by Paul Gilster | Jan 29, 2016 | Culture and Society |
It’s been awhile since I’ve seen Ian Crawford (Birkbeck College, London) — I think we last talked at one of the 100 Year Starship events — but I’m pleased to see his latest popular essay How to build a starship – and why we should start thinking about it now. A professor of planetary sciences and advocate of manned space exploration here in the Solar System, Crawford takes on the necessary task of acquainting a larger audience with something Robert Forward put forth as a maxim: ‘Starflight is difficult and expensive, but not impossible.’
Following decades of work on beamed sail technologies, antimatter and space tethers, Forward wrote that line in 1996, but it summed up statements he had been making for decades. Gregory Matloff and Eugene Mallove would echo him in their Starflight Handbook (Wiley, 1989), with an emphasis on the ‘difficult’ aspect of the journey: “Starflight is not just very hard, it is very, very, very hard!” So I guess we could say starflight is hard3. Matloff, who knew Forward well, has never entertained any illusions about the magnitude of the task.
Neither has Ian Crawford, who wants to keep Forward’s injunction out there. If there were some aspect of known physics that would have to be contradicted to make star travel possible, we would look at the matter differently. But instead we find vast problems of engineering and the need to overcome huge distances with craft that can operate for decades and perhaps centuries, returning data at the end of the journey. Crawford’s work has always engaged me because of his inherent optimism, and here he makes the case that ongoing work in areas like nanotechnology may get us to at least small, robotic space probes sooner than we think.
Igniting the Effort
The driver for such an attempt, in my view, would be the discovery of a nearby world in the habitable zone of its star. But it would take more than its presence. We would also have to have data from future space missions (and the next generation of ground-based telescopes) that showed biosignatures in the planet’s atmosphere. If we could make a strong case for there being a living world around, say, a planet of Proxima Centauri, we would surely want to make closeup investigations to learn about how evolution has played out on such a world.
Crawford gives a nod to the five craft that are currently on track to leave our Solar System altogether — the two Pioneers, the two Voyagers, and New Horizons. All will fall silent long before they approach another star, though I have been trying to resurrect a Sagan idea from the early Voyager days that one or both craft could have their trajectories adjusted with a final, tank-emptying burn to make a stellar encounter more likely in tens of thousands of years. If this sounds quixotic, it’s meant to be. It would be a purely symbolic statement of what our species can do (and as for the more practical details, I’ll turn you to my essay Voyager to a Star).
Image: Professor Ian Crawford doing astrobiological fieldwork on the Kverkfjoll volcano, Iceland. Credit: Ian Crawford.
But actual scientific return is another matter. It will require not ‘new physics’ but an expansion of our existing capabilities into areas of long-lifetime instrumentation and advanced laser communications, not to mention propulsion technologies like beamed power, fusion or more exotic methods. We’ve investigated the latter in the pages of Centauri Dreams, and Crawford has written them up in a 2010 paper called “‘A Comment on ‘The Far Future of Exoplanet Direct Characterization’ – The case for Interstellar Space Probes” (citation below).
Over the years, scientists have worked out a number of propulsion designs that might be able to accelerate space vehicles to these velocities… While many of these designs would be difficult to construct today, as nanotechnology progresses and scientific payloads can be made ever smaller and lighter, the energies required to accelerate them to the required velocities will decrease.
So we can talk about nuclear possibilities. Here I lean much more strongly toward nuclear pulse methods (think Project Orion) than fusion, though it will be interesting to see what the Icarus Interstellar team comes up with as it continues to refine the 1970’s-era Project Daedalus starship, which itself was based on a still-unavailable method called inertial confinement fusion, as studied by Friedwardt Winterberg. Using the energy released by either splitting or fusing atomic nuclei has long been studied by interstellar theorists, as has the much more powerful annihilation of matter and antimatter, though this is plagued by production problems (we can’t produce remotely enough) and certainly by storage issues for large amounts of antimatter.
Everything from interstellar ramjets to beamed laser or microwave sails is in the database here. Of the latter, Crawford says this:
Spacecraft using “light-sails” pushed by lasers based in the solar system are also a possibility. However, for scientifically useful payloads this would probably require lasers concentrating more power than the current electrical generating capacity of the entire world. We would probably need to construct vast solar arrays in space to gather the necessary energy from the sun to power these lasers.
Absolutely so, making the construction of a space-based infrastructure here in the Solar System a prerequisite for sending our first true interstellar probes. As Crawford notes, we are talking about systems far too large and certainly too power-laden to contemplate launching from Earth. They’ll be constructed in space as an outgrowth of this infrastructure. “This means,” Crawford adds, “that interstellar space travel is only likely to become practical once humanity has become a spacefaring species.”
