Apollo 10

Apollo 10

Apollo 10's Lunar Module, Snoopy, approaches the Command and Service Module Charlie Brown for redocking
Mission type	Crewed lunar orbital CSM/LM flight (F)
Operator	NASA
COSPAR ID	CSM: 1969-043A[1] LM: 1969-043C
SATCAT no.	CSM: 3941 LM: 3948
Mission duration	8 days, 3 minutes, 23 seconds
Spacecraft properties
Spacecraft	North American Rockwell LM: Grumman
Launch mass	42,775 kg[2]
Landing mass	4,945 kilograms (10,901 lb)
Crew
Crew size	3
Members	Thomas P. Stafford John W. Young Eugene A. Cernan
Callsign	CSM: Charlie Brown LM: Snoopy
Start of mission
Launch date	May 18, 1969, 16:49:00 (1969-05-18UTC16:49Z) UTC[3]
Rocket	Saturn V SA-505
Launch site	Kennedy LC-39B
End of mission
Recovered by	USS Princeton
Landing date	May 26, 1969, 16:52:23 (1969-05-26UTC16:52:24Z) UTC
Landing site	15°2′S 164°39′W / 15.033°S 164.650°W / -15.033; -164.650 (Apollo 10 splashdown)
Orbital parameters
Reference system	Selenocentric
Periselene altitude	109.6 kilometers (59.2 nmi)
Aposelene altitude	113.0 kilometers (61.0 nmi)
Inclination	1.2 degrees
Period	2 hours
Lunar orbiter
Spacecraft component	Command and service module
Orbital insertion	May 21, 1969, 20:44:54 UTC
Orbital departure	May 24, 1969, 10:25:38 UTC
Orbits	31
Lunar orbiter
Spacecraft component	Lunar Module
Orbits	4 (while solo)
Orbital parameters
Periselene altitude	14.4 kilometers (7.8 nmi)
Docking with LM
Docking date	May 18, 1969, 20:06:36 UTC
Undocking date	May 22, 1969, 19:00:57 UTC
Docking with LM Ascent Stage
Docking date	May 23, 1969, 03:11:02 UTC
Undocking date	May 23, 1969, 05:13:36 UTC
Left to right: Cernan, Stafford, Young Apollo program ← Apollo 9 Apollo 11 →

Apollo 10 (May 18–26, 1969) was the fourth human spaceflight in the United States' Apollo program and the second to orbit the Moon. NASA, the mission's operator, described it as a "dress rehearsal" for the first Moon landing (Apollo 11, two months later^[4]). It was designated an "F" mission, intended to test all spacecraft components and procedures short of actual descent and landing.

After the spacecraft reached lunar orbit, astronaut

While NASA had considered attempting the first crewed lunar landing on Apollo 10, mission planners ultimately decided that it would be prudent to have a practice flight to hone the procedures and techniques. The crew encountered some problems during the flight:

The mission's

By 1967, NASA had devised a

On November 13, 1968, NASA announced the crew members of Apollo 10.[7] Thomas P. Stafford, the commander, was 38 years old at the time of the mission. A 1952 graduate of the Naval Academy, he was commissioned in the Air Force. Selected for the second group of astronauts in 1962, he flew as pilot of Gemini 6A (1965) and command pilot of Gemini 9A (1966).^[11] John Young, the command module pilot, was 38 years old and a commander in the 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.^[12][13] Eugene Cernan, the lunar module pilot, was a 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 third group of astronauts in 1963, Cernan flew with Stafford on Gemini 9A before his assignment to Apollo 10.^[14] With five prior flights among them, the Apollo 10 crew was the most experienced to reach space until the Space Shuttle era,^[15] and the first American space mission whose crew were all spaceflight veterans.^[16]

The backup crew for Apollo 10 was

For projects Mercury and 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.^[19] Usually low in seniority, they assembled the mission's rules, flight plan, and checklists, and kept them updated.^[20][21] For Apollo 10, they were Joe Engle, James Irwin, and Charles Duke.^[22]

