Stratolaunch 747-400 seen carrying an undisclosed rocket in Mojave

Stratolaunch's Boeing 747-400 carrier aircraft, the "Spirit of Mojave," was photographed with a previously unseen rocket under its left wing. The images were shared with an aviation publication by photographer Brennan O'Neill.

They were taken on the afternoon of 9 October, as the aircraft landed at Mojave Air & Space Port in California. A Cessna Citation business jet flew alongside as a chase plane. Tufts were fitted on the pylon and on the underside of the wing behind the rocket.

The aircraft appears to have flown a test flight of a rocket not previously disclosed, intended to add to Stratolaunch's hypersonic testing capabilities. The flight was most likely a captive carry mission, used to assess how the rocket behaves when installed on the 747 and to study the airflow around it.

Tuft testing is a visualisation technique used in flight test and wind tunnel work to study airflow direction, strength and boundary layer properties. Short lengths of string are attached to a surface and blown downstream as air passes over them.

Stratolaunch announced four new launch vehicles in 2018: the existing Pegasus rocket, two variants of a Medium Launch Vehicle that had yet to be developed, and a future space plane. Those programmes have been abandoned, and the company's website now lists only the Talon.