Incremental Growth into Space
So there is a path for development here that acknowledges our current inability to send craft with data return capability to nearby stars, and addresses the problem by moving step by step to gradually acquire the needed expertise. This takes us to the Moon and Mars and beyond:
We need to progressively move on from the International Space Station to building outposts and colonies on the Moon and Mars (as already envisaged in the Global Exploration Roadmap). We then need to begin mining asteroids for raw materials. Then, perhaps sometime in the middle of the 22nd century, we may be prepared for the great leap across interstellar space and reap the scientific and cultural rewards that will result.
Image: To make the first interstellar mission a reality, we’ll need to move step by step from current space technologies toward a true infrastructure moving well beyond Earth orbit. Credit: NASA.
Crawford’s is a vision that places interstellar efforts into a broad context, one that will have to build the necessary levels of public support, and of course it will also have to show short-term value by way of scientific return and, in the case of asteroid mining, the necessary raw materials for growing the infrastructure. I think the middle of the 22nd Century is a highly optimistic goal, but it’s one worth working toward, and we can’t know what kind of breakthroughs may occur along the way (again, my money is on nanotech) to make the process quicker and more effective. Star travel may be hard3, but what else would we expect when it comes to translating a great imaginative venture into a mission that will someday fly?
Ian Crawford’s paper on interstellar propulsion technologies is “A Comment on “The Far Future of Exoplanet Direct Characterization”—The Case for Interstellar Space Probes,” Astrobiology 10(8) (November, 2010), pp. 853-856 (abstract).
by Paul Gilster | Nov 13, 2015 | Culture and Society |
Kelvin Long is chief editor of the Journal of the British Interplanetary Society and the author of Deep Space Propulsion (Springer, 2011). A founder and first project leader of Project Icarus, the ongoing re-design of the Project Daedalus starship, Kelvin is also a co-founder of the non-profit Icarus Interstellar. He now serves as executive director of the Institute for Interstellar Studies, an organization whose mission (‘Scientia ad Sidera: Knowledge to the Stars’) he describes in the following essay.
by Kelvin F. Long
The Initiative for Interstellar Studies (i4is) is a not-for-profit foundational institute incorporated in the United Kingdom with the mandate to develop interstellar capabilities. We at the initiative just successfully passed our third anniversary since our founding. We began work in August 2012 and went live on the 12th September 2012. Shortly after, we ratified our purpose through our innovative logo, and our mission and vision statements. And today we are focused on the launch of our innovative new educational course titled ‘Starship Engineer’. We are piloting the first version of this in London during November, and we hope some of you will join us: http://i4is.org/news/starship_engineer
But first, it is worth just reminding the readers what we are really about. The mission of i4is is to foster and promote education, knowledge and technical capabilities which lead to designs, technologies or enterprise that will enable the construction and launch of interstellar spacecraft. The vision of i4is is to aspire towards an optimistic future for humans on Earth and in space. Our bold vision is to be an organisation that is central to catalysing the conditions in society over the next century to enable robotic and human exploration of the frontier beyond our Solar System and to other stars, as part of a long-term enduring strategy and towards a sustainable space-based economy. Our motto is “Scientia ad sidera” (knowledge to the stars) and our philosophy of approach is “Starships in our Lifetime”. In addition to this, we also spent weeks writing our own bespoke articles of association, which forms our effective constitution as a company limited by guarantee but not having a share capital – which means we are a not-for-profit entity. In addition, our team produced a ‘founding Declaration’ which sets out what we believe and are working towards. The full text of this can be read here: http://i4is.org/the-starship-log/foundations
So how far have we got in the constitution of the world’s first ever foundational institute dedicated to the goal of the stars? The Initiative for Interstellar Studies is led by a board of directors for which I serve as its Executive Director, supported by the Deputy Directors Rob Swinney and Andreas Hein. We are also supported by our international advisory committee which is chaired by Professor Gregory Matloff and deputy Professor Chris Welch. We have various committees, including a marketing committee and a finance committee, which ensures we are fiscally compliant and ethical? But our activity based committee’s number a few, and I shall give a brief synopsis of each in turn along with their achievements to date?
The Alpha Centauri Prize Committee has the purpose of rewarding success and incentivising progress in activities related to interstellar studies. So far the committee has given out several awards for University students associated with their thesis projects, or for internal members for work that they have done to assist our mission that goes above and beyond what is expected of them. We have received sponsorship from several external organisations to fund those awards. We seek to establish the Alpha Centauri Prize awards as the standard by which all of our progress is measured.
The Educational Academy Committee is chaired by Rob Swinney and has the purpose of fostering educational abilities to conduct research relating to a broad set of subjects pertaining to interstellar studies, associated sciences and the arts. The committee has undergone much public outreach work, working with schools and universities, particularly across the UK.
