Deep Space Propulsion via Magnetic Fields

The beauty of magnetic sail concepts — magsails — is that they let us leave heavy tanks of propellants behind and use naturally occurring phenomena like the solar wind to push us where we’re going. Solar sails, of course, do the same thing, though they use the momentum imparted by photons rather than the energetic plasma stream of the solar wind. And Cornell University’s Mason Peck is now suggesting another kind of mission that leaves the fuel behind. Instead of using the solar wind, it taps magnetic fields like those around the planets.

As we’ll see in a moment, we might one day use this method to send a fleet of micro-probes to Proxima Centauri. But let’s examine it first in light of planetary missions, which is what Peck has in mind with his Phase II NIAC study “Lorentz-Actuated Orbits: Electrodynamic Propulsion Without a Tether.” What the researcher is proposing is that a spacecraft can be made to accelerate in a direction perpendicular to a magnetic field. We know from Cassini images how the orbits of dust particles in Saturn’s rings are governed by such forces.

In fact, this ‘Lorentz force’ proves to be tremendously useful in the near-planetary environment. A spacecraft in Earth orbit, for example, creates a charge as it moves through the plasma surrounding the planet. The charge is minute, but it can be boosted either by emitting charged particles from a high-energy beam, or by using a lightweight surface (Peck suggests a thin, cylindrical wire mesh) to house a greater charge. Once charged sufficiently, the spacecraft will be deflected by the planetary magnetic field in a direction perpendicular to the magnetic field lines.

Jupiter’s magnetic field, containing fully 18,000 times the energy of Earth’s magnetosphere, would be ideal for this kind of work, offering plentiful opportunity not just for orbital adjustment but even for ‘hovering’ in place over a particular area to be studied (Robert Forward used to discuss doing something like this with ‘statites,’ satellites that would use solar sails to hover in Earth polar orbit or elsewhere). And imagine the increased payload that could be added to a Galileo-style spacecraft to Jupiter without the 371 kg of propellant that flew aboard that mission!

But the notion really opens up when you begin considering much smaller vehicles. Here I’m going to quote our own Larry Klaes, who wrote Peck’s work up for Ithaca (NY’s)’s Tompkins Weekly:

[Peck] notes that the concept might be ideal for small spacecraft. Cornell graduate student Justin Atchison is developing a satellite that is the size and heft of a single wafer of silicon.

“At this small scale, a spacecraft might be surprisingly susceptible to Lorentz force effects,” explains Peck. “But rather than launching just one of these ‘ChipSats,’ NASA might launch millions of them that would act as a swarm of very small sensors to detect life on another planet, provide communications, or serve as a distributed-aperture telescope many kilometers in diameter.”

As we move into the realm of ChipSats, Peck has my full attention. Take the ChipSat to its logical conclusion and you can envision thousands of tiny spacecraft slung out from the Solar System at ten percent of lightspeed to make the journey to the Centauri stars. “When these small craft arrive,” says Peck (I’m quoting from Larry’s story again), “they might send back a single, simple signal; one bit of information confirming or denying some scientific principle, such as is there a blue-green planet, for example.”

Peck’s completed Phase I study for NIAC is here, and you can read a precis of the Phase II project as well. Compared to solar sails or tether concepts, the Lorenz-Actuated Orbit (LAO) offers singular benefits. Peck writes:

“Electrodynamic tethers and solar sails certainly have their place. Tethers are convenient for deorbiting spacecraft in a passive way (i.e. without applied power). Solar sails work just as well, if not better, outside the geomagnetic field as they do near the earth. However, both suffer from the problem that the very large structures involved can deform under the action of the forces on them, reducing their performance. In the case of a tether, it appears that only gravity-gradient balance or spinning will help align a tether stiffly enough for it can raise an equatorial orbit in a mass-efficient way without buckling, tangling, or becoming redirected into a useless orientation. Solar sails are virtually impossible to reorient in an agile fashion. Our goal is to develop the LAO concept to the point where it is highly compact but offers the same propellantless benefits. The result will be an agile propellantless spacecraft. Even if the LAO spacecraft includes a long wire for capacitance, this wire will result in the same effect regardless of its direction. This significant advantage argues for the continued investigation of the LAO concept and suggests that it may prove more readily adaptable to existing mission architectures than are tethers.

You can read more about the concept at Peck’s site, and the issue of the Tompkins Weekly with Larry Klaes’ article is here. I’m also reminded of Robert Freitas idea of the ‘needle probe,’ an interstellar vehicle the size of a sewing needle but equipped with the nanotechnological tools to create an observing station out of raw materials it finds in the planetary system to which it is sent. Send not one or two but thousands of these for redundancy and you open up the nearby stars to minute examination. Will ChipSats offer a way to put instrumentation into Centauri space and beyond?

