COLORADO SPRINGS—Hypersonic test developer Stratolaunch successfully completed a key separation test of its Talon vehicle from the Roc carrier aircraft over Vandenberg Space Force Base’s Western Range off California’s central coast on May 13, clearing the way for the first powered hypersonic flight attempt later this summer.

The long-anticipated milestone mission, which was the fourth captive-carry flight of the unpowered Talon TA-0 drop test vehicle, “accomplished a number of primary and secondary objectives, including a clean release, stabilized flight all the way to flare and landing in the water,” says Zachary Krevor, CEO and president of Stratolaunch. 

The Mojave Air & Space Port-based company originally planned to conduct the separation test months ago but was forced to delay because of range time restrictions compounded by successive bouts of bad weather. Stratolaunch also hoped to release TA-0 on the last flight of the Roc carrier aircraft on April 1, but despite reaching the correct separation conditions controllers called it off after seeing what appeared to be off-nominal reaction loads data on the Talon.

Post-flight mission analysis showed the April release attempt would have worked, but the company said the flight was valuable as a practice run. It also was the first opportunity for Roc to fly within the targeted drop area with all systems operating and interacting with the Pacific test range telemetry systems.

Other than ballast to represent the weight of the vehicle’s standard Ursa Major Hadley rocket engine, the 28-ft.-long Talon was “representative of a full hypersonic vehicle” for the May 13 separation test, Krevor says. Weighing around 7,000 lb., the 14-ft.-span delta winged TA-0 was released by the Roc’s crew on the second pass along a northwest-southeast racetrack pattern aligned parallel to the coast.

Stratolaunch declines to specify the separation conditions but says they represented the exact speed and altitude target "release box" parameters that will be used for the first hypersonic flight test with the second vehicle, TA-1, now expected in late summer. According to flight data from Flightradar24, Roc was flying at around 21,650 ft. at a speed of around 240 kt. at the time of the release, which occurred at 11:14 a.m. PDT, or just past the halfway point of the 4 hr. 8 min. flight. 

Following separation, the Talon vehicle glided for 2.5 min. before impacting in the ocean in a stable landing attitude. Telemetry data indicated the fully autonomous vehicle's handling qualities were as predicted, matching aerodynamic and performance forecasts derived from earlier wind tunnel and computational fluid dynamics analysis, Krevor says. 

“We activated the vehicle propulsion ignition systems, and flared for landing and checked angle of attack, flare and landing speeds, all of which were good,” Krevor says. The vehicle landed intact but sustained damage on impact with the waves. Stratolaunch recovery crews were still hoping to salvage parts of TA-O for later analysis. The carrier aircraft, which was flown by pilots Evan Thomas and Dave Fedors with Brad Schab as flight engineer, returned to land at Mojave at 1:10 p.m. PDT. 

Stratolaunch now is focusing on preparations for the start of hypersonic flights with TA-1, which is undergoing vehicle-level testing before upcoming integration tests with Roc. Hot-fire ground runs of the Hadley engine also are continuing at Stratolaunch’s Mojave test site. Following these tests the same engine will be integrated into TA-1.

Assembly work on follow-on vehicles TA-2 and TA-3 also is underway. Both of these are reusable and are 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 now being completed, Krevor says. 

Rehabilitation work on runway 12-30, the longest of Mojave’s main runways and the one used for Roc operations, is meanwhile due to begin at the end of May and continue through early July. The airport’s current schedule will see the runway closed for 42 days. Limited closures of the airport’s other runways, 8-26 and 4-22, also will occur throughout the same overall period. Runway 12-30 will close again for another week in early August while new pavement markings are applied.