The largest activity of this committee is in working with the International Space University in Strasbourg, and in particular with its Master’s Director Professor Chris Welch, who is a continued inspiration not just for the students but for all of us in his steadfast support of our ambitious efforts. Within this co-operative relationship, for which we have signed a Memorandum of Understanding, some of our projects have included “Autonomous Space Colony Construction” authored by Michio Hirai, which considered the manufacture of large structures in space; “Agriculture Design Trade-offs for Space Colony Feasibility“, authored by Erik Franks, which discussed farming methods in spaceflight; “Review of the Deceleration Options for a Robotic Interstellar Spacecraft Entering the System of Another Star“, authored by Wei Wang; “The Oculus Project: Solar Sailing to Discover Exoplanets at the Center of Our Galaxy“, authored by Piotr Murzionak, which looked at a gravitational lensing mission based on the ideas of the pioneer Claudio Maccone; “Jude: Solar Sailing A Low Mass Payload to Alpha Centauri-B“, authored by James Harpur, which considered an interstellar solar sail mission. The committee has also created a fun educational exam paper, which we call the ‘interstellar minimum’ – dare you have a go at it? http://i4is.org/the-starship-log/interstellar-minimum
Our biggest technical and educational accomplishment working with the International Space University has been the initiation and completion of a world ship project titled “Astra Planeta” and you can read a copy here: https://isulibrary.isunet.edu/opac/index.php?lvl=notice_display&id=9454].
This project was selected as one of the few team projects that the ISU runs each year and it involved over 20 Master’s students. The team also looked at the issues of creating a strategic and technological roadmap for a world ship. But the nice thing about this project, is that it also got supported by representatives from the Tennessee Valley Interstellar Workshop and Icarus Interstellar – so it may be one of the first successful pan-interstellar community projects, and is perhaps a model for the future.
The Technical Research Committee is chaired by Andreas Hein and has the purpose of conducting innovative theoretical and experimental research and development across the broad spectrum of issues relating to interstellar studies, associated sciences and the arts.
The committee’s flagship initiative is Project Dragonfly, which seeks to develop laser-sail propulsion capabilities based on the original ideas of Robert Forward. In the summer, the team ran a Kickstarter award and successfully won over $10,000.
This helped to fund a university affiliated design competition, which included participating teams from Cairo University, Egypt; University of California Santa Barbara, USA; Technical University of Munich, Germany and CranSEDS which involved students from Cranfield University in the UK, Skoltech in Russia and UPS in France. The University of Munich team won the competition with their innovative sail design. The four reports submitted by these teams were highly comprehensive and had to adhere to detailed competition requirements. To celebrate the award, the space artist David A Hardy was commissioned to produce an inspirational piece of art work of the winning design. The Technical Committee is now working on a technology roadmap focussed around the laser-sail technologies and this includes the consideration of actual space missions for the near future.
Image: Schematic of the winning Project Dragonfly design.
Image: David A Hardy commissioned art work of the winning laser-sail design for project Dragonfly.
The committee is also chairing several projects and this has already led to several reports. This includes “Project Sentinel” authored by Sissi Enestam, which described research into emission signals from different potential advanced space transportation systems as a contribution to SETI; “Space Eternal Memory” authored by Melissa Guzman which described methods of preserving and storing information on long duration deep space missions; “Project BAIR: the Black Hole Augmented Interstellar Rocket”, authored by Andrew Alexander, which discussed a black hole engine that utilised the Hawking radiation effect; “Program to Characterise the Local Stellar Environment” authored by Shambo Bhattacharjee. The committee is also currently launching a project relating to von Neumann machines and the Universal Constructor Project. The vision is to enable small interstellar probes to have the capability to build space infrastructures autonomously.
The Sustainability & Research Committee is chaired by Professor Rachel Armstrong and has the purpose of seeking space-based technological solutions to solving problems on Earth and in space, human made or environmental, and improving the human condition and harmonising cultural relations. Through this committee we have begun a relationship with a team of architects and initiated discussions on innovative technologies for the future that we can bring to our metropolis. The committee has also instigated the exciting ‘Starship Cities’ programmes, which seeks to develop the technologies for our society that can truly prepare us for the world ship journeys of the future. This includes looking at living architecture technologies such as protocells, and the ability to utilise them as a form of programmable matter and as a mechanism to simulate biological computing. In the last year the committee also completed a project with the International Space University titled “Biological Life Support Systems for Future Spaceflight Missions” authored by Brian Ramos. The committee is also looking at an innovative experimental architectural platform, upon which many types of experiments could be conducted on an iterative learning basis.
The Business Enterprise Committee is chaired by myself and has the purpose of encouraging entrepreneurship and business innovation initiatives related to the objects. We are currently exploring models for nurturing start-ups and aiming to develop a facilitation scheme over the next year. In addition, the committee is also in discussions with various private inventors about bringing potential products to market to benefit the community. One new company for which we have helped to nurture to fruition is Nebula Sciences (www.nebulasciences.com). This is a company led by Sam Harrison, who also serves on our Enterprise Committee, and conducts high altitude balloon launches into the upper stratosphere. That company is now working with multiple aerospace and marketing ventures throughout the world. The same team earlier placed the i4is logo at 89,000 ft, which was a milestone achievement for us, and demonstrates we are not just talking about theoretical developments.
