X-41 Common Aero Vehicle (CAV)
Hypersonic Technology Vehicle (HTV)

The Prompt Global Strike (PGS) Mission Needs Statement (MNS) established the requirement for rapid conventional strike worldwide to counter the proliferation of weapons of mass destruction and provide a forward presence without forward deployment. In December 2002 the DepSecDef directed the Air Force and Defense Advanced Research Projects Agency (DARPA) to establish a joint program office to accelerate the Common Aero Vehicle (CAV) effort to meet this requirement. This joint program has been named Falcon and was focused on the development and transition of more mature technologies into a future weapon system capable of delivering and deploying conventional payloads worldwide through space.

Initiated in 2003, the joint Air Force and Defense Advanced Research Projects Agency endeavor consists of two distinct objectives: to develop hypersonic technology for a glided or powered system and advance small, low cost, and responsive launch vehicles. Other partners participating in the demonstration program include the National Aeronautics and Space Administration, Space and Missile Systems Center, Sandia National Laboratories and the Air Force Research Laboratory's Air Vehicles and Space Vehicles Directorates. Both AFRL organizations have been working on the project's hypersonic technology vehicle portion, with Space Vehicles, located at Kirtland Air Force Base, N.M., specifically focusing on technologies for the glided system.

The Falcon program consists of two tasks. Task 1, the Small Launch Vehicle (SLV), has a primary objective of developing a launch vehicle capable of placing a 1,000 pound satellite into a 100 nautical mile, due east orbit when launched from Cape Canaveral Air Force Base. Task 2, the Hypersonic Technology Vehicle (HTV), will develop and flight test a number of key enabling technologies for hypersonic flight. The goal is a reusable hypersonic cruise vehicle (HCV) capable of global reach at a cruise speed approaching Mach 10.

As part of the Falcon program, a series of demonstration vehicles, referred to as HTV-1, HTV-2, and HTV-3, were developed. These vehicles will demonstrate the technologies required for the HCV. HTV-1 and HTV-2 are flight test-beds to demonstrate enabling technologies for future hypersonic reentry operational systems. HTV-3 was to be a flight test-bed to demonstrate enabling technologies for a future hypersonic cruise vehicle.

Though the HTV-1 was assumed to utilize state-of-the-art materials, both the HTV-2 and HTV-3 would requirematerials development to meet their requirements for thermal loading. DARPA established a Materials Integrated Product Team (MIPT) to work with Lockheed Martin on Task 2 in the development of materials for HTV-2, HTV-3, and HCV. The focus of the MIPT is on materials development for TPS and hot structures. Materials for propulsion components and for cryogenic tanks were not considered by the MIPT. The immediate goal of the MIPT efforts was use on HTV-2 and/or HTV-3.

The long use time at high temperatures for the HTV-2, and the added requirement of multiple cycles for the HCV, led the MIPT to select five technical areas for materials development. These five technology areas were identified as ones that are critical for achieving HCV operational objectives and in need of maturation to lower the Falcon program risk. The five areas are: 1) leading edges at use temperatures of less than 3000°F, 2) fiber reinforced composites with a use temperature of greater than 3000°F, 3) high temperature multi-layer insulation, 4) acreage thermal protection systems, and 5) high-temperature seals. This work has been funded by DARPA.

The goal of the joint program is to develop and validate in-flight technologies that enable both a near-term (2010) and far-term (2025) capability to execute time-critical, prompt global-reach missions, while at the same time demonstrating affordable and responsive space lift.