The Application of Implosion Wave Dynamics to a Hypervelocity Launcher

Flagg, Robert F.

doi:10.21236/ad0654273

Cited by 6 publications

(2 citation statements)

References 5 publications

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“…Studies done in at the University of Toronto Institute for Aerospace Studies (UTIAS) in the 1960s showed that only sensitive primary explosives, for example, lead azide, and powdered PETN can be initiated by gas-phase detonation. 108,109 Later studies by Grigor'ev et al 110 using overdriven gaseous detonation waves to initiate porous PETN measured a critical pressure of the gas shock required to initiate the explosive to be in the range of 20-65 MPa, which agrees well with earlier estimates for PETN from the UTIAS studies. This pressure is approximately an order of magnitude lower than the pressure required to initiate porous PETN with a shock wave from another condensed-phase source, that is, a donor charge of a different explosive, suggesting that shock waves in gases may be more efficient at initiating detonation.…”

Section: Initiation Of Explosives By Shock Waves In Gasessupporting

confidence: 64%

Ram Accelerators: Outstanding Issues and New Directions

Higgins

2006

Journal of Propulsion and Power

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An assessment of the key issues affecting the thrust and maximum velocities that can be obtained in ram accelerators is presented. The regimes of ram accelerator operation (subdetonative and superdetonative) are discussed, and simple models for thrust are compared to experimental results and found to be satisfactory. The phenomena that are responsible for the operating limits of these modes of operation are explored, and potential solutions for overcoming these limits are discussed. In particular, the possibility that flow separation may cause unstarts in both the subdetonative and superdetonative ram accelerator is shown to explain qualitatively the experimentally observed limits. A potential remedy to the unstart problem that involves modifying the geometry of the ram accelerator tube is presented. The role of the projectile material, which may react with the oxidizing environment of the propellant, also has a significant effect on superdetonative operation. Techniques to address this problem are outlined. Other novel concepts, such as the use of an explosive-lined launch tube and the laser-driven ram accelerator, are discussed as well. Nomenclature A= area A R = area ratio (tube area to throat area)= Mach angle q = heat release ρ = density τ = viscous shear stress χ = inert gas dilution Subscripts s = flow condition at boundary-layer separation point 1 = flow conditions approaching projectile 2 = flow conditions at projectile throat 6 = flow condition exiting projectile control volume in thermally choked mode

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Section: Initiation Of Explosives By Shock Waves In Gasessupporting

confidence: 64%

Ram Accelerators: Outstanding Issues and New Directions

Higgins

2006

Journal of Propulsion and Power

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“…Plagg (Ref. 10) has shown that the isentropic exponent of the gas scarcely changes during the implosion and reflection stages Cy . 1.14) after investigating the numerical results of Brode (Ref.…”

Section: S Comparison Op Experimental Results and Theorymentioning

confidence: 99%

Temperature measurements at an implosion focus

Saito

Kudian

Glass

1982

Proc. R. Soc. Lond. A

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Sectroscopic temperature measurements were made at the focal point of imploding shock waves in the UTIAS implosion C chamber, which has a 20-cm diameter hemispherical cavity.The chamber was filled with a stoichiometric H2-02 gas mixSture at different initial pressures (14 " 68 atm).The mixture was ignited at the origin by an exploding wire generating an outgoing detonation wave which reflected at the chamber wall as an imploding shock wave (gas-runs).Additional experiments where an explosive shell of PETN was placed at the hemispheriual wall were also conducted The shell was detonated by the impact of the reflected gaseous detonation wave at its surface, thereby generating an intense implosion wave (explosive-run).The temperatures were measured at the implosion focus using a medium quartz Hilger spectrograph with an eight photocell polychromator attachment over the visible wavelength range. The meas'ured radiation intensity distributions were fitted to blackbody curves. The temperatures were 10,000 1-13,000 K for gas runs, and 15,000 v 17,000 K for explosive runs.The cont.nuous spectra from photographic film and the measured emissivities, which were very close to unity, confirmed that the plasma was a blackbody.Numerical studies using the random choice method (RCM) and classical strong-shock theory wore used to analyse the flows in the entire range of the implosion process.Real-gas effects and radiation losses were also considered. The results were compared with the experimental data and good agreement was obtained.

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