ESA Propelling CubeSat with Butane

Artist rendering of the GomX-4 pair in formation around Earth - Credit: GomSpace

The European Space Agency (ESA) demonstrated the use of a butane based cold gas propulsion system to adjust the orbit of the GomX-4B CubeSat. During the mission GomX-4B was able to maintain formation with its twin, GomX-4A, up to 4500 km away. The two CubeSats also tested an inter-satellite radio link between each other and Earth. These tests are verifying the operation of a planned CubeSat constellation.

GomX-4B is a 6U CubeSat (measuring 30 cm by 20 cm by 10 cm) weighing 8 kg that includes an inter-satellite communication system, a hyperspectral imager, a star tracker (HyperScout), and the butane based cold gas propulsion system. The spacecraft contains four 1 mN thrusters that fire in pairs while keeping one set in reserve. For comparison, many existing CubeSats use a monopropellant (i.e. hydrazine) for propulsion that provide more thrust (up to 1 N) but a lower specific impulse (lower efficiency). Gomx-4B's propulsion system allows it to adjust its orbital speed by a total of 10 m/s (about the speed of kicking a ball).

The spacecraft stores 130 grams of liquid butane in two spherical titanium tanks. The butane is stored as a liquid to increase the amount of material stored. The cold gas thruster system takes up two half-CubeSat units on one side of the spacecraft.

Butane cold gas thruster system used on the GomX-4B that has four 1 mN thrusters and two titanium tanks for storing butane. Takes up two half-CubeSat units in size. - Credit: Nanospace

While not the first CubeSat to include an on-board propulsion system, it is the first to operate a butane based cold gas thruster in orbit. This further demonstrates the capability of cold gas propulsion technology. Other CubeSat propulsion systems proposed include electric thrusters, electrospray thrusters, warm/cold gas systems, monopropellant systems, solid rocket motor systems, electrolysis of water systems, and solar sails [Zondervan et al., 2014].

GomSpace manufactured the GomX-4 spacecraft, with both launched on February 2, 2018 from Jiuquan, China. GomSpace is starting development on GomX-5, a 12U follow-on CubeSat. GomX-5 will further evaluate CubeSat maneuverability and high speed communication links. It is scheduled to launch in 2021.

Roger Walker, head of ESA’s Technology CubeSats, holding a 3D printed model of GomX-4B, which while the size of a cereal box, is the largest CubeSat ESA has yet flown - Credit: ESA-G. Porter

Developing reliable and efficient CubeSat propulsion systems is essential for precise formation flying. Potential missions with this technology include communication constellations, deorbiting space debris, and near-Earth object mining. The CubeSat industry will continue to deliver innovative solutions for propelling CubeSats on ever more expansive missions.

References

  • http://www.esa.int/Our_Activities/Space_Engineering_Technology/Mission_accomplished_for_ESA_s_butane-propelled_CubeSat

  • http://www.rocket.com/cubesat

  • Zondervan, Kevin, et al. "CubeSat solid rocket motor propulsion systems providing delta-Vs greater than 500 m/s." (2014).