Skylon

=__**Skylon**__=
 * //Project Type// || **Single Stage to orbit (SSO) Spaceplane** ||
 * //Function// || **Transport materials and crew to Low Earth Orbit** ||
 * //Operating body// || **Reaction engines** ||
 * //Host Nation// || **United Kingdom / International** ||
 * //Program cost// ||  ||
 * //Cost per vehicle// ||  ||
 * Take off || Horizontal Takeoff and Landing ||
 * //Life support// || **Yes** ||
 * //Crew// ||  ||
 * Reusable || Yes ||
 * //Status// || **Research and development** ||

**__Introduction__**
Skylon is a single stage to orbit (SSO) space plant which uses sabre engines. These use jet power for initial elevation then rockets to achieve low earth orbit. Crucially this significantly cuts down on the amount of reaction mass due to the jet engines burning atmosphere. In addition to this, in the low altitude, high pressure environment initial launch, gaining altitude using a more horizontal jet take off is more efficient than vertical rocket take off. The massive fuel tanks are either side of the payload bay. This bay would be used to transport materials into a low earth orbit or contain a crew module to transport people.

**__Interesting videos__**
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**__Useful links__**

 * Reaction engines SKYLON page http://www.reactionengines.co.uk/skylon.html

=Reaction Engines Skylon 10/04/2011= From Wikipedia, the free encyclopedia

The vehicle design is for a hydrogen-powered aircraft that would take off from a conventional runway, and accelerate to [|Mach 5.4] at 26 km using atmospheric air before switching the engines to use the internal [|liquid oxygen (LOX)] supply to take it to orbit.[|[][|4][|]] It would then release its payload, which can weigh up to 12-tonnes, and [|re-enter] the [|atmosphere]. The payload would be carried in a standardised payload container or passenger compartment. During re-entry the relatively light vehicle would fly back through the atmosphere and land back at the runway, with its skin protected by a [|ceramic] [|composite]. It would then undergo inspection and any necessary maintenance and, if the design goal is achieved, be able to fly again within two days. As of 2010, only a small portion of the funding required to develop and build Skylon has been secured. The research and development work on the [|SABRE] engine design is proceeding under a small [|European Space Agency (ESA)] grant. In January 2011, REL submitted a proposal to the British Government to request additional funding for the Skylon project. [[|hide]]
 * ~ Skylon ||
 * = [[image:http://upload.wikimedia.org/wikipedia/en/thumb/c/cc/Skylon_climbing.jpg/300px-Skylon_climbing.jpg width="300" height="140" link="http://en.wikipedia.org/wiki/File:Skylon_climbing.jpg"]] ||
 * = The Skylon vehicle is an aircraft designed to reach orbit. ||
 * ~ Role || Re-usable [|Spaceplane] ||
 * ~ National origin || [|UK]/multinational ||
 * ~ Designed by || [|Reaction Engines Limited] ||
 * ~ Status || [|Research and development] ||
 * ~ Program cost || Projected to be £7.1 billion[|[][|1][|]] (~$12 billion est. 2004)[|[][|2][|]] ||
 * ~ Unit cost || £190 million (projected)[|[][|1][|]] ||
 * ~ Developed from || **Horizontal Take-Off and Landing** ([|HOTOL]) project ||
 * Skylon** is a design for an unpiloted [|spaceplane] by the British company, [|Reaction Engines Limited] (REL). It uses a combined-cycle, air-breathing jet engine to [|reach orbit in a single stage]. A fleet of vehicles is envisaged; the design is aiming for re-usability up to 200 times. In paper studies, the costs per kilogram of payload are hoped to be lowered from the current £15,000/kg to £650/kg (as of 2011 [|[update]] ),[|[][|3][|]] including the costs of [|research and development] (R&D), with costs expected to fall much more over time after the initial expenditures have amortised.[|[][|2][|]] The cost of the program has been estimated by the developer to be about $12 billion.
 * ==Contents==
 * [|1] [|Technology and innovations]
 * [|1.1] [|Structure of the fuselage]
 * [|1.2] [|SABRE Engines]
 * [|1.3] [|"Single Stage to Orbit" capability]
 * [|1.4] [|Payload bay]
 * [|2] [|Current project status]
 * [|3] [|Research and development programme]
 * [|4] [|Economics and political will]
 * [|5] [|Specifications]
 * [|6] [|See also]
 * [|7] [|References]
 * [|8] [|External links] ||

Technology and innovations
The Skylon [|spaceplane] is designed as a two-engine, "tailless" aircraft, which is fitted with a steerable [|canard.]

