Editing Apollo 10 (section)

==Framework==

=== Background ===
{{for|a fuller overview of this subject|Apollo program}}

By 1967, NASA had devised a [[List of Apollo missions#Alphabetical mission types|list of mission types]], designated by letters, that needed to be flown before a landing attempt, which would be the "G" mission. The early uncrewed flights were considered "A" or "B" missions, while [[Apollo 7]], the crewed-flight test of the [[Apollo Command and Service Module|Command and Service Module]] (CSM), was the "C" mission. The first crewed orbital test of the [[Apollo Lunar Module|Lunar Module]] (LM) was accomplished on [[Apollo 9]], the "D" mission. [[Apollo 8]], flown to the Moon's orbit without an LM, was considered a "C-prime" mission, but its success gave NASA the confidence to skip the "E" mission, which would have tested the full Apollo spacecraft in medium or high Earth orbit. Apollo 10, the dress rehearsal for the lunar landing, was to be the "F" mission.<ref name="drew" />{{sfn|Brooks|pp=234–235}}

NASA considered skipping the "F" mission as well and attempting the first lunar landing on Apollo 10. Some within the agency advocated for this, feeling it was senseless to bring astronauts so close to the lunar surface, only to turn away. Although the lunar module intended for Apollo 10 was too heavy to perform the lunar mission, the one intended for [[Apollo 11]] could be substituted by delaying Apollo 10 a month from its May 1969 planned launch.{{sfn|Chaikin|pp=151–152}} NASA official [[George Mueller (engineer)|George Mueller]] favored a landing attempt on {{nowrap|Apollo 10}}; he was known for his aggressive approach to moving the [[Apollo program]] forward.<ref name="Hamish">{{Cite web |last=Lindsay |first=Hamish |title=Apollo 10 |url=https://honeysucklecreek.net/msfn_missions/Apollo_10_mission/hl_apollo10.html |access-date=July 2, 2022 |publisher=Colin Hackellar}}</ref> However, Director of Flight Operations [[Christopher C. Kraft]] and others opposed this, feeling that new procedures would have to be developed for a rendezvous in lunar orbit and that NASA had incomplete information regarding the Moon's [[Mass concentration (astronomy)|mass concentration]]s, which might throw off the spacecraft's trajectory. Lieutenant General [[Samuel C. Phillips|Sam Phillips]], the Apollo Program Manager, listened to the arguments on both sides and decided that having a dress rehearsal was crucial.{{sfn|Chaikin|pp=151–152}}

=== Crew and key Mission Control personnel ===
{{Spaceflight crew
|terminology      = Astronaut
|position1        = Commander (CDR)
|crew1_up         = [[Thomas P. Stafford]]
|flights1_up      = Third
|position2        = Command Module Pilot (CMP)
|crew2_up         = [[John Young (astronaut)|John Young]]
|flights2_up      = Third
|position3        = Lunar Module Pilot (LMP)
|crew3_up         = [[Gene Cernan]]
|flights3_up      = Second
}}

