The Falcon program addressed the implications of hypersonic flight and reusability by developing a series of hypersonic technology vehicles (HTVs) to incrementally demonstrate these required technologies in flight.
The Hypersonic Technology Vehicle 1 (HTV-1) is an unpowered, maneuverable, hypersonic reentry
vehicle integrated with state-of-the-art hypersonic technologies to address materials and fabrication
challenges. A set of HTV-1 ground tests were conducted to develop and validate the vehicle’s
aerodynamic, aero-thermal, and thermal-structural performance as well as to validate advanced carboncarbon
manufacturing approaches.
HTV-2 is a second generation design developed under Falcon that incorporates advanced aerodynamic
configuration and thermal protection systems, and improved guidance, navigation and control systems for
greatly improved performance compared with HTV-1. The HTV-2 detailed design has been completed
and an aeroshell prototype fabricated. Two HTV-2 flight tests will be conducted in 2009 launched from
Vandenberg Air Force Base using the Minotaur IV Lite launch system.
The Falcon program originally planned to develop a third Hypersonic Technology Vehicle (HTV-3) that
would focus on reusable materials. However early on in the execution of Phase II of Falcon, DARPA
elected to exercise an option to fund development and ground testing of propulsion technology necessary
to realize a reusable hypersonic testbed. This task, dubbed FaCET (Falcon Combined-cycle Engine
Technology), has the objective of developing a reusable, hydrocarbon fueled, Turbine-Based Combined
Cycle (TBCC) propulsion system capable of operating from a conventional runway up to speeds greater
than Mach 6. Propulsion advances in this effort coupled with the availability of the High Speed Turbine
Engine Demonstration (HiSTED) program high-Mach capable turbojet engine led to the decision to
evolve HTV-3 into a testbed that would take off from a conventional runway, cruise at Mach 6, and land
back on a runway. This new design was subsequently designated HTV-3X. HTV-3X is a highly
integrated testbed that will allow demonstration of key technologies such as efficient aerodynamic
shaping for high lift to drag, lightweight and durable (reusable) high-temperature materials, thermal
management techniques including active cooling, autonomous flight control, and turbine-based combined
cycle propulsion.