14th AlAA/AHI Space Planes and Hypersonic Systems and Technologies Conference AIAA2006-7984 ALAA2006-7984 Preliminary Definition of Supersonic and Hypersonic Airliner Configurations Martin Sippel',Josef Klevanski Space Launcher Systems Analysis(SART),DLR,51170 Cologne,Germany The propulsion system investigations of the EU sponsored LAPCAT study require the definition of generic reference vehicles to e.g.define the thrust level or assess a specific engine performance considering the reference mission of non-stop Brussels to Sydney flight. This paper describes DLR's Space Launcher Systems Analysis SART group's iterative definition of two configurations:The generic supersonic cruise airplane for a cruise Mach number of about four(designated LAPCAT-M4)is considerably enlarged compared to an earlier NASA design to meet the ambitious range requirement.Its propulsion system is based on Turbo-RAM with JP-propellant.The generic hypersonic Mach 8 cruise airplane (LAPCAT-M8)has been initially based on an innovative concept dubbed HyperSoar.The latter configuration uses hydrogen as fuel and an RBCC propulsion system.The paper gives an overview on the recent conceptual design status of the two passenger cruise vehicles presenting geometrical size and mass data and describing results of trajectory simulations and thus actually achievable range.Crucial system related design issues of the propulsion system,especially for the RBCC,will be discussed and critically assessed.Finally,an alternative technical option for high speed intercontinental passenger transport without air- breathing propulsion will be presented as a competitive benchmark. Nomenclature D Drag N M.Ma Mach-number T Thrust N W weight N 1 body length 今 m mass kg 9 dynamic pressure Pa sfe specific fuel consumption g/kNs sfr fuel consumption per range kg/km angle of attack flight path angle expansion ratio Subscripts,Abbreviations CAD computer aided design CFD Computational Fluid Dynamics CFRP Carbon Fiber Reinforced Polymer EASA European Aviation Safety Agency FAA Federal Aviation Administration GLOW Gross Lift-Off Mass 'Department Head,Space Launcher Systems Analysis(SART),DLR,51170 Cologne,Germany,Member AIAA "Aerospace Engineer,Space Launcher Systems Analysis(SART),DLR,51170 Cologne,Germany 1 American Institute of Aeronautics and Astronautics Paper 2006-7984 Copyright2006 by DLR-SART.Published by the American Institute of Aeronautics and Astronautics,Inc.,with permission
American Institute of Aeronautics and Astronautics Paper 2006-7984 1 AIAA 2006-7984 Preliminary Definition of Supersonic and Hypersonic Airliner Configurations Martin Sippel* , Josef Klevanski** Space Launcher Systems Analysis (SART), DLR, 51170 Cologne, Germany The propulsion system investigations of the EU sponsored LAPCAT study require the definition of generic reference vehicles to e.g. define the thrust level or assess a specific engine performance considering the reference mission of non-stop Brussels to Sydney flight. This paper describes DLR’s Space Launcher Systems Analysis SART group’s iterative definition of two configurations: The generic supersonic cruise airplane for a cruise Mach number of about four (designated LAPCAT-M4) is considerably enlarged compared to an earlier NASA design to meet the ambitious range requirement. Its propulsion system is based on Turbo-RAM with JP-propellant. The generic hypersonic Mach 8 cruise airplane (LAPCAT-M8) has been initially based on an innovative concept dubbed HyperSoar. The latter configuration uses hydrogen as fuel and an RBCC propulsion system. The paper gives an overview on the recent conceptual design status of the two passenger cruise vehicles presenting geometrical size and mass data and describing results of trajectory simulations and thus actually achievable range. Crucial system related design issues of the propulsion system, especially for the RBCC, will be discussed and critically assessed. Finally, an alternative technical option for high speed intercontinental passenger transport without airbreathing propulsion will be presented as a competitive benchmark. Nomenclature D Drag N M, Ma Mach-number - T Thrust N W weight N l body length m m mass kg q dynamic pressure Pa sfc specific fuel consumption g/kNs sfr fuel consumption per range kg / km α angle of attack - γ flight path angle - ε expansion ratio - Subscripts, Abbreviations CAD computer aided design CFD Computational Fluid Dynamics CFRP Carbon Fiber Reinforced Polymer EASA European Aviation Safety Agency FAA Federal Aviation Administration GLOW Gross Lift-Off Mass * Department Head, Space Launcher Systems Analysis (SART), DLR, 51170 Cologne, Germany, Member AIAA ** Aerospace Engineer, Space Launcher Systems Analysis (SART), DLR, 51170 Cologne, Germany 14th AIAA/AHI Space Planes and Hypersonic Systems and Technologies Conference AIAA 2006-7984 Copyright © 2006 by DLR-SART. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission
HSCT High Speed Civil Transport JP (hydrocarbon)Jet Propellant(kerosene) LAPCAT Long-Term Advanced Propulsion Concepts and Technologies LH2 Liquid Hydrogen LLNL Lawrence Livermore National Laboratory LOX Liquid Oxygen MECO Main Engine Cut Off OPR Overall Pressure Ratio RBCC Rocket Based Combined Cycle SERN semi expansion ramp nozzle SST Supersonic Transport TBCC Turbine Based Combined Cycle TET Turbine Entry Temperature TRL Technology Readiness Level VCE Variable Cycle Engine cog center of gravity 0.0 sea-level,static I.Introduction The EU sponsored LAPCAT study investigates different types of advanced propulsion systems for supersonic and hypersonic cruise airplanes.LAPCAT addresses advanced high-speed air-breathing propulsion concepts.The first scientific and technological objective of the multinational research project is further outlined in [1]as: "..to evaluate two advanced airbreathing concepts:a Turbine or Rocket Based Combined Cycle (TBCC/RBCC) capable of achieving the ultimate goal to reduce long-distance