Measuring the Mass Properties

To ensure any simulations of the platforms is representative of the experiment, it is important that the mass properties be correct. Generally, this step only needs to be completed when there is a significant weight change to the platform (for example, adding the robotic manipulator with a heavy gripper attachment). The mass properties that are required for an accurate simulation are:

• Spacecraft mass
• Spacecraft center of mass
• Spacecraft inertia
• Phasespace LED positions relative to the center of mass

The measurement of mass and the center of mass can be performed using the three point method. This technique requires three scales in the following configuration:

A free-body diagram (FBD) for this configuration would take the form:

From this FBD, the following equations can be derived by taking the moments about A:

x = (B+C) E W ^-1

y = (C-B) D (2W) ^-1

Where A, B, and C are the force readings at each corner (or in this case, the scale measurement multiplied by gravity), and W is the total of all three force measurements. A visual representation of the measurements made in 2017 is shown below:

From the center of mass, it is also necessary to calculate the relative distance of the thrusters to the center of mass, as well as the positions of the LEDs relative to the center of mass. A script has been prepared and it located here. The script will print the following information: