All Astronautical Evolution posts in 2012:
Growth Options (1) (Feb.)
New in 2015:
Short story The Marchioness
2016: Stragegic goal for manned spaceflight…
2015: The Pluto Controversy, Mars, SETI…
2014: Skylon, the Great Space Debate, exponential growth, the Fermi “paradox”…
2013: Manned spaceflight, sustainability, the Singularity, Voyager 1, philosophy, ET…
2012: Bulgakov vs. Clarke, starships, the Doomsday Argument…
2011: Manned spaceflight, evolution, worldships, battle for the future…
2010: Views on progress, the Great Sociology Dust-Up…
Index to essays – including:
The Great Sociology Debate (2011)
Building Selenopolis (2008)
|(1) Starships and Future Scenarios|
|(2) Alan Bond speaks at Farnborough|
|(3) Rand Simberg on Neil Armstrong|
All content is by Stephen Ashworth, Oxford, UK,
unless attributed to a different signed author.
(1) Starships and Future Scenarios
Note: an extensive debate on the way forward for interstellar groups is currently under way at Centauri Dreams. The following essay was written in response to the announcement of the 100YSS organisation earlier this year.
The Challenge of the Starship
The objective of the 100 Year Starship (100YSS) organisation is to “make the capability of human travel beyond our solar system to another star a reality over the next 100 years” (Mae Jemison, leader of the project on the 100YSS website). It will “dedicate itself to identifying and pushing the radical leaps in knowledge and technology needed to achieve interstellar flight while pioneering and transforming breakthrough applications to enhance the quality of life on earth.”
But technologies for interstellar flight as such are not enough. In the present-day climate of widespread pessimism about the future prospects for industrial civilisation itself, the 100YSS and similar organisations need to focus in the first place on the prior social and economic developments necessary before interstellar flight can become a reality. Relevant technology developments will then emerge from that broader pattern of growth of civilisation in a natural way, but, more importantly, they will be prioritised correctly for maximum effect.
Interstellar flight, particularly with people on board, has two fundamental requirements which are way beyond the current state of the art: enormous energy for propulsion, and accommodation for indefinitely sustainable human life in space.
Suppose that a completely self-contained starship for say between 20 and 50 people can be built within a hardware mass of 10,000 tonnes, the size of a small ocean liner, containing everything they need for sustaining themselves and exploring at their destination, with or without artificial hibernation along the way. Suppose that it can accelerate within a couple of years to a cruising speed of 4.4% of the speed of light, or 13,200 km/s, and decelerate back to zero at its destination. Such a ship could then reach the very nearest interstellar destination, Alpha Centauri, in a century of flight.
The energy it would consume for acceleration and deceleration on the one-way journey, if its engine converted the energy it generated into kinetic energy of the vehicle with the maximum possible rocket efficiency, would be 5.4 x 1021 J, equivalent to about ten years of humankind’s entire current global annual industrial energy production (assumes mass ratio of 4.9, exhaust velocity 16,600 km/s, same engine used for acceleration and deceleration).
Doubling the mass would double the starship’s energy consumption; doubling its cruising speed in order to halve the journey time would quadruple its energy consumption. Using a less efficient propulsion system, such as a rocket operated at a high mass ratio or beamed power, would increase the energy demand proportionately. This is what we mean when we refer to “enormous” energy requirements.
The crew and passengers on such a ship would spend most of their lives – and more plausibly their entire lives for multiple generations – on board. When the starship arrives at its destination it will not find a duplicate of Earth which the interstellar travellers can immediately occupy, with liquid surface water, a breathable atmosphere and edible local plant life. Such Earth-analogue worlds may exist, but it is clear at this point that the majority of stars will not possess one, and therefore the majority of starship voyages – including the first – will not end at one.
The interstellar travellers will therefore need to construct, in space or near-space conditions (low gravity, high radiation, near vacuum), new permanent accommodation after arrival from local resources consisting of asteroidal materials and occasional Moon-like or Mars-like worlds. This is what we mean when we speak of “indefinitely sustainable” human life in space.