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.^[22] These names were chosen by the astronauts with the approval of Charles Schulz, the strip's creator,^[25] who was uncertain it was a good idea, since Charlie Brown was always a failure.^[26] 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.^[27] 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."^[28] Apollo 11's call signs were "Columbia" for the command module and "Eagle" for the lunar module.^[29]

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.^[30] Snoopy had been associated for some time with the space program, with workers who performed in an outstanding manner awarded silver "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.^[25] 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".^[31] 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".^[25]

The shield-shaped mission insignia shows a large, three-dimensional 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.^[32]

Training and preparation

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

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.[35] ALS-1, given that number because it was the furthest to the east of the candidate sites,^[b] 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, of scientific interest, and ALS-1 was deemed too far to the east.^[36] 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.^[7] 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.^[37]

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

Craig Nelson wrote in his book Rocket Men that NASA took special precaution 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."[42] Mueller, NASA's Associate Administrator for Manned Space Flight, stated,

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.^[43]

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

The launch vehicle for Apollo 10 was a Saturn V, designated AS-505,^[46] the fifth flight-ready Saturn V to be launched and the third to take astronauts to orbit.^[47] 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.^[48]

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.

Launch and outbound trip

Apollo 10 launched from KSC on May 18, 1969, at 12:49:00 EDT (16:49:00 UT), at the start of a 4.5-hour launch window. The launch window was timed to secure optimal lighting conditions at Apollo Landing Site 2 at the time of the LM's closest approach to the site days later. The launch followed a countdown that had begun at 21:00:00 EDT on May 16 (01:00:00 UT on May 17). Because preparations for Apollo 11 had already begun at Pad 39A, Apollo 10 launched from Pad 39B, becoming the only Apollo flight to launch from that pad^[51] and the only one to be controlled from its Firing Room 3.^[10][52]

Problems that arose during the countdown were dealt with during the built-in holds, and did not delay the mission.

The crew experienced a somewhat rough ride on the way to orbit due to

Arrival and initial operations

At 75:55:54 into the mission, 176.1 kilometers (95.1 nautical miles) above the far side of the Moon, the CSM's

After Stafford and Cernan checked out Snoopy, they returned to Charlie Brown for a rest. Then they re-entered Snoopy and undocked it from the CSM at 98:29:20.^[63] Young, who remained in the CSM, became the first person to fly solo in lunar orbit.^[66] After undocking, Stafford and Cernan deployed the LM's landing gear and inspected the LM's systems. The CSM performed an 8.3-second burn with its RCS thrusters to separate itself from the LM by about 30 feet, after which Young visually inspected the LM from the CSM. The CSM performed another separation burn, this time separating the two spacecraft by about 3.7 kilometers (2 nautical miles).^[63] The LM crew then performed the descent orbit insertion maneuver by firing their descent engine for 27.4 seconds at 99:46:01.6, and tested their craft's landing radar as they approached the 15,000-meter (50,000-foot) altitude where the subsequent Apollo 11 mission would begin powered descent to land on the Moon.^[67] Previously, the LM's landing radar had only been tested under terrestrial conditions.^[68] While the LM executed these maneuvers, Young monitored the location and status of the LM from the CSM, standing by to rescue the LM crew if necessary.^[69] Cernan and Stafford surveyed ALS-2, coming within 15.6 kilometers (8.4 nautical miles) of the surface at a point 15 degrees to its east, then performed a phasing burn at 100:58:25.93, thrusting for just under 40 seconds to allow a second pass at ALS-2, when the craft came within 14.4 kilometers (7.8 nautical miles) of the Moon, its closest approach.^[67] Reporting on his observations of the site from the LM's low passes, Stafford indicated that ALS-2 seemed smoother than he had expected^[69] and described its appearance as similar to the desert surrounding Blythe, California;^[70] but he observed that Apollo 11 could face rougher terrain downrange if it approached off-target.^[69] Based upon Apollo 10's observations from relatively low altitude, NASA mission planners became comfortable enough with ALS-2 to confirm it as the target site for Apollo 11.^[71]

