January 27, 2023
NASA’s recent validation of its 3D-printed RDRE aerospike engine has piqued interest in the aerospace community. The successful hot fire tests have opened up the possibility of creating a larger version of the RDRE, which is a major development in the aerospace industry.
Traditionally, rocket nozzles have been bell-shaped, which over-expands the gases and makes it inefficient. On the other hand, an aerospike engine fires the exhaust along the outside edge of a wedge-shaped protrusion called the “spike,” forming one side of a “virtual” bell, with the other side being formed by the outside air. This creates more efficient thrust as altitude increases. As you can see in the image below.
However, cooling traditional engines incurs a huge mass penalty. 3D printing lighter weight aerospike engines solves this issue, as seen in NASA’s recent tests. The RDRE aerospike engine was printed with an LPBF process, using GRCop-42, a copper alloy developed by NASA. The engine was fired over a dozen times, totaling nearly 10 minutes in duration.
RDRE engines use a series of small controlled explosions to generate continuous thrust, unlike traditional rockets that use a single continuous burn. Fuel and an oxidizer are injected into the combustion chamber, where they ignite and create a wave-like pattern of detonations that travel around the circumference of the chamber, converting more of the fuel’s energy into thrust. RDRE engines are more fuel-efficient, have a higher thrust-to-weight ratio, and can operate with a wider range of fuels and oxidizers.
The RDRE tests were successful in proving their ability to operate for long durations while withstanding the extreme heat and pressure environments generated by detonations. The tests also demonstrated deep throttling and internal ignition, bringing the technology closer to being used with future flight vehicles.
“Additive manufacturing certainly allows for very complex designs, but this novelty propagates and enables other new technologies such as advanced propulsion,” said Paul Gradl, Principal Engineer at NASA.
This recent development is a major step forward in the aerospace industry. RDRE engines have significant advantages over traditional liquid-fueled rockets and are of great interest to space engineers. With further development, they could be used in future space missions. The validation of the RDRE aerospike engine marks the beginning of a new era in space propulsion technology.