'Space policy' began as a tactic of the 'cold war'. The orbital flights of Sputnik in 1957 and Yuri Gagarin in 1961 suggested that the Soviet Union was technologically ahead of the USA and therefore a threat, because the technology used for launch was the same as that used in inter-continental ballistic missiles (ICBMs). In response, the US government established a civilian agency to compete with the Soviet Union by performing publicly visible 'space missions'. Initially tasked with launching small satellites, NASA later used missiles to perform sub-orbital crewed flights, and later orbital flights. Between 1961 and 1963 NASA grew rapidly from some 3,000 staff to 30,000 in order to carry out the 'Apollo Project'. Thereafter the 'Skylab' space station and the partially re-usable space shuttle were built and operated. Other countries, notably Europe, China and Japan, established government agencies and policies to develop launch vehicles and satellites.

It is notable that the concept of 'Space policy' is anomalous: governments do not have 'Atmosphere policy' or 'Sea policy'. They fund a range of civilian activities relating to both the atmosphere and the sea, but their main purpose is to aid the development of successful commercial activities (centred on transportation) in both environments. Both marine transport and air transport are today multi-hundred-billion-dollar industries. Government researchers continue to perform a range of research activities in both fields, but these are much smaller than the corresponding commercial transportation activities.

The objective of space technology development is often said to be 'preparation'. However, unless these preparatory activities lead on to commercially profitable activities, they are not economically beneficial. Furthermore, bearing in mind the 'time value of money' it is necessary for commercial profits to arise within a reasonably short period of time. For example, if some activity is not expected to lead to commercialisation for 20-30 years, it would be economically preferable to delay funding and focus on other work with potential for earlier application.

'Space policy' has continued for several decades to date, but the politico-economic environment of space activities has changed radically in several ways in recent years:

1. The end of the cold war removed the political justification for many government space activities (including the covert subsidy of missile technology).

2. Commercialisation has been recognised as the most important objective of space activities, since only in this way will they contribute to economic growth.

3. Space travel services for the general public have been widely recognised as the major space business in future, likely to grow to more than $100 billion/year and employ millions of people.

4. In both Japan and Europe unemployment is at historically high levels, and the USA's trade deficit is at a historical high, so there is an urgent need to develop new industries. As one such new industry, popular space travel could grow to play a major role in the 21st century world economy, similar to that played by air travel during the 20th century.

These changes in the political and economic environment of space activities justify revising the plans (short-term, medium-term and long-term) of government space agencies - just as changes in the business environment have caused many companies to revise their plans, even at the cost of corporate restructuring leading to reductions in employment.

However, to date, government space organisations have been extremely reluctant to change their activities, a large part of which still involves developing and operating expendable satellite launch vehicles, even though it is now clear that even the most successful of these are not commercially profitable. Consequently, it is desirable for space agencies to restructure their activities appropriately, however unwilling the responsible officials may be. The changed environment entails that if this is not done, their budgets are likely to be cut.

It is now widely acknowledged that space tourism is feasible, able to start soon with sub-orbital flights, and likely to grow into the largest commercial activity in space, including by NASA (1), by the AIAA (2), and by Keidanren (3). The potential economic benefits are particularly important since there is no other space activity that has comparable potential to create a large launch market. Expendable launch vehicles are too expensive to enable space activities to grow substantially. Reusable launch vehicles (RLVs) can greatly reduce the cost of access to space, but there is no economic value in developing an RLV that cannot carry passengers, since it will not be profitable due to the small market for satellite launch.

While there are plenty of matters about which economists disagree, there is no controversy about how to estimate the value of a piece of work: it is the present value of the profits that can be earned in the future as a result of the work. The resulting estimate is inevitably uncertain since the future is not precisely predictable, but the calculation process is straight-forward and the assumptions made about both future profit estimates and the appropriate discount rate are explicit, so they can be discussed and revised as new information becomes available.

On this basis it is clear that, among all the work that space agencies have performed over the past 10 years - at a cost of $250 billion to taxpayers - the most valuable product was NASA's report 'General Public Space Travel and Tourism' (1), since it identifies what is predicted to become the largest business activity in space, and includes a long list of recommendations for governments to implement to help realise it.

However, NASA has not followed its own recommendations, and provides no funding for tourism research - despite the fact that it has a legal responsibility to support commercialisation of space activities. It has been said that "NASA ... doesn't believe that its mission is to help taxpayers go to space"(4). The European Space Agency likewise provides no funding for work aimed at realising passenger space travel.

