|Artist's conception of an antimatter rocket|
A fusion-powered spacecraft could reach Jupiter within four months, potentially opening up parts of the outer solar system to manned exploration, according to a 2010 NASA report.
A number of hurdles would have to be overcome ― particularly in the production and storage of antimatter ― to make the technology feasible, but some experts imagine it could be ready to go in a half-century or so.
It's "probably not a 40-year technology, but 50, 60? Quite possible, and something that would have a significant impact on exploration by changing the mass-power-finance calculus when planning," Jason Hay, a senior aerospace technology analyst for consulting firm The Tauri Group, said during an Aug. 29 presentation with NASA's Future In-Space Operations working group.
The power of fusion
The fuel for such a fusion-driven spaceship would likely consist of many small pellets containing deuterium and tritium — heavy isotopes of hydrogen that harbor one or two neutrons, respectively, in their nuclei. (The common hydrogen atom has no neutrons.)
|How a fusion powered jet would work|
Inside each pellet, this fuel would be surrounded by another material, perhaps uranium. A beam of antiprotons — the antimatter equivalent of protons, sporting a net electrical charge of minus-1 rather than plus-1 — would be directed at the pellets.
When the antiprotons slammed into uranium nuclei, they would annihilate, generating high-energy fission products that ignite fusion reactions in the fuel.
Such reactions — for example, deuterium and tritium nuclei merging to create one helium-4 atom and one neutron — throw off huge amounts of energy that could be harnessed to propel a spacecraft in several different ways.
"The energy from these reactions could be used to heat a propellant or provide thrust through magnetic confinement and a magnetic nozzle," states the 2010 report, called "Technology Frontiers: Breakthrough Capabilities for Space Exploration," which NASA produced with the help of The Tauri Group and other experts.
The basic idea is not new: Project Daedalus, a study conducted by the British Interplanetary Society in the 1970s, proposed using a fusion rocket to power an interstellar spacecraft. Daedalus' fusion reactions would be sparked by electron beams rather than antiproton beams, however.
|Daedalus spacecraft's spherical tanks contain the fuel pellets for the nuclear fusion engine.|
Perhaps the biggest challenge is obtaining enough antiprotons — which can be produced in particle accelerators — and storing them for long enough to make a far-flung space journey feasible.
According to the "Technology Frontiers" report, about 1.16 grams of antiprotons would be required for a trip to Jupiter. That may not sound like much, but production levels are currently measured in the billionths of a gram.
"Antiprotons are extremely expensive; a few grams would cost multi-trillions of dollars," Hay said. "I believe the total production so far since the 1950s is on the order of like 10 nanograms."
But antiproton production is ticking upward at a fairly fast rate, he added. So perhaps the technology could be the next big breakthrough in space propulsion systems — in the year 2060 or so.
"With a steady supply of antiprotons and nuclear fuel, antiproton-driven fusion can provide abundant energy for large space stations, outposts, and extended exploration missions with relatively small power systems," the "Technology Frontiers" report states.