Impacts Spreading Life through the Cosmos?

by Paul Gilster on May 25, 2012

Still catching up after the recent series on antimatter propulsion, I want to move into some intriguing work on panspermia, the idea that life may spread throughout a Solar System, and perhaps from star to star, because of massive impacts on a planetary surface. Catching up with older stories means leaving some things unsaid about antimatter — in particular, I want to return to the question of antimatter storage, which in my mind is far more significant a problem even than antimatter production. But there’s time for that next week, and as I said yesterday, interesting stories keep accumulating and deserve our attention.

Planetary Ejecta and Trapped Microorganisms

What Tetsuya Hara (Kyoto Sangyo University) and colleagues put forth in a recent paper are their calculations about the ejection of life-bearing rocks and water into space from events like the possible ‘dinosaur killer’ asteroid impact some 65 million years ago, which involved an asteroid 10 kilometers in diameter. It’s a remarkable fact that materials can be knocked off one planetary surface and wind up on another, and in some quantity. Consider, for example, the 100 or so meteorites identified by their isotopic composition as being from Mars. They show marked similarity in chemical composition to Viking’s analysis of Martian surface rocks in 1976, and trapped gases in some closely resemble the Martian atmosphere.

So planets in the same system can exchange materials, and of course the Allan Hills meteorite found in Antarctica (ALH 84001), thought to have been ejected from Mars about 16 million years ago, caused quite a stir back in 1996 when scientists thought they had found evidence for microscopic fossils within it, an analysis that remains controversial. But whether or not ALH 84001 contained life, the discovery of various kinds of extremophiles here on Earth and the possibility that they could survive for long periods trapped in rocky debris leads to the idea that one world can seed another, and as we’ve seen in earlier posts on the topic, the idea goes back as far as the Greek philosopher Anaxagoras, with a revival of interest in the 19th Century.

Fred Hoyle and Chandra Wickramasinghe, who were proponents of continuing panspermia and the idea that life entering Earth’s atmosphere from outside could be a driver for evolution, would doubtless find Hara and team’s work fascinating. While the latter argue that solar storms could eject microbes from the upper atmosphere into space, they concede that bolide impacts would be the major driver:

Naturally, those meteors, asteroids or comets which strike with the strong force, would eject the most material into space. Thus it could be predicted that the asteroid or meteor which struck this planet 65 million years ago, and which created the Chicxulub crater (Alvarez. et al. 1979) would have ejected substantial amount of rock, soil, and water into space, some of which would have fallen onto other planets and moons, including stellar bodies outside our stellar system, Kuiper belt objects, Oort cloud objects, and possibly extrasolar planets…

And there’s the issue — just how much material would actually be transferred not just into the outer Solar System, but to nearby stars? Hara uses the Chicxulub crater event as the model for the kind of collisions that drive Earth materials into space, estimating that about the same amount of mass would be ejected from Earth as arrived in the original asteroid impactor.

Long Journey into the Dark

Remarkably, almost as much of the ejected materials make the journey to Europa as to our own Moon, an interesting outcome explained by Jupiter’s deep gravitational well, which in this case takes possibly biologically-laden material to a moon that contains an under-ice ocean. Another place of high astrobiological interest is Saturn’s moon Enceladus, with an internal body of water of its own, as evidenced by the geysers Cassini continues to monitor around its south pole. Here the numbers drop considerably but as many as 500-2000 Earth rocks may have reached Enceladus. Even distant Eris in the Kuiper Belt scarfs up 4 x 10⁷ Earthly objects in one scenario.

These numbers vary according to which of two models the authors use, but in either case their figures show significant movement of Earth materials into the outer Solar System. Extending the model to Gliese 581 becomes a fascinating exercise because we have reason to believe that the ‘super-Earth’ Gl 581d may orbit in the outer edges of the habitable zone there. The result: As many as 1000 rocks may have made the million year journey to fall upon a planet in the Gl 581 system. Thus we have the possibility, however remote, of dormant microorganisms moving between one stellar system and another, to fall upon a planet that conceivably can support life.

Hara and team acknowledge the uncertainties in their calculations but insist that “…the probability of rocks originated from Earth to reach nearby star system is not so small.” If this is the case, their conclusion points to the possibility that life did not originate on Earth at all:

We estimate the transfer velocity of the microorganisms among the stellar systems. Under some assumptions, it could be estimated that if origin of life has begun 10¹⁰ years ago in one stellar system as estimated by Joseph and Schild (2010a, b), it could propagate throughout our Galaxy by 10¹⁰ years, and could certainly have reached Earth by 4.6 billion years ago (Joseph 2009), thereby explaining the origin of life on Earth.

This assumes that there are 25 sites where life began 10¹⁰ years ago, with biological materials spread through the galaxy by the same kind of impact events that caused the Chicxulub crater. Add to this recent work by Brandon Johnson (Purdue) and colleagues. They’ve been investigating layers of rock droplets called spherules, which may tell us better than craters about ancient impacts, including the size and velocity of the impacting object. An initial reading of their work shows that the Late Heavy Bombardment, thought to have occurred from 4.1 billion to 3.8 billion years ago as huge numbers of asteroids and comets hit the Earth, may have lasted longer than we have previously believed.

Was Chicxulub relatively minor compared to the size of some of these impacts? Evidently so, which would account for even more materials from our planet being pushed out into nearby space. The wild card in all this is the ability of microorganisms to survive not just the impact but the journey, and when it comes to interstellar panspermia, my own credulity is pushed to the breaking point. Although I’m running out of time this morning, I want to return to two papers in Nature that examine the Late Heavy Bombardment and the history of later impacts on our planet. We’ll home in on evidence for a longer bombardment era when Centauri Dreams returns on Monday.

The Hara paper is “Transfer of Life-Bearing Meteorites from Earth to Other Planets,” Journal of Cosmology 7 (2010), p. 1731 (preprint). Thanks to John Kilis for the original pointer to Hara and an update on the Nature work.

Disruptive Planets and their Consequences

by Paul Gilster on May 24, 2012

One of the joys of writing a site like Centauri Dreams is that I can choose my own topics and devote as much or as little time as I want to each. The downside is that when I’m covering something in greater depth, as with the four articles on antimatter that ran in the last six days, I invariably fall behind on other interesting work. That means a couple of days of catch-up, which is what we’ll now see, starting with some thoughts on a possible planet beyond Neptune, a full-sized world as opposed to an ice dwarf like Pluto or Eris. This story is actually making the rounds right now, but it triggered thoughts on older exoplanet work I’ll describe in a minute.

It’s inevitable that we call such a world Planet X, in my case because of my love for the wonderful Edgar Ulmer film The Man from Planet X (1951), in which a planet from the deeps wanders into the Solar System and all manner of trouble — including the landing of an extraterrestrial on a foggy Scottish moor — breaks out. Of course, Planet X was also the name for the world Percival Lowell was searching for in the 1920s, a hunt that resulted in Clyde Tombaugh’s discovery of Pluto, although the latter occurred more or less by chance since Pluto/Charon isn’t big enough to cause the gravitational effects Lowell was examining.

