Many people would like to experience space travel for various reasons. Since the early days of science fiction in the 1930s, the image of space flight as adventurous and exciting has played a growing role in popular culture. Furthermore, those who have been lucky enough to visit space have all confirmed that it is a highly enjoyable experience. The view of Earth and the stars is spectacular, and the experience of living in "zero gravity" is fascinating. The first American woman to visit space, Sally Ride, said simply that it was the greatest fun of her life.

Of course the actual demand for flights to orbit, if these become commercially available, will depend both on their price and on the details of the "offering". Thus, in order to determine the commercial potential of space travel, research is required both on the technological possibilities of reusable passenger-carrying spacecraft and orbital accommodation, and on the economics of operating a commercial service, including market research.

Spacecraft engineering design is related to aircraft technology, as a result of which the term "aerospace industry" has been coined. However, the development of the space industry to date has been unlike the historical evolution of the aviation industry, notably in that the roles played by government and private industry have been different.

Although government departments, particularly the military services, played very important roles in the development of flight, governments did not establish monopoly organisations to perform aircraft flights "on behalf of the public". The fact that this occurred in the case of the space industry, initially in the USA and subsequently in Europe, Japan and elsewhere, can be seen as a result of the Cold War, and in particular of the challenge of Sputnik and Yuri Gagarin's orbital flight, which stimulated the USA to respond in kind by performing government-sponsored "space projects".

Although aviation research centres were established in many countries, these did not generally have manpower as great as or greater than the companies to which they gave contracts. The USA's Apollo Project was a unique Cold War project which created a widespread popular perception that space activities should be performed by central government organisations. This idea was apparently widely accepted for several decades in the USA, although it is contrary to that country's fundamental ideology. This acceptance was perhaps partly due to the unique aura of space and to the rhetoric of the government-funded space industry which has long claimed that they are "opening the space frontier for humankind".

Nevil Shute, the chief engineer on the very successful British "R100" commercial airship project in the 1920s, described particularly clearly some of the disadvantages of government carrying out advanced technology vehicle development projects (1). The "R101" was a parallel government project with much greater funding than the R100. Not only was the R101's performance very poor, but it crashed disastrously, killing nearly everyone on board. The British government then scrapped the R100, in a further non-commercial decision rather similar to the US government's later decision to scrap the Saturn 5 rocket and Apollo project hardware.

The recent evolution of the US/international space station project is an interesting case in point. Proposed initially to provide scientific research facilities in orbit, the project was of considerable interest to wide sectors of the engineering and scientific communities. However, as the cost mounted progressively to many times the cost of the 1970s Skylab project, and as the legal regime covering operations on board became progressively more complex, almost every scientific and engineering group has withdrawn their support. The current proposal is that the station will provide facilities for the agencies which build it, which is a travesty of the original purpose, and is not surprisingly of limited interest to the politicians who must justify such large expenditure to the public.

Government organisations' objectives and modes of operation are necessarily different from those of private comanies. It might be said that whereas companies are entrepreneurial, government organisations are "procedural", since they must be able to show to the public that their actions are in accordance with established rules. For this reason there are certain things that governments cannot do effectively. Commercial innovation is one of these, and this is required in full measure in order to develop popular space travel.

This difference can perhaps be further illustrated by considering what might be the result if the head of a national air force were asked what it would cost to provide tourist flights to a certain destination. Because they operate a variety of different aircraft it might be thought that an air force could do this. But the way in which an air force operates is completely different from that of a commercial air travel company, and so their estimates would have almost no relation to the actual costs of a commercial company.

Although commercial space travel is not an appropriate activity for government organisations, helping the private sector in various ways to develop the capabilities necessary to create a new and profitable industry is one of the traditional roles of government in every advanced country. In particular, governments in many countries played a major role over several decades in the development of aviation into a commercial industry, and they continue to do so, both directly and indirectly.

Consequently, determining the correct roles for government and private organisations in the development of this field will be very important to its success (2), and may be of considerable economic significance if the commercial space travel industry grows as has been suggested (3). 1992, International Space Year, was the 35th year of the space industry (measured from the first satellite launch in 1957), which is half the traditional western life-span of "three score years and ten". Thus 1993, the start of the "second half", is perhaps an appropriate date for starting a new approach to space development.

With the end of the cold war forcing the restructuring of the aerospace industry it might be said that we are seeing the beginning of "perestroika in the space industry". Over the decades of the cold war the aerospace industry has developed astonishing technological capabilities. It would be of potentially enormous economic benefit if this could be channelled into commercially valuable activities, rather than allowed to go to waste.

One sign of "perestroika" in the space industry is the recently announced joint venture by Lockheed and Krunichev to market the low-cost Proton launch vehicle. Although western governments are trying to protect the markets for their higher-cost launch vehicles, this development should put pressure on western makers of high-cost expendable rockets to consider developing low-cost reusable vehicles.

