"Engineering, stand by for warp drive." With that command, the "Star Trek" crew of the U.S.S. Enterprise prepared to hurl the spaceship through the cosmos at superluminal speeds. Warp drive is another one of those science fiction technologies, like teleportation and time travel, that have some scientific basis. It just hasn't been achieved yet. However, scientists are working on developing an interstellar spacecraft engine that is similar to the matter-antimatter engine of the Enterprise.
No engine is likely to generate superluminal speeds; the laws of physics prevent us from doing that, but we will be able to go many times faster than our current propulsion methods allow. A matter-antimatter engine will take us far beyond our solar system and let us reach nearby stars in a fraction of the time it would take a spacecraft propelled by a liquid-hydrogen engine, like the one used in the space shuttle. It's like the difference between driving an Indy race car and a 1971 Ford Pinto. In the Pinto, you'll eventually get to the finish line, but it will take 10 times longer than in the Indy car.
In this article, we will peer a few decades into the future of space travel to look at an antimatter spacecraft, and find out what antimatter actually is and how it will be used for an advanced propulsion system.
What is Antimatter?
This isn't a trick question. Antimatter is exactly what you might think it is -- the opposite of normal matter, of which the majority of our universe is made. Until just recently, the presence of antimatter in our universe was considered to be only theoretical. In 1928, British physicist Paul A.M. Dirac revised Einstein's famous equation E=mc². Dirac said that Einstein didn't consider that the "m" in the equation -- mass -- could have negative properties as well as positive. Dirac's equation (E = + or - mc2) allowed for the existence of anti-particles in our universe. Scientists have since proven that several anti-particles exist.
These anti-particles are, literally, mirror images of normal matter. Each anti-particle has the same mass as its corresponding particle, but the electrical charges are reversed. Here are some antimatter discoveries of the 20th century:
- Positrons - Electrons with a positive instead of negative charge. Discovered by Carl Anderson in 1932, positrons were the first evidence that antimatter existed.
- Anti-protons - Protons that have a negative instead of the usual positive charge. In 1955, researchers at the Berkeley Bevatron produced an antiproton.
- Anti-atoms - Pairing together positrons and antiprotons, scientists at CERN, the European Organization for Nuclear Research, created the first anti-atom. Nine anti-hydrogen atoms were created, each lasting only 40 nanoseconds. As of 1998, CERN researchers were pushing the production of anti-hydrogen atoms to 2,000 per hour.
When antimatter comes into contact with normal matter, these equal but opposite particles collide to produce an explosion emitting pure radiation, which travels out of the point of the explosion at the speed of light. Both particles that created the explosion are completely annihilated, leaving behind other subatomic particles. The explosion that occurs when antimatter and matter interact transfers the entire mass of both objects into energy. Scientists believe that this energy is more powerful than any that can be generated by other propulsion methods.
So, why haven't we built a matter-antimatter reaction engine? The problem with developing antimatter propulsion is that there is a lack of antimatter existing in the universe. If there were equal amounts of matter and antimatter, we would likely see these reactions around us. Since antimatter doesn't exist around us, we don't see the light that would result from it colliding with matter.
It is possible that particles outnumbered anti-particles at the time of the Big Bang. As stated above, the collision of particles and anti-particles destroys both. And because there may have been more particles in the universe to start with, those are all that's left. There may be no naturally-existing anti-particles in our universe today. However, scientists discovered a possible deposit of antimatter near the center of the galaxy in 1977. If that does exist, it would mean that antimatter exists naturally, and the need to make our own antimatter would be eliminated.
For now, we will have to create our own antimatter. Luckily, there is technology available to create antimatter through the use of high-energy particle colliders, also called "atom smashers." Atom smashers, like CERN, are large tunnels lined with powerful supermagnets that circle around to propel atoms at near-light speeds. When an atom is sent through this accelerator, it slams into a target, creating particles. Some of these particles are antiparticles that are separated out by the magnetic field. These high-energy particle accelerators only produce one or two picograms of antiprotons each year. A picogram is a trillionth of a gram. All of the antiprotons produced at CERN in one year would be enough to light a 100-watt electric light bulb for three seconds. It will take tons of antiprotons to travel to interstellar destinations.
NASA is possibly only a few decades away from developing an antimatter spacecraft that would cut fuel costs to a fraction of what they are today. In October 2000, NASA scientists announced early designs for an antimatter engine that could generate enormous thrust with only small amounts of antimatter fueling it. The amount of antimatter needed to supply the engine for a one-year trip to Mars could be as little as a millionth of a gram, according to a report in that month's issue of Journal of Propulsion and Power.
Matter-antimatter propulsion will be the most efficient propulsion ever developed, because 100 percent of the mass of the matter and antimatter is converted into energy. When matter and antimatter collide, the energy released by their annihilation releases about 10 billion times the energy that chemical energy such as hydrogen and oxygen combustion, the kind used by the space shuttle, releases. Matter-antimatter reactions are 1,000 times more powerful than the nuclear fission produced in nuclear power plants and 300 times more powerful than nuclear fusion energy. So, matter-antimatter engines have the potential to take us farther with less fuel. The problem is creating and storing the antimatter. There are three main components to a matter-antimatter engine:
- Magnetic storage rings - Antimatter must be separated from normal matter so storage rings with magnetic fields can move the antimatter around the ring until it is needed to create energy.
- Feed system - When the spacecraft needs more power, the antimatter will be released to collide with a target of matter, which releases energy.
- Magnetic rocket nozzle thruster - Like a particle collider on Earth, a long magnetic nozzle will move the energy created by the matter-antimatter through a thruster.
Approximately 10 grams of antiprotons would be enough fuel to send a manned spacecraft to Mars in one month. Today, it takes nearly a year for an unmanned spacecraft to reach Mars. In 1996, the Mars Global Surveyor took 11 months to arrive at Mars. Scientists believe that the speed of an matter-antimatter powered spacecraft would allow man to go where no man has gone before in space. It would be possible to make trips to Jupiter and even beyond the heliopause, the point at which the sun's radiation ends. But it will still be a long time before astronauts are asking their starship's helmsman to take them to warp speed.