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Corporate Groupthink: The Main Obstacle to an Affordable Lunar Base
Space Policy 50 (2019) 101344
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Corporate Groupthink: The Main Obstacle to an Affordable Lunar Base David Ashford 1 Bristol Spaceplanes, 3 Forest Hills, Almondsbury, Bristol, BS32 4DN, United Kingdom
a r t i c l e i n f o
a b s t r a c t
Article history: Received 3 August 2019 Received in revised form 19 September 2019 Accepted 1 October 2019 Available online 1 November 2019
This article describes a launch vehicle development roadmap that uses only proven technology and that could lead to a thousand-fold reduction in the cost of sending people to orbit within about 15 years. It could reduce the cost of the first lunar base by very approximately ten times. This would clearly revolutionise spaceflight and create a new space age. The roadmap involves a combination of full reusability, aeroplane-like vehicle design and high traffic levels, especially from space tourism, to provide economies of scale. This line of development could have started some fifty years ago, and the failure to do this has led to a corporate groupthink that is probably now the biggest obstacle to progress. © 2019 Elsevier Ltd. All rights reserved.
Keywords: Low-cost access to space Space tourism Spaceplanes Reusable launch vehicles
Contents 1. 2. 3. 4. 5.
6. 7. 8. 9.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Historical perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Historical exemplardthe Lockheed NF-104 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Ascender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Spacecab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5.1. Design logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5.2. Suborbital operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5.3. Orbital operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 On to the Moon and Mars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Business case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Declaration of interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction The fiftieth anniversary of the first manned lunar landing (and the forty-seventh since the last man left the moon) is a good time to reflect on how best to revisit our closest heavenly neighbour. If the Moon was all that worth visiting, why such a long hiatus? There are perhaps two answers to this questiondcost and motivation.
1
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The Apollo programme cost some $25 billion at the time, which is equivalent to roughly $150 billion today or about seven times the total present NASA annual budget. It needed an extremely strong motivation to obtain such a huge sum of money. This was provided by the pressures of the Cold War. The USA saw itself as being in a desperate struggle with the Soviet Union for global domination and even for survival. The U.S. effort was kicked off by President Kennedy's famous speech In May 1961, just 6 weeks after Yuri Gagarin's historic first manned flight to space, when he galvanised the nation by saying, “If
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we are to win the battle that is going on around the world between freedom and tyranny, if we are to win the battle for men's minds … I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to Earth.” The opening phrases of this speech show that he was more interested in demonstrating U.S. technical superiority than in space exploration per se. This urgent political motivation is largely lacking today. Some U.S. politicians are trying to build up the Chinese lunar programme as a threat to justify increasing the NASA budget, but the public mood is far less receptive to this approach than it was some 60 years ago. The USA might be wiser to go back to the Moon in its own time, and if the Chinese get there first to gently point out that they achieved the same feat more than 50 years ago. The space programme is thus in urgent need of far lower launch costs and new motivations. This article summarises, as the basis for discussion, a straightforward way of providing both using only proven technology, as worked up over the years by Bristol Spaceplanes. The lower costs come from developing an orbital spaceplane designed to satisfy potentially large new commercial markets, especially space tourism. This spaceplane is an updated version of the 1960s European Aerospace Transporter concept (see next section), which was considered feasible at the time but which has never been built. The combination of full reusability, aeroplane-like design and the high traffic levels arising from these new markets would enable an airline service to orbit with greatly reduced costs. The motivation comes from the compelling commercial business case for developing such a spaceplane. The rest of this article describes the historical background to spaceplane development and how corporate groupthink has evolved to become the greatest barrier to progress. It then discusses what should be the leading design features of the first orbital spaceplane, a historical exemplar and a progressive development sequence of launch vehicles leading to the desired goal. Bristol Spaceplanes projects are mentioned only when there are no other suitable exemplars.
(with a payload of 20e30 tonnes) than the European designs (2e4 tonnes). Thus when President Nixon imposed a budget cut, NASA could no longer afford to develop such a large fully reusable vehicle. Rather than develop a smaller but still fully reusable aeroplane-like launcher, NASA decided to forego complete reusability, and the vehicle as built was largely expendable. It was therefore as expensive and risky to operate as the throwaway launchers that preceded it. This history seems to have created organisations and habits of thought that repeatedly reinforce the habit of expendability. Even now, most major space agencies are promoting the development of expendable launchers. The failure to develop orbital spaceplanes when they first became feasible in the 1960s has led to a cultural chasm between the aviation and space industries. Few launcher designers really understand airliners and vice versa. The aircraft industry does not seem to appreciate the opportunity that it has to take over space transportation from Earth to low orbit. This corporate groupthink is probably the biggest obstacle in the way of spaceplane development today.
