New Engineering Test Facility and Air-Bearing Vehicles Provide A New Testbed For Spacecraft And Space Systems

The Department of Electrical and Electronic Engineering at Stellenbosch University boasts a new planar air-bearing test facility. The facility contains a testbed for researchers to validate their projects and perform experiments in spacecraft and space systems. The Electronic Systems Laboratory (ESL) research group at Stellenbosch University focuses on controlling vehicles and robotics, including spacecraft and space systems. Under the supervision of Drs Lourens Visagie and Willem Jordaan, Daniel’s project included the design of air-bearing vehicles, a pose estimator which measures the states of the vehicles being operated on the test facility. The two air-bearing vehicles, Laika and Belka, are named after the first dogs to orbit the earth in a spacecraft.

Demonstration payload 

It also includes a demonstration payload which can perform a controlled manoeuvre with the vehicle to showcase the test facility’s capabilities. A feedback and communication system (FCS) measures the positions and velocities of the air-bearing vehicles on the table. Data is logged and displayed to the user in near-real-time.

Daniel’s new test facility will replace the ESL’s archaic air-bearing vehicle. An air bearing creates a pressurised film of gas between itself and the surface it hovers, establishing an interface with very low friction. It is used to emulate the low-friction environment that spacecraft face in orbit. The vehicles hover on top of this table during experiments.

Figure 1: A photograph of the outdated air-bearing vehicle and the glass platform previously used for low-friction experiments in the ESL.

3D-printed nozzles 

In the world of designing and manufacturing spacecraft components, hardware and software must be thoroughly tested and validated before they can be used in actual space missions – hence the need for satellite test facilities, otherwise known as simulators. As part of Daniel’s project, he also designed 3D-printed nozzles for air-bearing vehicles. The design and testing of these nozzles contributed to an international conference paper.

“In the meantime, Daniel’s project has gained further momentum. Gideon Serfontein, currently in his first year as a master’s student, is developing a satellite test setup that will work on the air-bearing vehicles, including an attempt to simulate “docking” of two satellites with them”, says

Prof Jordaan

Gideon’s system consists of a mechanism to allow two small satellites to lock together, a pose estimation system, and a control system to control the manoeuvres of the satellites in orbit, which should allow for a suitable range of approach angles and rotations. Gideon explains: 

“The aim is to make the adapters androgynous so both satellites use the same mechanism. Such a design would allow for modularity in future space missions and missions that enable additional spacecraft to be added on at a later stage. The pose estimation system will consist of a pattern of LEDs and a camera on the adapters to allow the system to determine the relative position and rotation of the satellites.”

Final thoughts

According to Gideon, based on this data, a control system will drive reaction wheels, thrusters, and electromagnets to bring the satellites together for docking. They will test this system on the air-bearing vehicles on the glass table. Moreover, the new test facility will add “flat-sat” components to the air-bearing vehicles that mimic the functionality of typical satellite subsystems, such as power, communications, and onboard computing. Sam Jefferey, a second-year master’s student, is currently working on this project. 

Read Daniel’s complete research paper here:  Daniel Christopher Jansen, The development of a test facility for satellite experiments, M.Eng dissertation, Stellenbosch University, 2021