consumption per range(kg/km).The two peaks represent the acceleration phases,with the first in dry mode and the second with full afterburner ignition.The two long-time relatively flat,slightly decreasing sections are the cruise phases,with the first in subsonic dry mode and the second in Mach 4.5 RAM-cruise.On a first look it seems surprising that the RAM-cruise efficiency is better than those of the turbofans in subsonic flight.Although sfc is about more than 2 times above for RAM and L/D is approximately 40%lower at M=4.5,the velocity over ground is 5.4 times higher than at M=0.8.These numbers easily explain the lower cruise consumption of LAPCAT-M4 in supersonic cruise.Simulations show that if a direct acceleration to Mach 4.5 already over the European continent would be acceptable,the HSCT could reach its final destination of Sydney. sfr kg/km] 300 250 200 150 100 50 0- 0 5000 10000 15000 20000 25000 flight time[s】 Figure 5:LAPCAT-M4 fuel consumption per range as a function of flight time m. Hypersonic Cruise Airplane at Mach 8 C.HyperSoar Concept Historically,the proposals on hypersonic cruise airplanes seem to be much rarer than those on supersonic airliners.This is obviously due to the fact that in hypersonics the thermal environment is considerably more demanding.The very high heat flux at sufficient dynamic pressure for the airbreathing engines almost excludes any sustained hypersonic flight. An innovative concept dubbed HyperSoar has been proposed by Lawrence Livermore National Laboratory in the US.The vehicle concept found a large public interest when it was illustrated on the title of Aviation Week&Space Technology magazine in 1998 [5].Designed as a global reach military strike airplane with a flight Mach number of 10,HyperSoar has a unique feature of skipping on the upper atmosphere (see Figure 6).After accelerating with Rocket Based Combined Cycle(RBCC)engines,the vehicle would temporarily shut down its propulsion system and begin a periodic hypersonic cruise trajectory.While the configuration is outside the dense layers of the atmosphere the propulsion system and leading edges could cool down.When it falls back the Scramjet of the RBCC is reignited for a short period to accelerate again for another ballistic arc. In the course of continued research in the US,the notional design of the HyperSoar 1998 vehicle was improved using "Osculating Cone waverider"design.Figure 7 shows the layout of this improved shape.The inlet airflow requirements of the propulsion are more adequately addressed and the aft-body shape and flight control layout are more realistic in this design.DLR-SART has recalculated the HyperSoar 2000 configuration.The recalculation intended to develop the tools for a similar but larger LAPCAT-M8 hypersonic airliner.Independent mass assessment of the HyperSoar 2000 configuration with the DLR mass analysis tool stsm based on similar dimensions and loads delivers an empty weight of 94500 kg(+80%compared to data provided in [5D).With a similar amount of propellant(146200 kg+10000 kg reserves)and a new take-off mass(256200 kg)an intercontinental range with a payload of about 10000 kg does not seem to be completely out of reach on the first look. 6 American Institute of Aeronautics and Astronautics Paper 2006-7984American Institute of Aeronautics and Astronautics Paper 2006-7984 6 consumption per range (kg/km). The two peaks represent the acceleration phases, with the first in dry mode and the second with full afterburner ignition. The two long-time relatively flat, slightly decreasing sections are the cruise phases, with the first in subsonic dry mode and the second in Mach 4.5 RAM-cruise. On a first look it seems surprising that the RAM-cruise efficiency is better than those of the turbofans in subsonic flight. Although sfc is about more than 2 times above for RAM and L/D is approximately 40 % lower at M=4.5, the velocity over ground is 5.4 times higher than at M= 0.8. These numbers easily explain the lower cruise consumption of LAPCAT-M4 in supersonic cruise. Simulations show that if a direct acceleration to Mach 4.5 already over the European continent would be acceptable, the HSCT could reach its final destination of Sydney. sfr [ kg/km ] 0 50 100 150 200 250 300 0 5000 10000 15000 20000 25000 flight time [ s ] Figure 5: LAPCAT-M4 fuel consumption per range as a function of flight time III. Hypersonic Cruise Airplane at Mach 8 C. HyperSoar Concept Historically, the proposals on hypersonic cruise airplanes seem to be much rarer than those on supersonic airliners. This is obviously due to the fact that in hypersonics the thermal environment is considerably more demanding. The very high heat flux at sufficient dynamic pressure for the airbreathing engines almost excludes any sustained hypersonic flight. An innovative concept dubbed HyperSoar has been proposed by Lawrence Livermore National Laboratory in the US. The vehicle concept found a large public interest when it was illustrated on the title of Aviation Week & Space Technology magazine in 1998 [5]. Designed as a global reach military strike airplane with a flight Mach number of 10, HyperSoar has a unique feature of skipping on the upper atmosphere (see Figure 6). After accelerating with Rocket Based Combined Cycle (RBCC) engines, the vehicle would temporarily shut down its propulsion system and begin a periodic hypersonic cruise trajectory. While the configuration is outside the dense layers of the atmosphere the propulsion system and leading edges could cool down. When it falls back the Scramjet of the RBCC is reignited for a short period to accelerate again for another ballistic arc. In the course of continued research in the US, the notional design of the HyperSoar 1998 vehicle was improved using "Osculating Cone waverider" design. Figure 7 shows the layout of this improved shape. The inlet airflow requirements of the propulsion are more adequately addressed and the aft-body shape and flight control layout are more realistic in this design. DLR-SART has recalculated the HyperSoar 2000 configuration. The recalculation intended to develop the tools for a similar but larger LAPCAT-M8 hypersonic airliner. Independent mass assessment of the HyperSoar 2000 configuration with the DLR mass analysis tool stsm based on similar dimensions and loads delivers an empty weight of 94500 kg (+ 80% compared to data provided in [5]). With a similar amount of propellant (146200 kg + 10000 kg reserves) and a new take-off mass (256200 kg) an intercontinental range with a payload of about 10000 kg does not seem to be completely out of reach on the first look