by Paul Gilster | Jun 18, 2018 | Breakthrough Propulsion |
Marc Millis spent the summer of 2017 at the Technische Universität Dresden, where he taught a class called Introduction to Interstellar Flight and Propulsion Physics, a course he would also teach at Purdue University last November. The former head of NASA’s Breakthrough Propulsion Physics project and founding architect of the Tau Zero Foundation, Marc participated in the SpaceDrive project run by Martin Tajmar in Dresden, an effort that has been in the news with its laboratory testing of two controversial propulsion concepts: The Mach Effect Thruster and the EmDrive. Marc’s review comments on modeling for the former were almost as long as Tajmar’s draft paper. Described below, the SpaceDrive project is a wider effort that includes more than these two areas — neither the EmD or MET thruster had reached active test phase during the summer he was there — but the ongoing work on both occupies Millis in the essay that follows.
by Marc Millis
You may have noticed a renewed burst of articles about the EmDrive. What prompted this round of coverage was an interim report, part of the progress on Martin Tajmar’s ‘SpaceDrive’ project to carefully test such claims. Tajmar’s conference paper [citation below] is one of the early steps to check for false-positives. I expect more papers to follow, each progressing to other possibilities. It might take a year or so more before irrefutable results are in. Until then, treat the press stories about certain conclusions as highly suspect.
On Tajmar’s work, this quote from his conference paper:
Within the SpaceDrive project [6], we are currently assessing the two most prominent thruster candidates that promise propellantless propulsion much better than photon rockets: The so-called EMDrive and the Mach-Effect thruster. In addition, we are performing complementary experiments that can provide additional insights into the thrusters under investigation or open up new concepts. In order to properly test the thruster candidates, we are constantly improving our thrust balance facility as well as checking for thruster-environment interactions that can lead to false thrust measurements.
The Mach Effect Thruster is a different approach to the goal of a non-rocket spacedrive, but one that is rooted in unsolved questions in physics where there is a chance for new discoveries. Its theory led to a testable prediction that then evolved into an idea for a propulsive effect.
The unsolved physics question is: “What is the origin of inertial frames?” One attempt to answer that is called “Mach’s Principle” (term coined by Einstein to describe Ernst Mach’s perspective), which is roughly: “inertia here, because of matter out there.” The idea is that the phenomenon of inertia is an interaction between that mass and all the surrounding mass in the universe (presumed gravitational in nature). Jim Woodward picked up on a version of this from Dennis Sciama, and noticed that the inertial mass of an object can fluctuate if its energy fluctuates (think energy in a capacitor). That led to an idea for a propulsive effect by varying the distance between two fluctuating inertias. Unlike the EmDrive, this idea has been in the peer-reviewed literature from the beginning, with some of the more relevant papers being:
Woodward, J. F. (1990). A New Experimental Approach to Mach’s Principle and Relativistic Gravitation, in Foundations of Physics Letters, 3(5): 497-506.
Woodward, J. F. (1991). Measurements of a Machian Transient Mass Fluctuation, in Foundations of Physics Letters, 4(5): 407-423.
Woodward, J (1994), “Method for Transiently Altering the Mass of an Object to Facilitate Their Transport or Change their Stationary Apparent Weights,” US Patent # 5,280,864.
Woodward, J. (2012). Making Starships and Stargates, Springer.
Fearn, H. & Wanser, K. (2014). Experimental Tests of the Mach Effect Thruster. Journal of Space Exploration, 3: 197-205.
Martin Tajmar’s laboratory results can be summarized this way: False positive thrusts were observed under conditions where there should be no thrusting or only minor thrusting. More systematic checks have to be made prior to testing the thrusters at their nominal and maximum operating parameters. The mismatch was more pronounced for the EmDrive than for the Mach Effect Thruster. In both cases it is premature to reach definitive conclusions since this is a work in progress. And if any thrusters do pass all those tests, then more tests will commence to figure out how the thrusters operate (varying conditions to see which affect the thrust levels).
In the case of the EmDrive, only 2 W of the more normal 60 W of power was made available to the thruster. Even at that low power level, thrusts of about 4 µN were observed, which is more than the 2.6 µN expected from the claims from Sonny White’s tests. The more revealing observations were that thrusts were observed when the EmDrive was not supposed to be thrusting. When the EmDrive was pointed to a non-thrusting direction, thrusts were still observed. When the power to the thruster was sent to an attenuator to further reduce the power to the thruster by a factor of 10,000, thrusting at the prior level was still observed.
These observations do not bode well for the EmDrive’s claims of real thrust, but it is too early to firmly dismiss the possibilities. One suspect for the false positive is the interaction with the current to the device and the Earth’s magnetic field, where a current of 2-amps in a few cm of wires can produce a thrust in the µN range. Further tests are planned after adding more magnetic shielding and operating over different power levels.