Image: The i4is Logo at 89,000 ft in the stratosphere
As of our three year anniversary, our team has published over 100 papers, reports, articles and essays, has given over 50 presentations, has produced nearly 100 external and internal blog articles, has held over 30 formal team meetings and around 100 informal team meetings, has been involved with over 50 other external organisations, has participated in over 40 different international events, and today has around 70 people directly involved in our activities in one form or another. We have had media articles in multiple international publications and have participated in online podcasts and radio shows. We have attended or presented at events across the globe, throughout the United Kingdom, Europe and the United States. As a part of our participating in the London World Science Fiction convention 2014, our team also built a 4 m tall monolith in what may be a world record (anyone?). Our packed out session at this exciting venue included talks from the world renowned science fiction authors Gregory Benford, Stephen Baxter and Alastair Reynolds.
Image: Our Monolith displayed at Loncon3.
We have produced much of our own merchandise including t-shirts, post-cards and a calendar. One of our proudest and longest running achievement is the publication of our popular magazine Principium, and we are currently working on our twelfth issue. This is a popular publication for the community, and we always try to have an article on other organisations activities to help promote their work.
Image: Principium, the popular magazine of i4is.
We also have published our very own book “Beyond the Boundary” which had contributions from other 20 different authors associated with our subject [http://www.lulu.com/shop/http://www.lulu.com/shop/kelvin-long/beyond-the-boundary/hardcover/product-22028046.html]. And just to show that we are technologically minded, we have also developed our very own educational iPhone app. We have also been working with the inspirational artist and musician Alex Storer, and we are now on our fourth interstellar themed music album. This all proves we are engaging the both the arts and the sciences as we attempt to communicate the vision of interstellar travel. We have also recently just launched our own academic journal, Axiom, and we are now working on our second issue.
Image: Music albums, a journal and smartphone app of i4is.
So what about the future? Well, we are currently looking at facilities to host our Head Quarters and our team has visited many locations over the last couple of years and we are excited about the prospect of hosting interstellar events from such a facility. We are also working on another volume of the “Beyond the Boundary” book, as well as more issues of Principium and Axiom. We continue to attend events and this month we are attending Novacon, a science fiction convention held in Nottingham, UK, every year. Our team are busy working on papers for journals and various research projects from which we hope to see progress towards our goal made. We have also recently launched our supporting membership scheme (get in touch if you want to join) and we are planning to extend this in 2016. We are also keen to recruit more active volunteers to help out with our many activities.
One of the things I am personally keen to do in the future is to address how we can take this interstellar community onto the next level. That is, towards a path of constructive co-operation, resource sharing, and more focussed goal setting through inspirational leadership. One proposal I have made towards this, is the formation of an International Interstellar Committee, which would hold a bi-annual interstellar conference for which all of the community would help organise and participate in. Such a body would contain individual organisational membership, preserving their individual identifies and self-autonomy, whilst facilitating a global voice and finding synergies in strategies. It is my opinion, that such an entity may be needed if we are to find ways of harmonising relationships among different groups, but for all have their hearts set on the same goal.
Some still view our endeavours as premature, given the state of human space exploration to date. But I rather believe that now more than ever, there is the need for a visionary stretch goal to focus the energies of our fragmented civilisation. The vision of the stars gives us such promise, about the discovery of other worlds or new life forms. Its such an exciting journey to be a part of and it also has transformation potential for human civilisation, so that we can start to address the universe on its own terms, whether we live in a crowded galaxy, or if we are the only intelligent life out there. I for sure, would like to find out – so let’s build those starships in our lifetime, and go forth with less of our weaknesses and more of our strengths, as a unified people, embracing discovery and adventure as a primary goal. Personally, I can’t think of anything more fulfilling to dedicate one’s life too. At the Initiative for Interstellar Studies, we are making some progress towards that goal.
by Paul Gilster | Mar 26, 2015 | Deep Sky Astronomy & Telescopes |
‘Classical’ SETI, if I can use that term, is based on studying the electromagnetic spectrum primarily in the radio wavelengths thought most likely to be used for communication by an extraterrestrial civilization. SETI’s optical component is largely focused on searching for signals intended as communication. What is now being called Dysonian SETI is a different approach, one based on gathering observational evidence that may already be in our archives, data that demonstrate the existence of extraterrestrial activity far beyond our capability.
