Interpreting the Aliens

by Kelvin F Long

Quite a few years ago now I worked on a project with the U.S military. This was a dozen officers mostly of rank Captain and Major who had the task of developing a strategic contingency plan for a potential ET invasion. To be clear, this was a scenario training exercise and did not reflect an actual fear of a real threat to humanity. It was a lot of fun to see how these outstanding officers grappled with the various issues and assessed the limited data they were given in the scenario for events unfolding in the distant cosmos that pointed towards artificial megastructure engineering that was headed our way.

Since they were members of the military, they were very much threat oriented and this indeed was a part of their brief. To identify the threat and develop a mitigation strategy for the purpose of defence or even elimination of the threat. But this bothered me a little, since there was insufficient information to lead to a firm conclusion that a threat was imminent and I wanted to encourage the officers to think more out of the box in terms of questioning the chain of command instructions. In the military this is not really permissible of course and a chain of command is important for minimisation of errors, but given the gravity of the subject matter I wanted to encourage them to see a bigger picture and to develop an ability to challenge authority when it is appropriate.


Around the same time, a film had just came out titled ‘Arrival’ which was based on the short text ‘Story of Your Life’ written by Ted Chiang. In this story objects arrive on Earth and it is the task of the scientists to establish a line of communications with them - a species referred to as the heptapods. It was an excellent film and I have seen it several times since.

But one of the main issues that the story centres around is a misinterpretation of the intended message. The scientists believe that the heptapods are communicating “offer weapon”, which is then also interpreted by China to mean ‘use weapon’, when in fact the species is communicating the word ‘offer tool’ or ‘offer technology’. They simply want to establish a trading relationship with our species.

Knowing about this misinterpretation in the film, I decided to have a bit of fun with the excellent officers. I told them that in this hypothetical scenario a message had been received from one of the distant ET craft and that it was symbolic in nature, constructed of a group of Hieroglyphic like symbols.

I asked them in groups of three to see if they could work out what the message said. I gave them a set of 7 picture cards and firstly they had to put them into the right order. If you want to have a go at this yourself, then don’t scroll down yet since the answer is at the bottom of this post.

The officers split into their respective groups and they were given half an hour or so to come to a consensus about the message and also to put the cards into the right order. The chosen symbols were actually borrowed from ancient history on Earth and I used a combination of Egyptian Hieroglyphics and proto-Cuneiform since I had familiarity with both languages. I wanted to see how they would interpret the images.

A historical example in the history of Earth where a miscommunication occurred leading to tragic consequences was the Voyage of Captain James Cook who in the 1700s had landed on the coast of New Zealands North Island. Pulling alongside the East side of the Turangunui river near present day Gisborne he encountered the Maori inhabitants. But a leader from this tribe was immediately shot and killed whilst they were undertaking a ceremonial challenge to greet the new arrivals. Cook and his crew had misinterpreted this as a hostile gesture of war.

The military officers correctly put the cards into the right order as should be expected from what was highly intelligent individuals. But next came the issue of translating the message. There was a variation in the answers and this is to be expected since the challenge was somewhat ambiguous but they really enjoyed the task having spent the prior few days immersed in physics and engineering lectures so this was a welcome distraction. It was so long ago now that I don’t recall all of the group answers but for sure there was a variation.

The truth is that there was no right or wrong answer, since I had made up the message, but I wanted to leave in their minds a clear impression that (1) instructions for the annihilation of another should always be questioned when the consequences are so large (2) that messages can be misinterpreted and it was important to develop a critical thinking capacity and come to your own conclusion.

This is especially important when we live in a world with an incompetent leadership class across the political spectrum who neither serve the interests of the people who elect them, or make sensible decisions that lead to the improvement of society or the global community. Indeed, I would argue it’s even worse than that, in that we, the people of planet Earth, are deliberately deceived by every government of every country in the world on a regular basis. This points towards a profound problem in the human culture and the models we have adopted for how we elect our leadership class.

Given this, if ET was to come and visit us, we should be very careful about who we listen to and what information is communicated to us and therefore what are the motivations? Indeed, even on Earth one has to wonder in a geopolitical context what one nation is saying that is misinterpreted by another nation and how this can lead to dramatic consequences for everyone. Actions matter, but words matter too. Yet leaders across the world of all political persuasion are not careful with their words, but in fact they practice the opposite. We appear to live in a time where nation state diplomacy for the settling of disputes and civil discourse as a means for solving arguments is all but at an end. I worry about that. I worry about how we misinterpret each other.

When I was a child we learned the phrase “sticks and stones can break my bones but words can never hurt me”. But in the real world of nation state rivalry words can lead to chemical, biological or thermonuclear Armageddon. Words matter a lot!

So what did you come up with? My proposed answer is shown below. Remember this was just a bit of fun and I hope you enjoyed the challenge too.

Message read from Right to Left. The actual message intended was a request to meet in our system (star) at the first light (sun rise) and walk (foot) in the place where the mountains are (mountain), then to greet each other and in exchange a gift of precious metals (jewels) and tools (arrow) would be given to the humans. In return the aliens requested permission to mine (plough) hydrogen fuel (water) from the Sun (star) upon which their starship (boomerang) would then move off on a new trajectory away from our solar system (star).

