SunVoyager

by Kelvin F Long

Recently I have been looking at deep space probes driven by inertial confinement fusion propulsion. The SunVoyager is a mission concept for a 500 - 1000 AU flight carrying a 100 tons payload. In the current configuration it would complete the mission in a trip time of order 6 - 10 years travelling at speeds of 720 km/s. It would use a 5.76 milli-gram pellet filled with D3He fuel detonated at 10 Hz pulse frequency augmented with expellant propellant for enhanced mass flow rate. The laser driver would be 43.5 MJ delivered to the target with an assumed efficiency of 24.3% which implies a wall plug equivalent energy of 179 MJ. This is using a laser with an effective intensity of 4e17 W/cm2 and 60 separate beamlines. ICF propulsion is difficult. It was designed using a code I have been constructing in Fortran 95 called HeliosX. For information see the first concept paper published in the Journal of Spacecraft & Rockets and a follow-up paper which will shortly be submitted:

• Development of the HeliosX Mission Analysis Code for Advanced ICF Space Propulsion, Acta Astronautica, 202, 157-173, 2023.

• SunVoyager: Interstellar Precursor Probe Mission Concept Driven by Inertial Confinement Fusion Propulsion, Journal of Spacecraft & Rockets, 60(3), May-June 2023.

• SunVoyager Revisited: Interstellar Precursor Probe Driven by Inertial Confinement Fusion Propulsion, Submission Pending, March 2024.

Brief History of Interstellar Studies

In this article we give a brief overview of the history of interstellar studies. The entire field would encompass perhaps 10,000 papers and so inevitably this overview is not complete. Instead, this is intended to give just a flavour for some of the progress in the field and the directions it has taken in considering travelling to other star systems.

In 1952 the British scientist Les Shepherd published a paper in the Journal of the British Interplanetary Society titled Interstellar Flight [1], in which the author first described the essential requirements for an interstellar mission as implied by basic rocketry principles. The author also covered area such as erosion of the spacecraft due to particle bombardment due to interactions in the interstellar medium.

In 1960 the american physicist Robert Bussard made an amazing proposal which appeared to present a clear method of travelling between the stars. His paper Galactic Matter and Interstellar Flight [2] suggested that a spacecraft could get away from having to carry enormous amount of propellant fuel by instead mining the fuel en-route. In particular this was the hydrogen fuel of the interstellar medium. In principle such a vehicle would be capable of reaching relativistic speeds. Subsequent research however pointed out some of the technical issues with trying to make an interstellar ramjet work, such as the low abundance of hydrogen in the interstellar medium, the small cross section of hydrogen to fusion capsule, the overheating of the protons within the large magnetic funnel. It was clear therefore that if any version of the ramjet was possible, it would involve moderating those protons to managable energies.

In the early 1980s the american physicist Robert Forward pursued the idea of propellantless propulsion, such as in his paper Rountrip Interstellar Travel Using Laser-Pushed Lightsails [3]. His interest focussed on the idea of using directed energy beaming, such as with microwave beams or optical lasers, to push a small sail craft to the stars at large speeds. This culminated in his Starwisp concept in his paper Starwisp: An Ultra-Light Interstellar Probe [4]. On paper the energy beaming concepts proposed by Forward looked highly credible, but they came with the disadvantage of requiring large amounts of power, typically in the 10s TW levels. Forward was very optimistic about the potential of his ideas and even presented his concepts as a potential roadmap program to the US Congress. This was captured in his earlier paper A Programme for Interstellar Exploration [5], in which he believed it was possible to launch such missions by the year 2000. Forward remained an advocate for interstellar studies for many years, and he also initiated a form an index for Interstellar Travel and Communications: A Biography [6].

As well as the progress in thinking about propulsion, other work also focussed on the possibility of finding extra-terrestrial life assuming starships could be constructed by us or others that could eventually travel around the galaxy. The american astronomer Carl Sagan wrote about this in Direct Contact Among Galactic Civilizations by Relativistic Interstellar Spaceflight [7] as well as Galactic Civilizations: Population Dynamics and Interstellar Diffusion [8]. In this work Sagan proposed it was possible travelling at relativistic speeds to reach the centre of the galaxy in only 28 years and the edge of the Andromeda galaxy within 32 years and the centre of the known universe within 48 years. He also wrote about the possibility of trying to detect other intelligent life in the galaxy, such as in On the Detectivity of Advanced Galactic Civilizations [9].

In the 1950s and 1960s , former members of the Manhattan project to build an atomic bomb, came together to consider whether such technology could be utilised for the application of space propulsion. This was conducted under a General Atomics / United States Air Force study called Project Orion. This was based on an original proposal from Ulam and Everett in their work On A Method of Propulsion of Projectiles by Means of External Nuclear Explosions [10]. The work suggested that using atomic bombs or hydrogen bombs it may be possible to achieve speeds of 5% and 10% of the speed of light respectively. The British born physicist Freeman Dyson wrote about the project in Death of a Project [11] and Interstellar Transport [12]. An excellent history of Project Orion was written up in Project Orion: The Atomic Spaceship 1957 - 1965 [13]. An excellent review of nuclear pulse propulsion was written by the British scientist Anthony Martin in Nuclear Pulse Propulsion: A Historical Review of an Advanced Propulsion Concept [14].