Just as a Dyson Sphere would reveal the workings of a civilization of Kardashev Type II — producing something like ten billion times the energy of a Type I culture — the detection of a starship would show us technology in action, even if the craft were, as Ulvi Yurtsever and Steven Wilkinson have speculated, a vehicle pushing up against light speed millions of light years away. As physicist Al Jackson has tackled starship detection in recent years, he has taken note of the work of D. R. J. Viewing and Robert Zubrin, which dealt with some but not all design and detection possibilities. Beamed propulsion, for example, does not turn up in these sources.
Jackson also points to a caveat in such work: If we are hoping to detect a starship using many of the methods described in previous studies, we need to be inside the engine’s exhaust cone or the transmitter cone of the energy beam. We also know that the cone will be narrow. Even so, there are a number of ways to proceed, ranging from the craft’s interactions with the interstellar medium to detection of its own waste heat.
Image: Physicist Al Jackson. I can’t remember who took this (it may even have been me).
Imagine a highly advanced ship built by a Kardashev Type II civilization. Give it a gamma factor of 500, which translates to 0.999998 times the speed of light. Assume the ship is as hot as 5000 K (near the melting temperature of graphene). All these are extreme assumptions (see below) but we’re pushing the envelope here. This is, after all, K2.
Would we be able to detect such a craft? Waste heat can be modeled as isotropic radiation, says Jackson, in the rest frame of the ship, while to an observer in another inertial frame, this radiation appears beamed. We get this result:
Considering a ship of modest size and mass, a K2 ship accelerating at one gravity. For instance, if we have a ship 1000 meters long and 50 meters in diameter, generating 11402 terawatts in its rest frame, Doppler boosting will generate approximately 1.2×108 terawatts beamed into the forward direction. However… unless the ship is headed straight at the observer, it will be hard to see. Take into account the Doppler shifting of the characteristic wavelength, from near green in the rest frame to soft x-ray in the observer’s frame. One might look for small anomalies in data from a host of new astrophysical satellite observatories.
Not very encouraging, but then, detecting the signature of a starship is not going to be easy. One possible place to look is in the realm of what Jackson calls ‘gravitational machines,’ such as the massive binaries Freeman Dyson once suggested could be used as gravitational slingshots. We might consider not just white dwarf and neutron star binaries but even black hole binaries. A gravitational assist in such scenarios might reach as high as .006c.
On the other hand, wouldn’t a civilization that could already reach binaries like these have acquired capabilities greater than those it would gain by using the binaries in the first place? Perhaps better to consider black holes as a source of direction change for fast-moving starships. Jackson points out that a starship orbiting a black hole will have visible waste radiation. In fact, a close-orbiting ship will have fluctuating emissions peaked at those times that the ship, black hole and observer line up, a phenomenon that is the result of gravitational focusing.
Other extreme astronomical objects may be worthy of investigation in these terms. Jackson points to SS 433, a neutron star or black hole orbited by a companion star, with material being drawn from the companion into an accretion disk. Jets of particles are being blown outward from the poles. While at SS 433 the particles in the jets are moving at 26 percent of the speed of light, jet material in configurations like these can reach 95 percent of lightspeed. Using such jets to propel magsails that reach .5 times the speed of light would allow a K2 civilization an abundant source of energy for repeated missions at a high percentage of c.
Image: Magsail ‘jet riding’. Credit: Doug Potter.
We don’t know what a K2 civilization will choose to do, but exploiting naturally occurring resources like these may be an attractive proposition. There may be interesting prospects not just for magsails but so-called ‘lightsails’ around extreme astronomical objects:
Consider a K2 civilization taking advantage of a Schwarzschild or Kerr black hole as a means of focusing radiation from a beaming station onto a sail. The advantage of this is the tremendous amount of amplification possible. One of the most promising modes of interstellar flight propulsion is the use of a sail, a transmitter, and maybe a ‘lens’ to focus a beam of laser light or microwaves. Extrapolate to a K2 civilization the use of a black hole as the focusing device. An approximate calculation for a Schwarzschild black hole shows that beamed radiation can be amplified by a factor 105 to 1015.
So-called ‘strong focusing’ is tricky to model and, as Jackson explains in some detail, the astronomical configuration — the location of a source and the best location for the sail — are topics that need much more work. But the idea that a K2 civilization would use the immense energies available in the area of black holes makes them a natural hunting ground for Dysonian SETI activity. Could a black hole in the vicinity of a starship’s destination be used for braking?
Robert Bussard’s 1960 paper on interstellar ramjets posited a spacecraft that could collect gas from the interstellar medium, compressing it to a plasma that could be brought to fusion temperatures. Carl Sagan would later suggest that a magnetic scoop would be the ideal way for this gas collection to proceed, but later work by Dana Andrews and Robert Zubrin revealed how much drag such a magnetic scoop would produce. The ‘magsail’ actually acts like a brake.