2. Historical perspective
The first vehicle on the proposed development sequence is the Bristol Spaceplanes Ascender small suborbital spaceplane, Fig. 3. To climb higher than the NF-104, more rocket propellant is needed. By happy coincidence, the amount needed to reach space height, following a jet climb to around Mach 2 (about 40% of the aircraft weight at rocket start), is just achievable within existing technology boundaries. (A lower jet speed would require the rocket engine to do more of the acceleration and climb, which would need even more propellant because rockets use between ten and twenty times more than jets for a given thrust and time.) Ascender is the only suborbital spaceplane currently being proposed that uses jets to supersonic speed. It is like a secondgeneration NF-104 designed from scratch to reach space height. It could have been built in the 1960s. Ascender is like a quarter-scale Concorde with two seats, a simplified wing shape and fitted with two jet engines and a rocket engine. A typical trajectory is shown in Fig. 4. Ascender accelerates to Mach 1.8 using its jet engines only. The rocket engines are then started, and it pulls up to a climb angle of 70 . It then accelerates on this steep climb to a speed of Mach 3.2 at a height of 53 km. The rocket propellant is by then used up, and the aeroplane carries on unpowered under its own momentum to a height of just over 100 km. Ascender then descends under the influence of gravity, re-enters the atmosphere, pulls out of the dive, restarts its jet engines and flies back to the aerodrome from which it started. The passenger would see at one time an area the size of England and would experience about three minutes of
During the pioneering phase of spaceflight, converted ballistic missiles were used for launching satellites and astronauts. It was clear even then that throwing away one vehicle for each flight could never become economical and, in the 1960s, most big aircraft companies in Europe and the USA had substantial teams studying fully reusable aeroplanes that can fly to orbit (orbital spaceplanes) to replace these expendable launchers. The leading companies in €lkow, Bristol this field were British Aircraft Corporation, Boeing, Bo Siddeley, Convair, Dassault, Douglas, ERNO, Hawker Siddeley, Junkers, Lockheed, Martin and McDonnell. (The author's first job was as a junior member of the Hawker Siddeley team, and his first paper on spaceplanes was published in 1965 [1].) The European projects were studied under Eurospace auspices and were given the generic title of Aerospace Transporter [2]. The guiding mind was the rocket pioneer Eugen S€ anger. Some of the leading designs are shown in Fig. 1. The consensus in the 1960s was that an orbital spaceplane was a highly desirable development that was just about feasible with the technology of the day. However, they were not developed at the time, largely because the budget for advanced prestige projects was used up in the USA by the Cold War race to the Moon and in Europe by Concorde. It is less easy to explain why orbital spaceplanes have not been developed since then. In the 1970s, the early designs of the Space Shuttle were indeed fully reusable, but this project was much larger
3. Historical exemplardthe Lockheed NF-104 Of aircraft that have actually flown, the closest to those described later is the Lockheed NF-104, Fig. 2. The basic Lockheed F104 Starfighter was a first-generation Mach 2 fighter that first flew in 1954. In 1962/63, three F-104s were converted for training astronauts by adding a rocket engine to boost its maximum height. They were given the designation of NF-104. The conversion was successful, and it reached a height of 120,800 ft (36.8 km). It reached Mach 2 on jet power before the rocket was started. The F-104 was a tightly packed fighter aeroplane with little spare volume for rocket propellant. This limited its maximum height to about one-third of the 100 km usually considered as being the boundary of space. 4. Ascender
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Fig. 1. European Aerospace Transporter (Orbital spaceplane) projects of the mid-1960s.
weightlessness. This is a suborbital trajectorydorbital flight is discussed later. Ascender would have a wide application for various types of space research and for carrying passengers on brief space experience flights. Ascender uses only proven technology and could be flying in about five years. Flights to space in Ascender would become routine after a few years in service. (As routine as flying the NF-104 would have become if there had been a need to put it into operational service and build it in significant numbers.)
platforms towed into position by ocean-going tugs, with helicopters or small boats for everyday supplies. Two of these three elements already exist. Heavy-lift launchers have been in service since the Apollo of the late 1960s, and orbiting platforms (space stations) have been in service for nearly as long. One heavy-lift launcher under developmentdthe SpaceX BFRdwill be fully reusable, which will help to reduce costs.
5. Spacecab Ascender is a stepping-stone to the second vehicle on the sequencedthe two-stage Spacecab spaceplane, Fig. 5. The lower stage is like Ascender but is scaled up by a factor of four to about the same size as Concorde. Even if it were still in production, Concorde itself would not be suitable for such a rocket conversion because the loads and speed would be well outside its design limits. An all-new vehicle will be required. However, the required design changes compared with Concorde would all be straightforward and much Concorde technology could be used. The upper stage can be either a module carrying 20 passengers and that remains attached for a suborbital flight, or a reusable launcher that separates at Mach 4 and carries on to orbit under rocket power with either six passengers or a satellite or cargo of 750 kg. The orbital upper stage version is shown here. 5.1. Design logic Before considering Spacecab operations in more detail, it is worth considering the logic behind the selection of its basic design features. It has long been considered that routine and affordable access to space is the desired goal and that this is best achieved by building a ‘low-cost orbital infrastructure’. This consists of large orbiting platforms for various scientific and commercial purposes, heavy-lift launchers for placing these platforms in orbit and a small launcher for the regular delivery of crews and supplies. This is analogous to the offshore oil industry, which uses large drilling
Fig. 2. A Lockheed NF-104 climbing under rocket power. [US Air Force Test Center History Office].
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Fig. 3. The Bristol Spaceplanes Ascender suborbital spaceplane.
