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Space Future has been on something of a hiatus of late. With the concept of Space Tourism steadily increasing in acceptance, and the advances of commercial space, much of our purpose could be said to be achieved. But this industry is still nascent, and there's much to do. this space.
9 December 2010
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"What the Growth of a Space Tourism Industry Could Contribute to Employment, Economic Growth, Environmental Protection, Education, Culture and World Peace" is now the top entry on Space Future's Key Documents list.
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D Ashford, 27 October 1998, "The Imminent Space Revolution - How the UK Can Take the Lead", Presented to the Institution of Incorporated Engineers, 27 October 1998.
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The Imminent Space Revolution - How the UK Can Take the Lead

A revolution in the way we operate in space is imminent. Within the limitations of technical forecasting, it is highly likely that passenger flights to space will start within a decade. The cost of operating space stations and of sending people to orbit will be reduced by about one thousand times within 15 years.

The revolution will involve replacing launchers based on ballistic missiles by those based on aeroplanes. Ballistic missiles have the major disadvantage that they can fly once only. This is the fundamental cause of the high cost and risk of present spaceflight. Spaceplanes could have entered service some twenty five years ago, but NASA had alternative priorities. Technology is now such that a sub-orbital spaceplane is within the scope of a small aerospace company.

The logic behind these forecasts is simple and robust. It has been well publicised and is supported by a growing number of people in the field. It is not widely appreciated because it is not in line with the present policies of NASA and ESA.

The paper explains the arguments behind these predictions, and describes a straightforward project that would enable the UK to take the lead in setting up the new spaceplane industry.


Imagine a fleet of fifty spaceplanes looking somewhat like Concorde and capable of making several flights per day to orbit from ordinary airports. The cost of sending people to space and of operating space stations is 1000 times less than it is today. Large manned observatories equipped with big sensitive instruments are enabling breakthroughs in astronomy and Earth science. One million people per year take brief holidays in space hotels, enjoying experiences impossible on Earth. They enjoy superb views of whole continents at a time; they can strap wings to their arms and fly like birds in low-g gymnasiums; they can swim and fly like flying fish in low-g pools; and they can take mind-blowing looks at the heavenly bodies through telescopes untroubled by the distortions of the atmosphere. Affordable manned visits to the Moon and Mars are being planned. Large robotic explorers are on the way to every major object in the Solar System.

This is not some distant fancy. The least unlikely outcome of developments in hand right now is that this scenario will happen in about fifteen years. The UK is well placed to take the lead. Let me explain.


Perhaps surprisingly, the least controversial aspect of these seemingly outlandish claims is the engineering. Fig. 1 shows a progressive sequence of spaceplane designs proposed by my company. It is based on studies carried out over several years, see for example refs. 1-4.

Ascender is the first vehicle on the sequence, fig. 2. It is a sub-orbital spaceplane, i.e. it can reach space height but not satellite speed. It carries four people and is fitted with jet engines and a rocket motor. It takes off and climbs to 30,000 ft using the jets, fig. 3. The pilot then starts the rocket and pulls up into a steep climb. The rocket fuel is used up at a height of 40 miles while Ascender is flying close to the vertical at a speed of Mach 2.8. It coasts unpowered to a height of 60 miles and is in space for about two minutes. It falls back to Earth under the pull of gravity, re-enters the atmosphere, pulls out of the dive and flies back to the airfield from which it took off. The total flight time is about 30 minutes. The performance of Ascender is just less than that of the X-15 rocket powered research aeroplane which made 199 flights, many to space, between 1959 and 1968.

Figure 2. The Ascender Sub-Orbital Spaceplane
Figure 3. Ascender Flight Path

18 0.6
264 2.8
3100 0
446 3.3
524 3.3

Ascender will be used initially for research purposes and then for carrying passengers on brief space experience flights. A prototype could be flying in three years and production versions carrying passengers three or four years later. The development cost of the prototype is less than 50 million.

