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
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:
General discussions of interstellar transport.
Proposed methods of interstellar transport.
Relativistic effects.
Interstellar vehicle issues.
Life-supporting extrasolar environments.
origin of extrasolar life.
communicating with extrasolar intelligence.
Radio search for extra-terrestrial intelligence (SETI)
Non-technological discussions of interstellar travel.
Multiple topic books.
Compendia.
Bibliographies.
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:
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:
Foundations Age (1950 - 1973): Les Shepherd, Eugene Sanger, Freeman Dyson, James Strong, Carl Sagan, Robert Bussard, Robert Forward, D. F. Spencer, L. D. Jaffe.
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.
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.
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]](https://images.squarespace-cdn.com/content/v1/5ca7e28c32c85e0001f17bad/1574722073182-Z8X1NMNJ0QYPDRR8ADFN/Endeavour5_Scene+2.jpg)
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:
R. Freeland, Plasma Dynamics in Firefly’s Z-Pinch Fusion Engine, 71, pp.288-293, Journal of the British Interplanetary Society, 2018.
M. Lamontagne, Heat Transfer in Fusion Starship Radiation Shielding Systems, 71, pp.450-457, Journal of the British Interplanetary Society, 2018.
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:
R. M. Freeland, Project Icarus, Firefly Icarus: An Unmanned Interstellar Probe Utilizing Z-Pinch Propulsion, Internal Project Icarus report, October 2013.
A. Hein et al., Project Icarus, TUM Ghost Team Design, Internal Project Icarus report, October 2013.
K. F. Long, R. Osborne, P. Galea, Project Icarus Starship Resolution Sub-Team Concept Design Report, Internal Project Icarus report, October 2013.
M. Stanic, Project Icarus Ultra-Dense Deuterium Based Vehicle Concept, Internal Project Icarus report, December 2013.
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
The Sun is a giant fusion reactor, generating energy through the ignition of hydrogen fuels at the centre of its core, the radiation from which then takes around 50,000 years to travel through the opaque atmosphere to reach the outer envelope of the photosphere. Whilst a nuclear fission reactor will create lots of nasty radiation products which then have to be stored for tens of thousands of years, a nuclear fusion reactor on Earth would not have the same problems and is relatively clean whilst also offering the potential to produce reliable energy on the Earth for the national grid. If we can make it work in an Earth-based laboratory then this also brings the possibility of applying that same technology to a spacecraft propulsion system.
The key requirement to obtaining ignition in an inertial fusion capsule is through spherical convergence of a spherical fuel by hydrodynamic implosion to a state of what is called the fusion triple product. This species that the product of the confinement time, particle number density and the plasma temperature has to be greater than a certain number. When this occurs, then the fuel will ignite and generate a self-sustaining reaction and the goal is to produce more energy out of the capsule than went into creating it, so called energy gain. This criteria is also known as the Lawson criteria, named after John Lawson who first derived it in 1955 and then published it in a public document titled “Some Criteria for a Power Producing Thermonuclear Reactor” (Proceedings of the Physical Society, Section B, 70, 1, pp.6 - 10, 1955).
Conventional direct drive method of ‘hot spot’ ignition inertial confinement fusion
In conventional inertial confinement fusion, this state is achieved by impinging multiple laser beams onto the surface of the capsule, what is known as an ablator shell. These lasers will then mass ablate the surface causing a rocket effect and the transfer of momentum so that the spherical system starts to move inwards. The mass ablation also leads to a full ionization of the surface and so the creation of a corona layer of ions and free electrons; a plasma state. The goal is to compress the capsule up spherically and with high symmetry, until a high compression state is achieved at the centre and where the so called ‘hot spot’ ignition occurs under direct drive. The problem with this approach is that some of the electrons generated at the surface may be energised by the laser electromagnetic wave, and so accelerated up to suprathermal energies. This means that they will depart from a Maxwellian distribution and travel inwards into the fuel, ahead of the full compression. As they enter the fuel, they deposit their energy there and heat it up, so that it wants to expand, and this is an inefficiency on the implosion.
