COLORADO SPRINGS—Stratolaunch moved another step closer to the first flight of the Talon hypersonic test vehicle following a captive carry flight with live propellants over Southern California on Dec 3.

The 3-hr., 22-min. flight of the Roc carrier aircraft and rocket-configured Talon TA-1 vehicle—fueled with liquid oxygen (LOx)—followed a series of ground tests which culminated with a taxi test on Nov. 21 at Mojave Air & Spaceport.

“It was the first time flying with LOx on board, so we were making sure we were seeing everything we expected in terms of temperatures and the environment,” Stratolaunch CEO and President Zachary Krevor said. The bulk of the flight was spent at around 22,500 ft.–close to the release altitude attained during the separation test flight with Talon TA-0 on May 13. For that flight, according to Flightradar24 data, Roc was flying at around 21,650 ft. at the time of the release.

An assessment of whether another captive carry flight will be required will depend on data collected from the Dec. 3 sortie, Krevor says. “We did this flight in our own backyard [restricted airspace north of Edwards AFB, California] to get key things accomplished, and we may decide we want another captive carry in the West Range.” He was referring to Vandenberg Space Force Base’s Western Range off California’s central coast where the hypersonic flight attempt will take place.

“We also have a couple more ground tests to complete, so we will see what makes the most sense” on timing for a potential second captive carry flight and follow-on first hypersonic flight attempt,” Krevor says. Powered by the 5,000-lb.-thrust Ursa Major-built Hadley rocket engine, the Talon is designed to fly at hypersonic speed for several minutes. The TA-1 mission will be the first to evaluate the complete system in free flight at full power.

Meanwhile, assembly work on follow-on vehicles TA-2 and TA-3 continues. Both are reusable and designed to recover for landing at Vandenberg SFB after Mach 5-plus flights. TA-2 is fully assembled and undergoing integrated systems tests, while the structure of TA-3 is undergoing completion work.

The latest captive carry test comes less than a week after Stratolaunch announced a contract award from Leidos, the prime contractor for the U.S. Navy’s Multiservice Advanced Capability Test Bed (MACH-TB) program. The contract, which covers five Talon-A hypersonic flights with optional payloads, is funded by Naval Surface Warfare Center, Crane Division through the Strategic and Spectrum Missions Advanced Resilient Trusted Systems Other Transaction Agreement.

Describing the award for a block of flights as a “great vote of confidence” in Stratolaunch, Krevor says the contract “sets us up the flight manifest for 2024.” Together with the extra inflight launch capability that Stratolaunch is adding with the former Virgin Orbit Boeing 747-400 carrier aircraft, the company is setting up to offer “multiple hypersonic tests in multiple locations.” This will “enable us to build up to a cadence that the Pentagon has been asking for,” he adds.

The 747-400 is expected to arrive at Mojave in Stratolaunch colors over the next few days. It is likely to perform the bulk of its hypersonic launch test missions from sites around the East Coast, while the Roc is set to operate principally from the West.