Plasma Rockets - Where do you stand on this topic?

Josh33086 · 2002-02-01 10:19:24

I am very pleased with the input that has been recived on this issue. This technology is the future of space travel. With the new NASA administration this will not get the attention it needs and deserves. I would like to know what you think should be done

Phobos · 2002-02-01 19:23:10

It'd be nice to see NASA or somebody else try to seriously attempt to develop some of the more technologically exotic ideas floating around. I think the reason a lot of people, including a number of spaceflight enthusiasts, find the International Space Station such a boring waste of time and money is because it just has that "been there, done that" feel to it. I'd whole heartedly support taking the money that goes into dubious projects like the space station and instead use it to do heavy research and development on technology and science that pushes the envelope. Either that or we can just take about 2/3 of the Pentagon's budget and fund such projects with that instead.

nebula · 2002-02-10 15:46:16

I like the idea of plasma rockets but I would like more R&D on nuclear propulsion first.

Shaun Barrett · 2002-02-11 00:03:17

I like the idea of nuclear rockets if they are going to produce the goods and get us to Mars in, say, 4 to 6 weeks instead of 6 to 8 months. Especially if disposal of spent nuclear fuel is going to be safe and easy.
Has anybody heard any more about that Israeli scientist's Americium-powered nuclear rocket engine? Apparently you can sustain fission in even thin sheets of Americium, which means you just pump propellant straight between the sheets of Americium which heat it up to very high temperatures on its way to the exhaust nozzle. Very simple and efficient. And I think the one-way time to Mars was supposed to be reduced to about a month with such an engine.
Imagine the savings in consumables alone(!), and you could possibly ignore the zero-g problems too with such brief transit times.
I'm not sure about the relative merits of thermal nuclear versus plasma engines. Does anyone have projected figures for the journey time to Mars with the various types of motor? Because time is really what counts in the end, isn't it?

Zak Tolley · 2002-02-21 11:17:39

Josh, it looks like you are going to get your wish, in this years budget NASA is reviving their nuclear propolsion program. I've only heard bits and peices about it, but from what I have heard they are focousing on reactors to power various types of electric propolsion ie; Ion engines, plasma engines, things of that nature.

Shaun Barrett · 2002-02-24 01:36:30

Funny how things change, isn't it? For years nobody dared bring up the subject of nuclear powered spacecraft .... remember all the fuss over Cassini with its RTG?
Now, after 9/11, the Bush administration and NASA are happy to announce they're pushing ahead with nuclear rockets in space and nobody even blinks! Has anyone noticed any press campaigns against it? Where are all the "greenies"?
Not that I'm against nuclear power in space .... best place for it, probably. (If disposed of properly, the waste certainly won't be contaminating good old Mother Earth.)
But in spite of all the good it will do the exploratory side of space utilisation, you don't have to be a genius to see why President Bush & Co. are so keen all of a sudden: Nuclear reactors in orbit around Earth can be used to power all those neat toys the military has been writing to Santa about for years! Imagine lasers and particle-beam weapons in orbit with almost unlimited power on tap from a high-output atomic reactor. They must have to place "Caution Wet Floor" signs all over the Pentagon because of the drooling! And in the aftermath of the terrorist attacks on American soil, there is little danger of any serious opposition from environmentalists or those against the proliferation of weapons in space.
Still, if you look at China's recent pronouncements on their future in space, it looks like they're serious about establishing a permanent place for themselves among the space-faring nations. And I don't believe they're doing it for the greater good of humanity either! If there are going to be orbiting nuclear weapons of whatever type, I'd sooner they have the Stars and Stripes painted on them than the flag of either China or the Russian Federation!
So, for whatever reason, let's go ahead and harness the enormous power of the atom to help us advance the exploration of the solar system. We can't go on relying on chemical rockets which are obviously not up to the job.
Maybe, as a much-needed offshoot of all this, we'll end up with the means to defend ourselves against the asteroid threat; a real-life "Spaceguard" as envisaged by Sir Arthur C. Clarke (and others).
Would this view of mine be representative of all or most of the Mars Society? Or are there members who really don't want to see nuclear power in space? If not, why not?
Over to you!

RobHazlewood · 2002-03-20 01:40:07

I am completely in favour of Nuclear Propulsion, and think it should be invested in heavily by NASA and ESA. In the long term, they would get a large return from their investment.

What sort of force can these things produce? (N/kg) where the mass takes into account propellant (& storage) and engine.

