Скайлон: Британский космический самолет одноступенчатого выхода на орбиту.

Single stage to orbit spaceplane

Skylon is a series of concept designs for a reusable single stage to orbit spaceplane by the British company Reaction Engines Limited (Reaction), using SABRE, a combined cycle, air breathing rocket propulsion system. The vehicle design is for a hydrogen fuelled aircraft that would take off from a specially built reinforced runway, and accelerate to Mach 5.4 at altitude (compared to typical airliner's ) using the atmosphere's oxygen before switching the engines to use the internal liquid oxygen (LOX) supply to accelerate to the Mach 25 necessary to reach a 400 km orbit. It would carry of cargo to an equatorial low Earth orbit (LEO); up to to the International Space Station, almost 45% more than the capacity of the European Space Agency's Automated Transfer Vehicle; or to Geosynchronous Transfer Orbit (GTO), over 24% more than SpaceX Falcon 9 launch vehicle in reusable mode
The relatively light vehicle would re enter the atmosphere and land on a runway, being protected from the conditions of re entry by a ceramic matrix composite skin. When on the ground, it would undergo inspection and necessary maintenance, with a turnaround time of approximately two days, and be able to complete at least 200 orbital flights per vehicle. As work on the project has progressed, information has been published on a number of design versions, including A4, C1, C2, and D1. Testing of the key technologies was successfully completed in November 2012, allowing Skylon's design to advance from its research phase to a development phase. , the groundworks for an engine test facility have been completed at Westcott. Current plans are for the plant to be completed and the first ground based engine tests to begin in 2021, and SABRE engines could be performing uncrewed test flights in a "hypersonic testbed" (HTB) by 2025. In paper studies, the cost per kilogram (kg) of payload carried to LEO in this way is hoped to be reduced from the current £1,108/kg (as of 2015), including research and development, to around £650/kg (718.16USD/Kg), with costs expected to fall much more over time after initial expenditures have amortised. In 2004, the developer estimated the total lifetime cost of the Skylon C1 programme to be about $12 billion. contracts for this funding were signed in 2015.

Skylon has its origins within a previous space development programme for an envisioned single stage to orbit (SSTO) spaceplane, known as HOTOL. In 1982, when work commenced on the HOTOL by several British companies, there was significant international interest to develop and produce viable reusable launch systems, perhaps the most high profile of these being the NASA operated Space Shuttle. In conjunction with British Aerospace and Rolls Royce, a promising design emerged to which the British government contributed £2 million towards its refinement; British engineer Alan Bond was amongst the engineers who worked on HOTOL. Following the setback of HOTOL's cancellation, in 1989 Alan Bond, along with John Scott Scott and Richard Varvill decided to establish their own company, Reaction Engines Limited, to pursue the development of a viable spaceplane and associated technology using private funding.

The Skylon design features several distinct differences when compared with the earlier HOTOL program. Whereas HOTOL would have launched from a rocket sled as a weight saving measure, Skylon is to be equipped with conventional retractable undercarriage. The revised engine design, using the SABRE engine, is expected to offer higher performance than its predecessor. The rear mounted engine of HOTOL meant that the vehicle possessed intrinsically poor in flight stability; early attempts to resolve this problem had ended up sacrificing much of HOTOL's payload potential, which in turn contributed to the failure of the overall project. Skylon's solution to the issue was to position its engines at the end of its wings, which located them further forward and much closer to the vehicle's longitudinal centre of mass, thereby resolving the instability problem. Reaction intends ultimately to operate as a for profit commercial enterprise which, upon the completion of development, shall manufacture Skylon vehicles for multiple international customers who shall operate their fleets directly, while being provided with support from Reaction. In service, Skylon could potentially lower the cost of launching satellites which, according to evidence submitted to the UK parliament by Reaction, is forecast to be around £650/kg; as of 2011, the average launch cost using conventional methods was estimated to be roughly £15,000/kg. Reaction has also completed internal studies into the use of Skylon as a launch platform for a network of space based solar power satellites, which have been historically unfeasible due to high launch costs.

Speaking in June 2011, Reaction estimated that it would require ultimately $12 billion to achieve an operational configuration, which was then estimated to be achieved around 2020, dependent on funding. The obtaining of additional financing for the Skylon programme from the British government has often been difficult. During 2000, Reaction issued an ultimately unsuccessful request for funding from the British government; according to the government, Reaction's proposal had involved an offer of a potentially large return on its investment. However, several officials have emerged as proponents and advocated for the official backing of the Skylon programme. Speaking in 2009, the former UK Minister for Science and Innovation, Lord Drayson, stated of Reaction: "This is an example of a British company developing world beating technology with exciting consequences for the future of space." The initiative, known as the Technology Demonstration Programme, was scheduled to last approximately 2.5 years, during which further financing in the form of €1 million was made available by ESA. The 2009 agreement allowed Reaction to involve several external companies, including EADS owned Astrium, the University of Bristol and the German Aerospace Center (DLR), in further development work. By 2012, according to the UK Space Agency, the funding required to develop and construct the entire craft has not yet been secured; as such, research and development work was at that point mainly focused on the engines alone, which was supported by an ESA grant of €1 million. In January 2011, Reaction submitted a proposal to the British Government requesting additional funding for the Skylon project. Speaking on the topic of Skylon in 2011, David Willetts, the UK Minister of State for Universities and Science, stated:
blockquote|The European Space Agency is funding proof of concept work for Skylon from UK contributions. This work is focusing on demonstrating the viability of the advanced British engine technology that would underpin the project. Initial work will be completed in mid 2011 and if the trial is successful, we will work with industry to consider next steps. The grant was contingent upon Reaction having an industrial partner. The first grant of £50 million was approved by the European Commission in August 2015. In October 2015, British defence conglomerate BAE Systems entered into an agreement with Reaction Engines, under which it would invest £20.6 million in Reaction to acquire 20% of its share capital, as well as to provide assistance in the development of the SABRE engine. In July 2016, the second grant of £10 million was approved by ESA. On 25 September 2017 it was announced that the U. S. Defense Advanced Research Projects Agency (DARPA) had awarded a contract to Reaction Engines for an undisclosed amount to conduct high temperature airflow testing at a Colorado, United States site of a Reaction Engines precooler called HTX. Testing work is scheduled to start in 2018. In April 2018, Reaction Engines announced Boeing and Rolls Royce would be joining BAE Systems as investors in the development of the SABRE engine. A total of $37.5 million of new funding is to be provided including contributions from Baillie Gifford Asset Management and Woodford Investment Management.