flights,e.g.from Brussels to Sydney,to less than 2 to 4 hours.Two reference vehicles including their characteristic trajectory points have to be established." In LAPCAT the definition of both reference vehicles and their trajectories has been performed by DLR-SART.The statement on the Brussels to Sydney route translates into a range requirement of at least 16700 km along the orthodrome and hypersonic flight conditions. The design approach has been structured as: Identification of past projects on similar hypersonic cruise airplanes Critical recalculation of the past projects Definition of the baseline flight vehicles by adaptation and improvement of the investigated concept Iterative vehicle adaptation,taking into account latest,more elaborate data of LAPCAT propulsion work packages II.Supersonic Cruise Airplane at Mach 4.5 A.NASA Langley and Lockheed Mach 4 Airplane Study In 1990 NASA Langley and Lockheed Engineering Sciences Company conducted a study to configure and analyze a 250-passenger,Mach 4 high-speed civil transport with a design range of 6500 nautical miles(12045.8 km) [4].The design mission assumed an all-supersonic cruise segment and no community noise or sonic boom constraints.The study airplane was developed in order to examine the technology requirements for such a vehicle and to provide an unconstrained baseline from which to assess changes in technology levels,sonic boom limits,or community noise constraints in future studies 4. The general arrangement of the airplane is illustrated in Figure 1.The concept employs a blended wing-body with a modified blunt nose,a highly swept inboard wing panel,and a moderately swept outboard wing panel with curved,raked wingtips.Total length of the vehicle reaches almost 95 m. 2 American Institute of Aeronautics and Astronautics Paper 2006-7984
American Institute of Aeronautics and Astronautics Paper 2006-7984 2 HSCT High Speed Civil Transport JP (hydrocarbon) Jet Propellant (kerosene) LAPCAT Long-Term Advanced Propulsion Concepts and Technologies LH2 Liquid Hydrogen LLNL Lawrence Livermore National Laboratory LOX Liquid Oxygen MECO Main Engine Cut Off OPR Overall Pressure Ratio RBCC Rocket Based Combined Cycle SERN semi expansion ramp nozzle SST Supersonic Transport TBCC Turbine Based Combined Cycle TET Turbine Entry Temperature TRL Technology Readiness Level VCE Variable Cycle Engine cog center of gravity 0,0 sea-level, static I. Introduction The EU sponsored LAPCAT study investigates different types of advanced propulsion systems for supersonic and hypersonic cruise airplanes. LAPCAT addresses advanced high-speed air-breathing propulsion concepts. The first scientific and technological objective of the multinational research project is further outlined in [1] as: "… to evaluate two advanced airbreathing concepts: a Turbine or Rocket Based Combined Cycle (TBCC/RBCC) capable of achieving the ultimate goal to reduce long-distance flights, e.g. from Brussels to Sydney, to less than 2 to 4 hours. Two reference vehicles including their characteristic trajectory points have to be established." In LAPCAT the definition of both reference vehicles and their trajectories has been performed by DLR-SART. The statement on the Brussels to Sydney route translates into a range requirement of at least 16700 km along the orthodrome and hypersonic flight conditions. The design approach has been structured as: • Identification of past projects on similar hypersonic cruise airplanes • Critical recalculation of the past projects • Definition of the baseline flight vehicles by adaptation and improvement of the investigated concept • Iterative vehicle adaptation, taking into account latest, more elaborate data of LAPCAT propulsion work packages II. Supersonic Cruise Airplane at Mach 4.5 A. NASA Langley and Lockheed Mach 4 Airplane Study In 1990 NASA Langley and Lockheed Engineering & Sciences Company conducted a study to configure and analyze a 250-passenger, Mach 4 high-speed civil transport with a design range of 6500 nautical miles (12045.8 km) [4]. The design mission assumed an all-supersonic cruise segment and no community noise or sonic boom constraints. The study airplane was developed in order to examine the technology requirements for such a vehicle and to provide an unconstrained baseline from which to assess changes in technology levels, sonic boom limits, or community noise constraints in future studies [4]. The general arrangement of the airplane is illustrated in Figure 1. The concept employs a blended wing-body with a modified blunt nose, a highly swept inboard wing panel, and a moderately swept outboard wing panel with curved, raked wingtips. Total length of the vehicle reaches almost 95 m
Four advanced afterburning turbojet engines are mounted in two nacelles on the wing lower surface adjacent to the fuselage.The propulsion system selected for the NASA-study consists of four conceptual single-rotor, augmented(afterburning)turbojets using thermally stabilized jet fuel. The Lockheed-NASA estimated dry weight is given at 130 Mg and with 288 Mg kerosene propellant the total lift-off weight including crew,passengers,and their luggage reaches 448 Mg.This mass estimation could not be fully attested by a DLR-SART calculation [2].In any case the LAPCAT mission range is by almost 40%larger than NASA's 12000 km,which requires a re-design. 