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‘Deep Space Propulsion’: A Review

What I have in mind today is a book review, but I’ll start with a bit of news. The word from Houston is that Ad Astra Rocket Co., which has been developing the VASIMR concept from its headquarters not far from Johnson Space Center in Texas, has been making progress with its 200-kw plasma rocket engine prototype. VASIMR (Variable Specific Impulse Magnetoplasma Rocket) offers constant power throttling (CPT), which would allow it to vary its exhaust for thrust and specific impulse while maintaining a constant power level. CPT has now been demonstrated in a June test, as was reported at the recent AIAA Joint Propulsion Conference in Atlanta and in trade publications like Aviation Week, a useful step forward for the program.

VASIMR in Deep Space

What to make of VASIMR’s chances? When assessing something like this, I turn to my reference library, and because I’ve recently been reading Kelvin Long’s Deep Space Propulsion, I wanted to see what he said about VASIMR. Long treats the subject in a chapter on electric propulsion, a form of pushing a rocket in which a fuel is heated electrically, after which its charged particles are accelerated by electric and/or magnetic fields to provide thrust. The VASIMR wrinkle on electric propulsion is to use a fully ionized gas that has been heated hot enough to become a plasma, higher than the norm for most electrical systems.

Long’s explanation refreshed my memory on how all this works:

The engine is unique in that the specific impulse can be varied depending upon the mission requirement. It bridges the gap between high thrust low-specific impulse technology (e.g., like electric engines) and can function in either mode. The company who designs the VASIMR engine talks about possible 600 ton manned missions to Mars powered by a multi-MW nuclear electric generated VASIMR engine, reaching Mars in less than 2 months.

The proof is in the performance, of course, and we’ll see how VASIMR does in actual flight conditions. A 2015 flight prototype is in the works thanks to Ad Astra’s agreement with NASA. But Long’s book bears the subtitle “A Roadmap to Interstellar Flight,” so it’s intriguing to look at long-range developments with this technology. In theory, writes Long, a VASIMR drive could reach an exhaust velocity of up to 500 kilometers per second, corresponding to a specific impulse of 50,000 seconds, which translates into an Alpha Centauri crossing in 2200 years.

Now 2200 years may be progress — after all, Voyager-class speeds take 75,000 years to travel a similar distance — but if we’re talking about practical missions, VASIMR looks to be more valuable in the Solar System, assuming the technology lives up to Ad Astra’s expectations. But Long points something else out. A VASIMR engine could be considered a scaled down fusion development engine. The components that are similar to a fusion engine include the use of electromagnets to create a magnetic nozzle and the storage of low-mass hydrogen isotopes, along with techniques for energizing and ionizing a gas. Long sees VASIMR development as a way forward for understanding how to control plasmas in an engine for deep space.

A Survey of Interstellar Concepts

Insights like that make Deep Space Propulsion an instructive read. I find myself going back to specific sections and finding things I missed. The book has textbook aspects, containing practice exercises after each chapter, but it’s also enlivened by its author’s passion for finding the right tools to make star missions a reality. Long thus works his way through the major options, as we’ve seen in various recent Centauri Dreams articles where I’ve quoted him. Solar sails and their beamed power ‘lightsail’ cousins make their appearance, and so do futuristic concepts like the Bussard ramjet and its numerous variants. Just keeping up with the ramjet idea and how it has mutated over the years is an exercise in itself, but Long also covers antimatter, nuclear pulse (Orion) and exotic ideas like Johndale Solem’s Medusa.

It’s fascinating to work through these chapters and see how various physicists and engineers have tackled the interstellar challenge, spinning out a concept that is seized upon by others, modified, hybridized, and re-purposed as problems emerge and others solve them. Long was the guiding force behind the launch of Project Icarus, which is a re-examination of the British Interplanetary Society’s classic starship design of the 1970s. It makes sense, then, that fusion, which powered Daedalus, should be a major concern and a key element of the book.

Here it’s easy to get lost in the kind of details that, for me, make interstellar theorizing so endlessly fascinating. The BIS engineers knew their spacecraft would be vast to accommodate the propulsion needs of a vehicle designed to make the 5.9 light year crossing to Barnard’s Star, then thought to have planets. Work at Los Alamos and Lawrence Livermore National Laboratory had developed the idea of pulsed micro-explosions of small pellets using laser or electron beams to produce the needed fusion reaction. Long notes the contribution of Friedwardt Winterberg, whose study of electron-driven ignition became the core ideas of the Daedalus engine.

Winterberg is still, thankfully, with us, producing interstellar work that we’ve talked about here on Centauri Dreams, a remarkable link to a classic era of discovery considering that his PhD advisor was Werner Heisenberg. Long goes through Winterberg’s contribution and its adoption by Daedalus, work which continues to inspire the Icarus team as they develop and extend the Daedalus design. What the BIS came up with in the ‘70s was gigantic:

The propulsion system for Daedalus used electron beams to detonate 250 ICF [inertial confinement fusion] pellets per second containing a mixture of D/He3 fuel. The fusion products would produce He4 and protons, both of which could be directed for thrust using a magnetic nozzle. The D/He3 pellets would be injected into the chamber by use of magnetic acceleration, enabled by use of a micron-sized 15 Tesla superconducting shell around the pellet. The complete vehicle was to require 3 X 1010 pellets, which if manufactured over 1 year would require a production rate of 1,000 pellets per second.

Not only do you have extraordinary rates of production but you have the problem of finding the helium-3, which the Daedalus team addressed by considering a 20-year mining operation in the atmosphere of Jupiter. We’ll see how the Icarus designers solve the helium-3 issue, but it’s clear that the kind of nuclear starship envisioned by Daedalus would require an infrastructure throughout the Solar System that could reliably maintain large human crews in deep space and move industrial processes and products between the planets at will. There’s that ‘roadmap’ idea Long is talking about, as one developmental step builds upon another to make more advances possible. We can also hope that such advances teach us how best to contain our costs.

Making the Case for Star Missions

Like Gregory Matloff and Eugene Mallove, whose 1989 book The Starflight Handbook reviewed all the interstellar options then at work in the literature, Long’s Deep Space Propulsion offers a mathematical treatment of certain key ideas, especially useful for those coming up to speed on fundamentals like the rocket equation. Long throws in, in addition to the math, a good dose of interstellar advocacy. He’s keen on seeing design studies like Icarus continued around other possible technologies, so that we have constantly developing iterations of everything from nuclear rockets (NERVA) to microwave-beamed sails (Starwisp), a basis upon which future teams will finally build a starship. Along the way, generations of starship engineers learn and master their trade.

