Validation of a Simulation Model for a Planetary Entry Capsule

Abstract

Subsonic static and oscillatory aerodynamic coef cients were measured at Politecnico di Torino for a planetary entry capsule model. The experimental data set was included in a mathematical model of payload-decelerator system, and the results of simulations were compared with ight-test data. The frequency-domain attitude response of the capsule was reproduced during the main parachutes' deployment, and discrepancies for the drogue opening phase were observed. The impact on simulations of atmospheric turbulence and asymmetries in the parachute suspension system was also considered. The results suggest that several factors may affect the delity of simulations such as correct modeling of suspension system geometry and exibility, parachute aerodynamics, accuracy of payload inertial data, and accurate matching of real ight external perturbations. The effect of some design parameters on capsule attitude dynamics was evaluated. The arti cial increase of capsule damping coef cients produced observable effects on attitude time histories for large perturbations of the aerodynamic derivatives only. The dynamic stability of the system is reduced for large increase of riser length and parachute added mass. Nomenclaturereference length (capsule diameter) F = elastic force I ay = added moment of inertia of the parachute I x ; I y ; I z ; I x z = mass moments of inertia K = elastic constant L = rolling moment L b = additional rolling moment due to bridles l = length M = pitching moment m = mass m ax ; m ay = axial and transverse added masses of the parachute N = yawing moment N b = additional yawing moment due to bridles p; q; r = angular rates (capsule) q 1 = dynamic pressure, ½V 2 =2 Re = Reynolds number, based on capsule diameter d S = reference area, ¼ d 2 =4 S P = parachute reference area s; y; h = Earth-xed axes [T BV ] = rotation matrix from s; y; h to x B ; y B ; z B ; f .Á; µ; Ã ) [T P V ] = rotation matrix from s; y; h to x P ; y P ; z P ; f .Á P ; µ P ; Ã P ) degli Abruzzi 24; quagliotti@polito.it.Senior Member AIAA.auxiliary body-xed longitudinal axes (origin at capsule theoretical apex) x B ; y B ; z B = body-xed axes (origin at capsule c.g.) x P ; y P ; z P = body-xed axes (origin at parachute c.g.) Y = lateral force Z = normal force ®;¯= angle of attack and sideslip (capsule) 1l = length increment ² = strain, 1l=l ¾ = total angle of attack (capsule) N ¾ = measurement accuracy of wind-tunnel data ¿; Â = angular displacement of the riser with respect to s; y; h (see Fig. 1) Á; µ ; Ã = Euler angles Á a = aerodynamic roll angle (capsule) Subscripts b = bridle CG = center of gravity (capsule) CP = center of gravity (parachute) g = gust P = parachute PA = parachute attach point P2 = point of con uence of riser and suspension lines r = riser s = suspension line 0 = reference condition 1, 2, 3 = vector components

Stochastic Flight Simulation Applied to a Sounding Rocket

“…When a parachute reaches its steady form, it applies additional loads on the payload. In the most complete form, trapped air effects should be considered in equations [17][18][19][20]. However if the parachute, which is used, is small enough to neglect the effect of trapped air, then it is possible to model the parachute by a simplified force and assume that this force is applied to the end of the payload and induce a drag force which causes a moment by the distance between center of mass and payload end section with reasonable accuracy.…”

An algorithm for modelling the interaction of a flexible rod with a two-dimensional high-speed flow

“…Current and future interplanetary exploration missions demand the availability of numerical tools for the design of light structures such as Gossamer spacecraft and parachutes [1][2][3]. In many situations of interest, an adequate description of the continuum fields in both the fluid flow and the solid structure dynamic deformations, as well as of their coupled interactions, is 1059 restriction is imposed by the assumption that the fluid domain has a well-defined interior and exterior, which is the basis of the coupling algorithm based on level sets.…”

“…In this work, we extend this approach to the case of thin structures that at the same time are open and in which the flow on both sides of the structure may be relevant. These situations arise in important applications such as the deployment of parachutes used as deceleration devices during planet entry in space exploration missions [1][2][3]. The extended approach retains the basic concepts of the original algorithm, but allows an unbiased consideration of the flow conditions on both sides of the immersed structure as well as an adequate treatment of the boundary conditions on both sides of the boundary.…”

Parachute-Payload System Flight Dynamics and Trajectory Simulation

“…The implications of this decoupling are that there are no aerodynamic roll moments (L = 0), no sideslip effects in the longitudinal plane, and finally no angle of attack effects in the lateral plane. It should also be noted that, since the body is axissymmetric, total angle of attack would need to be considered for aerodynamic coefficients interpolation, as implemented in [23].…”

“…A second simulation model (designated as SM2) was defined, implemented, and validated in [23]. The major differences with respect to the less complex SM1 model are (i) the aerodynamics of the bodies are defined in terms of total angle of attack due to the geometrical symmetry of payload and parachute;…”