The Spacemen were all ex-space program trainees.  They had washed out of training and later stole meteor samples which John Jameson had collected on a space mission.  When they unsealed the containers, the meteors broke open and expelled an alien gas.  These fumes caused the quartet to develop superpowers.   
 
The group made a public appearance and claimed to be astronauts from a secret government task force.  Stating they had deliberately exposed themselves to a cosmic ray storm (similiar to the Fantastic Four and U-Foes), the Spacemen went to New York.  Acting as heroes on a mission to apprehend Spider-Man, their conflicts with the hero were actually covers in which they would rob banks and other venues and place the blame on Spider-Man for the robberies.  
 
J. Jonah Jameson, ignorant of the truth, heaped praise upon the Spacemen in an article printed in the Daily Bugle newspaper while criminalizing Spider-Man.  John Jameson was skeptical, especially since he was looking to recruit Spider-Man in the astronaut program himself.  Luckily Spider-Man developed a device which tapped into the Spacemen's radio signals so he could learn the truth.  He publicly exposed the Spacemen at a parade held in their honor and defeated them in full view of city authorities.