Centauri Dreams
Imagining and Planning Interstellar Exploration
Long: Toward an Interstellar Institute
Today we continue with responses to the Request for Information from the 100 Year Starship study. Kelvin Long is senior designer and co-founder of Project Icarus, the ambitious attempt to design a fusion starship. A joint project of the British Interplanetary Society and the Tau Zero Foundation, Project Icarus takes its inspiration from the original Project Daedalus, updating and extending it with new thinking and new technologies. Here Kelvin considers how a research organization tasked with developing something as ambitious as a starship can function and prosper. And he would have considerable insight into the matter — as a Project Icarus consultant, I’ve never seen so dedicated and energetic a team as the one he put together. Its final report will be an essential work in interstellar propulsion studies.
Kelvin Long completed his Bachelors degree in Aerospace Engineering and Masters degree in Astrophysics at Queen Mary College, University of London. He is a Fellow of The British Interplanetary Society, Fellow of the Royal Astronomical Society, Member of the American Institute Aeronautics & Astronautics, a Chartered Physicist and a Practitioner of The Tau Zero Foundation. He has published numerous articles and papers on various aspects of space travel. His Ph.D work is on the topic of Inertial Confinement Fusion, a key player in both the Daedalus and Icarus designs.
Kelvin F Long[ref]Note that the author is a British National based in the United Kingdom.[/ref]
BEng Msc CPhys FBIS FRAS MAIAA
Icarus Interstellar & Tau Zero Foundation (non-profits)
Abstract
This is a response to the DARPA solicitation requesting information for the 100 Year Starship Study. Preliminary ideas for a (long term) research model and Interstellar Institute for Aerospace Research (IIAR) are presented. The views expressed in this document represent the authors only and not the official views of Icarus Interstellar or the Tau Zero Foundation. This paper is a submission of the Project Icarus Study Group.
1 Introduction
The ambition of interstellar flight has been the subject of many science fiction novels [1-3] and continues to inspire a large number of academic papers and books [4-9]. Despite this interest, it has generally been the public belief that interstellar flight is speculative engineering. In 1969 man landed on the Moon, but before that stupendous achievement could be realized it had to first be demonstrated that such a thing was possible. Hence in the 1930s members of the British Interplanetary Society (BIS) undertook a study for a Lunar Lander [10], presenting the first such engineering concept and moving the subject from speculative fiction to credible engineering. Similarly, before the first interstellar probe can be launched it must first be demonstrated that such a thing is feasible. In the year 2033 the BIS will have reached its 100th anniversary and its Journal, JBIS, has been the home of visionary thinking since its first publication in 1934 – it is the oldest astronautical Journal in the world [11]. Members of the BIS were also the first in history to publish an academic paper on the subject of interstellar flight [12] and in the 1970s members pioneered the future by the design of a theoretical Starship called Project Daedalus [13]. Using an inertial confined fusion based propulsion system the probe would reach its stellar target in around half a century. Project Icarus was founded in 2009 and is an international project to redesign the Daedalus vehicle with modern knowledge as a ‘designer capability’ exercise [14]. An international team has been assembled and is hard at work on the calculations in a (volunteer) capacity. All of the above demonstrates that the “First Steps” towards the stars have already been made in advance of the DARPA RFI. The “Second Step” (for DARPA, TZF or others) is to bring this research together into a century long co-ordinated program. In reality, the first interstellar probe launch is likely at best one to two centuries away as has been consistently demonstrated [15-18]. To launch even an unmanned interstellar probe in advance of the year 2100 would likely require significant and sustained technology investments several times greater than those of today [19].
The means by which the first interstellar probe is to be propelled remains a matter of discussion awaiting technological breakthroughs. Although some clear contenders have emerged in recent decades, from external nuclear pulse [20], to fusion engines [21], to sail beaming systems [22-24]. Other more exotic alternatives includes antimatter based systems [25] or the use of interstellar ramjets [26] which requires no on vehicle propellant. One aspect that could changes all this is the discovery of a breakthrough method of propulsion physics such as proposed for the famed warp drive of science fiction, now the subject of rigorous metric engineering using the tools of General Relativity and Quantum Field Theory [27-29]. The potential for such propulsion systems (as well as others) and how to manage such research has been well studied by others [30-31]. The launch of human based Starships will require massive engineering and therefore large infrastructure requirements, as evidenced by studies of Worlds Ships [32-33], placing it many centuries into the future. Other than Project Orion and Project Daedalus, various vehicle design studies have been undertaken historically that are relevant to the design of a Starship, to differing degrees of engineering accuracy. This includes VISTA [34], AIMStar [35] and the student study LONGSHOT [36], for example.
How can the pace of interstellar research be accelerated so as to facilitate an earlier launch window? One method is to think about the interstellar roadmap by planning interstellar precursor missions which go to 200 AU, 1000 AU and beyond. Several such proposals have been made over the years [37-40]. What makes such proposals feasible (as well as the full interstellar missions) is consistency with the Technology Readiness Levels [41]. These are the guiding tool for all aerospace development even at national space agencies [42] and the emphasis for bringing about an interstellar mission must be to encourage and facilitate research into low TRL (~1-3) propulsion schemes and other technologies. An approach for the planning of visionary technology development programmes, the Horizon Mission Methodology, has been constructed and is an ideal tool for this purpose [43]. Although in past generations significant (largely theoretical) progress has been made towards the eventual launch of the first interstellar mission, this research has been largely uncoordinated, unfocussed and performed by volunteers. If the first launch of an interstellar probe is indeed to take place in the next two centuries, then what is required is a change of strategy to include a significant investment program and the formation of an Interstellar Institute for Aerospace Research (IIAR). The proposal for an Interstellar Institute has also been made by the former NASA physicist and current President of the Tau Zero Foundation Marc Millis, in private communication, and this is one of the long term aspirations of the Foundation.