Could contests like the Ansari X-Prize be adapted for deep space missions? The book goes into some detail on how this model might work as a way of increasing the technological readiness of different propulsion schemes. But the process is lengthy:

…other authors have estimated the launch of the first interstellar probe will occur by around the year 2200 AD. This includes one author who looked at velocity trends since the 1800s. Factoring the likely uncertainties associated with the assumptions of these sorts of studies, particularly in relation to assuming linear technological progression, it is likely that the first interstellar probe mission will occur sometime between the year 2100 and 2200. To achieve this will require a significant advance in our knowledge of science or an improvement in the next generation propulsion technology. Given the tremendous scientific advances made in the twentieth century, it at least does not seem unreasonable to think that such a technology leap may in fact occur.

Creation of an Institute

Toward that end, Long has recently announced the formation of what he has called ‘the world’s first dedicated Institute for Interstellar Studies,’ whose logo you see here. The Institute is currently building a website and in a recent brochure states an accelerated goal for an interstellar mission:

“Our mission is to conduct activities or research relating to the challenges of achieving robotic and human interstellar light. We will address the scientific, technological, political and social and cultural issues. We will seed high-risk high-gain initiatives, and foster the breakthroughs where they are required. We will work with anyone co-operatively from the global community who desires to invest their time, energy and resources towards catalyzing an interstellar civilization. Our goal is to create the conditions on Earth and in space so that starlight becomes possible by the end of the twenty first century or sooner by helping to create an interplanetary and then an interstellar explorer species. We will seek out evidence of life beyond the Earth, wherever it is to be found. We will achieve this by harnessing knowledge, new technologies, imagination and intellectual value to create innovative design and development concepts, defined and targeted public outreach events as well as cutting edge entrepreneurial and educational programs.”

We’ll track this as it develops — for more information, contact Interstellarinstitute@gmail.com. Meanwhile, those wanting to keep up with the primary interstellar concepts should keep a copy of Deep Space Propulsion at hand. I started this post with a look at VASIMR because the whole range of electric propulsion concepts is intricate and in many ways confusing. Long’s chapter on this goes into the major divisions between the thruster types and untangles the issues around Hall Effect thrusters, MPD thrusters, pulsed plasma and VASIMR in ways I could understand. This is a book that will get plenty of use, and my copy is already filling with penciled-in notes.


Comments on this entry are closed.

  • Marc Millis August 10, 2012, 13:43

    “Who do ya call?” Dear readers, Are getting confused as to who is doing what and why there is a proliferation of interstellar flight groups?
    – British Interplanetary Society
    – Tau Zero Foundation w/ Centauri Dreams
    – Peregrinus Interstellar
    – Icarus Interstellar
    – 100 Year Starship Organization,
    and now..
    – Institute for Interstellar Studies.

    Rather than advocate our own, I want to take this opportunity to ask YOU, our readership: What do YOU want an interstellar organization to do? And when answering, keep in mind that none of these groups has “serious” money. The bulk of work is till subsidized by volunteered labors of love.

    Tell us, all of us, Where are your preferences? What services do you need?

  • An Infinitude of Tortoises August 10, 2012, 13:51

    How does one power one’s VASIMR vehicle, and how is the resulting system superior to, say, a solar-thermal rocket?

  • philw1776 August 10, 2012, 14:07

    VSAIMR is superior because it has higher ISP, the plasma ejected at higher velocity. That means more payload X velocity with less reaction mass (fuel). Also VASIMR has a high thrust mode vs wimpy solar-thermal albeit with lesser but still better ISP.

    VASIMR requires lots of watts, maybe a large photovoltaic solar array works for smaller systems in the inner solar system, otherwise nuclear to generate the electricity.

  • Bob Steinke August 10, 2012, 15:14

    I think one valuable thing that interstellar organizations could do is build up a library of reference mission designs and open technical problems.

    Beyond that, if there is any preliminary experimental work that is within their capabilities like the Planetary Society’s work on solar sails.

  • Rangel August 10, 2012, 15:20

    That’s good to see serious people doing effort to make advancements on the understanding of instestellar flights, where the great challenge is to create an efficient propulsion system.

    We already know that an advance propulsion system capable of reach velocities of 0.01c or higher is possible, soon or later it will be archieved. I don’t think that any propulsion system with velocities under 0.01c will be launched, but of course the new propulsion techniques even if not used on a real insterstellar mission can be used on a deep solar system mission, any new advance will not be wasted.

    I think it will be progressive, every new advance on propulsion we will make a new step on what we can “easily” reach. Today manned missions can only reach the Moon, Mars is possible but with a lot of cons like the time of radiation exposure and issues with the vision and bone’s mass loss, the bone issue can be “easily” solved by a new spacecraft with artificial gravity by centrifuge force, already possible with the Nautilus-X spacecraft NASA project, i really hope that this project become reality soon as possible, it’s a great project.

    I wonder if we’ll archieve a new radiation protection technique, if radiation is great reduced and we use centrifuge artificial gravity we can go further on space, and this archievemnt is a key for interstellar manned flight as well.

    I look forward at VASIMR advances, probably the best we can do right now to explore space, specially with the near future upgrades that it can archieve.

  • Paul Gilster August 10, 2012, 16:56

    An Infinitude of Tortoises writes:

    How does one power one’s VASIMR vehicle, and how is the resulting system superior to, say, a solar-thermal rocket?

    Nuclear is the way to go if we’re talking longer missions, and I would think it scales up pretty well. But we still have to see this concept tested in actual space operations. It’s a nuclear version that Ad Astra talks about for potential Mars missions.

  • An Infinitude of Tortoises August 10, 2012, 18:41


    Thanks. Actually, it turns out the main issue I was hoping to explore about VASIMR was made in this very forum back in 2008 (I thought this had a very familiar ring to it): https://www.centauri-dreams.org/?p=2507
    See in particular Dave Salt’s August 12th post. What has changed since then to make the prospects of powering a VASIMR Mars mission feasible (i.e., without defeating any advantages with a mass penalty)?

    And in any case, does it really matter when we have the option of the Robert Adams modified two-burn Oberth maneuver? Three months is so bad?

  • Paul Gilster August 10, 2012, 19:12

    Exactly so, and I’ll quote Salt on this:

    The real key to enabling such advanced space missions is — and has always been — the availability of an energy source with sufficiently low specific power. Unfortunately, this requires nuclear systems employing gas-core fission or nuclear fusion — solid core fission just isn’t good enough — and the technology challenge (and cost!) of fielding these are orders of magnitude greater than the VASIMIR “thruster”.

