PDC/BNNT composites are the solution to otherwise intractable challenges to hypersonic flight. Hypersonic flight requires significant innovation to radar domes (radomes) of vehicle nosecones to maintain essential RF communications and sensing amid the compressed engagement timelines and severe aerodynamic heating with thermal shocks that such speed brings. Known ceramics and fiber reinforcement techniques do not allow the required combination of RF transparency, strength, or high-temperature endurance, nor allow tailoring compatible layers. Boron nitride is a known high-temperature dielectric, but not previously in a structurally useful form. Previously-known nanotubes and fiber reinforcements, while having high strength, do not meet the combined requirements of high-temperature strength, controllable thermal conductivity, low dielectric constant, and low loss tangent for reliably-performing RF transparent radome structures. ? PDC/BNNT (boron nitride nanotube-enhanced polymer-derived ceramic matrix composites) facilitate insertion of these high-temperature nano-reinforcements first into a polymer, then pyrolyzing it into the desired ceramic with controlled, tailorable characteristics. Not only do they improve thermo-structural capability and not compromise electrical performance, they improve both. Earliest PDC/BNNT composites already demonstrate over ten times the flexural strength of legacy materials (such as Pyroceram 9606), and excellent RF transparency with dielectric constant (relative permittivity) as low as 1.5 and dielectric loss tangent smaller than 0.025. These PDC/BNNT composites will be used to develop architecture concepts, then prototypes, for a new common radome architecture to enable multiple future advanced missiles to fly longer and faster (supersonic and hypersonic) through all weather. Optimization of ceramics explored so far is expected to improve strength above 1,500 C, and potentially to 2,100 C for newer matrix systems.
Benefit: Research and development into strong, lightweight, high-temperature composites for radar domes (radomes) is a critical limiting factor for control of emerging hypersonic vehicles required for national security between modern powers. Capabilities are currently driven by advancements in composite materials, of which nano-reinforced PDCs offer the most versatile promise, without other markets so immediately driving innovation. Defense innovation in these composite advancements, in turn, will cascade to dual-track such high-temperature materials advances to NASA, then commercial space, for vehicle entry, descent, and landing (EDL), and to supersonic commercial flight programs currently in work by commercial aerospace companies as yet without these R&D capabilities.
Keywords: Radome, Radome, RF Trans, boron nitride nanotube, thermal shock, Advanced Missile, BNNT, hypersonic, Dielectric
