N101-086 TITLE: Advanced Rail Materials for Electromagnetic Launchers

TECHNOLOGY AREAS: Materials/Processes, Weapons

ACQUISITION PROGRAM: ONR EM Railgun Innnovative Prototype

RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted." The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.

OBJECTIVE: Develop tough, erosion/high-temperature resistant metal alloys, metal composites, or advanced coatings to be used as electrically conducting rails in an electromagnetic (EM) launcher (electric railgun).

DESCRIPTION: The US Navy is pursuing the development of an electromagnetic launcher (also known as a rail gun) for long range naval surface fire support. An electromagnetic launcher consists of two parallel electrical conductors, called rails, and a moving element, called the armature. Current is passed down one rail, through the armature, and back through the other rail. The armature is accelerated down the barrel due to the interaction between this magnetic field and current flow (Lorentz Force). An electromagnetic rail gun (EMRG) system will accelerate projectiles to hypersonic speeds, enabling ranges beyond 200 NM in less than 6 minutes of flight time while traversing the atmospheric spectrum (endo-exo-endo). The EMRG can address time-critical targets with a rate-of-fire of 6 to 10 rounds per minute while residual energy at target impact provides lethal effects. This operation occurs in an environment consisting of strong magnetic fields, high temperatures, chemical interactions and strong lateral forces on the rails and armature in the launcher bore.

A pair of electrically conductive rails act to transfer the power supply current down their length and through the moving armature creating an accelerating Lorentz force. These rails also provide lateral guidance to the armature. The face of this rail material must be able to withstand the severe mechanical, electrical, and thermal environment present in the bore of a high power electromagnetic launcher. This surface must be able to survive sliding electrical contact of an aluminum armature and polymer bore rider materials at velocities up to 2.5 km/sec, and possibly concurrent balloting loads. In order to survive these conditions, the rail material must be electrically conductive to high currents approaching 6 MA, resistant to high transient temperatures, possess high hardness and yield strength and retain these properties after thermal transients, must accommodate balloting loads, and survive exposure to molten armature metals. The material is required to resist thermal breakdown and interaction in the presence of plasma due to high current electrical arcing and shocked gas. The material must eventually be manufacturable as well as affordable for these dimensions. Alternatively, potential protective layers may be considered such as bonded claddings, jackets, surface coatings or treatments. For purposes of managing electrical current distribution and mechanical stresses, approaches that permit grading of material properties such as electrical conductivity, thermal expansion coefficient, elastic modulus near the sliding surface would be particularly attractive.

PHASE I: Develop a rail material/coating and process approach to manufacture electrically conductive bore materials. Conduct any necessary subscale tests needed to show that the proposed process is suitable for Phase II demonstration. Create sample rail coupons for static or small scale testing and verification, such as strength, erosion resistance, and conductivity versus temperature from ambient to 500 degrees C.

PHASE II: Produce samples of electrically conductive rail materials of at least 1 m length that meet the needs of the EM launcher environment. Demonstrate that the material provides the required material property characteristics described above. Further develop and demonstrate the fabrication or joining processes for creating longer sections. Also demonstrate fabrication technology to create non-planar contact surfaces facing the bore. Produce a prototype set of coupons 1 m long and of full rail cross section, for testing in a small scale EM launcher. The EM launcher test facility may be provided as government furnished asset, or via a teaming relationship with other EM launcher test sites. Potential test sites include various scale railguns operated by Universities and Defense contractors. The results of testing may be classified. The Phase II product may become classified.

PHASE III: Develop process for full length (7-12 meters) rails with final design dimensions in other axes. The materials process developed by the Phase II effort will be applied to Navy railgun proof of concept demonstration and design efforts in the lab as well as industry advanced barrel contractors. Successful rail materials solutions will be installed in a weapon system on board ship upon transition to PEO IWS, PMS 405, ONR Program Office and integration with industry launcher manufacturers' production weapon systems that will be sent to the fleet.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The materials and processes developed could be applied to any electro-mechanical applications particularly under conditions of high heat, stress, and/or current requiring both the beneficial thermal and high current aspects of conducting metals combined with the need for higher toughness and hardness with traceability to relatively long sections. Example applications could be high-speed mag-lev contacts, electrical generation facilities, high current switches and sections for re-entry protection of space-craft.

REFERENCES:
1. Stefani, F.; Parker, J.V., "Experiments to measure gouging threshold velocity for various metals against copper," Magnetics, IEEE Transactions on , vol. 35, no.1, pp.312-316, Jan 1999.

2. Gee, R.M.; Persad, C., "The response of different copper alloys as rail contacts at the breech of an electromagnetic launcher," Magnetics, IEEE Transactions on , vol. 37, no.1, pp.263-268, Jan 2001.

3. Wolfe, T.; Spiegelberg, W.; Evangelist, M., "Exploratory metallurgical evaluation of worn rails from a 90 mm electromagnetic railgun," Magnetics, IEEE Transactions on , vol. 31, no.1, pp.770-775, Jan 1995.

4. Holland, M.M.; Eggers, P.D.; Guinto, S.; Stevenson, R.D.; Columbo, G., "Advanced railgun experimental test results and implications for the future," Magnetics, IEEE Transactions on , vol. 29, no.1, pp.419-424, Jan 1993.

5. Jackson, G.; Farris, L.; Tower, M., "Electromagnetic railgun extended-life bore material tests results," Magnetics, IEEE Transactions on , vol. 22, no.6, pp. 1542-1545, Nov 1986.

6. Newman Newman, D.C.; Bauer, D.P.; Wahrer, D.; Knoth, E., "A maintainable large bore, high performance railgun barrel," Magnetics, IEEE Transactions on , vol. 31, no.1, pp.344-347, Jan 1995.

7. Hurn, T.W.; D'Aoust, J.; Sevier, L.; Johnson, R.; Wesley, J., "Development of an advanced electromagnetic gun barrel," Magnetics, IEEE Transactions on , vol. 29, no.1, pp.837-842, Jan 1993.

KEYWORDS: railgun; rail; electromagnetic; conductor; wear; launcher

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