Antimatter Power: Reaching for Deep Space
By Robert Myers
Special to SPACE.com
posted: 07:00 am ET
30 October 2002
To Steve Howe, a trip to Pluto is small potatoes. That most distant planet orbits about 40 times further from the Sun than the Earth. But that's not even half as far as Howe dreams of traveling.
About five times further out, in the neighborhood of 250 Astronomical Units, or AUs (an AU is 93 million miles, the distance of the Earth from the Sun), is the Oort Cloud of comets. Even our fastest and most distant spacecraft, Pioneer 10 and Voyagers 1 and 2, are still decades away from this destination. Twenty-five years after launch, Voyager 1 has only now reached the 77 AU point. TECH WEDNESDAY
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Artist's representation of the antimatter sail spacecraft.
A Penning trap uses electric and magnetic fields to trap charged particles (ions). The two batteries at the two ends produce the electric field (red field lines). The magnetic field lines (green) travel from bottom to top. These field lines allow researchers to confine particles such as antimatter in the trap. (Courtesy National Institute of Standards and Technology.)
Using a Ioffe-Pritchard trap, howe expects that large quantities of anti-hydrogen atoms could be stored safely for long periods.
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So to get a spacecraft to the real edge of the Solar System and beyond in a reasonable amount of time, Howe turned to that most exotic of substances, antimatter. In a study funded by the NASA Institute for Advanced Concepts (NIAC), Howe is laying the groundwork for a faster, better, cheaper antimatter drive.
"We're trying to find an architecture to do really deep space exploration," says Howe. "Technology that might allow interstellar missions."
"Essentially we want to go really deep, reasonably fast," and avoid the huge vessels and leaps in technology that other concepts require, says Howe.
"What we tried to look at, instead of going to big, massive fusion engines that require big engines and big heavy weights, is high energy density and low mass," Howe explains.
A Different Kind of Sail
At first glance, Howe's antimatter sail looks like yet another solar sail variant. But there are important differences.
First, the sail itself is considerably smaller than a several miles-wide solar sail. With a diameter of 15 feet (5 meters), the antimatter sail is wonderfully compact.
Secondly, the ship will provide its own "wind" in the form of puffs of antimatter released from the spacecraft. When these antiparticles encounter the sail thrust is generated in not just one, but two ways.
First of course are the tiny explosions as the antimatter particles collide with the sail. Secondly, and more importantly, the antimatter's annihilation will react with a thin layer of uranium-235 coating the sail, creating a tiny amount of nuclear fission.
"We're using the base (fission) reaction, fundamentally," Howe says, "So we can keep our masses down."
The combination adds up to maximum bang for your buck in terms of mass. This means a smaller spacecraft can reach higher velocities more quickly. Howe's goal is a craft that can reach the 250 AU mark in 10 years or less.
Accelerating this way, Howe's vessel could reach a speed of 260,000 mph (116 kilometers per second) in four months. By comparison, Voyager 1 is a virtual tortoise putting along at a mere 38,000 mph (17.4 kps).
However, any advanced design like this is not without its hurdles. "The real hub is the storage," Howe says. "There's a lot of technology between here and there."
Howe has already begun studying this problem with funding from another NIAC proposal. Since you can't store antimatter in a regular fuel tank, Howe has found two possible ways to capture antimatter created in the lab before it annihilates itself.
One method involves keeping magnetized antiprotons in a container of frozen hydrogen. The magnetic field and the deep cold would keep the particles from bouncing into the walls and destroying themselves.
The other method involves allowing positrons and antiprotons (the mirror twins of normal electrons and protons) to clump together into antiatoms of antihydrogen. It might sound anti-rational, but that would make them easier to store.
"(There's a device called an) Ioffe trap which supposedly should be able to build and hold the antihydrogen," says Howe.
Either way, Howe expects the stored material would most likely take the form of tiny crystals, or "nanosnowflakes" of antihydrogen.
"Large" Scale Production
Antimatter is still remarkably hard to create, and even the most advanced labs like Fermilab in Batavia, Illinois, typically only creates about a billionth of a gram a year. To fuel Howe's space ship, they'd need to seriously ramp up production.
"What's needed is to build a cooling ring," Howe explains, a project that would cost on the order of $20 million and allow the mass production of more antimatter.
And Howe has a lot of ideas of how to use antimatter for things besides space ships. Using the radiation generated, Howe foresees advances in detection and treatment of cancers, as well as aiding national security by helping detect hazardous materials.
"It's always been a hobby," says Howe of antimatter. He worked for years studying its uses at NASA, before funding cuts prompted him to take his research to the business world.
However, Howe's first love is space exploration. Ever since he heard about antimatter on the original "Star Trek" show, he's been fascinated.
"Conceptually if we found the funding, we could do it in a year," Howe laments. "We're on that border, that fringe."
And I remember when I first head that they actually had made Antimatter. One of my girlfriends in college was talking to me about a lecture she had gone to the year before I showed up where the Air Force Physicist was talking about working with Anti-matter and she mentioned that he made it sound like they were just making tons of the stuff to use for future projects. I would hope that they could do something like this in my lifetime, but again, we'll see. Right now I don't think NASA could hit the moon again.