The vision of a manned starship hopping in a few weeks or even a few years from one Earth-analogue world to another is pure Star Trek fantasy. It does not correspond to the actual engineering or astronomical realities of real-world interstellar flight.
Growing into the Solar System
If manned interstellar flights are one day to take place, then civilisation needs to grow significantly in the following ways:
Note that such growth demands that the current trends towards global development and international peace continue; large-scale poverty and war between great powers are a waste of human potential and creativity, and are incompatible with the vision of a spacefaring future. The synthesis of peaceful growth and space was emphasised by Gerard K. O’Neill in his classic book The High Frontier. The starship requires peaceful global development, and the extension of this post-militarised, post-poverty lifestyle out into the Solar System.
Clearly, this point of view has an uneasy relationship with that of socialist groups which, under the banner “Keep space for peace”, nevertheless focus almost exclusively on military activities in space and have little in the way of a positive vision of space development to offer.
One sometimes sees comments to the effect that the problem with the British Interplanetary Society’s 1970s Daedalus interstellar probe study was that it presupposed a Solar System-scale economy in order to obtain its fuel supply (mining helium-3 from Jupiter’s atmosphere), and it would be preferable if a starprobe or even a manned starship could be launched using Earth’s resources alone.
This, however, would be to put the cart before the horse. To paraphrase Robert Zubrin (in The Case for Mars): we do not wish to fly to another star just in order to set a new aviation altitude record for the Guinness Book of Records, nor because we want to repeat Apollo on a far grander scale: planting the flag, collecting some rock samples and flying home again.
The only purpose of manned interstellar flight that makes sense, given the extreme remoteness of the stars, is to set up a new self-sustaining branch of civilisation in the destination planetary system. But in order to do that we must necessarily first do so in our own planetary system, using similar kinds of resources. Otherwise the only guarantee is that an attempted extrasolar colonisation will fail.
However, while a small interstellar probe may be launched from Earth using Earth’s resources alone, a manned starship of any realistic size and speed (such as outlined above) would require an economic base in terms of annual energy consumption at least two orders of magnitude greater than that of the entire present-day industrial Earth (thus siphoning off 1% of global energy production over a decade-long fuelling programme). This might possibly be achieved with large-scale ocean surface colonisation and terrestrial solar power.
But I would argue that such a vehicle would be too small to contain a complete microcosm of industrial civilisation and a functional human society. Absent some magical technology which can compress an interstellar journey down to less than a few years of flight time, and do so at affordable cost, we are inevitably looking at a worldship. I would argue that a vehicle, or small fleet of vehicles travelling in convoy, two orders of magnitude larger (one million tonnes zero-propellant mass, carrying a few thousand people) should be regarded as the minimum practical size, raising the energy cost to one thousand years worth of current global consumption, and the dollar cost in proportion.
If in addition the starship/worldship is to have a realistic level of reliability, it needs to build upon prior space experience amounting to at least several human generations living in progressively greater isolation from the home planet. So the Solar System-scale economy is in fact unavoidable, in addition to being itself an intrinsic goal of the starship programme.
Once the necessary building-blocks of that economy have been mastered, capabilities will have been developed for:
All three of these are essential precursors for manned interstellar flight.
The only interstellar capability which is not developed naturally during the course of Solar System colonisation is propulsion, because the speeds and energy levels required for flight to even the nearest stars are not necessary within the Solar System, where distances are four to five orders of magnitude smaller. The temptation is therefore to focus on propulsion and to sideline sustainable human life in space and mining and manufacturing with space resources, but without the latter, the best propulsion in the universe would be useless: you may arrive at your destination, but you will not be able to survive there for long, let alone grow.
Meanwhile, controlled nuclear fusion is highly desirable to power any human settlement beyond the Asteroid Belt, and achieving this long-sought goal would at least produce technologies relevant to developing fusion-based rocket propulsion for interstellar flight.