    VASIMR has a lot to offer but also a lot to prove.

  • J. R. August 10, 2012, 19:40

    I’ve been excited about the VASIMR concept for several years. It seems to be the next logical step in interplanetary propulsion. However, the way that it uses electrical input and magnetism to heat and compress the plasma, I’ve wondered about whether a future advanced version of VASIMR, providing even higher temperatures and compression, could eventually bring about highly efficient nuclear fusion propulsion.

  • Enzo August 10, 2012, 20:37

    Zubrin is ferociously against VASMIR. Here’s a very political, angry video from him :

    The very political way he starts might put you off. However, once you pass that, his technical arguments, based on power density, efficiency and cooling of the reactor appear to make sense. Not that I am an expert on this.
    I watched only about half of the first so far.

  • Interstellar Bill August 10, 2012, 20:46

    We need advanced, graduate-level textbooks on each propulsion option
    1. Laser sail
    2. Advanced Ion
    3. Nuclear Electricity for Space (every non-fusion method from radio isotopes to full scale fission reactors
    4. Fusion
    We also need anthologies of already-published, specialized interstellar papers. Both IEEE and BIS could alone do great anthologies.

    A textbook with one chapter each on these is far too introductory for the dear readers of this blog.

  • Rob Henry August 10, 2012, 22:31

    The dissuasion here has me realising the magnitude of my ignorance on this topic. I would be put back on track if someone could answer the following.

    If we ever had an interstellar space craft powered by a nuclear reactor AND we wished to give it a fair Carnot efficiency, The radiative area would be large.

    The best fissionable nuclear fuel has in the order of 10^14 J/Kg, so we would wish of ship loaded with fuel had at least a tenth that energy density. If that ship carried humans, it should be at least a million tonnes, and accelerate for no more than about 30 years. Here we would have to dissipate power at the rate of 100 TW. If we radiate the excess heat at one kilowatt per square metre we would need a surface of up to 100, 000 sqkm.

    I can imagine a highly conductive (metal?) surface skin, supported on advanced aerogels and with a carbon nanotube skeleton making such a structure possible but now…

    The heat dissipated by this craft hitting the interstellar medium at a percent lights speed has similar order of magnitude, meaning that this craft that has to have an exaggerated cigar shape, and opening the possibility that its engine might be better employed accelerating the charged particles in that medium once it has got up sufficient speed – or at least some fraction of its power should be used to that ends.

    Anyhow, a starship 1000km long and millions of times less dense than air is not one that I recall in any paper or science fiction. What am I missing here!

  • Joy August 10, 2012, 23:07

    VASIMR “requires nuclear systems employing gas-core fission”

    Only considered a low mass/power system because no one has ever taken the design concept beyond vague hand waving exercises. It would be simpler to just forget the VASIMR thruster and try to build a gas-core fission rocket, itself a very problematic project.

    “or nuclear fusion”

    Er, since when has any scheme for nuclear fusion had a low mass/power ratio? Are dilithium crystals involved? What VASIMR needs is to be mated to the massless energy module, which is a specialized perpetual motion machine immune to the effects of the Higgs field. /sarc

    Agree with An Infinitude of Tortoises, the VASIMR looks great on the lab bench, but cannot be evaluated for space propulsion without including the (considerable) mass of the power plant.

  • Greg August 10, 2012, 23:47

    “What do YOU want an interstellar organization to do? And when answering, keep in mind that none of these groups has “serious” money. ”

    Excellent question Marc, personally I would like to see a staged approach analysis to possible interstellar propulsion solutions. I think if a site could show a stage 1 analysis of possible technologies as well as theoretical physics giving its likelihood between a 1 and 10, 1 being next to impossible 10 being highly likely. It would simply be a group of researchers giving their best guess or analysis of a technology/theory and if it would be feasible or not.
    An example is this article on the Giant Casimir effect,
    using meta-materials to possibly amplify the Casimir effect. Between 1 and 10 what is the likelihood this is a possibility and if this could be worth pursuing as a means for energy production or propulsion for interstellar travel.
    Stage 2 could be a more detailed analysis of technologies. With stage 3 possibly moving to testing in a lab.

    It would be nice to cut through the impossible stuff and speaking for myself, see what may get through.

  • Jean-Pierre Le Rouzic August 11, 2012, 6:22

    To contribute with my own answer to Marc’s question: What I wait from an organization is any concrete achievement, even if small. Like Bob Steinke, I found Planetary society’s solar sail design and launch attempts to have lots of merits. If someone wants to search (as Paul proves daily) there are valuable scientific papers, but for every good paper there are tons of s**t papers, often using arcane physics concepts to propose what is basically perpetual movement machines. There are already many students that are interested by interstellar concepts (f.e. see what F. Loup did). What we need is not visionaries, there are already some very impressive people and it’s good to talk about them, but we now need project leaders with common sense and attention to details and engineers. We need people able to understand that to build interstellar probes, we have to demonstrate concepts validity and how it could be useful by some aspect to humanity in short term.

    Marc: What you can do without money is set a call for realistic interstellar proposals with positive impact on today’s life, with a team of volunteers to select a few very interested works with clear selection criterion. You don’t need to propose a price to recruit volunteers and contributors, many organisations only propose fame and it works (IEEE/Arthur B. Guise Medal (fire protection engineers)). Some even do not propose fame (scouts).

  • Astronist August 11, 2012, 10:10

    Marc Millis wrote: “What do YOU want an interstellar organization to do?”

    To my mind, possibly the most urgent task is to develop and publicise a scenario in which we actually get to do interstellar travel, starting from the present day. Why urgent? Imagine that we start discussing interstellar travel with a member of the large majority of people who are not, for whatever reason, excited by the prospect. What will be on their minds? Overpopulation: we must reduce the world’s population. Climate change: we must give up an energy-intensive lifestyle (see Tom Murphy’s “Do the Math” blog for a diet of pessimism on this point, thus directly contradicting any chance of a starfaring future, given the enormous energy demands of interstellar travel). World hunger: we must abandon spaceflight and spend the money on feeding the poor instead. Militarism: we must abandon spaceflight because all it’s doing is spreading evil American militarism and greedy anti-human capitalism into space (the position of the Global Network Against Weapons and Nuclear Power in Space, and of its sociologist supporters who came to talk at the BIS a couple of years ago).

    In other words, I detect a general mood of antipathy towards the value system of growth and progress, which would basically shut down space technology and economic growth if it could, and impose a competing value system based on values of being contented with what one already has and renouncing the accumulation of more material possessions, as well as halting progress towards such things as artificial intelligence, genetic engineering and nanotech.