Structure of the fuselage
The [|fuselage] of Skylon is expected to be carbon fibre [|space frame]; a light and strong structure that supports the weight of the aluminium [|fuel tanks] and to which the ceramic [|skin] is attached.[|[][|5][|]] Multiple layers of reflective foil [|thermal insulation] fill the spaces of the frame.[|[][|6][|]] The currently proposed Skylon model C2 will be a physically large vehicle, with a length of 82 metres (269 ft) and a diameter of 6.3 metres (21 ft).[|[][|7][|]] Because it will use a low-density [|liquid hydrogen] fuel, a great volume is needed to contain enough energy to reach orbit. The propellant is intended to be kept at low pressure to minimise stress; a vehicle that is both large and light has an advantage during [|atmospheric reentry] compared to other vehicles due to a low [|ballistic coefficient].[|[][|8][|]] Because of the low ballistic coefficient, Skylon would be slowed at higher altitudes where the air is thinner. As a result, the skin of the vehicle would only reach 1100 [|Kelvin] (K).[|[][|9][|]] In contrast, the smaller [|Space Shuttle] is heated to 2000 K on its [|leading edge], and so employs an extremely heat-resistant but extremely fragile silica [|thermal protection system]. The Skylon design need not use such a system, instead opting for using a far thinner yet durable reinforced ceramic skin.[|[][|2][|]] However, due to turbulent flow around the wings during re-entry, some parts of Skylon would need to be actively cooled.[|[][|6][|]] Skylon would employ a highly-loaded tightly spaced wheel assembly, to save weight and also interior space when the wheels are retracted into the [|fuselage].[|[][|10][|]] Because this wheel design distributes the weight of the aircraft and the force of its landing over a smaller area of the runway, it would require a specially strengthened runway.[|[][|11][|]] It will possess a retractable [|undercarriage] with high pressure tires and water cooled brakes.[|[][|12][|]] If problems were to occur just before a take-off the brakes would be applied to stop the vehicle, the water boiling away to dissipate the heat.[|[][|12][|]] Upon a successful take-off, the water would be [|jettisoned], thus reducing the weight of the undercarriage by many tons. During landing, the empty vehicle would be far lighter, and hence the water would be unneeded.[|[][|12][|]] The [|payload fraction] would be significantly greater than normal rockets and the vehicle should be fully reusable (200 times or more).[|[][|13][|]]

SABRE Engines
Main article: [|Reaction Engines SABRE] One of the significant features of the Skylon design is the engine, called [|SABRE].[|[][|14][|]][|[][|15][|]] The engines are designed to operate much like a conventional [|jet engine] at up to around [|Mach] 5.5 (1700 [|m/s]),[|[][|15][|]] 26 kilometres (16 mi) altitude, beyond which the air inlet closes and the engine operates as a highly efficient [|rocket] to [|orbital speed].[|[][|15][|]] The [|Reaction Engines Limited] [|Synergistic Air-Breathing Rocket Engine (SABRE)] engine is a key component of the Skylon spaceplane.

