If they can reduce costs, and make it safe then god I hope they do this... this might actually lead towards space travel becoming more economically and commercially viable for the near future.

Reduced costs for getting payloads out into space means more money for developing other projects.

"One of the reasons the original NERVA was never used was that the hydrogen reaction mass became radioactive as it passed through the reactor"

Honest question: how does hydrogen become radioactive? What does it break down to?

Being realistic here, there are not many other serious contendors for interplanetary travel within a reasonably timeframe. When you take into account that interplanetary travel means your away from the safety of the Earth's magnetic field, being out in interplanetery space for any length of time is extremely hazardous and should be reduced if at all possible!

Ion drives and solar sails are very slow, chemical rockets require huge fuel reserves.

The nuclear alternatice, although undesirable in close proximity, is the only reasonable alternative within the bounds of current science theory. (Yes there are a few others like a mag-lev catapault etc, but they are not nearly as mature or as TESTED as nuclear).

Of course there are risks, but there are risks in everything. Look at the early colonisation of the America's and new diseases, look at the first sailors to venture beyond the ability to see land or the first transatlantic flights!

To live is to risk, yes this isn't just risking the lives of those going up there by those on the ground too, but this is where inteligent and transparent discussion should take place and the ideas should not be dismissed by the public/people because of the word 'nuclear' in it!

All science is advancement, its uses, for good or ill are determined by those who use it.

I'm hoping people will poke holes and retort because that challenges me to think and to elabroate on points! One should not accept things blindly, but too often people in general will do so, be swayed by the media and are not open minded at all (but those are topics for discussion elsewhere).

My guess is the exhaust gas of the NERVA included Tritium. This would occur if some of the Hydrogen molecules pick up two neutrons.

But it should not be a problem, because NERVA rockets were only intended to be used outside of the atmosphere.

Tritium decays into helium-3, which is not radioactive.

Hydrogen becomes radioactive because, when it passes through the nuclear reactor, it will inevitably suck up some neutrons. Part of the hydrogen will turn into (harmless) deuterium and some will turn into (radioactive) tritium. As a result, you get a radioactive mixture.

However, one thing we musn't forget is that we're currently researching nuclear fusion. While nuclear fission for now remains the way to go, in perhaps as little as 50 years, we might have a viable fusion reactor. Give it a few dozen years more for the technology to get miniaturized and we can throw fusion drives into orbit

...what I really, really want.

I want big-ass railguns that stretch many miles across the desert so they can accelerate slowly enough not to squish people into goo, then gently arc upwards along the side of a really tall mountain so the lateral forces don't squish people into goo, then launch spaceships through the atmosphere using momentum alone, so they don't need rockets that run the risk of exploding and thereby turning people into goo.

And I want this tomorrow. Thank you in advance.

fly me to the moon

gone fission on the way there

some won't like the catch

Nice just what the earth does not need , more industrial garbage and waste requiring a minimum of 240,000 years of storage , when the current ones are are already full to overflowing , and the planned future ones are already spoken for!

As for diseases , how do you think the unwanted colonial interlopers at Jamestown manage to eliminate the million to one local native superiority , but with germ warfare.

Sadly , since with the aid of the mass media reduced to printing mere government propaganda (oops , have we not forgotten the so called liquid explosive plot at Heathrow Airport? or a house destroyed for no valid reason by the police, with all the major press outlets merely replaying government fiction without question rhyme or reason?) the new age of the chicken little paranoia fear of the ever implausible what ifs that read like failed plot lines from the TV show called "Spooks" , the big clock will reach midnight faster than cheap low cost interplanetary space flight for all will occur !

But then again , NASA did build that white elephant that is called the space shuttle , and we all know how safe and reliable those units are?

Nice choices indeed!

The rocket is based on Newton's third law. Only due to the huge amount of exhaust gases that come out does the rocket go up. In space, propellers are useless because there is no air (or water as in submarines and ships) to push, thereby you cant apply newton's third law. Thats the reason rocket engines are used. Do nuclear reactions spew as much fumes as a rocket engine does?

I think they only produce heat (from which electricity is produced). You can only get electricity from nuclear reactions and can't use them for space travel.

Please correct me if I'm wrong.

I was wondering where El Reg go materials for those funky keyring glow lights. Surely a conflict of interest here.

Mine is still going strong enough afer however many years.

You mean a Mass Driver?