The next action was to prepare to separate the LM ascent stage from the descent stage, to jettison the descent stage, and fire the

Snoopy rendezvoused with and re-docked with Charlie Brown at 106:22:02, just under eight hours after undocking.[63] The docking was telecast live in color from the CSM.^[76][77] Once Cernan and Stafford had re-entered Charlie Brown, Snoopy was sealed off and separated from Charlie Brown. The rest of the LM's ascent-stage engine fuel was burned to send it on a trajectory past the Moon and into a heliocentric orbit.^[78][79]

It was the only Apollo LM to meet this fate. The Apollo 11 ascent stage would be left in lunar orbit to crash, while post-Apollo 11 ascent stages were steered into the Moon to obtain readings from

After ejecting the LM ascent stage, the crew slept and performed photography and observation of the lunar surface from orbit. Though the crew located 18 landmarks on the surface and took photographs of various surface features, crew fatigue necessitated the cancellation of two scheduled television broadcasts. Thereafter, the main Service Propulsion System engine of the CSM re-ignited for about 2.5 minutes to set Apollo 10 on a trajectory towards Earth, achieving such a trajectory at 137:39:13.7. As it departed lunar orbit, Apollo 10 had orbited the Moon 31 times over the span of about 61 hours and 37 minutes.^[63]

During their journey back to Earth, the crew performed some observational activities which included star-Earth horizon sightings for navigation. The crew also performed a scheduled test to gauge the reflectivity of the CSM's high-gain antenna and broadcast six television transmissions of varying durations to show views inside the spacecraft and of the Earth and Moon from the crew's vantage point.^[63] Cernan reported later that he and his crewmates became the first to "successfully shave in space" during the return trip, using a safety razor and thick shaving gel, as such items had been deemed a safety hazard and prohibited on earlier flights.^[80] The crew fired the engine of the CSM for the only mid-course-correction burn required during the return trip at 188:49:58, a few hours before separation of the CM from the SM. The burn lasted about 6.7 seconds.^[63]

As the spacecraft rapidly approached Earth on the final day of the mission, the Apollo 10 crew traveled faster than any humans before or since, relative to Earth: 39,897 km/h (11.08 km/s or 24,791 mph).

Orbital operations and the solo maneuvering of the LM in partial descent to the lunar surface paved the way for the successful Apollo 11 lunar landing by demonstrating the capabilities of the mission hardware and systems. The crew demonstrated that the checkout procedures of the LM and initial descent and rendezvous could be accomplished within the allotted time, that the communication systems of the LM were sufficient, that the rendezvous and landing radars of the LM were operational in lunar orbit, and that the two spacecraft could be adequately monitored by personnel on Earth. Additionally, the precision of lunar orbital navigation improved with Apollo 10 and, combined with data from Apollo 8, NASA expected that it had achieved a level of precision sufficient to execute the first crewed lunar landing.[63] After about two weeks of Apollo 10 data analysis, a NASA flight readiness team cleared Apollo 11 to proceed with its scheduled July 1969 flight.^[88] On July 16, 1969, the next Saturn V to launch carried the astronauts of Apollo 11: Neil Armstrong, Buzz Aldrin, and Michael Collins. On July 20, Armstrong and Aldrin landed on the Moon, and four days later the three astronauts returned to Earth, fulfilling John F. Kennedy's challenge to Americans to land astronauts on the Moon and return them safely to Earth by the end of the 1960s.^[89][90]

In July 1969, Stafford replaced

The Smithsonian has been accountable for the command module Charlie Brown since 1970. The spacecraft was on display in several countries until it was placed on loan to the

The ascent stage of the Lunar Module Snoopy was jettisoned into a heliocentric orbit. Snoopy's ascent stage orbit was not tracked after 1969, and its whereabouts were unknown. In 2011, a group of amateur astronomers in the UK started a project to search for it. In June 2019, the Royal Astronomical Society announced a possible rediscovery of Snoopy, determining that small Earth-crossing asteroid 2018 AV₂ is likely to be the spacecraft with "98%" certainty.^[95] It is the only once-crewed spacecraft known to still be in outer space without a crew.^[96][97]

