Future commercial hypersonic flight will require an orbiter stage which, after main engine cut-off, will enter a high-speed gliding flight phase and will be capable of attaining altitudes of 80 km and Mach numbers beyond Mach 20. This vehicle would travel long intercontinental distances within a very short time--flight times from Australia to Europe would take just 90 minutes, Europe to California no more than 60 minutes.
A new kind of high-speed transport based on a two-stage Reusable Launch Vehicle (RLV) has been proposed by DLR, the national aeronautics and space research center of the Federal Republic of Germany, under the name “SpaceLiner”. The two-stage vehicle will be powered by rocket propulsion. Several advanced technologies are required for the realization of SpaceLiner which are currently under investigation at DLR and with international partners.
Passenger safety is one of the main obvious goals for the development of this future trans-atmospheric transportation system. For this reason acceleration loads for passengers will be designed to remain below those of the Space Shuttle astronauts, with a maximum of 2.5 g being experienced during the propelled section of the flight. Also for safety reasons the high levels of energy associated with this type of flight (hypersonic) as well as the level of reliability of the enabling technology leads to the need for a passenger escape system in case of an aborted flight.
The implementation of a cabin escape system for a hypersonic aircraft is challenging on several levels: integration within the larger launch vehicle, load factors for passengers, the ejection propulsion concept, the capability to withstand an extreme thermal environment (the thermal protection system is a critical component of any trans-atmospheric flight system as re-entry into the atmosphere creates tremendous heat due to a combination of compression and friction with atmospheric molecules) and adaptability to a wide range of abort scenario conditions (low and high speed and different altitudes).
Any successful approach to a hypersonic flight escape system will require breakthroughs in current technologies in the area of control, structures, aerothermodynamics and other systems. Researchers have come up with an innovative morphing concept based on an inflatable vehicle sidewall and deployable rudders. The concept, funded by the EU and called HYPMOCES (for Hypersonic Morphing for a Cabin Escape System) is being worked on by a consortium composed of four main partners from four different European countries: Deimos Space S.L.U.(Spain), DLR (Germany), AVIOSPACE (Italy) and ONERA (France).
The multi-phase nature of the return flight makes morphing an attractive solution for a hypersonic escape system. The abort scenarios cover a wide range of flight conditions and the integration within the mother spacecraft requires compact solutions in terms of shape. Thus, a single shape cannot provide adequate performance and can be challenging with regard to the wellness of the ordinary passengers expected in the cabin. An increase of the lifting capability after ejection of an escape capsule and the increase of aerodynamic control surfaces is considered a strong requirement in order to safely return the passengers and crew.
A large cabin escape system able to change its shape and automatically reconfigure during an abort event after ejection will balance the compromise between the constraints for integration within the mother aircraft (compactness), the adaptability to the unpredicted environment in case of abort and the required flight performance to ensure safe landing.
The HYPMOCES project will address key technological areas to enable the use of morphing in hypersonic escape systems, namely:
- Control and Reconfiguration during morphing.
- System integration within the escape system and within the mother aircraft.
- Structures, materials, actuators and mechanism of the deployed elements.
- Aerothermodynamics of the changing external shape after ejection.