    Clearly, the market is on our side: people generally place a higher value on their comfort and on having the latest gadget than on ideology, particularly self-effacing ideology, and the market is great at driving forward economic and technological progress. But I still think we would be well advised to put at the heart of our message to the broader world a reasoned explanation of why growth and progress are still good, why their benefits outweigh their risks, why climate change, peak oil and nanotech are not about to destroy us, and why the interstellar enterprise is not merely a juvenile-minded hobby that we happen to want to indulge in at everyone else’s cost, but the logical result of the growth of civilisation in a way which benefits everybody.

    Oxford, UK

  • Eniac August 11, 2012, 10:35


    If we radiate the excess heat at one kilowatt per square metre we would need a surface of up to 100, 000 sqkm.

    This assumes a radiator at ~300K. You can radiate 10,000 times as much at 3000K. Only the parts actually dissipating energy need to be at high temperature, so my image of the starship is not like your Zeppelin, but more like a firefly. Functionally designed living/storage areas, with a glowing hot drive unit in front or behind, like a light bulb. Plus, a huge amount of fuel, in front, where it can serve as a shield. For the reasons you mention, the whole thing will probably be very long and thin, like a train.

  • Alex Tolley August 11, 2012, 12:34

    @Enzo – thank you for the Zubrin on VASIMR link.

    While Zubrin is beating up on VASIMR in this instance, I think his overall frustration about the MO of human space exploration is justified. We’ve become incredibly cautious about doing anything. Reducing risks requires more cost which increases the cost of failure. What we need is the equivalent of a conestoga for space. Perhaps the private space initiatives may overcome this, or the programs of the newer space nations.

  • Alex Tolley August 11, 2012, 12:50

    The radiation hazard has become the big bugaboo of space flight. The Zubrin link dismisses the hazard by putting the doses in perspective. The solutions assume reduce exposure time by faster flight, or reducing intensity with shielding mass. Perhaps what we should be doing is researching potential biology/drug solutions rather than physical ones. We appear to be getting a much better idea about the biology of cancers, so possibly pharmaceutical research in treating them might produce superior protective compounds that will significantly reduce this particular hazard.

  • Kelvin F. Long August 11, 2012, 12:54

    Marc Millis wrote:
    “…Rather than advocate our own, I want to take this opportunity to ask YOU, our readership: What do YOU want an interstellar organization to do? ”

    My top five answers:
    1. Demonstrate both theoretical and experimental progress towards the long term vision, utilizing rigorous scientific techniques, across the spectrum of options, producing tangible benefits and real technologies.

    2. Demonstrate inspired leadership, good mangement and governance in an open, transparent and responsible way.

    3. Initiate bold and exciting projects and programs which inspire the world, swell our numbers, and produce more reliable studies.

    3. Work together, co-operatively and co-ordinatively, for common purpose, shared ambitions and increased national and international impact, in a way that rises above politics and human behaviours.

    5. Break down barriers to participation, knowledge, and belief in the seemingly impossible, by the creation and facilitation of opportunity through education and outreach, using positive-optimistic motivation.

    Kelvin F. Long

  • A. A. Jackson August 11, 2012, 13:55

    @Interstellar Bill
    Yeah … on books…
    Are Bussard and DeLauer’s books still the only hard core technical books on nuclear rocket propulsion? I mean , I know some recent technical books , with sections, such as the one here as a topic, Czysz and Bruno , Millis and Davis , seem ol’ Geroge Sutton’s last editions covered nuclear rocket propulsion, but I know of nothing like Bussard and DeLauer … tho I might be missing something?
    I do know ,maybe 15 years ago, I looked thought Nasa Star (that service is gone I guess) and found about 2 or 3 Russian books devoted to nuclear rocket propulsion, took a look at them on microfiche , they looked very inclusive, but I don’t read Russian.
    I recommend these books to the AIAA as candidates for translation and publication, never heard a word from the AIAA. I never seen a hard copy of these anywhere, I guess they exist!

    Here one thing I wish I had.
    Example, a long time ago Dover books published all the important papers on Quantum Electrodynamics in a single paperback volume (I don’t know if it was a reprint, I think not). So I would love to have in my possession a collection of all the important papers , hard technical papers, on interstellar propulsion, these are scattered over Acta Astronautica/Astronautica Acta, JBIS, AIAA Journals… much of the relativistic dynamics (pertinent to propulsion) works would be handy to have in one place… and these are really spread out.
    I would love it to be a hard copy, but electronic would be ok.
    Is someone working on something like this?
    Note I mean ‘hard physics…engineering physics’ type of referred journal papers.

  • Kelvin F. Long August 11, 2012, 14:00

    Incidentally, if anyone would like to get involved with the institute for Interstellar Studies, please email me at the address below. The opportunities are wide and varied.


    Kelvin F. Long

  • Brett Bellmore August 11, 2012, 14:21

    “An example is this article on the Giant Casimir effect,
    using meta-materials to possibly amplify the Casimir effect. Between 1 and 10 what is the likelihood this is a possibility and if this could be worth pursuing as a means for energy production or propulsion for interstellar travel.”

    Somewhere below 1, I’d say; The Casimir effect is conservative.

  • Michael August 11, 2012, 14:24

    If we are ever to make the ‘leap of leaps’ from our shores to other stellar shores we must endeavor as never before to delve into the smallest of the small and fear not the overwhelming vastness of space or be intimidated into submission by the task before us. Our goal can only be achieved if we pour immense effort into it by applying our collective intellects, knowledge and letting go the reigns on our imagination, only then can humanity proudly stand on those distant beckoning shores.

    Michael G. Million

  • Michael August 11, 2012, 14:54

    Perhaps we could accelerate each component of a interstellar craft from multiple very high velocity launchers in parallel (rail guns) and with suitable control mechanisms allow them to reassemble into single functioning craft?

  • Jack Crawford August 11, 2012, 15:51


    At this early juncture I think Tau Zero needs to differentiate between being a promoter, an enabler, and a driver of interstellar flight. Of these three things I think acting as an enabler is the easiest to do on a tight budget because it can be done by volunteers as a labor of love while research and public awareness cost money. As an enabler, Tau Zero’s role is to act as a compiler and distributor of knowledge. By acting as a venue for the exchange of information, such as a a free peer reviewed online journal, the Tau Zero Foundation can be a safe haven for scholarly writing, review papers, and general education.
    Currently, the literature for interstellar studies is greatly scattered which makes finding and following the literature trail difficult. This impedes research. Review papers can address this and another problem: the academic pay wall to information. Think of the audacity of having to pay $80 for a 10 page paper on the subject you are interested in only to find the paper doesn’t deliver what the abstract says was in the paper. This is our enemy: inaccessible and poor quality information. Help from academia is not coming any time soon so the burden for progressing interstellar studies is on the citizen scientist and engineer, but someone has to give them the tools to succeed. Tau Zero can do this. Important but obscure information can be compiled and rewritten for public consumption. Code for common numerical calculations can be made freely available. Scholarly articles can be held to a higher standard. Proper education articles aimed at the armchair enthusiast can also be written. All you need are volunteers to write and some editors.

