Load cells and NASA: a match made in heaven
There are some jobs involving load cells that make us, frankly, green with envy, and often it’s NASA projects that tops our ‘envy-list!’
Take a walk NASA style
The Active Response Gravity Offload System (ARGOS) is a spacewalk simulator developed by NASA to train astronauts for a variety of missions in a variety of gravities. ARGOS is essentially a crane that lifts the trainee into a simulated state of weightlessness. Strain and force sensors ensure that the force experienced is maintained whatever movement or action the trainee makes.
The system provides motion in all three axes from computer-controlled electric motors. A load cell in the main lifting cable instructs these motors to raise and lower, to maintain a constant force. It’s fast too; it can shift 300 pounds at a dizzying 10 feet per second.
ARGOS is designed to simulate a variety of gravitational systems, including:
- Zero gravity as experienced aboard the International Space Station
- Lunar gravity
- Gravity on the surface of Mars
- “Any other celestial destination” as NASA says!
Keeping fit in space
Long periods in zero gravity can reduce muscle mass by up to 15%, and some of that loss can be permanent. Astronauts on the ISS use the Advanced Resistive Exercise Device (ARED) to maintain their muscle strength and mass (4). First used back in January 2009, the ARED also helps crew members build their strength for physically demanding space walks, and prepare their bodies for re-entry, etc. And it’s packed with load cells!
The Exercise Platform Subassembly provides the surface for exercise, It contains two force plates, each with four load cells underneath to measure the reactive loads. The lift bar struts have two load cells installed, with two more in the arm base assembly yo measure reactive loads during exercises involving a pulley cable.
Rocket man testing
If you’ve ever wondered how NASA measures the thrust of rockets that produce over a million pounds of thrust, yes, they use load cells. As a NASA blog explains:
“Actual load cells used for rocket engines can take different forms … Any way that you can get an applied load to result in a slight, measureable stretching of metal (while obviously avoiding yielding or buckling) is a valid load cell design.”
The set-up is remarkably simple. A flexure ensures the load is directed in the correct axis onto a free-floating platform, with three or four load cells. The trick is to ensure the test structure can absorb the thrust without distorting, and apply tares to compensate for set-up elements such as fuel lines that might absorb some of the thrust.
Testing the Orion crew module
The NASA Engineering & Safety Center (NESC) is often engaged in testing elements manufactured under contract, including the full-scale Composite Crew Module for the Orion mission. Since most of the fittings were on the underside of the capsule, it was mounted in the test frame upside down. This actually helped testing considerably, as a NASA blog explains:
“Point loads to fittings were applied using an innovative technique to route load from the hydraulic actuators to the fittings through a low-stretch strap (less than 1% extension). …. To account for possible friction, two load cells were used to monitor the load at each end of the strap.”
Stellar load cells from The Load cell Shop
Whatever your project, our load cells can be the star of your measurement, testing or training rigs. Call us with your requirements, and you’ll be over the moon with our expert design, excellent quality of build – and down to earth prices. Or take a Peake at our online load cell shop. (OK, we’ll stop the space puns now…)