This leaves the small launcher suitable for high-frequency operations as the missing element. The basic design features of this vehicle can be derived using a straightforward logic. The first requirement is that it should be fully reusable. Today's launchers use large components that can fly only once, which is the root cause of the high cost and risk of spaceflight. (There are reusable booster stages and capsules but not yet reusable upper stages launched by reusable lower ones.) To gain insight into the cost penalty of this expendability, consider that the purchase price of a new car is very roughly 1000 times more than the cost of driving it for a few hours. Thus, if cars had to be scrapped every day, motoring would cost roughly 1000 times more than it does. Much the same applies to aviation. The production cost of an airliner is roughly 1000 times more than the cost of operating it on a long-range fight. Thus, if airliners could fly only once, the cost of a flight across the Atlantic would be roughly 1000 times more than it is. There is another major difference between space transportation and commercial air traveldthe former has far lower traffic levels. There are about 100 satellite launches per year compared with some 40 million commercial airline flights. The low launch rate precludes approaching aviation standards of maturity and low operating cost and is largely because of the high costs imposed by expendability. Spaceflight today is limited to government-funded missions and a few commercial applications such as
communications, TV, navigation, Earth observation and weather forecasting. These markets involve essentially using satellites to process and transmit data, and so a high launch cost per tonne is not a major handicap. However, new markets of very large commercial potential, such as space manufacture, solar-power satellites and orbital tourism, require the regular transportation of many tonnes of people and material and are thereby held back by high transportation cost. The new launcher should therefore be suitable for the large new markets to provide higher traffic levels and economies of scale. The new markets, especially space tourism, will require far greater safety than can be achieved by expendable launchers. This means that the new launcher should be designed to airliner standards as far as is practical, as these are the safest flying machines yet built. It should therefore be piloted and have wings for horizontal take-off and landing. These features should also offer better passenger appeal than vehicles that land vertically on a rocket pad. So that existing technology can be used, the new launcher should have two stages, as single-stagers require advanced new airbreathing engines. Finally, to generate large new markets, the lower stage should be able to operate on its own for suborbital missions, especially tourism. In summary, the new launcher best able to reduce launch costs should have the following basic features: It should be fully reusable. It should have two stages. Both stages should be piloted and have wings for horizontal take-off and landing. The lower stage should be able to operate on its own for suborbital missions, especially tourism. It is noteworthy that most of the 1960s European Aerospace Transporter designs had these features and that Spacecab is the only vehicle to have them that is currently being proposed.
5.2. Suborbital operations
Fig. 4. Ascender trajectory.
When the lower stage is used on its own for carrying passengers on suborbital space experience flights, its trajectory would be similar to that of Ascender shown earlier in Fig. 4. The total flight time would be about 40 min.
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Fig. 5. The Bristol Spaceplanes Spacecab orbital spaceplane.
Early suborbital fights would be expensive by aviation standards because of the short life of today's rocket engines and the need for significant maintenance between flights. As operating experience built up and the design matured, the life of rocket engines should approach that of jets, and spaceplanes should be capable of several flights per day. The Spacecab lower stage would then operate like an airliner, albeit one fitted with rocket engines. Preliminary estimates indicate that the total cost of flying Spacecab on a 40-min suborbital flight would then be about five times greater than a one-hour flight (approximately 400 miles) of a 200-seat jet airliner having about half the take-off weight as Spacecab. The Spacecab lower stage can carry 10 times fewer passengers (20 compared with 200). The resulting cost per seat would therefore be about 50 times more than that of a 400-mile airline flight or in the region of UKP 5000. Market research indicates that about 2.5 million people per year would pay UKP 5000 for a brief flight to space. As a sanity check on this number, 2.5 million people per year is roughly equivalent to 2.3% of the global population of 7.5 billion taking one flight to space in their lifetime, assuming an average lifespan of 70 years. Given the public interest in space and the amount spent on luxury items, this seems if anything likely to be an underestimate. Such a demand would require a fleet of about 80, twenty-seat spaceplanes, assuming that each made an average of four flights per day.
Fig. 6. Suborbital and orbital launch trajectories.
These costs are far lower, and the fleet size far higher, than for any other projected use of space. The key to this low cost is the combination of full reusability, an aeroplane-like vehicle design and high traffic levels, which enables space operations to approach the maturity of airlines. These numbers are clearly approximate but do indicate that space tourism is likely to be the first use of space to require such airline-like operations. Spacecab is an updated version of the 1960s European Aerospace Transporter concept described earlier. Since then, aeroplanes such as (in chronological order) the Sud Ouest Trident and Saunders Roe SR.53 rocket fighters, the X-15, the NF-104, Concorde, the Space Shuttle Orbiter and SpaceShipOne have between them demonstrated all the required technologies. Thus, what would have been a feasible but difficult project in the 1960s should now be straightforward.
5.3. Orbital operations As well as carrying passengers and science experiments on suborbital flights, Spacecab could carry an upper stage that separates at Mach 4 and flies on to orbit carrying a 750 kg satellite or six people. Suborbital and orbital launch trajectories are compared in Fig. 6. Ascender's trajectory from Fig. 4 (which, as mentioned earlier, is shared by the Spacecab lower stage when operating on its own for suborbital flights) is shown together with an orbital launch. To launch a satellite, the vehicle climbs clear of the effective atmosphere, turns over toward the horizontal and then accelerates on a shallow ascent to about 8 km/s, depending on the height of the desired orbit. Considering the cost of a flight to orbit, the upper stage is smaller than the lower one but needs a more advanced structure and more expensive fuel. Our estimates indicate that the cost per flight of the orbital Spacecab will be about four times that of just the lower stage on a suborbital flight. It carries about three times fewer passengers (6 compared with 20). The cost per seat to orbit would therefore be about twelve times greater than for a suborbital flight, at about UKP 60,000. An enlarged development of Spacecab, called Spacebus but not described here for the sake of brevity, would have a cost per seat approximately half as much, or about UKP 30,000.
