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Beamed core antimatter propulsion - more efficient, but don't hold your breath!


June 12, 2012

Will antimatter fuel the interstellar spacecraft of the future? (Photo: Shutterstock)

Will antimatter fuel the interstellar spacecraft of the future? (Photo: Shutterstock)

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Antimatter propulsion is the Holy Grail of spaceflight. When matter and antimatter react, the energy produced is several billion times larger than the thermomechanical energy resulting from burning a kilogram of a hydrocarbon fuel. Now a high school student has developed a new magnetic exhaust nozzle that would double the velocity of an antimatter-powered rocket.

Despite the extraordinary difficulty of generating and storing significant amounts of antimatter, the potential it offers as a power source for interplanetary and interstellar voyages is nearly irresistible to spaceflight visionaries. Hearing this call to adventure, Roman Keane, a high school senior at Western Reserve Academy in Hudson, Ohio, and his mentor, Senior Research Fellow Wei-Ming Zhang of Kent State University, decided to optimize an existing model for an antimatter-powered rocket engine.

Matter reacting with antimatter is the ultimate source of energy which might be available to power space travel beyond the Solar System. The energy released by the reaction of a gram each of antimatter and matter is about equal to that of a forty kiloton atomic bomb. As a result, numerous conceptual studies have examined antimatter as a fuel for extrasolar spacecraft. A full design effort is somewhat pointless at this stage, as at present we don't know how to manufacture, store, or manipulate large quantities of antimatter - the current cost of that gram of antimatter is roughly estimated at about a trillion US dollars.

One element of the system that can be studied with existing technology is the design and operation of a magnetic nozzle for a beamed core antimatter rocket engine. By causing moving charged particles to be directed into a beam, the magnetic nozzle generates propulsive thrust from the annihilating antimatter.

The beamed core antimatter rocket depends on a little-known fact about antimatter - the only particle-antiparticle annihilation that immediately converts 100 percent of the particle mass into energy is the reaction of an electron with an positron. In contrast, when protons and antiprotons react, they produce a variety of charged and uncharged pions, which are elementary particles. More interesting phenomena occur when antiprotons annihilate against a compound nucleus, such as copper or lead. Many of the electrically charged reaction products retain their identity as charged particles long enough that they can be focused into a unidirectional beam by a magnetic nozzle.

Past studies of such magnetic nozzles determined that magnet coils providing a magnetic field well in excess of 100 Tesla in strength were required. Such strong magnetic fields can only be produced in extremely short pulses using today's technology, so this early solution was not practical. These studies also suggested that the exhaust velocity of a beamed core antimatter engine would top out at about a third of the speed of light, which is rather marginal for interstellar missions.

To accelerate to a speed equal to that of the engine's exhaust velocity (0.33 c) and then decelerate to a stop at your destination, 86 percent of the initial mass of the spacecraft would have to be fuel - half of that antimatter. One could in principle go faster, but reaching a speed of double the exhaust velocity (0.66 c) and then stopping at your destination would require that 98 percent of the spacecraft initial mass is fuel - a rather difficult build job, although use of multi-stage vehicles could improve the situation in the same way as is seen in chemical rockets.

Keane and Zhang decided to take another go at designing and optimizing a magnetic nozzle for a beamed core antimatter engine. The simulation of antimatter reactions and of the dynamics of charged particles moving in magnetic fields has advanced considerably since the time of the previous studies. This has been the result of three decades of increasingly more subtle simulations to analyze the data from high-energy particle collisions. Keane and Zhang used analysis software from CERN for their study.

Depiction of the simulated trajectories of the products of a proton-antiproton collision. ...

Depiction of the simulated trajectories of the products of a proton-antiproton collision. The blue lines represent positive pions, the green lines negative pions, and the brown straight lines are gamma rays mostly generated by the decay of neutral pions. Note that the both positive and negative pions are eventually directed out the nozzle (Image: Keane and Zhang)

They found that a magnetic nozzle about four meters long and 1.5 meters in diameter having a maximum magnetic field of 12 Tesla would represent an optimal configuration for the general design assumed in the study. Such a magnetic nozzle could be made using today's technology, although some rather special engineering would be needed to attain large values of thrust.

Most encouraging is that the effective exhaust velocity of the new nozzle design is about 69 percent of the speed of light. This means that a beamed core antimatter spacecraft with the new nozzle could make a one-way trip at a speed of about two-thirds of the speed of light carrying seven times the payload that could be hauled using the old nozzle.