    ~ Jack Crawford

  • Rob Henry August 11, 2012, 21:06

    Eniac, thanks for your intriguing construction of how VASIMR might one day work in the service of deep space propulsion. Unfortunately it presents me with a new puzzle.

    If the cooling fins of the power plant to which VASIMR is coupled radiate at 3000K, what figure do you have in mind for the core temperature of the hypothetical reactor? And would it still operate via a *heat pump* as traditional nuclear reactors do?

  • James Jason Wentworth August 12, 2012, 2:18

    Alex Tolley wrote:

    “The radiation hazard has become the big bugaboo of space flight. The Zubrin link dismisses the hazard by putting the doses in perspective. The solutions assume reduce exposure time by faster flight, or reducing intensity with shielding mass. Perhaps what we should be doing is researching potential biology/drug solutions rather than physical ones. We appear to be getting a much better idea about the biology of cancers, so possibly pharmaceutical research in treating them might produce superior protective compounds that will significantly reduce this particular hazard.”

    In the 1950s, nuclear physicist Stanton Friedman worked on the NB-36 project, which involved flying a powered-up nuclear reactor aboard a modified Convair B-36 bomber. The reactor did not power the aircraft, as the project was conducted to study the effectiveness of radiation shielding in preparation for future nuclear-powered aircraft. Also:

    In connection with the objections to long-duration crewed space missions on the grounds of the radiation risk, Friedman wrote that during the NB-36 project the health physicists discovered that the human body has built-in repair mechanisms that can heal radiation damage to tissues, as long as the radiation dose is sufficiently low over a long period (a dim light shining for a long time rather than a bright instantaneous flash, to put it colloquially). As well:

    A few years ago, a UK group demonstrated an *active* radiation shield that could be used to protect the crews of interplanetary spaceships (and by extension, starships). In a test chamber, a model spacecraft encircled by a super-conducting wire “hoop” successfully created a miniature magnetosphere that kept high-velocity charged particles (simulated solar radiation and cosmic rays) from reaching the model spacecraft.

  • spaceman August 12, 2012, 3:08

    The aforementioned interstellar organizations will– certainly in a more realistic manner than does the film industry– definitely go along way as it pertains to keeping the grand goal of crossing the light years alive. Assuredly, new ideas will originate from these groups and existing ideas will be further refined as technology advances.

    As a lover of puzzles, I would like to see the interstellar dream presented as the ultimate puzzle– a puzzle that combines several branches of science both natural and social. So geniuses put down your NYTimes Saturday crossword, which of you has what it takes to crack this one? What could be more challenging and exciting, more important in terms of ensuring human species survival than solving this intricate conundrum of epic proportions?

    But it’s like what a friendly fellow at a recent singles party said to me: “When I was your age I used to think that if I waited around it would all fall into place. The right woman would just enter my life…but that’s unlikely. You have to get out there and do the hard work of finding her.”

    How true. I can and do imagine her. I think about the pros and cons of getting involved with her, but at the end of the day I know the imagining will only get me so far. He’s right, I have to get out there more and test the waters. Same is the case with interstellar societies…they are a great resource for thinking about, for example, which candidate propulsion systems might work best as well as other aspects of deep spaceflight. Imaginative interstellar groups are crucially important in terms of developing ideas on how it might be possible to effectively span the immense interstellar gulf, but eventually they—like me, will have to get out there and test/implement the ideas in the real world.

  • Alex Tolley August 12, 2012, 18:25

    @ JJ Wentworth
    health physicists discovered that the human body has built-in repair mechanisms that can heal radiation damage to tissues, as long as the radiation dose is sufficiently low…

    This is well established. The problem is that radiation in space, especially from unblocked cosmic rays, is too damaging to be managed by the mammalian DNA repair mechanisms. Some organisms, such as the famous Deinococcus radiodurans can withstand very high radiation doses as they have special protective proteins. Assuming humans won’t be engineered in the near future, what we need is a way to protect against the damage. This may involve drugs that stimulate DNA repair, or eliminating the damaged cells before they can proliferate, perhaps through triggering apoptosis.

    I keep hearing about electromagnetic shields as charged particle reflectors, but they never seem to be developed for spaceflight hardware. Is the issue power requirements, unacceptable mass requirements, electronic systems interference or something else?

  • Gregory Benford August 12, 2012, 18:51

    It’s time to lay to rest the entire view expressed: “Work at Los Alamos and Lawrence Livermore National Laboratory had developed the idea of pulsed micro-explosions of small pellets using laser or electron beams to produce the needed fusion reaction.”
    Many billions have been wasted on this program, which was NEVER intended to be more than a bomb simulation program. I left Livermore over this in 1971, sure it would never work and its public fusion power facade would crumble.
    So it has. Their trials the last few years have failed and they are doomed.
    A starship based on this is laughable. On a MOVING, vibrating ship you must hit tiny pellets repeatably hundreds of times per sec?
    Anyone sticking with such a design should be aware of this.

  • Gregory Benford August 12, 2012, 19:20

    My brother points out I should mention I left Livermore for UCI because Edward Teller wanted me to head the theory division of the laser fusion program. I couldn’t in all conscience pretend to believe in the agenda.

    ON VASIMR: unless it got fusion, it’s basically a heavy electric engine with massive magnets. But fusion won’t work–Livermore also showed that mirror reactors make no sense, and never got remotely close to a burn. VASIMR is a dead end.

  • Brett Bellmore August 12, 2012, 20:51

    “If the cooling fins of the power plant to which VASIMR is coupled radiate at 3000K, what figure do you have in mind for the core temperature of the hypothetical reactor? And would it still operate via a *heat pump* as traditional nuclear reactors do?”

    It’s hard to imagine what solid structures could work for a reactor whose *radiator* was at 3000K, and which had a high enough working temperature to run a Carnot cycle at reasonable efficiency. Perhaps a plasma core reactor generating power via an MHD device, and using the spent plasma as a radiator before running it through the cycle again.

    But, if you were going to use either fission or fusion to drive an interstellar ship, why wouldn’t you do so directly? Orion, or some variation on the concept?

