Gearing Satellites Up for Space

Space is a popular frontier these days. A record number of 2781 satellites were deployed in 2023, according to the Satellite Industry Association’s latest report, and by the end of the year there were a total of 9691 satellites in Earth’s orbit. Allied Market Research expects the market to grow 8.1%, amounting to a market size of $615.7 billion by 2032.

Engineering satellites and other space-bound systems entails making Earth-bound technology appropriate for space, Jeff Randall, maxon’s business development manager for aerospace, tells Design News. While environmental conditions and operating requirements guide most design and engineering decisions, so does the trip into space. “Anything going off-world has to ride on a rocket—so you have to figure out how it will survive it,” he says. 

maxon can take a common drive system and modify it for space, the Moon, and even Mars. “Each environment poses challenges, but believe it or not, Mars is the easiest,” he says. “We can leverage our wide manufacturing experience and industrial product base and make the necessary product modifications and adjustments for space.”

To help satellite innovators reach space, maxon opened its SpaceLab in 2020 and now supports commercial applications and science missions. The company offers brushless motors, brushed motors, gearheads, sensors, and brakes that can be modified for each mission.

Let’s take a journey into drive system design considerations for space and dream up some possibilities.

What Conditions Must Satellites and Their Drive Systems Survive in Space?

Satellites will see extreme conditions. Here are the likely ones and their challenges:

Vacuum. In space, motors must be able to operate in a vacuum, says Randall. For drive systems that utilize lubrication, this environment of near perfect vacuum means that lubrication “boils off,” he says. Engineers, therefore, are challenged to find a way to keep systems lubricated.

Radiation. “We are protected from radiation by the Earth’s atmosphere, but not in space,” Randall says. “Hall effect sensors and other components can be impacted by radiation from the Sun. We can select sensors that are shielded to protect them.”

Extreme temperatures. “Surfaces are exposed to wide temperature variations, from -70 degrees C to very high temperatures,” Randall says. Such extremes make material selection challenging, particularly for complex systems such as motors, which he says can contain up to 60 individual parts with varying materials. “If materials expand and contract at different rates, we could see different failure modes,” he said. For instance, “a metal shaft cools faster than a plastic one. We work to find materials with similar rates of expansion.

“Many factors go into material selection,” Randall continues. “We don’t source exotic materials but instead source different grades of established materials that are appropriate for space environments.” Choosing established materials that have a history of successful use in motors, gears, and brakes may give design engineers confidence in their selection. Randall does point out the need to keep an eye out for new materials, “such as bulk metallic glass for gearing, which could be interesting for space.”

Heat dissipation. In space, there is no convection (movement of air), only conduction (transfer of heat) and radiant heat transfer. Engineers will need to reduce the amount of power used to reduce heat risks.

Extreme shock and vibration. As mentioned earlier, satellites that travel to space and then “land” in their designated orbits may see quite a ride. “You must reinforce moving parts such as shafts and bearings so they don’t get displaced,” Randall explains. Special brushes are also chosen for brushed motors, he adds. 

maxon’s EC frameless motors are BLDC motor kits. Rotor and stator are delivered separately, without bearings and motor shaft, and connected only during assembly. The flat design, the high torques, and plenty of space for cable glands allow a high level of integration into applications. MAXON

Heightened Quality Standards

Because of such extreme conditions in space as well as the remoteness of system operation, the bar may be set much higher for components and assemblies. After all, “if a product fails in space, you can’t fix it,” Randall says. 

Still, there may be tradeoffs to make. “You are walking a fine line between important quality aspects and cost,” he says.

Space-bound components and assemblies are often inspected to higher standards. For instance, a soldered joint that is inspected to IPC 610 Class 2 for use on Earth may be inspected to IPC 610 Class 3 for use in space, he explains.

Quality levels may also depend upon customer requirements. maxon follows its own inspection standards for materials, printed circuit boards, and other incoming components and tightly controls and monitors its own manufacturing processes with regular in-process checks of subcomponents (such as rotors and stators) as well as final assemblies. The company can then add additional quality services as requested, such as specific reporting.

“Customers may request specific accepted test reports (ATRs) based on specific accepted test processes (ATPs),” he says.

Robust engineering, combined with the globally patented ironless winding, makes the maxon DCX range a highly dynamic and responsive motor for a wide range of application including demanding space applications. MAXON

Redundancy

Another design requirement often requested for space is redundancy. “Some want it, some don’t,” Randall says.

Widely employed options include engineering two motors with the same function or employing two motors coupled together in one gearbox. 

maxon has also introduced a new motor that is like two motors in one—a motor with a single body and two independently wound stators. “It features one rotor with two independent sets of copper windings connected in a way that serves as two independent motors,” he explains.

The stator has been a likely point of failure in motors, he adds. “In a brushless motor, the stator contains all the copper and that is where you generate a lot of heat,” he says. “This is also where the PCB is located and there are a lot of soldered joints. Even on Earth, when people run a lot of power in their systems, they burn their motors.”

Given the redundancy offered by a motor with two stators, Randall says “this may be well-received by the commercial satellite market.” 

Minimizing Energy Consumption

Given the risks that overheating presents, “it’s a good idea to minimize power use, because when you use more power, you create more heat,” Randall says. “Everyone wants to minimize the amount of energy consumed.”

To optimize power use, engineers should stay within the limits of specified current use. “If you have a given voltage, choose the appropriate motor to only use enough current to get the job done, while also considering your torque needs.” 

Randall says that maxon can help customers select the right drive systems to achieve their goals. 

maxon’s 4-pole power motor offers high performance per volume and weight unit, high quality, precision, cogging-free motion, and an unprecedented service life. MAXON

What’s on the Horizon?

Randall recently attended the Small Satellite Conference in August 2024 and he said that a popular discussion point was the use of reaction wheels, which are devices that can rotate and stabilize small satellites. "This uses the gyro effect to stabilize the satellite when outside forces are acting on it trying to move it in a way the use does not want it to go. The reaction wheels will keep the satellites stable (to a point)."