Despite the large growth in research into the question of intelligent life in the galaxy, the consensus view was that we didn’t see any. This bought about the possibility that interstellar travel was not possible. To address this, the British scientist Anthony Martin and engineer Alan Bond initiated a study of the British Interplanetary Society called Project Daedalus. They assembled a team and over 5 years designed a two-stage fusion based concept that would reach 12% of light speed and be sent as a 450 tons robotic flyby probe to the Barnard’s star system 5.9 light years distance. The spacecraft would carry 50,000 tons of D-He3 fuel and it utilised an inertial confinement fusion concept as its ignition system, based on a paper the team had read published by the German born physicist Freidwardt Winterberg titled Rocket Propulsion by Thermonuclear Microbombs Ignited with Intense Relativistic Electron Beams [15]. The study was highly rigorous in that it encompassed all of the essential systems of starship design, including propulsion, power, structure, materials, navigation, mission analysis, reliability, particle bombardment and more. It remains the most comprehensive starship design concept in history. The results of the study were eventually published as Project Daedalus: The Final Report on the BIS Starship Study [16].

The same authors that had initiated the Project Daedalus study had also initiated a study of a world ship. This is an enormous vessel that can carry large populations of people and typically travels at a speed of 1-3% of the speed of light. The results of this work was published in World Ships - An Assessment of the Engineering Feasibility [17] and World Ships - Concept, cause, Cost, Construction and Colonisation [18]. These concepts were nuclear pulse propulsion based. To provide a counter perspective, the american physicist Gregory Matloff wrote about world ships that did not utilise nuclear power and propulsion. In particular in his work titled Interstellar Solar Sailing: Considerations of Real and Projected Sail Materials [19] had already advocated for the use of solar sail systems in the transport of spacecraft around the Solar System, and so applying them to interstellar spacecraft was an extension of this work, which he did in Faster Non-Nuclear World Ships [20]. Matloff also wrote several books, including the outstanding Starflight Handbook [21].

In the modern era there has been a revival of the subject of interstellar studies. One of the causes of this has been the discovery of extra-solar planets around other stars, which now number thousands. In the 1990s the american space agency NASA began looking at methodologies in Breakthrough propulsion, such as work by the american scientist Marc Millis in Challenge to Create the Space Drive [22] and Breakthrough Propulsion Physics Workshop Preliminary Results [23]. A lot of these ideas were later published in the excellent book Frontiers of Propulsion Science [24].

Research that started to gather greater interest in breakthrough ideas included extensive theoretical work on wormhole theories by people such as the american physicist Kip Thorne in his work Wormholes in Spacetime and their Use for Interstellar Travel: A Tool for Teaching General Relativity [25]. In addition, a post-graduate student then at Cardiff University, Miguel Alcubierre wrote a paper titled The Warp Drive: Hyper-Fast Travel within General Relativity [26] in which he demonstrated theoretically how it may be possible to one day move space and so move around the Cosmos in the manner described by the science fiction show Star Trek.

The Project Daedalus study has received a revival known as Project Icarus, and a study was initiated in 2009 as written in the paper Project Icarus: Son of Daedalus - Flying Closer to Another Star [27]. The study was initiated by the British physicist Kelvin Long who also went on to write a book about interstellar space propulsion titled Deep Space Propulsion, A Roadmap to Interstellar Flight [28]. The Project Icarus study is different from the original Project Daedalus study, in that it aims to demonstrate theoretically full orbital insertion into the target stellar system, as opposed to Daedalus which was a flyby probe only. The study has resulted in many concept designs, with the most advanced being the Firefly concept, as published in Plasma Dynamics in Firefly’s Z-Pinch Fusion Engine [29].

Many of the papers in this field have been published in the Journal of the British Interplanetary Society, with its red covered interstellar issues published between 1974 - 1991 and revised recently. The British Interplanetary Society was set up in 1933 and is one of the world’s oldest space societies. It has been the torch bearer of the interstellar vision since its founding, and in particular since that first Les Shepherd paper in 1952.

Today there are many organisations pursuing the interstellar vision. This includes the Tau Zero Foundation, the Tennessee Valley Interstellar Workshop, Icarus Interstellar and the Initiative for Interstellar Studies (also known as the Institute for Interstellar Studies in the United States). The most recent inclusion to this list is the Breakthrough Initiatives, an organisation that has been funded in the millions of dollars and is directly pursuing both the detection of intelligent life in the Universe, but also under its Project Starshot it is pursuing the design and launch of an interstellar probe within two decades. This initiative was instigated by the american physicist Philip Lubin in his paper A Roadmap to Interstellar Flight [30] and is an effort to send something that is Gram-scale in mass by the use of directed energy laser beam propulsion.

In addition to all of the technical publications, a parallel stream of thought that has helped to move the field forward has been the science fiction literature. In particular, authors such as Robert Heinlein in his Time for the Stars [31] which explored torch ship propulsion and relativistic flight; Poul Anderson in his Tau Zero [32] which explored interstellar ramjets; Arthur C Clake in his The Songs of Distant Earth [33] which explored quantum vacuum propulsion; or Clarke again his now famous 2001 A Space Odyssey [34] which explored von neumann probes and extraterrestrial intelligence in the Universe. The book was made into a film of the same name, directed by Stanley Kubrick; Robert Forward in his The Flight of the Dragonfly [35] which explored laser sail propulsion; Larry Niven and Jerry Pournelle in The Mote in God’s Eye [36] which explored laser sail propulsion but also the first contact with an alien civilisation. These are just a small example of the vast literature on this subject.

This brief history of interstellar studies has barely scratched the surface on what has been achieved. It is not possible in these pages to list everything, but suffice it to say good progress has been made theoretically and now the effort needs to move towards experimental demonstrations and actual in-flight experience. The Foundations of Interstellar Studies workshops are designed to help move us along this trajectory with a focus on problem solving and solutions.

References

[1] L. R. Shepherd, Interstellar Flight, JBIS, 11, 4, July 1952.

[2] R. W. Bussard, Galactic Matter and Interstellar Flight, Astronautica Acta, 6, Fasc.4, 1960.

[3] R. L. Forward, Roundtrip Interstellar Travel Using Laser-Pushed Lightsails, J.Spacecraft & Rockets, 21, March-April 1984, pp.187-195.

