The next big step in expanding human presence into the solar system will be taken by exploration and science crews on the Moon and Mars. Built upon the technology foundation of Space Station Freedom, this ambitious undertaking will advance the state of our spacefaring technology. Beneficiaries will include both terrestrial and spaceborne industries. By learning as they go, exploration pioneers will pave the way for subsequent steps, including the most far-reaching one of all: enabling large numbers of ordinary people to visit live and work in space. The defacto presence in space of many people, following the path blazed by the pioneers and using their tools, can provide the social continuity and economic spark to ignite our transition to a true spacefaring civilization. Inevitably, the place where this transformation will start is low Earth orbit ( LEO).

LEO is physically close to home, and cheaper to get to than anywhere else in space. LEO is thus a prime location to conduct space life science research, to develop new or improved materials and processes in microgravity and hard vacuum, to study the geology, climate and biosphere of Earth, to operate astronomical observatories without atmospheric interference, and to assemble large vehicles for interplanetary exploration. Indeed, various governments and some companies are doing or planning all these things.

But the most banal activity we can conceive for LEO -- just being there and looking out the window -- may ironically hold the greatest promise for transforming our world. LEO proffers the most meaningful of all the solar system's spectacular scenery. The view from LEO, in fact, is so breathtaking, so beautiful, and so varied that every astronaut has, when asked, claimed to have been changed by it. This well-documented psychological shift in perspective is called the Overview Effect (5). It resembles but is stronger than the feeling, occasioned by air travel, of detachment from immersion in the details of the world below. It increases in intensity with both duration in space and distance from Earth; Apollo lunar astronauts have reported the most focused experiences so far. Earth is seen as a fragile system immersed in infinity, a natural wonder far more significant than any human conflict. From LEO, no borders and few human works are visible. From the Moon, all of Earth can be blotted from view by holding up a thumb, and the passage of time seems slowed. From Mars, Earth will appear as just a bright blue star.

Invariably, space travelers gain a deepened perception and appreciation of the "place" of humans, and Earth, in the universe. They return to Earth enlightened about, and even committed to ecological stewardship and international peace. Such a unique transformational experience, if shared by many people, could be invaluable in bringing about a more mature, global, coordinated and timely approach to the problems we face on Earth at the end of the 20th century. Returning participants relating their experiences and information media are somewhat capable of sharing the overview experience. The United States has begun flying policy-makers, and the Soviet Union has begun flying journalists. whole-world pictures of Earth taken by Apollo crews, geosynchronous satellites and the Jupiter-bound Galileo probe are popular and powerful tools for sharing the experience, as are IMAX(r) format films and folio-format books (3).

However, the Overview Effect is attained directly only by being in space. For the overview to become a fundamental part of the world's way of thinking, many more people must have the chance to experience it directly in LEO. Providing such a unique transformational opportunity for large numbers of people is the surest way to bring the far-reaching benefits of a space overview back down to Earth. And because of the sheer experiential power of a trip to LEO -- the ride, the view, the novelty, the risk, the exhilaration -- providing that opportunity should prove profitable as well.

Conventional wisdom holds that space travel is too special, too risky, and certainly too expensive for ordinary people to experience it. Only the perspective of history can dispute the finality of that hasty conclusion. No doubt in 1912 it seemed that the same restrictions applied to aviation. Only two generations of progress gave us airplanes capable of carrying a half-thousand people over the ocean, powered by engines each producing as much mechanical power as the entire industrial output of 11th century Britain. The challenge of space travel is to our technology what the challenge of air travel was to that of our parents and grandparents. Given a reason for people to travel in space, and technology based on the tools and knowledge developed by government-sponsored programs, commercial space travel can happen. Many current efforts are pointing the way.

The first manned launches, using expendable ballistic missile boosters borrowed from the arms race, were rough, high-acceleration rides fit only for test pilots. Re-entry in cramped ballistic capsules was also a crushing, rattling experience. But a new incarnation of this old method is represented by the NASA Personnel Launch System (PLS) program. As currently envisioned PLS would be a small vehicle, shaped like a capsule or blunt lifting body, that would carry eight passengers without flight crew on top of an expendable rocket, such as the National Launch System (NLS) vehicles being jointly developed by NASA and the Department of Defense. Because the PLS would also return people to Earth, it might be used as an escape vehicle for Space Station Freedom as well. Although small, the PLS' simple operation might allow it to become the first privately operated space transporter, and larger versions could follow (2).