The second vehicle is Spacecab, shown in fig. 4. It is a small spaceplane capable of reaching orbit. It will launch a one tonne satellite, or carry six people. Initially these would be astronauts visiting a space station or servicing a satellite. Later, Spacecab would be used for pioneering space tourism. Spacecab could be flying in five or six years at a development cost of around 1 billion. It is based on the European Aerospace Transporter designs of the early 1960s, but is updated to use technology developed since then for other projects. My first job, starting in 1961, was with the Hawker Siddeley Aviation team working on an Aerospace Transporter. We thought at that time that the concept was feasible, as did teams working for most of the large aerospace companies in Europe and the USA.

Figure 4. The Spacecab Orbital Spaceplane. A Study for ESA Showed that a Spacecab Prototype Could Use Existing Engines and Proven Materials

The third vehicle, Spacebus, is an enlarged and mature development of Spacecab, carrying 50 passengers or a five tonne satellite. Applying airliner cost estimating relationships to Spacebus gives a direct cost per person to orbit of around 3000. Adding overheads, profits and space station costs results in a fare for a few days in space of some 6000, which is about 1000 times less than the cost per person in the Space Shuttle.

These low costs assume airliner maturity, i.e. vehicles capable of several flights per day and a life of ten or more years. The technology for a prototype Spacebus exists today, but it would fall far short of airliner maturity. The rocket engines and the heat shield would need inspection and maintenance between every flight, and the airframe would have a life probably as low as 100 flights. The pacing item in achieving airliner maturity is likely to be a rocket motor with long life and low maintenance cost. Existing rocket motors, suitable for a prototype Spacebus, have a life of a few flights. Test times are still quoted in seconds.

Jet engines took eight years to mature from early operational use in 1944 in the Me 262 and Gloster Meteor to the first airline service in 1952 in the de Havilland Comet. A long life rocket motor has similar development challenges to that of a long life jet engine. Both require metal parts to be highly stressed at high temperature. It is therefore probable that, given the commercial incentive, long life rocket motors would evolve in a comparable timescale.

The technical feasibility of this development sequence is hardly in doubt. Ascender is designed to do on an everyday basis what the X-15 was doing on a research basis thirty five years ago. Thirty five years is a long time in aerospace. Spacecab is based on designs considered feasible also around thirty five years ago. My company carried out a feasibility study of Spacecab for the European Space Agency (ESA) in 1994, ref. 3, that showed that existing engines and proven materials could be used on a prototype. A subsequent independent review commissioned by the then Minister for Space agreed that the project was technically sound. There is no reasonable doubt that a long life motor could be developed, given the incentive.

The costs and timescales are less certain, but are in the right ball park. The DC-X experimental reusable launch vehicle cost about 50 million, and this was larger and more advanced than Ascender. A development cost of around 40 million is claimed for the X-34 experimental spaceplane due to fly next year. The X-34 is larger and faster than Ascender. The X-33 large experimental spaceplane, also due to fly next year, has an estimated development cost of around 600 million, and this is a more difficult and risky project than Spacecab.

These costs are for prototypes only. However, the prototypes of Ascender and of Spacecab are designed to be suitable for carrying non-passenger payloads and therefore of earning money as soon as they reach full performance. Certification for passenger carrying is applied for only after sufficient flights have taken place.

When routine low-cost transportation to orbit becomes available, the cost of building space stations and space hotels will become comparable to that of airliners of similar weight. Given the absence of distorting gravitational forces, it will be possible to build very large lightweight structures suitable for microgravity flying and swimming. There is no obvious reason why the hazards of space debris and radiation should not be manageable by straightforward development programmes.


The market for spaceplanes can be considered in the categories of long term and short term, and commercial and government. The largest long term commercial market is likely to be space tourism. Conservative interpretations of market surveys, e.g. refs. 5 and 6, indicates that one million people per year world wide would take a trip to space at the cost levels achievable with a mature spaceplane. This would require a fleet of some 50 spaceplanes. Other potential long term commercial markets have less certain demand (manufacture in space) or require additional technology (solar power collection for use on Earth). Long term government markets include science and space exploration.