An Interstellar Institute would coordinate research relating to all aspects of an interstellar mission, from the manufacturing and assembly, launch and construction, fuel generation or acquisition, to communications and science monitoring. Such a body should also encourage research spanning the range of propulsion options. By not closing off any options today each method progressives incrementally until a front runner clearly emerges – ad astra incrementis. The Institute logo spells out the letters of the name. The trajectory of a spacecraft is shown, passing three stars which get progressively larger, emphasising that with incremental steps the stars will get closer. The spacecraft exceeds the position of the stars and continues out into the galaxy showing that with visionary (but credible) goals anything is possible. The Institutes motto would be along the lines “Leading Astronautical Research to the Stars”, emphasising academic rigour in all studies.
2 Research Model
In this document we describe an optimistic (long term) vision for an Interstellar Institute manned by permanent staff, hosting resident academics and assuming the support of wealthy philanthropist(s) to get it started (but not to sustain it). If there were an Interstellar Institute this would attract academics from around the world to come together for weeks or months at a time to jointly work on some of the major technical issues or explore a new area of physics where a fundamental breakthrough in our understanding may come. Design teams could also be assembled to work on specific problems, such as: development of technology for the unfurling of a solar sail in deep space; engineering an interstellar ramjet; reducing the negative energy requirements of a warp drive; or finding ways of mining Helium-3 from the gas giants in a cost effective way. The basis of all research will be to improve the Technology Readiness Levels of a diverse range of spacecraft technologies, particularly pertaining to propulsion. It would also be the location for a major conference and would act as the international focus point for all interstellar related research. This is what we need to make interstellar research move substantially forward and allow innovative ideas to emerge and be applied efficiently to the progression of the subject. It needs to be moved from the volunteer sidelines of science, given some major investment, and an institute to focus the research and provide an exciting atmosphere where an optimistic vision for space exploration exists. The Aim, Vision and Mission of the Institute are described as follows:
- Aim : To co-ordinate and facilitate international research excellence towards solving the engineering and physics obstacles associated with interstellar flight and to spur technological breakthroughs.
- Vision : To encourage robotic and human missions to the stars in the coming centuries.
- Mission : [1] To be proactive in co-coordinating international research associated with international flight and to demonstrate research leadership in the field of astronautics [2] To conduct outstanding educational activities to better communicate to the public the importance and the credible feasibility of interstellar flight [3] To work towards an agreed set of short, medium and long terms goals that are consistent with the Institutes optimistic vision for interstellar flight.
2.1 Organizational Governance & Finance Model
A non-profit organization manned largely by volunteers does not have the man power or resources to undertake a large scale research program greater than 10s of people. A business does have this capacity but is subject to risks associated with financial markets and competition. Government can protect itself against risk and can manage large scale programs; however, inherent bureaucracy, micro-management and leadership changes due to changing political policies create an environment that is unstable, costly (usually measured in billions of dollars) and over time become less flexible to positive innovation and change. The best strategy therefore is to combine the best of all three structures whilst throwing away the worst parts.
The cost of the Institute construction is expected to be of order ~$30-50 million. The cost of the initial research investment program is expected to be of order ~$100 million. Annual funding programs of order ~$10-20 million per year are expected until self-revenue generation emerges. In essence the Institute is a non-profit research body, more similar to a University rather than an industrial company, which specialises in research and academic educational programmes in physics and engineering relating to deep space missions.
The Interstellar Institute would be founded around the year 2020, allowing time for sufficient planning and construction work. The initial start fund program to begin the planning stage is of order several hundred thousand dollars, consistent with the DARPA RFI. The funding structure is described in the diagram above, with innovative technologies leading to patents and new engineering products for space. The organisation that comes closest to this model is the Perimeter Institute for Theoretical Physics in Waterloo, Canada, which was founded in 1999 by Mike Lazaridis who owns the Blackberry Company. New Scientist has said of PI: “…what may be the most ambitious intellectual experiment on Earth” [44]. The Interstellar Institute can exceed this by reaching for new heights in intellectual leadership and turning the energies of international groups of volunteers into a coordinated research programme that is focused on the launch of the first interstellar probe in this century or the next.
2.2 Organizational Structure
The Institute would be an independent non-profit organized with a Technical Advisory Committee acting as the Board of Directors to oversee all activities. A core membership would support the non-profit status. The core of its work program consists of three elements:
1. Theoretical research to produce breakthrough solutions to problems in physics and engineering relating to deep space missions utilizing a variety of propulsion systems and technologies, including concept development for real spacecraft designs.
2. Education to bring about a greater awareness of the viability for future interstellar missions and how they might impact our cultural and technological growth.
3. Public outreach to communicate the vision and feasibility of interstellar travel and inspire the world that such a vision is essential to a secure and peaceful future for the human race in space.
Additionally, the Institute may undertake the following two activities:
1. Laboratory based experiments to improve the Technology Readiness Levels of key systems and sub-systems likely required for a deep space mission.
2. Contributions to actual space missions by development of a sub-system that would be required for a deep space mission.
The majority of the work undertaken by the Institute is expected to be theoretically based (~70%), performed by the visiting academics, with perhaps a minor element (~10%) dedicated to actual laboratory and space environment mission development. The remainder of the program will be dedicated to education and public outreach (~20%). Typically the Institute would consist of around 30 administrative and facility staff, 20 research co-coordinators and around 150-200 resident researchers, of which two thirds would be visiting. All staff will be designated Support, Management, Resident Researcher or Visiting Researcher. Additionally, non-academics/non- professionals (common in this field) who has showing a grasp of the technical issues may also become visiting residents, awarded on a grant basis, regardless of background.
The educational program would consist of regular symposia and conferences in a lively and dynamic research atmosphere. The highlight would be a bi-annual Conference for Interstellar Flight, reviewing the latest research in the field. One aspect of the outstanding educational program would be an annual summer residential course, taught by a combination of permanent and visiting residents. The course will lead to a Postgraduate Certificate in Interstellar Engineering, to be awarded by a local University with their co-operation and involvement. The syllabus would cover all aspects of spacecraft design technology and mission performance; from communications to structure and materials to propulsion. Orbital mechanics and trajectory analysis would also be included, as well as basic planetary and solar physics science. There is also the potential for creating a full Masters program in Interstellar Engineering, to include a design project, as part of a summer school attended twice in succession. Doctoral research programs may also be possible. The Institute is to be a world leader in the implementation of the latest technologies in the everyday activities of its residents with many symposia and conferences transmitted live to the World Wide Web. On occasions the entrance lounge of the Institute can be easily turned into a banquet hall for conference dinners whilst listening to some cultural music. The entrance hall would also be an exhibition arena showcasing either the latest technologies or artwork which helps us to understand the challenges of humans in space.
