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About MTBs

Magnetic Torquer Bars (MTBs), which are also known as Torque Rods or Magnetic Torque Rods, provide a highly reliable, jitter-free method of producing torque to control the attitude of spacecraft. They have the following advantages:

• MTBs have significantly lower power-mass products than air coils.
• They can be used indefinitely, without the high-mass expendables of thrusters or the speed limitations of reaction wheels.
• In low earth orbit, mid-sized MTBs produce torques comparable to small reaction wheels.

MTBs can be used on their own to control spacecraft attitude, but often they are used to de-saturate onboard momentum storage devices. MTBs are also used to eliminate tumbling when a spacecraft is first deployed.

MTB Operation Each MTB consists of a magnetically soft metal core wrapped with multiple layers of copper wire. In this longitudinal view, crosses represent current moving through the wire into the page, and dots represent current moving out of the page. The magnetic field produced is represented by curvy arrows. image credit: Geek 3

General design

Each MTB consists of a magnetically soft metal core wrapped with multiple layers of copper wire. Current passing through the wire generates an applied field that magnetizes the core. The moment in the core increases until the demagnetizing field generated by the core cancels the applied field, making the magnetic moment linearly proportional to the current until the core starts to saturate.

Magnetic properties of the core material can cause non-ideal behavior including non-linearity at high moments, hysteresis, and a residual moment with zero applied current. We use a superior core material and proper annealing to minimize these effects.

Cayuga Astronautics MTBs

Cayuga Astronautics has the largest selection of standard MTBs. Our MTBs range in size from less than 1 Am2 to 1500 Am2 and are available in four standard series.

• Long (L)-Series MTBs: Are bi-filar wound and have the lowest mass and power
• Short (S)-Series MTBs: Are bi-filar wound and are compact, light and have lower residual moments.
• Mono-filar (M)-Series MTBs are the shortest MTBs on the market.
• Bi-filar (B)-Series MTBs are the like the M-Series MTBs but have redundant windings and use more power for a given moment.

L and S Series MTBs
Bottom 6: End support “L” and “S” series MTBs with 2 to 15 Am2 of magnetic moment.
Top 3: “L” and “S” series MTBs with 30 to 200 Am2 of moment and potted mounting block. The 3 MTBs mounted on Aluminum shipping plates have been delivered to various customers for flight. The black MTB has the optional Z307 conductive paint.
(6 and 12 inch rulers are included for scale)
M series MTBs
Bottom 6: M series MTBs with conductive tape.
Center 8: Standard M series MTBs,
Top 3: Standard M series MTBs with optional Z307 conductive paint.
(12 inch ruler included for scale)

Our extensive product lines allow you to choose an MTB that best meets the moment and power requirements of your mission without the weight and size penalty of excess capacity. The simple, standardized design of our MTBs minimizes cost and manufacturing time while significantly improving robustness.

MTBs can also be custom-designed to accommodate different mass, size, power and bus voltage requirements. Give us a call for more information.