The largest short term commercial market for Spacecab is likely to be launching low orbit satellites for global mobile communications. Several constellations are planned. The first, Iridium, should be operational by the time this paper is published. Preliminary estimates suggest that this market is just about large enough for spaceplane development costs to be recovered on a commercial basis, but that the financial risk would be high.

The largest potential short term government market for Spacecab is space station supply. The International Space Station will need several Shuttle flights per year for supply operations, at a cost of some $500 million each. Spacecab flights would cost some $2 million each. Thus the development cost of Spacecab would be recovered in just one or two years by substituting for the Shuttle. Europe is involved with the ISS, and so there is a legitimate European interest in supply operations.

Thus ESA and/or NASA could pioneer low cost access to space and save money by developing a small orbital spaceplane using existing technology. If one looks at the present NASA and ESA plans for manned spaceflight and compares them with the approach suggested here, the latter involves lower budgets and leads to a mature spaceplane far sooner.

Thus ESA and/or NASA could pioneer low cost access to space and save money by developing a small orbital spaceplane using existing technology.

This sentence is deliberately repeated, for emphasis. It is probably the key to making it happen, as explained later.


The proposed development sequence is aimed at achieving a mature spaceplane at least cost to the taxpayer. Passenger carrying is the market most likely to generate high traffic levels and to bring in large private sector revenues, thereby providing the commercial incentive to achieve maturity. Thus the design features of Spacecab and Spacebus have been selected so that certification for passenger carrying can be achieved using existing technology. They are therefore piloted and have two stages separating at high supersonic speed. The carrier aeroplane lower stage has existing jet engines for practical low speed operations, and rockets in order to achieve an adequate separation speed and height.

Ascender is intended primarily for risk reduction and to provide an early demonstration of the practicability of everyday space flight.


The previous sections have described a progressive sequence of spaceplane designs aimed at achieving a mature spaceplane at least cost to the taxpayer. The engineering is conservative, and commercial revenues are generated as early as practicable. The key is to start with a prototype sub-orbital spaceplane to be followed by a small orbital spaceplane, both using existing technology. The resulting demonstration of aeroplane-like transport to orbit would open the way for private sector investment to exploit the new commercial markets, leading to a mature spaceplane.

In an ideal world something along these lines would at least be taken seriously by those responsible for policy and industrial investment. This has not yet happened, so it is useful to consider what is likely outcome if this situation does not change.

The answer lies in the US.

Several US start-up companies have gained significant funding towards the development of reusable launchers aimed at the one tonne communications satellite market. These companies include Kelly Space and Technology, Kistler Aerospace Corporation, Pioneer Rocketplane and Rotary Rocket. Some of these US companies are due to fly demonstrators next year. In addition to these privately funded developments, NASA is part funding the X-33 and X-34 experimental spaceplanes, also due to fly next year.

It is likely that at least one of the US spaceplane projects will soon fly successfully on a routine basis. This should trigger the paradigm shift in which the aeroplane approach to space transportation becomes generally accepted. Given the commercial incentive of constellations of small satellites and of space tourism, a mature spaceplane is then all but inevitable. The timescale is likely to be comparable to that described earlier, with a long-life rocket motor as the pacing item. Thus sub-orbital passenger flights are likely within a decade, and a million people per year are likely to be visiting space within fifteen years.


A fully reusable orbital spaceplane could have entered service in the early 1970s. If this had happened we would probably now have a mature spaceplane, and launch costs today would be 1000 times lower than they are. The reasons that this did not happen are linked to NASA politics. Having brilliantly got 12 men to the Moon and back, NASA in the early 1970s was geared up for a new mega-project. The alternative would have been the incremental development of hardware they already had. This would have led to an orbital follow-on to the X-15, i.e. the fully reusable orbital spaceplane which is the key to slashing launch costs.

In the event, NASA developed the Space Shuttle, which is only partly reusable and as expensive to operate as the preceding expendable vehicles.

