N131-071 TITLE: Dense Core Ablative Nosetip Materials for Hypersonic Applications

TECHNOLOGY AREAS: Air Platform, Materials/Processes, Weapons

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 and demonstrate high-density nosetip materials for advanced hypersonic projectile applications.

DESCRIPTION: The Navy is developing high-speed weapon systems for long-range surface fire support, missile intercept, and conventional prompt global strike applications. Hypersonic sea-level launch presents an extreme aerothermal environment with high heat flux, high thermal shock, and oxidizing conditions at temperatures >2500C. Current hypersonic nosetip materials are typically low-density ablators such as graphite, carbon-carbon (C/C), or Polymer Matrix Composites (PMCs) for re-entry vehicle and ballistic missile applications. For future Navy systems, a high-density nose tip will be needed to enable stable flight behavior of hypersonic sea-level projectiles. The nosetip will require a small nose radius to minimize drag, be of sufficient density in order to balance the center of gravity, handle extreme heat loads in highly oxidizing conditions, survive >30kG axial mechanical loads, >10kG transverse balloting loads, and thermal shock from surface temperature rise of 2000C/sec. However, it is believed that no single component material can meet the severe thermostructural and thermochemical design requirements of extremely high heat fluxes during the first seconds of flight, followed by longer flight at lower heat flux. With peak stagnation point heat fluxes on the order of 4500 BTU/ft2-s for a Mach 8 launch velocity(1) and densities over 15 g/cc, new materials solutions are sought, with multicomponent or functionally graded approaches likely necessary to minimize stress and handle oxidation issues. With a focus on high lift-to-drag ratio (L/D), hypersonic projectile testing in relevant environments will be necessary as the program progresses (as well as potential use in leading edge and rocket nozzle, combustor liner, and Thrust Vector Control applications)(2).

PHASE I: Assess legacy processing technologies and develop novel materials concepts for producing advanced nosetip materials. As the approach is developed, feasibility will be shown through proof of concept demonstrations. These demonstrations shall include quasistatic testing of materials systems with a focus on bonding/grading issues, as well as potential attachment solutions.

PHASE II: Optimize and scale up the materials approach formulated in Phase I. Prototype fabrication shall demonstrate the approach by producing relevant shape subscale parts, and then compare key performance data obtained from legacy and improved materials systems in severe thermal testing, such as arc-jet tests. There are potential ITAR and classification restrictions for technology when putting together materials concepts into relevant shaped subcomponent tests.

PHASE III: Apply the knowledge gained in Phase II to complete validation and certification testing. Develop a commercially viable process culminating in a prototype nosetip that can be integrated into a launch package or platform of interest. Then, conduct full-scale testing in relevant flight environments or other propulsion or extreme environment applications that has early ramp to transition. There are potential ITAR and classification restrictions for technology when putting together materials concepts into relevant shaped subcomponent tests.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Future military high speed and hypersonic propulsion components have a great potential to transition to the civilian rocket and related aeroengine applications such as low cost access to space. The materials resulting from these studies also have the potential for significant cost savings if they outperform existing state of the art materials systems. Further, these new materials may utilize revised fabrication methods which allow advanced component designs.

REFERENCES:
1. "Equations, Tables, and Charts for Compressible Flow", Report NACA 1135, Ames Research Staff, 1953.

2. Van Wie, D., D.G. Drewry, D.E. King and C.M. Hudson.2004. "The Hypersonic Environment: Required Operating Conditions and Design Challenges." Journal of Materials Science, 39 (19) p. 5915-5924. DOI: 10.1023/B:JMSC.0000041688.68135.8b

KEYWORDS: Nosetips; leading edges; ablatives; projectiles; high heat flux; high temperature materials

** TOPIC AUTHOR (TPOC) **

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