  • Greg August 12, 2012, 21:29

    Brett Bellmore said, “Somewhere below 1, I’d say; The Casimir effect is conservative.”

    I’m not asking for a simple Google search or a negative answer because its easy. What I would be looking for is a well thought out reason why or why it wouldn’t work. I know as an engineer that most ideas or theories do not turn out as workable. Whats needed is an objective analysis and a clear and concise explanation by the experts in the field.

    I ask this because so many memes like that of the ‘cold fusion’ crockery that so many people want to cling to in belief, need to be clearly explained away.

  • Eniac August 12, 2012, 23:06


    If the cooling fins of the power plant to which VASIMR is coupled radiate at 3000K, what figure do you have in mind for the core temperature of the hypothetical reactor? And would it still operate via a *heat pump* as traditional nuclear reactors do?

    Ideally, you would have a hot plasma, magnetically contained, that would generate the energy by nuclear processes (fusion, fission, antimatter, whatever. There would be four ways for the energy to be rejected 1) in the form of accelerated particles out the back (good), 2) in the form of electromagnetic radiation out the back (not too bad), 3) in the form of neutral particles or electromagnetic radiation in all direction, directly from the plasma (bad), and 4) in the form of heat absorbed and reradiated through the spacecraft (very bad). Any engine design should try to maximize the good and minimize the bad, of course.

    The worst of all such designs is the electric one, where energy is produced separately from the propulsion unit, such as VASIMR or any other electrically powered ion-engines. It is still much better than chemical rockets, though, and the most doable. If you have to use this scheme, then, you would operate a nuclear reactor at very high temperatures (above 2000K, ideally, materials permitting), and then use a thermionic converter to generate electricity. You would NOT optimize for Carnot efficiency, rather you would optimize a more complex function involving radiator mass. Your ideal rejection temperature is then likely to be quite high (~1500K, perhaps), which would lead you to the light-bulb design. Your reactor core would be made primarily out of highly refractory fuel-oxides (U or Pu), and the thermionic converter out of highly refractory metal such as tungsten. You would keep reactor and drive close together and hot, and would insulate them thermally from the rest of the ship using an umbrella style shade.

  • An Infinitude of Tortoises August 12, 2012, 23:32

    Alex Tolley: On the subject of radiation protection, one approach not so often mentioned (might there be a reason for this?) is polyethylene; see, e.g., http://science.nasa.gov/science-news/science-at-nasa/2005/25aug_plasticspaceships/ .

    Greg Benford: Regarding your leaving Livermore — good for you, man, good for you!

    Et al.: So, no opinions on the utility of the Robert Adams modified two-burn Oberth maneuver (hereafter RAM2BOM, unless anyone has a better acronym) as a way of neatly bypassing the variety of technological dead-ends we’ve been anatomizing here? Or was that already covered way-back-when?

  • William August 13, 2012, 1:02

    Perhaps energy could be beamed to a spacecraft with a photovoltaic array and a VASIMR engine, providing it with the necessary power.

  • Ric August 13, 2012, 4:10

    Seems to me that the Interstellar Institute already exists: Zero Tau. So why not slightly expand the scope of the Zero Tau website and merge the Intersteller Institute topics into it?

  • william August 13, 2012, 4:33

    I went to the suggested link that led to the YouTube page that presented the criticisms in applied by Dr. Zubrin in his review of the VASIMR program. While I am certainly no expert upon this propulsion system the particular arguments that he made seem to highlight as to why this system may be merely a mirage. The one thing that really stood out for me in his argument was the fact that the Ions produced that are in the plasma do not appear to be neutralized, rather they are vented out into free space as positive particles which causes charge separation which is simply no good from the stand point of propulsion.

    I was a little surprised by these revelations for the simple reason that the Wikipedia webpage suggested that was a good propulsion system that would have advanced propulsion capabilities. Given also what appeared to be practical engineering difficulties surrounding the heating issue if it would appear to be almost impossible to provide a sufficiently small radiator mass that could dissipate the heat effectively. This brings up a very important point concerning all Carnot type of heat engines.And that is simply this; all types of systems that are capable of doing work usually do so at fairly large inefficiencies. The best man-made machine which can in fact provide a reasonable type of efficiency is a gas turbine type of engine I recall a figure of about 60 percent. Because of these inefficiencies a great deal of the potential energy that would be able to do useful work would in fact be dumped overboard as waste heat thus the need for enormous radiators.

  • Adam Crowl August 13, 2012, 7:29

    Hi Marc
    An interstellar organisation with the aim of achieving interstellar flight needs to look at the many propulsion suggestions made over time and the broader pre-conditions needed to make the various scenarios happen. For example, what kind of society can make a large multi-stage fusion-propelled probe happen? What economic pathway will make that feasible? And how will it transform life for the rest of humanity?
    Or what would lead to huge multi-terawatt lasers able to push sail-craft to half the speed of light? Would powering such devices lead to abundant solar-power systems for human-kind?

    Being able to live in space for decades at a time would have implications for recycling and food-processing in a multitude of ways, surely a vital concern on a crowded Earth. By promoting development of minaturised industry, food-production, medical facilities and scientific equipment – all applicable to humans thriving in other star-systems – then we’d be sparking unimaginable leaps forward for everyday life on Earth.

    Kick-starting the economic infrastructure needed to develop the solar-system will be another area for the interstellar organisation. For example, Philip Metzger (and his NASA colleagues) have some interesting proposals for boot-strapping space-industry via the Moon’s resources. Well worth exploring further the whole idea of teleoperated, semi-self-replicating remote facilities on the Moon.

    What we need to do is get away from the vision of the one-shot effort. Interstellar involves everyone and could well transform the world.

  • Alex Tolley August 13, 2012, 10:49

    @ Inifinitude of Tortoises

    From your referenced article on polythene spacecraft:

    Cucinotta and colleagues have done computer simulations to compare the cancer risk of going to Mars in an aluminum ship vs. a polyethylene ship. Surprisingly, “there was no significant difference,” he says. This conclusion depends on a biological model which estimates how human tissue is affected by space radiation–and therein lies the rub. After decades of spaceflight, scientists still don’t fully understand how the human body reacts to cosmic rays. If their model is correct, however, there could be little practical benefit to the extra shielding polyethylene provides.

    A simpler solution is to have the crew spend most of their time nestled amongst the propellant tanks, which carry a large mas of low atomic weight material for the return flight. Alternative designs that use high ISP engines (e.g. electrothermal) would allow the propellant mass to be used up in transit, therefore providing propellant shielding for the outward bound journey, even if ISRU was used for the return.