Also, how would the fissionable materials be transported into orbit? The thought of transporting enough fissionable material to orbit in order to get a manned spacecraft to mars in 1 month makes me kinda nurvous.

I'm okay with fission power for small probes where an exploding rocket would produce little consequences, but a worldwide contamination of this stuff doesn't sound too fun to me.

By the way, I am a "greeny" (member of the Australian Greens political party). I am also pro nuclear fission for science. NOT for everyday power generation. The costs and risks are too high.

thankyou,
Rob

Shaun Barrett · 2002-03-21 21:18:27

I don't have any actual figures on the thrust of nuclear rocket engines, but I do remember reading somewhere that a nuclear thermal rocket engine produces about twice the specific impulse of the best chemical engines. I believe this ratio is gleaned from research done in the 60s and 70s for the NERVA project. Apparently they actually produced a thrust of about 250,000 lbs with one of their experimental prototype engines.
Changing the subject to the practicalities of transporting fissile material into space; it really isn't quite as daunting as it sounds. A nuclear engine could be placed in orbit without any fuel and the fuel rods transported separately, in small numbers, and in armoured canisters capable of withstanding explosions or the heat of reentry. Once all the fuel rods are assembled in one place in orbit, they can be loaded into the waiting engine by astronauts. There would never be more than a very small quantity of radioactive fissile material in any one launch vehicle, and it would be sufficiently well packaged to survive any launch mishap. The nuclear rocket itself would only ever be used outside Earth's atmosphere, so the radioactive exhaust would never be an environmental problem.
Really, there is no rational reason why we should not take advantage of nuclear power in space. We can build an engine of almost any power we wish in complete safety.
One more point I'd like to make relates to the Greenies' impression of the dangers of nuclear energy production. The number of people who have died since the advent of fossil-fuel use is very large. Think of all the coal-mining, oil-drilling, transportation, pipeline construction etc.; now think of all the accidents that have occurred in these endeavours over the past two centuries. Now think of all the bronchial diseases and cancers that have resulted from breathing the airborne pollutants produced by the burning of these fuels. Even allowing for the relatively short time that nuclear energy has been used, the death-toll from fossil fuel use vastly outweighs that associated with nuclear fuel use.
I know the Greenies want only clean energy production and therefore support neither fossil fuel energy nor nuclear energy production. But their passionate opposition to nuclear power seems out of proportion to the actual risks involved. Until such time as we can rely totally on renewable energy from the sun, wind, tides etc., I think we should be less emotional about our alternatives. If the choice is between a coal- burning power station and a nuclear plant, we are probably better off with the latter.
There! ... I said it! Hope I haven't opened up one of those proverbial cans of worms here! I only advocate reasoned discussion ... that's all.

RobHazlewood · 2002-03-22 04:50:57

I'll openly admit that the chance of something going wrong with a fission power plant is very low, but accidents have happened in the past. What is to say they won't happen again in the future?

And what do you do with the waste? Shove it underground in concrete bunkers for 10,000 years. Geez.. that sounds safe.

I know a concreter. Once one of his customers asked if any guarantee came with a job he just did. He replied "I guarantee it will crack".

Would a concrete bunker be any different? Its no driveway, but surely it will develop cracks over the period of time it must be kept in storage. Then what? It may leak into underground water resivors contaminating large ammounts of water.

Coal power is terrible, too. It is also very expensive. (although I might get shot for saying that where I live.. 15kms away from the largest coal shipping port in the world)

I know this may make me sound like a far left idealist greeny, but wind electrical power is actually cheaper to produce than power from nuclear and coal power.

When I use the term 'nuclear', I really mean 'nuclear fission'. I am an advocate of nuclear fission power.

Nuclear Fission plants may also be a target for terrorism. Most nuclear plants cant withstand the force of being hit with a 747. The ones that could would probably not be able to withstand being hit by an airbus A380!

Back to science...

Fission rockets do sound like a really good idea. The one that I have heard discussed alot recently involves your usual nuclear thermal rocket type approach. Wouldn't a nuclear powered ion or plasma engine be much more efficient, allowing a probe to orbit and map every planet in the solar system before returning back to earth for examination?