In the case of the Mach Effect Thruster – which by the way, none of the press articles mentioned – the findings were less pessimistic. Again there were thrusts measured in excess of what was expected for the low power levels (0.6 versus 0.02 µN). Unlike the EmDrive’s mismatch, no thrust was observed when the Mach Effect Thruster was pointed to a non thrusting direction. There was, however, a case where the thrust direction did not change when the thruster direction was flipped. The suspected causes to be further investigated include both magnetic and thermal (expansion) effects.
A word of advice: if you plan to look at Tajmar’s paper. When I tried my usual “rush read” through the paper by reading the abstract and scanning the figures, I misled myself. Read the full text that accompanies the figures to know what you are really looking at. It’s a short article.
Regarding some representative press articles, here is a quick assessment
(1) David Hambling, New Study Casts Doubt on the “Impossible” EmDrive, But this weird propulsion idea isn’t dead yet
This one goes into more detail than the other articles about what was actually done and not done and does link to its information sources. It does not mention the Mach Effect Thruster.
(2) Mike Wall, ‘Impossible’ EmDrive Space Thruster May Really Be Impossible
This one mentions the doubt, but leaves the door open just a bit. Although it does not mention the Mach Effect Thruster also under test, it does at least give a link to the core article and mentions where it came from.
(3) Ethan Siegel, The EmDrive, NASA’s ‘Impossible’ Space Engine, Really Is Impossible: Many tests have reported an ‘anomalous thrust’ where there should be none. A researcher has finally shown where everyone else has messed up
This article talks more about the old claims and expectations than what was really in the new paper. It does not mention the Mach Effect Thruster.
(4) Mike Wehner, NASA’s ‘impossible’ fuel-free engine is actually impossible
More short-hand opinion, and again, no mention of the Mach Effect Thruster.
The takeaway: Science does not proceed by proclamation. Despite what headlines may say, laboratory work is a matter of refining techniques and bringing precision to bear on prior claims. At the moment, evaluation of the EmDrive and Mach Effect thruster continues, with no guarantee that either of these effects may prove genuine, but let’s let the process play out.
The Tajmar paper is Tajmar et al., “The SpaceDrive Project – First Results on EMDrive and Mach-Effect Thrusters,” presented at the Space Propulsion 2018 conference in Seville, Spain (full text).
by Paul Gilster | May 24, 2013 | Breakthrough Propulsion |
Tau Zero’s founding architect (and the former head of NASA’s Breakthrough Propulsion Physics project) weighs in on the kind of technology we see in the new Star Trek movie and ponders what it would take to make at least some of it real.
by Marc Millis
Another Star Trek film just hit the screen – with the venerable Starship Enterprise and its iconic warp drives and in-flight gravitation. How close are we toward realizing such a fantastic “Starship Enterprise”? How do such visions compare to other starflight pursuits? And finally, what is being done about it?
STARFLIGHT CHALLENGES AND OPTIONS
To send a spacecraft to our nearest neighboring star system (Alpha Centauri is over 4 lys distant) within a human lifespan would require a speed of roughly 1,000 times faster than the Voyager spacecraft. The two Voyager spacecraft were launched by NASA about 3 decades ago, and are just now passing through the edge of our solar system, at a distance of roughly 1/500th of a light year.
To increase speed by a factor of 1,000 requires at least 1,000,000 times more energy, and then at least twice more if you want to stop at the destination. And think about the researchers left behind on Earth, the people who build the equipment and the experiments aboard the starship. Considering that a human lifespan is about 100 years (rough orders of magnitude), they’ll be able to track a mission only out 80 light years or so even if it’s moving close to lightspeed. While that might be enough to reach a habitable planet (whose closest distance estimates span roughly 25-ly – 200-ly), the provisional estimates to reach the nearest civilizations (if there are any) are between 500-ly – 6000-ly. [Click for more destination info]. To reach these more profound destinations within the lifetime of the starship builders back home requires either faster-than-light (FTL) flight, or a much longer human lifespan.
Image: Star Trek‘s Enterprise, an icon of breakthrough propulsion. Credit: The Light Works (www.thelightworks.com).
Absent FTL flight, most starflight researchers explore probe missions based on foreseeable technology. Armed with estimates of what might be ultimately feasible within existing physics, they determine what further technological advancements would be needed to enable meaningful missions. Early projections suggest that probe missions with flight times of only decades might be possible. To develop that technology and to prepare the supporting systems to collect the energy to launch such missions, however, might take several decades or centuries. Those estimates vary wildly depending on which conclusion is being advocated.
