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Modeling and experiments are being done with the goal of understanding the physics of projectile acceleration at high driving pressures (megabar range) and short acceleration times (a few microseconds) well enough to design and test successful hypervelocity launch systems, The Fast Shock Tube, a cylindrically convergent high-explosive driver, has been used to accelerate projectiles.Detailed modeling of the experiments, including high-pressure gas flow, projectile instability, and projectile fracture, has been done with MESIV2D. Modeling results show quantitative agreement with the average behavior of the system. However, details of projectile behavior are not predicted well. Observed velocity distributions across the diameter of a projectile or projectile shapes are only in qualitative agreement with calculations. This, then, presents the major constraint on the successful design of a launch system: that the processes that limit projectile integrity depend on the details of the drive conditions, and these details are not quantitatively modeled at this time.

Thlr rqnm wm prep ed m tin mxmurrt wf wrx~Iprrnmrral hy q n a~ncy of Ilw [Mod SImW (Jovernmenl, Ncllhcr the I Inikl SIMeB (Jrrvarnrrwnl nor qny ngency thared, nor nny of IIwir employeet. makern~ny wnrmn!y, c~prowuor impliai, or amumea wry Iegd Iiahilil y m reepnrdhdhy (or [he •~twratyl u)mplalenwu, or IMulrrms of any mformwinn, tppermus. prduct, or prrww diw!kmd, or reprc-nls Ihal ilo UK would nol infrin~e privnlely nwnd righlm Refer. cnce hcrem III wry rn~illu conrmercml prtdurt, prmxm, or Mrviw hy trnrkj name, Iredmrrai.k, mmruklurer, wr otherwise dtrna nut nwcensmly conn[iiule or imply itrncndwreement, rearer. mendamm, or favrwurs hy Ihe ( Inkl Strom (itwermrreni or rnny egency Iherewf, The viewg mrd qrimonn of muhwm cqrremed herein dn rml nwaeardy~iule or reflwct Ikw wf Ihe I hriled Slmlos (krvernmnl or uny qgency Iherwof LOSNl~llililOS LosAlamos,NewMexico8754gTeats have been done to diagnose various aspacfs of the behavior of the shocked foam In the core of the fast shock tube, Calculations and lest results of shock behavior In the foam are In good agreement. However, calculations with different foam equations of state differ in some details. Precursor shocks at the foam/HE interface were obsewed in some tests; a modified assembty procedure eliminated this problem. Calculations of shape and veloclty of plates In direct contact with the foam are in relatively good agreement. Expansion of shcked foam down q barrel Is mrnplicated by perturbations from the barrel Inlet and from deformed regions of the banel! In one test, a 2.Wm diameter by 2-mm thick stainless steel plnte was accelerated to 0.78 CWWSand remained planar for a 55-cm run throuoh air.

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