There is an extensive literature, both technological speculation and science fiction, concerning the future of human activities in space. Part of this literature concerns future solar system activities such as exploitation of the energy, raw materials and living space that are potentially of great value to humanity. Many promising concepts have been produced, such as solar sails, asteroid mining, mobile suits and space colonies, which may play major roles in the future. However, to date these ideas remain fictional; solar system resources remain untapped; and there is no agreed scenario within the space industry that leads from the present to human expansion through the solar system.

From a business point of view, in order to believe that such ideas are realistic, it is necessary to be able to foresee projects that will be commercially feasible; that is, projects in which the expected profits more than compensate for the costs and risks that must be incurred initially. Today a number of space industry activities involving generation and transmission of information are commercially profitable. However, these do not require the development of low-cost launch vehicles; they do not require human activities in space; and do not offer a route to accessing solar system resources.

Perhaps the best medium-term space business prospect that has been identified so far is the satellite power station ( SPS) proposal to collect solar energy on a large scale in Earth orbit and transmit it to Eafth as microwave beams for conversion to electricity. Electricity supply is one of the largest and most stable markets in the global economic system, and the SPS project therefore offers the space industry the possibility of earning stable commercial revenues from sales of electric power up to one hundred times those for telecommunications today.

An important side-effect of the development of SPS would be to create a demand in high Earth orbits for millions of tons of materials such as aluminium, silicon, oxygen, glass, titanium and iron. Most importantly, at the launch cost of $100/kg (13000¯/kg) which is necessary for the SPS to be profitable, the market price for basic materials such as these will be of the order of $100,000/Ton (1300 man\235/Ton) in LEO and $500,000/Ton (6500 man¯/Ton) in GEO.

Launch and transportation costs from the Moon to GEO have the potential to be much lower than this, due to the lower escape velocity and the possibility of electric-powered launch. Consequently, at a ceftain stage in the SPS project, the commercial demand for materials in orbit for SPS construction at this price will stimulate businesses to develop the technologies required to extract these materials from the lunar surface and process them in orbit, on a commercial basis. Once the necessary technology had been developed, other space resources could subsequently be used such as comets and asteroids.

No other project has been proposed to date that would provide a profitable route to tapping the solar system's resources in this way. Yet access to such resources may come to have increasing economic and political value in the future as the world faces serious global problems, and many raw material resources lie in less-developed countries.

Because of the ever-increasing demand for energy among most of the world's population, and the economic, political and environmental problems that face coal, oil and nuclear power, the SPS may become critically important. However, a total investment of several $ billions (several thousand oku¯) will be required to realize the SPS project, and the commercial prospects are currently too uncertain to justify such investment by electricity supply companies. Hence the SPS is not an immediate commercial prospect. There is a "missing link" between the present and the future of large scale commercial space activities.

In order to achieve launch costs as low as $100/kg (13000¯/kg), fully reusable launch vehicles (frlv) are required. However, it is not clear what payloads such vehicles should be designed to launch, since a frlv would not be a profitable development without sufficient traffic to amortize the investment and to lower construction and operating costs through repetition.

It has been proposed that, unlike the demand for communication satellites, the demand for passenger flights to orbit may have the potential to expand by several orders of magnitude as costs fall (1). It is hypothesized that as the cost of passenger space travel falls from some $75 m (100 oku¯) per person today, demand from governments will increase significantly; that as the price falls below $1 m (1.3 oku¯) commercial companies will find it profitable to establish facilities in orbit; and that as the price continues to fall, individual passenger flights will become popular (see Figure 1). For a business analysis the key questions are how much the demand would grow as the price of launch falls, and how far costs could fall as traffic increased.

It is important to note that sometimes even the best market research amounts to little more than what might strictly be called opinion or hearsay. A scientist could argue correctly that such evidence does not constitute proof, but it may nevertheless be of commercial value because it could provide grounds for estimating the probability of success of a project. In the case of passenger space transportation 1) there is a plausible logical case that it would be popular; 2) anecdotal evidence suggests that there would be vigorous market demand; and 3) the little quantitative evidence that exists is encouraging.