On November 13, 1968, NASA announced the crew members of Apollo 10.<ref name="drew" /> Thomas P. Stafford, the commander, was 38 years old at the time of the mission. A 1952 graduate of the [[United States Naval Academy|Naval Academy]], he was commissioned in the [[United States Air Force|Air Force]]. Selected for the [[NASA Astronaut Group 2|second group of astronauts]] in 1962, he flew as pilot of [[Gemini 6A]] (1965) and command pilot of [[Gemini 9A]] (1966).<ref>{{Cite web |date=March 2014 |title=Thomas P. Stafford, Lieutenant General, U.S. Air Force (Ret.) NASA astronaut (former) |url=https://www.nasa.gov/sites/default/files/atoms/files/stafford_thomas.pdf |url-status=live |archive-url=https://ghostarchive.org/archive/20221009/https://www.nasa.gov/sites/default/files/atoms/files/stafford_thomas.pdf |archive-date=2022-10-09 |publisher=[[Lyndon B. Johnson Space Center]]}}</ref> John Young, the command module pilot, was 38 years old and a [[Commander (United States)#Naval|commander]] in the [[United States Navy|Navy]] at the time of Apollo 10. A 1952 graduate of [[Georgia Tech]] who entered the Navy after graduation and became a test pilot in 1959, he was selected as a Group 2 astronaut alongside Stafford. He flew in [[Gemini 3]] with [[Gus Grissom]] in 1965, becoming the first American not of the [[Mercury Seven]] to fly in space. Young thereafter commanded [[Gemini 10]] (1966), flying with [[Michael Collins (astronaut)|Michael Collins]].{{sfn|Orloff & Harland|p=471}}{{sfn|Press Kit|pp=69–70}} Gene Cernan, the lunar module pilot, was a {{nowrap|35-year-old}} commander in the Navy at the time of Apollo 10. A 1952 graduate of [[Purdue University]], he entered the Navy after graduation. Selected for the [[NASA Astronaut Group 3|third group of astronauts]] in 1963, Cernan flew with Stafford on Gemini 9A before his assignment to Apollo 10.{{sfn|Press Kit|pp=71–72}} With five prior flights among them, the Apollo 10 crew was the most experienced to reach space until the [[Space Shuttle]] era,{{sfn|Stafford & Cassutt|p=545}} and the first American space mission whose crew were all spaceflight veterans.{{sfn|Orloff & Harland|p=279}}

The backup crew for Apollo 10 was [[Gordon Cooper]] as commander, [[Donn F. Eisele]] as command module pilot, and [[Edgar Mitchell|Edgar D. Mitchell]] as lunar module pilot. By the normal crew rotation in place during Apollo, Cooper, Eisele, and Mitchell would have flown on [[Apollo 13]],{{efn|The role of the backup crew was to train and be prepared to fly in the event something happened to the prime crew.<ref>{{Cite web |date=January 30, 2019 |title=50 years ago, NASA names Apollo 11 crew |url=https://www.nasa.gov/feature/50-years-ago-nasa-names-apollo-11-crew |access-date=February 24, 2023 |publisher=NASA}}</ref> Backup crews, according to the rotation, were assigned as the prime crew three missions after their assignment of backups.}} but Cooper and Eisele never flew again. [[Deke Slayton]], Director of Flight Crew Operations, felt that Cooper did not train as hard as he could have. Eisele was blackballed because of incidents during Apollo 7, which he had flown as CMP and which had seen conflict between the crew and ground controllers; he had also been involved in a messy divorce. Slayton only assigned the two as backups because he had few veteran astronauts available.{{sfn|Slayton & Cassutt|p=236}} Cooper and Eisele were replaced by [[Alan Shepard]] and [[Stuart Roosa]] respectively. Feeling they needed additional training time, [[George Mueller (NASA)|George Mueller]] rejected the Apollo 13 crew. The crew was switched to [[Apollo 14]], which saw Shepard and Mitchell walk on the Moon.{{sfn|Slayton & Cassutt|p=236}}

For projects [[Project Mercury|Mercury]] and [[Project Gemini|Gemini]], a prime and a backup crew had been designated, but for Apollo, a third group of astronauts, known as the support crew, was also designated. Slayton created the support crews early in the Apollo program on the advice of McDivitt, who would lead Apollo 9. McDivitt believed that, with preparation going on in facilities across the U.S., meetings that needed a member of the flight crew would be missed. Support crew members were to assist as directed by the mission commander.{{sfn|Slayton & Cassutt|p=184}} Usually low in seniority, they assembled the mission's rules, [[flight plan]], and checklists, and kept them updated.<ref>{{Cite journal |last=Hersch |first=Matthew |date=July 19, 2009 |title=The fourth crewmember |url=https://www.airspacemag.com/space/the-fourth-crewmember-37046329/ |journal=[[Air & Space/Smithsonian]] |access-date=October 4, 2019}}</ref>{{sfn|Brooks|p=261}} For Apollo 10, they were [[Joe Engle]], [[James Irwin]], and [[Charles Duke]].{{sfn|Orloff & Harland|p=256}}