However, with appropriate funding, space tourism services can start within just a few years, with sub-orbital flights. The experience of operating passenger flights of sub-orbital rocket vehicles will facilitate raising the funds needed to develop orbital tourism services, which promises to grow to some $100 billion/year (5). The existence of this possibility begs the question: Why are governments not trying to realise this possibility? Since all crewed space flights are funded by governments, this is a matter of political economy.

Since most space activities, including essentially all crewed space activities, are currently funded by governments, proposals for changes in these activities and in their objectives inevitably involve political change. That is, deciding to implement the proposed changes is not solely a matter of determining what is economically desirable, but also involves overcoming the resistance of groups with a vested interest in maintaining the status quo. Change may therefore require forming a coalition to outweigh such interest groups. The 'public good', that is the interest of taxpayers, is influential in revising out-dated policies only in so far as politicians feel significant popular support for a change.

Just as markets have flaws that economists have analysed in detail, government organisations also have weaknesses that are well-known to economists and organizational experts. The 1986 Nobel prize for economic science was awarded to the American economist Professor James Buchanan for his work on 'public choice economics', analysing the economics of government, which has been very productive in explaining the behaviour of politicians and government officials (6). The following are some of the weaknesses seen in government space activities

1. Slow response to change

   All large organisations resist change: Machiavelli described some of the reasons for resistance to change in government organisations more than 400 years ago. However, in the case of companies, when the environment changes so that a plan is no longer viable, shareholders press for restructuring to avoid or eliminate losses. However, government organisations do not have shareholders, and it takes longer for policies to be updated.

   In the present situation, for space agencies to continue pressing governments to fund projects that were planned some 10 years ago, which would make no contribution to economic growth and would add billions of dollars to government debts, is highly undesirable for taxpayers. For example, there is no economic value in developing and operating vehicles which will not be profitable, and which do not lead on technologically to other vehicles which can be commercialised. While other objectives such as subsidising military capabilities may benefit, at a time of particular economic difficulties it is important for the space industry also to aim at economic benefit.

   For this it is economically desirable for government to take the position: "The world has changed dramatically in recent years - with the end of the cold war, rapid economic development in many more countries, and rapid technological progress especially in computers and communications. As a result our objectives for space development must change to match the new environment." Unfortunately, government officials responsible for 'space policy' appear to hold the view: "We must stick with our old plan, however much it costs taxpayers, and however little economic value it has."

   Government officials are said to fear that if they change their plans they will be criticised for having followed a different plan previously. However, since the national and international situation have changed in major and unpredictable ways over the past decade, this necessitates appropriate changes in plans for space development. It is only to be expected that plans made as long as 15 years ago need to be revised to make them appropriate to present-day circumstances. Many other industries have been undergoing wrenching change, with closures of old facilities, international mergers and acquisitions, restructuring, and bankruptcies of companies unable to change appropriately. It is desirable for the space industry also to revise its objectives and activities to reflect the new economic situation. Furthermore, if governments continue to spend huge quantities of taxpayers' money on projects that are economically valueless they will be even more severely criticised for not revising their plans earlier.

2. Risk aversion

   By comparison with companies, government organisations discourage risk-taking. In the present situation it is economically important for space agencies to innovate by adopting new objectives - but this poses new risks. If this difficulty is not overcome, the space industry is in danger of becoming a 'dinosaur'.

3. Protection of vested interests

   Government organisations have an interest in protecting client companies that carry out government contracts on government projects. However, there is no economic value in preserving particular companies if this delays desirable change, raises costs, and reduces efficiency.

4. Inappropriate experience

   In the case of initiating passenger space travel services, another important influence is that government space agencies have insufficient experience. By contrast the aviation industry has decades of experience of passenger travel. Thus it is essential to initiate formal collaboration between space and aviation companies and organisations(7).

An additional factor that makes the need for change more urgent is the threat of the US government's 'Super 301' trade law. This is already in place to prevent unfair government subsidies of commercial satellites and launch vehicles, but not yet for RLVs. However, the application of 'Super 301' to RLVs is already under discussion. Thus there is a limited time-window during which governments can invest in building a capability to participate in what will become the largest business in space.

From the point of view of political economy, the popularity of the goal of passenger space travel is sure to mute any criticism that might be expressed about the development cost or about periodic failures.

A major objective of economic policy is to enhance economic growth - that is to raise average incomes, and thereby increase the economic resources available to society. One effect of the steady increase in individual productivity that underlies economic growth is that it continually reduces the number of employees needed to produce a particular quantity of industrial output. Consequently, an important part of successful economic policy is the encouragement of innovation, and of the development and growth of new industries (8).

