Show Brakes Glenn Has Ace In Hole By ALTON BLAKESLEE Associated Press Science Writer CAPE FLA America's Astronaut is counting on space rocket brakes to bring him safely But suppose the brakes ASTRONAUT John H. could keep on orbiting for a week or But his capsule will carry only enough oxygen for about 24 hours of Yet Glenn would still have a little known ace-in-space card to play in a tricky maneuver requiring the skill of the expert pilot he say space agency IT CALLS for shooting out jets of steam to act as little in a series of repeated at exactly the precise i His capsule has 18 nozzles out of which he can squirt jets of steam to control the attitude j or position of his spaceship along the path of its |