The Starship and the Rest of Society – Optimism versus Doom and Gloom
It would be easy for the 100YSS and similar organisations to cut themselves off from the rest of society and immerse themselves in their own esoteric intellectual world of warp drives and interstellar trekking. To its credit, the 100YSS website stresses the benefits of space technologies to Earth: GPS, remote sensing from orbit, weather satellites and so on. Yet the vision presented is not exactly transformative: Earth benefits from spin-offs, and meanwhile “Programs to establish a human presence on the moon, Mars, or elsewhere in our solar system will be stepping-stones to the stars.”
In my view, this vision is much too coy about the true meaning of space. We should not be talking about spin-offs such as medical instruments, pagers and beepers, but about the potential of space colonisation to expand the human population, economy and resource base by orders of magnitude, a transformative prospect which does not exactly leap out of the term “a human presence” on the Moon or elsewhere.
One of the critical controversies of our age is whether the growth of industrial civilisation – the fundamental driving force of our society – is sustainable in the long term, and space provides the answer: we have centuries of dynamic growth ahead of us which will utterly transform society in every way, provided that we can manage the trick of transferring the focus of material and population growth away from Earth and into space.
If large-scale economically sustainable Solar System colonisation takes place, then manned starship construction will be a natural outcome; if it does not take place, then any programme of starship construction which may be embarked upon will be politically or economically unsustainable and subject to cancellation, with individual flights at high risk of failure. The Mayflower model versus the Apollo model.
Given the current widespread pessimism about the future of civilisation even on Earth, let alone beyond it, the 100YSS organisation needs to engage with widespread popular fears such as:
Actions based on these fears are incompatible with any future human starship-building scenario. Interstellar groups need to challenge these fears head on and refute them, using the manned starship as the ultimate symbol of the growth and progress of human civilisation, the ultimate demonstration of our creative power and vindication of our existence.
Is Civilisation about to be Engulfed by the Perfect Storm,
or is it on Course for a Future so Bright you Gotta Wear Shades?
In their research and public pronouncements, interstellar organisations need above all to present a coherent, balanced and persuasive future scenario or narrative which explains the transformative power of growth into space, while avoiding simplistic clichés and recognising the many other areas of human endeavour which will contribute to a progressive future. It may include points such as the following:
These arguments need to be made, otherwise the starship will be seen as a frivolity and an irrelevance to that large fraction of society which believes in at best a retreat from industrial society, and at worst the collapse of that society.
Future scenarios tend to be polarised between the “perfect storm” vision of multiple stresses conspiring together to trigger a global crisis, and the “future’s so bright I gotta wear shades” vision (quoted here) of mutually reinforcing improvements in technologies, education and economic development delivering worry-free prosperity for all – argued also in the new book Abundance by Peter Diamandis and Steven Kotler.
What tends to be missing is a balanced assessment: yes, the world will grow richer through new technologies, but at the same time it will surely experience new stresses. If we assess the human future in the light of past experience, the lesson seems to be: there have always been serious problems, history has stumbled from crisis to crisis, but in spite of them the quality of life does continue to improve for increasing numbers of people, and a human civilisation peaceful and wealthy enough to afford an interplanetary and ultimately an interstellar future is a realistic prospect.
Not because it will solve all our problems, but because it will on balance open up more creative avenues than destructive ones.
(2) Alan Bond speaks at Farnborough
Alan Bond has given a good summary of progress so far on the Skylon project at Farnborough. Watch it on YouTube.
(3) Rand Simberg on Neil Armstrong
Neil Armstrong was the undisputed hero of the first space age. But time is moving on, and the second space age is already beginning.
In my view, one of the best comments on Armstrong’s passing comes from Rand Simberg. He gives full recognition to Armstrong’s unique personal qualities and experience, while noting also that the fact that he showed us the way to the Moon does not mean that an Apollo-Saturn type of system is the way we should be doing it now.