The general baseline design concept consists of a fully-reusable booster and passenger stage arranged in parallel.
The two-stage, vertical-takeoff configuration concept consists of a large unmanned booster and a manned stage designed for 50 passengers and 2 crew members. The fully-reusable vehicle is accelerated by a total of eleven liquid rocket engines (9 for the booster, 2 for the passenger stage), which are to be operated using cryogenic liquid oxygen (LOX) and hydrogen (LH2).
The concept design also foresees the passenger cabin to function as an autonomous rescue capsule which can be separated from the vehicle in case of an emergency, allowing the passengers to return safely to Earth.
After engine cut-off, the orbiter stage is to enter a high-speed gliding flight phase and be capable of traveling long intercontinental distances within a very short time. Altitudes of 80 kilometers and Mach numbers beyond 20 are projected, depending on the mission. Flight times of the SpaceLiner from Australia to Europe should take just 90 minutes or no more than 60 minutes on the Europe – California route.
Acceleration loads for the passengers on these missions are 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.
Several other shorter intercontinental missions exist, which potentially generate a larger market demand. For this reason a SpaceLiner configuration derivative has been studied, which could transport up to 100 passengers. In order to keep the number of different stage configurations at the lowest possible level, the potentially interesting flight destinations have been divided into three classes:
These three mission classes could be served flexibly by a suitable combination of four different vehicles (however with a lot of commonality in subcomponents such as engines): 50 and 100 passenger orbiter stages, and large and shortened boosters.
Several advanced technologies are required for the realization of the SpaceLiner which are currently under investigation at DLR and with international partners.
A few examples:
The SpaceLiner 7 achieves an excellent hypersonic L/D of 3.5 up to M=14 without flap deflection, assuming a fully-turbulent boundary layer. Mach contours of SpaceLiner 7-1 passenger stage at M= 10, angle of attack alfa = 6° from ESA-ESTEC Euler CFD- calculation:
Staged combustion cycle rocket engines with a moderate 16 MPa chamber pressure have been selected as the baseline propulsion system. The engine performance data are not overly ambitious and have already been surpassed by existing engines such as the SSME or RD-0120. However, the ambitious goal of a passenger rocket is to considerably enhance reliability and reusability of the engines beyond the current state-of-the-art.
The maximum acceptable temperature of any passive TPS on the SpaceLiner is 1850 K. The leading edge and nose areas exceed this limit and need advanced active cooling.
In those areas where the heatflux and temperatures exceed those values acceptable for CMC, transpiration cooling using liquid water is one potential technical option. This innovative method has been experimentally tested in DLR’s arc heated facility in Cologne using subscale probes of different porous ceramic materials.
Sippel, M.; Schwanekamp, T.; Trivailo, O.; Lentsch, A.: Progress of SpaceLiner Rocket-Powered High-Speed Concept, IAC-13-D2.4.05, IAC2013, Beijing, September 2013
Van Foreest, A., Sippel, M.; Gülhan, A.; Esser, B.; Ambrosius, B.A.C.; Sudmeijer, K.: Transpiration Cooling Using Liquid Water, Journal of Thermophysics and Heat Transfer, Vol. 23, No. 4, October–December 2009
Schwanekamp, T.; Bauer, C.; Kopp, A.: The Development of the SpaceLiner Concept and its Latest Progress, 4TH CSA-IAA CONFERENCE ON ADVANCED SPACE TECHNOLOGY, Shanghai, September 2011
Schwanekamp, T.; Bütünley, J.; Sippel, M.: Preliminary Multidisciplinary Design Studies on an Upgraded 100 Passenger SpaceLiner Derivative, AIAA2012-5808, 18th AIAA International Space Planes and Hypersonic Systems and Technologies Conference, Tours, September 2012
Reimer, Th.; Kuhn, M.; Gülhan, A.; Esser, B.; Sippel, M.; van Foreest, A.: Transpiration Cooling Tests of Porous CMC in Hypersonic Flow, AIAA2011-2251, 17th International Space Planes and Hypersonic Systems and Technologies Conference, 2011