It has been a European company that pioneered space tourism: as early as 1954, Thomas Cook in Britain, the world's oldest travel company, initiated the 'Moon Register', a list where enthusiasts can sign an option for a commercial trip to the moon. The company guarantees to provide tickets at the earliest possible date. Despite the fact that Thomas Cook did not advertise the register, over 1,000 people have enlisted to date.(10)

In 1990, Ashford and Collins, renowned space tourism researchers from Britain, released 'Your Spaceflight Manual: How you could be a tourist in space within twenty years', a popular science book which introduced a large readership to the subject.(2)

In 1992, the launch of a Moon Register' campaign in Germany drew over 2,000 people to sign up within a couple of months.(10)

At present, still no opportunities exist for booking commercial space trips, either in Europe or anywhere else. In view of a European Common Market of almost 400 million citizens with an average GNP per capita of about $20,000 (1992), one must admit that the relative market potential for commercial space trips is promising. So the question is, what has to be done to build up a European space tourism industry?

Firstly, Europe must have a cost-efficient and man-rated launch system. Secondly, Europe needs a continental spaceport.

Optimal vehicle layout for commercial utilisation requires a 'design for operations'. This means that top priority has to be given to the reduction of recurring costs and to vehicle safety. It is a fact that currently evaluated European concepts of advanced HTOHL (Horizontal Take-Off, Horizontal Landing) launch vehicles support these objectives. They even promise to provide the required technology for future passenger launch systems, although this is not yet the focus of interest.

The trigger for the current favouring of a winged concept for the next century's European launcher was provided by various research efforts in the 1980s: the work done in the UK on HOTOL was followed later on by the start of the German SÄNGER programme and the French STS-2000. All these presently fragmented R&D efforts are likely to be merged into one single joint European launcher project. ESA is trying to pave the way for this with FESTIP (Future European Space Transportation Evaluation Programme). At present, the agency conducts "a general assessment study to decide whether or not reusable launchers, in their various possible designs, are the way to go to facilitate access to space." (8) Recent surveys concerning the development strategy for future commercial passenger transportation show that a two-stage HTOHL is likely to lay the foundation for the first European passenger orbiter. (1,2,5) After all, Europe once demonstrated technological excellence with Concorde and such a vehicle would appear to be a logical evolutionary step. Among all concepts named above, SäNGER is by far the best documented design (see Fig. 1). It has also been suggested for space tourism before.(1,5) A Sänger-type vehicle (STV) such as a 2-stage HTOHL launch vehicle with around 40 passengers and a launch mass of under 400Mg would povide the potential design for space tourism purposes. Political will provided, such a hypersonic vehicle could be ready for commercial operations in the year 2020. The relevant technical data of the Sänger vehicle is shown in Tab. 1. (including the product improvement).

Year		2020	2050
Configuration		HTOHL
Stages	[no]	2
Passengers	[pers]	36	43
Crew	[pers]	4	4
Launch Mass	[Mg]	366.00
Net Mass	[Mg]	184.7
Propellant Mass	[Mg]	178.1
Propulsion 1. Stage		Airbreather
Engines 1. Stage	[no]	6
Propulsion 2. Stage		Rocket
Engines 2. Stage	[no]	1
Launch Rate 1. St.	[LpA]	50	144
Lifetime	[launches]	450	850
Launch Rate 2. St.	[LpA]	25	55
Lifetime	[launches]	150	240

Europe is densely populated and its southernmost regions are still relatively remote from the equator. So, during the history of spaceflight European authorities have been forced to conduct launch operations overseas, in remote places like Hammaguir (Algeria), San Marco Equatorial Range (Kenya), Woomera (Australia) and Kourou (French Guiana). In view of increasing launch rates, the logistics for the support of a spaceport overseas might become too expensive. By operating an HTOHL launch vehicle one gains the ability to conduct missions from the European mainland. This new opportunity leads to the concept of a Spaceport Europe'. Such a concept comprises airport facilities optimised for ground operations of hypersonic transports, for vehicle refurbishment and in situ LOX/ LH2-production. The optimal location for such a facility would be the Southern tip of Spain.

The arguments in favour of such a location are:

• In situ solar powered propellant production is well served by the extremely sunny weather

• Southern Spain is relatively close to the equator (36.5° North).

• A wide range of launch azimuths lead over open water or uninhabited areas in Northern Africa.

• The glide paths of upper stage vehicles returning from orbit come in from over the open waters of the Atlantic.

Almost unknown to the public, there is already a place in Europe that is near perfect for serving as a base for a future spaceport: the former Rota Naval Air Station near Cádiz, Spain (Fig. 2).