So is there a real Planet X? Rodney Gomes (National Observatory of Brazil) has run simulations on the ‘scattered disk’ beyond Neptune and, factoring in oddities like the highly elliptical orbit of Sedna and other data points on these distant objects, Gomes believes a Neptune-class planet about four times as massive as Earth may be lurking in the outer system. Sedna, you may recall, has a perihelion of 76 AU but an aphelion fully 975 AU out — it’s on a 12,000 year orbital period! As for Gomes, his team has been looking at what they call ‘true inner Oort cloud objects’ for some time, seeing objects like Sedna as markers for the existence of a planet.

Gomes ran through the results of his simulations at an American Astronomical Society meeting in Oregon in May, keeping the Planet X hunt alive, and it’s worth noting that a Jupiter-class planet at about 5000 AU may also fit the bill (see Finding the Real Planet X). For that matter, the orbits of scattered disk objects may have another explanation besides an undiscovered planet. But thinking about Gomes’ work brought me around to Jason Steffen and team, whose new paper goes to work on a much different kind of gravitational effect, the disruption caused by a ‘hot Jupiter’ as it moves through a young Solar System and scatters smaller planets.

Realm of the Wandering Planets

Steffen (Fermilab Center for Particle Astrophysics) is digging into exactly what makes ‘hot Jupiters’ take up such extreme orbits. These are planets of Jupiter’s size and larger that whip around their stars in periods of just a few days. The question is how they got to their present position, for the assumption is that planets of this size had to form much further out in their system and then move inward. There are two mechanisms that could make this happen, one of which — a slow migration through a gas disk that would allow low-mass planets to likewise migrate inward, where they can be captured into mean-motion resonance with the gas giant — seems benign. These models suggest the presence of smaller worlds near the hot Jupiter.

The other model is lethal to the inner system. Here, the giant planet’s migration is caused by gravitational interactions with another gas giant that result in one of the worlds being flung into interstellar space, while the other migrates inward and disrupts the orbits of any inner-system worlds. This scenario is what the Steffen paper is suggesting, for the team’s analysis of 63 Kepler planets around solar-type stars in orbits of 6.3 days or less shows no evidence at all for nearby planets. If such worlds were there, they ought to be detectable through transit timing variations (TTV) unless they are smaller than the Earth, or much further out in the system.

To compare and contrast environments, the researchers took another sample of 31 Kepler planets with ‘warm Jupiters’ — planets of Jupiter size around the same kind of star, but with longer orbital periods of between 6.3 and 15.8 days. They also checked 222 Kepler ‘hot Neptunes.’ The result: Three of the 31 ‘warm Jupiter’ systems showed companion planets in the inner system, and fully one-third of the hot Neptune systems showed the presence of inner system planets. Finally, the team looked at 52 ‘hot Earths’ in the Kepler data for TTVs, testing whether hot Jupiters and smaller worlds like these might co-exist in mutually inclined orbits. They found no evidence for high-mass companions on inclined orbits in this scenario.

The authors see this as a boost to the ‘scattering’ model, the study suggesting that hot Jupiters are migrating worlds on initially highly elliptical orbits that scattered other planets out of the inner system before their orbits became circularized close to their stars. Short period, low-mass planets would seem to have a different formation history than hot Jupiters. From the paper:

Hot Jupiter systems where planet-planet scattering is important are unlikely to form or maintain terrestrial planets interior to or within the habitable zone of their parent star. Thus, theories that predict the formation or existence of such planets (Raymond et al. 2006; Mandell et al. 2007) can only apply to a small fraction of systems. Future population studies of planet candidates, such as this, that are enabled by the Kepler mission will yield valuable refinements to planet formation theories — giving important insights into the range of probable contemporary planetary system architectures and the possible existence of habitable planets within them.

If hot Jupiter systems have a different dynamical history than other planetary systems, as this work suggests, then we have a useful filter to apply to exoplanet studies. If it can be firmly established that the presence of a hot Jupiter means no planets in the habitable zone, we know our resources are best focused elsewhere when it comes to looking for terrestrial worlds. It’s too early to make that call now, but the evidence is mounting that in most cases hot Jupiters are killer worlds when it comes to young planets in the warm regions where life may occur.

The paper is Steffen at al., “Kepler constraints on planets near hot Jupiters,” Proceedings of the National Academy of Sciences 109 (21) 7982-7987 (2012). Abstract available.

Toward a Beamed Core Drive

by Paul Gilster on May 22, 2012

If you didn’t see this morning’s spectacular launch of the SpaceX Falcon 9, be sure to check out the video (and it would be a good day to follow @elonmusk on Twitter, too). As we open the era of private launches to resupply the International Space Station, it’s humbling to contrast how exhilarating this morning feels with the great distances we have to traverse before missions to another star become a serious possibility. We’ve been talking the last few days about the promise of antimatter, but while the potential for liberating massive amounts of energy is undeniable, the problems of achieving antimatter propulsion are huge.

So we have to make a lot of leaps when speculating about what might happen. But let’s assume just for the sake of argument that the problem analyzed yesterday — how to produce antimatter in quantity — is solved. What kind of antimatter engine would we build? If everything else were optimum, we’d surely try to master a beamed core drive, the pure product of the matter/antimatter annihilation sequence. Protons and antiprotons are injected into a magnetic nozzle, blowing out the back at a substantial percentage of the speed of light. This is the kind of rocket analyzed by Ronan Keane (Western Reserve Academy) and Wei-Ming Zhang (Kent State University) in the paper I’ve been skirting around the edges of these past few days.

Channeling Antimatter’s Energies

The paper, headed for publication in the Journal of the British Interplanetary Society, has the provocative title “Beamed Core Antimatter Propulsion: Engine Design and Optimization,” and it deals with the particle stream emerging from proton/antiproton collisions. What you get when you put the two together are gamma rays and pions, some of the latter charged and some neutral. Almost immediately the pions decay into positrons and electrons, which meet each other and produce gamma rays. But the tens of nanoseconds the pions take to decay gives us long enough to channel the charged pions through a magnetic nozzle to produce the needed thrust.

The beamed core engine, then, is all about channeling the pions into a focused flow. Get this right and you’ve got a lot of energy to work with. In fact, Keane and Zhang note that the energy released per kilogram of annihilating antimatter and matter is 9 X 10¹⁶ joules, which is two billion times more than the thermal energy from burning a kilogram of hydrocarbon, and over a thousand times larger than burning a kilogram of fuel in a nuclear fission reactor. But while the beamed core engine is attractive because of the high relativistic velocities of the charged particles produced by the annihilation reactions, the situation is not ideal.

For one thing, much of the energy of the reaction goes into producing electrically neutral particles, which are impervious to the workings of a magnetic nozzle and thus cannot contribute to thrust. The other problem is that the nozzles we’ve been able to analyze have efficiency problems of their own in terms of creating the tight beam of thrust we’d like to produce. What Keane and Zhang do is to use software called Geant4 from the CERN accelerator laboratory to produce simulations of the interactions of particles with matter and fields. They want to bring previous studies of beamed core concepts up to date especially in terms of magnetic nozzles.

