Beam me up Scotty: load cells in space
Following the excitement of the safe touchdown of the NASA Mars rover, there’s a new kid on the planet in the form of the Chinese six-wheeled Zhurong rover. This rover will explore the Martian plain of Utopia Planitia for signs of water ice, and take samples of the planet surface. What we love most about this rover is the way it simply drove off the top of its lander down two ramps down to the surface. (Take a look here: https://www.space.com/china-mars-rover-zhurong-rolls-on-martian-surface)
Needless to say, we can’t find any technical details of the Chinese rover online, but there are bound to be load cells involved in various parts of the whole mission.
3129 sols and counting
Meanwhile on another part of Mars, the 2012 model rover Curiosity is trundling around the Gale Crater. The rover has been on Mars since August 5th 2012, clocking up over 3100 Martian days (known as sols) of travel. (A Martian sol is on average 24 hours and 40 minutes.)
According to the weekly report from the Curiosity team (dated 24th May 2021), the team hoped to see “some new bedrock in our workspace” but due to a technical fault in closing the MAHLI cover, they ended up doing “dust devil surveys”. As on-duty Long Term Planner (LTP) Lauren Edgar explains, the camera images show “some tantalizing stratigraphy ahead”.
The latest mock-up images show the Curiosity dirty with red dust from years in the planet surface, but with under 22 miles on the clock, it is definitely a low milage vehicle! We love the fact that you can track Curiosity’s progress online.
Load cells on Curiosity
As reported by Futek, Curiosity’s robotic drilling arm includes a “flight qualified cryogenic dual-bridge donut load cell” to monitor the forces of the drill bit. A diagram on the website shows the load cell sitting below the DTM actuator and the gimbal assembly.
“This specific sensor sits within the drilling mechanism on the rover. It is responsible to measure the forces of the drill bit at a high level of accuracy and resolution that a current controlled motor drive system cannot achieve. The inclusion of a dual-bridge was a necessity to allow redundancy in the system, which reduces risk of the system becoming inoperable in the extreme conditions.”
Drilling activity has taken place at various stages of the rover’s exploration, including at the “Mary Anning” drill site, named after the English paleontologist who unearthed fossils of extinct marine reptiles in the early 1800s.
Load cells have lift-off
Load cells are integral to the design, assembly, testing and control of almost every stage of what Strainsert call “spacecraft hardware’. The company describe how their load cells were used in the Curiosity mission to:
“Determine forces at many interfacing areas, where the various components come together forming a larger assembly (and) many load cells are designed to be permanently embedded in the system to both carry and measure the force for the life of the product.”
The company designed and manufactured no less than 42 custom force sensors on the Curiosity rover, involved in key stages such as the major spacecraft separations, and retention of the Mobility (wheels), High Gain Antenna, Camera Mast, and the Robotic Arm.
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