The winged space shuffle (STS), albeit noisy on ascent, provides a much smoother and gentler ride, both up and back down, than earlier boosters. It carries up to five passengers in addition to two crew. However, this first reusable spaceship, albeit well-seasoned by a decade of use, is developmental. Its performance margins are too slim and its maintenance requirements too finicky for use as a general transport.. Conceptually, though, we can easily envision a derivative spaceplane, launched ballistically by a booster and re-entering by unpowered aerodynarnic glide, less efficient and more robust than the STS. Such a vehicle might carry about 50 people to LEO and back.

Currently industry is studying Single Stage to Orbit ( SSTO) vehicles for the Strategic Defense Initiative Organization. These are launchers that would burn high-performance propellants (liquid oxygen and slush hydrogen) in rocket engines to attain LEO without jettisoning inert weight along the way. Three competing concepts use vertical takeoff and landing ( VTVL), vertical takeoff and horizontal landing ( VTHL), and horizontal takeoff and landing (HIUL) configurations. Because these vehicles would not drop hardware on the way to orbit, they would have less performance but be simpler to operate than the STS. Chief program goals are delivery of about 9 t to Space Station Freedom, with a ground turnaround time of about a week. Although such a vehicle could only deliver about eight passengers to orbit, larger versions would also be possible (4).

A step up in sophistication would be to increase the payload fraction to orbit by using the atmosphere as a propellant resource on ascent. The goal of the National Aerospace Plane (NASP) program is to develop a HTHL vehicle which derives its oxydizer during ascent from the air it moves through, instead of bringing it along from the ground in liquid form. The technological challenges here are to make jet engines which can perform at virtually all altitudes, and to make lightweight structures which can take the heat of atmospheric friction for long flight times.

A final step forward in propulsive capability might be attainable by leaving the energy source itself on the ground. A chemical rocket works by converting the energy released from chemical reactions (as heat) into high velocity of the expelled products, by expanding the expelled flow through a nozzle. The energy source is carried onboard in the form of the chemical reactants. But suppose the propellant gets its thermal energy from an offboard source. This is the idea behind laser rockets, including the ground-launched type envisioned by Arthur Kantowitz. A high-power laser would vaporize layers of propellant off the stern end of the launcher to provide thrust. Water turns out to be an efficient propellant, and ice may be an effective form for vehicle integration. Much work remains to be done; so far only numerical simulations have been performed.

Systems using propulsive and aerobraking technologies are the best we can credibly anticipate for ferrying people between Earth and LEO for a long time. However, we must also mention the most advanced mechanism yet imagined for leaving a planet, because its development would change space transportation as fundamentally as the automobile changed ground transportation. That, of course, is the space elevator, a tether system so long as to reach from an anchor point at Earth's surface all the way into space, either to a cable track in low orbit (going all the way around the planet) or to a station in geosynchronous orbit (and continuing that far beyond). The problems of deployment, dynamic stability and catastrophic failure are mind-boggling, and the enabling problem of an adequate tether material is so far unsolved. if possible eventually, however, the elevator would permit trips to and from LEO for essentially the cost of electricity, plus maintenance and the amortized cost of the system!). That and the scheme's avoidance of propulsive effluent would then allow traffic volume between Earth and space to become enormous.

Economics of Attaining Large-Scale LEO Overview

The reason that we do not already have large numbers of space travellers has little to do with technology availability, nor even with the risks of using the technologies we have. Rather, it is the prohibitive cost, which so far allows only governments to fly people into space. Although we are beginning to see sponsored crew participation in government flights (the recent Soviet flight of a Japanese reporter* is an example), the fees charged recover neither the infrastructure investment costs nor the system operations costs allocatable to that individual.

Most discussion of the high cost of space travel has centered on the transportation itself, and clearly this is the first choke. Analysis (6) has shown that launch costs can be reduced by over two orders of magnitude with the technologies we are using already. The key is high traffic volume. Two other secondary but important preconditions are long hardware life with full re-usability (requiring generous operating margins) and resource-efficient operations (including quick turnaround and small maintenance crews per vehicle). All three of these enabling conditions characterize the commercial airline business.

Our purpose in this paper is to investigate the second choke: accommodating high-volume passenger traffic in space. Where will space tourists go, and what will they do? Large-volume, intercontinental, air passenger travel would not have developed if all passengers could do was fly to Europe, look out the window at the Eiffel Tower while eating a French meal, and fly back without stopping! Large volume presupposes a reason to travel, and most of that reason depends on the nature of the destination. Weightlessness, the novelty of "spacewaiking", and time to appreciate the spectacular, ever-changing overview of the ever-changing Earth below will all compensate for comparatively small and simple orbital tour destinations. However, before we examine some functional requirements for LEO hotels, we need to see if the proposition makes any economic. sense. Specifically, we need to see if the cost can be bootstrapped down to allow ever-increasing numbers of people to afford tows. Our simple analysis uses 1991 dollars.