Unfortunately, governments commonly devote much larger resources to the preservation of older industries - in order for politicians to be seen to be 'preserving jobs'. From the economic point of view this is very wasteful: not only is it undesirable to protect inefficient companies that should restructure in order to preserve their economic competitiveness in a changing business environment, but giving public resources to them also reduces the resources available to support new activities, and enables them to resist the growth of new companies more strongly. This problem is a weakness of democratic systems of government, as has been analysed by Buchanan and colleagues (6).

Nevertheless governments do contribute to the development of new industries, including particularly successive generations of passenger transportation systems - from sailing-ships, canals and railways to ships, cars and aviation. However, although governments have given large sums to the space industry, economic policy-makers have given it little attention - partly because it is relatively small, and partly due to the mistaken belief that space travel is inevitably so expensive that it will remain small and government-funded for the foreseeable future. Consequently, government support for space activities has been guided not by economic policy, but by 'space policy' as discussed above.

However, from the point of view of economic policy, it is clearly desirable for government investment in the development of space capabilities to focus on activities that have the potential to become commercially profitable - and thereby contribute to economic growth and employment. Since it is now widely agreed that tourism has the greatest commercial potential in space, developing passenger space travel services is economically much more valuable than any other space development activities.

If it was widely accepted that the development of passenger space travel services was so difficult that it would require another 20 years of technology development, then in that case it might be sound policy to continue to spend public funds on the development of technological systems with little economic value. However, the contrary is true: it is increasingly widely acknowledged that tourism has unique potential - recently, for example, by the ex-director of NASA's Advanced Projects Office (9), and by the ex-CEO of Lockheed-Martin Corporation (10).

Because of this fact - that it is possible to develop a profitable, commercial passenger space travel industry - the most economically valuable target for government space development spending is to develop a passenger space transportation system. Furthermore, delay in developing this new business imposes major costs in the form of lost economic activity and lost employment. Hence continuing government funding of $25 billion/year for space activities with little or no commercial potential, while spending almost nothing on activities that contribute to the early development of passenger space travel, is a very serious misallocation of resources. This situation is clearly very unsatisfactory from the point of view of economic policy, particularly since the macro-economic situation is currently very unsatisfactory.

At the turn of the 21st century the world economy is in an unusually critical situation, with record levels of unemployment in many countries, both rich and poor, and the threat of deflation caused by over-capacity in many older industries together with a lack of new industries. In this situation, the possibility of creating a new consumer service industry with the potential to grow into an activity as large and influential as aviation is of the greatest value, and should be pursued with urgency (8).

In the following we look at the major countries from the point of view of the prospects for change in their national space policies towards contributing to economic growth through encouraging passenger space travel.

NASA's success with the Apollo program and its monopoly position in US society has had enormous influence on the view of space activities expressed by the media. This is coupled with widespread popular mis-understanding about NASA's objectives. Many people believe that "If space tourism was possible, NASA would be doing it." However, current NASA administrator Goldin has made it clear that he will not help US taxpayers to have access to space. He is not implementing the recommendations of NASA's (very positive) report on space tourism (1), and even declines to make it available to the public.

It is said that "Success is the root of failure". NASA's cold-war success led to its continuing as a government monopoly until it has become counter-productive in delaying public access to space. Because of this institutional resistance to change, a private, non-US organisation, the Japanese Rocket Society ( JRS), has been able to show leadership to NASA, many of the references in (1) being to published results of the JRS Space Tourism Study Program.

As an agency of the US government NASA should implement US government 'space policy', which includes helping the commercialisation of space activities. NASA's failure to do this is typical of a 'Buchananite' government monopoly defending its own interest at the expense of taxpayers (6).

By contrast, the FAA's Associate Administrator for Commercial Space Transportation is showing the leadership that is lacking in the official 'space industry'. Following the US government's positive and far-sighted move in 1995 to put the Office of Commercial Space Transportation (OCST) into the FAA, she has made positive speeches about space tourism, and is working to extend aviation regulations to cover passenger space travel (11).

Progress is also being made by a number of US companies and organisations such as the Space Transportation Association (STA), the Space Tourism Society (STS), the 'X-Prize' Foundation, and companies Gold & Appel, Bigelow Aerospace, and several others developing reusable launch vehicles, such as Kistler, Kelly, Rotary Rocket and Pioneer. However, they are all seriously constrained by lack of funding - while NASA spends $14 billion every year on a range of space activities with little economic value.