1530 10.0 32s 12125 Figure 1:NASA Mach 4 supersonic cruise airplane proposal from 1990 [4](all dimensions in ft) B.LAPCAT-M4 The new supersonic cruise airplane has to be considerably enlarged compared to the earlier NASA design to meet its ambitious range requirement.To keep the wing loading in an acceptable range the wing size has been increased to 1600 m2(+36%).The span grows almost proportionally by 16%,while the total length reaches 102.78 m which is only slightly longer(+8.8%)than the HSCT proposal. The general arrangement of the generic airplane geometry is illustrated in Figure 2 through Figure 4;principal geometric dimensions are presented in Table 1.The LAPCAT-M4 employs similar to the NASA concept a blended wing-body with a modified platypus nose,a highly swept inboard wing panel,and a moderately swept outboard wing panel (see Figure 3).The inboard wing panel is swept 78,allowing the flow component normal to its leading edge to remain subsonic even at the Mach 4.5 cruise condition.The high sweep allows relatively blunt leading edges without a substantial zero-lift wave drag penalty.The inboard leading edge has a fixed geometry,free of high-lift devices,resulting in a simpler and lighter wing structure.The outboard wing panel is swept 55 but its exact, possibly curved form has not been defined yet.The total wing is inclined with a positive angle of attack of approximately 2.75.Note that this angle and the wing's airfoil are not optimized yet and might be adapted,if required. The forebody of the concept is slender and elliptical in cross section.Like the NASA concept,the fuselage is windowless to simplify the structural design and environmental control.The wing-mounted struts of the main landing gear should retract into the engine nacelles and are housed between the inlet ducts as in [4].The two- wheeled nose gear is mounted on the bulkhead forward of the crew station and retracts forward. Four advanced turbo-RAM-jet engines are mounted in two nacelles on the wing lower surface adjacent to the fuselage.The location of the engine and nacelles is still open for adaptation if required by trim as long as they remain under the wing.The axial-symmetric geometry and the size of the air-intakes,nacelles and nozzles as shown in Figure 2 and Figure 4 are not representative of the actual LAPCAT design.A rectangular shape of the air-intake with vertical ramps as in [4]is the preferred design option.The detailed propulsion system definition is described in reference 3. Fuel is carried in integral wing tanks and in a single aft fuselage tank.It is further assumed that the vehicle uses thermally stabilized jet fuel (TSJF)because the existing airport infrastructure is designed around conventional jet fuel.A single vertical stabilizer is attached to the upper part of the aft fuselage(see Figure 2 and Figure 4). 3 American Institute of Aeronautics and Astronautics Paper 2006-7984
American Institute of Aeronautics and Astronautics Paper 2006-7984 3 Four advanced afterburning turbojet engines are mounted in two nacelles on the wing lower surface adjacent to the fuselage. The propulsion system selected for the NASA-study consists of four conceptual single-rotor, augmented (afterburning) turbojets using thermally stabilized jet fuel. The Lockheed-NASA estimated dry weight is given at 130 Mg and with 288 Mg kerosene propellant the total lift-off weight including crew, passengers, and their luggage reaches 448 Mg. This mass estimation could not be fully attested by a DLR-SART calculation [2]. In any case the LAPCAT mission range is by almost 40 % larger than NASA’s 12000 km, which requires a re-design. Figure 1: NASA Mach 4 supersonic cruise airplane proposal from 1990 [4] (all dimensions in ft) B. LAPCAT-M4 The new supersonic cruise airplane has to be considerably enlarged compared to the earlier NASA design to meet its ambitious range requirement. To keep the wing loading in an acceptable range the wing size has been increased to 1600 m2 (+ 36%). The span grows almost proportionally by 16 %, while the total length reaches 102.78 m which is only slightly longer (+ 8.8 %) than the HSCT proposal. The general arrangement of the generic airplane geometry is illustrated in Figure 2 through Figure 4; principal geometric dimensions are presented in Table 1. The LAPCAT-M4 employs similar to the NASA concept a blended wing-body with a modified platypus nose, a highly swept inboard wing panel, and a moderately swept outboard wing panel (see Figure 3). The inboard wing panel is swept 78°, allowing the flow component normal to its leading edge to remain subsonic even at the Mach 4.5 cruise condition. The high sweep allows relatively blunt leading edges without a substantial zero-lift wave drag penalty. The inboard leading edge has a fixed geometry, free of high-lift devices, resulting in a simpler and lighter wing structure. The outboard wing panel is swept 55° but its exact, possibly curved form has not been defined yet. The total wing is inclined with a positive angle of attack of approximately 2.75°. Note that this angle and the wing's airfoil are not optimized yet and might be adapted, if required. The forebody of the concept is slender and elliptical in cross section. Like the NASA concept, the fuselage is windowless to simplify the structural design and environmental control. The wing-mounted struts of the main landing gear should retract into the engine nacelles and are housed between the inlet ducts as in [4]. The twowheeled nose gear is mounted on the bulkhead forward of the crew station and retracts forward. Four advanced turbo-RAM-jet engines are mounted in two nacelles on the wing lower surface adjacent to the fuselage. The location of the engine and nacelles is still open for adaptation if required by trim as long as they remain under the wing. The axial-symmetric geometry and the size of the air-intakes, nacelles and nozzles as shown in Figure 2 and Figure 4 are not representative of the actual LAPCAT design. A rectangular shape of the air-intake with vertical ramps as in [4] is the preferred design option. The detailed propulsion system definition is described in reference 3. Fuel is carried in integral wing tanks and in a single aft fuselage tank. It is further assumed that the vehicle uses thermally stabilized jet fuel (TSJF) because the existing airport infrastructure is designed around conventional jet fuel. A single vertical stabilizer is attached to the upper part of the aft fuselage (see Figure 2 and Figure 4)
