Robert Forward used to talk about antimatter factories in space, installations that would draw their power from the Sun. He would point out that at a distance of 1 AU, our star delivers a gigawatt of energy for each square kilometer of collector. And being Robert Forward, he thought big: Build a collector array one hundred kilometers on a side to produce a power input of ten terawatts, enough to drive several antimatter factories at full power and produce a gram of antimatter each day.
Forward saw the antimatter problem as a matter of scaling and cost (and he often talked about ‘small problems of engineering’). As we’ve seen in the last few days, James Bickford (Draper Laboratory) is more than aware of both these issues, but unlike Forward, he’s keen on mining naturally occurring sources of antimatter right here in the Solar System. Forward’s huge factories may some day be built, but for now, let’s talk about how to get our early antimatter missions into the realm of possibility by learning how to cull the needed antimatter, if only in the minute quantities that would kick a payload up to 100 kilometers per second. Along the way, we establish the expertise to go further.
What Bickford has in mind is using a plasma magnet to create a magnetic scoop that can influence the trajectory of a charged particle over large distances. In an equatorial orbit around Earth, such a scoop could trap antiparticles occurring in the planet’s radiation belt as they, obeying the Lorentz force, bounce back and forth between their mirror points in the Northern and Southern hemispheres. The antiproton belt our spacecraft is tapping is analogous to the protons in the Van Allen radiation belt, and provides a close to home source of antimatter before we look out into the Solar System, where we find further stores especially around Saturn.
We’re still talking about large structures to collect this material, but nothing like Forward’s huge collector arrays (or, for that matter, his vast Fresnel lens in the outer Solar System that would enable a laser-beamed lightsail mission). In his Phase II NIAC report, available here on Centauri Dreams, Bickford talks about using high temperature superconductors to form two pairs of RF coils with a radius of 100 meters and a weight of some 7000 kilograms combined. 200 kW is needed to operate the system, achievable through nuclear or solar power. What happens is straightforward: The magnetic field driven by the RF coils concentrates the incoming antiprotons and then traps them.
Comparing this concept with what we do today, Bickford finds that space harvesting of antimatter is five orders of magnitude more cost effective than the Earth-based alternative. Working out Earth’s antiproton flux in relation to this scheme, he talks about collecting 25 nanograms per day, with up to 110 nanograms stored in the central region between the coils. And note: If you’ve looked at Bickford’s earlier Phase I report, be aware that his plasma magnet supplants that report’s single coil loop. The Phase II paper goes through all of the options that led to this result.
And here’s a spectacular mission concept from the report:
The baseline concept of operations calls for a magnetic scoop to be placed in a low-inclination orbit, which cuts through the heart of the inner radiation belt where most antiprotons are trapped. Placing the vehicle in an orbit with an apogee of 3500 km and a perigee of 1500 km will enable it to intersect nearly the entire flux of the Earth’s antiproton belt. The baseline mission calls for a fraction of the total supply to be trapped over a period of days to weeks and then used to propel the vehicle to Saturn or other solar system body where there is a more plentiful supply. The vehicle then fully fills its antiproton trap and propels itself on a mission outside of our solar system.
We’re talking realistic missions into the Kuiper Belt and perhaps to the Sun’s gravitational focus, where so many interesting things happen to enhance the image of objects examined from there (bear in mind that the Sun’s gravity focus, unlike an optical lens, allows incoming radiation to stay on the focal axis at distances greater than 550 AU — just get to that distance and a new category of observation becomes possible). In any case, missions of greater speed and with even more ambitious targets are possible. As Bickford notes: “Future enhanced systems would be able to collect from the GCR [galactic cosmic ray] flux en route to further supplement the fuel supply.”
