the reactor was turned on and was melting down and it fell to Earth, again it would most likely land in the ocean and the radiation would be dissipated and diluted by the ocean. But if it landed on land it wouldn't be as bad as Chernobyl, but it would be like a really small nuke going off. It could be bad, but a lot of things would have to go wrong before that happened. Only a real cluster fudge or meteorite could cause something like this to happen. But the reactor shouldn't be turned on until the end of production...maybe do a test run, but then shut it down until final assembly.

But then again I may be completely full of monkey poo and this may never happen. I know with complete certainty that I am at least partially full of monkey poo because I'm not a scientist...I've just been Googling and Binking these ideas out. I’ve been working out the math and am still working on ideas. I will give you links and citations if you're interested.

relativistically speaking, you can get close to light speed, but matter can never travel at light speed. Important distinction.

In terms of the thrust necessary to propel an object with an acceleration of is quite high. Assuming you're already in space, for a spacecraft with a payload of, say 10000kg, about 11 tons, very light for any kind of manned spacecraft, you would have to apply a constant force of 98,000N. Let's say we want to speed this payload up to 10% light speed, seems like a small number, but bear with me. For this, we won't consider relativity at all, and will treat this under Newtonian gravity alone. So, at it would take 3059107 seconds, or 35.4 days, to achieve .1c. That means that the spaceship will travel 9358135637449m before reaching that speed. That's 917,097,292,470,002 Joules of energy. It would take 3206633889.755252 moles of hydrogen combusting to produce that much energy. The weight of propellant necessary, in hydrogen alone, is 3206633kg. This also doesn't take into account that a large amount of the fuel would have to also be included in the payload section, since unburnt fuel is also being accelerated long with the payload.

Sorry for bursting the monkey poo bubble

Originally Posted by Arcane_Mathematician

relativistically speaking, you can get close to light speed, but matter can never travel at light speed. Important distinction.

In terms of the thrust necessary to propel an object with an acceleration of is quite high. Assuming you're already in space, for a spacecraft with a payload of, say 10000kg, about 11 tons, very light for any kind of manned spacecraft, you would have to apply a constant force of 98,000N. Let's say we want to speed this payload up to 10% light speed, seems like a small number, but bear with me. For this, we won't consider relativity at all, and will treat this under Newtonian gravity alone. So, at it would take 3059107 seconds, or 35.4 days, to achieve .1c. That means that the spaceship will travel 9358135637449m before reaching that speed. That's 917,097,292,470,002 Joules of energy. It would take 3206633889.755252 moles of hydrogen combusting to produce that much energy. The weight of propellant necessary, in hydrogen alone, is 3206633kg. This also doesn't take into account that a large amount of the fuel would have to also be included in the payload section, since unburnt fuel is also being accelerated long with the payload.

Sorry for bursting the monkey poo bubble

It sounds like he wants a spaceship to move around the solar system with. But I still like ion engines better. You don't run out of fuel very fast and you still gain the speed you need to get around in a reasonable amount of time.

Originally Posted by Arcane_Mathematician

relativistically speaking, you can get close to light speed, but matter can never travel at light speed. Important distinction.

In terms of the thrust necessary to propel an object with an acceleration of is quite high. Assuming you're already in space, for a spacecraft with a payload of, say 10000kg, about 11 tons, very light for any kind of manned spacecraft, you would have to apply a constant force of 98,000N. Let's say we want to speed this payload up to 10% light speed, seems like a small number, but bear with me. For this, we won't consider relativity at all, and will treat this under Newtonian gravity alone. So, at it would take 3059107 seconds, or 35.4 days, to achieve .1c. That means that the spaceship will travel 9358135637449m before reaching that speed. That's 917,097,292,470,002 Joules of energy. It would take 3206633889.755252 moles of hydrogen combusting to produce that much energy. The weight of propellant necessary, in hydrogen alone, is 3206633kg. This also doesn't take into account that a large amount of the fuel would have to also be included in the payload section, since unburnt fuel is also being accelerated long with the payload.

Sorry for bursting the monkey poo bubble

It's a lot worse than even your post suggests. Let's consider what a typical chemical rocket can achieve. We are looking at an exhaust velocity of ~4500m/sec.