To help to mitigate some of these issues, at the National Ignition Facility (NIF) in San Francisco the team uses a ‘Hohlraum’ or radiation cavity, so that the implosion occurs via an indirect drive. That is, the lasers (192 in total) do not direct impinge on the capsule surface, but instead impinge onto the surface of a gold cavity that surrounds the capsule, and this then generates an x-ray heat bath which surrounds the capsule to ensure uniform symmetry.
Indirect drive ‘hot spot’ method of inertial confinement fusion
There is however another way of achieving energy gain, which has received little attention in the literature but most importantly for space propulsion, holds the promise of high gain. And by high we are talking about an order of magnitude higher than can be achieved in ‘hot spot’ ignition. The method is known as ‘shock ignition’ and some of the first to propose it included R Betti et al in “Shock Ignition of Thermonuclear Fuel with High Areal Density” (Physical Review Letter, 98, 155001, 2007) and L. J. Perkins in his paper titled “Shock Ignition: A New Approach to High Gain Inertial Confinement Fusion on the Ignition Facility” (Physical Review Letters, 103, 045004, 2009).
In shock ignition the primary drive pulse is initially used to slowly compress the fuel to a high density and a pressure of several hundred Mbar due to spherical convergence amplification, but under the threshold required for ignition. The return shock wave then centrally reflects and begins to travel outwards, but before this happens a second ignition pulse is sent into the capsule and the ignitor shock eventually collides with the outgoing return shock from the first pulse, sending a collision shock back inwards and thereby heating the central hot spot to ignition conditions. So shock ignition depends upon the dynamics and interaction of three shock waves, the initial return shock, the ignitor shock and the collision shock. This is a simple scheme and it does not require the use of any short pulse lasers; in the way that an alternative method called fast ignition would need for example. This then helps to minimise the laser-plasma instabilities.
One of the neat things about shock ignition is that the capsules have an unusually large ablator shell. This means that any suprathermal electrons generated in the corona will deposit their energy into that ablator shell and they will not make it into the fuel which would otherwise cause expansion. The result of this is that the energy deposition into the ablator shell therefore contributes towards the implosion, resulting in an amplification of the pressure pulse - and this is why a much higher gain is possible in principle.
For a normal NIF type hot spot ignition design capsule, the irradiation of the surface will also lead to Rayleigh-Taylor instabilities and will increase proportional to the capsule In Flight Aspect Ratio (IFAR) which is a measure of the average shell radius to its thickness (~2 for shock ignition, c.f 5 for conventional thin walled designs used in other methods). But for shock ignition, the IFAR is maintained low due to keeping on a low adiabat associated with the low implosion velocity promoting stability during the acceleration phase, this means that the RT instabilities for shock ignition are much reduced compared to conventional ICF.
Like many of the inertial confinement fusion capsule designs, they are untested to the point of ignition and gain. But it gives hope for the future that we have so many different types of designs to experiment with, to ensure we get the performance that we need for either an Earth-based reactor or a space based propulsion system. It is likely, that shock ignition designs will have a key role to play as we seek to optimise performance and mitigate losses whilst we are attempting to create a star in a reaction chamber on Earth or in space.
The television series Star Trek, was created by Gene Roddenberry. Since that original series which debuted in 1966 for three seasons on NBC in the United States, it has produced many spin-off series. This includes the original series (1966 - 1969), The Next Generation (1987 - 1994), Deep Space Nine (1993 - 1999), Voyager (1995 - 2001), Enterprise (2001 - 2005) and Discovery (2017 - present). This has been an amazing franchise which has also produced 13 motion picture films.
A warp drive Starship from the Star Trek Universe (Paramount Studios)
A key element of the Star Trek universe is the starships themselves, based on some undefined warp drive technology that manipulates space and time in a way that allows it to transport across the galaxy and beyond, and still be home for tea. From a physics perspective this appears to break all of the known laws as we understand them. In addition, the engineering challenges with constructing such a vast machine are daunting to say the least. As the episodes of Star Trek rolled on year on year, there were efforts by the production team to introduce a science basis behind the technology. This led to the invention of an entirely new language with mentions of technologies such as ‘dilithium crystals’, ‘tractor beams’, ‘replicators’, ‘universal translators’, ‘cloaking devices’, ‘deflector shields’ and a whole manner of other ideas.
