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29 July 2012
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16 July 2012
Space Future has been on something of a hiatus of late. With the concept of Space Tourism steadily increasing in acceptance, and the advances of commercial space, much of our purpose could be said to be achieved. But this industry is still nascent, and there's much to do. this space.
9 December 2010
Updated "What the Growth of a Space Tourism Industry Could Contribute to Employment, Economic Growth, Environmental Protection, Education, Culture and World Peace" to the 2009 revision.
7 December 2008
"What the Growth of a Space Tourism Industry Could Contribute to Employment, Economic Growth, Environmental Protection, Education, Culture and World Peace" is now the top entry on Space Future's Key Documents list.
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P Collins, 1998, "Tourism in Low Earth Orbit: The Trigger for Commercial Lunar Development?", Proceedings of Space '98, ASCE, pp 752-756.
Also downloadable from in low earth orbit the trigger for commercial development.shtml

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Tourism in Low Earth Orbit: The Trigger for Commercial Lunar Development?

The potential market for liquid oxygen produced at the lunar surface for use by passenger launch vehicles and accommodation facilities in low Earth orbit ( LEO) is estimated. It is concluded that oxygen may be the first major commercial lunar export, and so low Earth orbit tourism is potentially very important for lunar development.


Considered from a commercial point of view, the feasibility of lunar development depends on achieving lunar exports - that is generating revenues outside the lunar economy from activities on the Moon. This is because the investment made in facilities on the Moon will come from investors on Earth - and so it must be repaid to those investors from profits earned on sales of products and services provided from the Moon to consumers on Earth. (In the absence of commercial investment, government funding could be used for lunar development up to a point. However, this is not predictable, and does not generate economic growth as business investment does.)

In the following we ignore revenues from the sale of lunar services, namely scientific research (because it would be small-scale) and lunar tourism (because it will also be small-scale for a relatively long time). Achieving exports therefore requires selling lunar materials processed and delivered to customers. (Transmitting microwave energy from the Moon to the Earth has also been proposed, and may become an attractive business opportunity - but significantly later than that proposed in this paper.) Ignoring also the possibility of finding large quantities of lunar ice (which could potentially provide a source of water, oxygen and hydrogen) the only materials available for export from the Moon are materials extracted from regolith and/or rock, such as glass, concrete, oxygen, silicon, metals. At a later stage, advanced materials and manufactured products may also be exported, but raw materials would be easier to export initially. Among the various raw materials that could be produced on the lunar surface, the extraction of oxygen from lunar rock has been under investigation for several decades, and experimental research has increased in recent years (1).


For basic materials, transportation costs are a major component of the final cost to the user. Materials exports from the Moon to any market will face competition from similar materials extracted and delivered from Earth (as well as from other extra-terrestrial sources). Roughly speaking, the cost of transporting lunar materials rises with increasing distance from the Moon, while the cost of terrestrial materials rises with increasing distance from the Earth. Following this simplified approach, the possible markets for lunar materials, in order from the most attractive to the least attractive, are the lunar surface, low lunar orbit, high lunar orbit, geo-stationary orbit ( GEO), low Earth orbit ( LEO), and the Earth's surface.

Substantial commercial facilities are not foreseen on the Moon or in lunar orbit in the near term. And until large-scale solar power satellites ( SPS) are built in geo-stationary orbit, the potential commercial demand there will probably also be small.

However, in recent years, discussion of potentially large-scale commercial facilities in LEO has grown considerably, centered on the potential demand for orbiting tourist accommodation, as described in the growing body of work concerning the feasibility of LEO tourism (2). As a result of this there is a growing body of opinion that such an activity is both commercially feasible and has the potential to grow into a large and profitable business activity. Indeed it has been proposed that this is the only way in which crewed space activities will become profitable.

JRS Scenario

A major piece of this work is the ongoing Space Tourism Study Program of the Japanese Rocket Society ( JRS), begun in 1993, which has led to the publication of a series of papers and reports (3). Part of this study involves a scenario for development of a space tourism business, based on the production of 8 " Kankoh-maru" VTOL passenger vehicles per year, each of which is capable of carrying 50 passengers to LEO 300 times per year over a 10-year lifetime. This assumption leads to a LEO passenger market growing by some 100,000 customers/year/year. This scale of activity has been criticized as being too large to be believable, but it is trivially small compared to commercial aviation which carries 3 million customers per day, and it would satisfy only a small part of the known demand.

However, in order to reach this scale of activity, market research suggests that accommodation will be required in orbit for thousands of guests, since most people say that they would prefer to stay in orbit for a few days. This will involve assembling thousands of tons of facilities in low Earth orbit, and will create a range of potential opportunities for sale of lunar materials. Eventually a wide range of products manufactured in space from lunar and other non-terrestrial materials may be sold in LEO to builders and operators of orbital accommodation. Hence we consider potential markets that should be accessible in the earlier stages.

Radiation Shielding

Materials as simple as bagged regolith may come to be used as shielding from radiation and/or from debris collisions. If this market became attractive, the tonnage involved could be very significant.

Liquid Oxygen ( LOX)

In many studies of lunar surface development, one of the first industrial products planned to be produced on the lunar surface is oxygen. Many different processes for producing it from lunar rocks have been designed, and practical experiments have been carried out in a number of companies and laboratories (4). However, to date, there has been no commercial motivation for this work: LOX production has been studied for use by those working on the lunar surface, who are generally assumed to depend almost entirely on government funding.

