Editing Project Mercury (section)

==Mission profile==
===Suborbital missions===
[[File:Mr3-flight-timeline-simple-2.png|thumb|upright=1.2|Profile. See timetable for explanation. Dashed line: region of weightlessness.]]

A Redstone rocket was used to boost the capsule for 2 minutes and 30 seconds to an altitude of {{convert|32|nmi|km}}; the capsule continued ascending on a ballistic curve after booster separation.{{sfn|Unknown|1961a|p=7}}{{sfn|Catchpole|2001|pp=208, 250}} The launch escape system was jettisoned at the same time. At the top of the curve, the spacecraft's retrorockets were fired for testing purposes; they were not necessary for reentry because orbital speed had not been attained. The spacecraft landed in the Atlantic Ocean.{{sfn|Catchpole|2001|pp=250, 308}} The suborbital mission took about 15 minutes, had an apogee altitude of {{convert|102|-|103|nmi|km|sp=us}}, and a downrange distance of {{convert|262|nmi|km|sp=us}}.{{sfn|Alexander & al.|1966|pp=640–641}}{{sfn|Catchpole|2001|p=475}} From the time of booster-spacecraft separation until reentry where air started to slow down the spacecraft, the pilot would experience weightlessness as shown on the image.{{refn|group=n|With the exception of the 20 seconds of retrofire during which the pilot would experience g-force.}} The recovery procedure would be the same as an orbital mission.[AS]

{| class="wikitable collapsible collapsed"
|-
!colspan="2" | Timetable (mm:ss)
|-
| style="text-align:right;"|0:00|| Launch
|-
| style="text-align:right;"| 2:22|| Launch vehicle cut-off and tower separation
|-
| style="text-align:right;"| 2:32|| Spacecraft separation
|-
| style="text-align:right;"| 2:37|| Turnaround
|-
| style="text-align:right;"| 5:14|| Retrofire
|-
| style="text-align:right;"| 6:14|| Retropack jettisoned
|-
| style="text-align:right;"| 7:48|| Reentry
|-
| style="text-align:right;"| 9:38|| Drogue deployed
|-
| style="text-align:right;"| 10:15|| Main chute deployed
|-
| style="text-align:right;"| 15:22|| Landing
|}

===Orbital missions===

[[File:Launch-complex-14.png|thumb|upright=1.2|Launch Complex 14 just before launch (service tower rolled aside). Preparations for launch were made in the blockhouse.]]

Preparations for a mission started a month in advance with the selection of the primary and back-up astronaut; they would practice together for the mission.{{sfn|Catchpole|2001|p=110}} For three days prior to launch, the astronaut went through a special diet to minimize his need for [[defecation|defecating]] during the flight.{{sfn|Catchpole|2001|p=278}} On the morning of the trip he typically ate a steak breakfast.{{sfn|Catchpole|2001|p=278}} After having sensors applied to his body and being dressed in the pressure suit, he started breathing pure oxygen to prepare him for the atmosphere of the spacecraft.{{sfn|Catchpole|2001|p=280}} He arrived at the launch pad, took the elevator up the launch tower and entered the spacecraft two hours before launch.{{sfn|Catchpole|2001|p=188}}{{refn|group=n|Inside the spacecraft the other astronauts had usually prepared a practical joke, such as a sign saying "No handball playing".{{sfn|Catchpole|2001|p=281}}}} Once the astronaut was secured inside, the hatch was bolted, the launch area evacuated and the mobile tower rolled back.{{sfn|Catchpole|2001|p=281}} After this, the launch vehicle was filled with liquid oxygen.{{sfn|Catchpole|2001|p=281}} The entire procedure of preparing for launch and launching the spacecraft followed a time table called the countdown. It started a day in advance with a pre-count, in which all systems of the launch vehicle and spacecraft were checked. After that followed a 15-hour hold, during which pyrotechnics were installed. Then came the main countdown which for orbital flights started 6½ hours before launch (T – 390 min), counted backwards to launch (T = 0) and then forward until orbital insertion (T + 5 min).{{sfn|Catchpole|2001|p=188}}{{refn|group=n|Countdown was controlled from the blockhouse at the Launch Complex until 2 min. before launch then it was transferred to Mission Control Center. The countdown of the last 10 sec. before launch would be given to the astronaut by one of the others and included on TV transmissions which had already started.{{sfn|Catchpole|2001|p=282}}}}

[[File:Vol-Atlas-Mercury.png|thumb|upright=0.9|Launch and reentry profiles: A-C: launch; D: orbital insertion; E-K: reentry and landing]]

