To Space and Beyond With Nuclear Energy

One of the things that you can do with nuclear energy is produce a lot of energy for a long length of time with an exceptionally small amount of uranium – or dilithium crystals, whichever is available. So if you need energy for an extended period of time – say, the time it takes to get from Earth to Mars, then nuclear energy has considerable utility – and you don’t have to worry about dust blocking the sun, as on some of the solar driven rovers.

Now, a group of scientists are thinking bigger – sending astronauts to Mars and beyond and doing it in a way that could get them there and back successfully. This is a barrier that hasn’t been breached, so while this project is in early days, it’s very intriguing.

A team of researchers, including engineers from the Los Alamos National Laboratory, this week reported their successful demonstration of a new concept that could provide reliable nuclear power for space exploration. The technology is still years away from the warp drive of Star Trek, but it could provide a means of propulsion for space travel beyond the moon.

I’m not sure warp speed is even a goal, but fine – it’s hard to avoid Star Trek in this context. And as long as this is what you’re up to, why not dream big? Pluto, anyone?

"We could have a nuclear-powered rocket that could get to Pluto in two years; whereas a chemical rocket would take seven years," said Paul Czysz, Ph.D., professor of aeronautical engineering at Parks College.

"We think it is the enabling technology," he told TechNewsWorld. "If you are really going to do something on this scale, you need to have something other than chemical rockets."

This article doesn’t say so, but even with this as a fanciful extension of the project, you probably couldn’t get astronauts out to Pluto and back with this technology – at least, not alive. And keeping the space travellers alive is a goal of this project.

Anyway, here’s what this gaggle of rocket scientists are up to:

"This is really a new old system, as it is a new platform build on an old technology," said Michael Podowski, Ph.D., professor of nuclear engineering at Rensselaer Polytechnic Institute.

"The Stirling engine is an old one," he pointed out, but "the concept is very healthy. The nuclear factor is not an issue at this point. However, [achieving] efficiency will require a lot more work.

"While the concept is interesting and it makes good use of the elements involved," Podowski told TechNewsWorld, "it will require more work. It is as simple as that."

How old is the Stirling engine? – think 19th century old. The article doesn’t really describe its characteristics very well, so I went over to How Stuff Works for a fuller explanation.

The Stirling engine is a heat engine that is vastly different from the internal-combustion engine in your car. Invented by Robert Stirling in 1816, the Stirling engine has the potential to be much more efficient than a gasoline or diesel engine. But today, Stirling engines are used only in some very specialized applications, like in submarines or auxiliary power generators for yachts, where quiet operation is important. Although there hasn't been a successful mass-market application for the Stirling engine, some very high-power inventors are working on it.

I guess the writer means the deep space scientists as well as others. But what is it about the Stirling engine that might work in a nuclear application? I’d point to these:

The gasses used inside a Stirling engine never leave the engine. There are no exhaust valves that vent high-pressure gasses, as in a gasoline or diesel engine, and there are no explosions taking place. Because of this, Stirling engines are very quiet.

So it appears to have a variation on a containment chamber. But it looks like the nuclear reaction would happen outside the engine:

The Stirling cycle uses an external heat source, which could be anything from gasoline to solar energy to the heat produced by decaying plants. No combustion takes place inside the cylinders of the engine.

A possible scenario would be to use reactors like those on nuclear submarines to drive the engine.

I’m still curious that no one has found a sizeable niche for these engines – I tend to be suspicious of “miracle” technologies that can’t gain traction – especially in nearly 200 years. That can mean scalability problems – I’ve read that it’s a big mechanism for the power it can generate. On the other hand, the engine’s ability to output a constant level of energy without much variation likely hurts it in an automotive context, but might be beneficial for a rocket.

In any event, this is an interesting development that might allow humanity to break through the artificial barrier between the moon and the rest of space. Maybe we won’t have to wait for dilithium crystals to send astronauts to Pluto.