In figuring the cost of a basic tour package, we must include the cost of the passage, the amortized cost of the orbital hotel facilities, the cost of hotel operations, and profit. We begin with the passage. Assume that an average traveler's weight allocation (person and luggage) totals 200 lbs (mass = 91 kg). Figure 1 shows some reference per-pound costs for some of the launch options discussed in the last section. With the exception of the commonly quoted STS value, all are projected. These are flight operations costs only, not burdened by amortization of the launch system or its development. This is the way the government quotes launch cost. Assume that the vehicle development has indeed been carried out already by the government, which is certainly the cast for STS, NLS and NASP technologies. Assume now for a commercial enterprise (analogous to airlines) that the cost of amortizing the re-usable vehicle fleet roughly equals the operations cost per launch. Taking the high end of the NLS-class range will make the transportation portion of total tour-cost roughly commensurate with the other components. Thus, doubling from Figure 1 to capture fleet amortization and launch operations, we estimate the burdened cost of a passenger flight ticket at $200,000.

Next we account for amortizing the capital cost of the orbiting hotel facility. Since such a facility has never been designed, costing is done by analogy, parametrically. Space hotel systems comming on line in the first decade of the 21st century would be based on two sources: (1) Space Station Freedom systems by then accumulating operational experience in space; and (2) next-generation, long-distance, long-duration equipment then being qualified to meet the driving crew support requirements for the Space Exploration Initiative (SEI). Assume that the cost of the First such Mars-class module (including its development) is roughly $2B, and can support 6 people. To estimate the cost of a production module, we scale down $2B by the ratio of production-unit cost to development cost for another commercial, large, complex, pressurized habitable flight system: the 747. In rough numbers, a 747 to carry 500 people costs $150M, whereas the design took about $5B to develop and qualify; the ratio is 0.03. A production-unit space habitat module for 6 people might then cost about $60M.

But we can take advantage of some economies of scale. The heavy-lift ETO rockets appropriate for SEI could easily lift modules at least twice as large and heavy as this Mars-class model. Building a hotel out of fewer, larger modules would both save costs and permit larger communal spaces important for functional reasons discussed later. Furthermore, a government space facility or spacecraft hab module is chock-full of heavy, bulky science and applications equipment not required for a hotel, so a living module sized for 6 people on a 2 yr Mars mission could accommodate more guests for their short stays in LEO. Let us collect such cost benefits by assuming the specific cost of production-line habitable facilities to be $30M per 6 people, or $5M/person.

For a reference example, imagine a modest initial hotel to accommodate 50 guests enough to comprise a diverse but collegial tour group. Assume that the average flight brings and returns 45 guests, that the hotel has full occupancy continuously, and that the modal tour time is three weeks, but that a few guests schedule longer stays, in multiples of 3-wk increments. 17 flights/yr are required.

The base hotel hab facility cost is then 5 x 50 = $250M. Now say that the support utilities (such as external power, thermal rejection, attitude-control, reboost, communications and debris-protection systems) and infrastructure (such as simple, production-line Earth-return shuttle pods and ground support dedicated to the hotel operation) inflate this cost by 50%. The facilities also need to support a small hotel staff. And because this is a resort hotel (and not a government space station), some "amenities" discussed later are required to make it viable. Assume that these two cost penalties amount to an additional 20%.

So far this amounts to 1.2 x 1.5 x 250 = $450M, which is roughly 25% of the estimated $2B development cost for the original, government-sponsored Mars-class-habitation system. Now although the Mars system development is assumed to have been paid for by the government, there will be a "spinoff development" cost to derive the commercial system from the original. Let us assume that most of this is borne by this first commercial hotel, and amounts to 20% of the $2B original, or $400M. This may be excessive, but that depends on how fast the LEO hotel business grows, and the physical longevity of the hotel systems. However, our conservatism allows this scaling factor to collect other, unmodeled facility costs -- a sort of cost "growth margin". We end up with a total LEO hotel facility cost of $850M. Assuming the whole facility weighs about 500 klbs (mass about 230 t), and that the insured, unmanned launch cost is figured at the same rate we used for the passenger flights, the cost to launch it into LEO is $250M. The total burdened capital cost on orbit is thus $1.1B. If that capital cost is amortized over 10 yr, then the capital amortization share borne by a typical 3-wk passenger tour package amounts to about $130,000, which is 65% as much as our estimated flight ticket.