The Institute governing structure is now defined.
– Institute Executive: Director Institute; Deputy Director; Executive Committee (Division Heads + selected volunteer external advisors).
– Division of Research Management: Division Head; Deputy Division Head; Building Management; Office Administration; Publications & Media; Building Maintenance (facilities, structure, gardening, health & safety); Business & Finance; Human Resources, Business Marketing & Finance; Archives & Exhibition (museum, library); Catering Facilities; IT Services (maintaining on site computers, networks and supercomputing clusters); Office of Future Developments (expansion of Institute); Office of International Research Co- ordination (co-coordinating residents/sabbaticals); Office of Space Mission Liaison (co- coordinating interactions with commercial/agency spacecraft missions); Office of Laboratory Research (management of on site laboratories or test technology).
– Division of Science & Technology: Division Head; Senior Advisory Committee; Leader Instruments & Payload Group; Leader Computing & Electronics Group; Leader Power Systems & Thermal Control Group; Leader Structure & Materials Group; Leader Risk, Reliability & Spacecraft Protection Group; Leader Space Infrastructure & Vehicle Assembly Group; Leader Space Communications, Navigation & Guidance Control Group; Leader Astronomy & Exploration Group; Leader Human Colonization.
– Division of Reacting Engines: Division Head; Senior Advisory Committee; Chemical Propulsion Group; Electric Propulsion Group; Nuclear Fission Group; Nuclear Fusion Group; Antimatter propulsion Group; Advanced Particles & Fields Group.
– Division of Propellantless Propulsion: Division Head; Senior Advisory Committee; Solar & Microwave Sails Group; Particle Beams Group; Interstellar Ramjets Group; Mass Drivers Group.
– Division of Breakthrough Physics: Division Head; Senior Advisory Committee; Leader Space Drives Group (dean drive, disjunction drive); Leader Metric Engineering Group (warp drive, black holes, worm holes); Leader Particle & Information Transmission (teleportation, tachyons).
3 The Interstellar Institute for Aerospace Research
The building for the Interstellar Institute should be visionary, futuristic and visually stimulating. One example for such a building would be the use of a pyramid shaped structure, a symbol of permanence and the need for long term planning in enduring programmes. It would be constructed of glass with layers of solar panels to supply the electrical energy for the building. Inside would be the building itself, constructed in stages analogous to the stages of a rocket. The ground floor level would contain the main conference hall, cafeteria, open air library, exhibition space and perhaps a Japanese garden. The higher levels would contain smaller conference rooms and offices for permanent and visiting residents working on the problems of interstellar flight. At the top of the building is the observational Skydome, shaped to represent an interstellar payload on top of each engine stage. The Skydome is maintained to low light levels, to allow visualization of the stars at night. Some moderate telescopes are permanently in place for the enjoyment of the visitors. The total floor area inside the pyramid is around 10,000 square meters, being 100 m on each side. The Institute would become the worlds leading centre for research into interstellar flight, promoting research excellence and stimulating scientific breakthroughs. The institute is to be a place of positive inspiration, where the best of humanity comes together to focus on solving the obstacles to the launch of the first interstellar mission.
On the very apex of the building is a high gain radio antenna for the sending and receiving of deep space signals for participation in some monitoring programs. On the first level is the main conference room capable of holding up to 300 people, using modern electronic visualization tools. On the second level is another, but smaller, conference room capable of holding up to 100 people. Small meeting rooms are included on the third and fourth level to hold up to 20 people. Each of the levels has a small balcony and railing which comes off of each office, providing for pleasant views over the arena and Japanese garden. In the middle of the third to fifth floor is a hollow opening allowing windows across the way. At the rear of the building (external to the pyramid) is a small observatory to be used for exoplanet observations to help determine the first astronomical mission target, focussed on stars within 20 light years. Entrance to this is enabled through the Japanese garden which is also a bird atrium. The overall design objective of the building is to inspire the designers, providing for a peaceful and relaxing atmosphere whilst being an innovative design using parallels with engineering technology from interstellar spacecraft designs.
References
[1] Anderson, P, “Tau Zero”, Orion Books, 1970.
[2] Niven, L & J.Pournelle, “The Mote in God’s Eye”, Simon & Schuster, 1974.
[3] Clarke, A.C, “Rendezvous with Rama”, Gollancz, 1973.
[4] Spencer, D.F et al., “Feasibility of Interstellar Travel”, Acta Astronautica, 9, pp.49-58, 1963. [5] Forward, R.L, “A Program for Interstellar Exploration”, JBIS, 29, pp.611-632, 1976.
[6] Gilster, P, “Centauri Dreams, Imagining & Planning Interstellar Exploration”, Springer, 2004.
[7] Matloff, G.L & E.Mallove, “The Starflight Handbook, A Pioneers Guide to Interstellar Travel”, Wiley, 1989.
[8] Long, K.F, “Fusion, Antimatter & the Space Drive: Charting a Path to the Stars”, JBIS, 62, pp.89-98.
[9] Long, K.F, “Deep Space Propulsion: The Roadmap to Interstellar Flight” (book), Springer, Publication Pending
2011.
[10] Ross, H.E, “The BIS Space Ship”, JBIS, 5, 1939.
[11] Parkinson, R, “Interplanetary, A History of the British Interplanetary Society”, BIS Publication, 2008.
[12] Shepherd, L.R, “Interstellar Flight”, JBIS, 11, 1952.
[13] Bond, A & A.R.Martin, “Project Daedalus – Final Report”, JBIS Special Supplement, 1978.