We have become so used to this over the years that it is almost taken for granted that a vast effort will be needed to reduce the cost and risk of spaceflight. So when small start-up companies say that the technology now exists for them to get on with it, they have a credibility problem. It has taken this long for a few US companies to get even initial funding.

We are a few years behind in Europe, and the main obstacle to starting the development of a mature spaceplane here is still mind-set. Given the commercial risks, some government support is probably necessary. The private US spaceplane companies have not yet achieved full funding, and their financial institutions are in general more adventurous than their European counterparts.

But ESA is committed to prestige manned space projects that are politically inspired and offer a poor return to the taxpayer. The UK government was wise enough not to join these projects, but on the other hand is so uninterested in manned spaceflight that it is all but impossible to obtain even seedcorn support.


The US spaceplane projects mentioned earlier are not designed with the features needed for a mature spaceplane as soon as practicable, and the development strategy described here could still get there sooner and at less cost and risk. There is therefore an opportunity for the UK to take the lead. Ascender was invented here and we have the engineering capability to develop it.

If the development of Ascender were started in the UK, the advantages of the proposed route to a mature spaceplane would become so obvious that our politicians should be able to persuade Europe to join in. The UK could then take the leading share of the large and profitable new market for spaceplanes.

A radio controlled development model of Ascender is flying successfully, fig. 5. An experienced core development team is on standby. But time is running out if the UK is to take the lead in space on a shoestring budget. If any IIE member has ideas for speeding up gaining support in this country, please get in touch.

Figure 5. Radio Controlled Development Model of Ascender, Wroughton, May 1998.
  1. D M Ashford, July 1965, " Boost Glide Vehicles for Long Range Transport", J R Ae Soc
  2. David Ashford and Patrick Collins, 1990, "Your Spaceflight Manual - How You Could be a Tourist in Space Within Twenty Years", Headline
  3. Bristol Spaceplanes Limited, February 1994, A Preliminary Feasibility Study of the Spacecab Low-Cost Spaceplane and of the Spacecab Demonstrator". Bristol Spaceplanes Limited Report Number TR6. Prepared for the European Space Agency under Contract No 10411/93/F/TB. (Volume 1 subsequently published as " The Potential of Spaceplanes" in the Journal of Practical Applications in Space, Spring 1995.)
  4. D M Ashford, February 1997, "Space Tourism - How Soon Will It Happen?", presented at 1997 IEEE Aerospace Conference, Snowmass, Colorado, Feb 1-8.
  5. Patrick Collins, Yoichi Iwasaki, Hideki Hanayama and Misuzu Ohnuki, "Commercial Implications of Market Research on Space Tourism", Journal of Space Technology and Science, Vol 10, No 2 pp 3-11.
  6. P Collins, R Stockmans and M Maita, December 1995, "Demand for Space Tourism in America and Japan, and its Implications for Future Space Activities", presented at Sixth International Space Conference of Pacific-Basin Societies, Marina del Rey, California.

For additional information, see websites and

David Ashford is Managing Director of Bristol Spaceplanes Limited, whose major project is the Ascender sub-orbital spaceplane. He graduated from Imperial College in aeronautical engineering and spent one year at Princeton doing post-graduate research on the combustion instability of rocket motors. His first job, starting in 1961, was with the Hawker Siddeley Aviation Advanced Projects Group as an aerodynamicist on hypersonic aeroplanes and spaceplanes. He has since worked as an aerodynamicist, project engineer and project manager on several aerospace projects, including DC-8, DC-10, Concorde, the Skylark sounding rocket, and various naval missile systems. He co-authored the first serious book on space tourism "Your Spaceflight Manual - How You Could be a Tourist in Space Within Twenty Years", by David Ashford and Patrick Collins, Headline 1990.

D Ashford, 27 October 1998, "The Imminent Space Revolution - How the UK Can Take the Lead", Presented to the Institution of Incorporated Engineers, 27 October 1998.
Also downloadable from imminent space revolution how the uk can take the lead.shtml

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