While major tests are often remembered as a defining moment for a new military hardware platform, often forgotten or simply overlooked are the efforts that went into making such tests possible. Beyond every trial launch or platform analysis, there are those who quietly serve behind the scenes and work to ensure that the tests go as planned. One such unit is the United States Air Force’s 846th Test Squadron (846 TS) at Holloman Air Force Base (AFB), New Mexico.
Members of the squadron, which is part of the 704th Test Group of the Arnold Engineering Development Complex, have been conducting a series of preparatory rocket sled tests that began last year at the Holloman High Speed Test Track (HHSTT)—one of the world’s longest such facilities at 51,000 feet or about ten miles. The track utilizes a special sled that can be launched at speeds in excess of 9,000 feet per second or roughly Mach 8.6. It serves as a critical link between laboratory-type investigations and full-scale flight tests by simulating selected portions of the flight environment under accurately programmed instrumented conditions.
The sleds, which serve as the rest vehicles, are accelerated to mission velocities by means of solid rocket motors, frequently in multi-stage operations.
The mission of the HHSTT is to provide a cost-effective yet realistic and dynamic test environment for the Department of Defense (DoD) and various defense contractors.
846 TS has been engaged in the necessary work to get the hypersonic sled testing program up to speed at the HHSTT. These tests are part of the Hypersonic Readiness (HSR) program, which entered the planning stages four years ago while the first sled test was conducted just this past summer. This initiative is an in-house project that has prepared 846 TS to carry out the Hypersonic Test and Evaluation Investment Portfolio (HyTIP), Air-Launched Rapid Response Weapon (ARRW) as well as other anticipated recovered hypersonic sled tests.
The HSR program currently consists of multiple dynamic sled test velocities, sled designs, environments and different braking media.
“Due to current DoD priorities, it is expected that the frequency and complexity of hypersonic testing will increase over the next 10 years at HHSTT,” explained Lee Powell, capability development lead, who added that sled testing in support of HyTIP is planned for 2021.
This will include weather effects testing, including a simulated rain encounter; while testing in support of the ARRW is then expected to get under
Testing Makes Perfect
For tests to go as planned next year the 846 TS is required to revive, develop and of course rehearse hypersonic monorail sled test capabilities. The HSR program has been primarily focused on the hypersonic nine-inch monorail sled test capability, which includes the revival of old, as well as the development of new, high-speed braking capabilities.
“Historical hypersonic sled braking techniques have been retired and current braking methods do not allow entry at the speeds required to recover hypersonic monorail sleds,” Powell added.
Rain to the Desert
One of the recent tests called for the sled to be exposed to a 400-foot section of the newly upgraded 6,000-foot HHSTT “rainfield,” where a sprinkler head system simulated a rain squall.
“The basic concept was to demonstrate exposure of a developmental material to a ‘rain environment’ in order to test the effects of water droplets hitting a test article at hypersonic velocities; think about the understanding of whether a missile will survive being launched through a rain cloud,” said Bryan Sinkovec, capability development program manager. “The HHSTT rainfield was recently upgraded with a state-of-the-art fiber optic control and data collection system in time to support the 2021 HyTIP missions.”
The HSR program will continue into the spring of next year, and wrap up prior to the HyTIP sled tests that are set to being around next summer. The tests will serve to validate modeling and simulation efforts, and will further ensure critical edge-of-envelope conditions are accurately characterized.
“The HHSTT strives to provide the world’s best rocket sled test team and offer capabilities that are not offered anywhere else in the world,” Sinkovec added. “There are ground test facilities and even other tracks in this state, country and world, but recovered hypersonic monorail testing is something that cannot be done anywhere else in the world due to the HHSTT’s unmatched length and alignment.”
In addition to the HHSTT testing, the Air Force has also been carrying out captive-carrying testing of the AGM-183A Air-launched Rapid Response Weapon (ARRW) from under the wing of a B-52 Stratofortress. The first captive-carry test of the hypersonic missile platform was conducted on a B-52H at Edwards Air Force Base in California in 2019. While the program has been running behind schedule, the last such test of the missile was carried out this past August.
The first launches of the AGM-183A prototypes are set to take place a year from now in October 2021.
Peter Suciu is a Michigan-based writer who has contributed to more than four dozen magazines, newspapers and websites. He is the author of several books on military headgear including A Gallery of Military Headdress, which is available on Amazon.com.