[14] Long K.F., Obousy R.K., Tziolas A.C, Mann A, Osborne R, Presby A, Fogg M, “Project Icarus: Son of Daedalus – Flying Closer to Another Star”, JBIS, Vol. 62 No. 11/12, pp. 403-416, Nov/Dec 2009.
[15] Dyson, F, “Interstellar Transport”, Physics Today, 68, 41-45, 1968.
[16] Cassenti, B.N, “A Comparison of Interstellar Propulsion Methods”, JBIS, 35, pp.116-124, 1982.
[17] Millis, M.G, “First Interstellar Missions, Considering Energy and Incessant Obsolescence”, JBIS, Publication Pending, 2011.
[18] Baxter, S, “Project Icarus: Three Roads to the Stars”, JBIS, Publication Pending, 2011.
[19] Long, K.F, “Project Icarus: The First Unmanned Interstellar Mission, Robotic Expansion & Technological Growth”, JBIS, Publication Pending, 2011.
[20] Dyson, G, “Project Orion – The Atomic Spaceship 1957-1965”, The Penguin Press, 2002.
[21] Long, K.F, R.K.Obousy & A.Hein, “Project Icarus: Optimization of Nuclear Fusion Propulsion for Interstellar Missions”, Acta Astronautica, 68, pp.1820-1829, 2011.
[22] Forward, R.L, “Starwisp: An Ultra-Light Interstellar Probe”, Journal of Spacecraft & Rockets, 22, pp.345-350, 1985.
[23] Landis, G.A, “Beamed Energy Propulsion for Practical Interstellar Flight”, JBIS, 52, 1999.
[24] Benford, G & J.Benford et al., “Power-Beaming Concepts for Future Deep Space Exploration”, JBIS, 59, 2006.
[25] Cassenti, B.N, “Design Considerations for Relativistic Antimatter Rockets”, JBIS, 35, pp.396-404.
[26] Bussard, R.W, “Galactic Matter and Interstellar Flight”, Acta Astronautica, 16, Fasc4, 1960.
[27] Alcubierre, A, “The Warp Drive: Hyper-Fast Travel within General Relativity”, Class.Quantum Grav, 11, L73-L77, 1994.
[28] Long, K.F, “The Status of the Warp Drive”, JBIS, 61, PP.347-352, 2008.
[29] Obousy, R .K & R.Cleaver, “Warp Drive: A New Approach”, JBIS, 61, pp.364-369, 2008.
[30] Millis, M, “Breakthrough Propulsion Physics Research Program”, NASA TM-107381, 1996.
[31] Millis, M & E.W.Davis, “Frontiers of Propulsion Science”, Progress in Astronautics & Aeronautics, 227, AIAA, 2009.
[32] Bond, A & A.R.Martin, “World Ships – An Assessment of the Engineering Feasibility”, JBIS, 37, 6, 1984.
[33] Martin, A.R, “World Ships – Concept, Cause, Cost, Construction & Colonization”, JBIS, 37, 6, 1984.
[34] Orth, C.D, “Parameter Studies for the VISTA Spacecraft Concept”, UCRL-JC-141513, 2000.
[35] Gaidos, G et al., “AIMStar: Antimatter Initiated Microfusion for Pre-cursor Interstellar Missions”, Acta Astronautica, 44, 2-4, pp.183-186, 1999.
[36] Beals, K.A et al., “Project LONGSHOT, An Unmanned Probe to Alpha Centauri”, N89-16904, 1988.
[37] Jaffe, L.D et al., “An Interstellar Precursor Mission”, JBIS, 33, pp.3-26, 1980.
[38] McNutt, R.L, Jr, “Interstellar Probe”, White Paper for US Heliophysics Decadal Survey, 2010.
[39] Long, K.F & R.Obousy, “Starships of the Future, The Challenge of Interstellar Flight”, Spaceflight, 53, 4, 2011.
[40] Maccone, C, “FOCAL – Probe to 550 or 1000 AU: A Status Review”, JBIS, 61, pp.310-314, 2008.
[41] Mankins, J.C, “Technology Readiness Levels”, A White Paper, NASA, 1995.
[42] Schmidt, GR & M.J.Patterson, “In-Space Propulsion Technologies for the Flexible Path Exploration Strategy”, Presented 61st IAC Prague, IAC-10.C4.6.2, 2010.
[43] Anderson, J.L, “Leaps of the Imagination: Interstellar Flight and the Horizon Mission Methodology”, JBIS, 49, pp.15-20, 1996.
[44] “Building on Success – Five year Plan”, Perimeter (PI) Institute for Theoretical Physics, 2009.
Planetary Migration and a Smaller Mars
I’m sometimes asked why I write so seldom about Mars, a very interesting place indeed. The answer is that so many excellent sites are out there tracking events on the planet that I’m happy to keep my focus on the outer system and the starry gulf beyond. But now and then Mars news interrelates with broader stories about planet formation and what we might find in other solar systems. Such is the case with new work from Kevin Walsh (Southwest Research Institute) that looks at the migration of Jupiter during the formation of the Solar System.
At issue is the question of why Mars is so small, because if you run simulations of the planet formation process for the four inner planets of our system, you get a Mars that’s much heavier than the one we see. Tweaking the simulation parameters isn’t enough — it still doesn’t produce the smaller Mars. But a major migration scenario involving Jupiter can help to explain the situation. The trick is that it relies upon an initial distribution of solid material that had to have an outer boundary of about 1 AU, the current average distance of the Sun from the Earth.
That’s a well defined boundary, and it doesn’t fit well with either the asteroid belt (between 2 and 4 AU) or the current parameters of the outer system, including the Kuiper Belt. But numerical simulations have been able to show that both Saturn and Jupiter could have migrated at a time in the early system when gas was still present, moving not only inward but back out again. Such migrations could occur on timescales of as little as 100,000 years. Walsh explains the scenario:
“If Jupiter had moved inwards from its birth place down to 1.5 AU from the Sun and then had turned around because of the formation of Saturn, eventually migrating outwards towards its current location, it would have truncated the distribution of solids in the inner solar system at about 1 AU, as required to explain the small mass of Mars.”