Robert Frisbee has performed rigorous studies of beamed core concepts in which magnetic nozzle efficiency is only about 36 percent, which means that while you’re dealing with pions that are initially moving at 90 percent of light speed and above, the exhaust velocity of the rocket would be just a third of that amount. Keane and Zhang derive an efficiency that is better than twice that, and manage to reach charged pion exhaust speeds of 69 percent of c. They also show that the initial speed of charged pions in a beamed core engine is actually closer to .81c than Frisbee’s 90 percent-plus. Despite the lower initial speed, the nozzle efficiencies make quite a difference depending on the kind of mission being attempted:

Frisbee’s papers explain in depth the needed generalization to account for emission of uncharged particles… When loss of propellant is taken into account, Frisbee has shown that v_e ~ 0.3c leads to a beamed core rocket facing daunting challenges in reaching a true relativistic cruise speed on a one-way interstellar mission where deceleration at the destination (a “rendezvous” mission) would be involved.

Fuel requirements become critical with lower nozzle efficiencies:

… with a payload of 100 metric tons, a 4-stage beamed core rocket designed for a cruise speed of 0.42c on a 40 light-year rendezvous mission would require 40 million tons of antimatter fuel. If the cruise speed were limited to 0.25c or less, only two stages might be needed, and Frisbee envisaged viable interstellar missions with as few as one beamed core stage; in such scenarios, fuel requirements would be dramatically lower.

All of this at 36 percent nozzle efficiency. The new numbers change the picture, with Keane and Zhang stating “With the new reference point of v_e =0.69c provided by the present Geant-based simulation, true relativistic speeds once more become a possibility using the highest performance beamed core propulsion in the distant future.”

Note the ‘distant future’ caveat, highly significant when you consider our problems in producing antimatter (or harvesting same) and the perhaps even more intractable issues involved in storage.

On Software and Methodology

But even if we can’t put a timeframe on something as futuristic as a beamed core rocket, we can continue to study the concept, and it’s heartening to see Keane and Zhang’s conclusion that the simulation software at CERN has proven robust in meeting this challenge and updating our numbers. Whether or not Keane and Zhang’s methodology is on target may be another issue, as Adam Crowl noted recently in a post to a private mailing list of aerospace engineers. Crowl hastens to add that his computations are provisional, but let me quote (with his permission) where he is right now on the magnetic nozzle efficiency issue:

There’s a problem with using just the exhaust velocity given to *part* of the fuel/propellant. It means the actual mass-ratio for a given delta-vee is quite different to a naive computation using the classic Tsiolkovskii equation. A more useful figure of merit for rockets with mass-loss in addition to reaction mass is specific impulse – momentum change per unit mass of fuel/propellant. Using the equations derived by Shawn Westmoreland and the rather vague particle energies in Zhang & Keane, the effective specific impulse is ~0.28c. Even with a perfect jet efficiency the Isp is just 0.31c.

The antimatter reaction, then, may not offer as much as we hoped:

The 0.81c average particle speed quoted in the paper isn’t as useful as the spread of kinetic energies in the particles produced, or the total kinetic energy in the distribution, but they don’t report either figure. What it does imply is that an antimatter-matter reaction puts about 11% of the mass-energy into the charged particles. Not exactly spectacular.

The chance to go to work on concepts through papers in the preprint process is invaluable, and we’ll see how Crowl’s thinking, as well as Keane and Zhang’s, evolves with further study of the issues in this paper. One thing is for sure: Given the manifest problems of antimatter production and storage, we’ll have no shortage of time in which to consider these matters before the question of actually producing this kind of antimatter rocket becomes pressing.

The paper is Keane and Zhang, “Beamed Core Antimatter Propulsion: Engine Design and Optimization,” accepted by JBIS (preprint).

Funding humans to Mars

by Frank Stratford
Monday, May 21, 2012

 

The subject of funding human Mars missions has been my focus—indeed, my obsession—for over seven years, as the dream of a future on Mars and in space hits the real world “wall” of lack of funding and all that it entails. I have read many different ideas, from the traditional government funding model to selling sponsorships on a private voyage to Mars to a lottery-style “Mars Prize”. All contain some elements of value, but as many of the non-government ideas are never really backed up with anything other than opinions, it is hard to say if any of them could accomplish anything to fund humans to Mars.

In 2012, the reality is that rockets are still very expensive, engineering the unknown is still as costly as ever, and the physics of getting into space remain unchanged. The fact is, space is hard, and getting to Mars several orders of complexity harder still.

There is no evidence that a billion-dollar private project where no customers exist, where the engineering is still conceptual or unproven, and where the real risks are unacceptably higher than other industries can be or has ever been funded.

Keeping humans alive and healthy on a round-trip or one-way program remains an unproven milestone along the road to Mars, with radiation mitigation, microgravity, and dust issues still without practical and proven solutions, just to name a few. It seems, then, that funding such a program, for the private or public sector, is still too risky, still too full of unknowns, and ranks far behind more relevant projects that can be done here on Earth.

There have been varying cost estimates for a private mission to Mars, from $5 billion to $30 billion, but of course these estimates are subject to change as engineering challenges along the way may inflate these costs. For private investors, this is simply unacceptable.

Most of the billion-dollar private projects we can think of involve the building of large skyscrapers, toll roads, transportation vehicles or networks, or other large-scale infrastructure projects that are then marketed to the general public for their use and payment. There is no evidence that a billion-dollar private project where no customers exist, where the engineering is still conceptual or unproven, and where the real risks are unacceptably higher than other industries can be or has ever been funded. Indeed, the relevance of the entire idea of sending humans to Mars is still very much in question: it is not a “practical consideration” such as a water reservoir or shipping canal might be. It doesn’t “make sense”, as similar multi-billion-dollar projects do.

So when the suggestion of a privately funded Mars mission for humans comes up, it is, of course, often met with laughs and expressions of incredulity.

Thus, we must first come to a “necessary solution”. Before we get to the funding of this project, we must first see if it makes sense. We must try to solve some of the logical roadblocks, like rockets that are too expensive and human life support factors that are still unknown. This may involve discussions, studies, and practical field research, but it needs a cohesive, structured direction, and it can’t be based just on the opinion of any individual engineer or single group of engineers, unless backed up with hardware research and development proof of concept studies.

That is where the concept of a “Mars Consortium” comes into focus as a potential solution at this stage in history. This consortium should start out as a research-oriented think tank made up of academics, enthusiasts, industry experts, and aerospace professionals, to see if we can indeed find solutions to many of the roadblocks and unknowns for a Mars mission for humans.