Next is the hotel operations cost. Operations includes hotel guest services (including meals), insurance, maintenance, supplies and staff compensation. Figure 2 tallies an estimate of the minimal staff expected to be adequate for this on-orbit operation. A larger hotel would be able to enjoy a more economical staff/guest ratio. Staff compensation could probably be limited to health and retirement benefits, avoiding salary per se because of the likely extreme competition for job openings. The annual cost to launch an additional 10% of the total hotel mass (for supplies, spares and growth), using our standard rate, would be only $25M. Let us assume a total operations cost about four times higher, about $110M/yr. This results reasonably in a cost per tourist ticket for operations equal to the ticket's share of capital amortization: $130,000.

Figure 2 - Minimal Staff for 50-guest LEO Hotel

Our total collected cost for transportation, capital amortization and operations allocatable to each tourist ticket is then $460,000. The investors in this unprecedented LEO hotel project have assumed a large financial risk, without the benefit of any statistics on success probability. To compensate them, let us assume a 20% profit margin, which would start showing payback after four years of operation (assuming an 8% discount rate). When burdened with the profit, our base tourist ticket costs $552,000. Clearly, only very wealthy people could pioneer the LEO hotel business by affording such an extravagant trip. Of those, however, some could and would undoubtedly repeat the experience. Over the reference 10 yr hotel amortization time, let us assume that 85% of the patrons are guests on their first trip. The question then becomes: are there (.85)(10)(17)(50) = 7,225 people in the world who, over a 10 yr span of time, would spend over half a million dollars each to be able to live in space for three weeks, experiencing first-hand its unique sensations and incredible view? A more pointed counter-question suggests itself: aren't there?

Our quick "sanity check" of the economics of LEO hotels does not at all prove their practicality, but it does indicate that further investigation is warranted. Once the viability of the LEO tourist market is appreciated, and once both man-rated launch and in-space operations Systems become truly purchasable, clever entrepreneurs will find ways to do better than our example, sharing risk and amassing the financing to take on such projects. Indeed, some already seem to be planning -- Shimizu Corporation envisions 100-person LEO hotels being profitable within a few decades. Even if development is more expensive and payback slower than we have proposed, not all companies expect as instant gratification as does American industry. For example, the Japanese view may be summarized by the quotation, "Most of our companies are hundreds of years old. Twenty or thirty years is nothing to us" (1). Once the first LEO hotel proves the concept, more will follow. Different hotels can focus their carefully-metered "amenities" margins in different ways, leading to specialization and increasing supply variety. Supply will increase, ticket costs deflate, and new population reserves of demand open up. flight rates will grow. As with commercial air travel, eventually moderate incomes will suffice to afford stays in Earth orbit.

Hotel LEO

The explicit desigu of an orbital hotel like the one assumed in our reference example is beyond the scope of this paper. what we can do is begin to identify some of the basic requirements such a facility might meet, and describe what it might be like there.

Safety - Maintaing safety is the dominant underlying principle throughout the hotel. In space, everyone is responsible for everyone else's safety, for it only takes one mistake or oversight to jeopardize the lives of all. Pre-flight liability waivers, albeit required, are no substitute for adequate preparation, and no consolation in the event of a contingency. Guests are thoroughly familiarized with safety rules, and they practice key procedures, on the ground prior to their trip. By the time they arrive at Hotel LEO, they all understand the inherent dangers of space travel. The hotel is desigued with all life-critical Systems two-fault tolerant. Fire hazards are strictly minimized, and armoring against orbital debris is state-of-the-art.

The onboard infirmary can accommodate up to 5 people continuously, and has full diagnostic and minor surgical capabilities, a decompression treatment chamber, and high-bandwidth interactive tele-presence links with groundside medical centers. The overwhelming percentage of treatments is for mitigating symptoms of the two-day adaptation to free-fall, which remains an unavoidable hurdle for about 1/3 of all space travelers.