Hydrodynamic simulations reproduce this inward, then outer movement, with Jupiter migrating inward to about 1.5 AU and subsequently moving to its present position, resulting in a truncated planetesimal disk ending at 1 AU. The terrestrial planets would have then formed from this disk over the ensuing 30 to 50 million years, producing planets consistent with Earth and Mars.
Image: An international team of scientists led by Dr. Kevin Walsh of Southwest Research Institute is using complex modeling techniques to better understand the formation of our solar system. The “Grand Tack Scenario” demonstrates that the gas giant Jupiter may have briefly migrated into the inner solar system and influenced the formation of Mars (right), stripping away materials that resulted in its relatively small size in comparison to Venus (left) and the Earth. Credit: NASA.
Walsh began this work while at the Observatoire de la Cote d’Azur (Nice), trying to figure out whether a migrating Jupiter, which would have had to pass through the 2-4 AU region, could be reconciled with the presence of the asteroid belt today. Not only did the simulations show the migration was consistent with the asteroid belt, but they actually helped to explain some features of the belt that have not been understood before. The planetary migration repopulated the asteroid belt with inner-belt objects that originally formed between 1 and 3 AU and outer-belt bodies that originated in and beyond the gas giant planets. Thus we gain insight into why the asteroid belt contains both extremely dry objects as well as bodies that are water-rich.
David O’Brien (Planetary Science Institute), a co-author on the paper, says “The asteroid belt, which was a priori our main problem, turned out to be the main strength of our model.” Walsh calls this model of the peripatetic Jupiter the ‘Grand Tack Scenario,’ likening the motion of the giant planet to a sailboat tacking around a buoy as it makes its great pivot at 1.5 AU. We wind up with a smaller Mars whose mass suggests a story of ancient planetary wandering, and we see a model of gas giant migration that may also give us insight into the kind of migrations that must have occurred in exoplanetary systems, where the orbital distance of gas giants varies widely.
The paper is Walsh et al., “A Low Mass for Mars from Jupiter’s Early Gas-Driven Migration,” published online by Nature 5 June 2011 (abstract).
100 Year Starship Study: A Response
by Marc Millis
“The Defense Advanced Research Projects Agency (DARPA) has initiated a study to inspire the first steps in the next era of space exploration—a journey between the stars.” So reads the Request for Information document (RFI) that DARPA released recently, seeking ideas for organization, business model and approach for a self-sustaining investment vehicle to study these matters. Note that word ‘study,’ because what DARPA talks about in its recent RFI is this: “The 100 Year StarshipTM Study is a project seeded by DARPA to develop a viable and sustainable model for persistent, long-term, private-sector investment into the myriad of disciplines needed to make long-distance space travel practicable and feasible.”
We’ve talked about the 100 Year Starship study before, particularly in Marc Millis’ article on his participation at the first meeting held to discuss the idea. Now Millis, former head of NASA’s Breakthrough Propulsion Physics project and founding architect of the Tau Zero Foundation, is releasing his response to the RFI. In coming days, we’ll look at responses from the Project Icarus team as well, in an attempt to fill you in on where things stand. Look for the Call for Papers for an upcoming conference on the 100 Year Starship study as part of this coverage.
Marc G Millis
Tau Zero Foundation
P.O. Box 26027
Fairview Park, OH 44126
Organizations that can sustain progress for more than a century already exist (universities), but the goal to create starships introduces further challenges. Since acquiring funds, managing endowments, making nominal progress, and longevity are already possible, this submission concentrates on the following less obvious organizational challenges for making the game- changing advances and world-scale investments necessary for star flight:
- Demonstrate that contributions to the new 100-yr starship organization will produce more progress than can be achieved through contributions to existing venues.
- Accommodate world-wide interests and concerns, since interstellar flight is an endeavor that affects all humanity.
- Ensure that the organization stays true to its mission rather than devolving to just serving its managing employees (a common pitfall).
- Balance the need for continually acquiring fresh insights (to avoid group-think, stagnation, parochialism) with the stability needed to stay focused on the mission.
- Provide flexibility to adapt to unforeseeable opportunities and constraints.
- Balance resources across the small seedling investigations needed to discover methods of interstellar flight, with the larger work to apply those discoveries to create mission infrastructure and starships.
- Balance investments across both evolutionary and revolutionary approaches (applying lessons from history about disruptive pioneers).
- Distinguish potentially viable revolutionary approaches (that sound crazy at first), from the more numerous, genuinely crazy ideas.
- Establish win-win intellectual property agreements where top-innovators will choose to work with the 100-yr organization, and where the organization also reaps sufficient returns to sustain its mission.
- Disseminate information responsibly to the public, without disclosing too many technical details that might compromise future revenue generation.
Lessons from different types of organizations:
NASA’s charter makes it the expected organization to create starships, but NASA (and its supporting aerospace community) have evolved per typical patterns to become short-sighted and constrained to their founding legacy. This offers lessons about stagnation and self-absorption.
Educational institutions continue to advance knowledge applicable to interstellar missions, but they do not have the organizational capacity to align and apply all those individual elements to build starships, or the international authority to launch interstellar missions. They also often lack the ability to investigate revolutionary ideas since such ideas pose risk to their reputations. Their revenues include tuitions, licensing of innovations, and huge donations from successful, loyal alumni. Their intellectual resources include a continual flow of young students with fresh ideas, moderated by seasoned professionals.
Professional and public societies, such as the British Interplanetary Society (78 yrs old), provide venues for vetting and advancing new, unconventional ideas, but they lack the infrastructure, coherency, and resources to launch ambitious missions.
Corporations build devices that apply the knowledge gained from universities and societies, but need huge investments to build huge devices (starships) – commitments on the scale of governments. A pitfall of corporations is that they typically follow a pattern of emergence, achievement, and eventual obsolescence. The do not inherently have the longevity to pursue a cause, but rather are optimum for introducing new products.
Governments have the authority and resources to bring such notions to fruition, but are typically mired in internal bickering on near-term crises that preclude applying resources consistently to solve the long-range and difficult-to-comprehend ambitions… until those become a crisis.
