capt peter hsieh reserve program manager air force office of scientific research armature-rail...
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Capt Peter HsiehReserve Program Manager
Air Force Office of Scientific Research
Armature-rail Electrical Interface in Electromagnetic Launch
3 Nov 2010
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
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Overview
• Electromagnetic launch applications• Railgun physics and engineering• Armature-rail sliding contact– Plasma transition– Hypervelocity gouging– Metallurgical reactions
• Summary
3 Nov 10
I. Newton, A Treatise of the System of the World, ca. 1680
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Electromagnetic launch applications
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0 5 10 15Velocity (km/s)
Kine
tic e
nerg
y (k
J)
Aircraft catapult
Naval railgun
Antitank railgun
Hypervelocity space debris
Space launch
O. Božić and P. Giese (2006)
NASA Ames Research Center (2008)
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Electromagnetic railgun physics
BLIF
C. Meinel, IEEE Spectrum (2007) 40-46
K.A. Schroder et al., IEEE Trans. Magn. 35(1): 95 (1999)
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Railgun engineering issues
• Pulsed power– Energy storage– Pulse shaping network
• Launcher– Armature and rail– Insulators
• PayloadElectromagnetic Launch Facility (EMLF)NSWC Dahlgren Division
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Armature-rail sliding contact
• Electrical contact– Current distribution
• Sliding contact• Hypervelocity gouging– Material properties
• Buried interface• Metallurgical reactions
R.A. Meger, et. al., IEEE Trans. Mag. 41, 211 (2005).
P. G. Slade, Electrical contacts: principles and applications (1999)
M. Ghassemi and R. Pasandeh, IEEE Trans. Mag. 39, 1819 (2003)
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Energy balance at the interface
Electrical current
Friction Joule heating
Air compression
Metallurgical reactions
Conduction
≈ 10 μm
Armature
Rail
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Transition to plasma contact
R. A. Marshall et al. IEEE Trans. Mag. 31(1): 214-218 (1995)
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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 impactK. F. Graff and B. B. Dettloff, Wear (1969), 87-97
Rocket sled testing at Holloman AFB
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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)
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Hydrocode simulation of gouging
J.D. Cinnamon and A. N. Palazotto, Int. J. Impact. Engr. (2009), 254-262
• 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
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Interfacial metallurgical reactions
C. Persad, IEEE Trans. Mag. 43(1): 391-395 (2007) ASM Handbook (volume 3): Alloy Phase Diagrams
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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
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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
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QUESTIONS?
Capt Peter HsiehAir Force Office of Scientific [email protected]
Artist’s concept of NASA lunar base with mass-driver for mined ores.
I.R. McNab, IEEE Trans. Mag. 45(1): 381-388 (2009)