As the first UK-funded launcher technology programme in 22 years begins, Flightglobal.com can reveal secret US government interest in the British Aerospace 1980s' HOTOL spaceplane - and the reasons behind that reusable rocket's cancellation.
On 19 February this year Reaction Engines, a company formed by HOTOL veterans, announced a £6 million ($8.7 million) technology programme supported by about £1.2 million of European Space Agency funding, which includes UK government monies.
The programme is to investigate a heat exchanger, an oxidiser cooled combustion chamber and an adaptive nozzle, all of which are technologies that were key to the horizontal take-off and landing HOTOL concept and are now planned for Reaction Engine's son-of-HOTOL spaceplane, called Skylon.
The HOTOL story goes back to August 1984 when BAe, the forerunner to today's BAE Systems, unveiled a satellite launcher concept that would see an unmanned automatic vehicle use runways of "Concorde length" to carry 7,000kg (15,400lb) to low Earth orbit in its 4.6m (15ft) diameter payload bay.
ESA's member states had been looking to replace its Ariane 4 launcher and the HOTOL announcement preceded the space agency's member states' 30-31 January 1985 ministerial meeting at which a decision was taken to start preparatory work on the expendable Ariane 5 rocket.
France had proposed its manned Hermes mini space shuttle, to be launched by Ariane 5. Then UK industry minister Geoffrey Pattie wrote to Treasury chief secretary Peter Rees on 25 February explaining how French diplomatic pressure had, perversely, won support for HOTOL: "[The French] were unsuccessful [in getting support for Hermes] and irritated most other member states, who then welcomed the opportunity to express interest in [HOTOL]." The meeting's communique asked the UK to keep the agency informed of HOTOL's progress.
In December 1984 a Department of Trade and Industry (now the Department for Business, Enterprise and Regulatory Reform) space branch memo, classified restricted, had reported German interest in HOTOL and French criticism that the spaceplane would burn up as it did not have Space Shuttle-like thermal tiles.
The memo said that BAe had answered this French criticism, but such was France's reaction that a handwritten note at the bottom of the memo says: "I think we must try to avoid appearing to rival or exclude the French in discussions with them."
The project was also attracting criticism at home, with the Rugby-based project management consultant David Andrews producing an eight-page critique. Written in December 1984 for Aerospace magazine, it was sent to the DTI's space branch director. Included in Andrews' criticisms of HOTOL was that the design was optimised for the ascent, but would extend the thermal loading on descent, due to too little drag.
And, more fundamentally, the vehicle offered no capability that was not already available. But this paper did not halt government interest in the project, and a handwritten note at the bottom of Andrews' letter to the DTI says that the criticisms had been answered by BAe.
In early 1985 HOTOL was a project with some European support. But as Pattie noted in his 25 February letter: "If the UK were to take the lead in a new launcher...it would be a major change in government policy." The stage was set for a vigorous discussion between departments on what HOTOL meant for spending.
The earliest evidence of US involvement came with a 4 March 1985 DTI memo to Treasury officials about a 1 March conversation between the memo's author, DTI space branch director Andrew Nicholas, and Frank Miles, who at that time was space correspondent for the UK's ITN service.
Nicholas reports that Miles claimed to know of ongoing HOTOL technology licensing negotiations between Rolls-Royce and US propulsion company Rocketdyne, now owned by Pratt & Whitney. This memo also reported that HOTOL had run into difficulties with the Ministry of Defence at a 28 February presentation.
This difficulty is echoed in comments in an April 1985 letter marked Secret UK Eyes Alpha from the MoD's research and development department deputy controller James Barnes to the Cabinet Office's chief scientific adviser, Sir Robin Nicholson.
Barnes wrote that there was no justification for developing a UK launcher capability and no defence requirement for HOTOL vehicles, adding that it would be unlikely to enter service until the 2020s and that the "engineering problems are considerable".
He did describe the HOTOL engine as "ingenious" and "based on a secret patent awarded to Alan Bond of the UK [Atomic Energy Authority] Culham Laboratory".
Despite this MoD resistance, later that month Pattie wrote to then-defence minister Michael Heseltine proposing a two-year £3 million (in 1985 money) public-private partnership proof of concept study with £1 million from government and the remainder divided between R-R and BAe. MoD support was key because the HOTOL engine had been classified and without the military's support the engines could not be developed.
Pattie also argued that the MoD could justify its spend on the basis of "strategic capability" and that rig tests of the key technologies of heat exchangers and combustion chambers could lead to international collaboration.
Heseltine's reply is not in the archive, but three papers from the released files have been kept classified under the UK's Freedom of Information Act exemption for "formulation of government policy".
By early July 1985 more problems for HOTOL had emerged. In a letter to the MoD's engines director general, R-R technical director Gordon Lewis says that R-R wanted the Royal Aircraft Establishment's (RAE) propulsion group involved and that the company would not invest its own money in HOTOL engine development. Yet for the £3 million programme, £1 million was supposedly coming from R-R.
The third quarter of 1985 saw work on the BAe/R-R two-year proof of concept study proposal and by November the case for US collaboration was getting stronger.
At an 8 November meeting between the RAE and the DTI's space branch it was reported that R-R now called its HOTOL engine Swallow and the company was seeking US ramjet data. R-R also expected to need US nozzle technology.
That month minutes of a conversation between then-prime minister Margaret Thatcher's minister without portfolio Lord Young and US president Ronald Reagan's science adviser George Keyworth were also sent to the DTI.
The minutes show that the USA was interested in collaborating on a hypersonic aircraft like HOTOL, that Pattie had attended a meeting in the USA for nations interested in such a project and that a "prototype could be flying as early as 1990".
But despite Keyworth's offer the UK government files show that neither the BAe or the MoD wanted US involvement, wary of the UK becoming too junior a partner while R-R saw a need for transatlantic co-operation.
In November 1985 an RAE assessment of the proof-of-concept study proposal was downbeat. The RAE thought that HOTOL would take up to 20 years to develop, not the 12 years BAe and R-R were proposing. It said there was a need for £750 million for the six-year definition phase based on a total project cost of £5 billion, in 1985 money.
It also said there was only £1.5 million pledged of the proposed two-year study's £2 million industry funding, with £1 million from BAe and £485,000 from R-R, and that an early decision was needed to ensure funding for a post-proof of concept, pre-definition phase feasibility study expected to cost £25 million.
Despite the two-year project proposal, the government knew that further European decisions on launchers would be taken in 1987. Full development of Ariane 5 was approved in November of 1987 and it flew successfully 10 years later.
In the first quarter of 1986 the UK government approved the two-year study, but by 1989 the future of HOTOL was looking bleak and France's Hermes mini shuttle eventually suffered the same fate and was cancelled.
In many respects the seeds for HOTOL's cancellation were sown at the beginning, with uneven support within UK government and its industrial partners, little prospect of European engagement and only the US government ready to embrace the project for its own ends.