The Soviet Union's space activities were entirely government-funded, and there was no 'consumer culture' to even suggest the idea of space tourism. By contrast, today, Russian and Ukrainian companies are ready and willing to participate in developing a space travel industry, although there are few investment funds available within these countries themselves.

However, the pressure to raise commercial investment is very productive, and has led to the innovative joint venture MirCorp established by the companies Energiya and Gold & Appel in early 2000. This is currently offering passenger flights and accommodation services in orbit. There is also said to be an agreement with SpaceHab to develop and operate commercial habitable modules in the Russian section of ISS.

The Japanese government funds space research at the Institute for Space and Astronautical Science (ISAS) through the Ministry of Education, Science & Culture and at the National Space Development Agency (NASDA) through the Science and Technology Agency (STA). These organisations are constrained by the current space policy concerning crewed space activities which limits spending in this field to collaborative activities involving the US space shuttle and the international space station ( ISS). In view of the unique economic potential of passenger space travel and accommodation services, it is clear that until this policy is revised Japanese space activities will be economically loss-making.

Since 1993 the JRS has had considerable influence in putting the subject of space tourism onto the agenda in the USA, Germany and Britain, and its work has been praised in these countries. The JRS is continuing to pioneer with studies on legal and regulatory issues, and preliminary consideration of a piloted sub-orbital demonstrator vehicle - which is a key step to realising passenger space travel.

The STA's cumulative deficit on space expenditure to date was officially calculated in early 2000 at some $18 billion. Continuation of the current rate of spending of some $3 billion/year would almost treble this cumulative deficit over the next decade, and the failure to achieve any economic return on this investment would be an unattractive burden to Japanese taxpayers - particularly at a time when unemployment is at a post-war record due to lack of investment in new industries, and when the Japanese government's overall financial deficit has reached a historically high level.

The economic policy viewpoint is particularly important in the case of Japan, since prolonged resistance to necessary economic restructuring has cost the Japanese several trillion dollars in lost economic output and increased government debt through the 1990s. The Head of Japan's Economic Planning Agency, Sakaiya Taichi, has stated in speeches that unless Japan has another 'Meiji Revolution' the economy will not recover.

(It is interesting to note that the Meiji revolution was a bloody civil war that led to the 180-degree reversal of national policies that had been followed for decades: the Tokyo-based government of the early 19th century had become incapable of adapting to match the changing outside world, paralysed by short-sighted protection of vested interests in maintaining the status quo. This caused enormous economic costs - and finally profound strategic danger to Japan. Consequently the revolutionary leaders from the west of Japan, who understood the global situation better than government leaders in Tokyo, overthrew the government militarily and introduced radically new policies which led to rapid technological progress, rising living standards and extensive social changes. It also subsequently led to the rise of non-democratic militarists who initiated military expansionism, finally plunging Japan into the 2nd world war.)

Resistance to change in the space industry could limit Japanese participation in future passenger space transportation to operating and component-manufacturing - similar to the Japanese airline industry which operates foreign-made aircraft. This danger is aggravated by the fact that in order to play a significant role in manufacturing, in which Japan has more of a national competitive advantage than it has in services, manufac-turing companies need to participate in advance of operating companies. If this opportunity is lost, it will not be through lack of ability or foresight by Japanese engineers, but due to the preference of government and managers of aerospace companies to preserve the existing 'not for profit' status of space activities rather than to innovate in doing what is clearly greatly in the economic interests of taxpayers.

Government reforms under way in Japan include the merging of STA with the Ministry of Education; this provides a timely opportunity to clarify the objectives of space spending. Space science includes a number of fields of scientific research, such as astronomy, space biology and micro-gravity, which have value as fields of science, and represent about 10% of space spending. Approximately 90% of spending is on what is called 'space development', but the meaning of this is less satisfactory.

Expenditure on space development should have an economic aim. Although the development of basic technological skills such as rocket engineering has potential economic value, its actual value depends on whether the technology is successfully used for commercially profitable purposes. To date STA has had no official responsibility to contribute to economic growth or to develop commercially valuable industries. Hence it is important that the reorganisation of government responsibilities in this field should be used to focus space spending on economically valuable objectives. To continue to use taxpayers' money to develop space technology without any requirement that it must have positive economic value would be a very costly waste of a rare opportunity.