It is interesting to note that whilst some of these technologies are far from being a part of the real world of science, others have actually maturated into actual devices, and the observation that science fiction inspires science as much as science inspires science fiction is an interesting one. Indeed, far from the sciences being seen as rigorous and the arts creative, it has been said that science needs the creativity to flourish and art needs rigour to have value.
So it was that in 1994, the Mexican physicist Miguel Alcubierre produced a paper titled “The Warp Drive: Hyper-Fast Travel within General Relativity” (Classical & Quantum Gravity, 11, L73 - L77, 1994), in which the author demonstrated how the General Theory of Relativity, allowed in principle for space to expand and collapse in a way analogous to a warp drive. This paper was such a seminal publication for the field, that it literally created an entire new genre of theoretical physics research. Even more amazing, when we consider that at the time Alcubierre was a graduate student. Although many of the physics issues for a workable warp drive still look prohibitively difficult, the fact that we can realise so much about this theoretical construct so earlier on in the birth of the idea, gives some optimism that the research may lead to something interesting at least.
Mathematical shape function visualised of the Alcubierre warp drive metric of General Relativity
However, there is an intriguing history of the design of a Starship from the Star Trek universe that many people may not be aware of, which is that, whilst in conventional engineering design shape tends to follow function, it is the other way around thanks to Gene Roddenberry, in that function follows shape.
The history of the creation of this starship, is described in the book by Stephen E Whitfield and Gene Roddenberry titled “The Making of Star Trek” (published by Ballantine Books, 1968). In this book the authors detail the design briefing specified by Roddenberry for the U. S. S Enterprise:
“We’re a hundred and fifty or maybe two hundred years from now. Out in deep space, on the equivelent of a cruiser-size spaceship. We don’t know what the motive power is, but I don’t want to see any trails of fire. No streaks of smoke, no jet intakes, rocket exhaust, or anything like that. We’re not going to Mars, or any of that sort of limited thing. It will be like a deep-space exploration vessel, operating throughout our galaxy. We’ll be going to stars and planets that nobody has named yet...I don’t care how you do it, but make it look like its got power.”
Then, so it was that the set designers came up with the gorgeous concept that we see in the television show and movies today. In the subsequent discussions with the set designers, when they made comparisons to the existing space program, or Buck Rodgers or Flash Gordon, the response of Roddenberry was “This we will not do”. The same response was given when comparisons were made to concepts from companies like North American, Douglass and TRW. What Roddenberry seemed to be reaching for was an acknowledgement that this machine was in the far future, and more advanced than even the most visionary thinking scientists of the day were conceiving.
Roddenberry wanted something that was beyond the reach of existing paradigms. This is consistent with the second law of the science and science fiction writer Arthur C Clarke who said “The only way of discovering the limits of the possible is to venture a little way past them into the impossible”. It is interesting to note that Roddenberry had previously had extensive discussions with Clarke and so was likely familiar with this law given it was published in his book “Profiles of the Future” published in 1962.
So it was that the team produced the beloved Starship concept of Star Trek, driven by an engine called a warp drive for which nobody could describe how it really worked. That warp drive, seems to have come out of the requirement not to have any smoke, flames or exhaust. From a scientific extrapolation perspective this made no sense at all. But form an artistic perspective it was pure brilliance and perhaps not something science would ever had created on its own; science needs the creativity of the arts.
This demonstrates the value of interdisciplinary thinking and the risks of working only in specialised areas. It is clear that to progress technologically science needs the arts. Would the idea of a warp drive ever been realised if it had not been conceived from this artistic background? We will never know for sure, but as long as we practice both in unison, as a form of joyous dance, the novelty produced from our species knows no bounds.
Starship Endeavour is a part of the Project Icarus suite of starship design solutions, as a part of an effort to redesign the British Interplanetary Project Daedalus flyby probe from the 1970s. It builds on earlier work for a single stage engine design known as Starship Resolution. However, the main problem with Resolution was its elongated boost duration of 15 years, and it was considered a major risk to the mission success, given the potential for issues like thrust structure fatigue and general system reliability.
