The 2 stage rocket was built by Curt von Delius, which was boosted by a CTI N5800 to a CTI N1100 sustainer with an 11 s coast delay. The rocket flew to 244,186 ft MSL, although the GPS units did lockout due to the COCOM speed and altitude limits, the apogee was still able to be calculated.
The flight becomes the first amateur 2 stage launch to break the 200,000 ft barrier.
[Edit, 8/11/2018: The use of the term “2 stage rocket” refers to each stage being powered]
Video Caption: Experience this amazing supersonic near space flight through on board HD video. Curt von Delius’s state of the art PHX4 launched on June 16, 2018 from the Black Rock Desert, Nevada. Accelerating to over 3.5 times the speed of sound the rocket coasted to 46 miles above sea level. This is the highest flight of any amateur two stage rocket. The reusable design was recovered using Disc Gap Band Parachutes and touched down 6.36 miles from launch.