 North American had originally suggested the hatch open outward and use explosive bolts to blow the hatch in case of emergency , as had been done in Project Mercury . NASA did not agree , arguing the hatch could accidentally open , as it had on Grissom 's Liberty Bell 7 flight , so the Manned Spacecraft Center designers rejected the explosive design in favor of a mechanically operated one for the Gemini and Apollo programs . Before the fire , the Apollo astronauts had recommended changing the design to an outward @-@ opening hatch , and this was already slated for inclusion in the Block II Command Module design . According to Donald K. Slayton 's testimony before the House investigation of the accident , this was based on ease of exit for spacewalks and at the end of flight , rather than for emergency exit . 