Interstellar Probe Project

by Kelvin F Long

n 2018 I attended an awesome meeting at the Explorers Club in New York. The meeting was to discuss the design of a potential interstellar probe to travel to 1,000 AU, to derive its possible design definition and also the compelling science goals to be achieved. The project was led by scientists at the Johns Hopkins University Applied Physics Laboratory. The main requirement was to develop a probe that could travel at 50 AU per year and therefore reach the distance within around 20 years. Other than the initial meeting in New York, I attended meetings in various other locations around the United States including in New Orleans and California. In those meetings it was insightful to learn how professional spacecraft designers go about designing an interstellar probe and it was a privilege to be involved with the original concept definition as it began to materialise, with one of the earlier goals to generate a 30 W power capability within a 30 kg payload mass. Such a probe would explore the solar heliosphere, Kuiper belt objects and circum-solar dust disk and even a flyby of a Trans-Neptunium object. The interstellar probe would pave the way, scientifically, technically and programmatically, for longer interstellar journeys that would require future propulsion systems. It would go beyond the Grand Tour of the 1970s Voyager probes. It was recognised that a high solar system escape speed would be required, and probably at least twice the asymptotic speeds of Voyager 1 at its ~34 km/s. Two approaches were considered to include a passive one with a C3 launch and unpowered gravity assist, and an active one with a powered gravity assist and the use of in-space propulsion. This might include solar sails, solar electric, radioisotope electric, nuclear electric or nuclear thermal propulsion.

Although I was only involved with the project for the first year or so, I was highly impressed by the professionalism of the scientists involved who led the project. People like Pontus Brandt, Ralph McNutt Jr, Michael Paul and Jim Kinnison. Inspirational leaders reaching for the far frontier in space. The project was initiated in support of the Decadal Surveys of the United States and focussed on the time frame for a possible launch of 2023 – 2032. The final report is listed below and I was honoured to have my name listed as one of the collaborators for such an inspirational study. Below shows a photo from the meeting of the initial team in New York City in October 2018 held at the Explorer's Club.

INTERSTELLAR PROBE, HUMANITY’S JOURNEY TO INTERSTELLAR SPACE, NASA Solar And Space Physics Mission Concept Study for the Solar and Space Physics 2023 - 2032 Decadal Survey, led by Ralph L McNutt Jr, Michael V Paul, Pontus C Brandt, Jim D Kinnison et al., 13 December 2021.

https://interstellarprobe.jhuapl.edu/Interstellar-Probe-MCR.pdf

Inaugural Meeting of Interstellar Probe Working Group

First Contact with ETI

by Kelvin F Long

Recently I published one of my more speculative papers to date. I derived a very simple equation to estimate the time of first contact with Extraterrestrial Intelligence (ETI). This calculation neglected the possibility that they would come here and only considered (as a thought experiment) the possibility of us interacting with them either in deep space (in the space between the stars) or in their planetary system of ETI origin by one of our probes. The paper emphasised two key developments which will enable first contact being; advanced propulsion capability and the discovery of many exoplanets through astronomical observations. This calculation depended upon two factors (1) the growth rate to mature our technological propulsion capability to the appropriate velocity, where as a case study I examined up to 0.1c (2) the distance to the astronomical target where it is assumed an exoplanet has been discovered with the appropriate conditions for life, for which we may choose to send such a probe. I concluded that for interstellar targets out to 10 LY first contact may occur any time in the next ~25 - 174 years. For targets out to 100 LY first contact may occur any time in the next ~114 - 1,044 years. For targets out to ~200 LY first contact may occur any time in the next ~214-2,000 years. The range of values was a function of the growth rate parameter index. Any maturation of technology into the relativistic velocity regime will only serve to highlight these conclusions.

On the basis of the above I recommended that astronomers should give particular attention to any exoplanets within ~200 LY distance. Since this neglected the possibility of them coming here, and given the age of our sun relative to other stars, the probability that they would have been here already or at least had knowledge of us was argued to be high. This also implied that the scenario of an ETI presence in our own solar system was also high. Although, these conclusions do depend on the assumption of a galaxy that is filled with independent biogenesis which emerges purely as a function of chemistry and the rise of intelligence in the first place and so is the major uncertainty on any conclusions. This also makes certain assumptions about the nature of intelligent life as organic/chemical in origin when in fact it could be defined more broadly but this is beyond our current knowledge (i.e. Schrodinger's definition of life being a resistance from decay to thermodynamic equilibrium).

The paper was:

K. F. Long, The Temporal Contact Equation: An Estimate for the Time of First Contact with ETI, JBIS, 76(11), 279 - 282, November 2023.

