Y1 D202 – Kerbal Space Center
Jebediah Kerman and Bill Kerman became the first kerbals to travel at, and beyond, the speed of sound.
After refueling and inspecting the aircraft, the crew climbed aboard and rocketed, literally, down the runway.
After reaching 6000 meters altitude, Jeb and Bill leveled off. Because of reports from the previous crew, the rear roll controls were disabled at altitude to prevent over-rolling at high speed, and the throttle was set to 66%. Moments later, Mach 1 was achieved, 320 m/s at 5979 meters ASL.
After holding mach 1.02 for a few moments, the throttle was increased to maximum. Once mach 1.1 was achieved, the engine was shut down and the aircraft glided back to KSC for a landing.
It's Not Rocket Science 