Going to Mars via Fusion Power? Could Be

A high-speed, lightweight way to travel in space — provided someone can actually build the thing

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At first, it’s hard to know whether to take the company known as Princeton Satellite Systems (PSS) seriously. For one thing, the PSS offices, a few rooms in a nondescript building in nondescript Plainsboro, N.J., right above the Sugar and Sunshine Bakery, don’t exactly suggest the imminent conquest of the final frontier. The company’s ambitions, by contrast, certainly do — but those sound so crazy that you have to wonder if they’re serious. This team of a half-dozen or so scientists and engineers is determined to send human beings to Mars, launch robotic probes to the outer solar system, send missions to Alpha Centauri and more, and do it all with rockets powered by nuclear fusion.

You heard that right: fusion. It’s the energy source that makes stars shine and that plasma physicists have been trying to tame for more than 50 years — so far, despite ever more gigantic and expensive machines, in vain. Controlled fusion could power the entire planet with energy free of carbon emissions and with negligible radioactive waste, but it’s proved so difficult to pull off that a commercial reactor won’t see the light of day for decades to come at the very soonest. Nonetheless, the folks at PSS think they might be able to build a fusion-powered rocket motor much sooner than that, and they may be onto something.

The advantages of such a breakthrough are easy enough to see: a fusion rocket for a Mars mission, says company founder Michael Paluszek, “would be smaller than a minivan, and you could get there and back in less than a year, compared with more than two years for chemical rockets.”

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That’s because a fusion drive would have more thrust than its conventional counterparts, but would weigh far less: the fuel itself would add up to just a few pounds, compared with thousands for a liquid-fuel rocket. The extra speed would reduce the danger to astronauts from interplanetary radiation, and it would slash the food, water and other supplies they’d need to bring with them in half.

Fusion power could also be ideal for deep-space robotic missions like Europe’s planned Jupiter Icy Moons Explorer (JUICE). Just as with a Mars trip, a trip to the outer solar system under fusion power could be made a lot faster than the eight years it will take JUICE to get there. The fusion reactor could also supply more than ample electricity to scientific instruments and communications gear once the spacecraft arrives, saving engineers the trouble of designing a separate power source.

It sounds implausibly good, but it might not be. Fusion happens when atomic nuclei, in the form of a hot, charged gas called plasma, are forced to fuse together, releasing enormous amounts of energy. The biggest challenge in getting nuclei to overcome their natural repulsion is to heat them up while keeping them tightly confined. Reactors like the huge one under construction in Europe use radio waves for heat and powerful magnets for confinement.

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That’s the idea here too, but it took a lot of fiddling with the wirelike antenna that delivers the radio waves to get things up to a high enough temperature. “That wire,” says PSS reactor designer Samuel Cohen with unalloyed pride, “represents my entire career.” The familiar torus-shaped magnet that’s used in most plasma reactors also had to be straightened out so it could be used in the new system. Those adaptations and others make the PSS reactor a lot smaller and cheaper to build — in principle, anyway. “We haven’t even produced a burning plasma yet,” says Paluszek, which means they haven’t achieved even minimal fusion, although they have built machines that demonstrate confinement and heating at a subfusion level.

This doesn’t prove the concept will actually work, as the engineers readily admit. “A lot more physics has to happen before then,” says Paluszek. But it’s plausible enough that the Department of Energy has sponsored some of the research. And while a handful of other labs are working on their own fusion-rocket designs, says staff engineer Yosef Razin, “we were the only ones at the 2012 International Astronautical Congress to have actual experiments.”

There’s one more difference between the PSS design and a conventional reactor, which serves as both a huge advantage and a huge disadvantage at once. Most fusion reactors run on deuterium and tritium, which are the heavier siblings of hydrogen. The PSS reactor relies on a combination of deuterium and helium 3. This helps address another problem with fusion energy, which is that while it gives off negligible radioactivity, negligible isn’t nothing, and in this case, the radiation comes in the form of a stream of neutrons, which can be deadly up close. The deuterium–helium 3 combination produces less neutron energy, meaning that a manned spacecraft would require less shielding around the crew compartment.

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Unfortunately, helium 3 is incredibly rare. “There’s enough on earth to run a single hundred-megawatt power reactor for a few decades,” says Cohen. The PSS reactor would be more like a 1-MW version (you’d probably use four of them to get to Mars, for more power and for redundancy). Even so, a fleet of interplanetary fusion rockets would start to eat into the supply. There’s plenty of helium 3 on the moon, but that raises a whole different set of problems.

On the other hand, says Paluszek, “if the Navy said, ‘Oh, gee, we’d like to use these for nuclear submarines,’ we’d find ways of getting all the helium 3 we need.”

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26 comments
Jameson
Jameson

one word... Minovsky Ultracompact Fusion Reactor on Gundam =)

dmoore95503
dmoore95503

Oh Dear:

If we haven't been able to achieve controlled fusion in the easiest reaction achievable: Deuterium and Tritium. Why oh why are we still talking about Helium-3 reactions? It just doesn't make sense.