[[Flight controller#Flight director|Flight directors]] were [[Gerry Griffin]], [[Glynn Lunney]], [[Milt Windler]], and [[Pete Frank]].{{sfn|Orloff & Harland|p=236}} Flight directors during Apollo had a one-sentence job description: "The flight director may take any actions necessary for crew safety and mission success."<ref>{{Cite news |last=Williams |first=Mike |date=September 13, 2012 |title=A legendary tale, well-told |url=https://news.rice.edu/2012/09/13/a-legendary-tale-well-told/ |url-status=dead |archive-url=https://web.archive.org/web/20200817125432/https://news.rice.edu/2012/09/13/a-legendary-tale-well-told/ |archive-date=August 17, 2020 |access-date=October 5, 2019 |publisher=[[Rice University]] Office of Public Affairs}}</ref> [[Flight controller#CAPCOM|CAPCOMs]] were Duke, Engle, [[Jack Lousma]], and [[Bruce McCandless II]].{{sfn|Orloff & Harland|p=256}}

===Call signs and mission insignia===
[[File:Stafford and Snoopy.jpeg|thumb|left|En route to launch, Stafford touches a "Snoopy" doll]]

The command module was given the call sign "Charlie Brown" and the lunar module the call sign "Snoopy". These were taken from the characters in the comic strip, ''[[Peanuts]]'', [[Charlie Brown]], and [[Snoopy]].{{sfn|Orloff & Harland|p=256}} These names were chosen by the astronauts with the approval of [[Charles M. Schulz|Charles Schulz]], the strip's creator,<ref name="snoop" /> who was uncertain it was a good idea, since Charlie Brown was always a failure.{{sfn|French & Burgess|p=1348}} The choice of names was deemed undignified by some at NASA, as were the choices for Apollo 9's CM and LM ("Gumdrop" and "Spider"). Public relations chief [[Julian Scheer]] urged a change for the lunar landing mission.{{sfn|Brooks|pp=301–302}} But for Apollo 10, according to Cernan, "The P.R.-types lost this one big-time, for everybody on the planet knew the klutzy kid and his adventuresome beagle, and the names were embraced in a public relations bonanza."{{sfn|Cernan|p=1156}} Apollo 11's call signs were "Columbia" for the command module and "Eagle" for the lunar module.{{sfn|Orloff & Harland|p=280}}

Snoopy, Charlie Brown's dog, was chosen for the call sign of the lunar module since it was to "snoop" around the landing site, with Charlie Brown given to the command module as Snoopy's companion.<ref>{{Cite web |last=Alaina |date=May 16, 2019 |title=Snoopy, Charlie Brown and Apollo 10 |url=https://www.kennedyspacecenter.com/blog/snoopy-charlie-brown-and-apollo-10 |access-date=June 19, 2022 |publisher=[[Kennedy Space Center]]}}</ref> Snoopy had been associated for some time with the space program, with workers who performed in an outstanding manner awarded silver "[[Silver Snoopy award|Snoopy pins]]", and Snoopy posters were seen at NASA facilities, with the cartoon dog having traded in his [[World War I]] aviator's headgear for a space helmet.<ref name="snoop" /> Stafford stated that, given the pins, "the choice of Snoopy [as call sign] was a way of acknowledging the contributions of the hundreds of thousands of people who got us there".{{sfn|Stafford & Cassutt|p=547}} The use of the dog was also appropriate since, in the comic strip, Snoopy had journeyed to the Moon the year before, thus defeating, according to Schulz, "the Americans, the Russians, and that stupid cat next door".<ref name="snoop">{{Cite news |last=Roberts |first=Steven V. |date=May 26, 1969 |title=You're a brave man, Charlie Brown |url=https://timesmachine.nytimes.com/timesmachine/1969/05/26/issue.html |url-access=subscription |work=[[The New York Times]] |page=20}}</ref>

