A technique for upwind differencing of the three-dimensional species continuity equations has been presented which permits computation of steady flows in chemical equilibrium and nonequilibrium. The iteration strategy has been demonstrated over a large range of pressures and temperatures. Easily programmed, empirical guidelines for controlling time step in the implicit formulation are also presented. isons with a free-energy-minimization routine serve to justify the equilibrium calculations. Nonequilibrium calculations for flow over spheres of varying radii demonstrate the prediction capabilities of the method over a large range of Damkohler numbers. Calculation of flowfields in near equilibrium present no problem for the method. of chemical species though there is no negative impact of diffusion terms (other than computer time) on the algorithm. Discussions of convergence rates, coupling strategies with the main equation set, and possibilities for improving convergence, reveal a challenging research area both from the point of view of physics and numerical analysis.
Compar-The method at present neglects diffusion 'ar'
V, free-stream w l o c l t y z A method for predlctlng t h e performance i~ viscous correlation paraneter, w&/K aerodynamlcs of aeroasslsted Orbltdl t r a n s f e r v d r l c l e s was developed based on technlgues that Space Shuttle o r b l t e r and theorles from the -, mro used I n the .erodynamlC ddtdbook Of the a angle of attack Hvnersonlc h r b l t r a r y Body R w r a m . The method Y rat10 O f SpGCif1C heats ,bans the e n t l r e f l i g h t broflie of the derOaSSisted Orbltdl t r a n s f e r Vehicles from t h e extreme high altltuck non-continwm re ine to the highly viscous continurn regime. Resufts from t h l s llethod me mnpared wlth f l l g h t data from t h e Shuttle orblter. Apollo Capsule. and the Vlklng Aeroshell. Flnally, performance aerodynamics are estimated for three aeroassisted o r b i t a l t r a n s f e r vehlcles t h a t range from low t o hlgh 1Ift-to-drag r a t i o conflguratlons. NOMENCLATUIE CA Chdpmdn-Rubesin vlacoslty coefficient CA a x l a l coefflclent, axlal f0rcelq.S Co drag cuefflcient, drag forceles CL lift coefflclent, l i f t force/eS w c, , normal coefflclent, normal f o r c e / e S S mference area. 4. Tw wall tanperature . . T, free-stream temperature T' reference tcrnperature *Aerospace Englneer, Space System Dlvlslon. Member AIM. *.Head, Vehlcle Analysts Branch, space Systems Dlvlslon. Meknber AIM. A mean free path u , free-stream vlscoslty a energy acconndatlon coefflclent Abbrevlatlons AOTV a e r m s s i s t e d o r b l t a l t r a n s f e r vehlclea FW free molecular flow HAB
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