Editing Apollo 9 (section)

== Hardware ==
=== Launch vehicle ===
The [[Saturn V]] (AS-504) used on Apollo{{nbsp}}9 was the fourth to be flown, the second to carry astronauts to space,{{sfn|Press Kit|p=8}} and the first to bear a lunar module. Although similar in configuration to the Saturn{{nbsp}}V used on Apollo 8, several changes were made. The inner core of the F-1 engine chamber in the first (S-IC) stage was removed, thus saving weight and allowing for a slight increase in [[specific impulse]]. Weight was also saved by replacing the skins of the [[liquid oxygen]] tanks with lighter ones, and by providing lighter versions of other components. Efficiency was increased in the S-II second stage with uprated J-2 engines, and through a closed-loop propellant utilization system rather than Apollo 8's open-loop system.{{sfn|Mission Report|pp=A-59, inside back cover}} Of the {{convert|3250|lb}} weight reduction in the second stage, about half came from a 16 percent reduction in the thickness of the tank side walls.{{sfn|''Science News'' 1969-03-22b|p=283}}

=== Spacecraft, equipment and call signs ===
Apollo{{nbsp}}9 used CSM-104, the third Block II CSM to be flown with astronauts aboard. Apollo 8, lacking a lunar module, did not have docking equipment; Apollo{{nbsp}}9 flew the probe-and-drogue assembly used for docking along with other equipment added near the forward hatch of the CM; this allowed for rigid docking of the two craft, and for internal transfer between CM and LM.{{sfn|Mission Report|pp=A-1, inside back cover}} Had the switch in missions between Apollo{{nbsp}}8 and{{nbsp}}9 not occurred, the Earth-orbit mission would have flown CSM-103, which flew on Apollo 8.{{sfn|French & Burgess|pp=338–339}}

The Earth-orbit mission was originally supposed to use LM-2 as its lunar module, but the crew found numerous flaws in it, many associated with it being the first flight-ready lunar module off Grumman's production line. The delay occasioned by the switch in missions allowed LM-3 to be available, a machine the crew found far superior.{{sfn|French & Burgess|p=339}} Neither LM-2 nor LM-3 could have been sent to the Moon as both were too heavy; Grumman's weight reduction program for the LMs only became fully effective with LM-5, designated for Apollo 11.{{sfn|''Science News'' 1969-03-01|p=218}} Small cracks in LM-3's aluminum alloy structure due to stresses such as the insertion of a rivet proved an ongoing issue; Grumman's engineers continued working to fix them until the LM had to be mounted on the Saturn{{nbsp}}V in December 1968,{{sfn|''Science News'' 1969-03-01|p=219}} where it was housed inside the Spacecraft-Lunar Module Adapter, numbered as SLA-11A.<ref name = "hardware">{{cite web|title=Apollo/Skylab ASTP and Shuttle Orbiter Major End Items|date=March 1978|url=https://s3.documentcloud.org/documents/6473665/Apollo-Skylab-ASTP-and-Shuttle-Orbiter-Major-End.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://s3.documentcloud.org/documents/6473665/Apollo-Skylab-ASTP-and-Shuttle-Orbiter-Major-End.pdf |archive-date=2022-10-09 |url-status=live|publisher=[[NASA]]|page=11}}</ref> LM-2 never flew in space and is in the [[National Air and Space Museum]].<ref>{{cite web|url=https://airandspace.si.edu/collection-objects/lunar-module-2-apollo|publisher=[[National Air and Space Museum]]|title=Lunar Module LM-2|access-date=April 19, 2019|archive-date=January 15, 2020|archive-url=https://web.archive.org/web/20200115082343/https://airandspace.si.edu/collection-objects/lunar-module-2-apollo|url-status=dead}}</ref>