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This is about 1000 (one thousand) times lower than the cost of sending people to space using today's expendable launchers. Such are the potential benefits of replacing launchers like ballistic missiles with those like aeroplanes. Regarding timescales, large new aircraft that do not require advanced technology need typically seven years from go ahead to early operations, and Spacecab would require a similar period. As mentioned earlier, these early prototypes would have short-life rocket engines (by jet engine standards). It took eight years for jet engines to mature from early quasi-experimental fighter operations (1944) to the first jet airliner service (1952), and there is no obvious reason for the development of mature rocket engines to take longer, given a strong commercial incentive. In this way, the cost of sending people to space can be reduced about 1000 times using only proven technology (or to be more precise, mature developments of existing technology), within about 15 years (seven to build prototypes and eight to mature the design). As a fully reusable aeroplane-like orbital launcher, Spacecab would also be ideal for serving the burgeoning market for small satellites. Spacecab was the subject of a feasibility study funded by the European Space Agency in 1993/4 [3]. The main conclusion was that new technology was not needed. This conclusion was endorsed by an independent review commissioned by the then UK Minister for Space, Ian Taylor, MP, and carried out by the then British National Space Centre. The spaceplane approach to space transportation was endorsed recently by a pioneering study carried out by the UK Civil Aviation Authority [4]. 6. On to the Moon and Mars As mentioned earlier, one of the main aims of Spacecab is to enable the development at affordable cost of the long-awaited lowcost orbital infrastructure. Among the orbiting platforms that would become affordable are depots for servicing and re-fuelling specialised in-space transports. A regular transportation service to the Moon could be provided by vehicles broadly similar to those used in the 1960s Apollo programme but designed for long life, full reusability and in-orbit servicing. (Apollo vehicles were single-use.) These would include tugs for transfer between depots in Earth and lunar orbits, and lunar landers for transport between the depot in lunar orbit and the lunar surface. A study by the author [5] compared the cost of the first lunar base under present plans (that use expendable launchers) with the cost using spaceplanes for transport to and from orbit. The result was that using spaceplanes would cost very approximately ten times less, even including the cost of developing the spaceplanes themselves. As already discussed, the cost of the Earth to orbit part of the lunar journey would be greatly reduced by using spaceplanes. The cost of the in-space parts would also be reduced by using reusable vehicles, but to a lesser extent because of lower traffic levels. For travel to Mars and beyond, the low-cost orbital infrastructure would make more affordable the development of in-space electromagnetic catapults and nuclear rockets, which would help to overcome the limitations of chemical rockets and greatly reduce journey time. 7. Perception In this way, the first orbital spaceplane will trigger a spaceflight revolution. The revolution will be one of perception as much as one of engineering. Spaceplanes will introduce an aviation way of
thinking and operating, which in turn will transform the image of spaceflight from exotic to routine. Space will lose the ‘exceptionalism’ that has enabled extraordinary practices like throwing away a vehicle after each journey to persist for so long. Space operations will become subject to the same sorts of checks and balances that affect terrestrial transport. Space will come down to Earth, so to speak. The perception of low-cost access to space soon using only proven technology will change from ‘far too good to be true’ to ‘why wasn't it done years ago?' 8. Business case The business case for Spacecab is compelling because it is the only launcher currently being proposed that can offer a thousand times reduction in the cost of sending people to space within about fifteen years using only proven technology. In this way, Spacecab is likely to gain a large share of the markets for launching small satellites, government human spaceflight as far as low orbit, suborbital tourism and orbital tourism. We estimate that the development cost of Spacecab to the start of early operations (using prototypes built in an experimental workshop) is about UKP 2 billion. This is small compared with the likely size of any of these markets, and we estimate a very attractive return on investment. 9. Conclusions Orbital spaceplanes were widely studied and considered desirable and feasible in the 1960s but were not developed at the time because of the priorities given in the USA to Apollo and in Europe to Concorde. Since then, all the required technologies have been demonstrated in other aeroplanes. What would then have been a feasible but difficult project should now be straightforward. A spaceplane would be ideal for space tourism, which is likely to demand a higher launch rate than any other space business. The resulting economies of scale would enable a widely affordable airline service to orbit, which in turn would greatly reduce the cost of nearly all space activities, including developing a low-cost orbital infrastructure and a return to the Moon. The most plausible cause of this prospect not being more widely appreciated is the culture and ways of thinking arising from some sixty years of using expendable launchers. Declaration of interest Bristol Spaceplanes has plans for developing spaceplanes along the lines of those described in this paper. However, these designs are mentioned only when they are the only suitable exemplars. References [1] D.M. Ashford, Boost-glide vehicles for long range transport, J. R. Ae. Soc. (July 1965). [2] Review of European Aerospace Transporter Studies H. Tolle, in: Proceedings of SAE Space Technology Conference, Palo Alto, California, May 1967. This paper € lkow, Bristol Siddeley, Dassault, ERNO, Hawker describes designs by B.A.C., Bo Siddeley, and Junkers. [3] A Preliminary Feasibility Study of the Spacecab Low-Cost Spaceplane and of the Spacecab Demonstrator, Bristol Spaceplanes Limited Report TR 6, February 1994. Carried Out under European Space Agency Contract No. 10411/93/F/TB. Volume 1 Reproduced as ‘The Potential of Spaceplanes’ in the Journal of Practical Applications in Space, Spring, 1995. Journal since renamed as ‘Space Energy and Transportation’. [4] UK Government Review of Commercial Spaceplane Certification and Operations, Civil Aviation Authority, July 2014. [5] D. Ashford, ‘The aviation approach to space transportation’, Aeronautical Journal of the RAeSoc (August 2009) 499e515.