Now, if we take the rocket equation



Where Ve is the exhaust velocity and MR is the mass ratio (Fully fueled rocket/rocket after expending fuel)

Using 10000kg for our rocket mass and 3206633 for fuel mass, we can get how much delta v we can expect.

It works out to ~26 km/sec or only ~0.00009c

We can also rearrange it to solve for MR given any V_e and desired delta V.



Which means that to reach 0.1c with a chemical rocket you would need roughly

kg of fuel for every kg of rocket.

Originally Posted by Bad Robot

Originally Posted by snak

I don't think we'll go very far with nuclear power spaceships. Nuclear reactors are heavy, big and dangerous, specially in a spaceship.

Is there anything about being in a spaceship that isn't dangerous? Anyway, we do have an example of nuclear power being used in small inclosed spaces (Submarines). They have a remarkably good safety track record.

However, like you I don't see nuclear spaceships being used for more than a few years in any event. I'm hoping for fusion power or anti-matter powered spaceships to do anything really useful, but to keep moving forward you have to use the best available tech at the time.

Ps - Welcome to the forum

Mmmm yeh, I'm quite interested to see if we can the solve the big challenge of being able to produce anti-matter in a large enough quantity and low enough cost. Anti-matter spaceships will be awesome i'm also wondering if there will be secondary systems of solar power, as well as nano fabricated batteries capable of holding a large amount of energy, that is produced by nuclear fusion.

how many years is it now we were on moon? afcourse the are real possibilitys we got on mars too.... I think the problem lyes elswere

Originally Posted by Janus

Originally Posted by Arcane_Mathematician

relativistically speaking, you can get close to light speed, but matter can never travel at light speed. Important distinction. In terms of the thrust necessary to propel an object with an acceleration of is quite high. Assuming you're already in space, for a spacecraft with a payload of, say 10000kg, about 11 tons, very light for any kind of manned spacecraft, you would have to apply a constant force of 98,000N. Let's say we want to speed this payload up to 10% light speed, seems like a small number, but bear with me. For this, we won't consider relativity at all, and will treat this under Newtonian gravity alone. So, at it would take 3059107 seconds, or 35.4 days, to achieve .1c. That means that the spaceship will travel 9358135637449m before reaching that speed. That's 917,097,292,470,002 Joules of energy. It would take 3206633889.755252 moles of hydrogen combusting to produce that much energy. The weight of propellant necessary, in hydrogen alone, is 3206633kg. This also doesn't take into account that a large amount of the fuel would have to also be included in the payload section, since unburnt fuel is also being accelerated long with the payload.Sorry for bursting the monkey poo bubble

It's a lot worse than even your post suggests. Let's consider what a typical chemical rocket can achieve. We are looking at an exhaust velocity of ~4500m/sec. Now, if we take the rocket equationWhere Ve is the exhaust velocity and MR is the mass ratio (Fully fueled rocket/rocket after expending fuel)Using 10000kg for our rocket mass and 3206633 for fuel mass, we can get how much delta v we can expect. It works out to ~26 km/sec or only ~0.00009cWe can also rearrange it to solve for MR given any V_e and desired delta V. Which means that to reach 0.1c with a chemical rocket you would need roughly kg of fuel for every kg of rocket.

Heh, yeah, I knew it was somewhere ridiculously high.. Been a bit since I've done any of these kinds of calculations, so I've gotten quite rusty.. Feels good to be back exposed to all of this again though

How about a warm drive that warps space around it, to expand the space behind the space ship, and contract the space in front, to achieve faster than light travel? Any idea how to possibly warm space, and what sort of energy system might be required to achieve this?

I like an electricly powered rail gun to get things into orbit. The heavy generators etc stay on earth and only the payload is shot into orbit. the ship can be assembled in orbit but some serious number crunching is needed because I once attended a seminar, presented by a NASA scientist, where the amount of various fuels needed to get a payload the size of a compact car to the nearest stars, was explored. Even with nuclear energy the amount of fissionable material needed to produce the energy to go to a nearby star was prohibitive. The only fuel with sufficient "bag for the buck" was antimatter.