[4] R. L. Forward, Starwisp: An Ultra-Light Interstellar Probe, J.Spacecraft, 22, 3, May-June 1985.

[5] R. L. Forward, A Programme for Interstellar Exploration, JBIS, 29, pp.610-632, 1976.

[6] E. F. Mallove, R. L. Forward et al., Interstellar Travel and Communication: A Bibliography, JBIS, 33, pp.201-248, June 1980.

[7] C. Sagan, Direct Contact Among Galactic Civilizations by Relativistic Interstellar Spaceflight, Planet. Space Sci, pp.485-498, 11, 1963.

[8] W. I. Newman & C. Sagan, Galactic Civilizations: Population Dynamics and Interstellar Diffusion, Icarus, 46, pp.293-327, 1981.

[9] C. Sagan, On the Detectivity of Advanced Galactic Civilizations, Icarus, 19, pp.350-352, 1973.

[10] C. J. Everett & S. M. Ulam, On a Method of Propulsion of Projectiles By Means of External Nuclear Explosions Part 1, LANL, August 1955.

[11] F. Dyson, Death of a Project, Science, 149, 3680, pp.141-149, 9 July 1965.

[12] F. Dyson, Interstellar Transport, Physics Today, 21, 10, pp.41-45, October 1968.

[13] G. Dyson, Project Orion: The Atomic Spaceship 1957 - 1965, Allen Lane The Penguin Press, 2002.

[14] A. R. Martin & A. Bond, Nuclear Pulse Propulsion: A Historical Review of an Advanced Propulsion Concept, JBIS, 32, 8, pp.283-310, August 1979.

[15] F. Winterberg, Rocket Propulsion by Thermonuclear Microbombs Ignited with Intense Relativistic Electron Beams, Raumfahrtforschung, 15, pp.208-217, 1971.

[16] A. R. Martin, A. Bond, Project Daedalus - The Final Report on the BIS Starship Study, JBIS Supplement, 1978.

[17] A. Bond, A. R. Martin, World Ships - An Assessment of the Engineering Feasibility, JBIS, 37, pp.254-266, June 1984.

[18] A. R. Martin, World Ships - Concept, Cause, Cost, Construction and Colonisation, JBIS, 37, pp.243-253, June 1984.

[19] G. L. Matloff, Interstellar Solar Sailing: Considerations of Real and Projected Sail Materials, JBIS, 37, 3, pp.135-141, March 1984.

[20] G. L. Matloff, Faster Non-Nuclear World Ships, JBIS, 39, 11, pp.475-485, November 1986.

[21] E. Mallove and G. Matloff, The Starflight Handbook: A Pioneer’s Guide to Interstellar Travel, John Wiley & Sons, 1989.

[22] M. G. Millis, Challenge to Create the Space Drive, Journal of Propulsion and Power, 13, 5, pp.577-582, Sept/Oct 1997.

[23] M. G. Millis, Breakthrough Propulsion Physics Workshop Preliminary Results, NASA/TM-97-206241, November

[24] M. G. Millis and E. W. Davis, Frontiers of Propulsion Science, Progress in Astronautics and Aeronautics, 227, The American Institute of Aeronautics & Astronautics, 2009.

[25] M. S. Morris and K. S. Thorne, Wormholes in Spacetime and their Use for Interstellar Travel: A Tool for Teaching General Relativity, Am. J. Phys, 56, 5, May 1988.

[26] M. Alcubierre, The Warp Drive: Hyper-Fast Travel Within General Relativity, Class. Quantum Grav, 11-5, L73-L77, 1994.

[27] K. F. Long, M. Fogg, R. Obousy, A. Tziolas, A. Mann, R. Osborne, A. Presby, Project Icarus: Son of Daedalus - Flying Closer to Another Star, JBIS, 62, 11/12, pp.403-414, Nov/Dec 2009.

[28] K. F. Long, Deep Space Propulsion: A Roadmap to Interstellar Flight, Springer, 2011.

[29] R. M. Freeland, Plasma Dynamics in Firefly’s Z-pinch Fusion Engine, JBIS, 71, pp.288-293, 2018.

[30] P. Lubin, A Roadmap to Interstellar Flight, JBIS, 69, pp.40-72, 2016.

[31] R. Heinlein, Time for the Stars, Gollancz, 1963.

[32] P. Anderson, Tau Zero, Doubleday, 1970.

[33] A. C. Clarke, The Songs of Distant Earth, Del Rey Books, 1986.

[34] A. C. Clarke, 2001 A Space Odyssey, Del Rey Books, 1968.

[35] R. L. Forward, The Flight of the Dragonfly, Pocket Books, 1984

[36] L. Niven & J. Pournelle, The Mote in God’s Eye, Simon & Schuster, 1974.

Interplanetary Podcast

The Director of the Interstellar Research Centre Kelvin F Long recently appeared on the Interplanetary Podcast. Listen to the full show here published on 17th April 2020. The topic of conversation was all things interstellar travel.

https://soundcloud.com/matt-interplanetary/181-kelvin-long-interstellar

The Interstellar Studies Bibliography

We have recently started work on an interstellar bibliography. This is a collection of papers on the subject of interstellar fight, interstellar travel or otherwise known as interstellar studies. Hence it is called the Interstellar Studies Bibliography or ISB. This name comes from the famous red cover issues of the Journal of the British Interplanetary Society which were published between 1974 and 1991.

In the past others have attempted to create such a bibliography and this was done by Robert Forward and Eugene Mallove in addition to others. It was known as “Interstellar Travel and Communicaiton: A Bibliography”. Their work was very comprehensive and in June 1980 had recorded a total of 2699 references to articles, books and reports discusing the problems of interstellar travel and communication.