And finally, although religious organizations have been used as models for longevity, their product (a belief system) is far easier to produce than scientific discoveries and functional space hardware. Additionally, given competing belief systems (plus righteousness), religions can evoke prejudice and conflicts that can impede the kind of world-scale collaborations needed for interstellar flight.
Scattered amongst all these venues are the elements for discovering methods for, and eventually launching, interstellar missions. Seeking the one best organizational structure to bring this to fruition will be a subjective exercise at best. There is no way to determine, rigorously and impartially, which methods will guarantee success. And if history is any indicator, any structure implemented today will have to adapt to unforeseeable constraints and opportunities. The notion of one, lasting organizational model might not be possible.
Instead, consider this recurring theme in history regarding achieving what was once impossible:
- [Individual level] Pioneers, inspired by the possibilities and having the creativity and competence to make progress, create new knowledge toward solving those grand challenges. (e.g., Tsiolkovsky, Oberth, Goddard, von Braun, etc.)
- [Group level] Those pioneers inspire more people to attempt to implement those visions, and typically volunteer organizations emerge that dabble in those ideas. After cycles of failures and successes, noteworthy progress results. (e.g. the first rocketry clubs, American Interplanetary Society, British Interplanetary Society, etc.)
- [Corporations and Governments] Once a threshold of success has been demonstrated, corporations or governments apply those possibilities to their own interests (e.g., German V2 missiles, American Apollo Moon landing, etc).
While this pattern is not the only way that such things happen, this pattern happens often enough to suggest this strategy:
Find today’s pioneers, support them to accelerate their progress, and then filter out the best prospects. Once sufficiently viable approaches emerge – invest to bring those approaches to fruition.
When it comes to interstellar flight, none of the technical approaches that exist today are fully viable. At least 3 different estimates peg human readiness for an interstellar mission to be roughly 2-centuries away. This topic is still at the stage of finding pioneers and seeing what develops. It is no coincidence that new volunteer societies are emerging, such as the “Tau Zero Foundation,” “Peregrinus Interstellar,” “Project Icarus,” “Life Boat Foundation,” and others that are looking toward pioneering work to solve the challenges related to interstellar flight. This is a natural progression, unfolding today.
Similarly to how DARPA and NASA-Ames are looking outside of NASA to solve these challenges, so too did this author. After leading NASA’s “Breakthrough Propulsion Physics” project that addressed revolutionary ideas to solve the propulsion challenges of interstellar flight, this author realized that NASA was no longer the place for such aspirations. In 2010, an early retirement from NASA allowed full time to be devoted to the “Tau Zero Foundation” – an international network of roughly 40 accomplished researchers and journalists who pursue interstellar flight to provoke longer-range and higher-payoff progress. The foundation’s work is published in various journals and then conveyed to the public via the ‘Centauri Dreams’ news forum
The organizational structure of Tau Zero was designed to take advantage of these historic patterns and avoid the recurring pitfalls. This includes methods to recognize and pursue disruptive, game-changing advances. It also includes methods to find the productive middle ground between wishful thinking and pedantic disdain. And as a result, Tau Zero’s practitioners are making progress. In 2010 they produced 2 books, 13 journal articles (or book chapters), 22 conference presentations, 22 media articles, plus 5 articles-per-week from the Centauri Dreams new forum. These numbers include the continuing progress of “Project Icarus” (design study for a fusion-based interstellar probe) and a few other ongoing projects.
By itself, Tau Zero does not answer all the challenges sought by the 100-yr starship organization. It is still missing a concerted revenue generation scheme, does not have all of the needed topic pioneers, and has no plans to actually launch missions. The presumption is that much research remains before mission implementation is ready to be addressed.
In this short submission, these methods can not be explained in detail, but several details have been published. For this first solicitation from the 100-year starship organization, it is hoped that introducing these issues and methods, along with this bibliography, will provide valuable guidance.
British Interplanetary Society, (continuous), (http://www.bis-space.com/)
Gilster, Paul. (continuous) Centauri Dreams – The news forum of the Tau Zero Foundation, (https://centauri-dreams.org/)
Klien, Eric. (continuous), Lifeboat Foundation, (http://lifeboat.com/ex/main)
Long, Kelvin. (continuous), Project Icarus, (http://www.icarusinterstellar.org/)
Millis, M. G. (2010), First Interstellar Missions, Considering Energy and Incessant Obsolescence. JBIS, 63, (publication pending)
Millis, M. G. (2010), Status Report on the Tau Zero Foundation. Centauri Dreams, 2010/Nov/19. (https://centauri-dreams.org?p=15379)
Millis, M. G. (2010), History Hints at a Decentralization of Future Space Activities, (IAC-10-E6.1.12). 61st IAC Prague, IAF.
Millis & Davis (eds). (2009), Frontiers of Propulsion Science. Vol 227 of Progress in Astronautics and Aeronautics, American Institute of Aeronautics and Astronautics (AIAA). [See in particular Ch. 2 about technology limits, and Ch. 22 about organizational methods]
Pacher, Tibor. (continuous) Peregrinus Interstellar, (http://www.peregrinus- interstellar.net/)
(c) Marc G Millis
CASCA: GJ 581 and More
Canada’s MOST space telescope (Microvariability & Oscillations of STars) has been used to put some constraints on the super-Earth GJ 581e. The work was discussed at this week’s meeting of the Canadian Astronomical Society in Ontario. Planet e is the innermost world among the multiple planets orbiting the star, and the least massive (with a minimum mass twice that of the Earth). Thus far it has been the Doppler method, measuring wavelength shift in the star’s spectral lines, that has identified the four uncontroversial planets: GJ 581 b, c, d and e.
I use the term ‘uncontroversial’ because of the ongoing debate over two other possibilities, not yet confirmed, one of which (GJ 581 g) was thought to be in the star’s habitable zone and announced as such to widespread media attention. The issue remains in doubt but I’m hearing little support for the two latter planets. Nonetheless, the GJ 581 system has stayed in the news because of habitable zone questions, the latest involving GJ 581 d, first thought to be outside the habitable zone and now found to have a chance for liquid water at the surface, assuming a carbon dioxide atmosphere in the right configuration. While all these matters continue to be studied, we now have the MOST findings, which say that if GJ 581 e transits the star, it must have a radius smaller than 1.4 times that of Earth or MOST would have detected it.