When considering human interstellar flight, the prominent concept is to build self-sustaining world ships that can support many generations of humans on their slow journey to eventually reach habitable planets to colonize, or to just coast through space as isolated pockets of humanity. Not much work has progressed toward this theme, since we still do not know the minimum number of colonists required and the minimum life support to keep them going… including what societal structure can sustain peace and satisfying lives in such isolation for so long.
And finally, for those that want to reach “new worlds, new life, and new civilizations” within short attention spans, further physics advances are required. This includes FTL flight and other breakthroughs typical of the Star Trek visions. This motivation includes the desire to usher in a whole new era of profound technological prowess – new technologies enabled by further advances – targeted advances – in physics. Some have characterized this last approach like the crazy uncle who indulges in wild dreams and playful tinkering.
At this stage it is too early to objectively determine which of these pursuits is ‘best,’ in large part because there is no definition of ‘best.’ The motivations, pros and cons are so varied, and the hard facts still so uncertain, that the choice is more based on personal preference. From those I know who work on these, they seem to pick the version that they, as individuals, can contribute the most to making them happen.
Note – the Build the Enterprise website is not about a true starship, but rather something that just looks like the Enterprise with far, far less capabilities. If you are seeking the realization of the Enterprise, keep reading.
FANTASTICAL STARFLIGHT REQUIREMENTS
Star Trek made starflight look easy and other inspiring fiction contributed to our yearnings. According to Jeff Greenwald, in his 1999 book, Future Perfect, about how Star Trek affected people around the world: “… it fulfills a deep and eternal need for something to believe in: something vast and powerful, yet rational and contemporary. Something that makes sense.”
An important element of Trek that went beyond technology is its society: creating a cooperative culture that can harness the power of starflight without killing themselves in the process. In reality, when considering the potency of the energy required for real starflight, this is critically important. This subject could be book unto itself, and why societal and human aspects are an integral part of contemplating real starflight. Personally, I am concerned that this challenge might turn out to be harder than creating new physics for warp drives and controlling gravity.
Back now to the inspiring spaceflight physics. For fun, and to appeal to a wider fan base, here is a composite of some of the biggest visual inspirations for starflight, our “2001 Millennium Enterprise, C57-D.”
Image: The “2001 Millennium Enterprise, C57-D”, a kludge of favorite fictional vehicles: two alien slabs (with FTL transport capability) from 2001, A Space Odyssey; the 1966 Star Trek Enterprise; the 1977 Millennium Falcon (Star Wars); and the 1956 saucer ship C57-D from Forbidden Planet. Graphic courtesy of Aldo Spadoni, 2013, based on a rough sketch from Millis.
Regardless of your favorite fiction, when it comes to enabling such fantastical star flight, here is what we need:
(I) Faster-than-light (FTL) engines: Compared to the distances between stars, lightspeed is actually slow. It takes years for light to travel the distance between stars. Our nearest neighboring star system (Alpha Centauri) is over 4 years away at lightspeed. The nearest habitable planet might be anywhere from 25-ly to 200-ly distant. And to consider meeting new aliens for each week’s episode, our ship would need a naive cruise speed of at least 25,000 times lightspeed. The word ‘naive’ is used here to remind us that we don’t really know what happens to time and space beyond lightspeed. For traditional slower-than-lightspeed flight, Special Relativity tells us what to expect about our perceptions of time and length changes as we get closer to the lightspeed limit.
(II) Control of gravitational and inertial forces: This is a hugely important feature that often gets neglected in shadow of FTL. It is so ubiquitous in science fiction that many people do not even realize it’s there and it has breakthrough implications – plus it does not yet have a cool-sounding name to convey its essence. Picture your favorite fictional starship – where the crew is walking around normally – as if in a studio back on Earth. This means that the ship is providing a gravitational field for the comfort and health of the crew – in the middle of deep space where such fields do not exist. This would be a profound breakthrough!
But wait, there’s more. Given this ability to create acceleration forces inside a spacecraft, it is not much of a leap of imagination to suggest that acceleration forces could be created outside the spacecraft too – thus propelling the spacecraft. This too – a non-rocket space drive – would be a profound breakthrough.
But wait, again there’s more. The physics of being able to manipulate gravitational and inertial forces also implies the ability to have “Tractor Beams” for moving distant objects, and the ability to sense properties of spacetime that we cannot yet even fathom.
(III) Unprecedented energy storage and power usage: Last on our list of top requirements is having enough energy onboard to power our magical FTL engines and space drives. On Star Trek, they use matter-antimatter to provide energy (which is existing physics), by fully converting matter into energy. Think Einstein’s E=mc2. Our fantastical spacecraft – and even some of the technological versions – will need at least that much energy.
ARE WE THERE YET?
In the book The Physics of Star Trek, physicist Lawrence Krauss compared the visions of Trek to contemporary physics. But it did not go far enough. It only compared the methods of Trek to the physics, rather than the overall requirements, and it did not suggest what we can do about it today.
