The Defense Advanced Research Projects Agency (DARPA) on Monday started soliciting research proposals for high performance leading edges for hypersonic air platforms.

DARPA released a presolicitation notice for the Materials Architectures and Characterization for Hypersonics (MACH) program, which “seeks to demonstrate new thermal based design and material solutions for sharp, shape-stable leading edges for hypersonic vehicles.”

A 10-percent-scale model of an experimental hypersonic scramjet.

The agency characterized leading edges as “an essential design feature of hypersonic aircraft” because they would dramatically improve hypersonic vehicle range, velocity, maneuverability, especially when it can withstand high heat fluxes while remaining aerodynamically thin and sharp.

Hypersonics are missiles that can travel over five times the speed of sound.

DARPA’s MACH program aims to develop new leading edge solutions integrated cooling to enable vehicle performance “well beyond that allowed” by the current carbon-carbon (C-C) composite-based leading edge systems in use today.

MACH will be a four-year and two-phase effort. The notice said proposals should be structured as a 27-month base Phase I with a 21-month optional Phase II. Phase I awardees will develop representative leading edge components that culminates in a Government-sponsored ground test campaign at program month 24.

After a three-month evaluation period from months 25 to 27, selected performers may be awarded a Phase II award to further mature their phase I technologies. Phase II winners will have a 21-month performance period to scale up and validate performance through ground testing during months 39 to 45 and perform manufacturability studies to inform cost models developed by the performers under Phase I.

If funding and the opportunity are available, select Phase II winners “may be candidates for a potential flight test campaign at which point a separate cost proposal to accommodate the flight test(s) will be requested.,” DARPA said.

The agency explained C-C composites are the current thermo-structural material of choice because they can handle temperatures over 2,000 degrees Centigrade and extreme heat fluxes. However, C-C also needs protection from oxidation to prevent material erosion and a subsequent shape change, even at much lower temperatures and heat fluxes. These restrictions limit the geometry of an unprotected C-C leading edge to a relatively blunt radius curve.

An anti-oxidation coating can help sharp C-C composite leading edge geometries withstand high temperature and heat fluxes, but then you have to worry about the coating reliability during extended hypersonic flight time.

DARPA is interested in integrating cooling in leading edges to help and thinks new technological advanced can push development past the mostly limited lab-scale tests conducted so far.

“DARPA believes that the complexity and risk associated with adding cooling to thin leading edges can be dramatically reduced by leveraging recent advances in thermal management, net-shape manufacturing, and integrated system modeling,” the solicitation said.

The agency also said developing high performance cooling leading edges might be useful to enhance other sharp aerodynamics structures on a hypersonic vehicle that need to withstand the ultrahigh heat fluxes in hypersonic flight.

DARPA said MACH “will develop a new class of thermally-managed, shape-stable, sharp leading edge solutions for high lift-to-drag ratio hypersonic air vehicles that are capable of operating at high heat fluxes. These architected, thermally-managed non-eroding leading edges will enhance hypersonic operational capability, e.g. enable future platforms to fly faster and farther.”

The agency explained it will solicit research that looks into innovative approaches that allow “revolutionary advances is the materials design and implementation of shape-stable, high heat flux capable leading edge systems.”

The presolictation notes MACH will focus on both integrated leading edge thermal management solutions applicable broadly across U.S. hypersonic configurations like boost-glide and scramjet vehicles as well as more general next-generation materials research for hypersonic leading edges.

In addition to a two-phase contract program, MACH will be divided into two technical areas. Technical Area 1 (TA1) will focus on developing fully integrated thermal management systems for a scaled leading edge to apply to near-term hypersonic platforms.

Technical Area 2 (TA2) will focus on next-generation leading edge materials research that can facilitate leading edge capability “well beyond TA1 performance metrics” to include new thermal management techniques, metals, ceramics, coatings, and new computational capabilities needed to develop the new materials and techniques.

DARPA said TA2 is geared to “identify and mature enabling leading edge solutions that greatly transcend TA1 requirements and develop foundational technologies applicable to future hypersonic platforms.”

Proposers can submit one or both TAs, but must be written separately for TA1 and TA2. The notice said proposers can assume a target start date of Sept. 2019 for planning and budgeting purposes.

In March the director of DARPA, Steven Walker, told reporters the agency’s timeline for hypersonic weapons is on track to develop strike capabilities by 2020, ISR capabilities by 2025, and usable technologies by 2030 (Defense Daily, March 9, 2018).

More recently, in August Under Secretary of Defense for Research & Engineering Michael Griffin reiterated the department will be working “very hard to have some of our first offensive strike weapons in the inventory by the early 2020s” followed by having long-range conventional strike weapons to hold an enemy hostage from ranges beyond what they can threaten the U.S. with by the late 2020s (Defense Daily, Aug. 2, 2018).