For that matter, how about creating an antimatter ‘fuel depot’ that could be used to support closer-in missions to Mars and the asteroids? All seem feasible provided the collection system can be made to function. But the idea is compelling: Bickford says the plasma magnet influences the trajectory of charged particles near the spacecraft, which then follow the field lines and are concentrated in the throat of the collection system. The momentum of the particles is then braked by RF and/or electrostatic methods so that the antimatter becomes trapped in the inner coil region. Long-term storage seems possible given the paucity of protons in the region between the coils, hence little loss by annihilation.
We’ll talk again soon about the technologies needed to make this come together, and discuss Bickford’s ideas on future research possibilities. As happens so often in examining space technologies, we can sketch out the shape of deeply promising concepts that rely on the development of a true space-based infrastructure to come to fruition. The major point remains: Building that infrastructure will open up possibilities denied to us now, among them the opportunity to experiment with propulsion methods that may one day power true interstellar missions.
Great concept if it proves practical. I really like the fuel depot idea.
Saturn as a fill-up stop before heading to the Kuiper Belt? It could happen!
It sounds like a great idea. This layman wonders whether making the RF coils out of mercury encased in a helium jacket would reduce the power required? I’ve read it makes a great superconductor. And what if you hooked the scoop up to a space elevator/tether? I foresee technological cross-over potential between this concept, sails and elevators (fingers crossed).
Five orders of magnitude? Hm.
That would reduce the cost of antimatter from $100 trillion per gram, down to… $1 billion per gram.
Am I missing something?
Doug M.
Doug, here’s the relevant quote from the Bickford report: “Based on the Earth antiproton flux, the system would be capable of collecting 25 nanograms per day and storing up to 110 nanograms of it in the central region between the coils. The system is more than five orders of magnitude more cost effective than Earth based antiproton sources for space-based applications.”
So Saturn’s ring system is an interstellar fuel depot for antimatter! Who knew?
I never cease to be amazed by the creative brilliance of some thinkers, e.g. Bickford’s ideas. What’s especially viable is that we do not need to launch a large payload into LEO to gather the fuel. The 100 ton spacecraft to Saturn is more problematical however.
BOTE calculation here.
A gram of antimatter gives you ~9 x 10^13 joules. A nanogram would give a billionth of that: about 9 x 10^4 joules. So, 110 nanograms -> about 10^6 joules.
By way of comparison, burning a gallon of gasoline releases about 1.5 x 10^8 joules. So, 110 nanograms is equivalent to about half a fluid ounce of gasoline.
I ask again, am I missing something? Is my math wrong?
Doug M.
Doug, I think you should get 2×10^7 J from that 100 ng. You missed carrying a digit in your multiplication, and then you would want to double the joules since you need an equal amount of matter to liberate the energy.
I don’t know about gasoline, but you could light a 100 watt light bulb for about 2-1/3 days, if you can figure out how to tame those gamma rays into dribbling out electrical energy and at 100% efficiency.
Doug, I passed your message along to Dr. Bickford, who was kind enough to send the following:
In response to the question posed on the blog, he is correct about the magnitude of the energy content. You actually would get about 2X when you also include the rest energy of the proton as well, but the magnitude question still remains. The reason why such small quantities of antiprotons matter is that they are used to catalyze other reactions in sub-critical nuclear material. Basically, the annihilation naturally induces other reactions which is where most of the net energy comes from.
Beamed core antiproton propulsion directly uses the antiproton annihilation energy but requires hundreds to thousands of kilograms to reach the highest velocities. However, table (1.2) summarizes several other published concepts for alternative concepts that require far fewer antiprotons. In these catalyzed concepts, an antiproton enters a target and induces a fission reaction which cascades to generate most of the thrust. The advantage of this is that you get nuclear energy densities from your fuel without having to bring along what amounts to a nuclear reactor.
I hope this answers the question. I can expand on it if needed. The detailed analysis I based this on can be found in the paper, “Antimatter Production for Near-term Propulsion Applications” by Schmidt et al. which is online at:
http://www.engr.psu.edu/antimatter/Papers/NASA_anti.pdf
How is he planning to cool the antiprotons? Trapping them into a much smaller volume than they originally occupied necessarily will cause their temperature to increase, if you do the compression isentropically. The entropy needs to be removed in order to avoid having the gas get very hot.