Progress toward Trek-like ambitions is actually being made. Notions of controlling inertial and gravitational forces, plus FTL flight, ceased to be just science fiction decades ago. Here is that legacy of some of pertinent publications:
1963 Induced Gravitation: Forward, R. L. “Guidelines to Antigravity,” in American Journal of Physics, Vol. 31, p. 166-170.
1988 Wormholes: Morris, M. S. & Thorne, K. S. “Wormholes in spacetime and their use for interstellar travel: a tool for teaching general relativity,” American Journal of Physics Vol. 56, p. 395-412.
1994 Warp Drives: Alcubierre, M. “The warp drive: hyper-fast travel within general relativity,” Classical and Quantum Gravity 11, p. L73-L77.
1997 Space Drives: Millis, M. G. “Challenge to Create the Space Drive,” AIAA Journal of Propulsion & Power 13(5), pp. 577-582.
2004 Quantum Vacuum Propulsion: Maclay, J. & Forward, R., “A Gedanken spacecraft that operates using the quantum vacuum (adiabatic Casimir effect),” Foundations of Physics 34(3), p. 477 – 500.
2009 Compilation of Approaches: Millis, M. G. & Davis, Eric. W., Frontiers of Propulsion Science, Vol. 227 of Progress in Astronautics and Aeronautics, (AIAA).
To be clear, this does not mean that these breakthroughs are on the threshold of discovery. What is does mean is that these notions have advanced to where they are now attackable problems. In terms of the scientific method, the first step of ‘defining the problem’ has been completed, the second step of ‘collecting relevant data’ is underway, and some ideas have even matured as far as testing hypotheses.
For those who can handle a graduate-level treatise, the first scholarly book on the topic (scholarly means peer-reviewed, objective, with equations and with traceable citations) was compiled by myself and co-editor, Eric W. Davis, with the help of over a dozen contributing authors, and so many reviewers that I can’t remember. In 2009, this book, Frontiers of Propulsion Science, was published as part of the Progress in Astronautics and Aeronautics series of the American Institute for Aeronautics and Astronautics (AIAA).
For those who want just the executive level summary, here are short descriptions, along with some notes about continuing work. I’ve attempted to convey this sanely, between the extremes of sensationalist hype and pedantic disdain:
• Faster-than-Light Flight: Wormholes and Warp Drives are theoretically possible, but our theory is not yet advanced enough to guide their actual construction. These theories are based on, and consistent with, Einstein’s General Relativity. The ongoing progress (I rely on Eric W. Davis to track this for Tau Zero) mostly focuses on the energy conditions – how to lower the energy required and how to create and apply the required ‘negative energy.’ One conclusion already is that Wormholes are more energy-efficient at creating FTL than the Warp Drive. A recent account of those details is available as:
Eric W. Davis, “Faster-Than-Light Space Warps, Status and Next Steps,” paper AIAA 2012-3860, 48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, Atlanta, GA, (January 9-12, 2012) (abstract).
Recent news about the work of Harold “Sonny” White at NASA’s Johnson Space Center has been a bit exaggerated, but the essence of the work is that it is an attempt to measure spacetime distortions caused by the presence of negative energy. Unfortunately, I do not have an article to cite about that hypothesis or the methods being used, since such information has not (yet?) been published. Although Eric Davis is tracking this for Tau Zero, even he does not yet know enough to render judgment. We shall have to wait and see, and hope that the information is submitted for rigorous review.
Additionally, Quantum Physics presents some tempting phenomena that might be relevant to FTL pursuits. A number of phenomena, such as ‘tunneling’ and ‘entanglement’ fall under the header of “quantum non-locality” – a term I learned from physicist John Cramer at the University of Washington, Seattle. That term encompasses the notion that quantum events or phenomena can exist over more than one place at the same time. Cramer’s attempt to test the possible time-paradox implications of such phenomena still remains incomplete. The last update I saw was this publication:
J.G. Cramer, K. Hall, B. Parris, and D.B. Pengra, “Status of nonlocal quantum communication test”, Section 7.2, Univ. Washington CENPA Annual Report 2010-2011, April 2011, pp. 94-95.
But wait, still again there’s more. The hot topics of Warp Drives, Wormholes, and ‘Retrocausal Signaling’ are not the only ways to ponder FTL, but they are the only ones in the peer-reviewed literature, so far. For the budding pioneers amidst us, here is a breakout of other ways of pondering FTL:
Image (click to enlarge): This diagram points out that there is more than one way to ponder FTL. The items in blue boxes are already in the scientific literature, while the remaining green boxes are some of the playful speculations we have heard along the way. Credit: Marc Millis, from the Tau Zero Foundation site.