Transfer of guests and staff into the hotel is "shirtsleeve", after direct berthing of their ETO vehicle to the hotel. After three weeks in orbit, experiencing free-fall and the spectacular view of earth below, guests return aboard the vehicle bringing the next tour group. The arriving guests are greeted by the departing guests at a short reception. in the Main Lounge (most of those who will lose two days to the effects of Space Adaptation Syndrome won't know it for another several hours). Watching the departure of the ETO vehicle is always an event of great exhilaration for newcomers; watching the arrival of the next one three weeks later to take these now-seasoned travelers back home is just as interesting, but induces mixed emotions of anticipation and regret. Throughout a stay aboard the hotel, a rapid return to Earth is possible using assured-return shuttle pods capable of de-orbiting, reentering and gliding to a landing at desiguated worldwide sites autonomously. Their use is primarily for severe medical emergencies, but they can be used -- at a stiff premium -- for terminating a trip for any personal reason. Sufficient pods are berthed to the hotel for the immediate evacuation of all guests and personnel in the event of a catastrophic system failure.

Accommodations - Stateroom accommodations aboard Hotel LEO offer visual and acoustic privacy, with comfort and service very different from, but equivalent to, Earth's finest luxury resorts and appropriate for orbital conditions. Both the physical setting and activities onboard Hotel LEO are unique, enhancing guests' appreciation of their novel experience. Rooms are arranged with volume, rather than floor space, in mind. A stateroom for two can be only a fraction as large as on Earth, since walls, ceilings and floors lose their familiar meaning. Beds in orbital microgravity no longer support the users! weight, but merely restrain them from floating about the suite in the forced-air currents while asleep. Consequently, orbital beds are more like padded alcoves, functioning also as chair and couch, adaptable for the activity intended by reconfiguring restraint cushions. All furnishings are well-crafted, but extremely lightweight, made of aerospace materials and efficiently stowable.

Each guest suite is equipped with built-in telecommunications and entertainment media, and stowage provisions for personal effects. Wall surfaces, padded for comfort and safety with high-quality, non-flammable fabrics in a variety of colors and textures, are studded periodically with mobility handles and restraint aids. The focal point of each suite is its own Earth-facing window, equipped with a shutter for sleep periods and surrounded by arm and leg restraints for comfortable, long-term viewing. This quintessential feature of Hotel LEO gives an otherworldly and unforgettable meaning to the expression "a room with a view". Each room's occupants can experience with personal significance having a private window on the whole world below. Figure 3 is a sketch illustrating what such staterooms might be like.

Facility costs of Hotel LEO are kept manageable by conserving habitable volume and consolidating functions which require sophisticated utilities. Thus a surprising aspect of this luxury hotel is its dormitory-style wetrooms. Each serves a cluster of suites, and provides microgravity toilets, washstands and suction-drying showers. The sounds of the arcane plumbing and air-conditioning machinery are insulated as much as possible from guest suites. Operations costs are kept reasonable by recycling all water and oxygen, and most of the complex organic wastes as well. This minimizes the amount of resupply mass needed. The high-quality water is reprocessed from cabin air condensate and urine, and all the food except gourmet meats and condiments is grown right at the hotel in intensive-agriculture modules, using recovered nutrients. The cuisine is simple, but expertly prepared in an unusual kitchen. Fresh specialty items and other hotel consumables arrive on the passenger vehicles bringing a new group of guests every three weeks, as well as on periodic cargo delivery ffights. The mechanical and biophysical functions which make Hotel LEO possible were developed and continue to be improved by the pioneering technologists of the government's Space Exploration Ininative.

Activities - Hotel LEO does its best to accommodate the desire of its guests to experience fully the adventure and beauty that astronauts and cosmonauts alone knew for decades. Weightlessness, the view of Earth below, the black void of space, and even the everyday acts of eating and washing up, are new experiences in space, and are in fact the primary reason most want to make this trip. But the hotel also provides activities to let large groups of space travellers function socially. As resorts on earth typically sponsor structured schedules of events that allow people to come together, so does Hotel LEO. The hotel provides a large, open volume for scheduled group events like concerts, theater, dance, microgravity athletic competitions, and conference meetings, all of which can be interactively tele-videoed with the ground. In this way, not only can the experience of working in space be shared with those on Earth, but so can the experience of actually living there.

Guests expect to see what makes this unique hotel work, as long as it doesn't interfere with their comfort. (Few consider that the motivation to keep their activities from interfering with the smooth operation of the spacecraft is stronger.) Public spaces are therefore arranged not only to take physical advantage of circulation intersections at module junctions, but also viewing advantage of interesting hotel support activities like food growth and preparation, mechanical maintenance and logistical operations. Without any doubt though, the most popular social activity aboard Hotel LEO, just as privately, is Earth-viewing, especially watching the darkside lightning storms, and the spectacular sunrises and sunsets occurring every 45 minutes. Major social spaces such as dining areas and lounges have Earth-facing windows much larger than those in the staterooms. Figure 4 is a sketch of what one of the larger public spaces might be like. Having dinner, sharing a drink with a friend, or listening to a live musical performance while the Himalayas, Indonesia and South America pass below, are surely some of the most memorable experiences available to 21st century travelers. Also popular, however, are the out-facing observation lounges, equipped with computer-aimed telescopes for seeing the Sun, Earth's Moon, and the strikingly bright, steady lights of other planets and myriad stars.

