KAIST develops a propulsion device for attitude control of upper stage space rockets

A thruster is a small rocket to generate the reaction force required to control the attitude of a spacecraft. The precise attitude is essential to inject the spacecraft into the desired orbit.

Article  |  Spring 2015

Rocket Lab KAIST has been working on a monopropellant thruster for more than ten years. The endeavor has finally won recognition, as Korea’s space agency selected the KAIST-developed thruster for the reaction control system of the next space rocket, KSLV-II, an indigenous Korean space rocket and the platform of Korea’s national space exploration program for the next decade.

The KAIST-developed thruster outperforms the conventional propulsion device. Furthermore, the monopropellant being used in the thruster is non-toxic and easy to handle, while the conventional monopropellant is extremely toxic and even carcinogenic. As a result, ground tests of the conventional thruster require a huge scrubbing facility and spacesuit to protect the operating personnel. Design, fabrication, and firing tests of the thruster confirmed that the thruster delivers the desired performance for KSLV-II.

A monopropellant thruster consists of a feed control valve that regulates the propellant flow and a thrust chamber that decomposes monopropellant by a catalytic reaction and releases thermal energy. The thermal energy is then converted into kinetic energy of the reaction product gas by accelerating through a converging-diverging nozzle attached to the thrust chamber. Thrust is the reaction force of the high speed exhaust flow of the reaction product gas. Key technologies, including the propellant decomposition catalyst and precision propellant feed devices were developed at Rocket Lab KAIST. The technology was transferred to Space Solutions, Inc. in 2009. The company will work on the system integration of the propulsion system of the upper-stage space rocket.

The national space agency is also interested in a bigger bipropellant rocket that Rocket Lab KAIST has developed for roll control of the second-stage space rocket. The initial design of the system was based on the reaction force that was generated by the high pressure turbo-pump exhaust gas. The bipropellant rocket developed by Rocket Lab KAIST can deliver up to 250kgf of thrust force and weighs far less than the turbo-pump based system. Rocket Lab KAIST has developed a catalyst ignited bipropellant rocket and hypergolic bipropellant rocket, both of which can be operated in pulses without ignitors. The bipropellant rockets can be used for the main engine of a spacecraft for an orbit transfer and soft landing of a moon lander for a lunar exploration mission.