[[File:Apollo 10 Flown Silver Robbins Medallion (SN-70).jpg|thumb|Apollo 10 space-flown silver [[NASA space-flown Robbins medallions of the Apollo missions|Robbins medallion]]]]
The shield-shaped mission insignia shows a large, three-dimensional [[Roman numerals|Roman numeral]] X sitting on the Moon's surface, in Stafford's words, "to show that we had left our mark". Although it did not land on the Moon, the prominence of the number represents the contributions the mission made to the Apollo program. A CSM circles the Moon as an LM ascent stage flies up from its low pass over the lunar surface with its engine firing. The Earth is visible in the background. On the mission patch, a wide, light blue border carries the word APOLLO at the top and the crew names around the bottom. The patch is trimmed in gold. The insignia was designed by Allen Stevens of [[Rockwell International]].<ref>{{Cite web |last=Hengeveld |first=Ed |date=May 20, 2008 |title=The man behind the Moon mission patches |url=http://www.collectspace.com/news/news-052008a.html |access-date=July 18, 2009 |publisher=[[collectSPACE]]}} "A version of this article was published concurrently in the [[British Interplanetary Society]]'s ''[[Spaceflight (magazine)|Spaceflight]]'' magazine." (June 2008; pp. 220–225).</ref>

===Training and preparation===
[[File:Two members of the Apollo 10 prime crew participate in simulation activity.jpg|thumb|left|Stafford (right) and Cernan in the lunar module simulator, April 1969]]
Apollo 10, the "F" mission or dress rehearsal for the lunar landing, had as its primary objectives to demonstrate crew, space vehicle, and mission support facilities performance during a crewed mission to lunar orbit, and to evaluate the performance of the lunar module there. In addition, it was to attempt photography of Apollo Landing Site 2 (ALS-2) in the [[Sea of Tranquillity]], the contemplated landing site for Apollo 11.{{sfn|Orloff & Harland|pp=256, 285}} According to Stafford, <blockquote>Our flight was to take the first lunar module to the moon. We would take the lunar module, go down to within about ten miles above the moon, nine miles above the mountains, radar map, photo map, pick out the first landing site, do the first rendezvous around the moon, pick out some future landing sites, and come home.{{sfn|French & Burgess|pp=1337–1338}}</blockquote>

Apollo 10 was to adhere as closely as possible to the plans for Apollo 11, including its trajectory to and from lunar orbit, the timeline of mission events, and even the angle of the Sun at ALS-2. However, no landing was to be attempted.{{sfn|Press Kit|p=2}} ALS-1, given that number because it was the furthest to the east of the candidate sites,{{efn|The five candidate sites for the first lunar landing, ALS-1 through ALS-5, were numbered from the easternmost to the westernmost. See {{harvnb|Press Kit|p=37}}}} and also located in the Sea of Tranquility, had been extensively photographed by Apollo 8 astronauts; at the suggestion of scientist-astronaut [[Harrison Schmitt]], the launch of Apollo 10 had been postponed a day so ALS-2 could be photographed under proper conditions. ALS-2 was chosen as the lunar landing site since it was relatively smooth and of scientific interest, while ALS-1 was deemed too far to the east.{{sfn|Wilhelms|pp=189–192}} Thus, when Apollo 10's launch date was announced on January 10, 1969, it was shifted from its placeholder date of May 1 to May 17, rather than to May 16. On March 17, 1969, the launch was slipped one day to May 18, to allow for a better view of ALS-3, to the west of ALS-2.<ref name="drew" /> Another deviation from the plans for Apollo 11 was that Apollo 10 was to spend an additional day in lunar orbit once the CSM and LM rendezvoused; this was to allow time for additional testing of the LM's systems, as well as for photography of possible future Apollo landing sites.{{sfn|Press Kit|pp=6, 8}}

The Apollo 10 astronauts undertook five hours of formal training for each hour of the mission's eight-day duration. This was in addition to the normal mission preparations such as technical briefings, pilot meetings, and study. They took part in the testing of the CSM at the [[Downey, California|Downey]], California, facility of its manufacturer, [[North American Rockwell]], and of the LM at [[Grumman]] in [[Bethpage, New York|Bethpage]], New York. They visited [[Cambridge, Massachusetts|Cambridge]], Massachusetts, for briefings on the [[Apollo Guidance Computer]] at the [[MIT Instrumentation Lab|Massachusetts Institute of Technology Instrumentation Laboratory]]. They each spent more than 300 hours in simulators of the CM or LM at the [[Manned Spacecraft Center]] (MSC) in Houston and at [[Kennedy Space Center]] (KSC) in Florida. To train for the high-acceleration conditions they would experience in returning to Earth's atmosphere, they endured MSC's centrifuge.{{sfn|Press Kit|p=65}}

