German start-up POLARIS Spaceplanes has marked a significant milestone by successfully conducting roll and flight tests of its MIRA II demonstrator. Powered by the company’s 3D-printed AS-1 linear aerospike engine, the five-meter-long prototype represents a critical step toward the development of the full-scale AURORA spaceplane, set to debut in 2028.
The unmanned MIRA II took off from Peenemünde Airport using jet turbines and performed a three-second in-flight burn of its 1 kN LOX/kerosene aerospike engine over the Baltic Sea. Generating 900 newtons of thrust, this test marks the world’s first airborne trial of a linear aerospike engine—despite a minor LOX tank leak resulting in the loss of an access hatch.
Aerospike engines feature a wedge-shaped nozzle design that optimizes thrust across varying altitudes, boosting efficiency and reducing weight compared to traditional bell-nozzle engines. However, their intricate cooling systems and extreme operating temperatures present manufacturing challenges. POLARIS has addressed these hurdles with additive manufacturing, leveraging 3D-printed components produced by AM Global for faster iteration and reduced downtime between flights.
Looking ahead, POLARIS plans to further refine its engine technology through tests with its twin demonstrator, MIRA III, while preparing for NOVA, a larger prototype. These efforts pave the way for the AURORA spaceplane’s 2028 launch, signaling a leap forward in aerospace propulsion innovation.
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