• Controlling Inertial and Gravitational Forces (in-flight gravitation for crew comfort, maneuvering the ship without rockets, tractor beams, etc.): More than one way to generate acceleration fields has been published and both methods are theoretically consistent with Einstein’s general relativity [Forward’s 1963 paper cited earlier, and the Levi-Civita effect]. Both of these have daunting theoretical and implementation challenges, similar to Warp Drives and Wormholes.
Similar to the FTL work, there is more than one way to approach this challenge, as shown in this graphic:
Image (click to enlarge): There is more than one way to ponder how to create a space drive, and these have been sorted by the physics discipline in which each is based. The items in red boxes have been reliable shown to be dead-ends. Credit: Marc Millis, from the Tau Zero Foundation site.
The details behind this diagram, and the next-step research of each approach are available in:
Marc Millis, “Space Drive Physics: Introduction & Next Steps,” JBIS 65, pp. 264-277 (2012). Abstract available.
This is the area that piques my interest, more specifically the “Space Coupling Propulsion” block in that diagram above. I’ve been working on grant proposals to get that work supported – which involves going back to old works of Eddington and Mach, and scalar potentials where relativity is cast in terms of retarded potentials. For those of you who do not speak that level of geek – I’m trying a different approach to understand the coupling between spacetime (inertial frames) and electromagnetism. The work involves the design and test of new sensors, based on those older perspectives.
• Ample On-board Power: Nuclear power is a technological reality now that, if used for spaceflight, would greatly increase the extent of space activities. The power levels required for interstellar flight, even slower-than-light, are still beyond the accrued prowess of humanity, but optimistic trends suggest they might be achievable sooner than later. The power levels required for faster-than-light (FTL) were once astronomically high, but those values have dropped with continued research to where they are now just fantastically daunting.
Are there new ideas to harness vast amounts of energy? There are credible theoretical and experimental approaches to improve our understanding of “quantum vacuum energy,” but this field is still too young to have developed plausible methods of ample energy exchange. What is possible are miniscule energy conversions when dealing with small electrodes. Today, these serve as good tools to empirically explore this young topic in physics, but are not close to suggesting how to achieve the kind of energy levels needed for FTL flight — levels that might be impossible to achieve..
WHAT YOU CAN DO ABOUT IT
If you want to become a practitioner in pursuit of Star Trek-ish spaceflight, you will need a degree in physics, a vivid imagination, steady rigor to work through the details and persevere through the setbacks, and the personal savvy to navigate amidst a world more interested in short-term returns, and sometimes even back to reruns.
For those who would rather support from the sidelines, Tau Zero will gladly accept donations and is now also open for memberships. If, by some chance, you are a generous philanthropist reading this and wondering if we have what it takes to run a whole program around this theme, the answer is “Yes.” I led the NASA project toward such ambitions, including developing the process to sort through proposals to avoid the detriments of pedantic dismissals and the lunatic fringe. Those details are in the last chapter of our Frontiers of Propulsion Science book. We have a network of qualified practitioners who would gladly assist, even if only for a modest honoraria. And if you are a researcher hoping to find funds for this topic, please let us know if you find any. As yet, we do not have enough funds to invite proposals.
Lastly, I should alert you that there are scams out there on these topics. Rather than risk the legalities of explicit names, please take this advice: If they claim amazing performance – don’t believe it. If they offer no test data to back up their claims, ignore them. If the data they offer has not been independently scrutinized, then look elsewhere. Conversely, the promising signs to look for include: The service providers have a track record of confronting these edgy issues in a manner where increments of progress are published in peer-reviewed journals. Quality practitioners are as open to the possibilities that an idea may or might not work, with the emphasis on getting a reliable answer, instead of hyping the claims or being dismissive.
CONNECTING THE DOTS – ONE VISION
This topic is at such an early stage that it is difficult to project into the future to see how these small steps might lead to the desired breakthroughs. To help fill this gap, I have leaped (below) into wild speculation and conjecture – science fiction, if you will.
First: a dose of reality. Consider how nature has been throwing us curve-balls regarding our physical understanding of space and time. Rotating galaxies do not obey Newton or Einstein, but rather these galaxies hold together as if some “dark matter” is keeping their stars within the galaxies. Next, when viewing our most distant spacetime, we see redshifts that suggest that spacetime is expanding faster than theory – as if some “dark energy” or “antigravity force” were accelerating the expansion of spacetime. Quantum physics, with its incredible predictive power and practical utility, also presents us with oddities like the quantum vacuum energy and non-locality. And finally, consider the Cosmic Microwave Background Radiation, whose properties let it serve as an absolute reference frame for motion relative to the mean rest frame of our Universe. This phenomenon is at odds with assumptions that the Michelson-Morley experiment and the very successful Special Relativity seemed to dismiss the notion of an absolute electromagnetic reference frame. In short, physics is not complete. New discoveries await – discoveries that might open the way for whole new classes of technology.