Why not, then, use these magsail properties, shedding energy and momentum as a spacecraft nears its destination? Craft moving at relativistic velocities might find this an efficient way to arrive, one that produces a ‘bow shock’ whose radiation ranges from the optical to the X-ray bands. “A starship will be much smaller than a neutron star,” writes Jackson, “but detection of the radiation signature of a starship’s bow shock could imply a very peculiar object.”
Image: Two examples of neutron star bow shock, the one on the right an artist’s concept. Credit: Wikimedia Commons.
Jackson’s paper is a work in progress, with an early version printed in Horizons, the AIAA bulletin for the organization’s Houston chapter. A journal submission is in the works as he refines the draft. It’s a fascinating discussion that reminds us how much we have to speculate about when we talk K2 civilizations. Jackson notes the major assumptions: Ships can run ‘hot,’ and that means as high as 5000 K; material structural strength limits have been overcome; extreme accelerations are allowable and dust/gas shielding issues resolved. We can argue about the limits here, but it’s clear that a K2 civilization will have capabilities far beyond our science, and it may be the random anomaly in astronomical data that flags its existence.
by Paul Gilster | Sep 26, 2014 | Culture and Society |
I don’t envy the track chairs at any conference, particularly conferences that are all about getting large numbers of scientists into the right place at the right time. Herding cats? But the track model makes inherent sense when you’re dealing with widely disparate disciplines. Earlier in the week I mentioned how widely the tracks at the 100 Year Starship Symposium in Houston ranged, and I think that track chairs within each discipline — already connected to many of the speakers — are the best way to move the discussion forward after each paper.
Still, what a job. My friend Eric Davis, shown at right, somehow stays relaxed each year as he handles the Propulsion & Energy track at this conference, though how he manages it escapes me, given problems like three already accepted presentations being withdrawn as the deadline approached, and one simple no-show at the conference itself. Unfortunately, there were no-shows in other tracks as well, though the wild weather the night before the first day’s meetings may have had something to do with it.
Processes will need to be put in place before future symposia to keep this kind of thing from happening. Fortunately, Eric is quick on his feet and managed to keep Propulsion & Energy on course, and I assume other track chairs had their own workarounds. A high point of the conference was the chance to have dinner and a good bottle of Argentinian Malbec with Eric and Jeff Lee (Baylor University), who joined my son Miles and myself in the hotel restaurant.
The Antimatter Conundrum
I found two papers on antimatter within Eric’s track particularly interesting given the challenge of producing antimatter in sufficient quantity to make it viable in a future propulsion system. We’d love to master antimatter because of the numbers. A fusion reaction uses maybe one percent of the total energy locked up inside matter. But if you can annihilate a kilogram of antimatter, you can produce ten billion times the energy of a kilogram of TNT. In nuclear energy terms, the antimatter yields a thousand times more energy than nuclear fission, and 100 times more energy than fusion, a compelling thought for interstellar mission needs.
Sumontro Lal Sinha described the requirements for a small, modular antimatter harvesting satellite that could be launched into the Van Allen radiation belt about 15,000 kilometers up. I was invariably reminded of James Bickford’s ideas on creating an antimatter trap in an equatorial orbit around the Earth that could harvest naturally occurring antiparticles — Bickford has always maintained that space harvesting of antimatter using his ‘magnetic scoop’ is five orders of magnitude more cost effective than producing antimatter on Earth. In any case, antimatter resources here and elsewhere in the Solar System offer useful options.
Remember that the upper atmosphere of the planets is under bombardment from high-energy galactic cosmic rays (GCR), which results in ‘pair production’ as the kinetic energy of the GCR is converted into mass after collision with another particle. Out of this we get an elementary particle and its antiparticle. Planets with strong magnetic fields become antimatter sources because particles interact with both the magnetic field and the atmosphere. Sinha’s harvester would be an attempt at pair-production that he describes as lightweight and modular. I haven’t seen a paper on this one so I can’t go into useful detail. I’ll hope to do that later.
Storing macroscopic amounts of antimatter for propulsion purposes is the other side of the antimatter conundrum, an issue tackled by Marc Weber (Washington State), who described long antimatter traps in the form of stacks of wafers that essentially form an array of tubes. Storage is an extreme issue because like charges repel, so that large numbers of positrons, for example, generate repulsive forces that magnetic bottles cannot fully contain. Weber’s long traps are in proof-of-principle testing as he tries to push storage times up.
Image: One of Marc Weber’s slides, illustrating principles behind a new kind of magnetic storage trap for antimatter.
Thermonuclear Propulsion and the Gravitational Lens
It’s always a pleasure to see old friends at these events, and I was happy to have the chance to share breakfast with Claudio Maccone, whose long-standing quest to see the FOCAL mission built and flown has come to define his career. But in addition to speaking about the gravitational lens at 550 AU and beyond, Claudio was in Houston to discuss the Karhunen-Loève Transform (KLT), developed in the 1940s to improve sensitivity to artificial signals by a large factor, another idea he has long championed. The idea here is that the KLT has SETI applications, helping researchers in the challenging task of sifting through signals that may be spread through a wide range of frequencies.