  • Marc Millis August 13, 2012, 11:23

    Thank you to those who answered my question. I am already compiling those answers… and I hope to turn them around into a Centauri Dreams post for future insight.

    Making progress is hard and frustrating; technically, financially, and in getting the community to align their work to avoid redundancy and avoid unnecessary competition.

    Best wishes to us all.

  • Brett Bellmore August 13, 2012, 12:57

    “I’m not asking for a simple Google search or a negative answer because its easy. What I would be looking for is a well thought out reason why or why it wouldn’t work. I know as an engineer that most ideas or theories do not turn out as workable. Whats needed is an objective analysis and a clear and concise explanation by the experts in the field.”

    “The Casimir effect is conservative” wasn’t based on google, it was based on my having aced engineering EM way back in college. You could go into excruciating detail, but you’d just be taking “the effect is conservative” and elaborating on it. The effect being electromagnetic in nature, and the EM field being conservative, really IS why it won’t let you do what you want with it. Don’t let the effect’s relation to zero point energy fool you on this, expecting to generate enormous amounts of energy this way is similar to thinking you can make a free energy generator by assembling magnets in the right way, because that won’t work for the exact same reason: The EM field is conservative.

    You can use the Casimir effect to store modest amounts of energy, reversibly. At most it might make a decent battery. It is not going to let you store energy on the scale needed for interstellar travel.

    The difficulty of storing sufficient energy to power a propulsion system is the fundamental obstacle to interstellar travel. Even nuclear reactions are marginal in this regard. This is why I’m convinced only beamed power systems will be feasible.

  • Kelvin F. Long August 13, 2012, 12:58

    Dear all,
    I completely agree with the comment by Adam Crowl: “What we need to do is get away from the vision of the one-shot effort. Interstellar involves everyone and could well transform the world”.

    As a community we need to pursue all of the options and keep in mind BOTH robotic and human applications. There are fundamental problems to address, such as how small can you make a nuclear fusion engine? Can we generate power sources MW/kg capability for deep space missions? Are microwave beam driven system appropriate to human as well as robotic missions?

    Regarding nuclear fusion, I don’t agree with the sentiment expressed that the facilities attempting to achieve inertial fusion is a façade. Although those facilities may have many research purposes to justify their funding and very existence, it is a genuine attempt to produce this urgently needed energy system to replace the inefficient systems and environmentally destroying systems we as a society have been reliant on for decades. We have to put the challenge into context, in essence they are trying to create a star on Earth. This is not an easy feat and it should be no surprise that it takes decades of research and experimentation. A star, will take far longer when you consider the entire molecular gas cloud collapse from a gravitational instability, which occurs over many millions of years. Humans, are trying to create mini-stars in a matter of a century or less. A testament to the ingenuity of the human mind and our own self-confidence to conquer science and create new technologies for the betterment of the human species. I don’t mind that it costs many billions, it is what I expect for such a high technology enterprise. I don’t mind that it has dual purposes, the US government paid for it after all. The facts are – there is a facility, NIF, which is making the attempt. The benefits to our civilization if they are successful, are surely worth the effort and the many failures along the way. It is so easy to lay into those efforts and declare it a failure ahead of the program completion, than it is to support those efforts even if they do fail, so that we can learn from the experiment how to eventually build a better machine.

    The efforts by Icarus Interstellar to demonstrate a theoretical propulsion concept such as Project Icarus should be applauded and encouraged, rather than criticised. Because from that study we get several things (i) a reliable set of reports on what it takes doing it that particular way, rather than just casual speculation (ii) a whole new generation of designer capable people, who can do the calculations and apply them to other concepts, propulsion or otherwise (iii) the possibility of new inventions and technologies which have spin-off applications (iv) the creation of intellectual value and an innovation culture (v) a forum by which to engage the wider public and media on the value for space exploration to us as a society. Note also, that all of these individuals are volunteers, giving up their own free time, away from their families, because they believe in a shared goal. This is the best of the human spirit, doing something because they recognise it is greater than themselves.

    Regarding microwave, here is the way I see it. Microwave most certainly has tremendous potential for launching an interstellar probe and I would like to see both theoretical and experimental research pushed forward with this excellent propulsion scheme. That said, all of the studies I have seen to date have been for very small payloads. Take the excellent Starwisp concept of the late Robert Forward, this was a 1 ton craft, pushed by a 50,000 km circular lens located at Earth orbit having a mass of around 50,000 tons (interestingly, the same mass as the Daedalus propellant). It would be accelerated by a 10-50 GW microwave beam at around 115 g to reach 0.2c. Has anyone done any studies to scale this architecture up for a ‘human carrying mission’? Apart from the very high g levels for Starwisp (impossible for humans to withstand), the entire architecture looks just as big as for a nuclear pulse system, the way I see it.

    Consider this too, it is generally the consensus that by the time we as a civilization are ready to launch a probe to another star (say in one century from now), orbital or lunar based observational platforms will be so advanced and have such high resolution, that they will be able to image much of what is in the star system already. So, this raises the question, what ‘knowledge’ value can small mass probes add and tell us that we won’t already be able to determine using this long distance observational systems? How is this mission justified given its costs when you can get the same information from the deep space telescope? The only way it can be justified is if you can ascertain more science information (sufficiently significant to justify the effort and cost) which is over and above that obtained using the home observatories. This implies you need to go beyond flyby and use orbiters, atmospheric penetrators and even planetary landers. If you throw all those in, this increases the mass of your science probe beyond just the 1 ton of Starwisp. Daedalus had a payload of 450 tons, which arguably is way too high. So maybe you are looking at something like a 50 – 100 tons probe. So here then is an interesting question: how does the cost and architecture requirements compare for say a microwave beam system and a nuclear pulse system (e.g. fusion) with such a probe mass? Until these sorts of comparisons are performed, it would be wrong to rule out one technology option over another. You simply don’t have the data to support such arguments.

    Getting back to human crewed missions. I refer you to some papers published in the 1980s exploring nuclear pulse driven world ships:

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

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

    What similar studies have been done for non-nuclear pulse systems? I am aware of some sail studies done by Greg Matloff, which I also reference here for the readers:

    Matloff, G.L, On the Potential Performance of Non-Nuclear Interstellar Arks, JBIS, 38, 3, pp.113-119, March 1985.

    Matloff, G.L & C.B.Ubell, Worldships: Prospects for Non-Nuclear Propulsion and Power Sources, JBIS, 38, 6, pp.253-261, June 1985.

    Matloff, G.L & E.Mallove, Non-Nuclear Interstellar Flight: Application of Planetary Gravitational Assists, JBIS, 38, 3, pp.133-136, March 1985.

