If all goes as planned, NASA will launch its Sample Retrieval Lander (SRL) Mars mission from Florida’s Space Coast in June 2028, the start of its latest, and greatest, mission to Mars. By sometime in the early 2030s, the SRL mission will have succeeded in traveling to Mars; gathering samples already collected by the Perseverance Rover; launching them into Mars orbit; and capturing and returning them safely to Earth. For NASA’s scientists, the SRL mission is the culmination of a decades-long series of Mars explorations designed to find evidence of life outside of Earth or, at the very least, provide important insights into the origin of life here on Earth.

The mission is among the most ambitious, and risky, ever devised by humankind. After a two-year journey and landing on Mars, the SRL will rendezvous with NASA’s Perseverance Rover, which landed on Mars in 2021 and is busy now exploring an ancient river delta and collecting samples that could show the potential for ancient life. These samples will either be collected by the Sample Retrieval Lander via Sample Transfer Arm or, if Perseverance can’t make the rendezvous point, retrieved by two Sample Recovery Helicopters. Sample tubes then will be loaded into an Orbiting Sample container atop the Mars Ascent Vehicle (MAV) carried by the SRL. The MAV then is launched into orbit around Mars, where it’s met by yet another vehicle: the Earth Return Orbiter (ERO). The Orbiting Sample container is transferred from MAV to ERO, which then delivers the samples to Earth.

Southern Gear puts all the resources for the machining of gear blanks, gear cutting, gear grinding, assembly and inspection under one roof—all close to the Space Coast.

Just a few hours south of where this mission will launch in 2028, on the factory floors of Miami-based Southern Gear & Machine, work is underway to help make this mission a success. Southern Gear is playing a small but important role, by helping to design, develop, and perfect the critically important gears and shafts used for the actuation of the legs and Sample Transfer Arm on the SRL. This vehicle must be both lightweight enough to get to Mars, and robust and reliable enough to withstand the rigors of space, a surface landing, successful transfer of the samples, and then launch the MAV and its precious cargo back into orbit. A lot is riding on the performance of these gears, says Southern Gear Engineering manager Sebastian Fajardo. “The project has unfolded over many months, starting in April 2023,” recalls Fajardo. “We were challenged by our customer to produce a series of high precision spur gears and internal splines, which sounds simple enough until you factor in the very thin walls required for weight savings, and the need to hold exceptionally tight tolerances to help ensure the highest levels of repeatability.”

Despite these challenges, Southern Gear’s President Karen Malin says her company was eager to take on the work and go ‘above and beyond’. “We have all the necessary resources in-house,” she says, “And the know-how derived from our long-time aerospace and defense work to find ways to make parts like these more easily manufacturable.”

Southern Gear streamlines production from engineering through final inspection—making it faster and more economical for prototype development of gears.

The first parts produced were a drive gear, an idler gear, and an output gear—each a combination of straight spur gears and internal splines. The internal spline in particular was a challenge, with a design that required Southern Gear’s engineering team to devise ways to make it more manufacturable. Every part was machined complete, requiring a combination of operations that included turning, external gear hobbing, internal spline shaping, and milling. Of special note was the output gear. With its very thin walls, heat treat distortion posed a significant challenge, requiring Southern Gear to utilize a non-conventional approach in order to compensate for, and minimize, heat treat distortion and allow for the machining of the part in the annealed state.

Southern Gear adheres to stringent AS9100 D, ISO 9001:2015 certified quality systems.

With the successful production of the first parts, Southern Gear was asked to produce two more challenging parts for this same program: a spline shaft assembly and its mating part. Both of these parts initially had some features that were not easily manufacturable but after a consultation with the customer, Southern Gear was able to deliver many innovative design alternatives that would allow for the production of both parts much more quickly and efficiently. The shaft was particularly complex, with an acme thread with tapped holes for helical inserts and a spline at the end. It also required that tight tolerances be held in features that wouldn’t normally require such accuracies, such as undercuts. Even the nut was complex, with an internal and external spline, an internal acme thread, and tapped holes on the side which needed helical inserts, which Southern Gear assembled.

Southern Gear’s products run the gear gamut: fine, medium, coarse pitch; spur, helical and face gears, shafts, splines, sprockets, worms, straight bevel—and now, gears for Mars exploration.

Upon successful completion of this second phase, Southern Gear was tasked with producing three more components for the SRL leg assembly: an upper hard stop, a lower hard stop, and a hard stop cap. The upper hard stop is a thin-walled external spline with internal features that require extremely precise milling. The lower hard stop and the stop cap had thin walls with an internal spline and a cam-like external feature that required very fine milling cuts to achieve the surface finish requirements. To produce this last batch of parts, Malin says the company pulled out all stops, to meet the customer’s aggressive delivery schedule—and to help keep the Mars mission on track.

southerngear.com