Originally Posted by Curiosity

How about a warm drive that warps space around it, to expand the space behind the space ship, and contract the space in front, to achieve faster than light travel? Any idea how to possibly warm space, and what sort of energy system might be required to achieve this?

I am guessing that you propose heating the area behind the space ship and cooling the area in front of it so that the expanding warm area pushes the space ship toward teh cool contracted area infront of the ship? What a brilliant notion Clearly you should win some sort of award but I am a loss to decide which one.

I remember reading how it's been proven that the concept doesn't defy any known laws of physics or relativity. I'm just wondering what possible force you'd need, to alter the shape of space-time.

Originally Posted by Arcane_Mathematician

relativistically speaking, you can get close to light speed, but matter can never travel at light speed. Important distinction.

In terms of the thrust necessary to propel an object with an acceleration of is quite high. Assuming you're already in space, for a spacecraft with a payload of, say 10000kg, about 11 tons, very light for any kind of manned spacecraft, you would have to apply a constant force of 98,000N. Let's say we want to speed this payload up to 10% light speed, seems like a small number, but bear with me. For this, we won't consider relativity at all, and will treat this under Newtonian gravity alone. So, at it would take 3059107 seconds, or 35.4 days, to achieve .1c. That means that the spaceship will travel 9358135637449m before reaching that speed. That's 917,097,292,470,002 Joules of energy. It would take 3206633889.755252 moles of hydrogen combusting to produce that much energy. The weight of propellant necessary, in hydrogen alone, is 3206633kg. This also doesn't take into account that a large amount of the fuel would have to also be included in the payload section, since unburnt fuel is also being accelerated long with the payload.

Sorry for bursting the monkey poo bubble

Yeah that's what I was going to work on next. So thank you for pointing that out. But it's not weight anymore, it's mass. Weight would imply gravity from the earth. The ship would be assembled in space and launched from space, but I will do the calculations for the ship with the same mass as a nuclear submarine.

HeyZeus, he's right this is going to be sky high. I'll get ideas from people that are smarter than me. I knew this idea had holes in it.

If an interplanetary craft could be built in orbit, would most of the weight to power ratio problems resolve themselves.

Originally Posted by Dirty_Mexican

Originally Posted by Arcane_Mathematician

relativistically speaking, you can get close to light speed, but matter can never travel at light speed. Important distinction.

In terms of the thrust necessary to propel an object with an acceleration of is quite high. Assuming you're already in space, for a spacecraft with a payload of, say 10000kg, about 11 tons, very light for any kind of manned spacecraft, you would have to apply a constant force of 98,000N. Let's say we want to speed this payload up to 10% light speed, seems like a small number, but bear with me. For this, we won't consider relativity at all, and will treat this under Newtonian gravity alone. So, at it would take 3059107 seconds, or 35.4 days, to achieve .1c. That means that the spaceship will travel 9358135637449m before reaching that speed. That's 917,097,292,470,002 Joules of energy. It would take 3206633889.755252 moles of hydrogen combusting to produce that much energy. The weight of propellant necessary, in hydrogen alone, is 3206633kg. This also doesn't take into account that a large amount of the fuel would have to also be included in the payload section, since unburnt fuel is also being accelerated long with the payload.

Sorry for bursting the monkey poo bubble

Yeah that's what I was going to work on next. So thank you for pointing that out. But it's not weight anymore, it's mass. Weight would imply gravity from the earth. The ship would be assembled in space and launched from space, but I will do the calculations for the ship with the same mass as a nuclear submarine.

yes, mass is the term I meant. Been a couple years since I was actively discussing these kinds of things.

Originally Posted by sculptor

If an interplanetary craft could be built in orbit, would most of the weight to power ratio problems resolve themselves.

Let's consider a craft making a flight from low Earth orbit to low Mars orbit.

First we need to consider the delta v needed to break orbit . This works to ~41% of orbital speed or 3205m/sec
Next we need to enter into a transfer orbit from Earth to Mars, A minimum energy orbit would require ~2952m/sec
Then we need to match orbits with Mars, which requires ~2655m/sec
Finally we have to brake in order to settle into a low Mars orbit, which is another ~1409m/s

All together this works out to ~10221m/sec. With a conventional chemical rocket you would roughly need 9kg of fuel for every kg of ship.

