Editing Project Mercury (section)

===Pilot accommodations===
[[File:GPN-2000-001027.jpg|thumb|upright|[[John Glenn]] wearing his Mercury space suit]]

The astronaut lay in a sitting position with his back to the heat shield, which was found to be the position that best enabled a human to withstand the high [[g-force]]s of launch and reentry. A fiberglass seat was custom-molded from each astronaut's space-suited body for maximum support. Near his left hand was a manual abort handle to activate the launch escape system if necessary prior to or during liftoff, in case the automatic trigger failed.{{sfn|Catchpole|2001|p=142}}

To supplement the onboard environmental control system, he wore a [[pressure suit]] with its own [[oxygen]] supply, which would also cool him.{{sfn|Catchpole|2001|p=191}} A cabin atmosphere of pure oxygen at a low pressure of {{cvt|5.5|psi|disp=or}} (equivalent to an altitude of {{convert|24800|ft|disp=or}}) was chosen, rather than one with the same composition as air ([[nitrogen]]/oxygen) at sea level.{{sfn|Gatland|1976|p=264}} This was easier to control,{{sfn|Catchpole|2001|p=410}} avoided the risk of [[decompression sickness]] ("the bends"),{{sfn|Giblin|1998|p=}}{{refn|group=n|The decision to eliminate the use of any gas but oxygen was crystalized when a serious accident occurred on April 21, 1960, in which McDonnell Aircraft test pilot G.B. North passed out and was seriously injured when testing a Mercury cabin/spacesuit atmosphere system in a vacuum chamber. The problem was found to be nitrogen-rich (oxygen-poor) air leaking from the cabin into his spacesuit feed.{{sfn|Giblin|1998|p=}}}} and also saved on spacecraft weight. Fires (which never occurred during the course of Project Mercury) would have to be extinguished by emptying the cabin of oxygen.{{sfn|Catchpole|2001|p=139}} In such case, or failure of the cabin pressure for any reason, the astronaut could make an emergency return to Earth, relying on his suit for survival.{{sfn|Alexander & al.|1966|pp=48–49}}{{sfn|Catchpole|2001|p=139}} The astronauts normally flew with their [[visor]] up, which meant that the suit was not inflated.{{sfn|Catchpole|2001|p=139}} With the visor down and the suit inflated, the astronaut could only reach the side and bottom panels, where vital buttons and handles were placed.{{sfn|Alexander & al.|1966|p=246}}

The astronaut also wore [[electrode]]s on his chest to record his [[heart rhythm]], a cuff that could take his blood pressure, and a [[Medical thermometer|rectal thermometer]] to record his temperature (this was replaced by an oral thermometer on the last flight).{{sfn|Catchpole|2001|pp=191, 194}} Data from these was sent to the ground during the flight.{{sfn|Catchpole|2001|p=191}}{{refn|group=n|Pilot and spacecraft data sent automatically to the ground is called [[telemetry]].{{sfn|Alexander & al.|1966|p=313}}}} The astronaut normally drank water and ate food pellets.{{sfn|Catchpole|2001|pp=343–344}}{{refn|group=n|Moisture and urine was recycled into drinking water.{{sfn|Alexander & al.|1966|p=47}}}}

Despite the lessons learnt from the [[Lockheed U-2|U2]] program, which also utilized a pressure suit, initially no urine collection device was included for the Mercury astronauts. An inquiry on the subject was made in February 1961 by a student, but NASA responded by stating that "the first space man is not expected to have 'to go".{{sfn|Hollins|2013|p=}} The expected short flight times meant that this was overlooked, although after Alan Shepard had a launch delay of four hours, he was forced to urinate in his suit, short-circuiting some of the electrodes monitoring his vital signs. Gus Grissom wore two rubber pants on the second Mercury flight as a crude workaround. It would take until the third flight in February 1962 before a dedicated urine collection device was installed.<ref>{{cite web |url=https://abcnews.go.com/Technology/history-urinating-space/story?id=19641585 |title=The History of Urinating in Space |publisher=ABC |access-date=27 Dec 2023}}</ref>

Once in orbit, the spacecraft could be rotated in [[yaw, pitch, and roll]]: along its longitudinal axis (roll), left to right from the astronaut's point of view (yaw), and up or down (pitch).{{sfn|Alexander & al.|1966|p=98}} Movement was created by [[Rocket engine|rocket-propelled]] thrusters which used [[hydrogen peroxide]] as a fuel.{{sfn|Alexander & al.|1966|p=499}}{{sfn|Catchpole|2001|p=143}} For orientation, the pilot could look through the window in front of him or he could look at a screen connected to a [[periscope]] with a camera which could be turned 360°.{{sfn|Catchpole|2001|p=141}}

The Mercury astronauts had taken part in the development of their spacecraft, and insisted that manual control, and a window, be elements of its design.{{sfn|Catchpole|2001|pp=98–99}} As a result, spacecraft movement and other functions could be controlled three ways: remotely from the ground when passing over a ground station, automatically guided by onboard instruments, or manually by the astronaut, who could replace or override the two other methods. Experience validated the astronauts' insistence on manual controls. Without them, [[Gordon Cooper]]'s manual reentry during the last flight would not have been possible.{{sfn|Alexander & al.|1966|p=501}}

{{hidden begin|title={{center|Cutaways and interior of spacecraft}}|style=border:solid 1px #aaa;background:#F9F9F9;padding-left:10px;}}
;Spacecraft cutaway
<gallery mode="packed">
Mercury Spacecraft.png|Interior of spacecraft
Mercury-spacecraft-control.png|The three axes of rotation for the spacecraft: yaw, pitch and roll
Mercury-spacecraft-temperature-profile.png|Temperature profile for spacecraft in [[Fahrenheit]]
</gallery>

;Control panels and handle
<gallery mode="packed">
Control panels mercury atlas 6.png|The control panels of ''Friendship 7''.{{sfn|Unknown|1962|p=8}} The panels changed between flights, among others the periscope screen that dominates the center of these panels was dropped for the final flight together with the periscope itself.
Three-axis hand controller mercury project.jpg|3-axis handle for attitude control
</gallery>
{{clear}}
{{hidden end}}