Another sign that the space industry is at last beginning to live up to aviation's example was the 1990 flight of Tokyo Broadcasting Service (TBS) journalist, Akiyaka Toyohiro, to the orbiting space station, MIR. This achieved a significant place in the history of humans' expansion into space. As well as being the first Japanese, and the first journalist to visit space, Akiyama-san's flight was the first commercial space flight by someone outside the space industry. His flight was also strikingly similar to the many pioneering flights in the early days of aviation sponsored by newspaper companies, primarily for the purposes of publicity.

As an example, the Mainichi Shimbun company (which today is the parent company of TBS) and the Asahi Shimbun company competed continuously through the 1920s and 30s, sponsoring international competitions, such as for the first flight across the Pacific ocean, and long distance flights. For example the 1937 flight of the "Kamikaze-go" from Tokyo to London was sponsored by the Asahi Shimbun company, while in 1939 the "Nippon-go" made an eastward flight around the world, visiting 30 countries, sponsored by the Mainichi Shimbun. These and similar flights, such as Lindbergh's transatlantic flight, that led to the "Lindbergh boom" in US domestic aviation, played a major role in popularizing passenger flight, by demonstrating that aviation technology was mature enough to provide safe passenger operations.

The second such commercial space flight project, the flight of the British Helen Sharman to MIR in 1991, was similar in principle to Akiyama-san's flight, except that it was commercially unsuccessful, leading to a substantial loss on the part of the sponsors. But this is also part of business; investments can lead to losses as well as to profits. After the recent "bubble economy" many companies in Japan are facing unprecedented losses caused by misdirected investment. A small fraction of these losses would be sufficient to pay for the development of a space tourism business.

As and when reusable commercial passenger-carrying launch vehicles are developed, they will surely receive a high level of publicity. For this reason they will be very good vehicles for commercial publicity, and it seems probable that there will be many sponsored space flights emulating the early days of commercial flight. Such a pattern of development in the space industry could well have similar benefits for the industry's commercialisation.

However, the development of reusable launch vehicles, which is needed both to reduce launch costs and to increase their reliability to the level of aircraft, faces a problem of commercial justification. The present day launch market is very small; a few tens of satellites per year. Consequently a single reusable launch vehicle that could fly even once per week, would be able to launch all of these (although due to political interference in the market, this would be unlikely). Unfortunately there is no good prospect that the demand for satellites will grow very much as the price of launch falls. Indeed, such markets as telecommunications and broadcasting seem likely to shrink under competition from more cost-effective terrestrial systems such as optical fiber cables and cellular telephone networks.

Consequently in order to be able to recover the development costs of reusable launch vehicles, the space industry needs a new, much larger market, that would require tens of launches per day. If commercial space travel could become popular enough to reach a scale of the order of one million passengers per year, it could pay for the development of low cost launch vehicles.

Table 1 illustrates the powerful effect of accessing such a large market; the development of such a vehicle might be amortized commercially. To reach this market is the key challenge for the space industry today. If it can reduce costs sufficiently, the industry can grow very large, with such important projects as satellite power stations ( SPS) providing environmentally clean electric power on a global scale. This will be the real "space age".

On the demand side, we know from modern popular culture that space travel is a popular idea in many countries (4). For example, in recent years some of the most popular video series and films such as Space Battleship Yamato, Star Wars, Mobile Suit Gundam and Star Trek are based in space. Consequently, if space travel was available at the same cost as air travel, it would certainly become a very large market - many tens of millions of customers per year (which is still only a few percent of air travel). However, we also know that flight to orbit will be more expensive than air travel, because the fuel needed to accelerate a person to Mach 25 is approximately that required to transport them around the world. Thus space travel will be a relatively expensive service, and if it is to become widely popular, it will probably be as a "once in a lifetime" experience for many customers, a unique modern equivalent of a "journey to Mecca" in an earlier age.

Although one million passengers per year would be very large for the space industry, it is quite small by comparison with modern aviation. However, in order to reach this scale, the cost must be low - less than 2,000,000 Yen per person or 20,000 Yen / kg, about 1% of the cost of launch using present-day expendable rockets.

In order to reduce costs to the required extent, we must start to get experience of reusable commercial launch vehicle operations as soon as possible. The only such project currently under way is the McDonnell Douglas DC-X / DC-Y / Delta Clipper project, though a vehicle more like the Pacific American Phoenix would seem more appropriate for passenger travel (5).

It is not uncommon for members of companies building expendable rockets to state that VTOVL SSTO rockets are impossible, but their feasibility has been demonstrated incontrovertibly by Hudson (5)(Appendix). The only interesting question is how much it would cost, and how much mass is required, to make an SSTO vehicle fully reusable. In this context it is interesting that, despite government funding of some hundreds of $ billions to date, the space industry has not yet tried to do this in any country.