They also went to the next level and sub-divided the bibliography into subjects, which included:

1. General discussions of interstellar transport.

2. Proposed methods of interstellar transport.

3. Relativistic effects.

4. Interstellar vehicle issues.

5. Life-supporting extrasolar environments.

6. origin of extrasolar life.

7. communicating with extrasolar intelligence.

8. Radio search for extra-terrestrial intelligence (SETI)

9. Non-technological discussions of interstellar travel.

10. Multiple topic books.

11. Compendia.

12. Bibliographies.

13. Miscellaneous.

They then further divided each of the subjects into sub-categories, but we won’t list those here. We are not yet sure as to what level we will go with the ISB but for now our task is to collate the references and then when we have assembled them, assess how to further improve it. This is obviously a large challenge and some of the subjects included in the original bibliography may be excluded from the present one (e.g. exosolar planet issues) simply due to the vast number of papers and articles that exist on the subject.

For now we are listing published books, journal papers, conference proceeding papers, white papers, team reports, graduate thesis, popular magazine articles, science fiction novels and a list of contributory authors. In addition, we supply some visual graphics of the covers of some of the seminal publications, and these are important because they help to depict some of the fantastic visual imagery.

We will continue to build in new content in the weeks and months ahead and we already have other pages ready to go live, such as a list of films, community meetings/events and a list of organisations that have played some role in this field. You will also notice that many of the pages are accompanied by a chart of data which shows the trend in the number of publications over time and perhaps nicely illustrates when the community has been active or not so active. We are currently analysing this data and will shortly be publishing a review of it, as an indication of interstellar research eras.

To find out more about the Interstellar Studies Bibliography, simply visit the pages on this web site which are continually updated and under construction:

The Interstellar Studies Bibliography

The City & The Stars

In the story ‘The City & the Stars’ the writer Arthur C Clarke proposes a definition of the ideal machine: that “no machine may contain any moving parts”. The central character - Alvin - is different from his contemporaries because this is his first life and in some ways he is responsible for the renewal of human civilisation to come. But Alvin has a passion, to get outside of the city
and explore, an almost infectious obsession that drives his every action. Eventually, he is helped by what can only be described as a deliberate and mischievous anomaly in the computer program (called Khedron) that shows him the way. There is a fundamental paradox in the story. The city of Diaspar is a perfect place, but the world outside is not. After a long period of galactic war the city of Diaspar is the last resting place of humanity, protected from any would-be invaders by a large domed shield.

Humanity was once a star-fairing species but has been forced to adopt an insular existence. Diaspra is also a form of dystopia, offering its inhabitants all they could ever want including immortality, but inhibiting their freedom to explore the world outside.

Outside the city is the human settlement of Lys, an apparently technologically less advanced place with no interest in space travel, consisting of mortal people who have perfected mental telepathy. In Lys, Alvin meets a companion called Hilvar and together they explore the planet. Eventually they meet an ancient extraterrestrial creature and his fellow robot that were loyal to their masters
- 'The Great Ones'. Their journey leads them to the discovery of a spaceship and they are able to leave Earth and travel to meet a powerful but child-like being of pure intellect called Vanamonde, who can travel through space instantaneously. They establish a telepathic communication with the being. From this encounter they learn the truth of what happened to the rest of the human race and the terrible deeds of the insane being known as 'The Mad Mind', a form of mentality which had been imprisoned inside a black star.

Like much of Clarke’s writing, this story contains a powerful blend of credible science fiction and large ideas which border on the metaphysical. Clarke maintains a perfect balance between these two limits and demonstrates, as he does with many of his other books that he is a corking good writer, as C. S. Lewis once described him. The ‘City & the Stars’ is one of my favourite science fiction novels by Clarke. I left the book wanting to know more, about where Alvin travelled to next.

Like much of science fiction literature, there are stories which contain real parables about our actual society and in particular the two characters Alvin and Khedron are interesting. Alvin is the adventurous one, always wanted to explore what is around that next corner, over that next hill, or to climb that highest mountain. He represents the curiosity in the human species that has helped us
to migrate across the vast lands of Africa, into Europe and Asia and beyond. They don't need to have reason for their adventures, but are just inspired by the call to adventure. Khedron is the mischievous one, the person that likes to play. He represents the contrarians and the mavericks and the awkward people in our societies that just won't play ball with the normal rules. Any attempt to contain them just makes them worse.

An example of a scientist that stood out like Alvin was the American physicist Richard Feynman, who just loved to play with science for the pleasure of finding things out. He had an infectious curiosity that also made him a great scientist. An example of a scientist that was like Khedron who would act as a contrarian to the established view was the British born physicist Freeman Dyson; a man who expressed many controversial views, but also come up with many creative ideas. Another is the British scientist and environmentalist James Lovelock, celebrated for his ‘Gaia’ theory of Earth as a self-regulating system, but demonised by many in the environmental movement for his views on nuclear energy. No person is perfect, but these particular attributes of their characters have more value to society than any flaws in their personalities pointed out by others.

As we seek to develop human society towards a more perfect model, for sure we need a sense of conservatism in our actions to ensure that our civilisation is stable and able to function. But it is the characters of Alvin and Khedron that takes us to the next level. It is a bit like the ancient Chinese philosophy of yin and yang in that a stable system needs the seeds of creativity to ensure it does not stagnate, and an unstable system needs the seeds of order to ensure it does not develop into full blown anarchy. Yet, our educational systems have been developed to reward the conformist and by definition to punish those that do not. What we see as bad behaviour, may actually be a necessary component of our society playing out in that they too have a role to play in ensuring that our societies continue to evolve towards new horizons.