The [|proposed engine] for the vehicle is not a [|scramjet], but a jet engine running [|combined cycles] of a [|precooled jet engine], [|rocket engine] and [|ramjet].[|[][|2][|]] Originally the key technology for this type of precooled jet engine did not exist as it required a heat exchanger that was ten times lighter than the state of the art.[|[][|16][|]] Research conducted since then has achieved the necessary performance.[|[][|14][|]] Operating an air-breathing jet engine at up to Mach 5.5 is difficult.[|[][|15][|]] Several previous engines proposed by other designers have been good as jet engines but performed poorly as rockets.[|[][|15][|]] This engine design aims to be a good jet engine within the atmosphere, as well as being an excellent rocket engine outside.[|[][|15][|]] The problem with operating at Mach 5.5 has been that the air coming into the engine heats up as it is compressed into the engine, which can cause the engine to overheat.[|[][|15][|]] Attempts to avoid these issues typically make the engine much heavier ([|scramjets]/[|ramjets]) or greatly reduce the thrust (conventional turbojets/ramjets).[|[][|15][|]] In either case the end result is an engine that has a poor [|thrust to weight ratio] at high speeds, resulting in an engine that is too heavy to assist much in reaching orbit.[|[][|15][|]] The SABRE engine design aims to avoid this by using some of the [|liquid hydrogen] fuel to [|cool the air at the inlet].[|[][|15][|]] The air is then used for combustion much like in a conventional jet.[|[][|15][|]] Because the air is cooled at all speeds, the jet can be built of light [|alloys] and the weight is roughly halved.[|[][|15][|]] Additionally, more fuel can be burnt at high speed.[|[][|15][|]] Beyond Mach 5.5, the air would still be unusably hot despite the cooling, so the air inlet closes and the engine relies solely on on-board [|liquid oxygen] and hydrogen fuel as in a normal rocket.[|[][|15][|]] Because the engine uses the atmosphere as [|reaction mass] at low altitude, it will have a high [|specific impulse] (around 2,800 seconds), and burn about one fifth of the propellant that would have been required by a conventional rocket.[|[][|15][|]] Therefore, it would be able to take off with much less total propellant than conventional systems.[|[][|15][|]] This, in turn, means that it doesn't need as much [|lift] or [|thrust], which permits smaller engines, and allows [|conventional wings] to be used.[|[][|15][|]] While in the atmosphere, using wings to counteract [|gravity drag] is more fuel-efficient than simply expelling propellant (as in a rocket), again reducing the total amount of propellant needed.[|[][|15][|]]

"Single Stage to Orbit" capability
See also: [|Single-stage-to-orbit] A vehicle that can fly to orbit without staging is known as [|single stage to orbit] (SSTO).[|[][|17][|]] Proponents of SSTO claim that staging causes a number of problems such as being difficult, expensive or even impossible to recover, reuse and reassemble the parts and therefore believe that SSTO designs hold the promise of reducing the cost of space-flight.[|[][|17][|]] The Skylon design aims to take off from its specially strengthened [|runway], fly into [|low earth orbit], [|re-enter the atmosphere], and land back on its runway like a conventional [|aeroplane], without staging, while being fully [|reusable].[|[][|4][|]]

Payload bay
The [|payload bay] of the Skylon C2 design is a cylinder 12.3 metres (40.4 ft) long and 4.6 metres (15 ft) in diameter.[|[][|10][|]] It is designed to be comparable with current payload dimensions, and yet able to support the [|containerization] of payloads that Reaction Engines hopes for in the future.[|[][|10][|]] To an [|equatorial orbit], Skylon could deliver 12 tonnes (26,455 lb) to a 300 kilometres (186 mi) height or 10.5 tonnes (23,149 lb) to a 460 kilometres (286 mi) altitude.[|[][|10][|]] It could also launch 9.5 tonnes (20,944 lb) to the orbit of the [|International Space Station], when launching from the equator.[|[][|10][|]] Using interchangeable payload containers, Skylon could be fitted to carry satellites or fluid cargo into orbit, or, in a specialised habitation module, up to 30 [|astronauts] in a single launch.[|[][|18][|]][|[][|19][|]]

Current project status
As of 2010, the funding required to develop and build the entire craft has not yet been secured, and so current research and development work is focused on the engines, under an ESA grant of [|€]1 million.[|[][|20][|]] In January 2011, REL submitted a proposal to the British Government requesting additional funding for the Skylon project.[|[][|3][|]]

Research and development programme
The [|Skylon] was developed from the ill-fated British [|HOTOL] project.