Vorlon Cruiser Spacecraft from Babylon 5

Project Starshot

by Kelvin F Long

Last year I published a paper on dust erosion for the Project Starshot probe. This is in relation to my work on the Breakthrough Initiatives Project Starshot, where I sat on the advisory committee since it was first formed in 2016. It was a lot of fun and I got to work with people like Martin Rees, Louis Friedman, Phil Lubin, Geoff Landis, Greg Matloff, Avi Loeb, Jim Benford, Greg Benford, Pete Klupar, Mason Peck, Kevin Parkin, Pete Worden, to name a few...and even got to meet Frank Drake a couple of times before his passing. It was an honour to have worked on the project and I feel that the theoretical results from the study have advanced our knowledge about how to do beamed propulsion missions of this type. Project Starshot still continues of course and I hope will pioneer new and interesting results in the future. In my paper I estimate that the erosion rates over the ~20 year journey would be of order 10^-11 - 10^-8 g/s and including a design margin would suggest a shielding size of order ~3 - 7 mm thick for the Gram scale probe. Interesting to wake up this morning to the news that the New Horizons probe may have discovered an additional dust layer to the outer solar system. The paper was:

K. F. Long, Calculations of Particle Bombardment Due to Dust and Charged Particles in the ISM on the Project Starshot Gram-Scale Interstellar Probe, JBIS, 76, 94-111, 2023.

Below is a photo of the original Project Starshot advisory committee meeting at the house of our sponsor Yuri Milner back in 2016. I'm at the back next to Greg Benford. Below is also a photo from the meeting and it illustrates what it is like to work on such projects with many amazing people all dedicated to the vision of advancing spaceflight on behalf of humanity.

Typical Project Starshot Meeting discussing the technical program

Inaugural Meeting of Advisory Committee at the home of the sponsor Yuri Milner

World Ships

by Kelvin F Long

In some recent studies I have been looking at World Ships. These are massive vessels 10^11 - 10^12 tons travelling at 1,500 km/s (0.5%c) to reach the nearest stars in 1,000 years or less. They carry 1 million people at the start of the journey and allow for growth of that population. The design concepts were to be propelled by 1024 engines based on inertial confinement fusion systems and this requires a staggering 170 TJ driver energy assuming an optimistic 25% wall plug efficiency of any lasers. The individual pellets in the design are 230 grams each of TN fuel along with 2.43 kg/shot of expellant propellant for thrust augmentation, all detonated at 100 Hz pulse frequency. The first paper was published and examines population demographics, power supply requirements for the habitats and spin gravity to contain the atmosphere and regolith. The second paper is currently under submission and examines the propulsion system. These studies were based on earlier papers from Bond/Martin in 1984 which utilised external nuclear pulse propulsion and seeks to advance concepts to the next stage. Its not easy to push such a large vessel and requires a thrust of 978 GN.

K. F. Long, Population Demographics & Other Issues for the Massive Ra World Ship Model - Part 1, JBIS, 76(11), 262 - 272, 2024.

K. F. Long, Inertial Confinement Fusion Propulsion for the Massive Ra World Ship Model - Part 2, JBIS, Submitted, February 2024.

World Ship Frontal View

World Ship Rear View

World Ship under Construction in Earth Orbit

STV Hypothesis for the Fermi Paradox

by Kelvin F Long

Recently I published a paper giving an explanation for the Fermi Paradox which I call the Spatial-Temporal-Variance (STV) hypothesis. It relates to the temporal and spatial scales of emerging intelligent civilizations in the galaxy. Calculations were conducted for populations of von Neumann probes expanding out through the galaxy as a dispersal problem. I used geometrical series as a representation of the growth of a population and diffusion theory as a representation of the decay of a population. This results in two possible extremes including Drake-Sagan chauvinism for a crowded galaxy and Hart-Viewing chauvinism for a quiet galaxy, and then everything else in between. I argued that our galaxy is likely to be populated but sparsely.

For more information see the paper:

K. F. Long, "Galactic Crossing Times for Robotic Probes Driven by Inertial Confinement Fusion Propulsion", JBIS, 75, 118-126, 2022.

Discovery III

by Kelvin F Long

I have recently been working on a mission concept for the outer planets to Jupiter and Saturn. This is based on an earlier NASA study called Discovery II which was driven by a spherical magnetic torus fusion engine (which itself is based on the earlier Discovery I from 2001 A Space Odyssey driven by a gas core nuclear fission Cavradyne engine). The difference is that the Discovery III is also an ICF driven engine. As with the NASA mission it is designed to carry a 172 tons artificial gravity payload and 6 - 12 astronauts, completing the mission to Jupiter at ~5 AU in around 118 days and the mission to Saturn at ~10 AU in around 212 days.

The Discovery III engine would be 26 MJ driver energy delivered to a target of 2.88 milli-gram fuel with an assumed laser efficiency of 7.69% with a peak intensity of 4.7e17 W/cm2. Preliminary calculations suggest that the ICF engine may only require half as much thermonuclear fuel mass when compared to the magnetic fusion engine (Discovery III versus Discovery II) but this research is ongoing. A paper will be submitted on these calculations to a journal shortly.

NASA Discovery II

ICF Driven Discovery III

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.