This answer links to https://history.nasa.gov/spacesuits.pdf which shows the image below. (fyi Wikipedia's STS-61 is not to be confused with STS-61A, STS-61B or STS-61C, see answers to Why so many STS-61's?).

STS-61B saw the Experimental Assembly of Structures in EVA and the Assembly Concept for Construction of Erectable Space Structures, or EASE/ACCESS. The results section of that article says:

Applied moments of inertia during EVA were found to be on the order of 2.0 newton meters (1.5 lbf⋅ft). In neutral buoyancy simulation, the applied moments of inertia were around five times greater than those during EVA.1 Assembly time during EVA was around 20% less than in neutral buoyancy simulation. The learning curve was on the order of 78%, and was unaffected by the strength, coordination, or size of the astronaut, or the fit of the space suit.[5] In both environments, moments of inertia were applied as short impulses, interspersed by several seconds of coasting.

While torque can have units of lbf⋅ft, the corresponding units of moment of inertia would be lbf ft s².

So in the context of STS-61B's EASE/ACCESS, are "applied moments of inertia" really "astronaut-applied torques"? Or are they actually moments of inertia?

enter image description here

Astronaut Sherwood C. Spring wears the EMU while checking joints on a tower extending from the Space Shuttle Atlantis cargo bay during mission STS 61 -B. He is standing on the end of the arm of the remote manipulator system connected to the space shuttle.


1 Answer 1


It appears that the author of the Wikipedia article made an error.

The source document, an abstract of the paper Moments Applied in the Manual Assembly of Space Structures: EASE Biomechanics Results From STS-61B simply calls them "moments", not "moments of inertia". Calling them "moments" is OK and basically equivalent to "torques".

Moments applied in these manual handling tasks were calculated on the basis of the reconstructed movements taking into account effects of inertia, drag and virtual mass. Applied moments of 2.0 Nm were typical for beam rotations in EVA. Corresponding applied moments in NBS were typically up to five times greater. Moments were applied as impulses separated by several seconds of coasting in both EVA and NBS.


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