Rocket Sled Traveling At 7,200 km/h (4,363 mph) Successfully Stopped During Hypersonic Test At Holloman

Hypersonic sled
An image of the reusable rocket sled travelling at 6,400 feet per second (7,200 km/h) during the late March 2022 test. (Image credit: USAF)

The test marked the fastest recovery of a monorail sled in over 30 years, and the first time a planned reusable sled was ever recovered at those speeds. The test paves the way for more hypersonic weapons testing.

Holloman High Speed Test Track (HHSTT), is a 51,000 feet (about 10 miles) track located at Holloman Air Force Base, New Mexico, and operated by the 846th Test Squadron. It uses a special 9-inch monorail sled that can be launched at speeds in excess of 9,000 feet per second, that is around Mach 8.6 calculating for altitude.

As we have explained in detail in a previous article, the track is used for the Hypersonic Readiness program, which is a series of tests being conducted by the 846th Test Squadron, belonging to the 704th Test Group of the Arnold Engineering Development Complex, to support programs and projects that involve hypersonic weapons (weapons travelling at speeds over Mach 5) including the Air-Launched Rapid Response Weapon (ARRW).

The mission of the HHSTT is “to provide a cost-effective, realistic, dynamic test environment for the entire acquisition community, including the DoD, and contractors.” Various tests are carried out at the track, including simulated ejections using ATDs (Anthropomorphic Test Devices), and weapons.

Interestingly, in late March, the 846th Test Squadron at the Holloman High Speed Test Track successfully stopped a reusable sled traveling at 6,400 feet per second (about 7,200 km/h, Mach 5.7 at ground level) on a monorail, making it a historic event for the team’s Hypersonic Sled Recovery, or HSR, effort.

Another image of the reusable rocket sled during the March 2022 test. (Image credit: USAF)

“What you accomplished marked the fastest recovery of a monorail sled in over 30 years, and the first time we have recovered a planned reusable sled at those speeds ever,” Lt. Col. Paul Dolce, Commander, 846th Test Squadron, said in a public release. “These efforts will now setup our future HyTIP [Hypersonic Test and Evaluation Investment Portfolio] runs for success and add a new capability for our hypersonic customers.”

Thanks to their promised capability to effectively penetrate and control contested battlespace (Anti-Access/Area Denial Zone), overcoming challenges of time, distance, and enemy defenses, hypersonic weapons are attracting a lot of interest. And, according to the U.S. Air Force, this translates into a significant increase in demand for hypersonic weapons testing, with a focus on improving its high-speed breaking capability in order to recover sleds for post-test analysis. Indeed, it’s extremely important to recover reusable sleds after they have carried out their hypersonic runs, as data collected during the tests can be collected and analysed and used for further hypersonic weapons testing. The late March 2022 test, that set the record for the fastest recovery mission in 30-plus years is a further step in that direction.

By the way, “hypersonic” has become a kind of “buzz word” recently (just think of “Top Gun: Maverick” and its Darkstar aircraft we have discussed here). A particular kind of hypersonic weapon has also been used by Russia in Ukraine. In fact, the Russian Ministry of Defense announced Russian forces made use for the first time of the Kinzhal hypersonic aero-ballistic missiles to destroy a large underground warehouse of missiles and aviation ammunition of Ukrainian troops in the village of Delyatyn, Ivano-Frankivsk region, in Ukraine’s western part, on Mar. 18, 2022.

Kinzhal is basically an air-launched Iskander-M SRBM (short-range ballistic missile) that uses a MiG-31 Foxhound or Tu-22M3 Backfire assets as an air-breathing first stage to increase its range: in fact, it is actually not a “hypersonic weapon” in the sense that it is an air-breathing missile based on scramjet technology and, as a ballistic missile, it flies at hypersonic speed with a reported cruise missile-like flat flight profile.

Hypersonic air-breathing vehicles utilize air captured from the atmosphere to achieve sustained propulsion without the need of rotating parts. The fast-moving, compressed air flow coming through the scramjet engine’s inlet is mixed with a hydrocarbon fuel and ignites, before being ejected trough a nozzle which propels the missile at a speed greater than Mach 5.

More or less in the same period as Russia made public the use of the Kinzhal missile in Ukraine, DARPA and the U.S. Air Force completed a free flight test of the Lockheed Martin version of the Hypersonic Air-breathing Weapon Concept (HAWC): the test happened in mid-March but the news was withheld for two weeks to avoid escalating tensions with Russia.

About David Cenciotti
David Cenciotti is a journalist based in Rome, Italy. He is the Founder and Editor of “The Aviationist”, one of the world’s most famous and read military aviation blogs. Since 1996, he has written for major worldwide magazines, including Air Forces Monthly, Combat Aircraft, and many others, covering aviation, defense, war, industry, intelligence, crime and cyberwar. He has reported from the U.S., Europe, Australia and Syria, and flown several combat planes with different air forces. He is a former 2nd Lt. of the Italian Air Force, a private pilot and a graduate in Computer Engineering. He has written five books and contributed to many more ones.