Consider our own civilization’s use of code division multiplexing. Mason Peck was also talking about this at the conference — the reason you can use your cellphone in a conversation is that multiple access methods (code division multiple access, or CDMA) allows several transmitters to send information simultaneously though using the same communications channel. Spread-spectrum methods are at work — the signal is sent over not one but a range of frequencies — and you’re actually dealing with a combination of many bits that acts like a code. If we’re using these methods, perhaps a signal we receive from an extraterrestrial civilization may be as well, and perhaps the best way to unlock it is to use the KLT.
I missed Claudio’s session on the KLT but was able to be there for his talk on using the gravitational lens as a communications tool. Beyond the propulsion question, one of the biggest problems with putting a probe around another star is data return. How do we get a workable signal back to Earth? Fortunately, the gravitational lens can offer huge gains by employing the focusing power of the Sun on electromagnetic radiation from an object on the other side of it. Using conventional radio communications would require huge antennae and substantial (and massive) resources aboard the probe itself. These would not be necessary if we fly the needed precursor mission to the distances needed to use the gravitational lens.
Thus we send a relay spacecraft not toward Alpha Centauri but in exactly the opposite direction. Ordinary radio links can be easily maintained. If we tried conventional methods using a typical Deep Space Network antenna and a 12-meter antenna aboard the spacecraft (assuming a link frequency in the Ka band, or 32 GHz, a bit rate of 32 kbps, and 40 watts of transmitting power), we still get a 50 percent probability of errors. A relay probe at the gravitational lens, however, shows no bit error rate increase out to fully nine light years.
I’m moving quickly here and I can’t go through each presentation, but I do want to mention as well Friedwardt Winterberg’s talk on thermonuclear propulsion options. Dr. Winterberg has a long history in researching nuclear rocketry, dating back to the days of Ted Taylor, Freeman Dyson, and the era of Project Orion (which he could not join because he was not yet a US citizen). The Atmospheric Test Ban Treaty of 1963 was one of the factors that put Orion to rest, but Fred has been championing nuclear micro-bombs with non-fission triggers, an idea he first broached at a fusion workshop all the way back in 1956. His most recent paper reminds us of von Braun’s ideas about assembling a huge fleet in orbit for the exploration of Mars:
A thermonuclear space lift can follow the same line as it was suggested for Orion-type operation space lift, but without the radioactive fallout in the earth atmosphere. With a hydrogen plasma jet velocity of 30 km/s, it is possible to reach the orbital speed of 8 km/s in just one fusion rocket stage, instead of several hundred multi-stage chemical rockets, to assemble in space one Mars rocket, for example. .. The launching of very large payloads in one piece into a low earth orbit has the distinct advantage that a large part of the work can be done on the earth, rather than in space.
Exactly how to ignite a thermonuclear micro-explosion by a convergent shockwave produced without a fission trigger is the subject of the new paper, and I’m looking for someone more conversant with fusion than I am to give it a critical reading to be reported here. The basic Orion concept remains in Winterberg’s work with fission bombs replaced by deuterium-tritium fusion bombs being set off behind a large magnetic mirror rather than Orion’s pusher plate.
All Too Little Time
So many papers occurred in different tracks at conflicting times, exacerbated by the need to attend advisory board meetings, so I missed out on a number of good things. I wish I could have attended Kathleen Toerpe’s entire Interstellar Education track, and there were sessions in Becoming an Interstellar Civilization and Life Sciences in Interstellar that looked very promising. I hope in the future the conference organizers will set up video recording capabilities in each track, so that attendees and others can catch up on what they missed.
Several upcoming articles will deal with subjects touched on at 100YSS. Al Jackson is writing up his SETI ideas using extreme astronomical objects, and I’ll be talking about Ken Wisian’s paper on military planning for interstellar flight — Ken and his lovely wife joined Heath Rezabek, Al Jackson, Miles and myself for dinner. The conversation was far-ranging but unfortunately the Friday night restaurant scene was noisy enough that I missed some of it. Miles and I stopped down the street the next night at the Guadalajara, a good Mexican place with a quiet upstairs bar. Great margaritas, and a fine way to close out the conference. Expect an upcoming article from Miles, shown below, on his recent interstellar presentation in a seriously unconventional venue. I’m giving nothing away, but I think you’ll find it an encouraging story.
by Paul Gilster | Sep 25, 2014 | Sail Concepts |
India can take great pride in the successful insertion of its Mangalyaan Mars probe into orbit around the red planet. At a cost of $75 million, the spacecraft is a bargain — Maven, which entered Mars orbit on Sunday, cost almost ten times as much. In an Associated Press story this morning, I noticed that B. N. Raghunandan (Indian Institute of Science) said that every time India launches another rocket, he is besieged with students asking how they can enter his school’s aerospace program. It’s the same effect I was talking about yesterday, in which inspirational achievements drive cultural perceptions and influence careers.