Addendum: I had originally referred to “Jupiter’s magnetic field, fully 18,000 times stronger than Earth’s…,” which Paul Dietz points out in the comments below is a mis-statement, as now corrected above.

Bussard and Fusion: A Practical Alternative

Some time later this month a paper by Robert Bussard should become available [Addendum: The paper is already available here — thanks to a sharp-eyed reader for the tip]. You’ll want to pay attention when it appears, because Bussard has spent well over a decade at Energy Matter Conversion Corporation (EMC2), a San Diego company he co-founded, working on devices that could be the most practical approach to fusion ever developed. They’re cheap, small and produce helium as their only waste product. Bussard believes they could be commercially viable in six to twelve years. And he has never made any secret of his wish that reliable fusion engines will one day explore deep space.

But of course fusion’s other benefits are equally immense, from improving the environment to ending nuclear waste production, replacing coal, oil and gas-burning power plants with clean energy that will stabilize industrial economies. He spelled all this out in a presentation now available as a downloadable video, a lecture he gave at Google in his continuing search for funding. Earlier sources like the US Navy, which saw its entire advanced energy development budget cut for 2006, have simply dried up as all attention seems riveted on the ITER European fusion research project, which is based on a tokamak design.

IEC fusion prototype

You should watch this video to get an idea of the alternative. It’s called inertial electrostatic confinement fusion (IEC), and it’s based on the reaction between hydrogen and boron-11, which is totally neutron-free. Traditional fusion research (if fusion research can be considered ‘traditional’) involves deuterium and tritium, but the neutrons produced are only one of the problems thus created.

Image: This is a WB-5 machine, part of a series of experiments developed as Bussard’s team investigated inertial electrostatic fusion concepts. Credit: Energy Matter Conversion Corp.

As to benefits in space, listen to the International Academy of Science’s statement about Bussard’s work in naming IEC a finalist for Outstanding Technology of the Year for 2006:

Design studies of IEF-based space propulsion show that this technology can yield engine systems with thrust/mass ratio 1000 times higher for a given specific impulse (Isp), over a range of 1000 < Isp < 1 x 10^6 sec, than any other advanced propulsion means, with consequent 100 times reduction in costs of spaceflight.

You can trace IEC’s roots back to the early part of the 20th Century, with contributions from none other than Philo Farnsworth, the pioneer of raster scan television, and a graduate student of his named Bob Hirsch, who wrote a classic paper on the technology in 1967. Those deep roots may be part of the problem, as Bussard says finding people less than 65 years old who can work readily with the technology is a continuing problem. Modern research has seemingly moved away from some of these techniques, much to our cost.

What does Bussard need? At Google, he outlined a program to continue the research into IEC, one that would take four to five years to produce a full-scale demonstration device. The details are in the talk, but be believes such a demonstrator capable of generating power will cost about $200 million. Listen to the lecture, in which Bussard describes a series of IEC devices he and his team built, with increasingly positive results even as their funding dried up.

Meanwhile, what’s wrong with the tokamak technology that came out of the Soviet Union in the 1950s? Bussard calls these huge devices ‘superconducting cathedrals,’ noting that a practical plant based on this technology would be 36 meters high and 45 meters wide. The US, he says, has spent $18 billion on tokamak designs so far with no clear result and no apparent end in sight. The tokamak approach is highly radiocative, provides no clear road to a practical power plant, and absorbs government funding like a sponge compared to alternative approaches. You can see why Bussard is frustrated.

Normally, the name Bussard appears in these pages in relation to a classic 1960 paper in which he outlined an interstellar ramjet principle. In that scenario, a spacecraft with a vast electromagnetic scoop could trap interstellar hydrogen and use it to drive its engines, thus producing continuous acceleration that could open up the stars at relativistic speeds. It’s a sensational idea, though one that fell out of favor when it became clear that drag was a serious problem, so serious that more recent thinking is that such a scoop could actually be used for braking upon arrival at a destination solar system by a spacecraft powered in some other way.

Tau Zero novel

Robert Bussard has left his fingerprints all over the subject of interstellar flight (and we again give a nod to Poul Anderson’s novel Tau Zero, so heavily influenced by Bussard’s ideas). But his contribution to energy and fusion technologies at places like TRW and Los Alamos is legendary, and he may be leading the way to a fusion solution of more immediate application. Philanthropic funding at these levels is more than feasible. All it takes, as Bussard says, is the right people with a visionary outlook and a willingness to put their money on an idea that is out of the conventional research loop. Google may not be that funding angel, but my guess is that Bussard’s work will attact another.

Image: The cover of the first paperback edition of Poul Anderson’s Tau Zero, published in 1970 (a shorter version called “To Outlive Eternity” appeared in 1967 in Galaxy Science Fiction). This tale of a runaway interstellar ramjet drew heavily on the work of Robert Bussard.