Skylon is based upon a previous project of [|Alan Bond], which was known as [|HOTOL].[|[][|21][|]] The development programme of HOTOL began in 1982, a time when space technology was moving towards [|reusable launch systems] such as the American [|Space Shuttle].[|[][|21][|]] In conjunction with [|British Aerospace] and [|Rolls Royce], a design emerged that proved highly promising, so much so that the British Government donated £2 million to further their work.[|[][|21][|]] However, in 1988, the Conservative government withdrew funding, and the development programme was terminated.[|[][|21][|]] Following this major setback, Alan Bond decided to set up his own company, [|Reaction Engines Limited], with the hope of continuing development with private funding.[|[][|21][|]] After having secured funding, the design of the craft was revisited, undergoing a rigorous redesign throughout much of the 1990s.[|[][|21][|]] In the last decade, Reaction Engines has been working with the [|University of Bristol] to develop the engines vital to the success of Skylon. The STRICT/STERN engines produced by this programme were deemed a great success.[|[][|16][|]] The next stage of development is to construct a full-sized working prototype of the SABRE Engine.[|[][|22][|]] The differences between Skylon and its predecessor are numerous. For example, HOTOL was to have been launched from a [|rocket sled] (to save weight), whereas Skylon uses a conventional retractable [|undercarriage].[|[][|21][|]] Skylon also uses a different engine design; the SABRE engine is expected to offer higher performance.[|[][|14][|]] Another issue that the Skylon design aims to circumvent was the intrinsically poor stability of HOTOL.[|[][|21][|]] The weight of the rear-mounted engine tended to make the HOTOL vehicle flip over mid-flight due to the centre of mass lying behind the centre of drag.[|[][|21][|]] Attempts to fix this problem ended up sacrificing much of the potential payload that the HOTOL vehicle could carry, and contributed to the failure of the project.[|[][|21][|]] Skylon would solve this by placing the engines at the end of the wings closer to the centre of the vehicle and thus moving the [|centre of mass] forward, ahead of the centre of [|drag].[|[][|5][|]][|[][|21][|]] The complete Skylon project has a projected R&D cost of over $10 billion and will continue for another 7–10 years.[|[][|2][|]] In February 2009, the [|British National Space Centre] (now the [|UK Space Agency]) and [|ESA] announced that they were partially funding work with [|€]1 million Euros ($1.28 million dollars) on Skylon's engine to produce a demonstration engine by 2011.[|[][|23][|]][|[][|24][|]][|[][|25][|]] The Technology Demonstration Programme will last approximately 2.5 years and will benefit from another [|€]1 million from the ESA.[|[][|26][|]] This programme will take Reaction Engines Ltd from a [|Technology Readiness Level] (TRL) of 2/3 up to 4/5.[|[][|27][|]] The former UK Minister for Science and Innovation in 2009, [|Lord Drayson], commented on Skylon in a speech: "This is an example of a British company developing world-beating technology with exciting consequences for the future of space."[|[][|3][|]]

Economics and political will
Once operative, Skylon could potentially lower satellite costs from the current £15,000/kg to £650/kg, according to evidence submitted to the [|UK parliament] by Reaction Engines Ltd.[|[][|3][|]] However, funding and support from the British government has not been easy to establish.[|[][|28][|]] Request for funding from the British government was undertaken in 2000, with a proposal that could have offered a large potential return on investment.[|[][|29][|]] The request was not taken up at that time. Subsequent discussions with the [|British National Space Centre] led to agreement in 2009 on a co-funding agreement between BNSC, ESA and REL to continue technology development for the SABRE engine.[|[][|30][|]][|[][|31][|]] Testing of the SABRE engine will commence in June 2011 with the start of Phase 3 in the Skylon development programme.[|[][|3][|]] Pre-orders are expected in the 2011–2013 time frame coinciding with the formation of the manufacturing consortium.[|[][|3][|]] According to [|David Willetts], the [|UK] [|Minister of State for Universities and Science]: > "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."[|[][|3][|]]

Specifications
//Data from// the Skylon User Manual[|[][|10][|]] **General characteristics** **Performance**
 * Skylon** **C2**
 * **Crew:** automated
 * **Capacity:** 40
 * **Length:** 83.3 m (273 ft)
 * **[|Wingspan]:** 25.4 m (82 ft)
 * **Height:**
 * **[|Empty weight]:** 53,000 kg (120,000 lb)
 * **Loaded weight:** 345,000 kg (760,000 lb)
 * **Powerplant:** 2 × [|SABRE]synergistic combined cycle jet engine
 * **Dry thrust:** 2,700 LT; 3,000 ST (2,700 LT; 3,000 ST) each
 * **Thrust with [|afterburner]:** 3,500 LT; 4,000 ST (3,500 LT; 4,000 ST) each
 * **[|Maximum speed]:** orbital
 * **[|Range]:** orbital
 * **[|Service ceiling]:** 26,000 m air breathing, >200 km exoatmospheric (85,000 ft air breathing, >124 mi exoatmospheric)
 * **[|Thrust/weight]:** ~1.2 – 3 at burnout (~0.768 atmospheric)SSTO
 * Fuselage diameter: 6.75 m (22.15 ft)
 * Maximum payload mass: 12,000 kg (26,000 lb)
 * [|Specific impulse]: 3560 s (35 kN·s/kg) atmospheric, 450 s (4.4 kN·s/kg) exoatmospheric[|[][|10][|]]
 * SABRE engine thrust/weight ratio: up to 14 atmospheric