0 [w]Z 5 1 emt日 0102030405060708090100 X [m] Figure 2:LAPCAT-M4 projection in the x-z-plane(nacelle design not representative) 2 10 5 0 5 -10 6 20 25 30 0102030405060708090100 X [m] Figure 3:LAPCAT-M4 projection in the x-y-plane Z N 0 -5 ELLLL 30 20 10 0 -10 -20 -30 Y [m] Figure 4:LAPCAT-M4 projection in the y-z-plane(nacelle design not representative) The large,slightly inclined wing might help to achieve a good maximum L/D of 7.8 at a small angle of attack and cruise Mach number 4.5 according to preliminary DLR-analysis.Actually,a high L/D is essential to achieve the ambitious range requirement. The total take-off mass of the supersonic cruise airplane has been iterated in the first loop to the huge value of 702.6 Mg [2]and has been recently slightly increased to 720 Mg,which is well beyond any supersonic passenger aircraft built to date.The dry mass is estimated at 184.5 Mg and the structural index is at a for airplanes low 36.8 % According to current data the LAPCAT-M4 would be able to transport about 200 passengers with their luggage.The 4 American Institute of Aeronautics and Astronautics Paper 2006-7984
American Institute of Aeronautics and Astronautics Paper 2006-7984 4 Figure 2: LAPCAT-M4 projection in the x-z-plane (nacelle design not representative) Figure 3: LAPCAT-M4 projection in the x-y-plane Figure 4: LAPCAT-M4 projection in the y-z-plane (nacelle design not representative) The large, slightly inclined wing might help to achieve a good maximum L/D of 7.8 at a small angle of attack and cruise Mach number 4.5 according to preliminary DLR-analysis. Actually, a high L/D is essential to achieve the ambitious range requirement. The total take-off mass of the supersonic cruise airplane has been iterated in the first loop to the huge value of 702.6 Mg [2] and has been recently slightly increased to 720 Mg, which is well beyond any supersonic passenger aircraft built to date. The dry mass is estimated at 184.5 Mg and the structural index is at a for airplanes low 36.8 %. According to current data the LAPCAT-M4 would be able to transport about 200 passengers with their luggage. The
high sensitivity of the configuration to mass changes and the ambitious mass goals of some components should be noted. Table 1:Major geometrical data of the LAPCAT-M4 configuration LAPCAT-M4 overall length [m] 102.78 overall height [m] 11.45 fuselage diameter [m] 4.13 fuselage length (incl.Nose)[m] 102.78 wing span [m] 54.15 wing mean aerodynamic chord(MAC)[m] 29.54 wing inboard span [m] 24.29 maximum wing thickness chord [m] 1.5 exposed wing area [m2] 1600 wing leading edge sweep angle [deg. 78° wing trailing edge sweep angle [deg.] 5° wing outboard span [m] 29.86 wing outboard leading edge sweep angle [deg. 56° outboard trailing edge sweep angle [deg.] 30° fin height m] 5.11 fin mean aerodynamic chord(MAC)[m] 8.7 maximum fin thickness chord [m] 0.35 exposed fin area [m2] 44.5 fin leading edge sweep angle [deg.] 69° fin trailing edge sweep angle [deg. 30.0 nose radius [m] 0.055 aerodynamic reference area [m2] 1600 aerodynamic reference length [m] 102.77 The NASA selection of four conceptual single-rotor,augmented(afterburning)turbojets has been used as a baseline in the preliminary sizing of [2].However,the engine type is slightly changed from pure augmented turbojet to combined Turbo-RAM propulsion to enable an increased cruise Mach number of up to 4.5.A detailed critical description of the engine selection process including the investigation of advanced propulsion options using Variable Cycle Engines(VCE)are described in [3]. The complete flight trajectory of LAPCAT-M4 from take-off,via ascent,acceleration to the supersonic cruise descent and landing approach has been simulated using control algorithms described in [2].The calculation ends after depletion of nominal propellants with descent to sea-level altitude.The vehicle follows almost the orthodrome, however,with some deviations to avoid some densely populated areas,adding about 200 km to the shortest great circle route.It's no objective in LAPCAT to proof if the chosen track is actually acceptable for supersonic high altitude flight.Nevertheless,the propulsion system performance should be assessed under realistic operational conditions.Thus,a significant portion of the trajectory (from Brussels in eastern direction up to Volgograd)is assumed to be flown in subsonic cruise. Under these hypotheses LAPCAT-M4 with the available 484.8 Mg of JP-fuel does not fully reach its final destination Sydney but at least arrives after 15989 km in central Australia(145.9 E:26.4S).Flight time is 23811 s (6.6 h).It has not been intended to further enlarge the vehicle to finally fulfill the mission goal.Such work could be the subject ofa separate study while LAPCAT focuses on propulsion system research. Therefore,the obtained results demonstrate the principle feasibility of a TBCC-powered ultra long-haul supersonic airliner.The VCE-214 engine variant with relatively high OPR shows the best performance of all investigated types as long as potentially different engine masses are not taken into account [3].Figure 5 reveals some interesting features of the intercontinental cruise trajectory performance in the form of vehicle fuel American Institute of Aeronautics and Astronautics Paper 2006-7984