That's assuming you don't have to carry fuel for the return trip. If you do, this jumps to about 93 kg of fuel per kg of ship.

This article might be of interest in this topic.

Faster-Than-Light Drive | Popular Science

Originally Posted by Janus

Originally Posted by sculptor

If an interplanetary craft could be built in orbit, would most of the weight to power ratio problems resolve themselves.

Let's consider a craft making a flight from low Earth orbit to low Mars orbit.

First we need to consider the delta v needed to break orbit . This works to ~41% of orbital speed or 3205m/sec
Next we need to enter into a transfer orbit from Earth to Mars, A minimum energy orbit would require ~2952m/sec
Then we need to match orbits with Mars, which requires ~2655m/sec
Finally we have to brake in order to settle into a low Mars orbit, which is another ~1409m/s

All together this works out to ~10221m/sec. With a conventional chemical rocket you would roughly need 9kg of fuel for every kg of ship.

That's assuming you don't have to carry fuel for the return trip. If you do, this jumps to about 93 kg of fuel per kg of ship.

I think my original post was way over ambitious and impractical. You'd need way too much fuel which would drive up mass to constantly accelerate at 9.8m/s/s to mimic gravity. But, if we were to do interplanetary manned flights it would still be more practical to launch from space, we could accelerate and reach a descent velocity to get to Mars in a reasonable amount of time and we could do it with current technology or old 60's tech, like with R-1 rockets which use kerosine and liquid oxygen. It would just have to be a big enough ship with enough fuel and rocket boosters to get there and back. We could use old technology like our lunar landing craft to go out take samples and explore.

But if we go further and further out into space, I think a nuclear electrolysis ship would be practical. The thing is you could make pit stops along the way to get more water and keep moving along. U'd need something like a space shuttle to collect the water on the planet and bring it back up to the ship. Mars has frozen water. Jupiter has moons with water and so does Saturn. There's holes in this idea too because you would have to make it efficient to collect water on the planet whether you use a landing craft to collect the water or you could land the mother ship on the surface and collect it, but then it would have to escape the planet or moon's gravitational pull, which would waste precious fuel. Either way you'd be expending fuel to get fuel.

But what I'm getting at is using water as the fuel source would be great because you can find water all over the universe. But finding oil to make kerosine would be like finding a needle in a hay stack because oil can only come from ancient dead decayed organisms and it takes millions of years for it to form. Plus you'd have to drill or frack it. Then u'd have to process it into kerosine, gasoline, or jet fuel or what ever. We're talking about a refinery on a freaking space ship, not a small nuclear generator.

I haven't been able to work on the physics of this lately so I greatly appreciate anyone who posts calculations or ideas.

describe how you would use nuclear decay to propel a spaceship please

Originally Posted by Dirty_Mexican

Originally Posted by Janus

Originally Posted by sculptor

If an interplanetary craft could be built in orbit, would most of the weight to power ratio problems resolve themselves.

Let's consider a craft making a flight from low Earth orbit to low Mars orbit.

First we need to consider the delta v needed to break orbit . This works to ~41% of orbital speed or 3205m/sec
Next we need to enter into a transfer orbit from Earth to Mars, A minimum energy orbit would require ~2952m/sec
Then we need to match orbits with Mars, which requires ~2655m/sec
Finally we have to brake in order to settle into a low Mars orbit, which is another ~1409m/s

All together this works out to ~10221m/sec. With a conventional chemical rocket you would roughly need 9kg of fuel for every kg of ship.

That's assuming you don't have to carry fuel for the return trip. If you do, this jumps to about 93 kg of fuel per kg of ship.