Transit or not? If the latter, we at least put some constraints on its orbital inclination. If the former, we know that it’s likely a solid rocky planet, one that, the researchers suggest, would lack a hydrogen or helium atmosphere. Diana Dragomir (University of British Columbia) led the study:
“Although transits were not detected for Gliese 581e, this result allows us to place limits on the planet’s physical and orbital properties, in addition to letting other astronomers know whether they should keep searching.”
So we keep homing in on the possibilities in this interesting system, which particularly flags the attention because it is relatively close to our Sun at some 20 light years. Also useful to learn is that MOST is showing a low level of activity on the host star. Remember that M-dwarfs have turbulent youths, spitting solar flares that could be problematic for the formation of life. The stability of GJ 581 argues that it is an older M-dwarf, and thus one that would have had time for life to emerge, assuming there is a planet on which the conditions really are favorable.
More on Blue Stragglers
We recently talked about ‘blue straggler’ stars, bluer and more luminous than would be expected by looking at the stars in the cluster around them. All of this assumes that the clusters we’ve found blue stragglers in contain stars that formed at the same time, from a single cloud of gas, with no new stars being formed since. I was interested to see that researchers at McMaster University have presented their own work on blue stragglers at the same Canadian Astronomical Society meeting. The work underscores the current explanations for stars that seem hotter, brighter and more massive than they ought to be given their cluster’s age. The thinking has an inescapable logic — clusters contain lots of stars in close quarters. Collisions and close passes are inevitable.
Alison Sills explains:
“Astronomers expect that the stars get too close to each other because of the complicated dance that stars perform in these dense clusters, where thousands of stars are packed into a relatively small space, and each star is moving through this cluster under the influence of the gravity of all the other stars. Somewhat like a traffic system with no stop lights, there are a lot of close encounters and collisions.”
Stellar interactions, then, may be producing blue stragglers that mimic the appearance of younger stars. But Sills’ work draws on Hubble Space Telescope observations of globular clusters that suggest two generations of star formation are involved rather than one, with a second generation evidently forming from material that was gently shed by the first generation, instead of, as is common in the rest of the galaxy, drawing on the remains of exploded stars. Sills is finding that this second generation of stars shows some of the same properties as the blue stragglers, including their color and their location in the cluster. So is the answer that stellar collisions and close passes produce not just blue stragglers but a related kind of star?
Some of the challenges this work will face involve understanding what happens when binary stars merge, and whether or not the model fits what we now know of blue stragglers, not to mention firming up our knowledge of whether stars in globular clusters do form in more than one burst. These stars are curiosities indeed and we’ll keep an eye on Sills’ work. I mentioned earlier in the week Martin Beech’s suggestion that blue stragglers be examined as possible instances of stellar engineering. Nothing observed thus far suggests anything other than a natural phenomenon. It’s interesting to speculate on what kind of stellar discovery really would point to a tangibly technological source, a question for the new generation of SETI specialists to ponder.
Starship Fuel from the Outer System
Adrian Mann has done it again, as witness his illustration of a gas mining operation on Uranus, reproduced below. The idea, as explored by Adam Crowl on Discovery News this morning, is to acquire vast amounts of helium-3 to supply not only Earth’s energy needs but the fusion engines of the Project Icarus star probe. I love Adrian’s work and particularly his Project Daedalus images, on display along with much of his other work in his online gallery. What he manages to do is to take an engineering concept and translate it into images that are both accurate yet stunning. It’s easy to forget, until he reminds us, that hard-nosed equations and their resulting designs can lead to extraordinary vistas, a result that reawakens the sense of wonder.
Image: Balloons, like those shown here in the atmosphere of Uranus, could be used to harvest helium-3 as starship fuel for Project Icarus. Credit: Adrian Mann.
Adam Crowl is a frequent Centauri Dreams contributor, but he’s also deep in the Project Icarus effort, serving as its module lead for fuel and fuel acquisition. And fuel is the heart of the problem. Deuterium (hydrogen with an added neutron) and the isotope of helium known as helium-3 (containing one less neutron than helium-4, or regular helium) create the kind of reaction Icarus needs. The method is preferable to the fusion of deuterium with tritium because the latter releases about 80 percent of the fusion energy in the form of high-energy neutrons. To avoid that kind of heat transfer to the engine, the original Project Daedalus team focused on deuterium/helium-3, which continues to be the method of choice for the Icarus designers.
But where to get the helium-3, which is found only in tiny amounts on our own planet? You might think the Moon would be useful, given that the solar wind has deposited perhaps as much as 2.5 million tons of the stuff in the lunar regolith. But Icarus has had a long look at lunar mining, and finds that the energy needed to extract it would be greater than what it would eventually produce. That leads us back to the gas giants — Project Daedalus focused on Jupiter for helium-3 extraction, conceiving of a giant mining operation using floating factories in the atmosphere.
But Uranus may be the better choice, and that leads to quite an interesting infrastructure. Here’s Adam’s take on the advantages of Uranus, and the technology needed to exploit them:
…as a mining site it has several advantages. The surface gravity, which is defined from the 1 bar pressure level in a gas giant’s atmosphere, is 90 percent that of Earth’s and the speed needed to reach low orbit is lowest of all the gas planets. Uranus’s rings are also high, thin and not showering the atmosphere below with a hail of meteors, unlike Saturn’s.
Accessing the gas riches of Uranus will require nuclear power, however. Designs exist for nuclear powered ramjets that could fly indefinitely in the atmospheres of the gas giants — this might prove a viable means of keeping an extraction factory aloft. Else we’ll be back to using balloons like “Project Daedalus,” serviced by nuclear ramjets.
An atmosphere composed of a cold gas mix that is lighter than helium and not much heavier than hydrogen, means that hot-air ballooning will need to be used. That the oldest technology of flight will find a role supporting the latest, fusion propulsion, has a certain poetic justice.