Now, armed with those uncertainties, consider that other perceptions about the relations between space, time, inertia, and electromagnetism might match nature better. For example, what about the older notions of inertial frames from Mach, Eddington’s other way of describing why light bends in a gravitational field, and the retarded potential perspective of deducing magnetism as a relativistic effect of moving charges. By combining these, it might be possible to first detect, and then induce, perturbations of inertial frames. Such transducers – which convert changes in inertial frames into electromagnetic energy – could reveal new phenomena, new waveforms within inertial frames. Those observations then lead to reversing that conversion – where electromagnetic energy is used to perturb inertial frames – creating momentary gradients that move matter.
This ability would be the beginnings of tractor beams and space drives. From there, imagine when those effects get strong enough to create 0-g recreation rooms on Earth, or 1-g habitats for long-duration, deep spaceflight. Powerful enough devices, ‘space drives,’ could propel spaceships faster and faster. As higher speeds are achieved, experiments to test various FTL theories could commence. Perhaps, just one of those theories might lead to the first FTL transport. And finally, with the combination of non-rocket space drives, cabin gravitation for the crew, and light speed travel… we would have our Enterprise.
Ad astra incrementis
Help us start taking some small risks, today, that might eventually escalate to fantastic starflight – enabling humanity to survive and thrive across the galaxy.
by Paul Gilster | Sep 4, 2009 | Breakthrough Propulsion |
Both Tau Zero Foundation founder Marc Millis and JPL’s recently retired Robert Frisbee appear in an article in the Smithsonian’s Air & Space, where voyages to distant places indeed are discussed. Nothing is further from Earth, the article notes, than Voyager 1, which travels at a speed (almost 17 kilometers per second) that would get it across the US in a little under four minutes. Point that spacecraft toward Proxima Centauri and the journey at this speed would take 73,000 years. Clearly, something has to give, and writer Michael Klesius runs through the options.
From Ideas to Engineering
Voyager is actually headed in the vague direction of the constallation Camelopardalis, and won’t come near anything stellar in several hundred thousand years. We’d like to get mission times to a nearby star down to decades so that scientists and engineers working on the project could live to see its outcome.
How to achieve that is a question that has been at the back of Bob Frisbee’s mind for a long time now. To Alpha Centauri in just decades? Years? “We can see the theoretical possibilities of these things happening, but we just can’t get the engineering there,” Frisbee notes in the article, but he points out that this kind of brainstorming was what we used to do when thinking about a moon voyage, and that was a journey we made. It may take several generations of brainstorming but the ideas continue to fly.
Building a Breakthrough Concept
Let’s hope the Air & Space article provokes public discussion as it runs through the background of advanced propulsion studies in the 1990s, when wormholes were seriously tackled and warp drive began to be written up in scientific journals. Miguel Alcubierre’s concept of a spacecraft riding what is essentially a wave in spacetime kicked off a resurgence in breakthrough propulsion that led materially to projects like NASA’s Breakthrough Propulsion Physics, run by Millis until its termination in 2002. Funding issues are always problematic, but Tau Zero continues to probe these matters, and Frontiers of Propulsion Science, co-edited by Millis and Eric Davis, shows that the ongoing conversation is robust indeed.
Says Millis:
“I think back to the era of Dirac and Schrödinger and Einstein. When they were having their pivotal meetings and sometimes heated debates, they weren’t being funded for that work. They were just doing it because that’s what they did. And they made significant advances… And I’m thinking to myself, Well, it would be great if we got funding, but even if we don’t, when we talk amongst ourselves and debate things and encourage each other to write papers, we’re going to make progress.”
That kind of progress is what Tau Zero is about. Not that robust funding is out of the picture — we are building a philanthropic model for the foundation that should be able to tap private sector sources (with all the good things that follow from not being channeled through endless layers of bureaucracy). But keeping an eye on the issues and encouraging debate is bound to produce good outcomes, if only in the synergies that result from putting propulsion theorists with good ideas in continuing contact.
Options for Infrastructure
But before we go to the stars, we’ve got to build up our capabilities right here in the system. On that score, the article is also noteworthy for its examination of NERVA, a nuclear thermal rocket design that Klesius describes this way:
It would produce thrust the way chemical rockets do: by heating a propellant—in this case, hydrogen—and ejecting the expanded gas through a nozzle. Instead of heating hydrogen through combustion, however, the nuclear rocket vaporizes it through the controlled fission, or splitting of atomic nuclei, of uranium. Because nuclear fuel has a greater energy density, it lasts a lot longer than chemicals, so you can keep the engine running and continue to accelerate for half the trip. Then, with the speedometer clicking off about 15 miles per second — twice the speed reached by returning Apollo astronauts — you’d swing the ship around to point the other way and use the engine’s thrust to decelerate for the rest of the trip. Even when factoring in the weight of the reactor, a nuclear engine would cut the transit time in half.