American Institute of Aeronautics and Astronautics Paper 2006-7984 5 high sensitivity of the configuration to mass changes and the ambitious mass goals of some components should be noted. Table 1: Major geometrical data of the LAPCAT-M4 configuration LAPCAT-M4 overall length [m] 102.78 overall height [m] 11.45 fuselage diameter [m] 4.13 fuselage length (incl. Nose) [m] 102.78 wing span [m] 54.15 wing mean aerodynamic chord (MAC) [m] 29.54 wing inboard span [m] 24.29 maximum wing thickness @ chord [m] 1.5 exposed wing area [m2 ] 1600 wing leading edge sweep angle [deg.] 78° wing trailing edge sweep angle [deg.] 5° wing outboard span [m] 29.86 wing outboard leading edge sweep angle [deg.] 56° outboard trailing edge sweep angle [deg.] 30° fin height [m] 5.11 fin mean aerodynamic chord (MAC)[m] 8.7 maximum fin thickness @ chord [m] 0.35 exposed fin area [m2 ] 44.5 fin leading edge sweep angle [deg.] 69° fin trailing edge sweep angle [deg.] 30.0 nose radius [m] 0.055 aerodynamic reference area [m2 ] 1600 aerodynamic reference length [m] 102.77 The NASA selection of four conceptual single-rotor, augmented (afterburning) turbojets has been used as a baseline in the preliminary sizing of [2]. However, the engine type is slightly changed from pure augmented turbojet to combined Turbo-RAM propulsion to enable an increased cruise Mach number of up to 4.5. A detailed critical description of the engine selection process including the investigation of advanced propulsion options using Variable Cycle Engines (VCE) are described in [3]. The complete flight trajectory of LAPCAT-M4 from take-off, via ascent, acceleration to the supersonic cruise, descent and landing approach has been simulated using control algorithms described in [2]. The calculation ends after depletion of nominal propellants with descent to sea-level altitude. The vehicle follows almost the orthodrome, however, with some deviations to avoid some densely populated areas, adding about 200 km to the shortest great circle route. It’s no objective in LAPCAT to proof if the chosen track is actually acceptable for supersonic high altitude flight. Nevertheless, the propulsion system performance should be assessed under realistic operational conditions. Thus, a significant portion of the trajectory (from Brussels in eastern direction up to Volgograd) is assumed to be flown in subsonic cruise. Under these hypotheses LAPCAT-M4 with the available 484.8 Mg of JP-fuel does not fully reach its final destination Sydney but at least arrives after 15989 km in central Australia (145.9° E; 26.4° S). Flight time is 23811 s (6.6 h). It has not been intended to further enlarge the vehicle to finally fulfill the mission goal. Such work could be the subject of a separate study while LAPCAT focuses on propulsion system research. Therefore, the obtained results demonstrate the principle feasibility of a TBCC-powered ultra long-haul supersonic airliner. The VCE-214 engine variant with relatively high OPR shows the best performance of all investigated types as long as potentially different engine masses are not taken into account [3]. Figure 5 reveals some interesting features of the intercontinental cruise trajectory performance in the form of vehicle fuel
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 2006-7984
American 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
Sustaining propulsion burns Mesosphere Stratosphere Ozone layer Jet aircraftN Mt.Everest Troposphere Range (scale is compressed) Figure 6:Principle idea of the HyperSoar trajectory Figure 7:Artists impression of the HyperSoar 2000 configuration However,this preliminary evaluation should be regarded with a high degree of skepticism.Almost no data can be found on the propulsion system performance characteristics of HyperSoar.The concept developer at LLNL Preston Carter,published a paper on periodic hypersonic cruise [6].This study used an ejector RAMJET/- SCRAMJET rocket engine.Therefore,it seems quite reasonable that a similar RBCC is the basic propulsion system of HyperSoar.The specific impulse model as presented in [6]seems to be very simplified,at least on the ejector rocket side.Very limited historical data of experiments or flight tests on air-augmented rockets have been published. Although the SART assumptions for the recalculation in [2]are less euphoric,the performance data still represent ideal values because actual intake,combustion chamber,and nozzle characteristics were not taken into account D.LAPCAT-M8 The new generic hypersonic cruise airplane for LAPCAT has been initially based on the HyperSoar 2000 shape despite some concerns on its flyability.However,for defining the size and the propulsion system thrust requirements this approach is still acceptable.LAPCAT-M8 is considerably enlarged compared to HyperSoar to accommodate the passengers and the cabin and to meet the ambitious LAPCAT range requirement.Since the beginning of the study the hypersonic-M8 configuration had to be redefined already two times. The TRL of RBCC propulsion is low and a high degree of uncertainty exists on its actually achievable performance in ejector-rocket and SCRAM-mode.Therefore,an iterative approach in defining the thrust requirements and subsequent calculation of the mission performance has been chosen.As the LAPCAT study is in focus of far-term propulsion concepts [1],usually optimistic engine performance assumptions are drawn.This approach is maintained not only in case of missing validation by an actual flight test but also if the efficiency could not yet be demonstrated in a ground experiment.This important difference should be kept in mind if obtained data are compared with the other two transportation options of the chapters II and IV which are based on propulsion systems with much more advanced TRL All variants described here are based on LH2 propellant and on LOX as the oxidizer in rocket mode.Hydro- carbon propellants had also been regarded at an early phase but fuel consumption was found tremendously high due to the poor specific impulse in ejector-rocket operation mode.Therefore,all hydrocarbons were dropped quite early in the study as a feasible propellant for LAPCAT-M8 [2].The following paragraphs give a brief overview on the evolution process In the first iteration cycle with the configuration status of June 2005 (see Figure 8)the lifting body's projected area had been increased to 3000 m2(+150 compared to HyperSoar 2000)to keep the wing loading within an acceptable range.The span grew to 34.2 m,while the total length reached 106.1 m (+74 %when compared to HyperSoar 2000 [7]. The preliminary RBCC performance assumptions of the generic LAPCAT hypersonic cruise airliner were more conservative than those of HyperSoar [7].However,engine Isp was used according to ideal RAM and SCRAM performance not taking into account any actual intake and nozzle geometry.Thrust of the propulsion system was selected as required for simulation of a sustainable trajectory.This very optimistic approach was justified at this design stage because the major intention had been in finding the reference operation conditions of the propulsion system. American Institute of Aeronautics and Astronautics Paper 2006-7984