This consortium effort may take us in unexpected directions—perhaps even away from Mars initially—but as long as the more fundamental roadblocks are being dealt with, is that such a bad thing? For those of us who do want to see humans on Mars, in the end, it must make sense, or it will simply never happen. There are plenty of mission designs for sending humans there, but all remain theoretical concepts and all contain large gray areas of unknowns. None of them give us a reason why to go in the first place. None provide a common-sense answer as to how this can be done sustainably or affordably. In the post-2008 global financial crisis world, financial considerations are now more than ever our biggest obstacle to reaching Mars.

However, if a human mission to Mars could be done with rockets and space vehicles 10 or even 100 times cheaper than today’s vehicles, and if we had shown how humans can survive and thrive in those hostile space environments for periods of time 50 times longer than the old Apollo missions, and if we had actually identified prime sites for a human expedition on Mars and we had done the research on how to land safely and take off again, and if the costs were clearly identified and the profits were well researched and demonstrated, I have no doubt that we could have humans on Mars within a decade.

What we need to do is to move this whole subject from the realm of opinions, maybes, and debate, to facts and hard data. To do this we need to start somewhere. We need to move beyond conferences and talks to real research of some kind.

So I’d like to propose a call to action for this purpose: to investigate the technologies, requirements, financing, and revenue potential for a humans to Mars program, looking beyond government funding as the only solution. There may well be a government mission in the next 30 years, but as history has shown with all government space missions, it will not be sustainable and it will not lead to anything more than a short exploration effort, and it still won’t make sense to the rest of the world. To explore an entire planet with the surface area of Earth’s continents combined will take decades of in-depth scientific exploration; for a place like Mars, so far away and currently so expensive, this will require some kind of permanent outpost or settlements. This kind of consortium can also have a direct impact on how we can send humans to the Moon or other destinations in space if it demonstrated itself to be a viable model.

Maybe the concept of “cheap reliable access to space” will become a must for a sustainable future on Mars. Maybe there are medical issues that are showstoppers right now. What we need to do is to move this whole subject from the realm of opinions, maybes, and debate, to facts and hard data. To do this we need to start somewhere. We need to move beyond conferences and talks to real research of some kind.

But is this goal of humans to Mars worth this kind of effort? In a word, no. That may sound surprising, but as the single focus of this consortium, Mars may be a waste of time and resources for a variety of reasons. That is why this consortium will be investigating all of the issues surrounding this type of program, and one of the biggest is the creation and importance of cheap space access. Other areas may include the value of micro-scale robotic exploration, life support advances, medical solutions with spinoffs to the health sector, energy supply technologies that can be marketed here on Earth before they work on Mars, and so much more. None of these areas are “worthless”. All contain very important rewards if achieved, even without a humans-to-Mars program as the end point. Indeed, a privately funded program will demand a return on investment whether humans get to Mars or not, and that is the challenge.

This consortium would focus on the technological hurdles first, and how to generate revenue from them. Then, as these come into existence and some of the most fundamental technical hurdles are overcome, a human program for Mars may start to make sense, and be affordable, with investors then stepping forward. To help kick this effort off, you can contact me via email at frank.stratford@marsdrive.com, or support our Mars Expo event next year where we plan to show the general public all the exciting advances in private and government space efforts and also begin a dialogue on sensible ways to get humans to Mars.

 

Antimatter: The Production Problem

by Paul Gilster on May 21, 2012

Antimatter is so tantalizing a prospect for propulsion that every time a new slant on using it appears, I try to figure out its implications for long-haul missions. But the news, however interesting, is inevitably balanced by the reality of production problems. There’s no question that antimatter is potent stuff, with the potential for dealing out a thousand times the energy of a nuclear fission reaction. Use hydrogen as a working fluid heated up by antimatter and 10 milligrams of antimatter can give you the kick of 120 tonnes of conventional rocket fuel. If we could get the cost down to $10 million per milligram, antimatter propulsion would be less expensive than nuclear fission methods, depending on the efficiency of the design.

But how to reduce the cost? Current estimates show that producing antimatter in today’s accelerator laboratories runs the total up to $100 trillion per gram. But when I was researching my Centauri Dreams book, I spent some time going through the collection of Robert Forward’s papers at the University of Alabama-Huntsville, where several boxes of materials are stored in Salmon Library. Forward was constantly working in a number of different fields, always keeping his eye on the latest research, and as part of that effort he produced a series of newsletters on antimatter developments that he circulated among colleagues.

Reading through these materials, I came to see that when we quote the $100 trillion per gram figure, we’re talking about antimatter as produced more or less as a byproduct. Forward understood and appreciated the science requirements of particle accelerator labs but also saw that they were hardly the most efficient place to produce antimatter in any quantity. They were not, after all, in the propulsion business. He proceeded to do a study for the US Air Force looking at what might happen if an antimatter facility were actually designed for no other purpose than the creation of antiprotons, finding that the energy efficiency could be raised from one part in 60 million to a part in 10,000, or 0.01 percent.

The cost of building the factory, meanwhile, could be lowered dramatically, to the point where Forward believed our $10 million per milligram would be within reach. This is an interesting figure in several ways. As noted above, it makes antimatter feasible for certain kinds of space missions (assuming equivalent advances in our methods of antimatter storage. But as the price begins to drop, we can expect to find new applications in other areas of research, which should drive demand and spur further work on efficient production. It’s worth remembering that even at today’s prices, antimatter has proven its worth in scientific research and medical uses.

What about other ways of lowering the cost? One possibility is to look beyond slamming high-energy protons into heavy-nuclei targets. Writing with Joel Davis in a book called Mirror Matter: Pioneering Antimatter Physics (Wiley, 1988), Forward looked at options like heavy ion beam colliders, in which beams of heavy ions like uranium could be collided to produce 10¹⁸ antiprotons per second (with acknowledged problems in creating large amounts of nuclear debris). He also considered new generations of superconducting magnets to create magnetic focusing fields near the region where the beams collide, which should make tighter beams and greater antimatter production possible.

I bring all this up because the possibility of harvesting antimatter from natural sources in space, which we talked about last week, has to be weighed against boosting production here on Earth. But Forward’s ideas actually coupled the two notions. He wanted to move antimatter production by humans into space in the form of huge factories. Here’s what he has to say on this in an essay in his book Indistinguishable from Magic (Baen, 1995):

Where will we get the energy to run these magic matter factories? Some of the prototype factories will be built on Earth, but for large scale production we certainly don’t want to power these machines by burning fossil fuels on Earth. There is plenty of energy in space. At the distance of the Earth from the Sun, the Sun delivers over a kilowatt of energy for each square meter of collector, or a gigawatt (1,000,000,000 watts) per square kilometer. A collector array of one hundred kilometers on a side would provide a power input of ten terawatts (10,000,000,000,000), enough to run a number of antimatter factories at full power, producing a gram of antimatter a day.

We’re a long, long way from producing a gram of antimatter a day, of course, which is why studies like the recent one performed by Ronan Keane (Western Reserve Academy) and Wei-Ming Zhang (Kent State University) have such a futuristic air. But it’s important to learn the theoretical constraints on propulsion systems even if the required antimatter isn’t available, and on that score, Keane and Zhang are thinking ahead to the most advanced kind of antimatter of them all, a beamed core drive. To make it work, assuming you have the antimatter available, you need to inject protons and antiprotons into a magnetic nozzle, one that channels charged pions from the matter/antimatter annihilation into a focused beam of powerful thrust.

Although charged pions decay quickly, they can start out at 90 percent of the speed of light. Unfortunately, earlier magnetic nozzle calculations have proven inefficient at channeling these energies, dropping the exhaust velocity down to a third of this value. Tomorrow we’ll look at how a more efficient magnetic nozzle can produce better results, as Keane and Zhang have analyzed using CERN software to simulate what would go on in the hellish interior of a beamed core antimatter engine. But we also need to consider other ways of using antimatter for propulsion, assuming that Forward’s space-borne factories aren’t going to be coming online any time soon.

Antimatter: Finding the Fuel

by Paul Gilster on May 17, 2012

In Stephen Baxter’s wonderful novel Ark (Roc, 2010), a team of scientists works desperately to come up with an interstellar spacecraft while epic floods threaten the Earth. The backdrop gives Baxter the chance to work through many of our current ideas about propulsion, from starships riding a wave of nuclear explosions (Orion) to antimatter possibilities and on into Alcubierre warp drive territory. I won’t give away the solution, but will say that it partly involves antimatter used in an unorthodox way, and because Baxter’s is a near-term Earth, there simply isn’t enough antimatter to go around. That means getting to Jupiter first to harvest it.

Antimatter in space is an idea that James Bickford (Draper Laboratory) analyzed in a Phase II study for NASA’s Institute for Advanced Concepts, for he had realized that high-energy galactic cosmic rays interacting with the interstellar medium (and also with the upper atmospheres of planets in the Solar System) produce antimatter. In fact, Bickford’s calculations showed that about a kilogram of antiprotons enter the Solar System every second, though little of this reaches the Earth. To harvest some of this incoming antimatter, you need a planet with a strong magnetic field, so Jupiter is a natural bet for Baxter’s scientists, who go there to forage.

The odd thing, though, is that Saturn is actually a better source of antimatter than Jupiter, with 250 micrograms produced by reactions in the rings and injected into the magnetosphere every year. Bickford’s work showed that the process by which galactic cosmic rays produce antimatter isn’t as effective around Jupiter because its magnetic field shields the Jovian atmosphere and lowers the flux. A much larger flux reaches the atmosphere of Saturn. But Bickford also believed that our own Earth would be a good antimatter source, leading to the idea of using a plasma magnet — the scientist discusses using high temperature superconductors to form two pairs of 100-meter RF coils to manage this. The result is a kind of magnetic scoop that could trap antiparticles found in our planet’s radiation belts.

Why go to the trouble of collecting antimatter from space? Because antimatter production on the order of one-trillionth of a gram per year, which is about what we can get out of today’s accelerator labs through high-energy particle collisions, isn’t enough to power up a lightbulb for more than a few seconds. Moreover, at today’s prices the stuff costs about $100 trillion per gram. This is why Robert Forward, who used to circulate an antimatter newsletter among colleagues and wrote extensively about its possibilities, proposed that one day we would build antimatter factories in space. Build a large enough solar-powered array and you could, he thought, come up with something on the order of a gram of antimatter per day.

Remember that as little as ten micrograms of antimatter might power a 100-ton payload on a one-year mission to Jupiter and you can see that one gram of antimatter a day is a bountiful supply. But Forward’s antimatter collector array was huge, 100 kilometers to the side, and well beyond today’s engineering. Thus the interest generated by the PAMELA satellite (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) last year when it picked up more antiprotons in the region known as the South Atlantic Anomaly than had been expected.

This South Atlantic Anomaly is where the inner Van Allen radiation belt makes its closest approach to the Earth’s surface, which in turn creates a higher flux of energetic particles there. The PAMELA work showed that Bickford’s original NIAC analysis was correct — antimatter is indeed being produced near the Earth. Bickford went on to suggest that we could collect some 25 nanograms per day using his magnetic scoop, a process that if successful would prove orders of magnitude more cost effective than creating antimatter here on Earth.

So would Baxter’s doughty crew be able to harvest their antimatter much closer to home than Jupiter or Saturn? Maybe not. A new paper by Ronan Keane (Western Reserve Academy) and Wei-Ming Zhang (Kent State University) comes into play here. The authors have developed new thinking on antimatter propulsion, specifically on the magnetic nozzles that would be required to make it work. It’s important work and tomorrow I want to get into the propulsion aspects of it, but for today I note their comment on the PAMELA findings and antimatter. Here’s a quote:

The recent PAMELA discovery, in which the observed antiproton flux is three orders of magnitude above the antiproton background from cosmic rays, paves the way for possible harvesting of antimatter in space. Theoretical studies suggest that the magnetosphere of much larger planets like Jupiter would be even better for this purpose. If feasible, harvesting antimatter in space would completely bypass the obstacle of low energy efficiency when an accelerator is used to produce antimatter, and thus could offer a solution to the main difficulties stressed by the skeptics.

The problem with this — and this has been noted by The Physics arXiv Blog and Jennifer Ouellette in recent days — is that PAMELA could come up with only 28 antiprotons over the course of 850 days of data acquisition. There is no question that Bickford is right in seeing how antimatter can be produced locally. In fact, the paper on the PAMELA work says this: “The flux exceeds the galactic CR antiproton flux by three orders of magnitude at the current solar minimum, thereby constituting the most abundant antiproton source near the Earth.” But does the process produce enough antimatter to make local harvesting a serious possibility?

We need to learn more, obviously, and it’s worth noting, as Keane and Zhang do in their paper, that the Alpha Magnetic Spectrometer was installed on the International Space Station in mid-2011, giving us a much enhanced ability to detect and measure antiparticles in Earth orbit. Antimatter harvesting within the Solar System appears to be a workable concept, but if we’re going to need to go to the gas giants to make it happen, we’re obviously pushing back the time frame on collecting significant quantities that could be used in future propulsion systems.

More on this tomorrow, when we’ll look further at Keane and Zhang’s ideas on antimatter engines and what could make them possible. Their paper is “Beamed Core Antimatter Propulsion: Engine Design and Optimization,” submitted to the Journal of the British Interplanetary Society (preprint). The PAMELA work is Adriani et al., “The discovery of geomagnetically trapped cosmic ray antiprotons,” Astrophysical Journal Letters Vol. 37, No. 2, L29 (abstract / preprint). For a cluster of Bickford references, see Antimatter Source Near the Earth, published here last August.

Changing the Risk Paradigm

by Paul Gilster on May 16, 2012

As we continue to think about the implications of Planetary Resources and its plans for asteroid mining, I was interested to see exoplanet hunter Sara Seager (MIT) make a rousing case for the company’s ideas and for commercial space ventures in general. Seager, who works with Planetary Resources as a science advisor, tells The Atlantic’s Ross Andersen in a May 14 interview that one reason for optimism is the progress we’re making with robotics. Mining operations currently being managed beneath the seas are being handled by robotics. Couple that with our ability to get to and orbit an asteroid as well as to scoop up surface materials and you have all the ingredients for a workable mining operation in a low-gravity environment.

