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Advantages of our MTBs

Superior moment to mass ratio

Our MTBs are optimized to minimize effective mass, a quantity that combines weight and power into one value. By minimizing effective mass and adding other unique design features, we produce power-efficient MTBs with a ratio of mass to magnetic moments that is significantly lower than that of our competitors. top of page


Lower power

Our long MTBs generally take less power than our competition (Graphs 3 and 4). This savings frees up power for other systems, and allows you to minimize the size of the power system. top of page

Smaller size

Our short MTBs are generally shorter than our competition (Graphs 5 and 6). A shorter MTB takes up less space on the satellite and can save mass by reducing the size of the spacecraft support structure. top of page

Test data

Our Long and Short MTBs have a residual moment less than 1.0% and 0.5% respectively. Non-linearity is less than 4% at the linear moment and 30% at the saturated moment. All of our MTBs have redundant coils. Magnetic moment test data for a 30 Am2 MTB is shown in Graphs 7 & 8.

Data provided assumes power is only applied to one coil at a time. However, you have the option to wire the two coils in series or in parallel. This cuts the power consumption in half and allows the MTB to be used with a different bus voltage. top of page

In graphs 7 and 8 magnetic moment was measured using the traditional method, in which magnetic moment is measured indirectly based on the magnetic field produced by the MTB and a simplified model of the distribution of the moment. We have also developed an alternate method that directly measures the magnetic moment using the equation:

Moment = (Rotational Inertia / Field Strength in plane parallel to ground) * (2πf)2

The rotational inertia is calculated from mass models and can be adjusted using the ratio between the measured mass and the calculated mass for better accuracy. The Earth’s magnetic field strength and frequency are measured parameters.

Although the alternated method is too time consuming to use exclusively, it is an excellent way to check the traditional performance test results. Figure 9 shows the test equipment used for both test methods and compares the results with the predicted magnetic moment versus current curve. As can be seen, there is excellent agreement between all three curves.

Figure 9 Magnetic moment measurements

magnetic moment measurements

left: MTB-15S-5V being tested by the alternate "torsional pendulum" method. middle: MTB-200L-28V being tested by the traditional method. right: graph comparing data taken using both methods to the predicted moment. top of page

Random vibe testing

Six MTBs (MTB-200L-28V, 200S-28V, 30P-28V, 15L-5V, 15S-5V, 2S-5V) were subjected to random vibration testing at 25 g rms with a peak of 0.5 g2/Hz between 50 and 800 Hz for 3 minutes per axis. Modal surveys confirmed that all primary vibration frequencies were greater than 100 Hz. No mechanical damage occurred, and magnetic performance was unaffected. All of our other MTBs are designed to withstand similar vibrations. top of page

Figure 10 Random vibe testing

Random Vibe Test