American Institute of Aeronautics and Astronautics Paper 2006-7984 7 Figure 6: Principle idea of the HyperSoar trajectory Figure 7: Artists impression of the HyperSoar 2000 configuration However, this preliminary evaluation should be regarded with a high degree of skepticism. Almost no data can be found on the propulsion system performance characteristics of HyperSoar. The concept developer at LLNL, Preston Carter, published a paper on periodic hypersonic cruise [6]. This study used an ejector RAMJET/- SCRAMJET rocket engine. Therefore, it seems quite reasonable that a similar RBCC is the basic propulsion system of HyperSoar. The specific impulse model as presented in [6] seems to be very simplified, at least on the ejector rocket side. Very limited historical data of experiments or flight tests on air-augmented rockets have been published. Although the SART assumptions for the recalculation in [2] are less euphoric, the performance data still represent ideal values because actual intake, combustion chamber, and nozzle characteristics were not taken into account. D. LAPCAT-M8 The new generic hypersonic cruise airplane for LAPCAT has been initially based on the HyperSoar 2000 shape despite some concerns on its flyability. However, for defining the size and the propulsion system thrust requirements this approach is still acceptable. LAPCAT-M8 is considerably enlarged compared to HyperSoar to accommodate the passengers and the cabin and to meet the ambitious LAPCAT range requirement. Since the beginning of the study the hypersonic -M8 configuration had to be redefined already two times. The TRL of RBCC propulsion is low and a high degree of uncertainty exists on its actually achievable performance in ejector-rocket and SCRAM-mode. Therefore, an iterative approach in defining the thrust requirements and subsequent calculation of the mission performance has been chosen. As the LAPCAT study is in focus of far-term propulsion concepts [1], usually optimistic engine performance assumptions are drawn. This approach is maintained not only in case of missing validation by an actual flight test but also if the efficiency could not yet be demonstrated in a ground experiment. This important difference should be kept in mind if obtained data are compared with the other two transportation options of the chapters II and IV which are based on propulsion systems with much more advanced TRL. All variants described here are based on LH2 propellant and on LOX as the oxidizer in rocket mode. Hydrocarbon propellants had also been regarded at an early phase but fuel consumption was found tremendously high due to the poor specific impulse in ejector-rocket operation mode. Therefore, all hydrocarbons were dropped quite early in the study as a feasible propellant for LAPCAT-M8 [2]. The following paragraphs give a brief overview on the evolution process. In the first iteration cycle with the configuration status of June 2005 (see Figure 8) the lifting body's projected area had been increased to 3000 m2 (+ 150 % compared to HyperSoar 2000) to keep the wing loading within an acceptable range. The span grew to 34.2 m, while the total length reached 106.1 m (+ 74 %) when compared to HyperSoar 2000 [7]. The preliminary RBCC performance assumptions of the generic LAPCAT hypersonic cruise airliner were more conservative than those of HyperSoar [7]. However, engine Isp was used according to ideal RAM and SCRAM performance not taking into account any actual intake and nozzle geometry. Thrust of the propulsion system was selected as required for simulation of a sustainable trajectory. This very optimistic approach was justified at this design stage because the major intention had been in finding the reference operation conditions of the propulsion system
After a good acceleration,mostly carried out by its powerful rocket engines,the early LAPCAT-M8 con- figuration reached the periodic cruise condition in slightly more than 10 minutes.The periodic cruise Mach number was alternated between 9 and 7 while the altitude varied between 32000 m and 50000 m.After approximately 6800 s(1.9 hours)of flight along the orthodrome the hypersonic cruise airplane reached its final destination in the simulations [7]. 106.1m 山 34.2m Figure 8:Generic Mach 8+hypersonic cruise airplane LAPCAT-M8-1 shown in June 2005 status One of the major shortcomings of the early design had been that it was mostly based on a resized HyperSoar and similarly did not take into account the propulsion system demands.Analysis of preliminary specific thrust data-still without relationship to the LAPCAT geometry-revealed that the early air-intake lay-out would not be able to deliver sufficient airflow to the engines.Thus a resizing of LAPCAT-M8 started in November 2005 based on a calculated air-intake which meets the engine mass flow requirement [2].Further,the average skipping cruise Mach number was reduced to benefit from the better specific thrust at lower Mach numbers. The span of the second LAPCAT-M8 generation grew to 38.58 m enabling a larger air-flow capture,while the total length reached 101.8 m [2].The geometry of this generic configuration is shown in Figure 9. 101.8m t■■■■。 38.58m Figure 9:Generic Mach 8 hypersonic cruise airplane LAPCAT-M8-2 shown in November 2005 status American Institute of Aeronautics and Astronautics Paper 2006-7984