Seager explains that asteroids are attractive mining targets because unlike fully formed planets like the Earth, their heavier elements have not largely sunk inside through planetary differentiation in the early days of the planet’s existence. Asteroids are either fragments of bigger objects or building blocks that were never fully formed, meaning that high-value platinum metals should be readily accessible on the right kind of object. Their low gravity and, in the case of NEA’s, proximity mean that they are attractive targets from which to return materials.

Planetary Resources is intriguing not only because of potential mining returns but because it involves a different model of detail and risk than would be acceptable in a government-created program. Here Seager invokes the Mars Science Laboratory, a $2 billion mission that will land a rover on Mars this summer. MSL became a huge operation because it is a general science mission that demands the 10 different science instruments aboard the craft, making it a heavier rover and demanding a landing system far more complicated than the air-bag methods we’ve used successfully in our last several Mars landings. A private firm, on the other hand, can focus tightly on a specialized goal rather than aiming for a multi-purpose mission from the start.

But there’s a bigger difference, adds Seager:

In the private spaceflight world there are focused goals with profit and new capability as priorities. At NASA the motivation for space missions is different. In addition to big and general science goals, the main goal appears to be not to fail. In this sort of culture the bigger space companies and academia are taught that it, the mission, has to work.

Even the large space companies like Lockheed and Northrop Grumman can become trapped inside this paradigm, for they are not creating long-term, sustainable businesses with the work they perform for the government. Instead, they are operating within a culture riddled with bureaucracy and plagued with high costs. Seager likes the look of young and lean space companies:

…at small space companies, things can fail. Risk is part of developing new technology. Also, for the big space companies the whole competition is just getting the government contract. The competition is not about making something awesomely cool, first to market, and making a ton of money out of it. So in my opinion, the motivation factor and the risk aversion factor make it basically impossible for these larger companies to shift gears. The question that is on the minds of a lot of people is “Can America continue to be competitive in space with the current paradigm?” And the answer is no. That is the reason we have seen the rise of the commercial space flight world—they’re trying to start a new paradigm for spaceflight with a sustainable business that doesn’t just rely on government contracts.

The Seager interview is well worth your time as she discusses not only the Planetary Resources business model but the implications involved in getting a new generation of small and inexpensive technology into space. It’s no surprise that the Arkyd series of spacecraft should catch her eye, since Seager is also involved in a project called ExoplanetSat, a prototype ‘nanosatellite’ that can monitor a single, Sun-like star for two years. This gets seriously interesting when you start talking about producing a large number of such satellites, because while we have the Kepler mission monitoring planetary transits in a fixed field, we have no mission in the works to hunt for planets around the nearest and brightest stars.

So instead of a single space telescope fixated on tens of thousands of stars, most of them distant from the Sun, we invert the model to produce a fleet of tiny telescopes with a single target each, with the detailed properties of each star under observation programmed into each instrument. You can see why Planetary Resources’ plan to launch a large number of small space telescopes would appeal to Seager. The Arkyd series (based on the company’s original name) would allow small institutions to buy a space telescope for a price ranging from $1-10 million, opening space-based observations to universities or even wealthy individuals.

Here again Seager sees Planetary Resources tweaking the basic model of how science gets done. A telescope specifically designed for a unique science goal can produce superb results, as we’ve learned from Hubble, CoRoT, Kepler and other missions. But bring a commercial interest into the mix and a new flexibility emerges. Planetary Resources can sell small space telescopes into a new market, while also using the product for its asteroid characterization work. The mix of motivations provided by commercial space drives the enterprise. Adds Seager, “If you’re part and parcel of the commercial space flight world, it appears you can get a lot of interesting things done. I think that in academia we could learn a lot from the business world.”

How Space-Age Nostalgia Hobbles Our Future

Contrary to popular belief, public support for space exploration in the 1960s was far from universal.

By Matt Novak|Posted Tuesday, May 15, 2012, at 7:45 AM ET

 

The future used to be so much better. At least that’s what everyone under the age of 65 keeps telling me. In the 1950s and ‘60s, people dreamed of—nay, expected—jetpacks and flying cars and colonies on Mars. On Mars!

Legend has it that after the Soviet Union launched Sputnik, the first human-made satellite to ever orbit the Earth, in 1957, Americans rallied behind the idea of a better, more technologically advanced future for all. This nationwide enthusiasm buoyed NASA’s Apollo program and, as much as rocket fuel, propelled us to the moon. During his 2011 State of the Union address, President Obama invoked the popular idea of the “Sputnik moment” as he implored Congress to invest more in scientific research and education.

So what percentage of Americans in the 1960s do you suppose believed that the Apollo program was worth the time and resources devoted to it? Seventy percent? Eighty percent?

In reality, it was less than 50 percent.

Erik Conway, historian at the Jet Propulsion Laboratory in Pasadena, Calif., explains: “The Apollo program only had a majority public support—over 51 percent—for the few months around the 1969 moon landing. That’s it. Otherwise, it was less than 50 percent.” In a 1969 opinion poll taken after the lunar landing, just 53 percent of American adults believed that the moon excursion was worth the expense. In fact, during the nine years of the Apollo program, American support pretty much fluctuated between 35 percent and 45 percent. In a 2005 paper, Roger Launius, chief historian at NASA, wrote, “While there may be many myths about Apollo and spaceflight, the principal one is the story of a resolute nation moving outward into the unknown beyond Earth.” Nostalgia for the Space Age is rooted more in The Jetsons than in reality.

But try telling that to the baby boomers, who insist that they grew up in the most wondrous period of scientific adventure in U.S. history—a time when Americans supposedly united behind a single goal and achieved it. Raised by parents who spoke wistfully of watching the moon landing, Generation X and the Millennials have bought into the narrative, too. This romanticization of the past has real-world consequences because it breeds a certain kind of futility, a belief that we’re simply not able to accomplish things without every American behind the idea. The myth of the “Sputnik moment” means that we spend time hand-wringing over a lack of shared ambition, rather than actually working toward game-changing goals. Time is wasted as we act like petulant children, whining that no one wants to go to Mars anymore, rather than making the case for a manned Red Planet mission.

So where did this myth of national unity around the space race come from? There are two explanations. 1) The people currently telling the story of the Space Age were young in the 1960s. The world is a much simpler (and often much rosier) place through the eyes of a child. 2) Just as history is written by the victors, space history is written by space enthusiasts.

Unfortunately, we don’t have public opinion polls of children from this time. What we do have are toy sales figures.

Immediately post-WWII, cowboys were all the rage. Stanley Breslow of the Carnell Manufacturing Co. explained to The New Yorker in 1950: “Last year there were enough [cowboy gun] holster sets manufactured to supply every male child in the United States three times over. I don’t know where they all go.”