To achieve this reduction in boost duration, Starship Endeavour instead was to employ a quintic engine design, that is with 5 engine bells, similar to say the Saturn V moon rocket. A trade-study had first been conducted to see the effect of increasing the number of thrust chambers or engine nozzles and it was found that by moving to more engines (parallelising the thrust profile) a significant drop in the boost phase was demonstrated, but all for a constant cruise velocity of 4.84% of the speed of light.
Starship Endeavour 1.0 Five Engine Bell (Quintic) Design Concept (Adrian Mann)
For example, whilst a single stage engine might take 13.2 years (skeleton concept) at a Thrust of 0.46 MN and a mass flow rate of 0.043 kg/s for 150 Hz pulse frequency, by having two engine stages the boost duration would be reduced to 6.6 years with a Thrust of 0.92 MN and a mass flow rate of 0.08 kg/s. Moving to a 3, 4 or 5 engine stage would reduce the boost down to 4.4 years, 3.3 years or 2.3 years respectively. However, this was for a skeleton concept in the trade-study rather than the full design configuration, but the benefit to engine staging was a clear route to burn time reduction.
The Endeavour Starship concept would also employ Deuterium / Helium-3 fuel but would only require 22,000 tons fuel for the acceleration phase and a further 4,000 tons for the deceleration phase (as opposed to the 50,000 tons of Project Daedalus). It would also utilise the Daedalus 2nd stage capsule designs but it would burn at a pulse frequency of 150 Hz, which was the same for the earlier Starship Resolution. It would exhibit an exhaust velocity of 9,210 km/s and accelerate at 0.13 m/s2 reaching a cruise speed of 13,300 km/s or 4.44% of the speed of light.
Starship Endeavour with Cylindrical Propellant Tanks (Adrian Mann)
The engine would produce a total thrust of 1.99 MN and a Jet power of 9.16 TW. The spacecraft would accelerate for 3.2 years to a distance of 3,747 AU. It would then cruise for a further 93.8 years over a distance of 263,161 AU. It would then decelerate for 2.9 years over a distance of 11,614 AU. It would complete its mission by arriving at its destination target in a total time of 99.95 years, under the 100 years project requirement.
Although Starship Endeavour looked more credible. the addition of the extra engines also created a more complicated radiation environment. In particular, one of the reasons for the original Daedalus team choosing a Deuterium/Helium-3 fuel for their design was because the reaction is aneutronic, and produces protons and helium-4 particles, both of which can be directed magnetically for thrust generation. However, it was pointed out in a paper by R. A. Hyde titled “A Laser Fusion Rocket for Interplanetary Propulsion” (IAF-83-396, 34th IAC, Budapest, October 1983), that Deuterium-Deuterium self-burn reactions within the fuel will lead to a large fraction of both low and high energy neutrons which will reduce the power. Hyde’s calculations showed that self-burn within the fuel will account for about 15% of the reactions, and then producing neutrons either directly or indirectly through Deuterium-Tritium reactions.
He also commented that any neutron capture by Helium-3 will produce Tritium and most of this will burn, even in the outer reaches of the pellet. Further, Hyde stated that at temperatures relevant to DD or DHe3 burn (around 100 keV) there would be copious production of x-rays due to bremsstrahlung radiation. For the Endeavour, the neutrons and x-rays presented a problem, not just for the engine bell, but also for the coupling between each of the engine bells now that there were 5 present in the design.
For some time the Endeavour design looked like it would fail. But two key design improvements saved it. The first is the adoption of a cleaver capsule design to ensure that the high energy neutrons and x-rays were adequately captured; this will be discussed in a later post. The second is the adoption of a radiation shield, based loosely on the Project Icarus Firefly design produced by Michel Lamontagne in earlier work titled “Heat Transfer in Fusion Starship Radiation Shielding Systems” (JBIS, 71, pp.450 - 457, 2018). This work is now being adopted into a redesign of the Endeavour Starship but with a 4-engine bell configuration, and this will be discussed in a later post.
The design of starships is far from easy. It involves many complex physics issues but also engineering issues in order to demonstrate that something is practical. Physics and Engineering are the two first hurdles to move towards a credible design. What comes after that is economics, and certainly the construction of spacecraft as ambitious as Daedalus, Resolution or Endeavour will not come cheaply. What is important, is to be able to justify those costs by the primary mission benefits but also the secondary society benefits. Ultimately, this has to be the test of all new technologies if we are to devote resources to their pursuit. The stars is no exception.
