What did the astronauts fail to do which would have saved them from falling haphazardly through space in "Kaleidoscope"?

"Kaleidoscope" is the second story in Ray Bradbury's science fiction anthology The Illustrated Man. The story narrates the fate of a group of men who narrowly escape an explosion on their rocket ship but end up abandoned, floating away from each other in space. In the opening lines of the story, the men are described as "wriggling silverfish" who are "scattered into a dark sea," which emphasizes the desperate, hopeless situation they face.
The spacemen had some time to enact their survival protocols, but their rocket explodes before they can finish them. Bradbury writes:

They were wearing their sealed-tight space suits with the glass tubes over their pale faces, but they hadn't had time to lock their force units. With them, they could be small lifeboats in space, saving themselves, saving others . . . But without the force units snapped to their shoulders, they were meteors, senseless, each going to a separate and irrevocable fate.

Although the men can breathe and survive the frigid temperatures of space, they have no means of escape because they hadn't locked their "force units." The details of this technology are not provided by Bradbury, but it is evident that it would have been a lifeline for the doomed men. Without the life-saving device, the group of men are forced into a lengthy wait for their deaths.
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