    Again, until they are done for all the claimed ‘interstellar propulsion candidates’, with both (plausible) robotic and (plausible) human crewed missions, ruling one technology out over another is premature.

    It is my personal belief that beam/light driven systems may be best for a few tons or less, but for the launch of a larger 10′s tons nuclear pulse will be optimum. For human crewed missions along the lines of a world ships, slow boats or other such concepts, I would like to be presented with some evidence that any other alternatives can compete with nuclear fusion and nuclear pulse (excepting more exotic options like antimatter and FTL). I would be glad for some references to read to clarify my view here if I am not familiar with some good studies that have been done along these lines, as I always remain open to changing my views. Please provide some example studies.

    Dear Ric, I completely agree with your sentiment regarding merging like-minded interstellar organizations. Working together co-operatively, gives us the maximum chance of succeeding in our mission. What prevents this and is also an explanation for why several interstellar organizations are now springing up is ‘human emotions’. Human emotions drive us from rational decision making, force us to defend our point of view, with such a strength of feeling that it gets in the way of co-operation. We see some of this strength of feeling expressed frequently in many blog comments of this most excellent Centauri Dreams web site. Somehow, we need to get away from that, raise above it, and focus on the science we are trying to achieve. Sir Arthur C. Clarke once said: “politics and economics are concerned with power and wealth, neither of which should be the primary, still less the exclusive, concern of full-grown men”. I see too much of this, in our wondrous subject. One of my collegues called it ‘space addiction’, which goes to your head as you are more convinced that “your way is the right way” and everyone else is obviously not very bright for dissagreeing with you. When this happens in our community, it should be like a red siren going off saying “warning! entrenched non-moving view point”.

    I leave you with a final thought. In the 1920s and 1930s, many space organizations were springing up across the world. The vfr in Germany, The American Interplanetary Society, The British Interplanetary Society and many others. This was a few decades before the real space age began in 1957 with Sputnik 1 an 1969 with the first Moon landing. Are we witnessing a similar phenomenon today, with the emergence of space tourism, commercial space flight and now interstellar societies? I suspect we are at another inflection point in the future history of our species. My only hope, is that rational human thinking sends us along the right trajectory and sees the interstellar vision fulfilled.

    As the Tau Zero President is fond of saying “we must be impartial, objective and follow the numbers”, to paraphrase him. I agree with this, but first we need to ensure we have the numbers to follow – this means we need reliable studies across the spectrum of options and only when that is done can anyone claim with authority that a front runner exists. Until then, we must pursue all the options, without exception.

    Kelvin F. Long

  • Greg August 13, 2012, 14:03

    “engineering EM way back in college”

    That seems after my time our EE program never offered any type of quantum electrodynamics, a few years later I did encounter it going for my Physics, just briefly. I’ll refer to the article and why it may or may not of use,

    “But it is not insignificant. At a separation of 10nm, the force is equivalent to 1 atmosphere (although the actual force depends on various factors such as the precise shape of the objects in close proximity). ”

    “That makes the Casimir energy huge. Zhao and Miao calculate that in a lab at 300K (room temperature), the Casimir energy would be some 10^11 times bigger than the free space value.”

    True it has bold claims but whats needed is the experts to give it an objective review and determine if this is a valid path or not.

    I view that while interstellar propulsion methodologies need to be firmly grounded in physics, it still needs a foot in the ‘fringe’ if it is ever going to be worthwhile.

  • Brett Bellmore August 13, 2012, 19:22

    Greg: Force integrated through distance equals energy. At a separation of 10 nm, the force is equivalent to 1 atmosphere, but at a separation of 10nm, two surfaces are only a few nanometers away from contacting each other. The force gets integrated over a truly minute distance, and so it really isn’t a huge amount of energy. Which is why Reynolds Wrap factories don’t blow up from the released energy as the separation between the foil they’re winding goes to effectively zero.

    Metamaterials can produce some really amazing effects, but they do so with the energy already inherent in their construction. By the time you got two surfaces separated by metamaterial down to ten nanometers apart, the metamaterial would cease being meta for lack of any space to contain the structural complexities such materials rely upon.

    Casimir effects may yet contribute to interstellar travel: Manipulation of them seems critical to getting molecular nanotechnology working, and nanotechnology would allow us to become a K2 civilization, with the energy resources to engage in interstellar travel. But they won’t contribute by pulling energy out of empty space, of that I am fairly confident.

  • Greg August 14, 2012, 8:56

    Brett, yes I understand how the Casimir effect works on the nanometer level, thanks. Whats needed is to have the experts tell us if the theory is worth further analysis.

  • Ron S August 14, 2012, 13:09

    “Whats needed is to have the experts tell us if the theory is worth further analysis.”

    Talk to an expert and you will almost certainly get the opposite response, for good reason. Will you reject them just as you’ve rejected Brett’s expertise?

  • Eniac August 15, 2012, 22:45

    I agree with Ron. This is one of these issues that any expert would say “forget about it”, but they have gotten sick of saying it over and over again to people who will not listen anyway. That’s why you find this issue discussed only among non- or would-be experts, together with all the other nonsense in this category, most prominently “free energy” and “antigravity”.

  • David McCarroll August 19, 2012, 8:02

    interesting reply by “Astronist” (Stephen, from oxford) regarding the current antipathy towards expenditure on space exploration, maybe those who want to pursue this avenue of research (of which I Am definitely one!) need to take the same response that all other entities with a barrow to push do, and find the positive spin on what we could do.

    There is never enough press, or promotion given to just what the US space missions have produced for humanity as spinoffs – for example, this laptop I am writing on here could be viewed as a direct child of the technological advances brought by space mission research…..

    Likewise, regardless of whether opponents believe that we, as a species should be devoting every resource to stopping people from starving (thus sadly making human overpopulation even more of a pressing problem), or providing fresh water, or literacy for all, one thing almost all people agree on is that the destruction we have wrought upon our planet’s fragile ecology is devastating and probably close to reaching a point of no hope in terms of ever righting the mess we have made of our home.

    SO. One of the enormous benefits I see in getting off planet Earth, and looking elsewhere for the energy and resources we require, is that the sooner we do so, the sooner we MIGHT be able to devote resources to returning Earth to a sort of “Eden” where the damage we have done can be reversed, or at least halted, giving us all the chance to redeem ourselves in the face of mother nature.

    This reason alone I suspect would be enough to get an awful lot of people at least looking positively at what Interstellar, or at least deep solar travel might do to benefit us all.

    Any takers?

    David McCarroll
    Sydney, Australia