1. From a marketing point of view, space flight has a unique aura of excitement in the popular imagination, and this is largely justified, for orbital facilities could offer a range of entertainments which cannot be provided on Earth. For example, everyone who has visited space speaks movingly of seeing the planet Earth against the background of space, and it seems reasonable that more people should wish to have this experience.

   Those who have visited space also testify that learning to move around in zero gravity is highly entertaining. Even more, in large rooms a range of novel sports activities will be possible. In view of these ideas, it seems likely that if suitable facilities were available, there would be large popular demand for short visits to orbit.

2. There is much anecdotal evidence for believing that space tourism will be popular:

   • Everyone who has been into space agrees that the experience of space flight is fascinating. Astronauts and cosmonauts have spent hours looking out of their spacecraft windows. The first American woman to visit space, Sally Ride, said that it was the greatest fun of her life.

   • The American Express company in Britain found in 1985 that over half the population would like a holiday in space.

   • The Thomas Cook travel company and many airlines have received thousands of letters from people asking about the availability of trips to space.

   • The US National Commission on Space reported in 1986 "...a frequent desire expressed by the public - to personally participate in the future of the space program". It requires little imagination to understand what this means.

   • Popular culture tells the same story. The exceptionally durable success of such video productions as "Uchuusen Yamato", "Star Trek" and " Gundam" is testimony to the unique popular appeal of space. In his history of aviation in the USA, Roger Bilstein discusses the popularity of several American space-based fictions because this phenomenon is so striking. But these are only part of the much larger field of science fiction, of which a large part is devoted to space travel, much of it involving serious attempts at realism.

   Thus many millions of the general public take a strong, lifelong and detailed interest in realistic fictions set among people living in space. Yet they have to date been entirely excluded from space travel. It is perhaps not too extreme to say that in future the path that the space industry has taken over the past twenty years will come to be seen as an aberration from what would normally be expected in democratic capitalist societies.

3. There is also some quantitative evidence as to the prices that people will pay for visits to space.

   • At the request of customers, the adventure travel company Society Expeditions developed " Project Space Voyage" in 1985, offering short orbital flights, and received several hundred deposits of $5,000 (65 man¯) for their offer of passenger space trips at $50,000 (650 man¯) per person in the Phoenix launch vehicle (2). (The deposits were subsequently returned because at that time US investors considered the business case for single stage to orbit ( SSTO) launch vehicles insufficiently attractive.)

   • In December 1990 the world's first fare-paying passenger, Toyohiro Akiyama, a journalist from Tokyo Broadcasting System, went into space. His company paid some $11 million (14 oku¯) to the Soviet Union to spend a week at their orbiting station MIR, and earned revenues through sponsorship and related promotional activities. It is interesting to note how similar this Japanese project was to the commercial sponsorship that paid for many pioneering flights in the early days of aviation, both in Japan and elsewhere. Such a historic event as Lindbergh's crossing of the Atlantic was financed by commercial sponsorship, and had a very important effect in generating demand for air travel.

   • In May 1991 a British woman, Helen Sharman, also visited MIR financed privately, though due to commercial mismanagement the project's underwriters paid most of the costs.

   Thus some commercial demand exists even at a price of several $ millions per flight. This would seem to be the very upper limit of the price, however. For example the American singer John Denver declined to pay $10 million (13 oku¯) for a visit to MIR in 1988. It therefore seems clear that there will be no commercial demand for flights on the space shuttle or the proposed Hermes vehicle, given their costs of some $75 million (100 oku¯) per person.

The demand for flights to orbit will undoubtedly increase as the price falls through $750,000 (1 oku¯) and then $75,000 (1,000 man¯). Society Expeditions estimated that demand would reach 100 passengers per year at a price of $500,000 (6,750 man¯); 5,000 passengers per year at $50,000 (650 man¯), and 30-40,000 passengers per year at a price of $25,000 (325 man¯) (3).

Beyond this, the only published figure is the author's 1986 speculation that at a price of $10,000 (130 man¯) demand would reach one million passengers per year (4), which has been quoted with approval (5, 6), and criticized only for being conservative. The fact that so little market research has been done on a service with such an apparently promising future is itself interesting, and indicative of the non-commercial behavior of the space industry.

