Passenger safety is one of the main drivers for the development of future trans-atmospheric transportation systems. The high levels of energy associated hypersonic flights as well as the level of reliability of the enabling technology leads to the need of a passenger escape system in case of flight abort.
The implementation of a cabin escape system for a hypersonic aircraft is challenged by the integration within a larger structure, the load factors for the passengers, the ejection propulsion concept, the capability to withstand extreme thermal environment(plasma flow)and the adaptability to a wide range of abort scenario conditions (low and high speed and altitude).
This 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 (ex: capsule adapted to outer mold line). Thus a single shape cannot provide adequate performances and consequently it can be challenging (ex: load factors) for the wellness of the ordinary passengers expected in the cabin. The increase of the lifting capability after ejection of a escape capsule and the increase of aerodynamic control surfaces is a strong requirement in order to safely return to ground the crew – composed by non-trained persons.
The main goal of HYPMOCES is to investigate and develop the technologies in the area of control, structures, aerothermodynamics, mission and system required to enable the use of morphing in escape systems for hypersonic transport aircrafts. 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 the 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.
Ejecting safely from transatmospheric flight
Transatmospheric aircraft combine the properties of an aeroplane and a spaceship. Passenger safety is key to getting advanced concepts off the ground, and a new cabin escape system will make a major contribution.
Complex flight conditions create associated challenges for the design of an advanced passenger escape system necessary in case of flight abort. An EU consortium launched the project 'Hypersonic morphing for a cabin escape system' (http://hypmoces.deimos-space.com/ (HYPMOCES)) to develop the required technologies.
A large and morphing cabin escape system that can automatically reconfigure after ejection will enable meeting complicated constraints. These include compactness for integration with the mother aircraft, adaptability to an unpredictable post-abort environment and flight performance for safe landing. The innovation exists in the inflatable sidewalls and deployable rudders.
The design of the pre-ejected system (before deployment) came from previous studies related to a partner's suborbital hypersonic passenger transport concept (SpaceLiner). Excellent teamwork from the outset resulted in selection of preliminary designs for the baseline and backup morphing concepts given the pre-deployment configuration. A variety of analyses have addressed integration of systems both within the cabin escape system and within the mother aircraft.
Computational methods have facilitated modelling and analysis of the three concepts. Scientists are assessing and optimising aerodynamics under numerous conditions and identifying the flight corridors for atmospheric re-entry. The optimal morphing point has been identified for each of the optimised descent trajectories.
The thermal protection system is a critical component of any transatmospheric flight system as re-entry into the atmosphere creates tremendous heat due to a combination of compression and friction with atmospheric molecules. A design study has been completed and analyses of materials, structures and loads have been done as well. Thermomechanical analyses of all components of the thermal protection system and the cabin escape system designs have been complied into a specification document.
A single structure cannot meet the requirements of changing flight conditions during ejection and re-entry. A morphing cabin escape system will enable a compact design within the mother aircraft, increased lift after ejection and increased aerodynamic control for safe return to ground by non-trained persons. HYPMOCES is on its way to a breakthrough in technologies to help transatmospheric hypersonic passenger spacecraft take flight.