(This is also a problem with Bussard-like interstellar ramjets.)
Good question. I’ve floated a query to Dr. Bickford.
Ok, we collect antimatter, then what? Antiprotons in nature are not unlimited. Economy based on collecting antimatter won’t be different from today’s oil economy. At the end it will agonizing.
Antimatter production like this in Star Trek is something better, far better.
Paul, here’s what Dr. Bickford had to say in response to your question about antiproton cooling: “Yes, we were planning to cool the incoming particles. Even without any compression heating, their energy must be degraded to trap them in the B field of the loop. We proposed several ways to do this. Adding some intervening mass is the most straightforward technique though this tends to be massive and you’ll lose a small fraction of the incident flux to annihilation. Alternatively, we suggested using polarized RF waves to selectively cool the antiprotons and heat the protons to promote trapping of one species over another. Finally, a third option is to use electrostatic fields to degrade the flux. A combination of the techniques is probably most desirable to minimize power and mass requirements. These are briefly discussed on page 104 of the report.”
Paul, based on this description I have to wonder if resistive and radiative losses in the deceleration and capture of his 25 ng per day objective is problematical. You say he says it takes 200 kw to operate this system, which presumably includes these types of losses, even with non-cooled superconductors. If that’s accurate it will take, per day, 1.7E10 J to capture a mass-energy of 25 ng of antiprotons which, when detonated, produces about 5E6 J. Yes, once captured, the containment should be reasonably low in energy consumption, but still.
Have I missed something?
Ron, here’s Dr. Bickford’s response: “I’m not sure I completely understand what is being asked here, but let me take a shot at answering what I think he is talking about. The 200 kW mostly comes from the power needed to make up for resistive losses in the rotating plasma which is used to form the large scale magnetic field. The energy required to maintain this over the course of a day is substantially more than the rest mass of the antiprotons collected over the same period. However, the intrinsic energy content of the antiprotons is not what is actually important; instead the key factor is how efficiently it can generate thrust via the nuclear cascades that I mentioned in one of my previous responses.
Another important consideration under some circumstances is the difference in system mass. You can afford to have a heavy power system at a fuel station compared to a nimble spacecraft that does not have to carry the entire collection system. It does not matter if the system energy to antiproton energy ratio is very large as long as you’re only using it to fuel a smaller spacecraft with a much better mass ratio.
I hope this helps!”
Lubo, I think part of the attraction of the idea is that the antiproton resevoirs around the giant planets are self replenishing. The one around earth is to, but at a much slower rate, so the use of antiprotons mined from around earth would have to be restricted to the barest minimum. And given that the amounts available are tiny, and of interest only as catalysts for conventional nuclear reactions in the very specific case of spacecraft propulsion, I can’t imagine any economys being built on it.
So to apply this result to an area relevant to modern society, how could we work this in to a Dan Brown novel plot?
You can never know what their intentions are ;)
Thanks, Paul, I think I understand now. The antiproton collector is to be stationary and separate from the spacecraft.
I still find the energy budget issue interesting. It’s no mean feat to produce 200 kw continuously to run the collector, but doable. The overall systems issues of Bickford’s scheme make me uncomfortable since it seems to me to be complex, expensive and fragile. At least it’s good to see someone working to put the whole system together conceptually.
I think it’s great that Dr. Bickford is responding like this. Okay, two more questions.
1) What would be a long-term sustainable rate of “harvest” from the Earth’s antiproton reservoir? IOW, how big is the reservoir, and how fast does it replenish?
2) What about charge? Even a hundred nanograms of antiprotons will carry quite a lot of charge.
Doug M.
