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Why air bearings are used to test satellites

Satellite testing can be undertaken using friction-free, 3DOF spherical air bearings from PI. [Credit: PI]

 

 

The number of active satellites in space keeps growing at an accelerated pace. In July, Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, estimated there are more than 10,000 active satellites orbiting our planet. Predictions see that number growing by several 10,000s -- possibly up to 100,000 by the end of the decade.

With the advent of compact CubeSats and commercial spaceflight, the cost of building and transporting a satellite into space has dropped significantly, which has made feasible the use of a global network of low earth orbit (LEO) satellites for free space optical communication via laser beams.

This emerging technology has huge potential for rapid growth, and the increased demand for satellites also drives the need for new test equipment. Commercial and academic institutions developing these satellites continuously work on improved test systems and methodologies to fully validate their hardware before launch.

PI's 3-degrees-of-freedom (3-DOF) spherical air bearing systems are commonly used to test the attitude control systems of small satellites. The frictionless nature of the spherical air bearing makes it easy to simulate a zero-gravity environment, allowing the satellite's pitch, roll, and yaw control systems to function as they would in space without cumbersome and expensive test simulations, such as traditional drop testing.

VIDEO: Spherical air bearing demonstration. [Credit: PI]

PI's A-651 - A-657 series of spherical air bearings offers frictionless motion in three rotary degrees of freedom -- with unrestrained rotation about the vertical Z-axis and +/-45° tilt motion about the horizontal X and Y axes. These air bearings are available with diameters from 50 mm to 300 mm and can carry payloads from less than 20 lb up to 1,400 lb with compressed air at 80 psi.

This variety of air bearing sizes provides solutions for nearly any small satellite, from 1U picosatellites to half-ton mini satellites. The moving element of the PIglide HB spherical air bearing is lightweight to reduce moving mass and moment of inertia, ensuring the test system closely simulates actual satellite behavior.

What is attitude control and zero-gravity simulation testing?
In attitude control testing, spherical air bearings are extensively used for testing because they provide a frictionless environment that allows for the simulation of pitch, roll, and yaw movements, which are essential for assessing how a satellite will orient itself in space.

For zero-gravity simulation, air bearings allow frictionless motion in three degrees of freedom. This capability is vital for testing how satellites will behave in the weightlessness of space without the need for expensive and complex drop tests or parabolic flights.

Most of the small satellites will be used in free space optical communications, promising affordable, high-speed internet at any place on the planet.

Spherical bearings are also used in systems for precision chip contacting and optical alignment. Due to the use of spherical bearings at both ends of the drive screw shaft, it is possible to build extremely stiff drive screws. This arrangement allows precision alignment of the drive screw shaft, due to the motion of one spherical bearing relative to the other.

In addition to the spherical air bearings, PI also provides other solutions for space applications, such as 6DOF hexapod positioning systems that can be used in the validation of optical terminals, such as the OTVT at the MIT Lincoln Laboratory and fast steering mirrors for free space optical communication in LEO satellites.

Source: PI

Published August 2024

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