Contents lists available at ScienceDirect
Space Policy journal homepage: www.elsevier.com/locate/spacepol
Corporate Groupthink: The Main Obstacle to an Affordable Lunar Base David Ashford 1 Bristol Spaceplanes, 3 Forest Hills, Almondsbury, Bristol, BS32 4DN, United Kingdom
a r t i c l e i n f o
a b s t r a c t
Article history: Received 3 August 2019 Received in revised form 19 September 2019 Accepted 1 October 2019 Available online 1 November 2019
This article describes a launch vehicle development roadmap that uses only proven technology and that could lead to a thousand-fold reduction in the cost of sending people to orbit within about 15 years. It could reduce the cost of the first lunar base by very approximately ten times. This would clearly revolutionise spaceflight and create a new space age. The roadmap involves a combination of full reusability, aeroplane-like vehicle design and high traffic levels, especially from space tourism, to provide economies of scale. This line of development could have started some fifty years ago, and the failure to do this has led to a corporate groupthink that is probably now the biggest obstacle to progress. © 2019 Elsevier Ltd. All rights reserved.
Keywords: Low-cost access to space Space tourism Spaceplanes Reusable launch vehicles
Contents 1. 2. 3. 4. 5.
6. 7. 8. 9.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Historical perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Historical exemplardthe Lockheed NF-104 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Ascender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Spacecab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5.1. Design logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5.2. Suborbital operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5.3. Orbital operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 On to the Moon and Mars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Business case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Declaration of interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction The fiftieth anniversary of the first manned lunar landing (and the forty-seventh since the last man left the moon) is a good time to reflect on how best to revisit our closest heavenly neighbour. If the Moon was all that worth visiting, why such a long hiatus? There are perhaps two answers to this questiondcost and motivation.
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https://doi.org/10.1016/j.spacepol.2019.101344 0265-9646/© 2019 Elsevier Ltd. All rights reserved.
The Apollo programme cost some $25 billion at the time, which is equivalent to roughly $150 billion today or about seven times the total present NASA annual budget. It needed an extremely strong motivation to obtain such a huge sum of money. This was provided by the pressures of the Cold War. The USA saw itself as being in a desperate struggle with the Soviet Union for global domination and even for survival. The U.S. effort was kicked off by President Kennedy's famous speech In May 1961, just 6 weeks after Yuri Gagarin's historic first manned flight to space, when he galvanised the nation by saying, “If
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we are to win the battle that is going on around the world between freedom and tyranny, if we are to win the battle for men's minds … I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to Earth.” The opening phrases of this speech show that he was more interested in demonstrating U.S. technical superiority than in space exploration per se. This urgent political motivation is largely lacking today. Some U.S. politicians are trying to build up the Chinese lunar programme as a threat to justify increasing the NASA budget, but the public mood is far less receptive to this approach than it was some 60 years ago. The USA might be wiser to go back to the Moon in its own time, and if the Chinese get there first to gently point out that they achieved the same feat more than 50 years ago. The space programme is thus in urgent need of far lower launch costs and new motivations. This article summarises, as the basis for discussion, a straightforward way of providing both using only proven technology, as worked up over the years by Bristol Spaceplanes. The lower costs come from developing an orbital spaceplane designed to satisfy potentially large new commercial markets, especially space tourism. This spaceplane is an updated version of the 1960s European Aerospace Transporter concept (see next section), which was considered feasible at the time but which has never been built. The combination of full reusability, aeroplane-like design and the high traffic levels arising from these new markets would enable an airline service to orbit with greatly reduced costs. The motivation comes from the compelling commercial business case for developing such a spaceplane. The rest of this article describes the historical background to spaceplane development and how corporate groupthink has evolved to become the greatest barrier to progress. It then discusses what should be the leading design features of the first orbital spaceplane, a historical exemplar and a progressive development sequence of launch vehicles leading to the desired goal. Bristol Spaceplanes projects are mentioned only when there are no other suitable exemplars.
(with a payload of 20e30 tonnes) than the European designs (2e4 tonnes). Thus when President Nixon imposed a budget cut, NASA could no longer afford to develop such a large fully reusable vehicle. Rather than develop a smaller but still fully reusable aeroplane-like launcher, NASA decided to forego complete reusability, and the vehicle as built was largely expendable. It was therefore as expensive and risky to operate as the throwaway launchers that preceded it. This history seems to have created organisations and habits of thought that repeatedly reinforce the habit of expendability. Even now, most major space agencies are promoting the development of expendable launchers. The failure to develop orbital spaceplanes when they first became feasible in the 1960s has led to a cultural chasm between the aviation and space industries. Few launcher designers really understand airliners and vice versa. The aircraft industry does not seem to appreciate the opportunity that it has to take over space transportation from Earth to low orbit. This corporate groupthink is probably the biggest obstacle in the way of spaceplane development today.