TonyHanscomb
TonyHanscomb

Helium-3 is sitting on the surface of the moon mixed in with what is called regolith (The hellion, the nucleus of a helium-3 atom, consists of two protons but only one neutron, in contrast with two neutrons in common helium) the "dust" could be gathered from the surface using a giant orbiting "Vacuum cleaner" ! processed on board and transferred to a lunar/earth shuttle transporter, which would drop huge capsules for entry to earth for Earth consumption or rendezvous to spaceships in orbit for their fusion fuel or alternatively "parked" in earth orbit for later use. The huge Transporter ship would never need to land as it would endlessly  "shuttle" between earth and moon and guess what the entire operation could be powered using Helium-3 fed fusion ! (If this idea is used I only want 1% of the profits, thank you)


iongeopol
iongeopol

Helium 3 - plenty of supply on the moon.  Is that why the Chinese have a lunar landing project, and we don't?  Give this some thought.

HermesMercury
HermesMercury

Helium 3 is much more prevalent on the Moon -- which we can reach.

HenryKBarton
HenryKBarton

It is entirely plausible inducing nuclei to overcome their natural repulsion to fuse together, releasing enormous amounts of energy for interplanetary propulsion to explore our solar system still in our lifetime.  http://www.youtube.com/watch?v=VUrt186pWoA

vbscript2
vbscript2

"That’s because a fusion drive would have more thrust than its conventional counterparts, but would weigh far less: the fuel itself would add up to just a few pounds, compared with thousands for a liquid-fuel rocket."

Try millions unless you're assuming this thing is already in orbit when it launches. For comparison, the Space Shuttle stack was 4.5 million pounds, the vast majority of which was fuel. A rocket that intends to leave Earth's orbit needs even more fuel than one going to orbit, since it must attain escape velocity, not just orbital velocity. Furthermore, if you wish to get to another planet quickly, you'll likely need to go well beyond escape velocity. You also need some way to slow down quickly once you get there, as ramming into Mars' surface at tens or hundreds of thousands of miles per hour would be rather unpleasant.

JoeJones2
JoeJones2

right.  I'll have my George Jetson car by the time you have this fusion rocket.


Get real.

derykhouston
derykhouston

The best way to overcome the problem of getting the plasma to fuse by heating is to think in reverse.

 Instead. Super cool the system at the three most critical points. 

(Similar to the idea of pulling more gently on the teflon to get it into strands which doesn't work....... Instead.....yank it..... and you will have more success.)

fivebytuesday
fivebytuesday

We must mine the moon and move forward with this technology.

mothergoosemc4
mothergoosemc4

Humm I am curriuose if the same methods can be applied with a different fuel source like methane hydrate.

poulosejp
poulosejp

But it’s plausible enough that the Department of Energy has sponsored some of the research. Follow the money trail.



SanMann
SanMann

@HermesMercury,

Would require strip mining major portions of the surface of the Moon. Think of all the poor flora and fauna.

Shoeone
Shoeone

@HermesMercury The search for Helium-3 provides an economic incentive for going back to the Moon, which is good, but it's hard for me to believe that there is not a way to create Helium-3 at a reasonable price right here on Earth.

YosefRazin
YosefRazin

@vbscript2 The proposed system can be launched on a single NASA Space Launch System which is currently in development.  Thus, to get to LEO it does uses chemical propulsion.

KaiserBeebe
KaiserBeebe

@JoeJones2 The one sure mark of the ignorant is to instantly discredit anything they deem impossible.

rapier1
rapier1

@LarryLuv I think you need to read that article again. It's at about the same stage of development as the propulsion technology discussed here. In particular - the 200 MW power supply in order to make that Mars mission is still just an idea on paper. It's promising technology and seems to be worth pursuing. However, it is not *in any way* a 'done deal'. As for 'wasted' federal fundage the VASMIR system is also federally funded. The government has a policy, when it comes to blue sky projects like these, to fund multiple avenue of research in order to maximize the chance that at least one of them may prove fruitful.

YosefRazin
YosefRazin

@mothergoosemc4 This is a fusion reaction not a chemical combustion.  The easiest things to fuse have very low atomic weights and are single atoms, not molecules, therefore all proposed systems concentrate on protons, hydrogen (deuterium, tritium), helium, boron, and lithium.

seanwrath
seanwrath

@mothergoosemc4 No. The He3 is acting like a Neutron sponge, and combining (I'm guessing here,) with detritus particles to form the more common He4. (Which is like most helium on the planet.) Most of the Helium in nature is He2 or He4.

rapier1
rapier1

@poulosejp And discover what exactly, that the government funds ground breaking research that may have a significant impact on our lives? SHOCKING!

YosefRazin
YosefRazin

@Shoeone @HermesMercury  Small amounts can be bred from Tritium decay as we dismantle the US nuclear arsenal as well as extracted as a by-product from hydrocarbon processing.

vbscript2
vbscript2

@rapier1 @LarryLuv Getting a 200 MW power source isn't really all that hard. The hard part is getting one that's light enough. Lots of existing commercial reactors are more than 200 MW output power. I think some are closer to a GW or so now. Even the jet engines on a Boeing 777-300ER aren't too far off 200 MW of output power. Full rated performance on its GE90-115b engines is about 75 MW/engine, IIRC (and it has two of them.) A normal rocket stack is probably capable of much more than 200 MW peak output power.

rapier1
rapier1

@vbscript2 @rapier1 @LarryLuv That's 200MW of electrical power. The jet engines require a large amount of fuel (imagine running those all the time for 40 days) and oxygen so those aren't really feasible in this scenario. The 200MW from a fission power source is what they are talking about but the reactor design that would make sense in this scenario is still conceptual. Weight is a huge issue as well as the issues of actually being in a non-conductive environment. The heat you generate stays with you as the vacuum of space is an excellent insulator.