Getting the fuel home, where it can be used domestically as well as for tanking-up starships, could provide an early pay-off for developing a fusion propelled starship.
That payoff could involve a major change to how our planet gets its energy. Adam looks at world energy demands, which have increased historically at a rate of 2.5 percent per year. By 2100, which for the purposes of argument is chosen as the earliest date for the launch of a star probe like Icarus, 14,000 tons of deuterium/helium-3 fuel would supply world energy demand for a year. The same infrastructure that would return helium-3 from Uranus (conceived as a high-speed freighter built on fusion principles) would offer a continuing source of fuel on our own planet. Making such a case will be a key issue for the Icarus team, because finding the commercial incentive to develop Uranian gas mining is the only way to conceive of it happening.
Are there other options? Sure, and Project Icarus is examining them. If pure deuterium fusion can be put to work — this assumes finding ways to confine the excess neutrons in the plasma created by the reaction and holding down damage to the reactor walls — then we can look much closer to home for deuterium. Now we have a further incentive for a return to the Moon:
Unlike helium-3 we know the moon has large amounts of hydrogen, as ice, and a significant fraction of it will be deuterium. The moon’s low gravity also means that water composed of regular hydrogen and oxygen will escape quicker than heavy water, perhaps leading to a concentration of deuterium in the water of the moon. We won’t know until we return to the moon for a closer look.
We can also look at the fusion of boron-11 and hydrogen, a reaction that is hard to sustain and perhaps impossible to adapt for propulsion purposes. But so far the odds continue to favor deuterium/helium-3, which leads us invariably to the outer Solar System. Taking a long-term look at our possible future, the creation of an infrastructure that can mine the atmosphere of a gas giant would have to make financial sense in terms of energy production at home while serving as a testbed for the technologies that would push much deeper into space. The Daedalus designers glimpsed that infrastructure thirty years ago. We now re-examine their thinking to tune up the concept and bring it into line with the latest in fusion research.
Simulating Moons Around Terrestrial Planets
Just how the Moon originally formed is under renewed scrutiny given the finding that it contains larger amounts of water than previously thought. We’ll look at that issue in depth another time, because it’s far from resolved. The generally accepted account of the Moon’s formation involves a giant impact with a planetary embryo that has been called Theia. The name is a nod to the Greek story of the titan that gave birth to Selene, the Moon goddess. After its formation, the Moon would have been closer to a much more quickly rotating Earth, inducing huge tidal forces that may have had repercussions on the evolution of the earliest life on the planet.
All of this has a further bearing on life’s emergence because a large moon can affect the tilt of a planet’s rotation relative to its orbit around the star. The term for this degree of tilt is ‘obliquity,’ and its effects on global climate can be profound. If there is little or no tilt, the poles become colder and heat flows in their direction. Increasing the obliquity means that the poles get more sunlight during half of the year while the equatorial regions cool twice a year. The influence on climate is inescapable, as is the fact that obliquity will be unique for each planetary situation.
A new paper by Sebastian Elser (University of Zurich) looks at this issue in terms of the Earth’s history and the probability of giant impacts among planets in general. What we know now is that the Earth’s tilt varies about 1.3 degrees around the figure of 23.3 degrees, with a period of roughly 41,000 years. Elser and team note that without the Moon, the Earth’s obliquity would experience large variations. Venus, which has no moon, shows a retrograde spin, which the Elser paper finds may have been induced by spin-orbit resonances and tidal effects.
Obliquity can vary enormously with time. The tilt of Mars’ rotation ranges from 0 to 60 degrees in less than 50 million years, and earlier work has indicated that the obliquity of an Earth without its Moon would range from 0 to as much as 85 degrees (complete references on these numbers can be found in the paper, cited below). Large moons, then, may be a major player in keeping climatic conditions stable. The Elser paper explores the impact history of planets to see how many would be likely to have a companion like the Moon, using simulations of planets forming in the habitable zone. The history and evolution of such Moons is then modeled.
The results show that large moons are not unlikely:
Under these restrictive conditions we identify 88 moon forming events in 64 simulations… On average, every simulation gives three terrestrial planets with different masses and orbital characteristics and we have roughly 180 planets in total. Hence, almost one in two planets has an obliquity stabilizing satellite in its orbit. If we focus on Earth-Moon like systems, where we have a massive planet with a final mass larger than half of an Earth mass and a satellite larger than half a Lunar mass, we identify 15 moon forming collisions. Therefore, 1 in 12 terrestrial planets is hosting a massive moon.
Assuming, then, that an Earth-class planet forms in the habitable zone around another star, the chances of its being orbited by a moon large enough to stabilize its orbital tilt is roughly 10 percent. The simulations used here, based on 2010 work by Ryuji Morishima (Swiss Federal Institute of Technology) and colleagues, produce numerous habitable ‘Earths,’ so the question of the importance of the Moon’s stabilizing influence becomes significant. We also have to untangle the issue of the water content of lunar magma, called into play by new work by Erik Hauri (Carnegie Institution of Washington). We’re looking at water levels 100 times higher than first supposed, challenging the giant impact theory of the Moon’s formation, which predicted very low lunar water content. Clearly, untangling all this will involve, among other things, sample returns from planets and other bodies that will teach us more about our system’s history.
Hauri speaks to this question himself:
“Water plays a critical role in determining the tectonic behavior of planetary surfaces, the melting point of planetary interiors and the location and eruptive style of planetary volcanoes. I can conceive of no sample type that would be more important to return to Earth than these volcanic glass samples ejected by explosive volcanism, which have been mapped not only on the Moon but throughout the inner solar system.”
The paper on planet/moon simulations is Elser et al., “How common are Earth-Moon planetary systems?” accepted for publication in Icarus (preprint). On the issue of water on the Moon, see Hauri et al., “High Pre-Eruptive Water Contents Preserved in Lunar Melt Inclusions,” published online by Science on 26 May 2011 (abstract). On the Moon’s stabilizing effects in general, see Laskar et al., “Stabilization of the Earth’s Obliquity by the Moon,” Nature 361, 615-617 (1993). Abstract available.
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