Is Ion and Plasma propulsion unfeasible for manned craft due to the small force created by the engines?

thanks,
Rob

just a last passing thought.. To settle our disagreement about power generation, lets just aggree on spaced based solar power stations

Aaron Chester · 2002-03-22 06:44:49

I hate to provoke you further Rob. But, "green" power generation is at the moment too expensive. You make a good point that wind power is cheaper. However, I think you fail to take into consideration the infrastructure required. Not to mention the maintenance for that infrastructure. Solar power has the same problems. For the time being, nuclear power generation is the way to go if we want to reach Mars in the next 10-20 years.

What about the possibility of using nuclear power plants to fuel engines that propel probes to Mars? Then, once we reach Mars retrieve the power plants and use them to power the station. We would be killing two birds with one stone. The only problem that I foresee is protecting the nuclear power plant at impact. This problem might be the deal breaker for this idea. And, maybe only certain types of probes that have a slower descent rate could use this type of engine?

RobHazlewood · 2002-03-22 21:53:31

I know this is still off the topic, but the argument that was made about the cost of nuclear power generation being cheaper is false.

"This makes nuclear power very expensive. It is estimated that it will cost 3.0 to 4.5 pence per kilowatt-hour by 2020, compared with 1.5 to 2.4 p/kWh for onshore wind power. Combined heat and power comes in at 1.6 to 2.4 p/kWh and gas-fired generation at 1.8 to 2.1 p/kWh. "Nowhere in the world have new nuclear stations yet been financed within a liberalised electricity market," the report points out.
"
-New Scientist 15 Dec 01

It was an article discusussing a leaked british government review. I have not taken the quote out of context, either. The costs include insurance and disposal of radioactive waste.

thanks,
Rob

RobHazlewood · 2002-03-22 21:59:53

One other thing I forgot to point out.. what does electricity generation on earth have to do with getting to mars? H-H Fusion is probably the best option for use on mars. But i'll admit that it is unrealistic and Fission is the best electrical source for mars.

My point is that earth is a different case.

-Rob

Shaun Barrett · 2002-03-23 02:19:37

I wasn't sure whether or not to continue this line of argument since it seems a bit off-topic. But then I thought about nuclear waste disposal on Mars in the future, so discussing nuclear waste management does have relevance to Mars exploration ("Contrived logic!", I hear you all cry!!)
As I understand it, Rob, the plan with "hot" waste is to first powder it and then mix it into liquid glass; making chemically very stable glass "bricks". Then you locate a continental plate which is stable over geological ages, drill a hole some metres across and maybe a kilometre deep (straight down into solid bedrock) and then begin burying the bricks. The bottom of the shaft is first lined with 2 or 3 metres of reinforced concrete, then a stack of bricks, then more reinforced concrete, then more bricks, then more concrete, etc. etc. The last few hundred metres of the shaft are then filled in with yet more concrete; forming an impregnable plug.
There are regions of Earth's continental plates (e.g. in Greenland, Canada, and Australia) which have been largely undisturbed by volcanic or tectonic activity for periods of maybe 2 to 3 billion years. The radioactive half-lives of fission products are typically many orders of magnitude shorter than this.
In other words, if you have half a brain, you should be able to find any number of places on Earth (and more so on Mars which probably has less vulcanism and no discernible tectonic activity) where you could safely bury nuclear waste for many many times the prospective life-span of the human species. Obviously there will be costs associated with this deep burial but we are good at drilling holes and I don't see these costs as being prohibitive.
As for all these cowboy politicians stirring up irrational fears in their electorates any time somebody suggests a nuclear waste repository in their State, it makes me despair of humanity's common sense! These same people probably have more radiation in their homes from naturally occurring radon gas percolating up from the rock under their cellars than you would ever get out of a properly constructed nuclear waste repository!
I regret, Rob, that I just have to agree to disagree with you about nuclear power. A properly conducted nuclear power industry IS an environmentally sound option; most of the opposition to it is just pure emotion. (No offence intended.)

RobHazlewood · 2002-03-24 01:50:00

There is alot of GM emotion going around it at the moment. If someone presented me with a cupboard full of GM products, I wouldn't hestitate to eat it. (provided it is considered suitable for human consumption)

Going back to my previous comment, your way of getting rid of the waste sounds rather expensive to me.

What about Chernobyl? (I know that also creates alot of emotion. But that emotion is created with good cause)

Sure, a properly run nuclear industry IS safe. But what about the other factors that should be taken into account. I don't like the idea of private industry controlling nuclear plants. They would take shortcuts. Even a government run plant would take shortcuts. Anyone living in a country with a conservative government would not be able to deny this.

Forgetting everything except price, Wind still comes out on top.