By 1958, the year following the Soviet launch of Sputnik, a full 50 percent of the $1.3 billion U.S. toy market was sci-fi-related. Kids traded in their six-shooters for ray guns. That’s significant to the narrative we see today about Americans’ shared Space Age ambitions. Conway explains:

There’s a tendency to assume that everyone knew all along that [the Apollo program] would be successful and that everybody enjoyed it and so forth and so on. And of course it’s looked back on fondly by the generation who grew up then, not necessarily their parents. And who is it now that are the main spokesmen of … well, everything in the United States, right? It’s folks … who were kids during the Apollo program and who loved it even if their parents didn’t.

In 1989 Howard Schuman and Jacqueline Scott at the University of Michigan published a paper on generations and collective memories. They quantified what seems like common sense: The events that happen around us when we’re children create the strongest memories. Or, to put it in academic speak: “[T]he events and changes that have maximum impact in terms of memorableness occur during a cohort’s adolescence and young adulthood, often referred to as ‘youth.’ ”

The study asked people in 1985 about the past 50 years, a period that included the Great Depression, World War II, the Vietnam War, the Kennedy assassination, the threat of nuclear war, the civil rights movement—the list goes on. The third most-mentioned important “event” from 1935-85 was space exploration, just behind World War II and the Vietnam War.

The study only measured attitudes toward the space program for those who mentioned it as a momentous achievement, but it still found a distinct difference between generations. While those of the Greatest Generation and the Silent Generation simply expressed awe at the achievement, often using words like “amazing” and “fantastic,” the baby boomers were the ones who talked about national pride and the inevitability of space in their future.

A 24-year-old woman in the study said, “Our world will change in the next 50 years because of what’s going on the space industry. We may make moves to live elsewhere.” That woman was 8 when humans first set foot on the moon and, if she’s still alive, is now about 51. Similarly, a 27-year-old woman remarked, “Well, we might even have space stations and so if we destroy our world, we will have a place to go.” She was 11 during the lunar landing of 1969 and would be 54 today.

You almost have to feel bad for the baby boomers for not getting the future they were promised. When they were kids, there was a deliberate effort to get children excited about, and emotionally invested in, scientific and technological progress. Dr. Athelstan Spilhaus, the dean of the University of Minnesota’s Institute of Technology, started one of at least two Sunday newspaper comic strips borne out of concern that American kids were falling behind the Russians intellectually and weren’t sufficiently interested in science and technology. The comic explained scientific principles, often with a futuristic flair, and by 1959, Dr. Spilhaus’ “Our New Age” appeared in more than 100 U.S. newspapers.

Dr. Spilhaus sat down with Louise O’Connor, who recorded oral histories over three years with him in the late 1980s. Spilhaus recalled, “I decided to [start writing Our New Age] right after Sputnik, when I was disturbed about kids knowing very little about science. Rather than fight my own kids reading the funnies, which is a stupid thing to do, I decided to put something good into the comics, something that was more fun and that might give a little subliminal education.”

But even as parents were buying up space toys for their kids and encouraging them to read the more educational Sunday funnies, they were skeptical, even surly, about the funds spent on Apollo and NASA. Those people with reservations about the space program seemed to be primarily concerned that the money spent on space could be better invested in more earthly problems.

Shortly after the Apollo 11 crew was launched, destined for the historic first landing on the moon, a reporter from the Delaware County Daily Times in Pennsylvania went to the local mall to ask how people felt about the imminent moon landing. Many thought that the money should be spent elsewhere.

Sheila Larkin of Brookhaven told the reporter that there were “better uses for much of the money that goes into the space program. It’s great that they can do it, but there is so much poverty in the country that the money could go other places.” George Conaway, a retired machinist, said that the trip was “foolish and a waste of money—money that should be spent on the poor people in this country.” Giles Jones said that it was important the U.S. would land there first, but offered reservations: “We’re supposed to be the greatest country and we can show that this way. But there are other good uses for much of the space program money.”

The day after the moon landing, a number of Associated Press articles reflected the mixed public opinion about the historic event. One of the articles focused on the feelings of New Englanders and was generally positive, quoting people who called the achievement “amazing” and “unbelievable” but the piece also quoted people like Barbara C. Sauer from Portland, Maine, who said, “It’s really a good accomplishment, but the money should be spent here on earth.” The article also quotes Frederick W. Varney, a 50-year-old service station operator from Bangor, Maine, who said that he hope it does some good but, “I think it’s a waste of money.”

That widespread ambivalence plays into another part of the “Sputnik moment” myth: that NASA’s coffers were bursting during the ‘60s. Erik Conway, the historian at the Jet Propulsion Laboratory, told me, “The basic facts are that every year after 1964 Congress cut the NASA budget. Why did they do that? Well, the reality simply was that the public support wasn’t there.”

Personally, I’d like to see NASA well-funded. Space exploration is an important part of our future, and I firmly believe that we can push the boundaries of science while still addressing important domestic issues of poverty, racism, and health care—just as we did to certain degrees of success in the 1960s and ‘70s. But if we continue to perpetuate the inaccurate myth, we’re essentially declaring that America’s best days are behind us, instilling a certain futility. How might we live up to the greatness of an era when everyone got along and the nation stood united in a single goal? By approaching the future and the challenges ahead with a better understanding of history—stripping away the fictions of our retro-futures—our greatest obstacles may start to seem surmountable. With any luck, our children’s children might romanticize the 2010s as a time when people used to get things done.

Space merchants and planetary mining

by Ayodele Faiyetole
Monday, May 7, 2012

 

The exhaustibility of mineral resources on Earth and their almost infinite deposits, b comparison, on the different planetary bodies in our solar system is fast leading to the development of a whole new industry spearheaded by exploratory-entrepreneurial visionaries. These space merchants, like the British who prospected America as a tobacco plantation, have conceived that the outer space holds the prospects for some of the world’s most valuable minerals that could be exploited for usage here on Earth and beyond.

The asteroid miners

Planetary Resources, Inc. made public its plan last month to mine the near-Earth asteroids (NEAs) for resources that are in so much of abundance (see “Planetary Resources believes asteroid mining has come of age”, The Space Review, April 30, 2012). The company will launch a series of unmanned spacecraft starting with their Arkyd-100 Earth-orbiting telescopes to prospect candidate NEAs. Subsequently, they plan to launch new spacecraft to mine precious metals and extract water, which can be used for fuel and in life-support systems for human space exploration.

Planetary Resources “is establishing a new paradigm for resource utilization that will bring the solar system within humanity’s economic sphere of influence” by mining asteroids, Diamandis said.

Considering the array of leaders of different industries that are backing Planetary Resources, one might consider this a done-deal success even before the start. The venture’s financiers include The Perot Group Chairman Ross Perot, Jr. and Larry Page, CEO of Google. Planetary Resources founders, Peter Diamandis and Eric Anderson, have already created one new space industry by pioneering the space tourism business with the founding of Space Adventures. The Planetary Resources backers include two-time space tourist and former Microsoft executive Charles Simonyi, Eric Schmidt and Ram Shriram of Google, and filmmaker James Cameron.

