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Armature-rail Electrical Interface in Electromagnetic Launch 3 Nov 2010

Armature-rail Electrical Interface in Electromagnetic Launch 3 Nov 2010. Capt Peter Hsieh Reserve Program Manager Air Force Office of Scientific Research. DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Overview. Electromagnetic launch applications

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Armature-rail Electrical Interface in Electromagnetic Launch 3 Nov 2010

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  1. Armature-rail Electrical Interface in Electromagnetic Launch3 Nov 2010 Capt Peter Hsieh Reserve Program Manager Air Force Office of Scientific Research DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

  2. Overview • Electromagnetic launch applications • Railgun physics and engineering • Armature-rail sliding contact • Plasma transition • Hypervelocity gouging • Metallurgical reactions • Summary I. Newton, A Treatise of the System of the World, ca. 1680 3 Nov 10

  3. Electromagnetic launch applications 108 Space launch 107 Aircraft catapult 106 Naval railgun 105 O. Božić and P. Giese (2006) Antitank railgun 104 Kinetic energy (kJ) 103 102 101 Hypervelocity space debris NASA Ames Research Center (2008) 100 0 5 10 15 Velocity (km/s)

  4. Electromagnetic railgun physics K.A. Schroder et al., IEEE Trans. Magn. 35(1): 95 (1999) C. Meinel, IEEE Spectrum (2007) 40-46

  5. Railgun engineering issues • Pulsed power • Energy storage • Pulse shaping network • Launcher • Armature and rail • Insulators • Payload Electromagnetic Launch Facility (EMLF) NSWC Dahlgren Division

  6. Armature-rail sliding contact • Electrical contact • Current distribution • Sliding contact • Hypervelocity gouging • Material properties • Buried interface • Metallurgical reactions P. G. Slade, Electrical contacts: principles and applications (1999) M. Ghassemi and R. Pasandeh, IEEE Trans. Mag.39, 1819 (2003) R.A. Meger, et. al., IEEE Trans. Mag. 41, 211 (2005).

  7. Energy balance at the interface Armature Air compression Metallurgical reactions Joule heating Friction ≈ 10 μm Electrical current Conduction Rail

  8. Transition to plasma contact R. A. Marshall et al.IEEE Trans. Mag.31(1): 214-218 (1995)

  9. Hypervelocity gouging • Phenomenon first reported by AF scientists working with rocket sleds (1969) • Characteristic tear-drop gouges in rails due to asperity impact • High-speed asperity impact Rocket sled testing at Holloman AFB K. F. Graff and B. B. Dettloff, Wear (1969), 87-97

  10. Gouging and shock loading K.R. Tarcza and W.F. Weldon, Wear, 209: 21-30 (1997) F. Stefani and J.V. Parker, IEEE Trans. Mag., 35(1): 312-316 (1999)

  11. Hydrocode simulation of gouging • Analysis of experimental data with CTH hydrocode modeling to extract high-strain rate material parameters • Validation of CTH model by comparing predicted temperature with alloy microstructure changes J.D. Cinnamon and A. N. Palazotto, Int. J. Impact. Engr. (2009), 254-262

  12. Interfacial metallurgical reactions C. Persad, IEEE Trans. Mag.43(1): 391-395 (2007) ASM Handbook (volume 3): Alloy Phase Diagrams

  13. Unraveling the problem • De-couple sliding velocity from electrical current density • Improve multi-physics modeling of the boundary film on relevant timescale with respect to its electrical and thermal transport mechanisms • Model and test nonreactive armature-rail material pairs

  14. Summary • Electromagnetic launch is a breakthrough technology for hypervelocity research • The armature-rail interface in railguns experiences conditions far from equilibrium during launch and gives rise to rail wear • Further basic research to understand energy transport across the armature-rail contact is crucial for materials engineering

  15. I.R. McNab, IEEE Trans. Mag.45(1): 381-388 (2009) Capt Peter Hsieh Air Force Office of Scientific Research peter.hsieh@afosr.af.mil Questions? Artist’s concept of NASA lunar base with mass-driver for mined ores.

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