*end of nuclear discussion*

-Rob

Shaun Barrett · 2002-03-25 05:44:26

Thankyou Rob for this interesting discussion. You have raised many good points and I do respect your opinions on power generation.
And you are quite right that it's probably time to move on! I look forward to hearing more from you soon.
Shaun

Austin Stanley · 2002-03-25 20:15:52

About transporting nuclear fuel into space, the Mars program wouldn't be the first, IIRC the USSR used to have spy-satilites powered by nuclear reactors (not a RTR) as well. One in fact de-orbited (AKA crashed), over Northern Canada, although the actual amount of radioactive polution was negligable.

-off the topic-

Breeding reactors can make use of most of the so called "nuclear waste," only the actual products of Fission deserve to be called waste, and there half-lifes are very short (less than 30 IIRC). Certianly the amount of waste is tiny compared to that of the other options, such as coal.

Austin Stanley · 2002-03-25 20:16:24

About transporting nuclear fuel into space, the Mars program wouldn't be the first, IIRC the USSR used to have spy-satilites powered by nuclear reactors (not a RTG) as well. One in fact de-orbited (AKA crashed), over Northern Canada, although the actual amount of radioactive polution was negligable.

-off the topic-

Breeding reactors can make use of most of the so called "nuclear waste," only the actual products of Fission deserve to be called waste, and there half-lifes are very short (less than 30 IIRC). Certianly the amount of waste is tiny compared to that of the other options, such as coal.

thunder · 2002-04-10 06:17:39

SOmehow the conversation from plasma fusion to fission. I admit I'm a little uncomfortable about the use of fission in an area where humans are present (be it on the ground or a manned space ship). Current plasma research also produces a bit of radioactivity, but at least there is no worry of an uncontrolled reaction. The Princeton Plasma Physics Laboratory, funded by the US Department of Energy, is about 10 miles from my college. Two weeks ago, the Physics Club went for a little field trip over there and got the grand tour. The current plasma research is for a D-T reaction, combining Deuterium and Tritium (hydrogen 2 and hydrogen 3 if you will). They are researching this type of fusion because it is easier then the others. Deuterium and Helium 3 is a more efficient reaction, but requires a higher heat and Helium 3 isn't all that common here on Earth. There is, however, a nearly unlimmited supply of He3 located in lunar ore. A lunar proccessing plant could provide enough fuel for plasma rockets for centuries to come.

Mark S · 2002-04-16 14:05:09

I see nuclear fission power as the key to opening the space frontier. A nuclear reactor is much lighter and more reliable than a solar array of equivalent output. Launching one would not be a big problem, either. If the rocket exploded, the reactor would be vaporized and would not cause a nuclear explosion. Once in space, the reactor would be kept a safe distance from the crew, and the ship's fuel would insulate the crew from the radiation. One demonstration reactor for space nuclear power was as large as a trash can, and it would require someone hugging it for at least a year to absorb a cancer dose of radiation.

I cannot think of any serious proposal for Mars exploaration that have not used nuclear power in some form. Even the chemically-propelled Mars Direct uses a nuclear reactor to produce the fuel for the earth return vehicle.

C M Edwards · 2002-04-29 15:30:55

Hello All.

I should note that VASIMR and some other plasma rocket engines are so much more efficient than chemical rocket engines that if you had the fuel to run a chemical rocket engine, you would be better off burning it in a generator to make electricity for a plasma rocket instead. That means that chemical power plants, though not as efficient as some other types, are also a possible alternative for powering interplanetary spacecraft.

The dry weight of a chemical power plant is less than that of either a solar power plant or nuclear plant of the same power output. Yes, nuclear plants produce a phenomenal amount of _energy_ (kWh of electricity) over the course of their entire operating lifetimes, but they're often incapable of matching the _power_ (kW, no hours) output of a chemical plant of the same dry mass. That's because of a chemical plant's primary advantage over nuclear power plants: a chemical plant doesn't have to be in one piece at the end of the day. You can run it until it just melts.

True, there are spacecraft nuclear power plants on the drawing boards that can get us from Earth orbit to Mars in months. But if you decide to do without that advantage, there are still chemical plants that can get you there, using VASIMR, with a single space shuttle launch. The theoretical operating limit for a chemical plant could -- in theory -- allow for one capable of powering an SSTO plasma rocket from the Earth's surface (though you would have to rebuild it after the mission). Nuclear fission can't touch that, because a nuclear power plant weighs so much compared to its actual power output.