Didn't read the article completely.

you must have missed this part of the article Choundappan:

"...NERVA-type rockets use a fission reactor to heat up hydrogen and blast it out of the thrust nozzle at extremely high speed, faster than can be achieved by normal chemical-powered boosters..."

I think they only produce heat (from which electricity is produced). You can only get electricity from nuclear reactions and can't use them for space travel.

Please correct me if I'm wrong.

Since you asked, I will.

Rockets use Newton's second and third laws. A chemical reaction is used to create thrust which pushes against the rocket, not the surrounding air.

And while you are correct in that (some) nuclear reactions produce heat, there are two ways that a nuclear REACTOR can be used to produce useable thrust for space travel.

The first is a Nerva type engine. You use the reactor to produce heat, which is used to heat up a reaction mass and accelerate it out the end of the craft. This is where Newton's Second Law applies, F=ma= thrust.

The second is to have the reactor produce electricity for use in creating a very high strength magnetic field. Then you introduce some mass into the coil which accelercates the mass out the other end as ions. Again, F=ma=thrust. This type of engine is already being used by NASA.

Why are we using hydrogen as reaction mass, and not something that's easier to store/carry? The reason hydrogen fuel cells are not too feasible yet is at least partly because hydrogen is difficult to compress, thus a tank won't get you too far. Water on the other hand also doesn't compress easily but is quite dense on its own. It's also abundant and cheap.

As for the mass driver, aiming might be a problem for such a long structure. Much easier if the "barrel" is short, which relegates it to freight-type payloads.

not simply ground to orbit.

And a beanstalk is far more attractive than a mass driver for that too. Mass drivers would be OK for sending freight, but not through an atmosphere, and not out of a gravity well.

I have always called myself a pro-nuclear greenie. The blind resistance by the smelly ignorant masses to anything nuclear still pisses me off.

Space is radioactive. The Earths core is radioactive. Yet somehow, if we produce something slightly radioactive ourselves, it is the end of the universe ??

Re: Nice

You won't need to worry about storing a spent nuclear rocket motor. Once it's in space you have a couple of good options available to you that aren't available to high-level nuclear waste on earth.

1: Lunar Storage - Dig nice deep pits on the moon and bury the waste there. No need to worry about possible environmental damage because there is no environment to speak of.

2: Extreme-Orbit - Put the spent engines in an orbit that will take say, oh.. 240,000 years to come back to the Earth, and safely dispose of it when it returns.

3: Solar Furnace - Load a stack of engines up with sensors & cameras (for the science value) and shoot that puppy at the sun! Problem Solved!

Re: why hydrogen?

They use Hydrogen as a reaction mass because they can store so much more of it in liquid form in the fuel tanks.

The exhaust velocity is still way too low.

Let's go the whole hog: a single Orion pulse launch could put an entire space infrastructure into orbit. From then on out, nuclear ion or plasma engines, unconstrained by physical nozzle designs, can take us where we want to go.

@Andrea: You're right -- "push per cc of launcher" is an issue, but H2 is still the "best" reaction mass because it's the lightest and so the exhaust velocity and hence "push per gram" (specific impulse) is highest.

@realism: Ion drives are not slow. They're not high thrust and they need a decent (nuclear) electricity source, but they can run for as long as it takes to give you the delta-V you want, and the specific impulse is sci-fi. What nuclear-electric rockets can't do is get you through the atmosphere.

So instead of polluting this planet we are going to pack up all the really essential things like water and hydrogen, or whatever other fuel we use, and send it off to space.

Simple logic must dictate that eventually this planet becomes uninhabitable through this process, we sure as hell better hope that the Sci-Fi writers are correct and there are other places we can find and live on as a species before we terminally screw this one.

Beanstalk. Best option in the long run, and once it's built your ground-orbit costs are approaching zero. And we're probably closer to realising the neccesary technology than we are for fusion.

"1: Lunar Storage - Dig nice deep pits on the moon and bury the waste there. No need to worry about possible environmental damage because there is no environment to speak of."

Madness!. Didn't you see 'Space 1999'??

There's a great deal of difference between using a fission reaction to pop about in space, and basing your entire domestic electric supply on it.

The comment section is not filled with people objecting to the idea, as from the tone of the article you sorta would expect.

There is a lot wrong with nuclear power generation, the main thing being we can do the job a lot better with coal and sequestration, the secondary being nuclear proliferation, theres not that much between weapons and power. In fact the design for a good combined coal/sequestration power station NEEDS to be designed quickly. Have you seen how many new coal fired power stations the Chinese are bringing on line.