Clearly, developing a spacecraft to ply the vast expanses between stars is a terribly difficult enterprise, and the methods to be used when our technology has advanced enough will probably not be like anything we can currently conceive. Despite that, it is often inspiring to take a small bite of a nearly impossible project, and discover that we indeed can solve a bit of it in the here and now. That this has been accomplished by a high school student increases one's faith in the future of technology.


About the Author
Brian Dodson From an early age Brian wanted to become a scientist. He did, earning a Ph.D. in physics and embarking on an R&D career which has recently broken the 40th anniversary. What he didn't expect was that along the way he would become a patent agent, a rocket scientist, a gourmet cook, a biotech entrepreneur, an opera tenor and a science writer.   All articles by Brian Dodson

I've seen a lot of articles in various science magazines focusing on how difficult it is to store antimatter.

There is, of course, a possible way around this.

The way around the problem is to **only generate the antimatter when it is needed**.

If you look at the problem that way, then the antimatter storage problem goes away, and it now becomes a matter (excuse the pun) of creating the antimatter (from ordinary matter).

That would itself be difficult, but it would still be enormously easier than trying to store antimatter.

13th June, 2012 @ 02:15 am PDT

"the current cost of that gram of antimatter is roughly estimated at about a trillion US dollars."

this is why our monetary economy doesnt work. all these technological advancements that would be ready immediately if the resources were given to it, but in this current world, money is all that matters to survive...

follow the zeitgeist movement for a new economic system!

Tony Kalniev
13th June, 2012 @ 03:29 am PDT



As soon as I read that, I thought the same thing...

A fantastic energy source who could be available and perfected with experiments as of right now is being delayed. And so is our development.

Fábio Dias
13th June, 2012 @ 06:25 am PDT

"The way around the problem is to **only generate the antimatter when it is needed**.

But surely the amount of energy required to generate anti-matter on board is going to be as much, if not more, than the energy obtained by using it. In which case you might as well use an ion propulsion system. The only way to make sense of this is to generate the "fuel" on earth/in orbit and then carry it with you.

Crazy idea: could we ever harness the gravity of the moon to work for us? Everyday the moon drags trillions of gallons of seawater around the earth, creating tides. The negative effect on the moons' orbit is too small to measure. Here is a vast source of energy to be tapped. But how?

13th June, 2012 @ 11:20 am PDT

re; mooseman

How much energy and mass does it require to produce antimatter? hint you never get more energy out of a system than you put in.

It sounds to me like you're trying to solve one problem by creating a bigger one.

13th June, 2012 @ 12:45 pm PDT

A rocket is capable of moving faster than its exhaust. Remember, it's the reaction to the exhaust in the same frame of reference that provides the acceleration, not the "absolute" velocity of the exhaust. So the fact that the exhaust travels at .69 c would not impede the craft using the engine from greater velocities, including those very close to the speed of light. Other factors (especially radiation from collisions with the rare but present particles in space) would limit the speed of the craft, not the exhaust velocity.

Wouldn't it be possible to collect anti-protons or positrons in near Earth space? To collect positrons you'd use something like a mass spec where you'd electrostatically accelerate negatively charged anti-protons around a curved track and put an as yet hypothetical "anti-matter collector bottle" where negatively charged particles of the proton's mass would go. The charge would separate anti-protons from the positively charged protons and the mass would separate the anti-protons from electrons. A similar collection apparatus could be used to collect positrons. I wonder why I've not seen this idea anywhere- so there must be a fault in it.

John J. Peloquin
13th June, 2012 @ 06:00 pm PDT


So we should all surrender our freedoms and becomes slaves to work for this purpose so you can travel through space ?

Zeitgeist = collectivist = global poverty

13th June, 2012 @ 07:23 pm PDT

Antimatter is hard to be produced, stored, and manipulated for propulsion. Better is the fusion-powered plasma turbine.

13th June, 2012 @ 07:34 pm PDT

You're not thinking, people. Interstellar travel will come, but lets build this puppy and try it out around the solar system. Dr. Robert Forward described the problems of "containing" antimatter and using it for an interplanetary drive 25 years ago. Among the things he mentioned is that antimatter costs so much because we've only been using it for research. We have never tried to optimize the process to mass produce it. Check with the National Space Society. I bet somebody there still has copies of his work. I'm just going by memory.

James Bogart
13th June, 2012 @ 07:50 pm PDT

re; John J. Peloquin

While true, the lower the exhaust velocity the more propellent that is required to accelerate a specified mass to any specified velocity.

re; fruitsalad

Well said.

13th June, 2012 @ 09:36 pm PDT

Protons, Anti-proton & Sci-Fi.

Protons have a gravitational field for use as a repelling force and Anti-protons have no gravitational field that could be of use as a repelling force. So like glass scratching glass. Anti-protons can penetrate the nucleus of protons and release the energy in side with out compression on the Proton.