====Lunar landing capability====
{| class="wikitable plainrowheaders floatright"
|+ Comparison of LM weights
|-
! scope="col" rowspan=2 | Component
! scope="col" colspan=2 | Apollo 10 LM-4
! scope="col" colspan=2 | Apollo 11 LM-5
|-
! scope="col" | {{abbr|lb|pound (mass)}}
! scope="col" | {{abbr|kg|kilogram}}
! scope="col" | lb
! scope="col" | kg
|-
! scope="row" | Descent stage dry{{sfn|Orloff|2004|pp=276–277}}
| {{cvt|4,703|lb|kg|disp=table}} || {{cvt|4,483|lb|kg|disp=table}}
|-
! scope="row" | Descent stage propellant{{sfn|Orloff|2004|p=295}}
| {{cvt|18,219|lb|kg|disp=table}} || {{cvt|18,184|lb|kg|disp=table}}
|- style="font-weight: bold; background-color: #EAECF0;"
! scope="row" style="font-weight: bold;" | Descent stage subtotal
| {{cvt|22,922|lb|kg|disp=table}} || {{cvt|22,667|lb|kg|disp=table}}
|-
! scope="row" | Ascent stage dry{{sfn|Orloff|2004|pp=276–277}}
| style="background-color: #9f9" {{cvt|4,781|lb|kg|disp=table}} || {{cvt|4,804|lb|kg|disp=table}}
|-
! scope="row" | Ascent stage propellant{{sfn|Orloff|2004|p=296}}
| style="background-color: #f99;" {{cvt|2,631|lb|kg|disp=table}} || {{cvt|5,238|lb|kg|disp=table}}
|- style="font-weight: bold; background-color:#EAECF0;"
! scope="row" style="font-weight: bold;" | Ascent stage subtotal
| {{cvt|7,412|lb|kg|disp=table}} || {{cvt|10,042|lb|kg|disp=table}}
|-
! scope="row" | Equipment
| {{cvt|401|lb|kg|disp=table}} || {{cvt|569|lb|kg|disp=table}}
|- style="font-weight: bold; background-color:#EAECF0;"
! scope="row" style="font-weight: bold;" | Total{{sfn|Orloff|2004|pp=276–277}}
| {{cvt|30,735|lb|kg|disp=table}} || {{cvt|33,278|lb|kg|disp=table}}
|}

While Apollo 10 was meant to follow the procedures of a lunar landing mission to the point of powered descent, Apollo 10's LM was not capable of landing and returning to lunar orbit. The ascent stage was loaded with the amount of [[aerozine 50|fuel]] and [[nitrogen tetroxide|oxidizer]] it would have had remaining if it had lifted off from the surface and reached the altitude at which the Apollo 10 ascent stage fired; this was only about half the total amount required for lift off and rendezvous with the CSM. The mission-loaded LM weighed {{convert|30735|lb|kg|order=flip}}, compared to {{convert|33278|lb|kg|order=flip}} for the Apollo 11 LM, which made the first landing.{{sfn|Orloff|2004|pp=276–277}} Additionally, the software necessary to guide the LM to a landing was not available at the time of Apollo 10.<ref name="Hamish" />

Craig Nelson wrote in his book ''Rocket Men'' that NASA took special precautions to ensure Stafford and Cernan would not attempt to make the first landing. Nelson quoted Cernan as saying "A lot of people thought about the kind of people we were: 'Don't give those guys an opportunity to land, 'cause they might!' So the ascent module, the part we lifted off the lunar surface with, was short-fueled. The fuel tanks weren't full. So had we literally tried to land on the Moon, we couldn't have gotten off."<ref>[[#Nelson|Nelson 2009]], p. 14</ref> Mueller, NASA's Associate Administrator for Manned Space Flight, stated, <blockquote>There had been some speculation about whether or not the crew might have landed, having gotten so close. They might have wanted to, but it was impossible for that lunar module to land. It was an early design that was too heavy for a lunar landing, or, to be more precise, too heavy to be able to complete the ascent back to the command module. It was a test module, for the dress rehearsal only, and that was the way it was used.<ref>{{Cite web |date=April 9, 2019 |title=Apollo 10 |url=https://solarsystem.nasa.gov/missions/apollo-10/in-depth/ |url-status=dead |archive-url=https://web.archive.org/web/20220804181858/https://solarsystem.nasa.gov/missions/apollo-10/in-depth/ |archive-date=August 4, 2022 |access-date=June 19, 2022 |publisher=NASA Science}}</ref></blockquote>