In 2000, the firm completed work with University of Bristol testing the precooler. From 2007 to 2009 Reaction worked with University of Bristol and Airborne Engineering on Project STERN (Static Test Expansion/Deflection Rocket Nozzle), which tested Reaction's engine ignition system, a Reaction designed air breathing hydrogen rocket engine, and investigated the flow stability and behaviour of with Dr Neil Taylor's expansion deflection nozzle design via multiple test firings by Airborne Engineering. An expansion deflection nozzle is capable of compensating for the changing ambient pressure encountered while gaining altitude during atmospheric flight, thus generating greater thrust and thereby efficiency. Static testing of the engine precooler began in June 2011, marking the start of Phase 3 in the Skylon development programme, In April 2012, Reaction announced that the first series of the precooler test programme had been successfully completed. On 10 July 2012, Reaction announced that the second of three series of tests has been completed successfully, and the final series of tests would begin the following month after the testing facilities had been upgraded to allow testing of 150 °C ( 238 °F) temperatures. ESA's propulsion division audited the precooler tests during mid 2012 and found the results satisfactory. On 9 May 2011, Reaction stated that a preproduction prototype of the Skylon could be flying by 2016, and the proposed route would be a suborbital flight between the Guiana Space Centre near Kourou in French Guiana and the North European Aerospace Test Range, located in northern Sweden. Pre orders are expected in the 2011–2013 time frame coinciding with the formation of the manufacturing consortium. In November 2012, Reaction announced that it would commence work upon a three and a half year project to develop and build a test rig of the SABRE engine to prove its performance across both the air breathing and rocket modes.

The Skylon is a fully reusable SSTO vehicle, able to achieve orbit without staging, which is intended to be used principally as a reusable launch system. Proponents of the SSTO approach have often claimed that staging involves a number of inherent complications and problems due to complexity, such as being difficult or typically impossible to recover and reuse most elements, thus unavoidably incurring great expense to produce entirely new launch vehicles instead; therefore, they believe that SSTO designs hold the promise of providing a reduction to the high cost of space flights. Operationally, it is envisioned for the non crewed Skylon to take off from a specially strengthened runway, gain altitude in a fashion akin to a conventional aeroplane and perform an ascent at very high speeds, in excess of five times the speed of sound , to attain a peak air breathing altitude of roughly 92,000 feet (28042 m), where payloads would typically be launched prior to the vehicle's re entry into the atmosphere, upon which it will conduct a relatively gentle descent before performing a traditional landing upon a runway. Richard Varvill, technical director at Reaction, stated of Reaction's market: "we're competing with expendable rockets, a machine that is only used once". The design of the SABRE engine has drawn heavily upon the STRICT/STERN experimental engines, sharing many features such as the propellant and the adoption of the trialled Expansion Deflection Nozzle, as well as building upon the wider field of liquid air cycle engines (LACE). altitude, beyond which the air inlet closes and the engine operates as a highly efficient rocket to orbital speed. Operating an air breathing jet engine at velocities of up to Mach 5.5 poses numerous engineering problems; several previous engines proposed by other designers have worked well as jet engines, but performed poorly as rockets. The fuselage of the Skylon is expected to be a silicon carbide reinforced titanium space frame; a light and strong structure that supports the weight of the aluminium fuel tanks and to which the ceramic skin is attached. Multiple layers of titanium foil thermal insulation are sandwiched between the skin and frame In contrast, the smaller Space Shuttle was heated to on its leading edge, and so employed an extremely heat resistant but fragile silica thermal protection system. The Skylon design does not require such an approach, instead opting for using a far thinner yet durable reinforced ceramic skin; would be jettisoned. When this feature was introduced in the C1 model of the design the weight of the brakes was reduced from around .

A special runway will be required for launch: it needs to be reinforced to tolerate the high equivalent single wheel load; necessitated by the Skylon's 325 tonnes takeoff weight; it will need to have heat resistant sections at the start of the take off run and at the rotation zone; and it will have to be long to allow the Skylon to accelerate to its rotation speed, yet still have to abort the launch and brake to a standstill if required. At nearly 20,000 feet, this would be the longest paved runway in the world. The Skylon would be able to land on a Code F civil runway. When on the ground, it would undergo inspection and necessary maintenance, with a turnaround time of approximately two days, and be able to complete at least 200 orbital flights per vehicle.