Murderer's Base

They played a ghastly game on that lonely asteroid. Killer and victim-to-be danced and feinted between space-beacon and ship. Only the stars knew the winner.
He did not remember exactly when the idea of killing Hervey occurred to him. Probably, though, it had been that day at Hermes Station, when the wrench had slipped from his grasp as he worked on the tower; it had drifted lightly down and struck Hervey a glancing blow on the helmet. They had laughed about it, and Hervey had said, If we were under grav conditions, Joe, that probably would have conked me.
It had been funny then, but it wasn't funny any more. Joe Berne watched Hervey all of the time now, waiting. There had to be an opportunity, some day, some time. Accidents weren't frequent on the beacon service-run, but they did happen. And it had to look like an accident.
Berne knew that it wasn't going to be easy. Sam Hervey was a careful, cautious man. He was a man who checked his equipment before he went through the air lock, who nursed his jets like they were infants, a man who had every intention of living a long life in a dirty business where the careless died young. Berne had been glad when Space Service had teamed him with Hervey; Personnel had clearly hoped that a tour of duty with the veteran Hervey would supply the balance and judgment that the younger man apparently lacked. It had worked out ... Berne, Hervey and battered old Service Ship 114 had hung up an enviable record of efficiency and safety. And after their leave, Hervey had asked to work with Berne on another tour.
Hervey was good at this damned, dull, hateful task. Not many men were willing to spend nine months out of the year blasting from asteroid to asteroid, checking and servicing and reporting on the great beacons that beamed the dangerous spaceway from Mars to the moons of Jupiter. It was always tedious, often backbreaking and sometimes dangerous, and even Sam Hervey had said that he would be glad to be out of it.