A Prototype Aerospike: Another Fish in the Sea
Authors: Lengade Rohin 
Published: February 2021

Exploration is in our DNA! It is this spark of curiosity that has taken us to the moon and beyond. It is not easy to get into orbit. The rockets that we build today are quite sophisticated. Although technology will improve, these massive machines will increasingly be complicated to play with. One big reason being the ‘tyranny of rocket equation.’ As of now, we do not have any technology that will propel us out into space without using rockets. We are constantly finding ways to make rockets more efficient and launch more meaningful payloads into orbit. This is done by intelligently choosing the propellants, radical change in the design of rocket nozzles, applying different rocket engine cycles and improving the manufacturing process. Quite recently, we find a range of rockets being developed. The most commonly used engine cycle is the gas generator cycle (open cycle). Another way is to use electric powered turbo pumps. This cycle is far simpler than a gas generator cycle as it uses batteries to directly power the pumps. However, unlike propellant tanks with fuel, these energy powerhouses (batteries), do not reduce their weight during flight. Hence they represent dead weight. This technology is preferred for smaller rockets. There is another, not so often used engine cycle, called the full flow combustion stage or closed cycle. This cycle is the most complicated cycle and was considered almost impossible to build. Here, the exhaust from the turbine is fed into the combustion chamber, turning it into useful thrust. Apart from engine cycles, various engine nozzles have also been researched on. The conventional bell shaped nozzle, although widely used, is designed for a specific altitude. This means that the rocket needs to be multi-staged. The aerospike nozzle however, is an altitude compensatory nozzle. Although an aerospike has never flown to space, it has been rigorously tested. Here in, is a concept design of a prototype aerospike rocket engine. The intention of the design is to solve the engineering complexity involved in making efficient rocket engines. From the research carried out over a period of time, the following problems were noticed in an aerospike:

• Near full combustion of propellant was not observed.

• Overall heating of the spike increased.

• Thrust Vector Control was difficult.

The suggested design concept aims to tackle the above mentioned problems. The key technology used here is additive manufacturing. Additive manufacturing provides great flexibility in design and manufacturing. The complexity involved in manufacturing the aerospike can be tackled with this. The exhaust from the turbine can be used to create additional thrust by letting it out from the bottom of the toroidal spike. Near full combustion of the fuel-oxidizer mixture can be achieved by a dedicated combustion chamber rotated around the exhaust pipe of the turbine; unlike previous aerospikes which didn’t. The outer shape of the combustion chamber will be cylindrical, which will house traditional thrust vector control assembly. The heating of the nozzle can be reduced by using high grade graphite, tungsten and aluminum alloys with composite and ceramic materials. Also, for the rocket to be fuel efficient, the initial momentum to the turbines used will be given by permanent magnets mounted on the shaft, surrounded by windings and powered by supercapacitors. Once a desired rpm is achieved, a very small amount of fuel is used to maintain the same.