The major reason for the slow progress towards passenger space travel is of course that the cost of space flight is extremely high today. This is primarily because launch costs are very high, but this is not because the technology necessitates it. Liquid-fuelled rocket engines were developed before jet engines because they are simpler. Rocket-powered German V2s first reached space nearly 50 years ago, a decade before transistors were invented. The Soviet Union orbited a satellite in 1957, effectively before the advent of computers, followed by a person in 1961. And the USA sent people to the Moon more than two decades ago in 1969, before microprocessors existed.

During the 1970s and 1980s technology has continued to advance rapidly in every field. Typical of this process is the fact that the cost of the miniature tape recorders and video cameras which the Apollo crews used in the 1960s have fallen by a factor of 10,000 times since then - from $1,000,000 (1.3 okuY) to just $100 (1.3 man¯). However, space flight has not benefitted from such cost reduction. Indeed it is more expensive in real terms to launch payloads today than it was a quarter of a century ago on the Saturn 5!

The main reason for this path of development is that to date launch vehicles have been developed like military systems as government projects, with inevitably different objectives from those of commercial companies. The effects of this process have been overlooked for too long in the case of the space industry. They have been particularly well described in relation to the competition that occurred in Britain in the 1930s between the (successful) commercially developed R1OO airship, and the (disastrous) government-developed RiOl (7).

It is perhaps worth noting two particularly striking examples of this divergence between commercial and political objectives. In order to launch the proposed US-international space station, the Soviet Energiya could be used at a probable cost of a few hundred $ mfllions (a few hundred oku¯) in total. Instead, for political reasons, the US government currently aims to spend several $ billions (several thousand oku¯), and to cut back other socially valuable expenditure including many space science programmes, in order to use their space shuttle which is much less suitable for the task.

An earlier example occurred in the 1960s. Having developed a range of effective launch vehicle technologies for the Apollo project, the commercial, or economically rational, approach would have been to develop a minimum-cost, fully-reusable derivative vehicle such as the Saturn Applications Single-Stage To Orbit ( SASSTO) proposed at that time (8). However, for various reasons this course was not politically attractive, with serious economic costs to the USA. Japan and Europe have now more or less caught up with US rocket technology of the 1960s, and their launch costs are much the same. (Note however that these countries' governments have similar tendencies: development of new vehicles like Hermes and Hope to be launched on expendable rockets apparently offer political benefits, but they will not reduce launch costs.)

The recent decision by the US Strategic Defence Initiative Office to fund development of a SASSTO-like vehicle is aimed at reducing launch costs by some 99% (9, 10), following the route proposed in the 1960s (8) and championed throughout the 1980s by Hudson (2). It is interesting to note that today the uncertainty concerning this project's political support appears to outweigh the technical uncertainty. If government funding does not continue, the project's continuation on a commercial basis would be very interesting. Justifying such commercial investment would depend, among other factors, on identifying suitably attractive markets for the proposed vehicle.

Ultimately the cost of flight to orbit in mature, fully reusable vehicles will be equal to the cost of the propellant multiplied by a small factor (11), as is the cost of air travel today. This gives a figure of a few $ thousand (some tens of manY) per person. However, the lessons of history suggest strongly that the oppoftunity that clearly exists to reduce launch costs radically will be fully exploited only when performed as a commercial project - that is by commercial companies using their own funds, with no objective other than to earn a profit by selling to commercial customers.

In addition to launch costs, there is also great potential for reduction in costs of all the hardware for use in space. These costs are strongly dependent on the cost of launch; when this falls, so will these other costs. A major reason for this is that it will become economic to carry out maintenance and repair on operating spacecraft. Their production costs will therefore tend towards the costs of other technology designed for extreme but accessible environments, such as underwater, which are far lower than space industry costs. An illuminating discussion of this subject concluded that this will result in a reduction in space industry costs by about 99% (12).

There are a number of other issues that must be resolved in order to develop a mature passenger space travel industry.

• The safety of space vehicles will have to approach that of aircraft. This will be a straight-forward matter once launch vehicles are fully reusable and can generate operating statistics in a meaningful way like other transpoft vehicles such as trains and aircraft.