Chosen as an emergency landing site for the Space Shuttle in the 1970s, Rota already has a runway (12,000 feet long) and ground facilities appropriate for launching and landing Sänger-type vehicles. But still, there are facilities that would have to be added for commercial passenger operations. The functional structure for the spaceport is shown in Fig. 3. Depending on passenger traffic, the investments for a spaceport with initial operating capability (IOC) would be in the range of some ten million dollars (1990 values).

Spaceport Europe' could become an excellent project for the development of transportation infrastructure in Southern Europe. But first, detailed site planning and environmental documentation for such a spaceport will be required.

Most critical for a flourishing space tourism market is low-cost transportation. As one can easily imagine, demand is a function of ticket price. The lower the ticket price, the more people want to fly into space. A first survey on the potential world-wide demand for LEO space tourism was undertaken in 1985 by Society Expeditions of Seattle, USA.(4) The company's quantitative findings are depicted as graphical function in Fig. 4.

It is obvious that any launch system selected for passenger transportation must show an economic performance that can be plotted in that region of the diagram where demand is greater than supply.

If the ticket price of any launch system for a given passenger throughput meets a market where demand is still greater than supply, one is able to bundle some extra services (to be paid) into a space tour package without strangling demand. Potential offers could include a stay in an orbital hotel. Therefore the decision as to whether it makes sense or not to include orbital hotels in a development strategy for space tourism requires an analysis of transportation cost trends. Based on a time horizon from 2020 to 2050, three different market growth scenarios (no growth; low growth; high growth) were developed. The three alternative growth functions for passenger transportation demand are plotted in the diagram in Fig. 5.

As one can see, the annual transport throughput is between 80 and 500,000 passengers. These demand trends served as input for an integrated operations and cost model. The two most important parameters, namely the annual launch rate and the vehicle inventory, are depicted in Fig. 6 and Fig. 7.

While an inventory of up to 200 upper stages plus around 100 booster stages reminds one of today's big airliner fleets (Fig. 7), up to 10,000 launches per year might cause some environmental problems, despite the LOX/ LH2-propulsion of the vehicles (Fig. 6). The simulation's results are used as input for the subsequent computation of cost trends.

Computer simulation of passenger operations within the given time horizon produced cost trends and allowed clues to potential cost reductions.

The estimation of cost parameters vs. time applied a statistical-analytical method which is based on the Transcost' model by D.E. Koelle.7 Some of the original Transcost equations were adapted, while most Cost Estimation Relationships (CERs) were either customised' or newly developed to handle a couple of special cases which were not taken into account by the original model. Most modifications concerned the hardware costs.

The philosophy behind the cost model and its computer implementation is laid out in Fig. 8.

The prime objective of cost analysis within this study has been the assessment of specific transport costs ($ per seat per flight). The specific cost equals total cost (overall operations cost) divided by numbers of passengers. The overall operations costs are split into five cost elements.

These comprise direct operations cost, indirect operations cost, vehicle amortisation cost, launch site/range cost and cost for maintenance and refurbishment.

In order to avoid cost peaks due to acquisition of new vehicles, the acquisition costs are amortised via the launch rate. The amortisation of R&D expenditures has been left out. The accuracy of cost figures is naturally limited by the accuracy of Cost Estimation Relationships (CERs). Transcost' which delivered most of the CERs utilised in this model, estimates accuracy to be +/-20 percent.

As already stated, keeping ticket prices as low as possible is imperative for sparking the development of a European space tourism market. System simulations of all three scenarios produced specific cost trends that would result in lack of demand (see Fig. 9), based on Society Expeditions demand projections.

The results show that ticket prices for round-trips to LEO of under $200,000 ($1990) are feasible, provided that demand is over 10,000 passengers per year (Low Growth Scenario). Even lower costs of under $60,000 require passenger numbers of around 500,000 per year. That is ten times (!) as many passengers as in the Society Expeditions' demand figure for the same price.

According to the same demand function, 500,000 passengers per year would only show up at the spaceport if they had to pay just slightly over $10,000 for a space tour. So in this case we encounter a "price gap" of around $50,000, or rather 400% of the demand price. Such a figure does not leave much hope for a working market.

After having seen that demand for space tourism could probably fall short of the costs of the space tourism sector, one has to ask oneself what could be done to bridge the "price gap" shown in Fig. 9? The answer is easy, either the launch system operations become less expensive or the potential customers become wealthier. Since the first option is out of the question hope of an even better vehicle than a Sänger-type vehicle coming out of Europe within the next decades seems to be completely unfounded a sensitivity analysis of Society Expedition's demand curve has been conducted.

Different levels of wealth increase within the target group (high income people: HIP) have been assumed and the resulting overall demand (devoted to space tourism) as a function of passenger throughput has been plotted together with the overall costs. The year of reference is 1990. As one can see, the No Growth Scenario requires only about 1% per year increase in real purchasing power (from 1990 on) for reaching the demand/supply-equilibrium (see Fig. 10).