As we wait for the new Bussard paper (and absorb the video’s implications), it’s wonderful to go back to the earlier work on ramscoops. The key paper is “Galactic Matter and Interstellar Flight,” Acta Astronautica 6 (1960), pp. 179-1994. Thanks to Vincenzo Liguori, Adam Crowl and Larry Klaes for early pointers to the Bussard video.

Gravity, Inertia, Exotica

Are we ever going to understand what makes matter resist acceleration? If we can get a handle on inertia, we’ll have a better idea what’s possible when it comes to exotic propulsion. 19th Century physicist Ernst Mach believed that inertia was the result of matter being acted upon by all other objects in the universe, even the most distant ones. At the University of California at Fullerton, James Woodward has been studying inertia in a Machian context for some time, and an implication that appears to grow out of it: an object undergoing acceleration may experience transient fluctuations in its mass.

It will take a great deal of experimentation to find out whether there is anything to this, but the idea is interesting enough to keep Woodward working. His theories are put to the test in the laboratory, for they predict an effect that should be measurable. Indeed, his work with capacitors produces results that can be interpreted as mass reduction, though getting a clear data signal through the experimental noise is not easily done. How such mass reduction squares with the laws of physics, and just how far it can be taken — is this a clue to possible anti-gravity effects? — are questions that remain unanswered.

But the implications are intriguing. Be aware, then, of two sites that focus exclusively on Woodward’s activities. The polymath (he’s a member of both the history and physics faculty at Fullerton) maintains a research page of his own with links to older papers explaining his theories, and a bibliography of recent publications. A PDF on propellantless propulsion is useful, as is the older paper “Mach’s Principle and Impulse Engines: Toward a Viable Physics of Star Trek?” which Woodward presented at NASA’s Breakthrough Propulsion Physics workshop in 1997.

Woodward doesn’t refer to what he’s studying as the ‘Woodward Effect,’ but the name has begun to settle in, and Peter Vandeventer maintains a Woodward Effect site containing background papers (unpublished) and links to further information. As Vandeventer notes, Woodward prefers to talk about the ‘Mach Effect,’ a refreshing dose of humility in a world filled with people intent on naming things after themselves. Whatever we call it, the effect studied by Woodward and others gives some credence to the notion of a ‘Mach-Lorentz thruster,’ a spacecraft that, as Woodward once said, “…puts out thrust without blowing stuff out the tailpipe.”

Be aware, too, of a recent paper by Martin Tajmar, Florin Plesescu and team that discusses work sponsored by both the US Air Force and the European Space Agency. The authors attempted to “…measure the gravitational field induced by a non-stationary gravitomagnetic field generated by an angularly accelerated superconducting ring.” If confirmed, these findings would appear to demonstrate the production of a gravitomagnetic field of measurable magnitude in the laboratory. Which is to say that years of research lie ahead to examine such effects and place them in a sound mathematical context.

We may find, of course, that there are other explanations for the results of both Woodward’s and Tajmar’s experiments — Tajmar, for example, notes quite different results from earlier claims by Evgeny Podkletnov about gravitational shielding effects above rotating superconductors. But provocative work that tests the boundaries of known physics is worth keeping an eye on as followup investigations continue. Most hypotheses fail — this is how science works — and we are early on in putting a number of fascinating concepts to the test. Let’s hope funding for the most testable of these ideas continues to emerge as we get an idea of which hypotheses make sense.

A Potential Breakthrough in Quantum Gravity

An effect that far exceeds what would be expected under Einstein’s theory of General Relativity has been produced in a laboratory. The fact that the effect — the gravitational equivalent of a magnetic field — is one hundred million trillion times larger than what General Relativity predicts has raised the eyebrows of more than a few researchers. But Martin Tajmar (ARC Seibersdorf Research GmbH, Austria) says that three years and 250 experimental runs have gone into this work, and encourages other physicists to examine and verify it.

If confirmed, the new findings could be a key result in the search for a quantum theory of gravity. We know that a moving electrical charge creates a magnetic field, and General Relativity assumes that a moving mass likewise generates a gravitomagnetic field, one that should, by the tenets of GR, be all but negligible. To test this, Tajmar and colleague Clovis de Matos (European Space Agency HQ, Paris) used a ring of superconducting material rotating 6500 times per minute. From an ESA news release:

Spinning superconductors produce a weak magnetic field, the so-called London moment. The new experiment tests a conjecture by Tajmar and de Matos that explains the difference between high-precision mass measurements of Cooper-pairs (the current carriers in superconductors) and their prediction via quantum theory. They have discovered that this anomaly could be explained by the appearance of a gravitomagnetic field in the spinning superconductor (This effect has been named the Gravitomagnetic London Moment by analogy with its magnetic counterpart).