The Apollo astronauts were provided with early versions of the [[Sony Walkman]], portable [[cassette recorder]]s intended to allow them to make observations during the mission. The Apollo{{nbsp}}9 crew was the first to be allowed to bring music [[mixtape]]s, one each, that could be played in that device. McDivitt and Scott preferred [[easy listening]] and [[country music]]; Schweickart's [[cassette tape]] of [[classical music]] went missing until the ninth day of the ten-day mission, when it was presented to him by Scott.<ref>{{cite web|last=Hollingham|first=Richard|url=http://www.bbc.com/future/story/20130429-thirteen-space-music-firsts|publisher=[[BBC]]|title=Space music firsts|date=November 18, 2014|access-date=July 5, 2019}}</ref><ref>{{cite web|last=Hollingham|first=Richard|url=http://www.bbc.com/future/story/20190704-apollo-in-50-numbers-the-technology|publisher=[[BBC]]|title=Apollo in 50 numbers: The technology|date=July 5, 2019|access-date=July 5, 2019}}</ref>

After the [[Gemini 3]] craft was dubbed ''[[Molly Brown]]'' by Grissom, NASA forbade naming spacecraft.{{sfn|Shepard, Slayton, & Barbree|pp=227–228}} The fact that during the Apollo{{nbsp}}9 mission, the CSM and LM would separate and need different [[call sign]]s caused the Apollo{{nbsp}}9 astronauts to push for a change. In simulations, they began to refer to the CSM as "Gumdrop", a name inspired by the CM's appearance while in the blue protective wrapping in which it was transported from the manufacturer, and the LM as "Spider", inspired by the LM's appearance with landing legs deployed.{{sfn|Orloff|p=282}} Personnel in NASA public relations thought the names were too informal, but the call signs ultimately gained official sanction.{{sfn|French & Burgess|p=340}} NASA required more formal call signs for future missions, starting with Apollo 11.{{sfn|Scott & Leonov|p=234}}

<gallery widths="200" heights="160">
File:Lunar Module 3 arrives at KSC aboard Super Guppy (KSC-68PC-85).jpg|alt=cased LM on airplane in hangar|LM-3 arrives at KSC, June 1968
File:Apollo 9 backup crew (S68-55255).jpg|alt=Blue command module Gumdrop|Apollo{{nbsp}}9 backup crew training in ''Gumdrop''
</gallery>

=== Life Support System backpack ===
[[File:Apollo 9 Schweickart with EMU.jpg|upright|thumb|alt=Spacesuited man with large backpack|Schweickart with the life support backpack]]

The [[Apollo/Skylab A7L|Extravehicular Mobility Unit]] (EMU) backpack flew for the first time on Apollo{{nbsp}}9, used by Schweickart during his EVA.<ref name="sp368ch6">[[#sp368|Carson et al. 1975]]</ref> This included the [[Portable Life Support System]] (PLSS), providing oxygen to the astronaut and water for the [[Liquid Cooling Garment]] (LCG), which helped prevent overheating during extravehicular activity.{{sfn|Press Kit|pp=84–85}} Also present was the [[Oxygen Purge System]] (OPS), the "bedroll" atop the backpack, which could provide oxygen for up to roughly an hour if the PLSS failed.{{sfn|Thomas|p=22}} A more advanced version of the EMU was used for the lunar landing on Apollo 11.{{sfn|Thomas|p=22}}

During his stand-up EVA,{{efn|A stand-up EVA is when the astronaut only partially exits the spacecraft.<ref>{{cite web|url=http://planet4589.org/space/jsr/back/news.601.txt|title=Shuttle and Station|date=October 12, 2008|access-date=April 29, 2019|publisher=Jonathan's Space Report}}</ref>{{sfn|Thomas|McMann|p=68}}}} Scott did not wear a PLSS, but was connected to the CM's life support systems through an umbilical, utilizing a Pressure Control Valve (PCV). This device had been created in 1967 to allow for stand-up EVAs from the hatches of the LM or CM, or for brief ventures outside. It was later used by Scott for his lunar surface stand-up EVA on [[Apollo 15]], and for the deep-space EVAs by the command module pilots of the final three Apollo flights.{{sfn|Thomas|pp=24–25}}