A key factor which protects the contrarians and the mavericks among us is the ability to conduct free speech, but this is something that has come under considerable threat even in the Western World in recent years. In particular, scientists are no longer free to express their opinions without consequences and there is always a political angle to consider in their deliberations. If they say
something that goes against the majority they may face being ostracised, banishment or the ending of their career. This is amazing considering the inquisition experience that Galileo Galilei went through at the hands of the Catholic Church in the 1600s when he pushed the view that the Earth rotated around the Sun; we appear to have learned nothing. Whilst it is true that those mavericks may express opinions which can cause offence, it is better to have an open society where such views are publicly debated. The preservation of free speech at the risk of offence has a far greater benefit to contemporaneous society than does the policy of shutting that free opinion down. Science is really the pursuit of knowledge and higher truths, and our capacity to attain that knowledge is only facilitated by the maintenance of scientific objectivity in our various societal discussions.

In the construction of a starship society what sort of a culture do we want to develop? We certainly don't want authoritarianism but neither do we want anarchy, yet some degree of both order and chaos seems essential to our progress. We have over the centuries experimented with many governance models within the different nation states of Earth, but none of them have been shown to
be perfect. The only way we will tend towards a more perfect model is to continue the tradition of free speech and allow models to play out. This would appear to be an essential social-experiment before we can put people onto a starship and have confidence that it would make the journey.

Story telling has more to tell us than just entertainment. They play out scenarios about our own civilisation and where we are going which can teach us so much about ourselves. Clarke's ‘The City & the Stars’ was a wonderful book like so many of his other books and those of other science fiction
authors. Yet, in thinking about building a city in the stars, it would seem apparent that we firstly need to figure out how to properly build our own cities on Earth. This is not to say that we must perfect those Earth based cities before we can make the attempt at an interstellar journey since often
more is learned about something in the act of making the attempt. But it would seem that by paying more attention to how we govern ourselves and take care of our citizens, this would increase the probability that any future mission into deep space carrying human crews would be successful.

Lecture to the British Interplanetary Society

On Tuesday 25th February Kelvin F Long gave a lecture to the British Interplanetary Society titled “The Philosophy of Starship Physics: The Exploration of Interstellar and Intergalactic Space”. He had been there many times before although not in recent years. Introducing him was past-President Alistair Scott and the current President Gerry Webb was also present during the evening. Despite the BIS computer choosing to shut down early on during the presentation, the talk garnered some interesting discussions post lecture.

Photo credits Geir Engene

During the lecture Kelvin discussed the developments of interstellar studies as a field. This included identifying three critical eras in history, which he termed the foundations age, the golden age and the consolidations age, with key people being involved in those eras as listed below:

1. Foundations Age (1950 - 1973): Les Shepherd, Eugene Sanger, Freeman Dyson, James Strong, Carl Sagan, Robert Bussard, Robert Forward, D. F. Spencer, L. D. Jaffe.

2. Golden Age (1973 - 1991): Freidwardt Winterberg, Anthony Martin, Alan Bond, Robert Parkinson, Robert Freitas, Al Jackson, Gregory Matloff, Giovani Vulpetti, H. D. Froning, T. A. Heppenheimer, E. F. Mallove, C. Powel, D. Viewing, D. Whitmore, C. E. Singer, B. N. Cassenti.

3. Consolidation Age (1991 - 2019): Ian Crawford, Ralph McNutt, Robert Zubrin, Les Johnson, Marc Millis, Geoffrey Landis, Miquel Alcubierre, Johndale Solem, John Anderson, John Halyard, G. Gaidos, Charles Orth, James Benford, Gregory Benford, Terry Kammash, David Fearn, Gerald Nordley, Robert Frisbee, John Cramer, Eric Davis, Jordan Maclay, Philip Lubin.

The years 1974 - 1991 was particularly interesting since this was the special red cover interstellar issues of the Journal of the British Interplanetary Society, but many interstellar papers started appearing the year before that. The year 1992 was also interesting because it was when the first exoplanet was discovered, arguably sparking significant interest in interstellar ideas. Some significant technical projects over these periods included the nuclear bomb propulsion Project Orion (1957 - 1965), the fusion starship Project Daedalus (1973 - 1978), the laser beamed driven Project Starwisp (1984), the fusion starship Project Icarus (2009 - 2020), the laser beam driven Project Starshot (2016 - present).

The full video for the lecture is available on You Tube or via the link below.

Memories of Freeman Dyson

I was very sad to hear of the recent loss of the physicist Freeman Dyson on the 28th February 2020. It just so happens that I last got an email from him on 8th February, only two weeks before he had passed. I did not have an impression that anything was wrong with his health, but I did get an impression he was very busy. My last words to him were “God speed and ad Astra” and little did I know this would be a metaphor for spiriting him away on the next great journey that awaits him in this fantastic Cosmos.  I was not surprised to hear that he had passed away given how old he was, but I was saddened by it since Dyson had shown me tremendous personal support and kindness in the decade or so that I had corresponded with him as a fellow scientist.

As a student I had first come across his writing by reading about the struggles of Richard Feynman in solving the problems of quantum electrodynamics and how it was Dyson’s 1948 paper that had shown some clarity on what Feynman was saying with his unusual diagrams. This, and his work on Project Orion, a nuclear bomb advanced propulsion concept, had made him a legend as one of the smartest people on planet Earth.

I first made contact with Freeman Dyson when I was the Chief Editor of the Journal of the British
Interplanetary Society and I would ask him to review papers. I will never forget the very first review he ever did for me, because it just struck me as the thoughts of an incredibly clear and logical mind that was able to cut through the noise of a scientific paper and get straight to the heart of the argument and dissect it to its fundamental truths. When I interacted with hundreds of other authors and reviewers over the years, nobody else demonstrated an equivalence of thought in quite the same way, and it was an example to me of what the uncluttered mind of a human being was really capable of when high reason and truth is ones goal.

