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**115**

**Chapter 6**

**Abstract**

*Rakhab C. Mehta*

zero angle of incidence.

**1. Introduction**

reentry vehicle, shock wave

Numerical Simulation of Base

Reentry Capsules at High Speed

The numerical simulations over several reentry vehicles are carried out by solving time-dependent compressible laminar axisymmetric Navier-Stokes equations for Mach 1.2–6.0. The fluid dynamics equations are discretized in spatial coordinates using integral formulation in conjunction with a finite volume method which reduce to semi-discretized ordinary differential equations. A local time-step is used to achieve steady-state solution. The numerical computation is carried out on a single-block structured computational grid. The flowfield features over the reentry vehicle such as formation of a bow shock wave ahead of the fore-body, expansion fan on the shoulder, and recirculation zone in the base region are well captured in the numerical simulations. Lower pressure acting on the base of the reentry capsule acts as base drag. The base drag coefficient based on maximum cross-section of the reentry capsule must satisfy inequality. The base drag coefficient is a function of several geometrical parameters of the fore-body and back-shell of reentry capsule, boundary layer, formation of free-shear layer in the wake region and freestream Mach number. The purpose of this chapter is to numerically evaluate and tabulate the base pressure and the base drag coefficients of various reentry space capsules at

**Keywords:** aerodynamic, base drag, CFD, high speed flow, viscous flow,

A space vehicle may be designed with several trajectory options such as nonlifting (steep or shallow), lifting (skipping or diving), terminal (gravity assist), thrusting (jet-on) reentry. The base pressure and heat flux are of paramount importance for smooth deployment of parachute and successful landing of a spacecraft. Cassanto [1] has carried out a number of wind tunnel and free-flight experiments to obtain the base pressure. Lamb et al. [2] have reviewed the base pressure on the reentry vehicle at high speed, which depends on wake flow characteristic, freestream conditions and edge properties of boundary layer at the shoulder of the module. The base pressure correlation for supersonic flows are compared by Kawecki [3] using the ground test data and with different vehicles such as ABC, MK-3, 4, 12, MTV, reentry F, REX, RVTO, SAMAST, TVX and WAC. A supersonic analysis of the SPR INT blunted cone-flare is carried out by Terry and Barber [4] employing computational fluid dynamics (CFD) method as well as wind-tunnel

Pressure and Drag of Space