2. Historical perspective
The first vehicle on the proposed development sequence is the Bristol Spaceplanes Ascender small suborbital spaceplane, Fig. 3. To climb higher than the NF-104, more rocket propellant is needed. By happy coincidence, the amount needed to reach space height, following a jet climb to around Mach 2 (about 40% of the aircraft weight at rocket start), is just achievable within existing technology boundaries. (A lower jet speed would require the rocket engine to do more of the acceleration and climb, which would need even more propellant because rockets use between ten and twenty times more than jets for a given thrust and time.) Ascender is the only suborbital spaceplane currently being proposed that uses jets to supersonic speed. It is like a secondgeneration NF-104 designed from scratch to reach space height. It could have been built in the 1960s. Ascender is like a quarter-scale Concorde with two seats, a simplified wing shape and fitted with two jet engines and a rocket engine. A typical trajectory is shown in Fig. 4. Ascender accelerates to Mach 1.8 using its jet engines only. The rocket engines are then started, and it pulls up to a climb angle of 70 . It then accelerates on this steep climb to a speed of Mach 3.2 at a height of 53 km. The rocket propellant is by then used up, and the aeroplane carries on unpowered under its own momentum to a height of just over 100 km. Ascender then descends under the influence of gravity, re-enters the atmosphere, pulls out of the dive, restarts its jet engines and flies back to the aerodrome from which it started. The passenger would see at one time an area the size of England and would experience about three minutes of
During the pioneering phase of spaceflight, converted ballistic missiles were used for launching satellites and astronauts. It was clear even then that throwing away one vehicle for each flight could never become economical and, in the 1960s, most big aircraft companies in Europe and the USA had substantial teams studying fully reusable aeroplanes that can fly to orbit (orbital spaceplanes) to replace these expendable launchers. The leading companies in €lkow, Bristol this field were British Aircraft Corporation, Boeing, Bo Siddeley, Convair, Dassault, Douglas, ERNO, Hawker Siddeley, Junkers, Lockheed, Martin and McDonnell. (The author's first job was as a junior member of the Hawker Siddeley team, and his first paper on spaceplanes was published in 1965 [1].) The European projects were studied under Eurospace auspices and were given the generic title of Aerospace Transporter [2]. The guiding mind was the rocket pioneer Eugen S€ anger. Some of the leading designs are shown in Fig. 1. The consensus in the 1960s was that an orbital spaceplane was a highly desirable development that was just about feasible with the technology of the day. However, they were not developed at the time, largely because the budget for advanced prestige projects was used up in the USA by the Cold War race to the Moon and in Europe by Concorde. It is less easy to explain why orbital spaceplanes have not been developed since then. In the 1970s, the early designs of the Space Shuttle were indeed fully reusable, but this project was much larger
3. Historical exemplardthe Lockheed NF-104 Of aircraft that have actually flown, the closest to those described later is the Lockheed NF-104, Fig. 2. The basic Lockheed F104 Starfighter was a first-generation Mach 2 fighter that first flew in 1954. In 1962/63, three F-104s were converted for training astronauts by adding a rocket engine to boost its maximum height. They were given the designation of NF-104. The conversion was successful, and it reached a height of 120,800 ft (36.8 km). It reached Mach 2 on jet power before the rocket was started. The F-104 was a tightly packed fighter aeroplane with little spare volume for rocket propellant. This limited its maximum height to about one-third of the 100 km usually considered as being the boundary of space. 4. Ascender
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Fig. 1. European Aerospace Transporter (Orbital spaceplane) projects of the mid-1960s.
weightlessness. This is a suborbital trajectorydorbital flight is discussed later. Ascender would have a wide application for various types of space research and for carrying passengers on brief space experience flights. Ascender uses only proven technology and could be flying in about five years. Flights to space in Ascender would become routine after a few years in service. (As routine as flying the NF-104 would have become if there had been a need to put it into operational service and build it in significant numbers.)
platforms towed into position by ocean-going tugs, with helicopters or small boats for everyday supplies. Two of these three elements already exist. Heavy-lift launchers have been in service since the Apollo of the late 1960s, and orbiting platforms (space stations) have been in service for nearly as long. One heavy-lift launcher under developmentdthe SpaceX BFRdwill be fully reusable, which will help to reduce costs.
5. Spacecab Ascender is a stepping-stone to the second vehicle on the sequencedthe two-stage Spacecab spaceplane, Fig. 5. The lower stage is like Ascender but is scaled up by a factor of four to about the same size as Concorde. Even if it were still in production, Concorde itself would not be suitable for such a rocket conversion because the loads and speed would be well outside its design limits. An all-new vehicle will be required. However, the required design changes compared with Concorde would all be straightforward and much Concorde technology could be used. The upper stage can be either a module carrying 20 passengers and that remains attached for a suborbital flight, or a reusable launcher that separates at Mach 4 and carries on to orbit under rocket power with either six passengers or a satellite or cargo of 750 kg. The orbital upper stage version is shown here. 5.1. Design logic Before considering Spacecab operations in more detail, it is worth considering the logic behind the selection of its basic design features. It has long been considered that routine and affordable access to space is the desired goal and that this is best achieved by building a ‘low-cost orbital infrastructure’. This consists of large orbiting platforms for various scientific and commercial purposes, heavy-lift launchers for placing these platforms in orbit and a small launcher for the regular delivery of crews and supplies. This is analogous to the offshore oil industry, which uses large drilling
Fig. 2. A Lockheed NF-104 climbing under rocket power. [US Air Force Test Center History Office].
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Fig. 3. The Bristol Spaceplanes Ascender suborbital spaceplane.