Reduce, reuse and recycle, what a fucking joke. Nuclear power to the rescue. schmuks.

Nuclear engines are mainly interesting if you want to get to the moon (or other planets fast). This means when you transport people, as few other transport types are time-critical. Having people on board nuclear vessels requires heavy shielding, which tends to negate some of the advantage of going nuclear. I suppose it is possible to place the payload (== humans) at a large distance from the nuclear material so less shielding is needed, but it still requires some extra mass.

When time isn't critical, you can use low-energy transfers (http://www.gg.caltech.edu/~mwl/publications/papers/lowEnergy.pdf) and may even use solar power to accelerate hydrogen, so very little fuel needs to be carried.

Nevertheless, the main cost of Earth to Moon transports is getting from the ground to orbit, so until this is made much cheaper, we won't see large-scale moon transport. This brings us back to the space elevators discussed recently. :-)

"That said, the nuclear rocket's uranium core would be a hazard before it was ever fired, and it might be involved in a catastrophic explosion while being lifted to orbit by a normal rocket. But Howe reckons it could be encased in tungsten, which is extremely strong and doesn't melt even under high temperatures. In the event of a disaster, it would come down as a single chunk and be recovered safely."

That's good, except, somewhere in this titanium casing there has to be access to the core, which means there is an escape route for the fuel in the event of a problem.

I expect that's supposed to be radioactive... thats pretty simple, it gains an extra neutron (making deuterium), further increasing the mass of the exhaust, further increasing velocity :)

Have these guys not heard of the Emdrive?

http://www.eurekamagazine.co.uk/article/9657/No-propellant-drive-prepares-for-space-and-beyond.aspx

http://en.wikipedia.org/wiki/EmDrive

which has apparently been shown (in the second prototype) to develop sufficient thrust to move the device in a low-friction environment. The energy to run it could come from solar panels, but even here nuclear generators would probably be used.

Andrea asked:

Why are we using hydrogen as reaction mass, and not something that's easier to store/carry?

For chemical rockets hydrogen offers the greatest amount of energy per kilo when it combines with an oxidiser. Many large rockets use cheap kerosene liquid oxygen combinations for their lower stages then switch to liquid hydrogen oxygen for their upper stages that either insert payloads into orbit or send them on interplanetary trajectories.

A few experiments have been made with compounds involving fluorine and boron that potentially offer even greater amounts of energy, but they are notoriously corrosive and toxic.

For manned missions, hydrogen/oxygen is also used to power fuel cells because the waste (water) can then be used to keep the astronauts alive.

HTH.

Not sure about Nerva, but in the case of the Dumbo design, the radioactive material that could end up in the exhaust was not the reaction mass itself but rather the daughter products of the fission reactions - the requirement for a very low barrier to heat exchange meant that some of them could reach the reaction mass. Nerva may have had the same issue.

Hydrogen is used as reaction mass because, for a given exhaust temperature (as set by the engine design, and the requirement that it remain solid!), hydrogen gives the highest specific impulse. "Easier to store" materials may actually give a lower specific impulse than chemical engines.

is ignorance and bad publicity.

"Nuclear" = Evil to the general public.

Since we can rely on the general public to remain ignorant despite everyones best efforts, to move forward we should take advantage of this.

Rename Nuclear energy as something warm and fuzzy, like "Shiney energy".

Then, put some little used letter from the alphabet in front of it -" i " is probably owned by Apple, " x " by some conspiracy of advertising-for-crap-products consortium.. and pretty soon everyone will want a "qShiney" powerplant in their suburb, and it will take a couple of decades before some Uni student does a health study and starts making awkward allegations.

I'm not bitter and cynical, I am perfectly adjusted to the environment I live in..

I'm all in favour of sending nukes into space - surely that's been the basis of ICBMs for decades and no one seriously said we could do without them did they? We could also remember the comments from ROSPA recently which said that we should be allowed to play dangerous games and risk bumps and bruises as we mature. Put them both together and you're hard-pushed to come up with a justifiable reason for not using nuclear energy in space.

Anyway, as has been pointed out many times here before; the biggest hurdle is the small step to GEO and beyond. If only we could overcome that problem then we probably wouldn't need to worry so much about nuclear energy in space - just stick the reactor in a packing crate and send it up the space elevator! Isn't a side effect of the space elevator that it might generate electricity? I'm sure I've stumbled across that whilst working (reading theregister).