Aircraft

World's first aerospike aircraft to fly this month after crash setback

View 6 Images
Polaris Spaceplanes MIRA II and III, looking pretty slick and awaiting install of their four turbine engines as well as the AS-1 LOX/kerosene aerospike engine
Polaris Spaceplanes
Polaris Spaceplanes MIRA II and III, looking pretty slick and awaiting install of their four turbine engines as well as the AS-1 LOX/kerosene aerospike engine
Polaris Spaceplanes
Polaris Spaceplanes MIRA II and III
Polaris Spaceplanes
Nearly completed Polaris Spaceplanes MIRA II and III
Polaris Spaceplanes
This September, the MIRA II and III will be taking flight
Polaris Spaceplanes
Polaris Spaceplanes demonstrator nearing time for demonstration
Polaris Spaceplanes
The MIRA looks fast
Polaris Spaceplanes
View gallery - 6 images

The world's first flight test for an aerospike rocket engine ended in disaster, but Polaris Aerospace is back on track, preparing to fly two new prototypes for its MIRA supersonic/hypersonic aerospike spaceplane platform within weeks.

Immediately after the MIRA I crashed upon takeoff, Polaris Spaceplanes stated it would be going forward with the MIRA II and III. True to word, Polaris has unveiled two new, yet-to-be-fully completed airframes in a recent LinkedIn post.

The MIRA II and III are identical 16.4 ft (5 m) airframes with 30% more wing area than their predecessor, the MIRA I. Polaris opted to create two identical airframes in order to speed up flight testing as well as have a "reserve" aircraft if need be. "In addition," writes the team, "the design has been greatly improved compared to MIRA with incorporating all the lessons learnt so far."

This September, the MIRA II and III will be taking flight
Polaris Spaceplanes

Both are fiberglass airframes, as they are demonstrators only. The company intends to use Carbon Fiber Reinforced Polymer (CFRP) for its supersonic and hypersonic aircraft.

While the MIRA I did make several successful test flights before crashing, it did so using its four conventional kerosene turbine engines. It was only once the AS-1 LOX (Liquid Oxygen)/kerosene linear aerospike rocket engine was fitted that it was destroyed on takeoff at over 100 mph (160 kph) – preventing it from becoming the first aircraft ever to fly under aerospike power.

The MIRA I craft suffered just enough crash damage to not be worth salvaging, with the company instead moving on to the MIRA II and III
POLARIS Spaceplanes

Aerospike Engines

Most rockets only work efficiently in a certain altitude range, largely defined by the shape and size of their bell-shaped exhaust nozzles, which tune the pressure and flow of the expanding gases to produce maximum thrust. As the ambient air pressure and speed of the vehicle change, so does the ideal shape of that exhaust nozzle – and this is one reason why most space launch vehicles use multiple stages.

Comparison of a conventional rocket engine and an aerospike
NASA

The aerospike engine is different – and in theory, it should be effective from sea level all the way up into space. Essentially, the aerospike design doesn't use a traditional nozzle – it fires its rocket exhausts down the sides of a central surface shaped to mimic one side of the interior wall of a bell-shaped nozzle, and the ambient airflow around the rocket acts as the remaining walls of the nozzle.

This test of twin Rocketdyne XRS-2200 Linear Aerospike engines, originally built for Lockheed Martin's X-33 program, was performed on August 6, 2001, at NASA's Stennis Space Center
NASA

So the aerospike's virtual nozzle characteristics change constantly in response to aerodynamic flow. The rocket naturally tunes itself as speed and altitude changes. It'll never exceed the efficiency of a bell-shaped nozzle running right in its sweet spot, but its average efficiency from takeoff to orbit should be good enough to do the job, in a way that cuts down on moving parts.

The aim of the MIRA project is to develop a cargo and/or passenger-carrying spaceplane running a single stage to orbit (SSTO), that can takeoff and land on runways, and that's fully and rapidly reusable.

Polaris eventually hopes to build reusable spaceplanes for cargo and passenger transport
Polaris Spaceplanes

Hopes are high that all goes well with the 2nd generation aircraft.

Earlier test flights were held at the Peenemünde Airfield in northern Germany, and over the waters of the neighboring Baltic Sea. It's unknown if that's where testing will begin again with the latest iterations of the MIRA – however, Polaris has announced that it expects to have them airborne within this month.

So we should soon see the very first aerospike engine in flight since Rocketdyne invented them over 70 years ago. We'll definitely keep you posted when it happens. In the meanwhile, you can see the first prototype giving its aerospike engine a blast at 60% power for a few seconds in a runway roll test, in the video below.

The aerospace company is already making plans to test NOVA, a 26.2 ft (8 m) supersonic prototype it intends to develop into a commercial product, starting next year in 2025.

A video from Zweites Deutsches Fernsehen Today, in German only, offers a few glimpses of footage from behind the scenes, as well as what appears to be the moments before the MIRA I crash when it diverted off the runway moments before takeoff.

Source: Polaris LinkedIn

View gallery - 6 images
  • Facebook
  • Twitter
  • Flipboard
  • LinkedIn
0 comments
There are no comments. Be the first!