When I was the Vice President of Icarus Interstellar, a United States non-profit I was involved with co-founding, in our bid to win the NASA/DARPA 100 Year Starship competition, Dyson had agreed to support us after I asked him and had approved his name to a signatory of support; among other great science and science fiction people, this letter also included both Patrick Moore and Les Shepherd, who would shortly after pass away. Unfortunately, although we went onto win the 100 Year Starship, others that we teamed with clearly had other plans and so we were unable to execute on our vision.

So it was that in 2012 I moved on from Icarus Interstellar and worked to found the Initiative for Interstellar Studies in the United Kingdom, also called the Institute for Interstellar Studies in the United States. Once again, Freeman Dyson was supportive, and agreed to serve on the advisory committee and did so for the first five years of its operation whilst I was the leading Executive Director.  In his characteristic efficient style his response was to the point “I am willing to serve if needed”. I would correspond with him a few times a year and consult his opinion on various issues. He was also very supportive of the Breakthrough Initiatives Project Starshot effort to send a space probe towards the nearest stars within decades, and served on its advisory committee. This is an effort which I also support serving on the same advisory committee.

Over the years, I had many wonderful conversations with Freeman Dyson. In one such conversation we discussed the accelerated expansion of the universe and the nature of dark energy, and Dyson just went for the jugular and questioned the very meaning of the name “I think the idea is wrong because the name ‘dark energy’ is misleading. The right name for ‘dark energy’ is ‘non-linear expansion’. It describes the shape of the universe, not the existence of a new form of energy”.

In another dialogue we discussed Project Orion. I had read Dyson’s earlier papers when he had been a proponent of the project and then his later reversal. I had spent many years working as a physicist on thermonuclear weapons development and I was attracted to Project Orion as an application of this technology. Yet it seemed to me that although it would not be desirable to launch something like an Orion from the surface of the Earth (due to the risk of atmospheric contamination of radioactive material), given that the space around the gas giant Jupiter was so radiative anyway why couldn’t we launch from there instead? Dyson came back along the lines: “We wouldn’t need to go that far, all we would need to do is launch outside of the Earth’s magnetosphere and that was sufficient”; an indication to me that there were circumstances in which he might support the launch of such an energetic reaction engine. Even the American astronomer Carl Sagan had said he couldn’t think of a better use for such a technology.

We never discussed his well-known criticisms on anthropogenic global warming in any detail, but I was aware of his views and it was such a pity that his unbiased intellect was not listened to merely because his views were contrary to the consensus. He was never carrying some political perspective here and only giving his well-qualified views as an objective physicist. Ultimately, I believe a failure to listen to his opinion will harm the environmental movement in the long-run and this is tragic. Fortunately, those views are online for others to read and watch.

In 2011 I had organised a symposium in London on the Philosophy of Olaf Stapledon, the British philosopher turned science fiction writer. Having read all of the writing of Arthur C Clarke I had then turned to those that influenced him, and this included Stapledon’s 1930 ‘Last and First Men’ and his astonishing 1937 novel ‘Star Maker’. Dyson admitted himself that Stapledon is the one that really originated the idea of a star surrounded by a large artificial sphere able to capture all of its radiative energy – and he expressed a personal wish that at the very least they should be known as Stapledon-Dyson spheres, rather than just Dyson spheres; always wanting to make sure proper credit was given. This was a man of integrity.

In my own paper, later published in 2016 in the journal Axiom and titled ‘Is the Concept of (Stapledon) Universal Mentality Credible?’ I leaned heavily on Dysons viewpoints quoting him in various parts from his wonderful 1979 book ‘Disturbing the Universe’ to illustrate his belief in the potential of a conscious universe: “The laws of subatomic physics cannot even be formulated without some reference to the observer. ‘Chance’ cannot be defined except as a measure of the observer’s ignorance of the future. The laws leave a place for mind in the description of every molecule…..I do not feel like an alien in this universe. The more I examine the universe and study the details of its architecture, the more evidence I find that the universe in some sense must have known that we were coming…..I do not claim that the architecture of the universe proves the existence of God. I claim only that the architecture of the universe is consistent with the hypothesis that mind plays an essential role in its functioning”.

For some time, I was elected onto the governing council of the British Interplanetary Society, and whilst there I was one of the people that put his name forward to become an honorary fellow of the Society. I was very pleased to see that happen eventually in 2017, and his acceptance letter to the BIS is shown below also giving some interesting views on a few topics, writing from the Institute for Advanced Study.

By my count there were only a handful of people that got interstellar studies going in the 1950s and 1960s in what I call the ‘Foundation Age’ leading up to around 1973. In that list I cite Les Shepherd, Eugene Sanger, James Strong, Carl Sagan, Robert Forward, Robert Bussard, D. F. Spencer, L. D. Jaffe and Freeman Dyson. In particular his 1965 Science article on ‘Death of a Project’ and his 1968 Physics Today article on ‘Interstellar Transport’ clearly laid out what was possible with Project Orion type technology. His estimate for when the first interstellar missions could begin using Orion type technology, driven by 2% economic growth was two centuries hence; so around the year 2168. Time will show if his prediction was accurate.

I had an enormous respect for Freeman Dyson and he is one of the few people that I have a photo of in my office, because he was purely inspirational in his conduct, and also in his unwillingness to stroke his own ego; without wanting it or intending it, ironically this made him a leader. Yet, in discussing his leadership of the Space Studies Institute with me as its past president, he was self-critical that he was not the right man for the job in carrying on the legacy from the visionary Gerard O’Neil (I am sure many in the Institute would disagree with him). That self-critical humility, immediately struck me as fresh and unusual from such a high achieving man who was also very kind with the time he gave to others.

He will be sadly missed and it is up to the generations that follow him to continue to demonstrate the example of high reason which he continually showed, something that is particularly needed in these times when reason is often trumped by emotion and social network trolling as people who cannot win an argument through logic resort to underhand tactics and ad hominem attacks; and truth itself is allowed to be a variable rather than a constant that we are all collectively striving to understand.