Shock wave onto a focusing crystalline structure to create an Anti-dimensional Proton without a gravitational field that when condense pull in the surrounding space into another dimension.

Robert DuBois
13th June, 2012 @ 10:19 pm PDT

I like that besides your product, the propellant, you get gamma rays that are scattered about in any direction - including you, the pilot.

Fretting Freddy the Ferret pressing the Fret
14th June, 2012 @ 10:53 am PDT

Pellegrino, in "Flying to Valhalla", explains how. Near-sun orbital stations using abundant solar energy to generate and contain the anti-matter.

Of course, this is in the context of the Rules for Alien Contact, developed with Asimov. Short form: some aliens may be predatory, attempting to squelch all other species. Even one would be enough. All other species, suspecting this, must as a matte of self-preservation assume that any others might be that sort, so also will have to pre-emptively exterminate any they find.

The best way to do this is watch for signals and, ultimately, any life-bearing planet, and send a package to it. A couple of shuttle-mass antimatter-powered missiles should do it. At about 0.92C, they'd punch a 100-mi. wide vacuum tunnel in the atmosphere, penetrate the crust, and shower the planet with burning debris and toxins. Game over!

So these solar automated factories stock up on such missiles, and send them off at the first sign of potential competitors.

Of course, the odds are excellent that we have a package headed our way right now. At that speed (.92C), you see them about 12X as far away as they are physically. Detected a few light-hours out by their gamma wake, you'll have a few minutes to bend over and kiss your bippy good-bye!

(This, by the way, solves the "Fermi Paradox" -Where are they? Answer: all gone, killed each other off. Our turn should come sometime soon.)

The only way to maybe survive is to find another star with dead planets, dig in, and be VERY quiet. Hurry!

Brian Hall
14th June, 2012 @ 11:20 am PDT

The plasma conduits of protein. The helix of many proteins is a long containment field with perfect exclusion--better than any magnetic one--from it's small core size. Moving ions from anywhere to anywhere should be easy. They said linear accelerators were the first truly novel invention--using proton ATPase running millions of said accelerators in the speaker's cells.

Facebook User
15th June, 2012 @ 12:40 am PDT

re; Fretting Freddy the Ferret pressing the Fret

Tungsten absorbs gamma rays converting them to heat which can then be used to generate electricity for powering the ship.

re; Brian Hall

I refuse to believe that genocidal xenophobia is the default mode of intelligence.

15th June, 2012 @ 02:32 pm PDT

Humanity as a whole is insane.

Our economic system is incompatible with the future, both technological, and morally. As it is it supports corruption, greed, and injustice, we need to build the infrastructure to support a planet wide cashless system...and that would never happen without a massive revolution because our economic and world leaders would never agree to it. I fear that kind of transformation would only happen after a total collapse of our curent civilization.

Antimatter is a noble goal, but researching the technology to produce it would likely lead to a safer and cheaper solution for power production and drive technology. Much of what we know was discovered by accident.

John Hemingway Parkes
17th June, 2012 @ 07:49 pm PDT

I wonder if the calculations are with Newtonian or with Relativistic physics. I think we would first have to give it a try with Neutonian, just to see if there would be a need for a lot less fuel? I mean, if this is true: then the latter could be so. Just saying, lets think scientifically and prove things work like we think they do...

Alfredo Balmaseda
18th June, 2012 @ 09:30 am PDT

The easiest way to store antimatter is not to try containing it at all and thus trick it into staying exactly where you wanted in the first place.

19th June, 2012 @ 08:19 am PDT

There are many good ideas here in this forum. Yet I have not heard the Idea that makes anti-matter drive at .99c light possible.The answer is of course not to take any fuel with the ship. Since anti-matter may be accelerated to .99c, the answer is to essentially beam a stream of anti-matter and matter to the ship that is then put into reaction on-board. Beaming might take place from a position like Uranus or Neptune where orbital-deltav is less and a cold sump for molecular extraction exists. The ship would essentially look like the McDonald's logo. The ends of the m - the beam input, and the middle base of the m a duel vectored nozzle. BTW, one way trips only, good for fast probes. Or... if one insists on passengers, the ship mass is only used for deceleration, thus one would want to bring a set of beam guns with them to set up at the other end.

Dr. VonsterMonster
19th June, 2012 @ 10:30 am PDT

I can foresee a giant laser in a near-Sun orbit aiming at the spaceship to accelerate it with photons or even better: Causing a reaction in it to form plasma. The problem would be decellerating tough...

Damian Reloaded
30th January, 2013 @ 09:17 am PST
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