NERVA was a promising technology that delivered 850 seconds of thrust — twice the efficiency of chemical rockets — in 1960s-era tests, but the program faded in the 1970s. You’ll find more on NERVA, and on Franklin Chang-Díaz’ work on VASIMR, in Klesius’ article. Neither NERVA nor VASIMR has interstellar potential, but in terms of opening up the Solar System for exploration and infrastructure building, these are solid options to investigate.
An Insurance Plan for Human Survival
I like the Chang-Díaz quote that ends the piece:
“The space program began the day humans chose to walk out of their caves. By exploring space we are doing nothing less than insuring our own survival.”
Indeed. And all the technologies described here point to ways of making the insurance policy pay big dividends. Klesius writes about a fusion-powered 180-day trip to Jupiter, one dependent on breakthroughs in fusion itself and in materials science. Build the infrastructure here in the Solar System and gradually push the envelope outwards. It’s a plan that could pay off one day in making that journey to Proxima Centauri via fusion, antimatter or other means, and crossing the gulf in a single human lifetime.
by Paul Gilster | May 5, 2009 | Breakthrough Propulsion |
Wired has picked up on our Frontiers of Propulsion Science book with just published interviews of Marc Millis and Eric Davis, co-editors of the volume. Interviewer Sharon Weinberger had a tough assignment, dealing with a 739 page collection of technical and scientific papers aimed, as she notes, at scientists and university students. But her questions were well chosen, particularly in drawing out why a book like this was necessary.
Defining the Terms
Marc Millis, founder of the Tau Zero Foundation, noted the need for a single, defining reference point outlining the current status of research and the opportunities presented. Thus the motivation:
To clear the way for progress, my colleagues and I decided to compile this one document covering the status, issues, and unresolved questions behind a variety of known concepts, and to link the ideal goals back to real physics details. To the extent possible, we endeavored to treat these subjects impartially; showing both their visionary relevance and their critical issues.
All of this is in the context of building a base for future work more than hawking the merits of any particular approach. Moreover, advanced propulsion studies needed a volume that identified the founding references that later work could build upon:
The intent was to create a document that other researchers could use as a reliable starting point for productive research – chipping away at the issues and unknowns that might one day enable practical interstellar flight.
The book emerges into an environment where the decision to re-play Apollo has seen cutbacks in the kind of fundamental research pursued by projects like Breakthrough Propulsion Physics, which Millis once headed at NASA. The situation is not new. Three times more private funding went into propulsion physics research in the late 1990s, Millis notes, than was supplied by government. The trick now will be to encourage private initiatives to publish their results widely, for the benefit of the entire community.
Rigorous Concepts, Testable Hypotheses
These are thorny matters in a field as prone to exaggerated claims as cutting-edge propulsion, but high-quality research that engages the scientific community through peer-reviewed journals is out there. Eric Davis notes the need for rigorous, lab-tested concepts of the sort he pursues at the Institute for Advanced Studies at Austin, and also as CEO of Warp Drive Metrics:
…there is no general hesitancy toward conducting experiments by scientists. There is a larger question that looms in this regard: “Does a particular concept have a rigorous hypothesis or theory worth testing in the lab?” This question addresses whether any concept is testable. According to the scientific method, experiment must be driven by hypothesis, or in absence of a hypothesis, one uses laboratory empirical studies to produce a hypothesis. There are an enormous amount of concepts floating around out there and most of them do not have a testable hypothesis. That makes it very difficult for any serious scientist to justify doing experiments.
Even those ideas that make the grade of testability can fail the test, as some of the concepts examined in Frontiers of Propulsion Science make clear. A serious-minded inventor with a breakthrough in mind will, if confronted with such evidence, go back to figure out where the problem is. But not everyone takes the scientific method so seriously, Davis notes:
Often, however, the inventor holds on to his original belief, attacks the independent evaluation process as being flawed, and continues to hype his claim, a sure indicator of the pathological science position that is not self-corrective. In this case, as time passes and no positive contribution to the energy field emerges, the process of independent evaluation becomes more and more appreciated as unbiased.
In Search of a New Model
Getting fewer sales pitches and more credible research is what interstellar studies needs, which is why Frontiers of Propulsion Science stands out (in the interest of transparency, I should note that I wrote the first chapter of this book, so consider me an interested party). Where we go next seems clear. NASA did support the compilation of Frontiers, but that was its last contribution to such research, with further support withdrawn as of October of last year. Now we turn elsewhere. A growing commercial space sector gives hope of private funding to support rigorous research. Driving the attempt is not, as Millis notes, the kind of Cold War tension that boosted Apollo, but today’s understanding that the very habitability of Earth is endangered.
