In the past 20 years, cube satellites have played an important role in the field of aerospace technology exploration and research. Operation of CubeSats in orbit requires an Attitude Determination and Control System (ADCS). The Magnetorquer integrated into the PCB is one of the accurate and efficient ADCS, which is most suitable for providing torque to satellites in low earth orbit (LEO) to control the direction of the satellite.
What are Cubesats?
CubeSats, also known as Cube Satellites, are small satellites are small satellites typically used to launch small experimental payloads into orbit. Due to its small size, low cost and low power consumption, it is used in many fields, including aerospace science experiments, ground environment monitoring, GPS, etc.
They are typically categorized by the number of units that they are comprised of, where one unit (1U) is a (10 x 10 x 10) cm3 module. Commonly, CubeSats are 1U, 2U, 3U, or even 6U, and one of the common challenges in operating these satellites is controlling the CubeSat’s attitude, or its orientation in space. This is done using some sort of attitude determination and control system (ADCS).
What is Magnetorquer?
A magnetorquer is a relatively cheap attitude control system ADCS that applies an external torque on a CubeSat. We sometimes just call them “torques”, and they come in two categories, “cylindrical torquer rods” and “compact magnetic torque coils”. Both of these work based on the solenoid’s law and Ampere’s law, but the former contains ferrite material to enhance its magnetic dipole moment.
Since the torque source is based on the Lorentz force, there is an uncontrollable axis parallel to the geomagnetic flux density vector. Additionally, magnetic torquers can only function in environments that contain a sufficiently localized magnetic field, such as low-Earth orbit (LEO).
The magnetorquer also requires local magnetic flux density vector information for its attitude control logic. A straightforward way to obtain such data is to use a magnetometer. Propagation using the IGRF model also works. Torque-based control is probably the simplest approach to active attitude control. But its control accuracy is only about 1~5 degrees.
Magnetorquer Block Diagram
Types of Magnetorquer
Cylindrical Magnetorquer Rod
A cylindrical magnetorquer consists of a cylindrical coil of wire and a permanent magnet that is mounted inside the spacecraft.
When an electrical current is passed through the coil, a magnetic field is generated that interacts with the magnetic field of the permanent magnet. This interaction produces a torque that can be used to rotate the spacecraft in a desired direction.
One of the advantages of a cylindrical magnetorquer is its simplicity and reliability. It can be easily integrated into the spacecraft’s design and requires minimal maintenance. Additionally, it is a low-power device, which is important for spacecraft that have limited power resources.
The cylindrical magnetic rod is the best available magnetorquer for the generation of higher torques and consequently better attitude controls. The magnetic rod is also designed which completely fits in the dimensions of a CubeSat.
Compact Magnetorquer Coil
The coil of compact magnetorquer is typically made of a thin wire wrapped around a core, which is usually made of a magnetic material like iron or ferrite. When an electrical current passes through the wire, it creates a magnetic field that interacts with the Earth’s magnetic field, causing the spacecraft to rotate.
The compact design of the magnetorquer coil is important because space is limited on most spacecraft and satellites. Therefore, a smaller device that can still produce a sufficient magnetic field is highly desirable. Additionally, a compact magnetorquer coil can reduce the weight and cost of the overall system.
There are several companies that produce compact magnetorquer coils, including CubeSatShop, Sinclair Interplanetary, and Blue Canyon Technologies. These companies offer a range of sizes and designs to meet the specific needs of different spacecraft and satellite missions.
Magnetorquer PCB Solutions
There’re few vendors sell magnetorquer PCB board for Cubesat on the market, one of them is ISISPACE.
If you would like to do DIY design on the magnetorquer board, we’re here to help you!