This leaves the small launcher suitable for high-frequency operations as the missing element. The basic design features of this vehicle can be derived using a straightforward logic. The first requirement is that it should be fully reusable. Today's launchers use large components that can fly only once, which is the root cause of the high cost and risk of spaceflight. (There are reusable booster stages and capsules but not yet reusable upper stages launched by reusable lower ones.) To gain insight into the cost penalty of this expendability, consider that the purchase price of a new car is very roughly 1000 times more than the cost of driving it for a few hours. Thus, if cars had to be scrapped every day, motoring would cost roughly 1000 times more than it does. Much the same applies to aviation. The production cost of an airliner is roughly 1000 times more than the cost of operating it on a long-range fight. Thus, if airliners could fly only once, the cost of a flight across the Atlantic would be roughly 1000 times more than it is. There is another major difference between space transportation and commercial air traveldthe former has far lower traffic levels. There are about 100 satellite launches per year compared with some 40 million commercial airline flights. The low launch rate precludes approaching aviation standards of maturity and low operating cost and is largely because of the high costs imposed by expendability. Spaceflight today is limited to government-funded missions and a few commercial applications such as
communications, TV, navigation, Earth observation and weather forecasting. These markets involve essentially using satellites to process and transmit data, and so a high launch cost per tonne is not a major handicap. However, new markets of very large commercial potential, such as space manufacture, solar-power satellites and orbital tourism, require the regular transportation of many tonnes of people and material and are thereby held back by high transportation cost. The new launcher should therefore be suitable for the large new markets to provide higher traffic levels and economies of scale. The new markets, especially space tourism, will require far greater safety than can be achieved by expendable launchers. This means that the new launcher should be designed to airliner standards as far as is practical, as these are the safest flying machines yet built. It should therefore be piloted and have wings for horizontal take-off and landing. These features should also offer better passenger appeal than vehicles that land vertically on a rocket pad. So that existing technology can be used, the new launcher should have two stages, as single-stagers require advanced new airbreathing engines. Finally, to generate large new markets, the lower stage should be able to operate on its own for suborbital missions, especially tourism. In summary, the new launcher best able to reduce launch costs should have the following basic features: It should be fully reusable. It should have two stages. Both stages should be piloted and have wings for horizontal take-off and landing. The lower stage should be able to operate on its own for suborbital missions, especially tourism. It is noteworthy that most of the 1960s European Aerospace Transporter designs had these features and that Spacecab is the only vehicle to have them that is currently being proposed.
5.2. Suborbital operations
Fig. 4. Ascender trajectory.
When the lower stage is used on its own for carrying passengers on suborbital space experience flights, its trajectory would be similar to that of Ascender shown earlier in Fig. 4. The total flight time would be about 40 min.
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Fig. 5. The Bristol Spaceplanes Spacecab orbital spaceplane.
Early suborbital fights would be expensive by aviation standards because of the short life of today's rocket engines and the need for significant maintenance between flights. As operating experience built up and the design matured, the life of rocket engines should approach that of jets, and spaceplanes should be capable of several flights per day. The Spacecab lower stage would then operate like an airliner, albeit one fitted with rocket engines. Preliminary estimates indicate that the total cost of flying Spacecab on a 40-min suborbital flight would then be about five times greater than a one-hour flight (approximately 400 miles) of a 200-seat jet airliner having about half the take-off weight as Spacecab. The Spacecab lower stage can carry 10 times fewer passengers (20 compared with 200). The resulting cost per seat would therefore be about 50 times more than that of a 400-mile airline flight or in the region of UKP 5000. Market research indicates that about 2.5 million people per year would pay UKP 5000 for a brief flight to space. As a sanity check on this number, 2.5 million people per year is roughly equivalent to 2.3% of the global population of 7.5 billion taking one flight to space in their lifetime, assuming an average lifespan of 70 years. Given the public interest in space and the amount spent on luxury items, this seems if anything likely to be an underestimate. Such a demand would require a fleet of about 80, twenty-seat spaceplanes, assuming that each made an average of four flights per day.
Fig. 6. Suborbital and orbital launch trajectories.
These costs are far lower, and the fleet size far higher, than for any other projected use of space. The key to this low cost is the combination of full reusability, an aeroplane-like vehicle design and high traffic levels, which enables space operations to approach the maturity of airlines. These numbers are clearly approximate but do indicate that space tourism is likely to be the first use of space to require such airline-like operations. Spacecab is an updated version of the 1960s European Aerospace Transporter concept described earlier. Since then, aeroplanes such as (in chronological order) the Sud Ouest Trident and Saunders Roe SR.53 rocket fighters, the X-15, the NF-104, Concorde, the Space Shuttle Orbiter and SpaceShipOne have between them demonstrated all the required technologies. Thus, what would have been a feasible but difficult project in the 1960s should now be straightforward.
5.3. Orbital operations As well as carrying passengers and science experiments on suborbital flights, Spacecab could carry an upper stage that separates at Mach 4 and flies on to orbit carrying a 750 kg satellite or six people. Suborbital and orbital launch trajectories are compared in Fig. 6. Ascender's trajectory from Fig. 4 (which, as mentioned earlier, is shared by the Spacecab lower stage when operating on its own for suborbital flights) is shown together with an orbital launch. To launch a satellite, the vehicle climbs clear of the effective atmosphere, turns over toward the horizontal and then accelerates on a shallow ascent to about 8 km/s, depending on the height of the desired orbit. Considering the cost of a flight to orbit, the upper stage is smaller than the lower one but needs a more advanced structure and more expensive fuel. Our estimates indicate that the cost per flight of the orbital Spacecab will be about four times that of just the lower stage on a suborbital flight. It carries about three times fewer passengers (6 compared with 20). The cost per seat to orbit would therefore be about twelve times greater than for a suborbital flight, at about UKP 60,000. An enlarged development of Spacecab, called Spacebus but not described here for the sake of brevity, would have a cost per seat approximately half as much, or about UKP 30,000.