• The threat from orbital debris must be removed. Many studies are already under way, including on the use of lasers to decelerate debris particles sufficiently to cause their orbits to decay. Such a proposal, which involves large and complex spacecraft, is impractical at today's launch costs of $10,000/kg (130 man¯/kg). However, it will become attractive at a launch cost of $100/kg (13000¯/kg).

• Space travel sickness must be overcome - and a range of promising medications and treatments are being researched. It is notable that the development of a space tourism industry does not require the resolution, or even the identification, of the medical problems of long-term space flight.

• A number of legal issues need to be resolved, such as liability for damage, orbital traffic control, and jurisdiction for civil crimes in space. It is interesting to note that even an international Treaty to enforce liability for damage caused by space debris would become feasible when launch costs are low.

In a vigorous capitalist economy, if passenger space travel is expected to become a profitable business, that is the only justification needed in order for it to come about. However, the development of a thriving passenger space travel business in the near future would have a number of impoftant societal benefits, both social and economic. These are inter-related and difficult to evaluate, but they are nevertheless real.

For those who have the opportunity to visit orbit, of course, it will be a popular experience, and the objective of greatly increasing the number of people who have this opportunity is a desirable and democratic one. It is one of the strengths of commercial competition that it seeks to expand markets. Following the rapid growth of air travel in recent years it is likely that passenger space travel would quickly become widely available, although for a long time it will remain a once-off experience for which people will have to save seriously.

This benefit will be wider than solely for those who visit orbit. The public has greatly enjoyed such space photographs as those taken by the Apollo astronauts and the Voyager spacecraft. The beginning of ordinary passenger travel to space, albeit only to low Earth orbit initially, will provide a decisive step beyond this, which will offer a new and inspiring goal for popular aspirations. In addition, of course, "travel broadens the mind," and space travel may help to give more people the "planetary consciousness" that is so needed if humans are to overcome the global problems of the next few critical decades. (Interestingly, in " Gundam", Japanese popular culture has generated the idea of "new type" consciousness to refer specifically to the psychologically beneficial effects of living in space.)

Beyond this, passenger space travel will start to open a genuine new frontier for humanity. The existence of a frontier provides a foundation for public optimism, and helps to create a popular mood that the future is open and promising, something which is of real if intangible social value. Is it too fanciful to see the surprising popularity in the technologically advanced countries of new and irrational religions as perhaps partly due to the conventional, but mistaken, view of the world as closed? A closed world system would be less able to overcome the ecological problems caused by increasing population and industrialization, and the vision of an entirely Earth-bound future lacks excitement and challenge.

But a frontier is not opened by sending a few government employees into a new territory; it happens when individuals and companies, using their own resources, establish economically viable, lasting operations there. A partnership between government and people is needed, but government must be a facilitator, and not try to play the role of activator, which it cannot do.

Another social benefit that can be anticipated will be educational. This arises from the "paradox" that as the world comes to depend increasingly on technology, there is a tendency for children in affluent countries to avoid studying the more difficult technical subjects in favour of easier, more fashionable subjects. Although this phenomenon is perhaps most advanced in Britain and the USA, it is becoming visible even in Japan which has hitherto been particularly successful in motivating people to study technology.

The prospect of space travel seems attractive to the public, and particularly to children. Yet in order to understand space flight children need to understand a wide range of subjects in engineering, physics, chemistry, biology and other scientific fields. Thus it can be anticipated that the development of a vigorous space travel industry could help to make modern technological education an interesting and natural process, rather than one that is seen as unnecessary and boring.

Inter-related with these social benefits will be a number of economic benefits. First, if passenger space travel is commercially profitable, it will of course have economic benefits by creating wealth. However, by promising to generate continually growing commercial traffic to orbit, passenger space travel offers something more that other space activities do not, namely to create launch operations on the scale needed to amortize fully reusable launch vehicle development costs and to reduce operating costs sharply.

Reduced launch costs would in turn render feasible other socially beneficial activities in space that are currently too expensive and too uncertain to justify commercial investment. Most importantly this includes the SPS project, which is not yet considered a serious energy supply candidate by electricity companies, mainly due to the high cost of launch today. But at a launch cost of $100/kg (13000 ¯/kg), the "SPS 2000" LEO demonstrator project (13, 14) would be almost competitive on a capital cost basis with Earth-based electricity generation systems (though not in delivered energy cost due to the inevitably low utilization).

