World’s first aerospike engine aircraft to take to the skies in September

Aiming to bounce back from an accident while testing its demonstrator MIRA, German startup Polaris Aerospace is on course to develop the next iteration of its demonstrator modules.

The MIRA I prototype was poised for the world’s first aerospike rocket engine test, but it crashed on takeoff before its innovative propulsion system could ignite.

The firm has now taken delivery of the glass-fiber composite structures of its most recent vehicles, MIRA II and MIRA III.

The demonstrators are a precursor to the development of Aurora , the firm’s next-generation spaceplane concept for cargo and passenger transport.

Aerospike engine trial

Most rockets are designed to work efficiently within a specific altitude range, which is determined by the shape of their bell-shaped exhaust nozzles. These nozzles adjust the pressure and flow of gases to maximize thrust.

However, as a vehicle’s altitude and speed change, the ideal nozzle shape changes too, which is why rockets often require multiple stages. The aerospike engine offers a different approach. Instead of a traditional nozzle, it directs exhaust down the sides of a central spike, allowing the surrounding air to act as the other side of the nozzle.

This design adapts to varying altitudes and speeds, maintaining consistent efficiency. While it may not surpass a bell nozzle at its peak performance, the aerospike offers reliable efficiency from launch to space.

The MIRA project aims to develop a fully reusable spaceplane capable of carrying cargo or passengers. The spaceplane would operate as a single-stage to orbit (SSTO) and can take off and land on conventional runways.

The MIRA I successfully completed several test flights using its four conventional kerosene turbine engines. However, after the AS-1 LOX (Liquid Oxygen)/kerosene linear aerospike rocket engine was installed, the aircraft was destroyed during takeoff at over 100 mph (160 kph). This incident stopped it from becoming the first aircraft to fly powered by an aerospike engine.

Polaris’ supersonic future

The identical twin aircraft MIRA II and III are 16.4 feet (five meter) long and have a 30 percent larger wing area than their predecessor, MIRA, which was 14 feet (4.3 meter) long. This increased size significantly enhances flight-testing capabilities.

Additionally, the design has been greatly improved, incorporating lessons learned from previous tests. Each aircraft will be equipped with four turbines and a LOX/kerosene linear aerospike rocket engine.

Both airframes are made of fiberglass, as they are only for demonstration purposes. The company plans to use Carbon Fiber Reinforced Polymer (CFRP) for its supersonic and hypersonic aircraft.

“We decided to build two vehicles rather than one in order to speed up flight testing and to have a reserve aircraft. In the coming weeks we will assemble and integrate the new aircraft, make them flight-ready, and prepare the documentation required for the operation licenses,” said the firm in a post on LinkedIn .

Polaris is hopeful of completing the assembly and starting the fight-testing of the new demonstration in September itself.

The MIRAs are set to be Polaris’ final pure technology demonstration vehicles. In 2025, the team will develop and launch the approximately 8-meter-long supersonic successor, NOVA, which will serve as the prototype for a commercial product.