The second phase of DARPA’s Glide Breaker program will seek to conquer the problem of operating a divert and attitude control system (DACS) on a kill vehicle traveling at hypersonic speed within the atmosphere, the agency says in a newly released solicitation. 

DARPA launched the Glide Breaker program in 2018 and awarded contracts to Aerojet Rocketdyne and Northrop Grumman to develop competing designs for “a critical enabling technology for hypersonic defense,” according to program documents. 

Last August, Aviation Week confirmed the key enabling technology for Glide Breaker is an advanced DACS for the Missile Defense Agency’s Glide Phase Interceptor (GPI) program. 

DACS are typically used to steer missiles or satellites outside the atmosphere where aerodynamic control surfaces are ineffective. A typical DACS is comprised of a ring of small rocket thrusters, which receive commands from a guidance and control system to fire as required to steer a missile into an incoming target or a satellite into a new position. 

Some missiles also use a DACS within the atmosphere, but such endoatmospheric intercepts are more dynamic at hypersonic speeds, when the complexity of a Mach 5-plus airflow interacts with the DACS jets. These highly complicated “jet interaction” (JI) effects must be understood, DAPRA says in a “program background and overview” document about Glide Breaker Phase 2 released on April 15. 

A notional schedule for Phase 2 calls for a company design and flight test of a demonstration system of a Glide Breaker DACS within four years, including a critical design review within 24 months, DARPA says. The design should be capable of integration in an operational system, such as GPI. 

The design of the demonstration system must be informed by wind tunnel testing, DARPA says. The agency has booked the Von Karman Gas Dynamics Facility Tunnel B at the Arnold Engineering Development Complex in Tennessee around March 2024. 

The last program to study JI effects of a DACS at hypersonic speed was the Advanced Interceptor Technology (AIT) program in the late 1990s, DARPA says. 

“AIT showed that JI effects are highly dependent on outer mold line geometry (including nosecone angle), jet placement, jet geometry, jet thrust, and chemistry effects resulting from unburned propellant reacting with the crossflow,” the agency says in the overview presentation. 

“If successful, the results of Phase 2 will provide the foundation for a future program of record interceptor,” the agency adds. The interceptor must be capable of launching from a Mk-41 Vertical Launch System on an Aegis ship, and hitting hypersonic missiles during the glide phase. Those requirements align with the GPI program. 

The competition between Aerojet and Northrop for the Glide Breaker contract also has industrial base implications. Aerojet is the only U.S.-based supplier for DACS in operational missiles, so the program offers an opportunity for the Defense Department to expand the industrial base.