I think my original post was way over ambitious and impractical. You'd need way too much fuel which would drive up mass to constantly accelerate at 9.8m/s/s to mimic gravity. But, if we were to do interplanetary manned flights it would still be more practical to launch from space, we could accelerate and reach a descent velocity to get to Mars in a reasonable amount of time and we could do it with current technology or old 60's tech, like with R-1 rockets which use kerosine and liquid oxygen. It would just have to be a big enough ship with enough fuel and rocket boosters to get there and back. We could use old technology like our lunar landing craft to go out take samples and explore.

The numbers given in my post are the bare minimum required for such a trip to Mars in terms of delta v. They are set by the rules of orbital mechanics. For instance, if you do not generate the 2952m/sec needed to make the transfer orbit, you won't get to Mars, your orbit will fall short of Mars' orbit and you start falling back in toward the Sun. The time for such a trip one way would be ~258 days

How much fuel is needed to achieve the required Dv depends on your exhaust velocity of your rocket.

The equation for determining this is



Delta v is the change in velocity and Ve the exhaust velocity of your rocket.

MR is the ratio of the mass of the fully fueled rocket to the mass of the rocket after expending its fuel.

For my calculations I used 4500m/s for the Ve (about what the best chemical rockets of the day can achieve)

The old R1 rockets got something in the order of 2000 m/s.

Using this value drives the fuel requirement up by a factor of ~18 for a one way trip and ~295 times for a round trip. In other words, for a round trip you would need over 27 metric tons of fuel for every 1 kg of empty rocket.

There are ways of reducing that number. Because of the exponential nature of the rocket equation, splitting the launch into multiple parts can help. Send a couple unmanned refueling rockets to Mars first so the manned rocket (which is heavier due to life support) doesn't need to carry the fuel to return itself. (Or, send an automated fuel manufacturing plant to Mars first.)

But yeah, for interplanetary travel, we really need to get the exhaust velocity up as that has the biggest, most direct impact on things. Of course, if it gets too high, you really wouldn't want to set it off on the ground, or even in the atmosphere.

Originally Posted by sculptor

describe how you would use nuclear decay to propel a spaceship please

Alpha emitter emits high energy alpha particles through an aperture. Reaction drives the ship the other way. By far the simplest nuclear rocket.

Originally Posted by MagiMaster

There are ways of reducing that number. Because of the exponential nature of the rocket equation, splitting the launch into multiple parts can help. Send a couple unmanned refueling rockets to Mars first so the manned rocket (which is heavier due to life support) doesn't need to carry the fuel to return itself. (Or, send an automated fuel manufacturing plant to Mars first.)

If you can send a fuel manufacturing plant ahead that would help, But sending the fuel ahead doesn't (At least in this scenario, I'll come back to when it would).

The fuel needed to send the return trip ahead is just as much as needed if you just sent it all together.

Look at it this way, It takes y amount of fuel to deliver x amount of payload to Mars, it doesn't matter if the the payload is fuel for the return trip or passengers. Sending the fuel ahead won't take less fuel than if you launched the fuel ships and main ship at the same time* and they traveled side by side, which is no different from them all being hooked together which is no different than it all being one ship. ( And sending them separately could end up in being more costly, considering that you will have to expend fuel in order to rendezvous with your fuel ships once you get there.)

* This is not taking into account the fact that the eccentricity of the planet orbits involved can vary both the travel times and Delta Vs for different launch windows but that gets more complicated than I want to go into here.

So here is where it makes sense to send the fuel ahead:

It's when you want or need to reduce the travel time for the main ship and it passengers to below that needed for the minimum energy trajectory.

So let's say that, in order to reduce exposure to solar flares for example, you need to shorten the trip time. Now you can do this by using something other than the minimum energy path, However, it will be much more costly in terms of delta V and mass ratio. So here's what you do, you send the fuel and supplies you need for the return trip and any equipment supplies you'll need while at Mars ( for instance, landing craft, base construction materials, etc.) ahead by the slow, low energy route, which uses a lower Delta V/mass ratio. This way you only have to expend the higher mass ratio on just what you need to get your crew to Mars by the faster route.

Oh yeah. That makes sense. (I guess I'd forgotten a few details from last time I read about this as that does sound kind of familiar now that you mention it. )

Originally Posted by AlexG

Originally Posted by fiveworlds

Why would you use electrolysis of hydogen id use ion thrusters

You still need something to ionize, and hydrogen is easiest to ionize. If your ship is manned, you're going to need the water and the oxygen anyways.