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This is about 1000 (one thousand) times lower than the cost of sending people to space using today's expendable launchers. Such are the potential benefits of replacing launchers like ballistic missiles with those like aeroplanes. Regarding timescales, large new aircraft that do not require advanced technology need typically seven years from go ahead to early operations, and Spacecab would require a similar period. As mentioned earlier, these early prototypes would have short-life rocket engines (by jet engine standards). It took eight years for jet engines to mature from early quasi-experimental fighter operations (1944) to the first jet airliner service (1952), and there is no obvious reason for the development of mature rocket engines to take longer, given a strong commercial incentive. In this way, the cost of sending people to space can be reduced about 1000 times using only proven technology (or to be more precise, mature developments of existing technology), within about 15 years (seven to build prototypes and eight to mature the design). As a fully reusable aeroplane-like orbital launcher, Spacecab would also be ideal for serving the burgeoning market for small satellites. Spacecab was the subject of a feasibility study funded by the European Space Agency in 1993/4 [3]. The main conclusion was that new technology was not needed. This conclusion was endorsed by an independent review commissioned by the then UK Minister for Space, Ian Taylor, MP, and carried out by the then British National Space Centre. The spaceplane approach to space transportation was endorsed recently by a pioneering study carried out by the UK Civil Aviation Authority [4]. 6. On to the Moon and Mars As mentioned earlier, one of the main aims of Spacecab is to enable the development at affordable cost of the long-awaited lowcost orbital infrastructure. Among the orbiting platforms that would become affordable are depots for servicing and re-fuelling specialised in-space transports. A regular transportation service to the Moon could be provided by vehicles broadly similar to those used in the 1960s Apollo programme but designed for long life, full reusability and in-orbit servicing. (Apollo vehicles were single-use.) These would include tugs for transfer between depots in Earth and lunar orbits, and lunar landers for transport between the depot in lunar orbit and the lunar surface. A study by the author [5] compared the cost of the first lunar base under present plans (that use expendable launchers) with the cost using spaceplanes for transport to and from orbit. The result was that using spaceplanes would cost very approximately ten times less, even including the cost of developing the spaceplanes themselves. As already discussed, the cost of the Earth to orbit part of the lunar journey would be greatly reduced by using spaceplanes. The cost of the in-space parts would also be reduced by using reusable vehicles, but to a lesser extent because of lower traffic levels. For travel to Mars and beyond, the low-cost orbital infrastructure would make more affordable the development of in-space electromagnetic catapults and nuclear rockets, which would help to overcome the limitations of chemical rockets and greatly reduce journey time. 7. Perception In this way, the first orbital spaceplane will trigger a spaceflight revolution. The revolution will be one of perception as much as one of engineering. Spaceplanes will introduce an aviation way of
thinking and operating, which in turn will transform the image of spaceflight from exotic to routine. Space will lose the ‘exceptionalism’ that has enabled extraordinary practices like throwing away a vehicle after each journey to persist for so long. Space operations will become subject to the same sorts of checks and balances that affect terrestrial transport. Space will come down to Earth, so to speak. The perception of low-cost access to space soon using only proven technology will change from ‘far too good to be true’ to ‘why wasn't it done years ago?' 8. Business case The business case for Spacecab is compelling because it is the only launcher currently being proposed that can offer a thousand times reduction in the cost of sending people to space within about fifteen years using only proven technology. In this way, Spacecab is likely to gain a large share of the markets for launching small satellites, government human spaceflight as far as low orbit, suborbital tourism and orbital tourism. We estimate that the development cost of Spacecab to the start of early operations (using prototypes built in an experimental workshop) is about UKP 2 billion. This is small compared with the likely size of any of these markets, and we estimate a very attractive return on investment. 9. Conclusions Orbital spaceplanes were widely studied and considered desirable and feasible in the 1960s but were not developed at the time because of the priorities given in the USA to Apollo and in Europe to Concorde. Since then, all the required technologies have been demonstrated in other aeroplanes. What would then have been a feasible but difficult project should now be straightforward. A spaceplane would be ideal for space tourism, which is likely to demand a higher launch rate than any other space business. The resulting economies of scale would enable a widely affordable airline service to orbit, which in turn would greatly reduce the cost of nearly all space activities, including developing a low-cost orbital infrastructure and a return to the Moon. The most plausible cause of this prospect not being more widely appreciated is the culture and ways of thinking arising from some sixty years of using expendable launchers. Declaration of interest Bristol Spaceplanes has plans for developing spaceplanes along the lines of those described in this paper. However, these designs are mentioned only when they are the only suitable exemplars. References [1] D.M. Ashford, Boost-glide vehicles for long range transport, J. R. Ae. Soc. (July 1965). [2] Review of European Aerospace Transporter Studies H. Tolle, in: Proceedings of SAE Space Technology Conference, Palo Alto, California, May 1967. This paper € lkow, Bristol Siddeley, Dassault, ERNO, Hawker describes designs by B.A.C., Bo Siddeley, and Junkers. [3] A Preliminary Feasibility Study of the Spacecab Low-Cost Spaceplane and of the Spacecab Demonstrator, Bristol Spaceplanes Limited Report TR 6, February 1994. Carried Out under European Space Agency Contract No. 10411/93/F/TB. Volume 1 Reproduced as ‘The Potential of Spaceplanes’ in the Journal of Practical Applications in Space, Spring, 1995. Journal since renamed as ‘Space Energy and Transportation’. [4] UK Government Review of Commercial Spaceplane Certification and Operations, Civil Aviation Authority, July 2014. [5] D. Ashford, ‘The aviation approach to space transportation’, Aeronautical Journal of the RAeSoc (August 2009) 499e515.