=== Equipment ===
The descent stage of the LM was delivered to KSC on October 11, 1968, and the ascent stage arrived five days later. They were mated on November 2. The [[Apollo command and service module#Service module (SM)|Service Module]] (SM) and [[Apollo command and service module#Command module (CM)|Command Module]] (CM) arrived on November 24 and were mated two days later. Portions of the [[Saturn V]] launch vehicle arrived during November and December 1968, and the complete launch vehicle was erected in the [[Vehicle Assembly Building]] (VAB) on December 30. After being tested in an altitude chamber, the CSM was placed atop the launch vehicle on February 6, 1969.{{sfn|Orloff & Harland|p=257}} The completed space vehicle was rolled out to [[Launch Complex 39B]] on March 11, 1969—the fact that it had been assembled in the VAB's High Bay 2 (the first time it had been used) required the [[Crawler-transporter|crawler]] to exit the rear of the VAB before looping around the building and joining the main [[crawlerway]], proceeding to the launch pad.<ref name="roll" /> This rollout, using [[Mobile launcher platform#Mobile Launcher Platform-3|Mobile Launch Platform-3]] (MLP-3),<ref name="drew" /> happened eight days after the launch of Apollo 9, while that mission was still in orbit.<ref name="roll">{{Cite web |date=March 11, 2019 |title=50 years ago: Apollo 10 rolls out to launch pad |url=https://www.nasa.gov/feature/50-years-ago-apollo-10-rolls-out-to-launch-pad |access-date=June 19, 2022 |publisher=[[NASA]]}}</ref>

The [[launch vehicle]] for Apollo 10 was a Saturn V, designated AS-505,<ref name="background">{{Cite web |date=February 10, 2017 |title=Apollo 10: Background |url=https://history.nasa.gov/afj/ap10fj/as10-prep.html |access-date=June 21, 2022 |website=Apollo 10 Lunar Flight Journal |publisher=[[NASA]]}}</ref> the fifth flight-ready Saturn V to be launched and the third to take astronauts to orbit.{{sfn|Mission Report|p=14-1}} The Saturn V differed from that used on Apollo 9 in having a lower dry weight (without propellant) in its first two stages, with a significant reduction to the interstage joining them. Although the S-IVB third stage was slightly heavier, all three stages could carry a greater weight of propellant, and the [[S-II]] second stage generated more thrust than that of Apollo 9.{{sfn|Press Kit|p=55}}

The Apollo spacecraft for the Apollo 10 mission was composed of Command Module 106 (CM-106), Service Module 106 (SM-106, together with the CM known as CSM-106), Lunar Module 4 (LM-4), a spacecraft-lunar module adapter (SLA), numbered as SLA-13A, and a launch escape system.{{sfn|Press Kit|p=38}}<ref name="hardware">{{Cite web |date=March 1978 |title=Apollo/Skylab ASTP and Shuttle Orbiter Major End Items |url=https://s3.documentcloud.org/documents/6473665/Apollo-Skylab-ASTP-and-Shuttle-Orbiter-Major-End.pdf |url-status=live |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 |publisher=[[NASA]] |page=11}}</ref> The SLA was a mating structure joining the Instrument Unit on the S-IVB stage of the Saturn V launch vehicle and the CSM, and acted as a housing for the LM, while the [[Launch Escape System]] (LES) contained rockets to propel the CM to safety if there was an aborted launch.{{sfn|Press Kit|p=38}} At about 76.99 metric tons, Apollo 10 would be the heaviest spacecraft to reach orbit to that point.<ref name="drew" />