Snoopy's descent stage was jettisoned in lunar orbit; its current location is unknown, though it may have eventually crashed into the Moon as a result of orbital decay.^[98] Phil Stooke, a planetary scientist who studied the lunar crash sites of the LM's ascent stages, wrote that the descent stage "crashed at an unknown location",^[99] and another source stated that the descent stage "eventually impact(ed) within a few degrees of the equator on the near side".^[100] Richard Orloff and David M. Harland, in their sourcebook on Apollo, stated that "the descent stage was left in the low orbit, but perturbations by 'mascons' would have caused this to decay, sending the stage to crash onto the lunar surface".^[101]

Images

• 
  The S-IC first stage in the VAB
• 
  Apollo 10 during rollout
• 
  The crew poses with their launch vehicle; left to right, Cernan, Young, Stafford.
• 
  Crew boarding the command module before launch
• 
  Apollo 10 view of Earthrise
• 
  CSM Charlie Brown
• 
  Apollo Lunar Module Snoopy about to dock with the command module
• 
  Necho crater on the far side of the Moon
• 
  High-albedo swirls within unnamed crater east of Firsov

See also

• List of artificial objects on the Moon
• List of vehicle speed records

Notes

References

Bibliography

• Apollo 10 Mission Report (PDF). Scientific and Technical Information Branch, NASA. 1969. Archived (PDF) from the original on October 9, 2022.
• Apollo 10 Press Kit (PDF). NASA. May 7, 1969. Release No. 69-68. Archived (PDF) from the original on October 9, 2022.
• Brooks, Courtney G.; Grimwood, James M.; Swenson, Loyd S. Jr. (1979). Chariots for Apollo: A History of Manned Lunar Spacecraft (PDF). NASA History Series. Scientific and Technical Information Branch,
  OCLC 4664449. NASA SP-4205. Archived
  (PDF) from the original on October 9, 2022.
• OCLC 321015054
  .
• OCLC 611666234
  .
• OCLC 539472915
  .
• OCLC 436030244
  .
• OCLC 883606901
  .
• Nelson, Craig (2009). Rocket Men: The Epic Story of the First Men on the Moon.
  OCLC 1336245311
  .
• Orloff, Richard W. (2004) [First published 2000]. "Apollo by the Numbers: A Statistical Reference". NASA History Division, Office of Policy and Plans (PDF). NASA History Series.
  OCLC 651892628. NASA SP-2000-4029. Archived
  (PDF) from the original on October 9, 2022.
• Orloff, Richard W.;
  OCLC 315797584
  .
• OCLC 1301427286
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• OCLC 539191452
  .
• OCLC 488684300
  .

External links

Wikimedia Commons has media related to Apollo 10.

• "Apollo 10" at Encyclopedia Astronautica
• NSSDC Master Catalog at NASA
• Apollo 10 Flight Journal

NASA reports

• The Apollo Spacecraft: A Chronology Archived December 9, 2017, at the Wayback Machine NASA, NASA SP-4009
• "Apollo Program Summary Report" (PDF), NASA, JSC-09423, April 1975
• "Table 2-38. Apollo 10 Characteristics" from NASA Historical Data Book: Volume III: Programs and Projects 1969–1978 by Linda Neuman Ezell, NASA History Series (1988)

Multimedia

• Apollo 10: "To Sort Out the Unknowns" Official NASA/JSC documentary film, JSC-519 (1969)
• Apollo 10 16mm onboard film part 1, part 2 raw footage taken from Apollo 10 at the Internet Archive
• Mission Transcripts: Apollo 10 at NASA's
  Lyndon B. Johnson Space Center
• Images from Apollo 10 Archived May 17, 2008, at the Wayback Machine at NASA's Kennedy Space Center
• Apollo launch and mission videos at ApolloTV.net