American Institute of Aeronautics and Astronautics Paper 2006-7984 8 After a good acceleration, mostly carried out by its powerful rocket engines, the early LAPCAT-M8 configuration reached the periodic cruise condition in slightly more than 10 minutes. The periodic cruise Mach number was alternated between 9 and 7 while the altitude varied between 32000 m and 50000 m. After approximately 6800 s (1.9 hours) of flight along the orthodrome the hypersonic cruise airplane reached its final destination in the simulations [7]. 106.1 m 34.2 m Figure 8: Generic Mach 8+ hypersonic cruise airplane LAPCAT-M8-1 shown in June 2005 status One of the major shortcomings of the early design had been that it was mostly based on a resized HyperSoar and similarly did not take into account the propulsion system demands. Analysis of preliminary specific thrust data –still without relationship to the LAPCAT geometry– revealed that the early air-intake lay-out would not be able to deliver sufficient airflow to the engines. Thus a resizing of LAPCAT-M8 started in November 2005 based on a calculated air-intake which meets the engine mass flow requirement [2]. Further, the average skipping cruise Mach number was reduced to benefit from the better specific thrust at lower Mach numbers. The span of the second LAPCAT-M8 generation grew to 38.58 m enabling a larger air-flow capture, while the total length reached 101.8 m [2]. The geometry of this generic configuration is shown in Figure 9. 101.8 m 38.58 m Figure 9: Generic Mach 8 hypersonic cruise airplane LAPCAT-M8-2 shown in November 2005 status
During flight performance assessment the propulsion efficiency data was not consistent with the actual LAPCAT-M8-2 geometry but was based on generic engine size assumptions.However,the available RAM and SCRAM thrust was already limited by these data's specific thrust and the actual geometry-limited mass flow.The trajectory simulations show that the periodic cruise trajectory is much less sensitive to L/D than steady state cruise. In a relatively short acceleration phase the LAPCAT-M8-2 reached the periodic cruise condition.During that time the initial take-off mass of the vehicle was reduced by more than 250 Mg to slightly below 500 Mg.The axial load factor did not exceed 0.83 g.The periodic cruise Mach number alternated between 6.5 and 8 while the altitude varied between 30000 m and 51000 m.The LAPCAT-M8-2 configuration fell 600 km short of the Brussels to Sydney range requirement of 16700 km for a flight along the orthodrome.After approximately 9000 s(2.5 hours)of simulated flight including a final gliding descent the hypersonic cruise airplane should have reached a distance of 16100km[21. The simulations of November 2005 allowed the preliminary propulsion system component sizing of LAPCAT- M8:the intake,the combustion chamber,and the large semi expansion ramp nozzle(SERN).These components will be subject to experimental and numerical CFD research in LAPCAT [1].The early intake geometry had to be adapted to meet the combustion chamber static entry pressure requirements of at least 100 kPa.A new 2 ramp+flat forebody intake has been defined which fulfills the air-mass flow requirements of LAPCAT-M8-2 taking also care of potentially necessary boundary layer bleed [9].The total height reaches 10.8 m for an engine module width of 2.75 m.The early LAPCAT-M8-2 combustion chamber length of about 20 m has been assessed as not compatible with an acceptable level of internal friction.A preliminary chamber resizing [10]has been performed in LAPCAT including an early assessment of the required isolator length [13]for flight Mach numbers below 8.The RBCC is now designed with the rocket engines located at a backward facing step on top and behind of the isolator similar to a configuration been proposed in reference 14.The nozzle contour has been generated by EADS with the method of characteristics.Its windtunnel contour [15]had to be adapted for the flight vehicle because of height restriction. The dimensioning of the propulsion system components allowed the definition of the lower part of the latest generic LAPCAT-M8 airplane geometry as illustrated in Figure 10 through Figure 12. 10 5 N -10 102030 40 5060708090 100 X [m] Figure 10:LAPCAT-M8 projection in the x-z-plane 20 =二 1 0 5 10 -20 0 1020 3040 506070 80 90 100 X [m] Figure 11:LAPCAT-M8 projection in the x-y-plane 9 American Institute of Aeronautics and Astronautics Paper 2006-7984
American Institute of Aeronautics and Astronautics Paper 2006-7984 9 During flight performance assessment the propulsion efficiency data was not consistent with the actual LAPCAT-M8-2 geometry but was based on generic engine size assumptions. However, the available RAM and SCRAM thrust was already limited by these data’s specific thrust and the actual geometry-limited mass flow. The trajectory simulations show that the periodic cruise trajectory is much less sensitive to L/D than steady state cruise. In a relatively short acceleration phase the LAPCAT-M8-2 reached the periodic cruise condition. During that time the initial take-off mass of the vehicle was reduced by more than 250 Mg to slightly below 500 Mg. The axial load factor did not exceed 0.83 g. The periodic cruise Mach number alternated between 6.5 and 8 while the altitude varied between 30000 m and 51000 m. The LAPCAT-M8-2 configuration fell 600 km short of the Brussels to Sydney range requirement of 16700 km for a flight along the orthodrome. After approximately 9000 s (2.5 hours) of simulated flight including a final gliding descent the hypersonic cruise airplane should have reached a distance of 16100 km [2]. The simulations of November 2005 allowed the preliminary propulsion system component sizing of LAPCATM8: the intake, the combustion chamber, and the large semi expansion ramp nozzle (SERN). These components will be subject to experimental and numerical CFD research in LAPCAT [1]. The early intake geometry had to be adapted to meet the combustion chamber static entry pressure requirements of at least 100 kPa. A