Editing Apollo 1 (section)

==== Hatch design ====
[[File:AS-204 - hatch.jpg|thumb|The Block{{nbsp}}I hatch, as used on Apollo{{nbsp}}1, consisted of two pieces, and required pressure inside the cabin to be no greater than atmospheric in order to open. A third outer layer, the boost protective hatch cover, is not shown.]]

The inner hatch cover used a [[plug door]] design, sealed by higher pressure inside the cabin than outside. The normal pressure level used for launch ({{convert|2|psi|kPa|abbr=on}} above ambient) created sufficient force to prevent removing the cover until the excess pressure was vented. Emergency procedure called for Grissom to open the cabin vent valve first, allowing White to remove the cover,<ref name="SP4029" /> but Grissom was prevented from doing this because the valve was located to the left, behind the initial wall of flames. Also, while the system could easily vent the normal pressure, its flow capacity was utterly incapable of handling the rapid increase to {{convert|29|psi|kPa|abbr=on}} caused by the intense heat of the fire.<ref name="aibreport" />{{Reference page|page=5-3}}

North American had originally suggested the hatch open outward and use [[explosive bolt]]s 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 ''[[Mercury-Redstone 4#Liberty Bell 7|Liberty Bell 7]]'' flight, so the [[Lyndon B. Johnson Space Center|Manned Spacecraft Center]] designers rejected the explosive design in favor of a mechanically operated one for the Gemini and Apollo programs.<ref name= "chariots9-2">{{Cite book |last1=Brooks |first1=Courtney G. |url=https://history.nasa.gov/SP-4205/cover.html |title=Chariots for Apollo: A History of Manned Lunar Spacecraft |last2=Grimwood |first2=James M. |last3=Swenson |first3=Loyd S. Jr. |publisher=Scientific and Technical Information Branch, NASA |others=Foreword by [[Samuel C. Phillips]] |year=1979 |isbn=0-486-46756-2 |series=NASA History Series |location=Washington, DC |chapter=Stalked by the Spectre |oclc=4664449 |id=NASA SP-4205 |access-date= January 6, 2016 |chapter-url=http://www.hq.nasa.gov/office/pao/History/SP-4205/ch9-2.html}}</ref> 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 [[Deke Slayton|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.<ref name = spaceport/>