At a time of vigorous economic growth it might be acceptable to continue to spend taxpayers' resources on uneconomic space activities as a cultural activity or a national luxury. But in the present conditions of record levels of unemployment, negative economic growth and deflation caused by prolonged lack of investment in new industries, it would be irresponsible not to focus government space spending on economically valuable activities. This should include spending to enable companies to participate in the new industry of passenger space travel.

Some of the earliest studies of space tourism were performed at MBB Gmbh, and these were followed by work at Berlin Technical University. Space Tours GmbH, a subsidiary of Daimler-Chrysler Aerospace Gmbh, built on these beginnings and held the first historic International Symposium on Space Tourism (ISST) in Bremen in 1997, followed by the 2nd ISST in 1999. As prime contractor for the Columbus module, the European contribution to ISS, and the largest shareholder in SpaceHab, Daimler-Chrysler performed an internal study of the feasibility of tourism, concluding that it is a market to be aimed at in future (12). In addition, having developed the Columbus habitable module, the company is interested in making and selling as many units as possible, and has recognised that the only market for many modules is tourist accommodation. A study of future hotel accommodation in orbit has also been prepared by staff at DLR who produced a design for 'Space Hotel Berlin' using components that have already been developed (13).

However, work aimed at developing passenger launch vehicles is held back by the German government's participation in the Ariane 5 launch vehicle, and by ESA's policy that there is no need for any other vehicle until 2020 or later. This influence is not as strong as it is in France, as demonstrated by the joint development of the Rockot launch vehicle by German and Russian companies.

The French government has made the largest investment in expendable launch vehicles in Europe, and follows the policy that there is no need for any launch vehicle other than Ariane 5 until 2020. France did not even participate in ESA's 'FESTIP' study program of reusable launch vehicles. As a result of this policy stance, French researchers have contributed the least to realising space tourism among the advanced countries: as of 2000, not a single paper has been published on the subject by a French researcher. The only related activity in France has been by a small number of students and journalists.

During the 1980s, the Thatcher administration revised British space policy to focus government spending on scientific research and on space activities that are commercial or potentially commercial, such as telecommunications, broadcasting and remote sensing. In addition it was decided not to participate in Ariane 5 since launchers are unprofitable, nor in ISS since it is not cost-effective. Government spending of some $300 million/year has been concentrated on space science including astronomy, and on the telecommunications and remote-sensing industries.

Despite this lack of support, British researchers have made valuable contributions towards the realisation of space tourism. Bristol Spaceplanes Ltd (BSL) has achieved the highest technical credibility among promoters of sub-orbital passenger vehicles for its 'Ascender' (14). In addition to a series of refereed papers over some 20 years, in 1990 BSL's founder David Ashford published the first ever book on space tourism, which explains both its technical and economic feasibility, and its importance for the future development of space (15). The author too has published more than 50 refereed papers on many aspects of space tourism; carried out the first market research on the potential demand for space tourism; and co-founded the leading web-site providing information on space tourism www.spacefuture.com

The economic role of passenger space transportation in enabling low-cost access to space is increasingly widely recognised, and in 1999 the 2nd UK-Japan Workshop on Space Tourism concluded that "Space tourism should be considered in future revisions of the UK's space policy" (16).

Since NASA published its 1998 report 'General Public Space Travel and Tourism' identifying passenger space travel as the most promising business in space, the UK policy not to support work on launch vehicles has become contradictory to its policy to focus on potentially commercial activities. In late 1999 the UK government announced a review of its space policy to take place in early 2000: it is greatly to be hoped that the British government will remove the contradiction from its policy by removing the restriction on support for work on launch vehicles, provided that they are designed to carry passengers.

Other countries with satellite launch capabilities, notably India, China, Brazil, Israel, Pakistan, North Korea, are still limited to expendable launch vehicles. Although China has announced plans to launch a crew on an expendable launch vehicle, this will have no economic value since it will be too expensive to generate significant commercial revenues. As such it will be a drain on the Chinese economy, but this is presumably considered to be less than the political benefits to the government.

The above has looked at the need for 'space policy' to be revised in the light of the new realities of the post-cold-war world economy; at the feasibility and benefits of developing a space tourism industry including its potential contribution to economic growth; and at the importance of this for economic policy, for which there is an urgent need to create new industries to counteract deflation.

The delay in revising the objectives of government spending on space activities to include the profitable new direction of passenger space travel is caused by those responsible for deciding 'space policy', and is imposing large costs in terms of lost economic opportunities and unnecessary prolongation of high unemployment.