The Low Growth Scenario already requires between 2% and 3% annual wealth increase (see Fig. 11) to be sustained.

The High Growth scenario requires as much as between 3% and 8% annual increase, depending on the respective passenger numbers (see Fig. 12). That is quite a high number, even if one keeps in mind that the high income people (the target group for space tourism) become richer faster than the average population.

It might be questionable to found the future of space tourism on the uncertain growth of individual wealth alone, so another alternative comes into mind: in case of lacking demand due to high prices, ticket sales may be boosted by some kind of space tourism lottery.

To be sure, many more people would be willing and able to buy a cheap lottery ticket instead of an expensive space tour ticket itself. Taking state lotteries as an example, a space tour lottery would raffle space tour tickets among all those people who previously bought a lottery ticket. Assuming that a lottery organisation could use up to two thirds of its turnover for purchasing space tour tickets, sustained operation of any of the three scenarios would require yearly lottery ticket sales as shown in Fig. 13. Provided, of course, that the demand grows according to Society Expedition's 1985 survey.(4)

While the figures for the No/Low Growth scenarios look as if lottery-augmented space tourism could work, the corresponding values for the High Growth Scenario look way off: $500 million of required lottery turnover per week (!) in 2050 may be beyond any demand.

Pricing is the most important issue in the high-risk world of commercial space. The strong interdependence between ticket price and space transportation demand as mentioned before makes this clear.(1) Any pricing strategy has to take into account the negative effect high profitability leading to rising prices could have on demand. As long as the premise is to initiate a new market for manned space transportation systems in conjunction with public access to space, a high profit margin should not be the focus of interest.

The dilemma with this survey is that all three scenarios promise seat costs higher than the demand price per ticket. This means losses rather than profits and leaves no room for any discussion of pricing policy. Unfortunately, such cost projections leave little leeway for space tour extras like staying in an orbital hotel or visiting an orbital recreation facility.

After all, the market projections could be too pessimistic, but, whatever the real market development will be, in view of the cost degressions attainable with a Sänger-type vehicle, any future supplier of commercial space tours would most probably have to do without much profit.

A European Space Tourism Initiative is feasible. Crucial is, however, to strive for this goal. ESA's FESTIP programme and its successors will hopefully produce an Advanced Launch Vehicle that could be used for Commercial Space Tours. Rota Airport is also there and could be converted into a real European Spaceport for Aerospace Planes and other HTOHL vehicles.

The economic feasibility calls for a small initial market volume, say 2 to 4 launches per year, and then a slow growth towards a balanced market, whatever its volume may be. An additional space tour lottery might prove to be a liable way to balance possible price gaps; furthermore a lottery would attract far more people to the subject of space tourism than the space tour business itself.

Admittedly, the given cost calculations do not leave much room for goodies like orbital hotels. So European Space Tours will most probably be limited to day trips into LEO. A day trip here means 5 - 8 orbits and up to 12 hours of flight duration. Nevertheless, space tourism offers a bold, positive vision for Europe's future in space.

1. S Abitzsch and F Eilingsfeld, 1992, "The Prospects for Space Tourism: Investigation on the Economic and Technological Feasibility of Commercial Passenger Transportation into Low Earth Orbit", Preprint IAA-92-0155.
2. David Ashford and Patrick Collins, 1990, "Your Spaceflight Manual: How You Could Be A Tourist in Space Within Twenty Years", London: Headline
3. P Q Collins and D M Ashford, 1998, "Potential Economic Implications of the Development of Space Tourism", Acta Astronautica 17: 421-431.
4. Patrick Q Collins, 1989, " Stages in the Development of Low Earth Orbit Tourism", SpaceTechnology 9: 315-323
5. Dietrich E Koelle and Wolfgang Kleinau, 1989, " Man-into-Orbit Transportation Cost: History and Outlook", Preprint IAF-89-695
6. Dietrich E Koelle and Heribert Kuczera, 1990, " SÄNGER Space Transportation System: Progress Report 1990", Preprint IAF-90-175
7. Dietrich Koelle, 1991, " TRANSCOST Statistic-Analytical Model for Cost Estimation and Economic Optimization of Space Transportation Systems", München: MBB-Report URV-185
8. M Pfeffer, June 1993, 'ESA studies future launchers: The winged launcher configuration studies' Reaching for the Skies 8: 1-3
9. 'Tourismus größter Arbeitgeber', Der Tagesspiegel 14183: 47, 26 April 1992
10. Christiane Wronski (Marketing & Public Relations Representative of Thomas Cook Germany), Personal Communication, 6 March 1993.