Undeterred, Polaris is building two bigger prototypes.

The MIRA I, from German aerospace startup Polaris Raumflugzeuge, was traveling at approximately 105 mph (169 km/h) during takeoff when a "landing gear steering reaction" plus a side wind caused a "hard landing event," rendering the space plane inoperable and it's fiberglass airframe damaged beyond repair.

Its subsystems remained mostly intact – however, rather than attempt to repair the prototype spaceplane, Polaris has opted to decommission the 4.25-meter (13.9-ft) long MIRA I to go ahead with the identically shaped 5 m (16 ft) MIRA II and III design. Basically larger copies of the MIRA I.

This ill-fated test was set to be MIRA I's first chance to fire its AS-1 LOX (Liquid Oxygen)/kerosene linear aerospike rocket engine in actual flight – and indeed, the first time any aerospike engine had been properly flight-tested in an actual aircraft.

Yes, an aerospike rocket engine, developed in-house by Polaris. If that sounds like something from science fiction, well, it almost is. They were first invented in the 1950s by Rocketdyne, but have never been used outside of a lab.

The easiest way to imagine an aerospike engine is to take a conventional bell-shaped rocket engine nozzle, and more or less turn it inside-out, making the inner cross section half of the bell shape and leaving the outside open to the atmosphere.

Why? Traditional bell-shaped rockets can only operate at peak efficiency at a specific altitude, defined by the shape and size of the bell. As the rocket goes higher in altitude, the atmospheric pressure decreases and efficiency drops – thus requiring different rocket stages, using different bell shapes and sizes for different phases of a launch.