Cost reduction is one of the continual driving forces in commercial industry, since every reduction in cost is a direct addition to profit, and reducing prices below those of competitors is one of the major forms of commercial competition. However, the possible cost of passenger space travel is controversial, with published estimates ranging from $400,000 in 2012 (6); $60,000 in the year 2050 (7); to $10,000 in the 2000s (8). An experienced figure such as Ruppe doubts whether low-cost launch is possible.

However, if the space industry does not succeed in reducing launch costs low enough, then space travel will not become a significant business, and the space industry will probably continue as a small-scale, high-cost activity of government researchers. In that case, space will not be a "new frontier" for humans.

The DC-X project budget is some $60 million, or less than 0.05% of NASA's annual budget. This shows a lack of interest by US politicians, but it is also perhaps a sign that much can be achieved at relatively low cost. Once reusable launch vehicles are in commercial operation, operating companies will learn continually about improving their operation and reducing costs. When the space industry reaches this stage, the early history of aviation will have many interesting lessons for its further commercial development.

An interesting aspect of the future development of commercial travel to low Earth orbit is the relation between the cost of flights to and from orbit, and the cost of staying at an orbiting "hotel". At a target price of some 20,000 Yen per kilogram to low Earth orbit, a passenger flight would cost some 2,000,000 Yen. At this price the launch of an orbital hotel weighing some hundreds of tons would cost some tens of billions of Yen. If the demand for trips to orbit was of the order of 1 million passengers per year, and if passengers were to stay in orbit for 2 or 3 days, there would be a demand for accommodation for between 5,000 and 10,000 people in orbit. This scale would certainly provide manufacturers the opportunity to obtain significant scale economies through mass production of accommodation units.

It is worth noting that a "space hotel" would be much easier to design and build than the US/international space station. As an illustration of this, accommodation made from several units of the Skylab space station from the early 1970s, excluding the scientific equipment but including more windows and comfortable fittings, would be satisfactory for an initial hotel. It is difficult to believe that each unit would cost more than a few billion Yen, about the price of a business jet, which is a much more complex vehicle.

The total cost of such a hotel, including launch, should therefore be a few tens of billions of Yen, which is comparable to that of a modern office building. If we assume that such a hotel should earn annual revenues of 10% of its cost, or some billions of Yen per year, then if it accommodated some thousands of passengers in a year, the cost of a few days' stay would be of the order of 1,000,000 Yen, or some 50% of the cost of a passenger flight to orbit. It will be interesting to see whether more detailed future cost estimates support this approximation. If so, then it seems likely that space hotels will be built even in the early stages of space tourism.

Provision of low-cost passenger flights to orbit seems to have the potential to become a key opportunity for the space industry to tap a huge new commercial market. It is therefore highly desirable to devote resources to discovering whether it is possible to develop this business in the near future.

Like other large commercial development projects, the development of commercial space travel will require detailed discussion between people from many different areas of business, from manufacturing companies of course, but also from travel and hotel companies, marketing and media companies, insurance and law firms, and banking and finance companies. A successful project will come about only as the result of the combined efforts of these groups.

But in order to succeed, discussion between these groups must begin. It seems surprising that this discussion has not yet begun elsewhere within the world's space industry. Consequently it is beginning in Japan, with the work of this Space Travel Study Group of the Japanese Rocket Society. Let us hope that it will lead to a new, commercial "space race". If it does so, the winners will be the travelling public.

1. N Shute, 1954, " Slide Rule", Mandarin (1990 edition).
2. M Nagatomo, 1992, " Development organization and safety design environment of space transport system", in Perspectives of Advanced-Technology Society, RCAST, pp 132-3.
3. P Collins, 1988, "Space tourism - the door into the space age", Analog essays on science, Wiley, pp 193-204.
4. P Collins, 1991,"Benefits of passenger space travel for society", Proceedings of 5th ISCOPS, AAS Vol 77, pp 41-52.
5. G Hudson, 1991, "History of the Phoenix VTOL SSTO and recent developments in single-stage-to-orbit launch systems", Proceedings of 5th ISCOPS, AAS Vol 77, pp 329-351.
6. D Koelle and H Kuczera, 1989, " Sanger II, an advanced launcher system for Europe", Acta Astronautica, Vol 19, No 1, pp 63-72.
7. F Eilingsfeld and S Abitzch, 1992, "The prospects for space tourism: investigation on the economic and technological feasibility of commercial passenger transportation into low Earth orbit", Proceedings of 43 IAF Congress, IAA-92-0155.
8. M Nagatomo, 1993, "Space tourism: manned spaceflight for the general public", Proceedings of IAA Conference on Manned Space-flight, in press.