Doug, here’s Dr. Bickford’s response to your two questions, along with some additional material (thank you, Dr. Bickford!): “1) The Earth field has a total quasi-static supply of about 160 nanograms. This is replenished at the rate of about 2 nanograms/year. In comparison, Saturn has a 10 microgram supply that is replenished at the rate of 240 micrograms/year. Table (1.3) in the report summarizes these values for all planets and more.
“2) Space charge limits are a factor – we’ve worked around the issue by neutralizing the overall storage volume with an equal quantity of protons. Positrons could also be used but are probably harder to deal with. You may wonder how we can handle both protons and antiprotons in the same volume without significant annihilation losses – it turns out that the density is extremely low making the loss rate insignificant. Earth antiproton traps are about 1cm3. In comparison, our trap is nearly twelve orders of magnitude larger in terms of volume. The resulting plasma density is very low and prevents significant losses from occurring.
“I also wanted to clarify something from earlier. It is possible to have the antiproton collector separate and stationary from the spacecraft. The mass ratios should be good enough so the entire vehicle/collector would be propelled. This is nice since the magnetic field also acts as a radiation shield and a nozzle for the propulsion system. However, for the highest performance, it would work quite well to have a separate collector and spacecraft. This is an area we’d want to pursue in more detail if funding ever resumed.”
Black holes, neutrinos and gravitational proprieties of antimatter
Authors: Dragan Slavkov Hajdukovic
(Submitted on 13 Dec 2006 (v1), last revised 25 Nov 2007 (this version, v2))
Abstract: The gravitational proprieties of antimatter are still a secret of nature. One outstanding possibility is that there is gravitational repulsion between matter and antimatter (in short we call it antigravity). We argue that in the case of antigravity, the collapse of a black hole doesn’t end with singularity and that deep inside the horizon, the gravitational field may be sufficiently strong to create (from the vacuum) neutrino-antineutrino pairs of all flavours. The created antineutrinos (neutrinos) should be violently ejected outside the horizon of a black hole composed from matter (antimatter).
Our calculations suggest that both the supermassive black hole in the centre of our Galaxy (Southern Sky) and in the centre of the Andromeda Galaxy (Northern Sky) may produce a flux of antineutrinos measurable with the new generation of the neutrino telescopes; like the IceCube Neutrino Detector under construction at the South Pole, and the future one cubic kilometre telescope in the Mediterranean Sea. A by the way result of our consideration, is a conjecture allowing determination of the absolute neutrino masses. In addition we predict that in the case of microscopic black holes which may be eventually produced at the Large Hadron Collider at CERN, their thermal (Hawking) radiation should be dominated by a non-thermal radiation caused by antigravity.
Comments: This new version is four times longer than the first one, and consequently contains much more results
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics – Theory (hep-th)
Cite as: arXiv:gr-qc/0612088v2
Submission history
From: Dragan Hajdukovic [view email]
[v1] Wed, 13 Dec 2006 22:25:14 GMT (132kb)
[v2] Sun, 25 Nov 2007 12:15:35 GMT (211kb)
http://arxiv.org/abs/gr-qc/0612088
Instead of having the array at 1 Au, wouldn’t it make more sense to drop the array to like inside the orbit of mercury. Since the photo energy density would be much higher there. Energy density is proportional to 1/d^2 where d is the distance from the sun.
The Mystery of the Missing Antimatter
Helen R. Quinn and Yossi Nir
http://press.princeton.edu/titles/8475.html
The shape of the mysterious cloud of antimatter in the
central regions of the Milky Way has been revealed by
ESA’s orbiting gamma-ray observatory Integral.
The unexpectedly lopsided shape is a new clue to the
origin of the antimatter.
Full story:
http://www.esa.int/esaSC/SEMKTX2MDAF_index_0.html
Would an antimatter apple fall up?
00:03 12 June 2008
NewScientist.com news service
Rachel Courtland
New experiments are being proposed to test a big unknown in physics: how antimatter reacts to gravity.
