Numerical and Experimental Investigations of Epsilon Launch Vehicle Aerodynamics at Mach 1.5

Abstract

The Epsilon Launch Vehicle, successor of M-V rocket which conveyed "MUSES-C (Hayabusa)," is currently under the development in Japan. The Epsilon is also designed for sending scientific satellites to outer space and its first flight is scheduled to be in 2013. In this study, by conducting both numerical simulations and wind tunnel tests, the aerodynamic characteristics and associated flow features of the Epsilon Launch Vehicle are extensively investigated at Mach 1.5. The results provided are axial/normal/side forces, pitching/yawing/ rolling moments, detailed three-dimensional flow structure, along with effects of Reynolds number (between wind-tunnel and flight conditions), Skin Stringers (small devices on the main body), and difference from another configuration called "NextGenEpsilon." This set of data includes unavailable ones at either the experiment standalone or the actual flight. Magnitudes of computed aerodynamic coefficients are in good agreement with the experiment and within the design criteria. According to the results, axial force is not affected by those above-mentioned factors, but local normal force is influenced around Skin Stringers by Reynolds number, and rolling moment can change even its sign. Detailed M x = rolling moment, (y-y cg )f z -(z-z cg )f y ] [N·m] M y = pitching moment, (z-z cg )f x -(x-x cg )f z ] [N·m] M z = yawing moment, (x-x cg )f y -(y-y cg )f x ] [N·m] p = static pressure [Pa] Pr = Prandtl number, 0.72 [-] q = dynamic pressure [Pa] Re = Reynolds number [-] S = reference area, πD 2 /4 [m 2 ] T = temperature [K] u, v, w = velocity components in Cartesian coordinates [m/s] x, y, z = Cartesian coordinates [m] x cg , y cg , z cg = center of gravity coordinates, (0.6363L, 0, 0) [m] x n , y n , z n = normal vector components in Cartesian coordinates [-]  = angle of attack [deg.]  = slip angle [deg.]  = roll angle [deg.]  = specific heat ratio, 1.4 [-]  = thermal conductivity [W/(m·K)]  = (molecular) viscosity [Pa·s]  = density [kg/m 3 ] Subscripts FL = flight condition F = forebody t = turbulent WT = wind-tunnel test condition ∞ = freestream value 0 = initial or stagnation value American Institute of Aeronautics and Astronautics 4

Experimental and Numerical Investigations of Slender Body Side Force with Asymmetric Protuberances

“…The protuberance mimics the attitude control device [5] that is typically installed on rockets, as shown in Fig. 1b.…”

“…Generally, it is rare for slender bodies to generate asymmetric vortices resulting in side forces at low angles of attack (0° ≤ α ≤ 15°) without protuberances [3,4]. However, if a protuberance is attached to a slender body surface, it generates an asymmetric vortex, even at a low angle-of-attack (0° ≤ α ≤ 15°), and various problems are associated with asymmetric vortex influence [5]. For example, more than 30 protuberances would have been installed on the Ares I rocket, of which six types of protuberances would have been arranged asymmetrically, thereby forming an asymmetric flow field and side force [6].…”

“…Side forces have been observed not only as a result of axial asymmetric protuberances on the surface of slender-bodied objects, but of high angles of attack [9][10]. Therefore, in many development projects, aerodynamic loads induced by protuberances have been examined, such as the Epsilon Launch Vehicle in Japan, and Ares I and Ares V rockets in the United States [5][6][11][12]. However, these studies are considered to be limited in terms of the design of protuberance arrangement.…”

“…Additionally, corresponding experiments were not conducted. As mentioned above, the authors of [5][6][7][8][9][10][11][12][13] only presented aerodynamic characteristics from either wind tunnel experiments or numerical calculations independently, or focused on a specific configuration.…”

“…Mach 1.5 was selected because this is the speed at which a rocket is expected to experience its highest dynamic load (i.e., maximum dynamic pressure, q) [5]. This is considered to be one of the most important Mach numbers during flight for many rockets.…”