The Project Daedalus study ran from 1973 to 1978 and resulted in a systems integrated study of a starship design that was unlike anything that had been undertaken previously. However, years after the study it became apparent that there were many potential problems with the Daedalus design which might result in a mission failure, many of which the team was themselves aware of and they wrote about this in a 1984 review paper by Alan Bond and Anthony Martin titled “Project Daedalus Reviewed” (JBIS, 39, pp.385 - 390, 1986).
Some of the problems identified includes excessive fatigue on the thrust chamber with the high repetition rate of 250 detonations per second, the difficulty with mining Helium-3 fuel, the use of electron beams as the main energy driver for the detonations, and the production of x-ray radiation and high energy neutrons from self-burn reactions (e.g. Deuterium/Deuterium) inside the fuel. Others also identified other issues not identified by the Daedalus team, such as the use of a Deuterium/Tritium trigger at the centre of the fuel pellets, which due to Tritium decay produce substantial heat.
There was also a desire to reduce the overall mass of the system, reduce the environmental conditions and to significantly simplify the design. This resulted in a realisation of running the numbers on just using a Daedalus 2nd stage only, but also allowing for the additional fuel so as to bring the spacecraft into full orbital insertion from reverse engine thrust deceleration at the destination target; Project Daedalus was a flyby probe only and did not decelerate.
This resulted in a design concept called Starship Resolution, which was presented by Kelvin F Long, Richard Osborne and Pat Galea in a report titled “Project Icarus: Starship Resolution Sub-Team Concept Design Report” (Project Icarus Internal Report, December 2013).
Project Icarus Starship Resolution (Adrian Mann)
To reduce the environmental conditions the spacecraft would detonate capsules at a rate of 150 Hz (instead of the 250 Hz Daedalus) and it would utilise 20,700 tons of Deuterium/Helium-3 fuel for the acceleration, followed by 3,900 tons of Deuterium/Helium-3 for the de-burn. It would carry 12 propellant tanks for the boost and 4 tanks for the de-burn. It would use the second stage capsule designs of the Daedalus concept, which were 1 cm in diameter and 0.288 grams in mass. It would have a mass flow rate of 0.0432 kg/s for both the boost and the de-burn and it would exhibit an exhaust velocity of around 9,210 km/s.
In order to calculate the spacecraft performance in detail and with confidence, a Fortran program was constructed which firstly modelled the Daedalus design as a form of numerical validation of the model. This was then applied to the new design of Starship Resolution. The calculations showed the spacecraft would accelerate for 15.18 years, followed by a cruise phase of 81.47 years, then a de-burn phase of 2.86 years, bringing the spacecraft to its target destination in 99.52 years, which was less than the 100 years Project Icarus requirement.
Project Icarus Starship Resolution (Adrian Mann)
After the acceleration phase the spacecraft would achieve a cruise speed of 14,481 km/s or 4.83% of the speed of light. It would produce a Thrust of 0.398 MN and a Jet Power of 1.832 TW. It would deliver its 150 tons payload mass (instead of the 450 tons mass of Daedalus) to its target, where it would deploy orbiters, atmospheric penetrators and ground landers onto the local planets and moons of that system. This would enable a far more in depth study of astrophysics, planetary science, geology, and astrobiology than could ever be achieved through a flyby probe alone.
However, the main problem with the Starship Resolution design was its 15 years burn time. Considering the high risk of sub-system failures, this was deemed a substantial risk to the success of the mission, and it was desirable to reduce this significantly. This resulted in a new design called Starship Endeavour, which will be discussed in a later post.
A key fact to take away from the Starship Resolution design, is that it demonstrated that it was possible to reduce the mass and complexity of the Project Daedalus design. It also demonstrated that full deceleration was possible and therefore an interstellar flyby probe was difficult to justify. In particular, if the cost of such a mission ends up being a significant cost of the global economic output, then there is an argument that one may as well just build a larger ground or space based telescope or even a space interferometer. Making the probe fully decelerate into local orbit, would permit such much more science value, and even the biggest interferometer would find it difficult to compete with that value.