Physicists have studied antimatter, the mirror version of ordinary matter, for decades. They know, for example, that antiparticles have the same mass as ordinary particles, but opposite charge. But no one knows what effect gravity will have on such particles.
Now several groups want to measure exactly how Earth will pull on antimatter. The tests would create a horizontal beam of the stuff and measure how much gravity deflects it.
The complicated ballistic test may show no difference between the way matter and antimatter fall. But some experimentalists are holding out hope that they may see something completely unexpected, which could point the way to new gravity-like forces, or perhaps even antigravity.
“If antimatter fell down faster, it would mean the discovery of at least one new force, probably two. If it fell up, it would mean our understanding of general relativity is incorrect,” says Thomas Phillips, a physicist at Duke University in Durham, North Carolina, US.
Full article here:
http://space.newscientist.com/article/dn14120-would-an-antimatter-apple-fall-up.html
September 13, 2009
Temporary Radiation Belt Discovered at Saturn
Written by Nancy Atkinson
A new, temporary radiation belt has been detected at Saturn, located about 377,000 km from the center of the planet, near the orbit of the moon Dione. The temporary radiation belt was short-lived and formed three times in 2005.
It was observed as sudden increases in the intensity of high energy charged particles in the inner part of Saturn’s magnetosphere, in the vicinity of the moons Dione and Tethys, and likely was caused by a change in the intensities of cosmic rays at Saturn.
“These intensifications, which could create temporary satellite atmospheres around these moons,” said Dr. Elias Roussos, “occurred three times in 2005 as a response to an equal number of solar storms that hit Saturn’s magnetosphere and formed a new, temporary component to Saturn’s radiation belts.”
Full article here:
http://www.universetoday.com/2009/09/13/temporary-radiation-belt-discovered-at-saturn/
After reading this article, I am feeling a little lost on the actual collection of antimatter. Not even so much that, but the actual storage of it. How would you contain something in a, case lets say, without it touching the container. You would need to do this because the contact of matter and antimatter leads to the annihilation of both, equal masses, and then releasing energy powerful enough to destroy whatever it is contained within. I know I am not very smart, but how would you do it? Would you use electromagnetic fields? And if so, would the antimatter be affected then? Also, the harnessing of energy would weird because half the energy is released in the form of neutrinos. Please tell me if I am wrong, and explain it.
DTuck, antimatter can be contained within magnetic fields, which is how antimatter traps like HiPat work today. They’re effective but they can house only the tiniest amount of antimatter — in any case, we can’t make more than very small amounts of antimatter in the first place. Better antimatter storage will be a priority if we figure out better ways to produce the stuff.
I have a question and I know I am very late in reading this article but if you read this please answer back. If we are able to go up all the way to the Kuiper belt wouldn’t we already need some form of advanced propulsion. The only viable options are nuclear reactors or some form of electric propulsion. Unforunately I see nuclear fusion as the one with the most money and research so if we are to have it commercialized the antimatter source would be rendered obsolete. For example I have designed a spacecraft which uses 6 nuclear fusion reactors as a form of propulsion, with 2 fission reactors as power back ups and a use of 13 Ion drives. Now the fusion propulsion system allows for continous speed with only about 5-10 percent of the whole energy being used as electricity. The fission reactors may be used for propulsion should more power be required. The fusion reactions stop when decelerating is required and the Ion drives turn on to use the last of the momentum of the fusion reactions. I am not sure about exactly how much time it would take to reach the antimatter but my guess is somewhere in the amount of five hours or less. For my design come true or the factories to come true or anything in space travel that deals a significant change would mean that we would have to be much like the entities in sci-fi works.
Varun, I don’t see a workable fusion drive as making antimatter obsolete because antimatter allows us to extract so much more energy from the matter/antimatter annihilation. A working fusion drive would be a wonderful thing and could open up the outer Solar System. But once we develop fusion, we can still hope for much stronger antimatter reactions to be used in propulsion, assuming we can find ways to collect or produce sufficient antimatter.