British company Reaction Engines Limited announced on 2nd November 2015 that new agreement with BAE Systems was signed.

Reaction Engines Limited is responsible for designing Skylon spaceplane and agreement is targeted for strengthening and streamlining cooperation between REL and BAE in further development. As we can read on REL site:

“The working partnership will draw on BAE Systems’ extensive aerospace technology development and project management expertise and will provide Reaction Engines Limited with access to critical industrial, technical and capital resources to progress towards the demonstration of a ground based engine – a key milestone in the development of the technology.”

BAE is supposed to invest around £20 million in SABRE engine project. Combined with announced government grant of £60 million it will provide necessary funds for further development of SABRE which is crucial part of Skylon project.

History of Skylon

Skylon is British project of single stage spaceplane capable to reach space without separate launch vehicle. Conception of such plane is dating to World War II German project of hypersonic bomber able to attack targets in USA. It was called Silbervogel and stayed (luckily for Allies) only on blueprints. Idea was ambitious, but it project was strictly military – reaching low orbit was only mean of increasing range but not main objective. After decades, conception materialized in 1982 in three different projects. American “Copper Canyon” project firstly developed by DARPA was announced in the middle of the eighties as a future hypersonic (with speed of 8 Ma and possibility of reaching even 20 Ma) passenger plane. In second half of the eighties project was divided between NASA, DARPA, the US Air Force, the Strategic Defense Initiative Office (SDIO) and the US Navy and resulted in Rockwell X30 project. Due the high costs of creating manned and able to lift cargo technology demonstrator, X30 program was cancelled in 1993. Next conception was born in USSR in 1986 as answer for X30. Tu-2000 was announced as new hypersonic bomber with speed of 24 Ma and payload capacity at 8000 kg. Project was cancelled after collapse of USSR due the lack of funds and economy problems in Russia. But even in case further development, planned capacity was not impressive; experimental hypersonic bomber was tested earlier (XB70) in USA, and it was rejected as economically and militarily ineffective (ICBM were less expensive and were able to play the same role). Third project was developed in Great Britain in the beginning of the eighties. HOTOL (Horizontal Take-Off and Landing) was designed to give opportunity of lifting payload into orbit from conventional runway without using rocket. BAe (predecessor of BAE) started cooperation with Rolls-Royce (famous due their contribution in development of jet engines). RR designed innovative engine RB545, operating like jet engine during start and flight in low atmosphere and with possible of switching into rocket mode in specific height. Secret of propulsion was using atmosphere oxygen for jet mode to reduce amount of oxidizer used in climbing (it would make separate or additional rocket unnecessary) for height where engine will start rocket mode. In spite of fact that project was in the end of design it was cancelled in the end of the eighties due two reasons. First, the limited economic sense – in that times rockets were not significantly more expensive in terms of launch costs. Second reason was aerodynamic problems which were known since project phase. HOTOL was too heavy at the rear (due the large engines). To ensure flight stability it was necessary to add many different heavy hydraulical systems. Unfortunately after redesigning, HOTOL lost most of its payload capacity. Again economical sense of HOTOL came under question. After lost battle between ambitions with economics, BAe tried to restart project in less expensive form, as smaller spaceplane launched with conventional rocket engines from An 225, but again project was rejected.

New beginning

In 2012, after over two decades since HOTOL was cancelled, Reaction Engines Limited announced that main problems of HOTOL were solved, and propulsion finished successfully testing under inspection of ESA. REL was founded in 1989 by one of designers of HOTOL Alan Bond. Alan Bond invented SABRE engine basing on his project of RB545 engine during his working for Rolls-Royce. SABRE is able to operate both as a jet or rocket engine. For jet mode, SABRE is utilizing atmosphere oxygen cooled to almost liquid state. In rocket mode conventional oxidizers are utilized. Two SABRE engines will be propulsion of SKYLON. For now SKYLON is designed as remote controlled, reusable, spaceplane available to lift cargo or men into low orbit. With cargo space in the center, front and rear of construction (based on composite space frame) are fuel tanks. Spaceplane is using canard foreplanes combined with short wings with no tail. It is planned to be reusable up to 200 times. Heat protection during reentry will be ceramic skin with active cooling; due the fact of low ballistic coefficient Skylon should not be able to reach high speeds in high parts of atmosphere where air is thinner. Expensive and vulnerable to damage Thermal Protection System (like in Space Shuttle) will not be necessary (also it will reduce service time between flights). Skylon in present phase of develop is large vehicle. Length is planned at 83.133 m, wingspan at 26.818 m with start weight at 325000 kg. Planned payload capacity with equatorial launch site is up to 17000 kg to 160 km orbit or 2700 kg for 600 km orbit. Skylon is able to lift up to 30 passengers in special module or 24 passengers in combined manned and cargo Skylon Personnel / Logistics Module (SPLM). Skylon is able for space maneuvers and Rendez – Vous with cargo but is not designed for docking. To lift cargo module from Skylon to for example ISS special Skylon Orbiting Facility Interface (SOFI) is required to be attached to transported module. SPLM or any other personnel module will have attached USIS docking port. Skylon will be able to dock with space station or other Skylon equipped with USIS. It is also part of rescue system. As personnel modules are separate construction from Skylon they can provide two days of life supporting in case of Skylon malfunction. It will let other Skylon to start and dock to malfunctioning spaceplane to make possible transferring passengers into safe module. In case of crash during start or landing structure of Skylon will provide shock protection for passengers, and module is equipped in heat shields to protect from burning propellant.

Skylon’s predecessor, HOTOL shared more enthusiasm for its idea in USA than in UK. NASA was seriously interested in participating in HOTOL, unfortunately without positive response from Ministry of Defense. This time, Skylon is considered as a potential successor of Space Shuttle and doubtless one of most interesting and promising projects. Maybe international cooperation between Britain, USA and UE would let Skylon to avoid fate of being only a model on a shelf.