The development of space tourism is economically too important to be left to 'space policy'. The potential value of creating a new industry as large as aviation is much too important to allow government space activities to continue to be decided without input from economic policy. Economic policy-makers should therefore insist that space funding is targeted on realising what NASA (1), AIAA (2), Keidanren (3) and others have identified as the largest business opportunity in space.

In order to realise a passenger space travel industry, it is essential for space industry staff to collaborate with their counterparts in aviation, who have enormous experience of carrying passengers safely and profitably in advanced-technology aerospace vehicles. However, because of their history, their structure and the motivations that these create for their leaders and staff, government space agencies are very reluctant to change in this way. In addition, companies which earn substantial revenues from making expendable launch vehicles will not try to develop reusable launch vehicles, since this would be against their shareholders' interests by making their existing vehicles obsolete.

It is very important for the general public, the media, and the political leadership of the advanced countries to recognise these limitations clearly. If this collaboration does not start soon, it will be desirable to reduce the budgets of space agencies and transfer the funding to aviation organisations to develop passenger space travel services - as is being advocated in the USA (17). A relatively small initial government investment could be effective in starting the development and rapid growth of popular space travel services, leading to the creation of great economic wealth (5, 8, 9). This is economically highly desirable, particularly at a time of exceptionally high unemployment.

In general, governments will not make better decisions than their electorates. If, for example, the electorate do not understand that new industries are needed to create new employment, and if they do not understand that developing a space tourism industry is now feasible and economically desirable, they will not press politicians to implement these policies. Consequently, a very important activity for realising a passenger space travel industry is to bring these matters to the attention of the general public.

With good policy decisions, sub-orbital passenger space flights can start within just a few years, and the operating experience accumulated will contribute directly and indirectly to developing orbital tourism, which promises to grow like aviation to reach $1 trillion/year. As well as being economically desirable, work towards realising this optimistic future will be very popular with the general public. Consequently it is to be hoped that the space industry will reform itself appropriately in the very near future.

1. D O'Neil et al, 1998, "General Public Space Travel and Tourism - Volume 1 Executive Summary", NP-1998-03-11-MSFC, NASA/ STA; also downloadable from www.spacefuture.com.
2. M Gerard and P Jefferson (eds), 1998, " International Cooperation in Space: New Government and Industry Relationships", Report of an AIAA/ CEAS/ CASI workshop, AIAA; also downloadable from www.spacefuture.com.
3. Anon, 1998, ' Space in Japan', Space Activities Promotion Council, Keidanren, p 11.
4. T Nagel, 18 October 1991, 'Customers Lining Up to Tour Space', San Francisco Chronicle, Business/Technology Section, p 1.
5. P Collins, 2000, "The Space Tourism Industry in 2030", Proceedings of Space 2000, American Society of Civil Engineers, pp 594-603; also downloadable from www.spacefuture.com.
6. P Collins, 2000, "Public Choice Economics and Space Policy: Realising Space Tourism", IAF Congress paper no IAA-00-IAA.1.3.03.
7. P Collins and Y Funatsu, 1999, "Collaboration with Aviation: The Key to Commercialisation of Space Activities", IAF Congress paper no IAA-99-IAA.1.3.03; also down-loadable from www.spacefuture.com.
8. P Collins, 1999, "Space Activities, Space Tourism and Economic Growth", Proceedings of 2nd International Symposium on Space Travel, Bremen; also downloadable from www.spacefuture.com.
9. I Bekey, 1988, "Economically Viable Public Space Travel", Proceedings of 49th IAF Congress, 1998; also downloadable from www.spacefuture.com.
10. N Augustine, 2000, 'The Wright Brothers Meet Adam Smith', Aviation Week & Space Technology, Vol 152, No 1, pp 48-9.
11. P Smith, 1999, " Reliability and Space Transportation", Space News, Vol 10, No 30, p 15.
12. H Muller et al, 1998, " Space Tourism - New Business Opportunity or a Remaining Fiction?", Proceedings of 49th IAF Congress.
13. M Reichert, 1999, "The Future of Space Tourism", IAF Paper no IAA-99-IAA.1.3.07; also downloadable from www.spacefuture.com.
14. http://www.bristolspaceplanes.com/projects/ascender.shtml
15. D Ashford, 1990, "Your Spaceflight Manual", Headline.
16. BIS News, Spaceflight, Vol 41, p 317, 1999.
17. T Rogers, 2000, Presentation to FAA Space Transportation Conference, February 8, Arlington, VA.