KAIST develops a sounding rocket using a hybrid propellant rocket engine

A sounding rocket is a rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. Using a hybrid propellant rocket engine, the KAIST Rocket Lab developed the SNUKA II with a team made up of members of Seoul National University, Sol-top, and NARA-Space.

Article  |  Spring 2018

Have you ever seen a rocket being launched, such as the Falcon 9, which was made by Space-X? It was launched and landed safely and has been reused again. This success in landing on a set destination has encouraged others to develop more advanced rockets. Research on new technologies relating to rocket development is currently a hot topic around the world. Recently, North Korea launched several ICBMs (Intercontinental Ballistic Missiles), and with this in mind, research into rocket development has become important for South Korea. There is a great deal of secrecy surrounding rocket technology. It is difficult to transfer technologies from one country to another, so they must be developed by each country individually.

A sounding rocket is one of the best ways to acquire basic skills for developing space launch vehicles. Surrounding rockets can reach an altitude of 40~1500 km, which is between weather balloons’ and satellites’ operation ranges. The purpose of the rocket is measuring the atmosphere, providing a zero-gravity laboratory space, and taking pictures of celestial objects. Thus far, a number of developed countries have invested in programs and researched to acquire basic rocket technology and to perform scientific experiments during sub-orbital flights. Just as with the rockets called KSR series which was made by KARI(Korea Aerospace Research Institute), Korea has also launched sounding rockets several times. In cooperation with Seoul National University, the KAIST Rocket Lab developed a sounding rocket called SNUKA II in 2017.

SNUKA II is 3.5 m in size and weighs 57.5 kg. The rocket uses a hybrid propellant rocket engine and produces 2500 N thrust. The hybrid propellant rocket engine is a rocket engine that uses liquid oxidizer and a solid fuel. The LOX(Liquid Oxygen), N2O(Nitrous Oxide), H₂O₂(Hydrogen Peroxide) are used as the liquid oxidizers. HTPB(Hydroxyl-Terminated Polybutadiene), and PE(Polyethylene), PMMA(Polymethyl Methacrylate) are used as solid fuels. SNUKA II uses a H₂O₂/HDPE hybrid rocket engine. This rocket marks Korea’s first ever usage of H₂O₂ as a liquid oxidizer. Fig. 1 shows how the hybrid propellant rocket engine works. When hydrogen peroxide is injected from the injector, it is met with catalysts. Then, hydrogen peroxide decomposed into hot oxygen and water vapor.

 

Finally, the gases met the solid fuel and ignited, resulting in a high-speed and -temperature (2000°C) gas leaving the nozzle, creating huge amounts of power. To achieve high thrust, huge amounts of hydrogen peroxide were injected into rocket engine, and a new type of dome manifold was adopted to withstand high flow rates.

For controlling the rocket and knowing its trajectory, there is some equipment in SNUKA II. The attitude and acceleration sensors, the GPS sensor, and the pressure altimeter were all mounted in the navigation system, which was made by the companies Sol-top and also NARA-Space. This navigation system can measure and save 10 altitude, acceleration and GPS data in one second. Also, the valve that blocks the propellant injection can be controlled by the navigation system. When the rocket goes to an unexpected dangerous trajectory, the navigation system automatically halts the rocket engine from flying any further. A parachute has been mounted on the SNUKA II and the pressure altimeter, the GPS altimeter, and the timer help the parachute to eject in appropriate conditions.

Normally, the parachutes were ejected by giving an electric impulse. However, for the SNUKA II, the parachute was ejected by using a bellows. This rocket is currently being inspected through methods such as a firing test (Fig.2) and will be launched in the USA in 2018. After launching the rocket, its trajectory will be compared with the results derived from the simulation program, and the validity and improvement of the simulation program will be checked. The SNUKA II is larger rocket than the SNUKA I, and it will be able to identify problems and phenomena that occur when the rocket is scaled up through the launch.

 

Ref: M. Viscardi, et al. (2009), “HYBRID ROCKET STAGE AS A SUBSTITUTE FOR THIRD AND FOURTH STAGES OF VEGA LAUNCHER”, AIDAA