Space

Researchers developing fusion rocket to slash travel time of Mars missions

Researchers developing fusion ...
Artist's concept of a fusion-drive ship
Artist's concept of a fusion-drive ship
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The fusion driven rocket test chamber at the UW Plasma Dynamics Lab in Redmond
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The fusion driven rocket test chamber at the UW Plasma Dynamics Lab in Redmond
Artist's concept of a fusion-drive ship
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Artist's concept of a fusion-drive ship
Details of a fusion-drive ship
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Details of a fusion-drive ship
Steps in the FRC fusion process
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Steps in the FRC fusion process
FRC fusion engine
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FRC fusion engine
UW experimental FRC setup
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UW experimental FRC setup
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Traveling through deep space is a hazardous undertaking and choosing the right engine can mean the difference between a fast, successful mission and a slow one with mounting dangers of radiation sickness, equipment failures and personal conflicts. A team of researchers from the University of Washington (UW) and Redmond, Washington-based MSNW are aiming to expand the options by developing a new fusion drive rocket engine that promises to make possible a manned spacecraft that could reach Mars and return to Earth in months rather than years.

There are a number of ways of getting to Mars, but the options are pretty limited if it includes having a crew on board. The obvious choice is chemical rockets. That’s how all space vehicles from Earth are launched and most are set on their trajectories. It’s a tried and trusted technology, but long ago reached the point of diminishing returns. Without getting into the maths, using chemical rockets would mean building a huge Mars ship that is mostly fuel with a tiny payload that will take years to complete the journey.

Nuclear thermal rockets

One alternative is a nuclear thermal rocket that gets its power from splitting heavy atoms such as plutonium in more or less the same way as power plants do on Earth. These rockets have been under development since the 1940s, but none have ever been used on a space mission. There are a remarkable number of designs, from straightforward fission reactors that heat hydrogen as it passes through the core, to exotic gas core reactors. With their greater power output and energy density, they hold the promise of more powerful engines and thus shorter journeys, but there are a lot of tradeoffs that offset the advantages – such shielding and larger tanks to accommodate lighter weight propellants. So in reality, even the most practical ones don’t reach much more than a 30 percent improvement over chemical rockets.

According to the research team, a nuclear thermal rocket Mars mission would require nine launches to put the Mars ship into Earth orbit at a cost of more than US$12 billion – and that doesn't include the rest of the budget for building the ship, exploring Mars or making the tea. The ship would weigh 848 tonnes (935 tons) and a round trip mission to Mars would take 4.6 years.

“Using existing rocket fuels, it’s nearly impossible for humans to explore much beyond Earth,” said lead researcher John Slough, a UW research associate professor of aeronautics and astronautics. “We are hoping to give us a much more powerful source of energy in space that could eventually lead to making interplanetary travel commonplace.”

Fusion Driven Rocket could be the answer

The team believes that they can do better using a Fusion Driven Rocket (FDR). As the name implies, it uses fusion, the fusing of light elements, as a power source instead of fission. There are a number of ways of causing fusion and here the Washington team is using a Field Reversed Configuration (FRC).

FRC fusion engine
FRC fusion engine

A FRC is a device for confining plasma on closed magnetic field lines without a central penetration. It uses huge electric capacitors powering an extremely powerful magnetic field with one million amps that causes large lithium metal foil rings to implode on a blob of ionized hydrogen plasma as it squirts into the engine. The metal foil squeezes the plasma for a few microseconds until fusion occurs. The magnetic field then channels the superheated, ionized metal out of the rocket nozzle at high velocity in a pulse of thrust.

It’s not a very smooth ride. The pulses come at one minute intervals, so the ship travels in a series of jolts rather than a constant thrust, but the Washington team believes that it can do the job and is very efficient with only a bit of material the size of a grain of sand producing as much power as a gallon (3.7 l) of chemical rocket fuel. According to the team, a Mars ship using the FDR engine would have a mass of only 134 tonnes (148 tons), need only one launch to put it into orbit, and could make the trip to Mars and back in 210 days with a 30 day stopover.

Details of a fusion-drive ship
Details of a fusion-drive ship

Currently, the team is working to develop individual components and then combining them into a working prototype of a whole engine. “I think everybody was pleased to see confirmation of the principal mechanism that we’re using to compress the plasma,” Slough said. “We hope we can interest the world with the fact that fusion isn't always 40 years away and doesn't always cost $2 billion.”

The results of the team’s work was presented last month at the 2013 NIAC Symposium.

The brief animation below shows how the fusion drive works.

Sources: University of Washington, MSNW

The Fusion Driven Rocket: Animation

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22 comments
Adrien
1 million amps?
blobs of ionised hydrogen plasma?
Where do these come from?
MBadgero
Not a convincing argument that fusion is required for a manned Mars trip.
Also, not a convincing fusion rocket engine design, and it appears to require a small nuclear fission reactor to supply the electricity to run it. But at least the company has built actual hardware and this is not entirely a computer graphics fantasy.
Dave MacLachlan
Sounds like a higher-tech version of the Orion nuclear pulse rocket design from the late 1950's - 60's that Freeman Dyson worked on.
Stephen N Russell
still need HLLVs to boost atomic rocket into Orbit for assembly alone. & need to expand ISS for role or add other Orbital Hub Be radical to get to Mars in months vs years, radical.
Slowburn
I doubt that the solar panels in the illustration would provide enough power to make this work. for deep space operations you need to have a high yield radiation shield to protect against solar flares putting a fission reactor on the sunward side of the shield is not a problem.
Dick Doeren
I worked on a project at Lockheed Sunnyvale in the early 60's called RIFT Reactor In Flight Test nuch different that this, Very Interestion
Rustin Lee Haase
Whether this machine proves viable or not, it or others like it will make our solar system seem much smaller and more reachable. I agree with MBadgero. This technology is not essential to make it to Mars. We already have technology that can do that, but research like this is good and the potential of cutting travel time in half or better is nothing to dismiss lightly. I hope they make enough progress to keep the funding going so that they can make a practical machine. It seems like a solid concept. We have a hard time keeping fusion reactions contained in our stationary fusion reactor labs but we don't need to contain them with a fusion propulsion engine. What was a problem becomes something wonderful: THRUST!!
Bob Komarek
Mars Mars mars, blah blah blah.
The resources we need are on the Moon, not Mars. Everyone is in some sort of hurry, and wants to skip the logical step.
That error will cost us dearly.
David Bell
#Dick Doeren - Did you mean "not much different"? Looks like you're no longer with Lockheed; can you tell us more about the old program? I don't remember it, myself.
Leonard Foster Jr
Ion engines work now??? just use a nuke power source!