"Escape" velocity.
D000060:Accidents, Aviation; D018480:Astronauts; D004190:Disasters; D006801:Humans; D016272:Occupational Health; D011482:Protective Devices; D012449:Safety; D013026:Space Flight / Q000295:instrumentation / Q000592:standards*; D018531:Spacecraft / Q000295:instrumentation*; D014481:United States; D018557:United States National Aeronautics and Space Administration / Q000592:standards