new 2 ramp + flat forebody intake has been defined which fulfills the air-mass flow requirements of LAPCAT-M8-2 taking also care of potentially necessary boundary layer bleed [9]. The total height reaches 10.8 m for an engine module width of 2.75 m. The early LAPCAT-M8-2 combustion chamber length of about 20 m has been assessed as not compatible with an acceptable level of internal friction. A preliminary chamber resizing [10] has been performed in LAPCAT including an early assessment of the required isolator length [13] for flight Mach numbers below 8. The RBCC is now designed with the rocket engines located at a backward facing step on top and behind of the isolator similar to a configuration been proposed in reference 14. The nozzle contour has been generated by EADS with the method of characteristics. Its windtunnel contour [15] had to be adapted for the flight vehicle because of height restriction. The dimensioning of the propulsion system components allowed the definition of the lower part of the latest generic LAPCAT-M8 airplane geometry as illustrated in Figure 10 through Figure 12. Figure 10: LAPCAT-M8 projection in the x-z-plane Figure 11: LAPCAT-M8 projection in the x-y-plane
10 5 N -5 .10 LLL4山 201510 50-5-10-15-20 Y[m] Figure 12:LAPCAT-M8 projection in the y-z-plane The upper section of the vehicle is dependent on the necessary volume for fuel tanks and the SERN expansion ratio intended to be as far adapted as possible.The vehicle span is influenced by the intake width which is directly proportional to the required thrust.LAPCAT-M8 as a generic airplane is designed as a lifting body with a simple 2D-geometry in the central air-intake part,easing not only the conceptual lay-out but also CFD and experimental investigations.The outboard region converges rapidly to the "wingtips",so that the leading edge sweep angle is about 82.The stabilizer located in the tail part of the lifting body and two vertical fins,slightly inclined outboards, are to be used for aerodynamic trim and control.Their respective sizes are not yet designed by flight dynamic and stability requirements. The principal geometric dimensions are presented in Table 2 Table 2:Major geometrical data of the LAPCAT-M8 configuration LAPCAT-M8 overall length [m] 101.18 overall width [m] 41.58 overall height [m] 19.69 lifting body chord length [m] 91.8 lifting body span [m] 41.58 lifting body maximum airfoil thickness chord [m] 13.62 lifting body leading edge sweep angle [deg.] 82.2° lifting body trailing edge sweep angle [deg. -73° exposed lifting body area [m2] 3593 fin height [m] P fin root chord length [m] 20.8 maximum fin thickness root chord [m] 1.04 exposed fin area [m2] 102 fin leading edge sweep angle [deg.] 70° fin trailing edge sweep angle [deg.] 38° nose radius [m] 0.093 aerodynamic reference area [m] 3000 aerodynamic reference length [m 100 The propulsion system operational requirements resulted in an aerodynamic cross section increase by about 100 to more than 490 m2compared to the previous-M8-2 variant.This development has an unfavorable effect on the vehicle's drag and L/D-ratio.On the other hand the increase of internal volume allows to carry more fuel which is now raised to 668.9 Mg resulting in a take-off mass of 936470 kg.This gigantic mass is almost two times above the largest subsonic airplanes and about five times that of first generation supersonic airliners.Consequently,LAPCAT- M8 is no longer assumed taking-off on its own gear,offering some dry mass savings.Anyway,LAPCAT-M8 10 American Institute of Aeronautics and Astronautics Paper 2006-7984
American Institute of Aeronautics and Astronautics Paper 2006-7984 10 Figure 12: LAPCAT-M8 projection in the y-z-plane The upper section of the vehicle is dependent on the necessary volume for fuel tanks and the SERN expansion ratio intended to be as far adapted as possible. The vehicle span is influenced by the intake width which is directly proportional to the required thrust. LAPCAT-M8 as a generic airplane is designed as a lifting body with a simple 2D-geometry in the central air-intake part, easing not only the conceptual lay-out but also CFD and experimental investigations. The outboard region converges rapidly to the "wingtips", so that the leading edge sweep angle is about 82°. The stabilizer located in the tail part of the lifting body and two vertical fins, slightly inclined outboards, are to be used for aerodynamic trim and control. Their respective sizes are not yet designed by flight dynamic and stability requirements. The principal geometric dimensions are presented in Table 2. Table 2: Major geometrical data of the LAPCAT-M8 configuration LAPCAT-M8 overall length [m] 101.18 overall width [m] 41.58 overall height [m] 19.69 lifting body chord length [m] 91.8 lifting body span [m] 41.58 lifting body maximum airfoil thickness @ chord [m] 13.62 lifting body leading edge sweep angle [deg.] 82.2° lifting body trailing edge sweep angle [deg.] -73° exposed lifting body area [m2 ] 3593 fin height [m] 8 fin root chord length [m] 20.8 maximum fin thickness @ root chord [m] 1.04 exposed fin area [m2 ] 102 fin leading edge sweep angle [deg.] 70° fin trailing edge sweep angle [deg.] 38° nose radius [m] 0.093 aerodynamic reference area [m2 ] 3000 aerodynamic reference length [m] 100 The propulsion system operational requirements resulted in an aerodynamic cross section increase by about 100 % to more than 490 m2 compared to the previous -M8-2 variant. This development has an unfavorable effect on the vehicle's drag and L/D-ratio. On the other hand the increase of internal volume allows to carry more fuel which is now raised to 668.9 Mg resulting in a take-off mass of 936470 kg. This gigantic mass is almost two times above the largest subsonic airplanes and about five times that of first generation supersonic airliners. Consequently, LAPCATM8 is no longer assumed taking-off on its own gear, offering some dry mass savings. Anyway, LAPCAT-M8