Freeman Dyson always said he wanted to be a contrarian in debates because it’s the best way to test the logic of the dominant view. He also appeared to enjoy building his own reputation as a heretic. As we seek to solve our problems on Earth and move out into the stars, treasure the few contrarians that still exist, for those are the ones that will prevent us from making our biggest mistakes, and ultimately help us to achieve our biggest goals. This example of his uniquely special character may be the biggest legacy he left us. I for one will miss the conversations I was privileged to enjoy for over ten years with one of the greatest scientists that ever lived and fundamentally a superb human being. It would be fitting if he were reborn as a star.

Kelvin F Long

Project Icarus: Starship Pegasus Makes Progress

Recently several meetings have taken place of some core members of the Project Icarus Study Group. These discussions have included Kelvin F Long (co-founder of the project), Richard Osborne, Michel Lamontagne, Robert Freeland and Rob Swinney (current Project Leader). The team is trying to make progress towards closing out the study, first initiated in September 2009, and so has been going for double the length of the Project Daedalus study. The emphasis on these specific meetings has been on progressing one of the designs towards a greater fidelity of completion.

The design started out as Starship Resolution which had a single engine stage for both the acceleration and deceleration phase and was based on the design of the Daedalus 2nd stage engine. In a need to bring down the 15 year boost time, then then evolved to Starship Endeavour which was a paralised thrust system with a quintec engine arrangement, that is 5-engine bells similar to the Saturn V rocket that took men to the Moon. One of the concerns about this design however has been the high radiation and neutron environment generated from these different engines and how they couple up to each other. This then led to a new 4-engine arrangement which has been named Starship Pegasus. The image below shows the transition from a 5-engine staged Endeavour to a 4-engine staged system and was the baseline for the Pegasus design, although is now undergoing significant revision with the inclusion of radiator fins specifically.

4-engine Staged Endeavour (progenitor to Pegasus) [M. Lamontagne]

Currently, Kelvin F Long has been progressing the design model, built in a Fortran 95 code, and his efforts are now also focussed on the implosion, ignition and burn model for the inertial confinement fusion capsules utilised by the engine. But in addition, Richard Osborne has been working on many of the other systems and the power supply and radiators have been given special attention and he has been working with the others to produce something that is sensible and then folding out a new configuration arrangement for the vehicle layout. Robert and Michel had put a lot of effort into the design of the radiator fins for the Icarus Firefly design [1, 2] and that experience has been well utilised for the Pegasus design. Although preliminary calculations are suggesting that large radiators may not be needed, they are being included as a design margin and to allow for uncertainties. This is in addition to an insulator, to help mop up the x-rays and high energy neutrons. Further, an innovative capsule design is being utilised to help mitigate the offending energy release. Terry Regan has also been attending some of the meetings and lending his wisdom to the design considerations.

Over the last few months several meetings have taken place between these people to include:

• Friday 6th September 2019. Discussion on radiator fins and engine arrangement.

• Friday 11th and Saturday 12th October 2019, special workshop on Project Icarus Concept Design Fusion Ignition Physics and Engineering Propulsion. The main focus was on the implosion and ignition system but with some discussion on radiators, power systems and configuration layout.

• Monday 28th October 2019, discussion on configuration layout.

• Friday 22nd (radiators) and Sunday 24th (power systems) November 2019.

Although Project Icarus has taken a lot of time to complete, the team hopes that the final study report will be published in 2020, and that the additional effort that has gone into the report by certain team members to improve its quality will justify the end product. For those still waiting for the output of this work, watch this space.

References:

1. R. Freeland, Plasma Dynamics in Firefly’s Z-Pinch Fusion Engine, 71, pp.288-293, Journal of the British Interplanetary Society, 2018.

2. M. Lamontagne, Heat Transfer in Fusion Starship Radiation Shielding Systems, 71, pp.450-457, Journal of the British Interplanetary Society, 2018.

Fusion Ignition Physics & Engineering Workshop

On Saturday 12th October 2019 several people met at a special symposium designed to accelerate Project Icarus. It was titled ‘Project Icarus Concept Design Fusion Ignition Physics and Engineering Propulsion Workshop’. Presenting at this meeting was Kelvin F Long, Rob Swinney and Richard Osborne,

This was a workshop focussed on the fusion physics issues relevant to Project Icarus. This is a theoretical design study launched in 2009 to re-design the Project Daedalus spacecraft. The project is nearing completion but there are some issues on closing out the design concept for the Starship Resolution and Starship Endeavour concepts and the purpose of this workshop was to help bring that work to a close so that the project can be published and completed. The focus of this meeting was on the fusion ignition system and also the power, thermal management and fuel storage/acquisition so it was a propulsion specific meting and the team not discus other issues such as communications, science instruments or the payload other than from a top level. Several external people had also been invited to add additional input to the discussions focussed around fusion propulsion designs. The meeting was chaired by Rob Swinney who is the Project Leader for Project Icarus. This was a working level meeting to facilitate discussions on the physics and engineering issues.

Rob Swinney welcomed everyone to the meeting and outlined the purpose for the day. Kelvin F Long presented the Project Daedalus study and some of the physics and engineering issues that had been highlighted by the wider team. Rob Swinney then presented all of the different vehicle concepts that several sub-teams had conceived at a concept level. Richard Osborne presented some of his thinking on the power systems for the Project Icarus vehicle and how they differed from Daedalus. The meeting was then dominated by Kelvin going through his Fortran 95 coding of the different vehicle designs and what work was required to increase its modelling capacity to include the fusion capsule design in particular.

It was agreed that the two main issues that needed to be addressed was the high neutron flux and x-ray radiation environment produced from the energetic capsules. Although it was planned to include an insulation layer in the engine bell and also radiator fins external to the thrust chambers, Kelvin argued that the specific design that he was proposing, based on the principle of shock ignition designs, would actually help to moderate the excess release of offending energies anyway. In particular, the adoption of a thick ablator shell would moderate some of the energy release.