The result: acceleration sensors placed close to the spinning superconductor show an acceleration field that seems to be produced by gravitomagnetism. In other words, a superconductive gyroscope seems to be capable of generating a gravitomagnetic field, making it the gravitational counterpart of the magnetic coil used in Michael Faraday’s classic experiment of 1831. In that groundbreaking work, Faraday moved a magnet through a loop of wire and observed electric current flowing in the wire, thus demonstrating electromagnetic induction.

Despite being far vaster than what General Relativity predicts, the effect is nonetheless just 100 millionths of the acceleration due to Earth’s gravitational field. It could, nonetheless, represent a breakthrough in engineering acceleration fields. “If confirmed, this would be a major breakthrough,” says Tajmar, “it opens up a new means of investigating general relativity and its consequences in the quantum world.”

Further research and confirmation of these findings will be a fascinating process to watch. The results were presented on March 21 at ESA’s European Space and Technology Research Centre in the Netherlands. The two papers to study right now are:

Tajmar, Martin, F. Plesescu, K. Marhold, and Clovis J. de Matos, “Experimental Detection of the Gravitomagnetic London Moment,” submitted to Physica C and available here.

Tajmar, Martin and Clovis J. de Matos, “Local Photon and Graviton Mass and its Consequences,” submitted to International Journal of Modern Physics D, available here.

Creating a Traversable Wormhole

Can traversable wormholes be created, allowing us to achieve our wildest dreams of traveling between the stars? Mohammad Mansouryar says yes, and in a paper titled “On a macroscopic traversable spacewarp in practice,” the young Iranian theorist lays out his argument. Mansouryar bases his thinking on a needed prerequisite: the violation of the Averaged Null Energy Condition. He writes up its parameters in a 41 page document stuffed with conjectures, eight boxes of figures and 127 footnotes.

Mansouryar’s analysis is intractable to Centauri Dreams, demanding an examination from those far more competent in theoretical physics than myself. Especially given his startling conclusion: “In this paper, I have tried to review the literature, in the spirit of whether the TWs [traversable wormholes] in practice are far reaching or constructible by present knowledge & technology. The conclusion is they are quite possible to manufacture provided a sufficient determination of investment on improving computation tools & necessary materials.”

The goal, of course, is all but magical. A workable wormhole using Mansouryar’s methods would allow a spacecraft to take a cosmic bypass, riding a subluminal warp drive through the wormhole shortcut so that distances through space are radically altered while maintaining spacetime stability for passengers. The result is a hybrid of warp drive thinking a la Alcubierre and the classic wormhole as, more or less, conceived by science fiction.

On a Web site devoted to his work, the author notes that while increasing velocity in space is a desirable goal, the final goal is not the speed of light. For one thing, even c is too limiting when compared to cosmic distances, and the technical problems of accelerating closer and closer to c still stand. Mansouryar is also well aware of control problems at superluminal speeds, impacts from interstellar dust at high velocity, and the intractable issue of propulsion systems. His goal is to create a system in which local movement is much less than c but, as he says on his Web site “…the considered distance changes so that consequently would be less devoted time, finally in compared to a situation if a light pulse would be supposed to pass the same distance.”

A traversable wormhole is a solution if we can find a way to produce the negative energy needed to create and stabilize it. The paper discusses methods for producing exotic matter and muses on techniques to verify Mansouryar’s wormhole theories experimentally. Abstract and full text are available on the arXiv site, where the paper will doubtless produce controversy and discussion — particularly as to his experimental ideas — more illuminating than Centauri Dreams can provide.

The Felber ‘Antigravity’ Thesis and Cosmology

Those interested in reading the controversial paper by Franklin Felber recently presented at the STAIF meeting in Albuquerque can find it here. The summary is concise: “The Schwarzschild solution is used to find the exact relativistic motion of a payload in the gravitational field of a mass moving with constant velocity. At radial approach or recession speeds faster than 3-1/2 times the speed of light, even a small mass gravitationally repels a payload. At relativistic speeds, a suitable mass can quickly propel a heavy payload from rest nearly to the speed of light with negligible stresses on the payload.”

A first reading of the paper reveals an intriguing implication: Felber’s solutions of Einstein’s field equation imply that any mass produces what Felber calls an ‘antigravity field’ above a certain critical velocity. And although this field is at least twice as strong in the direction of motion, the field also repels particles in the opposite direction. It follows, quoting Felber again, that “…a stationary mass will repel masses that are radially receding from it at speeds greater than 3-1/2 c, with obvious cosmological implications.”

Is Felber suggesting a way of explaining Einstein’s cosmological constant, and thus accounting for the apparent acceleration in the universe’s expansion? An intriguing thought, though the equations that express it will demand long and patient scrutiny. Audacious papers make fascinating reading, but the road to experimental verification is unforgiving, as all too many researchers have learned.