Thus, creating the demand necessary to justify commercial, low-cost launch vehicle development will be an economically beneficial side-effect of passenger space travel. No other use of space has yet been proposed that offers a comparably realistic possibility of a commercial route to airline-type economies of scale in launch operations and costs.

A further socio-economic benefit that can be expected from the development of passenger space travel will be to provide commercial demand for some of the advanced technologies which have been developed primarily for military purposes. By providing an alternative outlet for these technological skills, the expansion of a commercial space travel industry will utilize capabilities now being released as the Cold War winds down. This should not be the objective of the activity; but countries with hitherto relatively large strategic defence burdens have the opportunity to take advantage of current geo-political changes in this way, if they are sufficiently flexible.

To obtain these many benefits would seem to justify taking up the challenge of developing a commercial passenger space travel industry, which seems a worthy goal for the end of the twentieth century.

The space industry suffers from very high launch costs. These were not critical while space activities were an arena for superpower competition. However, as this justification for government involvement in the space industry disappears, the industry's future depends on developing commercially self-supporting activities, which require much lower launch costs. Technically there are design approaches that offer the prospect of reducing launch costs sharply. However, in order to attract commercial investment it is also necessary to identify suitable markets in which demand for launches will grow rapidly as prices fall.

Passenger space travel appears to offer the possibility of launch traffic rates several orders of magnitude greater than today. It could therefore lead to launch costs as low as 1% of today's, which would make short visits to low Earth orbit commercially available to a large proportion of the population of developed nations, bringing a range of social benefits. Such low launch costs would also have the benefit of making a range of projects attractive that are not feasible today. Foremost among these is the satellite power station project to supply energy from space to Earth.

The consumer services market is different in many ways from the government and telecommunications markets that the space industry has supplied exclusively to date. Thus the initiation of commercial passenger space travel is a major challenge. However this development should be seen not as a threat to the space industry, but as an opportunity to evolve into a more normal commercial industry, independent of government, with a wide popular customer base, and with much wider horizons than today.

1. P Collins, 1991, "The coming space industry revolution and its potential global impact", Journal of Space Technology and Science Vol.6 No.2 pp 21-33
2. G Hudson, 1985, " Phoenix: a commercial, reusable, single-stage launch vehicle", IEEE EASCON 85 pp 151-163
3. Society Expeditions, 1985, " Space tourism could drive space development", Proc. L5 Space Development Conference
4. P Collins and D Ashford, 1988, "Potential economic implications of the development of space tourism", Acta Astronautica Vol 17 pp 421-431
5. G Woodcock, 1987, " Economics on the space frontier: can we afford it?", Space Studies Institute Update 13 No 3 pp 1-10
6. D Koelle, 1987, " Sanger: an advanced launcher system for Europe", 38th IAF Congress paper no. IAF-87-207
7. N Shute, 1954, " Slide rule: The autobiography of an engineer", Mandarin, London, pp 60-154, 1990 edition
8. P Bono, 1967, " The re-usable booster paradox - aircraft technology or operations?", Spaceflight No 9 pp 379-387
9. R Richardson, 1991, "Prospects for inexpensive space transportation", Proc. SPS 91 b6.1 pp 479-483
10. McDonnell Douglas, 1991, " Delta Clipper: a reusable single-stage-to-orbit-and-return space transportation system", McDonnell Douglas Space Systems Company, Huntington Beach, CA
11. T Gregory and H Wright, " National aero-spaceplane status and plans, Progress in space transportation", ESA SP-293 pp 149-156
12. W Haynes, 1988, " The issue is cost", Space Studies Institute Update Vol 13 No 2, pp 1-5
13. M Nagatomo and K Itoh, "An evolutionary satellite power system for international demonstration in developing countries", Proc. SPS 91 Power from Space Symposium B1.4 pp 356-363
14. P Collins, R Tomkins and M Nagatomo, 1991, "SPS 2000: a commercial SPS test-bed for electric utilities", Proc. IECEC