The formal workshop was followed by an extensive discussion between the participants and actual design calculations to make progress and discuss the results. This was then followed by a special virtual meeting with designer Robert Freeland in the United States to garner his feedback on the progress made. Further discussions were to be continued in the coming weeks.

References:

1. R. M. Freeland, Project Icarus, Firefly Icarus: An Unmanned Interstellar Probe Utilizing Z-Pinch Propulsion, Internal Project Icarus report, October 2013.

2. A. Hein et al., Project Icarus, TUM Ghost Team Design, Internal Project Icarus report, October 2013.

3. K. F. Long, R. Osborne, P. Galea, Project Icarus Starship Resolution Sub-Team Concept Design Report, Internal Project Icarus report, October 2013.

4. M. Stanic, Project Icarus Ultra-Dense Deuterium Based Vehicle Concept, Internal Project Icarus report, December 2013.

Becoming Interstellar Symposium

On Saturday 23rd November the Interstellar Research Centre played host to a symposium titled ‘Becoming An Interplanetary and Interstellar Civilisation: The Key Geopolitical, Economic and Commercial Considerations’. This was held at the main headquarters in Gloucestershire.

The 1920s and 1930s saw a surge of interest in the exploration of space in Europe and in the United States. This then eventually led to the advent of the space age in the 1950s and 1960s between the United States and the then Soviet Union. Since then we have witnessed space stations in Earth orbit, boots on the lunar soil and interplanetary probes visiting all of the planets of our Solar System. We have also seen the launch of the Voyager probes in 1977 which have now left our Solar System.

Fast forwarding to the early 21st Century, and we are now living in an age where there is a renewal of interest in sending humans back to the Moon and also a refocussing of long-term efforts towards landings on the planet Mars. In addition, we have seen new nations enter the activity of exploring space, including China and India, and the opening up of space to commercial ventures, to include asteroid mining operations and space tourism. Significant efforts have also been expended in reducing the cost to LEO, by using technology such as Single Stage to Orbit, or reusable rockets such as the SpaceX Falcon 9 or Blue Origins New Glenn. Both companies are also now looking at much larger launch vehicles, with the SpaceX Falcon Heavy which would transport 25 tons to LEO and the two-stage Blue Origin which would transport 45 tons to LEO. The US Space Agency NASA is also pursuing its Space Launch Vehicle (SLS) with a payload capacity to LEO of around 95 tons.

Also in the Commercial sector, the Breakthrough Initiatives has launched Project Starshot, and has allocated $100 million of funding to investigate sending a Gram-scale probe towards another star in the next two decades. Other activities including the announcement in the United States of the Formation of a Space Force and also the passing of the Space Act into Law in 2015 which will permit companies to mine asteroids and own those resources. It is also clear that the 1967 Outer Space Treaty does not cover all of these issues and is in need of revision.  Although historically NASA has not had an interstellar focus, in 2017 the US House of Representatives under the Chairman in charge of NASA appropriations, John Culberson did pass a bill mandating NASA to look at the problem of an interstellar mission to be launched by the year 2069, a century after the first landing of people on the Moon. That has led to a Johns Hopkins Applied Physics Laboratory study for a 1,000 AU probe that may be launched around 2030.

What does all this mean for the future of human kind in space? How will nations co-operate together or even compete? How do we avoid conflicts in the future? How do we use space resources to improve the well-being of human civilisation and create prosperity for all? What are the critical bottlenecks for success and failure? Finally, what does this all mean for our ability to transition from an interplanetary species to one that goes on to colonise the space around other stars – the ultimate goal of interstellar exploration?

Dr David Baker

To discuss these issues and more, we invited Dr David Baker to present a lecture, and to participate in an interactive meeting where all those attending to discuss these issues further. Dr Baker is a distinguished British Scientist who worked on the NASA Gemini, Apollo and Space Shuttle programs between 1965 and 1984. He is an independent space consultant and also works as a journalist and prolific author. He has published thousands of articles and over a hundred books and has taking part in numerous radio and television documentaries. He is the Editor of the British Interplanetary Society magazine Spaceflight.

One of the astonishing facts to come out of David’s presentation was the claim that for every $20 billion that the US Congress invests in space (the NASA budget) there is a return of around $200 billion. He also said that in 1969, 80% of scientists worked for the government on research and development, but in 2019 only 15% did, so we have moved to a dividend driven research. In addition, back in 1969, 85% of space money was from government but by 2019 it is only 15% and some 70% is driven by profit boost in the telecoms industries and others. Overall, the worldwide space expenditure was around $450 billion, and the tax paid by space companies more than pays for the amount governments spend on space. He also said that 60% of the global economy was dependent on space.

There was then four short talks given by different people. Kelvin F Long spoke about co-operation versus competition in the pursuit of space and talked about the pros and cons. Rob Swinney discussed non-profit (or not-for-profit) versus for-profit models for companies in space activities and again contrasted the benefits and disadvantages of both. Stephen Ashworth spoke about industrialisation versus sustainability in space and argued that fundamentally the only way to become sustainable is to firstly demonstrate such habitats on the Earth first. Richard Osborne spoke about Single Stage To Orbit, Two Stage To Orbit launches versus conventional and reusable rockets and which was the best approach to pursuing the construction of large space architecture such as a space station or world ship; he favoured TSTO. The participating members then enjoyed a long discussion on all the issues which included scientific-technical, political-economic, social-cultural and religious-philosophical. The participants then retired for dinner and continued the discussions.

Stephen Ashworth

Richard Osborne

Rob Swinney

Some of the participating members at the after event dinner, De Vere Hotel, Tortworth Court