Meanwhile, I want to tackle solar sails this morning, prompted by Les Johnson’s presentation at the 100 Year Starship Symposium in Houston last week. What caught my attention here was the positive news Les had to share about what’s ahead in the pipeline. But to put it into context, let’s think about what has already flown in space. The Russian ‘sail mirror’ experiments called Znamya were pitched as an attempt to light up Siberian cities at night, but of course can be considered experiments in sail deployment, the first successful in 1993, the second a failure when it became entangled on an antenna on the Mir space station.
Image: Les Johnson (left) and Al Jackson. The latter, by the way, presented some startling ideas in Houston about how an extraterrestrial culture might use astronomical objects — including neutron stars and black holes — as ways of flagging its existence to other cultures. Al is writing up these SETI ideas for a future article on Centauri Dreams.
Since then we’ve had IKAROS, which flew as a secondary payload on a Venus mission, was spin-deployed, and is still active in and around the orbit of Venus. This is a story that caught a lot of people by surprise. I remember when I was watching the launch of this mission online and my wife came into the room. Looking over my shoulder, she asked what I was watching. “The Japanese are launching a solar sail,” I replied. She was headed out of the room as I responded, then came back. “You’re kidding,” she said, and just stood there watching.
The early success of IKAROS was a surprise to me because we had seen ground deployment experiments from NASA as well as from DLR, the German Aerospace Center, and a lot of us took our eye off what was going on with JAXA, the Japanese space agency. IKAROS was and is a thumping success, and one that deployed an ingenious electro-optical material to vary the brightness of parts of the sail in order to maneuver. That gets around trying to ‘tack’ the sail as one would with a conventional wind sail on the ocean, and Johnson said it was a marker for the future — the plan will be to avoid mechanical systems wherever possible, to keep things simple.
NASA’s NanoSail-D sails were actually cut down from one of the earlier 20 square meter ground deployment test sails, the first launched and lost in the attempt, the second (NanoSail-D2) successfully achieving orbit. Keep in mind that NanoSail-D, a 10 square meter sail, was not only a deployment test but also a look at how satellites might be de-orbited, using a small sail to create enough atmospheric drag to cause the satellite to burn up upon re-entry. There was no NanoSail model A, B, or C, by the way — the D has been variously said to stand for ‘demonstrate,’ ‘deploy,’ ‘drag,’ and ‘de-orbit,’ so you can take your pick.
And look at everything that’s coming up. The Planetary Society’s CubeSat-based sails, LightSail-A and LightSail-B, both using an aluminized 4.5 micron mylar film and sails of 32 square meters is on the horizon. We’re looking at April of next year for the first LightSail launch, which could well herald the era of small CubeSat missions driven by sail propulsion to Mars and other planets. NASA’s Sunjammer is also in the mix, though I’m waiting on a clarification from the builders as to its flight status.
Beyond LightSail, we have three different versions ranging in size up to 50 square meters of the European Space Agency’s Gossamer sail, the first of which has already been built and is awaiting a launch date. Developed in tandem with Germany’s DLR, the sails are designed as technological demonstrators with increasing levels of complexity in a scalable design. The first deployment will be of a 5 meter by 5 meter sail in a 320 kilometer Earth orbit, to be documented by at least four onboard cameras. The intermediate sail is 20 X 20 meters.
Image: The ESA/DLR Gossamer sail in an artist’s impression. Credit: ESA.
I’ll be looking in future days at some of the other possibilities, which include the University of Surrey’s CubeSail, with three CubeSat sail missions slated to fly in the next three years (emphasis here on de-orbiting spacecraft in low-Earth orbit), and the CubeSat-based Near Earth Asteroid (NEA) Scout, a solar sail prospector designed for eventual rendezvous with multiple NEAs to evaluate their possibilities for mining. And then there’s Lunar Flashlight, a CubeSat mission out of the Jet Propulsion Laboratory and Marshall Space Flight Center which will orbit the lunar poles to look for signs of water at the south pole.
As to JAXA: The long-range plan is to develop a joint ion propulsion/sail mission to the outer planets, so it’s clear that Japan will remain a force to be reckoned with in sail technology
Johnson pointed out that the key for our future sail ambitions is to learn how to make large sails in space. The worst place to work on a sail is on the ground, in a gravity well — we have to launch and safely deploy these huge structures. Most people watching the sail scene believe that we’ll ultimately be building sails that dwarf these early efforts in space using materials we’ve harvested from the asteroids. Then we can start the ramping up of sail technologies for true interstellar precursors.
