Fuselage Diameter:
Wingspan:
Unladen Mass:
Fuel Mass:
Maximum Payload Mass:
6.25m
25m
41,000kg
220,000kg
12,000kg
During atmospheric flight, control is provided by aerodynamic surfaces:
- An all moving tail fin provides yaw control.
- A delta foreplane (canards) provide pitch control.
- Ailerons extending along the entire wing trailing edge provide roll control.
During the rocket powered ascent the combustion chambers are gimballed to provide pitch, yaw and roll control. Once in space, reaction control thrusters take over from these control surfaces.
Takeoff and Landing
The vehicle takes off and lands using a relatively conventional retractable undercarriage. By special attention to the brake system it has proved possible to achieve an acceptably low undercarriage mass. However, a heavily reinforced runway will be needed to tolerate the high equivalent single wheel load.
At the start of the take-off roll the vehicle weighs 275 tonnes, whilst maximum landing weight is 55 tonnes. At take-off the vehicle carries approximately 66 tonnes of liquid hydrogen and approximately 150 tonnes of liquid oxygen for the ascent.
The ground handling operations will be carried out using a standard aircraft tractor and a bonded goods cargo building permitting overhead loading and protection from the elements. For safety and operational simplicity the cryogenic propellants are loaded subcooled without venting of vapour. Cryogen loading is automatic through services connecting in the undercarriage wells whilst the vehicle is stood on the fuelling apron.
Material Construction
Skylon's fuselage and wing load bearing structure is made from carbon fibre reinforced plastic and consists of stringers, frames, ribs and spars built as warren girder structures. The aluminium propellant tankage is suspended within this, free to move under thermal and pressurisation displacements.
The external shell (the aeroshell) is made from a fibre reinforced ceramic and carries only aerodynamic pressure loads which are transmitted to the fuselage structure through flexible suspension points. This shell is thin (0.5mm) and corrugated for stiffness. It is free to move under thermal expansion especially during the latter stages of the aerodynamic ascent and re-entry.
Payload Capabilities
The Sklyon payload bay is 4.6m diameter and 12.3m long. It has been designed to be compatible with expendable launcher payloads but in addition to accept standard aero transport containers which are 8 foot square in cross section and 10, 20, 30 or 40 feet long. It is anticipated that cargo containerisation will be an important step forward in space transport operations, enabling the "clean" payload bay to be dispensed with.
The vehicle can deliver 12 tonnes to a 300km equatorial orbit, 10.5 tonnes to a 460km equatorial spacestation or 9.5 tonnes to a 460km x 28.5 deg spacestation when operating from an equatorial site.
Although essentially a cargo carrier the payload bay can accommodate tankage for propellant supply to orbit based operations, upper stages for orbit transfer operations and, once endurance certification is achieved, a cabin module for 30 passengers.
Skylon provides no payload support being purely a transport system.
Propellants
Skylon employs two Sabre hybrid airbreathing/rocket engines. These engines employ liquid hydrogen fuel with atmospheric air up to Mach 5.5 and on board liquid oxygen beyond that to orbital velocities.
Whilst on orbit the main propellant tanks are vented and allowed to warm to ambient conditions. Propulsion and attitude control are provided by the Orbital Manoeuvering System (OMS) or Reaction Control System (RCS). This uses a common LH2/LO2 propellant storage which is heavily insulated and cryogenically cooled. This system can remain operational on orbit up to 7 days. The RCS employs gaseous propellants supplied by the Gaseous Propellant Supply System (GPSS). The GPSS also supplies reactants to the fuel cells and the auxiliary power turbines.
Re-entry
During re-entry, which occurs at an altitude between 90 to 60km the heat is radiated away from the hot aeroshell. Heat is prevented from entering the vehicle by layers of reflecting foil and the low conductivity shell support posts. Liquid hydrogen is evaporated in the main tanks, passed through thermal screens to intercept the small residual heat leak and then vented overboard.
