Over the past few months Amaero and NextAero have been working on an additive manufactured (3D printed) aerospike rocket engine.
For more see http://www.amaero.com.au http://www.nextaero.com.au or check out some footage of the hot fire:    • Additive Manufactured Aerospike Rocke...  

What is an Aerospike?
The bell of conventional rocket engines directs the rocket exhaust in one direction. Atmospheric pressure also plays a part in directing the exhaust, so the engine only works with peak efficiency at one altitude, for example at launch. As the rocket climbs the flame spreads out, reducing thrust.
The aerospike design works by firing the gases along a spike and using atmospheric pressure to create a virtual bell. The shape of the spike allows the engine to maintain high efficiency over a wider range of altitude/air pressure. It’s a much more complex design challenge and is difficult to build using traditional technology.
The team have created a novel three-chamber aerospike engine, which also allows for thrust vectoring without gimbaling systems. This means that instead of tilting the engine, which is done to control a vehicle’s flight path, the engine can be firmly mounted to the chassis and instead vary the direction of the thrust via the pressure in the combustion chambers. This offers weight and cost savings, which the team hope to investigate in the future.
The rocket engine the team have created is an initial demonstrator. It is not intended for flight, but rather to show the possibilities if traditional manufacturing constraints are removed. The opportunity for researchers working in aerodynamics and combustion to work with Amaero’s experts in 3D printing enabled some of the key problems associated with the aerospike nozzle to be solved. Once the design team were unshackled from the usual constraints of traditional manufacturing, curves and shapes ideally suited to optimising fluid flows and combustion gases could be brought to life.

The Additive Manufactured aerospike rocket engine is the result of a collaboration between Amaero Engineering and NextAero, supported by Woodside Energy and Monash University.