On an orbital mission, the Atlas' rocket engines were ignited four seconds before lift-off. The launch vehicle was held to the ground by clamps and then released when sufficient thrust was built up at lift-off ('''A''').{{sfn|Catchpole|2001|pp=188, 242}} After 30 seconds of flight, the point of maximum [[dynamic pressure]] against the vehicle was reached, at which the astronaut felt heavy vibrations.{{sfn|Catchpole|2001|p=340}} After 2 minutes and 10 seconds, the two outboard booster engines shut down and were released with the aft skirt, leaving the center sustainer engine running ('''B''').{{sfn|Catchpole|2001|p=188}} At this point, the launch escape system was no longer needed, and was separated from the spacecraft by its jettison rocket ('''C''').{{sfn|Catchpole|2001|p=132}}{{refn|In the event of a launch abort before this point, the launch escape system would fire its main rocket for one second, pulling the spacecraft and astronaut away from the launch vehicle and a possible explosion.{{sfn|Catchpole|2001|p=179}} At this point, the spacecraft could be separated from the launch vehicle and land using its parachute.{{sfn|Catchpole|2001|p=180}}|group=n}} The space vehicle moved gradually to a horizontal attitude until, at an altitude of {{convert|87|nmi|km|sp=us}}, the sustainer engine shut down and the spacecraft was inserted into orbit ('''D''').{{sfn|Unknown|1962|p=46}} This happened after 5 minutes and 10 seconds in a direction pointing east, whereby the spacecraft would gain speed from the rotation of the Earth.{{sfn|Catchpole|2001|pp=188, 460}}{{refn|group=n|The direction of insertion was east and slightly to the north, meaning that, on a three-orbit flight, the tracking network was used optimally and a landing could take place in the North Atlantic Ocean.{{sfn|Alexander & al.|1966|p=215}}}} Here the spacecraft fired the three posigrade rockets for a second to separate it from the launch vehicle.{{sfn|Catchpole|2001|p=133}}{{refn|The sustainer would disintegrate and fall down; after the launch of ''Friendship 7'' a part of the sustainer was found in South Africa.{{sfn|Grimwood|1963|p=164}}|group=n}} Just before orbital insertion and sustainer engine cutoff, g-loads peaked at 8 g (6 g for a suborbital flight).{{sfn|Catchpole|2001|p=340}}{{sfn|Unknown|1961|p=10}} In orbit, the spacecraft automatically turned 180°, pointed the retropackage forward and its nose 14.5° downward and kept this attitude for the rest of the orbital phase to facilitate communication with the ground.{{sfn|Alexander & al.|1966|p=333}}{{sfn|Catchpole|2001|p=120}}{{refn|group=n|The capsule's tendency to drift was countered automatically by the attitude control system (ASCS) which used small hydrogen peroxide thrusters. To save fuel, however, the spacecraft would be allowed to drift from time to time, especially on longer missions.{{sfn|Alexander & al.|1966|pp=195, 450}}}}

Once in orbit, it was not possible for the spacecraft to change its [[trajectory]] except by initiating reentry.{{sfn|Catchpole|2001|p=462}} Each orbit would typically take 88 minutes to complete.{{sfn|Catchpole|2001|p=324}} The lowest point of the orbit, called [[perigee]], was at about {{convert|87|nmi|km|sp=us}} altitude, and the highest point, called [[apogee]], was about {{convert|150|nmi|km|sp=us}} altitude.{{sfn|Catchpole|2001|p=475}} When leaving orbit ('''E'''), the angle of retrofire was 34° downward from the flight path angle.{{sfn|Alexander & al.|1966|p=333}} Retrorockets fired for 10 seconds each ('''F''') in a sequence where one started 5 seconds after the other.{{sfn|Catchpole|2001|p=133}}{{sfn|Unknown|1961|p=9}} During reentry ('''G'''), the astronaut would experience about 8 g (11–12 g on a suborbital mission).{{sfn|Alexander & al.|1966|p=574}} The temperature around the heat shield rose to {{convert|3000|°F|abbr=on|sigfig=2}} and at the same time, there was a two-minute radio blackout due to [[ionization]] of the air around the spacecraft.{{sfn|Unknown|1962|p=9}}{{sfn|Catchpole|2001|p=134}}

After reentry, a small, drogue parachute ('''H''') was deployed at {{convert|21000|ft|abbr=on}} for stabilizing the spacecraft's descent.{{sfn|Catchpole|2001|p=147}} The main parachute ('''I''') was deployed at {{convert|10000|ft|abbr=on}} starting with a narrow opening that opened fully in a few seconds to lessen the strain on the lines.{{sfn|Alexander & al.|1966|p=356}} Just before hitting the water, the landing bag inflated from behind the heat shield to reduce the force of impact ('''J''').{{sfn|Alexander & al.|1966|p=356}} Upon landing the parachutes were released.{{sfn|Catchpole|2001|p=144}} An antenna ('''K''') was raised and sent out signals that could be traced by ships and [[helicopter]]s.{{sfn|Catchpole|2001|p=144}} Further, a green marker dye was spread around the spacecraft to make its location more visible from the air.{{sfn|Catchpole|2001|p=144}}{{refn|group=n|[[Radar chaff]] and a [[SOFAR bomb]] which could be detected by the recovery ship's [[hydrophone]] were eliminated as unnecessary measures after the first orbital flight.{{sfn|Alexander & al.|1966|p=445}}}} [[Frogmen]] brought in by helicopters inflated a collar around the craft to keep it upright in the water.{{sfn|Catchpole|2001|p=166}}{{refn|group=n|The collar was not ready for suborbital missions.{{sfn|Catchpole|2001|p=166}}}} The recovery helicopter hooked onto the spacecraft and the astronaut blew the escape hatch to exit the capsule.{{sfn|Catchpole|2001|pp=144–145}} He was then hoisted aboard the helicopter that finally brought both him and the spacecraft to the ship.{{refn|It was also possible to exit the capsule through the nose cylinder; only Carpenter did this.{{sfn|Alexander & al.|1966|p=143}}{{sfn|Catchpole|2001|p=147}} | group=n}}

<gallery mode="packed">
Mercury profile.jpg|Mercury crewed launches
Glenn62.jpg|[[John Glenn]] in orbit, 1962 (Mercury-Atlas 6)
Shepard Hoisted into Recovery Helicopter - GPN-2000-001361-crop.jpg|[[Alan Shepard]]'s 1961 recovery seen from helicopter (Mercury-Redstone 3)
</gallery>
{{clear}}