Those who can afford to spend three or more weeks in LEO may also want to purchase tour package "options" to experience the thrill of spacewalking. Training is provided prior to Earth departure. Once fitted with suits, most spacewalking guests are escorted outside the hotel in groups by experienced staff monitors, and tethered securely to the structure. A more expensive option includes time alone at the end of the orbit-forward boom, enjoying unencumbered the spectacle of speeding silently over Earth's curved horizon below. Another includes an untethered excursion with propulsive backpack under computer control. The experience of utter isolation in becoming your own tiny spacecraft, separated from everything reassuring by vacuum, and from Earth's surface by hundreds of miles, is worth every dollar of premium. Other tour options include visits to co-orbiting satellites in shuttle pods piloted by hotel staff, and of course extended hotel stays in multiples of three-week intervals. One of the most popular options is booking a reservation with a group including a'telebrity scientist, who acts as tourguide for groundwatching, seawatching, cloudwatching or spacewatching. Many guests combine their trip with a pivotal event -- honeymoons are common -- to justify stretching their trip budgets as fully as possible with options.

Staffing the Hotel - The hotel staff are not professional "astronauts" as they used to be known. Rather they are dedicated, highly proficient service and operations professionals who love being in space. Although skilled in all aspects of safe and contingency spacecraft operations, their primary functions are service, instruction, meal preparation, program direction, atirninistration, physical plant maintainence and other occupations important for the resort business. They are all thoroughly cross-trained in multiple emphasis areas, and able to guide guests across Earth's features, instruct them in the use of hotel systems, monitor their observance of safety rules, and respond to contingencies according to well-drilled procedures. In essence, they are special-purpose flight attendants, whose visible function is to help, whose invisible function is to keep the hotel operating smothy, and whose major responsibility is to ensure the safety of the guests. The on-orbit staff is as small as possible to limit overhead costs; some critical functions, like plant tending and processing, rely heavily on advanced automation to limit staff requirements at the price of requiring capable maintenance engineers.

Our development as a truly spacefaring civilization will be measured not by the number of places we visit, but rather by the numbers of people for whom traveling in space becomes familiar. Focusing on low Earth orbit leads simultaneously to the largest traffic potential, the most useful trip durations, and access to the most moving scenery in the solar system. The societal benefits accruing from propagating the Overview Effect attainable through spaceffight among increasing numbers of people are anticipated to be dramatic. Reduced transportation costs no higher than those originally targeted for the Advanced Launch System appear enabling. Full launch system re-usability and simple turnaround operations can set the stage for the high flight rates that would reduce trip costs substantially. Resort hotels to support extended stays in low Earth orbit are technically feasible using technology being developed now by the U.S. Space Program. Their economic practicality as commercial ventures appears achievable eventually, although the first generation of such resorts will necessarily cater to the very wealthy. Subsequent market growth would allow reduced rates, resulting in expanding access for more people. Large hotels can benefit from economy of scale, but represent substantial capital investments probably requbng the pooling of many entrepreneurial resources. Much room for innovation exists in designing ways to adapt emergent space hardware systems to take cost-effective advantage of unique orbital conditions for the purpose of hosting ordinary people in LEO. The extensive variety of activities available to space travelers on multi-week visits into Earth orbit can be turned to advantage in developing successful, profitable resort ventures.

1. A R Dalby and A R Hogan, Feb 1991, " A Rising Sun Over Earth?", Ad Astra.
2. L David, Feb 1991, " PLS: a mini-space-liner for people on the go", Ad Astra.
3. K W Kelley (ed), 1988, " The Home Planet", Addison-Wesley and Mir Publishers.
4. G Payton and J M Sponable, April 1991, " Singe stage to orbit: counting down"; also Designing the SSTO rocket Aerospace America
5. F White, 1987, " The Overview Effect - Space Exploration and Human Evolution", Houghton Mifflin Company.
6. G R Woodcock, May 1986, " Lower bounds on launch cost", International Space Development Conference