Hypersonic Wind Tunnel Test of Flare-type Membrane Aeroshell for Atmospheric Entry Capsule Kazuhiko Yamada (JAXA) Masashi Koyama (The University of Tokyo) Yusuke Kimura (Aoyama Gakuin University) Kojiro Suzuki (The University of Tokyo) Takashi Abe (JAXA) A.Koichi Hayashi (Aoyama Gakuin University) Supported by Wind Tunnel Technology Center in ARD/JAXA
CONTENTS Background Objectives Experimental setup and model Results *Behavior of membrane aeroshell *Aerodynamic coefficient *Aerodynamic heating environment Conclusions
BACKGROUND New and innovative Atmospheric entry vehicle was proposed. Low-ballistic-coefficient atmospheric entry system using flexible aeroshell Aeroshell is deployed by injecting the inflate gas in vacuum and zerogravity condition in orbit. Vehicle re-enters into atmosphere with low aerodynamic heating and make soft landing without a parachute thanks to the large and low-mass aeroshell. Packed aeroshell is transported to orbit beforehand. And aeroshell and payload is connected before re-entry. Capsule Compression ring (Inflatable torus) Flare-type Aeroshell (Thin membrane)
Key technology 1) To develop a large but low-mass flexible aeroshell utilizing Inflatable structure Development and demonstration of reliable deployment system Understanding structural strength of inflatable structure. 2) To develop and evaluate flexible material Development of gas tight and high heat resistance material Analysis on inside of multilayered membrane Demonstration of durability in atmospheric entry condition 3) To understand aerodynamic characteristics Confirmation of stability in wide range of Mach number. To obtain aerodynamic characteristic ti data (drag coefficient) ient) Investigation of aerodynamic heating environment. To solve some issues in these key technology by Hypersonic wind tunnel test
OBJECTIVES To confirm the durability and decelerating capability of flexible aeroshell in hypersonic flow. To understand the characteristics of flare-type membrane aeroshell in hypersonic flow Behavior of membrane aeroshell Aerodynamic characteristics Aerodynamic heating environment To investigate t the effect of aeroshell configuration focusing on the flare angle in this presentation.
Experimental Setup and Model
Hypersonic wind tunnel Test was carried out using JAXA Φ1.27m Hypersonic wind tunnel which is located in JAXA Chofu Space Center. Mach number 10.0 (Fixed nozzle) Nozzle exit diameter Φ1.27m Stagnation temperature 850~1200K Stagnation pressure 1.0~9.9MPa Heater Outside of Test section
Freestream Condition This test was carried out in the calmest flow condition of this hypersonic wind tunnel Mach Number 9.45 Uniform flow velocity 1320m/s To ~950K Static temperature 48K Po 1.0MPa Static pressure e 34.3Pa 3 Static density 2.45 10-3 kg/m 3 By Tauber s eq. Stagnation Heat flux 112kW/m 2 (R N =0.01m) Comparison with actual low-ballistic-coefficient lli i t reentry condition Reentry trajectory Vehicle mass : 100kg Aeroshell diameter :10m Initial orbit : circler orbit in altitude of 400km Initial pass angle : 3 degree Mach Number 24 Uniform flow velocity 6600m/s Static temperature 192K Static pressure 0.1Pa Static density 1.9 10-6 kg/m 3 Stagnation heat flux 80kW/m 2 (R N =0.5m)
Experimental Model Experimental model consisted on Hemispherical metal head Flare-type membrane aeroshell made of ZYLON textile Aluminum torus frame imitating an inflatable torus. The junction of aeroshell with either the head or the frame was reinforced by thicker ZYLON cloth Model specification Aeroshell diameter 140 mm Head diameter 20 mm Stagnation curvature radius 10 mm Torus tube diameter 10 mm Maximum diameter 160 mm Flare angle 45 or 60 F45 model Flare angle is 45 degrees F60 model Flare angle is 60 degrees
Flexible Aeroshell In Hypersonic Flow The behavior of the flexible aeroshell and flow field around the model Flare angle = 45 deg (F45 model) Flare angle = 60 deg (F60 model) Both aeroshells are quit stable and there are no significant oscillation. Shock wave is significantly oscillated. One bow shock generated and flow field is quit stable
Aerodynamic Coefficient The relation between angle of attack and drag and lift coefficient of F45 model and F60 model. Inclination of frame vs AoA Drag coefficient of F60 model is larger than F45 model. F60 model is suitable to decelerating device Lift coefficient of F60 model is more sensitive than F45 model. F60 model have similar characteristics as rigid aeroshell.
Measurement of Aerodynamic Heating Surface temperature is measured by infrared thermography Model is mounted on high speed model injection device. And infrared thermography was set in test section Time history of surface temperature is obtained in 15Hz High speed model injection device Infrared thermography continued in pressure vessel Experimental model Surface temperature of aeroshell reached 500 degc
Estimation Method Aerodynamic heating (heat flux) is estimated from surface temperature history on the basis of heat balance on the model surface. <Stagnation (Vespel)> Quasi-one-dimensional head conduction equation, assuming hemispheric shape Governing equation dt ρsc pv = κ S dt x <Flare (ZYLON)> T x Boundary condition T C T Surface : κ = q εσt + εσt x T Center : κ = 0 x PA 4 4 0 1 i C PA T0 Simple equation; heat balance between convection aerodynamic heating and radiative cooling, assuming that the temperature is constant in depth direction dt C T ρ hc pz = q + dt pa 4 4 0 1 2 εσ T 2 εσ Ti CPAT 0
Confirmation of heat convective model Comparison of surface temperature time history between experimental data and prediction model. Surface temperature distribution of F45 model 1 second after model injection Temperature time history at stagnation and on the aeroshell. Both results are in good agreement --> the predicted model is appropriate.
Results of Aerodynamic Heating Heat flux distribution image Heat flux distribution in radial direction F45 model Higher at outer end F60 model Higher at inner end Flare angle have large influences on aerodynamic heating on the aeroshell. Large flare angle is more suitable to reentry vehicle
CONCLUSIONS It was demonstrated t d that t flare-type membrane aeroshell made of ZYLON textile have capability as a decelerator for atmospheric entry vehicle experimentally using hyper sonic wind tunnel Data about aerodynamic coefficient and aerodynamic heating of flare-type membrane aeroshell was obtained. Flare angle has large influence on the characteristics Large flare angle is suitable to atmospheric entry, in terms of decelerator performance and aerodynamic heating. Future works Design of the actual aerodynamic entry mission is progressed considering not only the results obtained in this study but also the other factors, for example, aerodynamic stability and structural strength of the aeroshell against the aerodynamic force.