Due to the low lunar gravity of 1/6 that on Earth, the lack of an appreciable atmosphere, and the abundance of solar energy, it is possible to launch materials from the lunar surface through using linear-motor technology, and hence without using fuel. Thus, lunar LOX could potentially be delivered from the lunar surface to LEO at relatively low cost if performed on a large scale.

Orbital accommodation will require regular resupply of oxygen. In addition, on each flight to orbit, passenger vehicles such as Kankoh-maru must carry sufficient propellant to be able to de-orbit and land. Since Kankoh-maru uses cryogenic engines, it carries several tons of liquid oxygen to low Earth orbit on each flight. The JRS scenario in which 8 Kankoh-maru vehicles are built each year and the number of flights grows by 2400 flights/year/year therefore involves carrying LOX to LEO in quantities growing by several thousand tons/year/year, assuming a return-flight requirement of 3 tons/flight. Consequently, if LOX supplies were offered for sale in LEO at a competitive price, this would represent a large and rapidly growing potential market.

The LEO price at which LOX supplies would be attractive to Kankoh-maru operators is much higher than the price on Earth, due to the high cost of transportation from Earth. However, it should be noted that delivery of LOX from the lunar surface to LEO using chemical propulsion is not likely to be competitive with launch from Earth, due to the cost of delivering fuel to the lunar surface from Earth (5). Consequently launch using solar-generated electricity driving a linear-motor launch system will be required. This will itself be a substantial capital investment, raising the initial cost of starting such a supply, but enabling very low operating costs to be achieved due to the absence of fuel costs. In order to illustrate the potential scale of this business opportunity, Figure 1 shows the demand for LOX in LEO based on the JRS scenario of LEO tourism development.

In order for vehicles in LEO to obtain LOX they will need to rendezvous and dock with a suitable supply site. Consequently, from logistical considerations, we assume that only those flights that dock with an orbital facility such as a hotel are candidates for sale of lunar-derived LOX (LLOX). Provisionally we assume that this represents 75% of Kankoh-maru flights. We also assume that only 1/3 of this demand is supplied in LEO, since without detailed analysis it is unclear what proportion of Kankoh-maru's return-flight oxygen requirement could be supplied on orbit, due to the requirement for emergency de-orbit capability even before rendez-vous (6). We also ignore hotels' demand for oxygen for air-supply and orbit-boosting propulsion, although this could be substantial. From the resulting demand for purchases of LOX in LEO, and from the known technical requirements for production of LOX on the lunar surface (4), we can estimate the scale of power generation facilities required on the Moon and their growth rate following the JRS scenario, as shown in Figure 2.

Figure 1: Annual use of LOX for return from LEO in JRS scenario
Figure 2: Growth of lunar LOX (LLOX) production facilities

A cost of $1m to launch 5 tons of LOX to a supply depot in LEO using "Kamotsu-maru" (the cargo-version of Kankoh-maru) provides a rough estimate of the maximum LEO price that could be charged for LLOX. Based on this, the commercial revenues that could be earned by lunar surface operations including mining, liquid oxygen production, and linear-motor launch can be estimated, as shown in Figure 3.

The above analysis is only preliminary, and makes many simplifying assumptions. However, it reveals a potentially very large commercial opportunity for lunar industries supplying the LEO tourism market. In view of the fact that no other substantial commercial opportunity has been proposed to date, it would seem very desirable that this analysis should be repeated in greater detail by those with more expert knowledge of the many factors involved - lunar materials processing, linear-motor launch from the lunar surface, orbital storage of LOX, tanker flight operations, passenger launch vehicle operations, orbital hotel propulsion and others.

Figure 3: Potential commercial revenues from supplying LLOX to LEO

This paper has estimated the scale of the potential commercial demand for LOX supplies in LEO, based on the JRS space tourism business scenario and on the price at which such supplies might be attractive to Kankoh-maru operators in LEO. Based on this, the potential growth of commercial revenues earned by lunar surface operations supplying LLOX to LEO has been estimated as growing by more than 1000 tons/year/year, generating commercial revenues for lunar surface activities of as much as several $billions per year. It will be the task of entrepreneurial companies to determine profitable means of satisfying the potential demand within the scale of investment that can be raised commercially.

Thus the supply of lunar-derived oxygen to passenger-carrying launch vehicles and passenger accommodation in LEO at prices reflecting the high cost of launch from Earth may be the first significant commercial market for lunar products, and would seem to be a uniquely promising business opportunity for lunar surface activities. Consequently, the development of orbital tourism may have major implications for lunar development and hence for the growth of space activities beyond Earth orbit, and research on lunar industrialization should be focused on this application.

  1. Shimizu, 1996, " Lunar Resource Utilization: Oxygen Production", Shimizu Corporation, Space Systems Division, Tokyo.
  3. M Nagatomo (ed), 1994, 1995, Special Issues on Space Tourism, Journal of Space Technology and Science, Japanese Rocket Society.
  4. D Bullard et al, 1996, " Lunar oxygen production in a hydrogen "cold" plasma", Proceedings of SPACE 96, ASCE, pp 1188-1197.
  5. G Hudson and M Hyson, 1985, " A single-stage vertical takeoff and landing space transport for lunar settlement establishment and resupply", AIAA Symposium on Lunar Bases and Space Activities in the 21st Century.
  6. T Williams and P Collins, 1997, "Orbital considerations in Kankoh-maru rendezvous operations", Proceedings of 7th ISCOPS, AAS in press.
P Collins, 1998, "Tourism in Low Earth Orbit: The Trigger for Commercial Lunar Development?", Proceedings of Space '98, ASCE, pp 752-756.
Also downloadable from in low earth orbit the trigger for commercial development.shtml

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