Diamandis said Planetary Resources “is establishing a new paradigm for resource utilization that will bring the solar system within humanity’s economic sphere of influence by enabling low-cost robotic exploration and eventual commercial development of asteroids.” Definitely, this is not the first time entrepreneurs are seeking to actively look “spaceward” with such “bold steps” to prospect, exploit and utilize its resources.

The Moon miners

Moon Express, Inc., which was selected by Forbes as one of the 15 “Names You Need to Know” in 2011, has made known its interest in prospecting outer space for resources since its formation in 2010. On April 23, the Google Lunar X PRIZE contender announced it had successfully delivered its Preliminary Design Checkpoint Technical Package to NASA under its $10-million Innovative Lunar Demonstration Data (ILDD) contract, providing NASA continuing data on the development of the company’s commercial lunar robotic missions and plans to mine the Moon. MoonEx, as Moon Express is also known, was selected in 2010 for this data buy contract, which happens only after technology is demonstrated at the company’s own risk. Technology luminaries Naveen Jain and Barney Pell teamed up with space visionary Robert Richards to form MoonEx based at the NASA Research Park in Silicon Valley.

In answering my question of what similarities or distinctions exist between these planetary mining companies, Richards, CEO of MoonEx, said, “Basically, Moon Express plans to mine asteroids too. The main difference is that MoonEx is planning to mine asteroidal material on the Moon.” He further explained the company’s rationale for going to the Moon: “proximity, shorter horizon, less risk, existing technology, known destination sampling, and distributed materials.” On the other hand, “asteroids are far, far away, longer horizon, high risk, no existing technology, no destination sampling, and concentrated materials.” From Richards’ analysis, the Moon has clear advantages from both business and technical perspectives.

Extraterrestrial resource extraction may lead to whole new industries, products, and lower costs as resources become more abundant.

Under a special partnership agreement with NASA, MoonEx in a way has hired NASA to help create a small, high performance, lunar lander system. “This will be launched starting from as early as 2014,” Richards said. If this launch date is accomplished it will be the first time a commercial company will travel out of the Earth’s orbit to another world.

The gains to humanity

No matter how difficult mining these planetary objects might get, our existence here on Earth is bound to benefit hugely from this NewSpace industry should it succeed. Terrestrial mineral resources are exhaustible, and reserves here on Earth are fast being depleted by continuous exploitation, causing long-term resource concerns. A new window to the nearly infinite reserve of such minerals and more will do humanity good in terms of abundance and prosperity.

New industries will be created and developed as a result of this planetary mining. In the past, space activities have relied heavily on measuring spinoffs when calcuating the gains from space exploration; this is bound to change. Extraterrestrial resource extraction may lead to whole new industries, products, and lower costs as resources become more abundant. As a result, new skills will be needed, spurring jobs creation for the entire economy.

The activities of these planetary miners may, consciously or unconsciously, further open up the final frontier, and will serve as an enabler for human spaceflight. As Planetary Resources’s Diamandis noted, “Accessing water resources in space will revolutionize exploration and make space travel dramatically more economical.”

 

Antimatter Propulsion Engine Redesigned Using CERN's Particle Physics Simulation Toolkit

Latest simulation shows that the magnetic nozzles required for antimatter propulsion could be vastly more efficient than previously thought--and built with today's technologies

Smash a lump of matter into antimatter and it will release a thousand times more energy than the same mass of fuel in a nuclear fission reactor and some 2 billion times more than burning the equivalent in hydrocarbons. 

So it's no wonder that antimatter is the dream fuel for science fiction fans. 

The problem, of course, is that antimatter is in rather short supply making the prospect of ever building a rocket based on this technology somewhat remote. 

But from time to time physicists put aside these concerns and have a little fun working out how good antimatter rocket engines can be. Today it's the turn of Ronan Keane at Western Reserve Academy and Wei-Ming Zhang at Kent State University, both in Ohio, who take a new approach to the problem with some interesting results. 

First, some basic rocket science. The maximum speed of a rocket depends on its exhaust velocity, the fraction of mass devoted to fuel and the configuration of the rocket stages. "The latter two factors depend strongly on fine details of engineering and construction, and when considering space propulsion for the distant future, it seems appropriate to defer the study of such specifics," say Keane and Zhang.

So these guys focus on the exhaust velocity--the speed of the particles produced in matter-antimatter annihilations as they leave the rocket engine. 

The thrust from these annihilations comes largely from using a magnetic field to deflect charged particles created in the annihilation. These guys focus on the annihilation of protons and antiprotons to produce charged pions. 

So an important factor is how efficiently the magnetic field can channel these particles out of the nozzle. 

In fact, the exhaust velocity of these pions depends on two factors--their average initial velocity when they are created and the efficiency of the magnetic nozzle design. 

In the past, various physicists have calculated that the pions should travel at over 90 per cent the speed of light but that the nozzle would be only 36 per cent efficient. That translates into an average exhaust velocity of only a third of lightspeed, barely relativistic and somewhat of a disappointment for antimatter propulsion fans.   

All that is set to change now, however. Keane and Zhang have come up with a different set of figures with the help of software developed by CERN that simulates the interaction between particles, matter and fields of various kinds. 

CERN uses this software, called GEANT4 (short for Geometry and Tracking 4), to better understand how particles behave at the Large Hadron Collider, which itself collides beams of protons and antiprotons. So it's ideally suited to Keane and Zhang's task. 

The new work produces some good news and some bad news. First the bad. The new simulations indicate that pions produced in this way will be significantly slower than previously thought, travelling at only 80 per cent of light speed.

The good news is that the GEANT4 simulations indicate that a magnetic nozzle can be much more efficient than previously envisioned, reaching 85 per cent efficiency. That translates into an average exhaust velocity of about 70 per cent light speed. That's much more promising. "True relativistic speeds once more become a possibility," say Keane and Zhang.

These guys have another surprise up their sleeve. Their nozzle has a magnetic field strength of around 12 Tesla. "Such a field could be produced with today’s technology, whereas prior nozzle designs anticipated and required major advances in this area," they say.

That will bring a smile to the face of many science fiction fans.

There is, of course, the small problem of gathering enough antimatter for a journey of any decent length. The number of antiatoms made at CERN is small enough to be countable. By one estimate, at this rate it will take a thousand years to make a single microgram of antimatter. 

Keane and Zhang point out that all earlier estimates predate the PAMELA spacecraft's discovery last year that Earth is surrounded by a ring of antiprotons and suggest that this could mined for fuel. What they don't mention, however, is that PAMELA spotted only 28 antiprotons in two years--far less than the rate at which CERN makes them on a daily basis.

Keane and Zhang finish by noting that other fuel technologies have advanced at an exponential rate, liquid hydrogen production, for example. If antimatter manufacture turns out to follow a similar trajectory, who knows what could happen.  

Interesting, entertaining and wildly ambitious--all good fun.

Ref: arxiv.org/abs/1205.2281: Beamed Core Antimatter Propulsion: Engine Design and Optimisation