Thanks for your time.

CME

Canth · 2002-04-29 21:51:49

A chemical power supply is capable of producing more output per wieght over a very short period of time than a nuclear poerplant. However you have to run a plasma rocket for the whole trip not just the beggining. Chemical power is not a good method of powering a plasma rocket, you will get more power using a cemical rocket engine. The most effecient chemical power options currently in use are hydrogen oxygen fuel cells, beleive me a hydrogen oxygen rocket engine is going to produce a #### of a lot more thrust than running a plasma engine off of fuel cell power.
A solar thermal rocket is a viable alternative to nuclear, chemical, or plasma engines. Basicaly it uses large reflectors to heat a fuel and spew it out the back. It could use any number of liquid or gaseous fuels the best being hydrogen. It could also be refueled with carbon dioxide ( or any other available liquid or gas) which you can pull right out of the martian air. The biggest problems would be folding and unfolding the reflectors (if you want maximum efficiency) and getting all that carbon dioxide to the viehicle (you would need a larger return rocket to get the fuel to the ship)
Solar sails also show much promise as a propulsion metod. (again much of the problem is in getting it unfolded without ripping the huge sail)

C M Edwards · 2002-04-30 07:02:13

Hello Canth.

Indeed, given a plasma rocket engine of some thrust, you can always build a chemical rocket engine that's capable of more thrust, and for less mass, too. However, rocket thrust is not rocket efficiency. Plasma rockets get more final kinetic energy out of the potential energy in their fuel/power plant than standard chemical rockets do. That doesn't mean chemical power plants are shining examples of efficiency. It only means that a chemical power plant plus a plasma rocket is more efficient than just a chemical rocket. Sufficiently so to, say, squeeze each of the NASA Mars Reference Mission modules into a set of single launches without further assembly required.

As for thermal rockets, it's interesting to note that the whole "has to be in one piece at the end of the day" limitation applies to them, too. If a H2/O2 rocket spews water exhaust at 4500K and a water-fuelled thermal rocket can only operate at 2800K without disintegrating, the hotter one wins. A thermal rocket using any propellant with a molecular weight heavier than methane can't exceed the performance of a chemical rocket, and methane's only good because modest temperatures will crack it to make hydrogen.

Plasma rockets are definitely the way to go, IMHO, even if you have to strap a diesel on them.

I can't wait for the first tractor pull in space.

CME

Canth · 2002-04-30 21:06:46

Plasma rockets are fuel efficient, however you must add to the wieght of every bit of fuel they use (such as xenon) the weight of the chemical fuel needed to accelerate it. Fuel cells produce energy maybe a bit more effeciently than a rocket engine but power is also lost in moving it around. Anyway it is certainly better to beam power via mirowaves to an ascending plasma rocket rather than degrade its preformance with heavy chemical fuels. I beleive that there has actually been a satilite power beaming system emplaced at some point, power via satilite from alaska to africa or something. It is inefficient for power transmission on earths surface it is cheaper to just build a straight power line or move the fuel, it is very effecient for a rocket however because of the immense cost of lugging fuel. Once in space a plasma rocket could be solar powered thus eliminating the need for chemical fuel. If your going to build a plasma rocket chemical power generating fuel on a large scale is not worth your while, as it removes one of the best feature of the system, the low fuel requirement.

C M Edwards · 2002-05-01 07:06:30

Hello Canth.

Indeed, if a better generating system is in place to produce electrical energy (or just heat) for a plasma rocket once it's in orbit, one should use that. However, I don't see any Mars-Transit rated microwave beam stations around anywhere. (A pity, because the lightcraft method of propulsion is _very_ cool.)

In lieu of anything better, we're pretty much stuck with solar, nuclear, and chemical power.

Sigh.

Fortunately, I don't think we have to chose just one. Each has its own unique performance characteristics, and we benefit by being able to pick and chose between them for each mission. And we're GOING to have more than one mission.

CME

GOM · 2002-05-01 11:21:14

And we're GOING to have more than one mission.
CME

Well....

Do you know something the rest of us don't?

I would certainly hope we would have more than one mission to Mars. However, I'm not sure it's ever going to happen.

Right now I'd be more than happy just to have ONE real manned Mars mission.

Shoot. I've even volunteered to go! And I don't care if they can't get me back to Earth. All I want is a promise that they will get me to Mars alive. There are some things over there that really need to be investigated.

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