Ion Propulsion is not ideal for manned flights... You would die of old age before you got anywhere. Some form of sustained induced stasis would need to be in place, which would lead to less or even no usage of water or oxygen, which therefore concludes in full circle.

Originally Posted by Devon Keogh

Originally Posted by AlexG

Originally Posted by fiveworlds

Why would you use electrolysis of hydogen id use ion thrusters

You still need something to ionize, and hydrogen is easiest to ionize. If your ship is manned, you're going to need the water and the oxygen anyways.

Ion Propulsion is not ideal for manned flights... You would die of old age before you got anywhere. Some form of sustained induced stasis would need to be in place, which would lead to less or even no usage of water or oxygen, which therefore concludes in full circle.

What you say makes sense if you are traveling to other star systems, but not if you need to just move around our local solar system. Using any sustained propulsion is much better than what our current standard is now.

Originally Posted by billvon

Originally Posted by sculptor

describe how you would use nuclear decay to propel a spaceship please

Alpha emitter emits high energy alpha particles through an aperture. Reaction drives the ship the other way. By far the simplest nuclear rocket.

Thanx
Now, (pardon my ignorance): Could we derive a power to weight ratio that would propel the craft fast enough to use and then break free of the natural acceleration of a paraballic course past the sun and other planets.
Would that gain us a significant advantage?

time to heliopause?

The sun is not a very good object for slingshot because it sits too close to the solar system's barycenter. It's not all that difficult to escape the Sun's gravity ---our Voyager space craft have done that.

Does anybody know if you can make Tritium liquid or gas running current through it? Tritium is a hydrogen atom with 2 electrons right? So if you ran current through H2 liquid or gas (in a vacuum of course), could the electrons bind to the hydrogen atoms? U could still start out with Nuclear water electrolys and get ur O2 and H2 then maybe do what I asked about above and do an Orion style ship that uses the Tritium for shaped charged Nuclear Explosions for propulsion. I don't know, I'm just fishing for an idea.

Yeah, I better shut up because I don't want to figure out how to make tritium and post it on a forum where everybody including our enemies can see it. I'll think harder before I speak. I'm glad I'm wrong.

Originally Posted by Dirty_Mexican

Does anybody know if you can make Tritium liquid or gas running current through it? Tritium is a hydrogen atom with 2 electrons right? So if you ran current through H2 liquid or gas (in a vacuum of course), could the electrons bind to the hydrogen atoms? U could still start out with Nuclear water electrolys and get ur O2 and H2 then maybe do what I asked about above and do an Orion style ship that uses the Tritium for shaped charged Nuclear Explosions for propulsion. I don't know, I'm just fishing for an idea.

Tritium is not something that is easily made, but a very small percentage of hydrogen does form an isotope with 2 neutrons. They can then use it to make super heavy water which is radioactive. You wouldn't want to drink tritiated water or even just plain heavy water.

Tritiated water - Wikipedia, the free encyclopedia

Originally Posted by Bad Robot

Originally Posted by Devon Keogh

Originally Posted by AlexG

Originally Posted by fiveworlds

Why would you use electrolysis of hydogen id use ion thrusters

You still need something to ionize, and hydrogen is easiest to ionize. If your ship is manned, you're going to need the water and the oxygen anyways.

Ion Propulsion is not ideal for manned flights... You would die of old age before you got anywhere. Some form of sustained induced stasis would need to be in place, which would lead to less or even no usage of water or oxygen, which therefore concludes in full circle.

What you say makes sense if you are traveling to other star systems, but not if you need to just move around our local solar system. Using any sustained propulsion is much better than what our current standard is now.

Almost anything is better than the current standard, but Ion propulsion takes a very long time to accelerate, therefore you would need more than a few engines to power a manned spaceship. Remember that a manned spaceship is considerably more complex and therefore heavier than an unmanned probe.

Nuclear engines combat this by having a better acceleration than ion propulsion, and so are more suitable for inter-planetary missions. Ion being more suitable for inter-solar missions.