Is the answer to Fermi’s ‘Where are they?’ question that technological civilizations simply cannot survive their growing pains? A culture unable to muster its defenses against space-borne impactors, facing the ever-present prospect of future war with advanced weaponry and contemplating environmental change may well wonder if survival is possible. Basic research into the options for getting off-planet is the kind of insurance policy it should create, if not governmentally, then by private initiative.
And that, in support of Tau Zero, is why this site continues.
by Paul Gilster | Jul 5, 2007 | Breakthrough Propulsion, Exotic Physics |
A mission to another star is quite a jump for today’s technologies and will be for some time to come. But if you’re thinking of robotic payloads rather than human, it’s at least in the range of possibility. Fast ‘Sun-diver’ trajectories that could get a fly-by probe to Alpha Centauri in something on the order of a thousand years are not beyond question, and Robert Forward-style lightsails, pushed by gigantic lasers, might reduce that time to a century or less, using a Solar System-wide infrastructure we might be able to build with the help of nanotechnology in the next century.
Human crews, though, are quite another matter. The problem seems to demand breakthrough technologies, one of which could be the propellantless propulsion being investigated by James Woodward (California State University, Fullerton). The vast amounts of propellant needed for chemical or even nuclear missions seem to rule out their use in practical crewed spacecraft. A propellantless thruster would resolve the issue, but most theorists think that producing acccelerating forces without expelling some kind of propellant mass from the vehicle is an idle dream.
On the other hand, we learn things by finding out just what the problems are — in this case, the distances to be traversed, and the time involved — and then asking what breakthroughs would be needed to surmount them. Our experiments to probe breakthrough concepts may lead to further solutions we hadn’t ever thought of. And if the work of a James Woodward, recently considered in these pages, ultimately fails, it will still offer the chance to confirm our existing understanding of physical laws and perhaps broaden our views of what is and is not possible.
Those who have asked for more information about Woodward will also want to know about the investigations of Hector Brito (Instituto Universitario Aeronautico, Cordoba, Argentina) and colleague Sergio Elaskar (CONICET, Universidad Nacional de Cordoba). In a recent paper, the researchers describe their experiments with what they call an electromagnetic inertia manipulation (EMIM) thruster, producing what they believe is experimental evidence of sustained thrust using concepts not dissimilar to those championed by Woodward.
After describing their device, the authors present the principle behind it:
By Minkowski’s formalism, a nonvanishing momentum of electromagnetic origin is shown to arise for the particular device… It follows that the EM field can modify the inertial properties of the generating device, their variation producing forces on the device without any exchange of mass-energy with the surrounding medium. A propulsion concept based upon this kind of inertia manipulation mechanism was subsequently drawn; an electromagnetic inertia manipulation (EMIM) thruster was engineered up to the “proof of concept” level. Experiments were designed and performed, yielding by spectral analysis techniques, in an exploratory phase, indirect evidence of Minkowski’s approach being valid.
Brito and Elaskar then go on to modify the experiment, producing what they call “…sharper and clearer evidence of sustained thrust…” Work like this depends crucially on filtering out the signal from the noise, so that tiny effects that might be construed as thrust aren’t confused with myriad side-effects caused by the apparatus itself. The paper studies such effects in a series of experiments, with results the authors consider provocative:
Tests performed during an exploratory phase produced results, which after intensive data processing gave indirect evidence of matter-electromagnetic field momentum exchange, as predicted by Minkowski’s formalism; direct detection of the sought effect could not be achieved due to interfering effects leading to very low S/N ratios. Sustained thrust experiments based on an alternative formulation of the EM force densities were devised and performed, aiming at getting rid of most of the identified spurious effects. They yield sharp and clear evidence of force-producing effects as predicted by that formulation, albeit in contradiction with null results predicted by the standard formulation.
Are Brito and Elaskar (and, by extension, Woodward) on to something, or are they mistaking mechanical noise for thrust? I tend to agree with Bob Shaw that there is no such thing as a free launch, but we’ll see. The uncertainties are numerous, with the researchers noting how extensive is the work necessary to confirm their results, including (one day) in-orbit testing. Right now we’re a long way from that, or from understanding the principles underlying such anomalous effects, if they are indeed genuine.
The paper is Brito and Elaskar, “Direct Experimental Evidence of Electromagnetic Inertia Manipulation Thrusting,” Journal of Propulsion and Power Vol. 23, No. 2 (March/April 2007), pp. 487-494. Many thanks to Joseph Mahaney for getting a copy of this paper to me.
