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February 07, 2011

Skylon spaceplane

Five papers related from Reaction Engines Limited (who are making the SKylon spaceplane) are in the January, 2011 Journal of the British Interplanetary Society (JBIS). The papers can only be seen by purchasing downloads or buying the journal (or going to a library that has the JBIS).

The papers are about SKYLON’s systems engineering processes and ideas on how SKYLON could support space stations and missions beyond low-Earth-orbit (LEO).

The papers are:

The Requirement Generation Process for the SKYLON Launch System
Mark Hempsell and Roger Longstaff

An Analysis of the SKYLON Infrastructure
Mark Hempsell

Technical and Operations Design of the SKYLON Upper Stage
Mark Hempsell and Alan Bond

The Interaction between SKYLON and the International Space Station
Mark Hempsell

A Design for an Orbital Assembly Facility for Complex Missions
Simon Feast and Alan Bond


Skylon summary from Wikipedia

Skylon is a design by the British company, Reaction Engines Limited (REL), for an unpiloted spaceplane. 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 (US$1000/kg as of 2011, including the costs of research and development, with costs expected to fall much more over time after the initial expenditures have amortised. The cost of the program has been estimated by the developer to be about $12 billion.

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. It would then release a 12-tonne payload, then re-enter the atmosphere. The payload would be carried in a standardised payload container or passenger compartment.

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) 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 easier time during atmospheric reentry compared to other vehicles due to a low ballistic coefficient. Because of the low ballistic coefficient, Skylon would end up slowing down at higher altitudes where the air is thinner, meaning the skin of the vehicle would only reach 1100 Kelvin (K). 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. However, due to turbulent flow around the wings during re-entry, some parts of Skylon would need to be actively cooled. 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. Because this wheel design distributes the weight of the aircraft and the force of its landing over a smaller area of the runway, it will need to operate from a specially strengthened runway. It will possess a retractable undercarriage with high pressure tires and water cooled brakes. 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. 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 is unneeded. The payload fraction would be more than twice that of normal rockets and the vehicle should be fully reusable (200 times or more)

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. Originally the key technology for this type of precooled jet engine did not exist—the required heat exchanger was about 10 times lighter than the state of the art. However, research has now achieved the necessary performance

52 page User manual (Jan 2010)

SKYLON Configuration C2 Features

Length 83.3 m
Fuselage diameter. 6.75 m
Wingspan 25. 4 m
Unladen mass 53 tonnes
Propellant mass 277 tonnes
Nominal take-off mass 345 tonnes
Maximum air-breathing thrust 2 x 1350 kN
Isp in air-breathing mode 35000 N s / kg
Maximum thrust in rocket mode 2 x 1800 kN
Isp in rocket mode 4500 N s / kg
Thrust range (rocket mode) 55% - 100%
Operational life 200 flights


Interview from late 2009 with Mark Hempsell

Hobbyspace had an interview with Mark Hempsell of REL

The technology programme (in 2009 and through mid-2011) is intended to deal with the few items in the engine that are not standard rocket technology. The main thing we are looking at is a heat exchanger that cools and compresses the air before it enters the engine. This has not really been done before in flight conditions. The technology programme is proving that we can build these heat exchangers in a factory on a commercial basis and that they work as we expect them to. We are also looking at changing the coolant in the combustion chamber because our engine cycle needs to use the oxygen rather than hydrogen. Thirdly we are looking at a new type of E-D (expansion Deflection) nozzle, this is not a key technology but would be nice to have.

The next step is more engine demonstrators, making up full engines, some flight testing- re-entry vehicles, structural testing and so on, which we are discussing and is going well. We need to finalise the design of the main vehicle and do detailed design so we can have it flying in 2018

At the moment it looks likely the majority of the £12 billion could come from private investors. {but they have now submitted a proposal to the British Government to request additional funding for the Skylon project.}

I [Mark Hempsell] worked at British Aerospace on HOTOL with Alan (Bond), then taught at Bristol University for a number of years, and joined the company when they were in a position to go forward with the project.

Our company policy is to get everything ready to proceed and build the vehicle. Our business plan is to build heat exchangers while other larger companies like Airbus built the airframe.

I don’t think there is any point in going sub orbital; it is very difficult to make the business plan work. While it may be possible to make an operating profit it won’t be enough to pay back off the development costs or fund development of follow on vehicles. We feel that orbital is the way ahead, there is already a large market for orbital vehicles and Skylon will be able to undercut them significantly and repay the investments even at the current market size.

(Virgins) it doesn’t reach orbit and only has 1/25th of the energy needed to do so. The air launched orbital version is basically the same as Pegasus, and will have quite high costs like any other expendable vehicle. While there may be a market for such a vehicle it is not going to change the way we get into space.



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