Apollo 10

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Apollo 10
Apollo 10 Lunar Module.jpg
Apollo 10's Lunar Module, Snoopy, approaches the Command/Service Module Charlie Brown for redocking
Mission type F
Operator NASA [1]
  • CSM: 1969-043A
  • LM: 1969-043C
  • CSM: 3941
  • LM: 3948
Mission duration 8 days, 3 minutes, 23 seconds
Spacecraft properties
Launch mass 98,273 pounds (44,576 kg)
Landing mass 10,901 pounds (4,945 kg)
Crew size 3
  • CSM: Charlie Brown
  • LM: Snoopy
Start of mission
Launch date May 18, 1969, 16:49:00 (1969-05-18UTC16:49Z) UTC
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 109.6 kilometers (59.2 nmi)
Aposelene 113.0 kilometers (61.0 nmi)
Inclination 1.2 degrees
Period 2 hours
Lunar orbiter
Spacecraft component Command/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
Orbit parameters
Periselene 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


The Apollo 10 Prime Crew - GPN-2000-001163.jpg
Left to right: Cernan, Stafford, Young
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Apollo 10 was the fourth manned mission in the United States Apollo space program, and the second (after Apollo 8) to orbit the Moon. Launched on May 18, 1969, it was the F mission: a "dress rehearsal" for the first Moon landing, testing all of the components and procedures, just short of actually landing. The Lunar Module (LM) followed a descent orbit to within 8.4 nautical miles (15.6 km) of the lunar surface, at the point where powered descent for landing would normally begin. [2] Its success enabled the first landing to be attempted on the Apollo 11 mission two months later.

According to the 2002 Guinness World Records, Apollo 10 set the record for the highest speed attained by a manned vehicle: 39,897 km/h (11.08 km/s or 24,791 mph) on May 26, 1969, during the return from the Moon.

The mission's call signs included the names of the Peanuts characters Charlie Brown and Snoopy, which became Apollo 10's semi-official mascots. [3] Peanuts creator Charles Schulz also drew some mission-related artwork for NASA.


Position Astronaut
Commander Thomas P. Stafford
Third spaceflight
Command Module Pilot John W. Young
Third spaceflight
Lunar Module Pilot Eugene A. Cernan
Second spaceflight

Backup crew

Position Astronaut
Commander L. Gordon Cooper, Jr.
Command Module Pilot Donn F. Eisele
Lunar Module Pilot Edgar Mitchell

Support crew

Flight directors

Crew notes

Apollo 10, along with Apollo 11, were the only Apollo missions whose crew were all veterans of spaceflight. Thomas P. Stafford had flown on Gemini 6 and Gemini 9; John W. Young had flown on Gemini 3 and Gemini 10, and Eugene A. Cernan had flown with Stafford on Gemini 9.

In addition, Apollo 10 was the only Saturn V flight from Launch Complex 39B, as preparations for Apollo 11 at LC-39A had begun in March almost immediately after Apollo 9's launch.

They were also the only Apollo crew all of whose members went on to fly subsequent missions aboard Apollo spacecraft: Young later commanded Apollo 16, Cernan commanded Apollo 17 and Stafford commanded the U.S. vehicle on the Apollo–Soyuz Test Project. It was on this flight that John Young became the first human to fly solo around the Moon, while Stafford & Cernan flew the LM in lunar orbit as part of the preparations for Apollo 11.

The Apollo 10 crew are also the humans who have traveled the farthest away from home, some 408,950 kilometers (220,820 nmi) from their homes and families in Houston. [4] While most Apollo missions orbited the Moon at the same 111 kilometers (60 nmi) from the lunar surface, the distance between the Earth and Moon varies by about 43,000 kilometers (23,000 nmi), between perigee and apogee, throughout the year, and the Earth's rotation make the distance to Houston vary by another 12,000 kilometers (6,500 nmi) each day. The Apollo 10 crew reached the farthest point in their orbit around the far side of the Moon at about the same time Earth's rotation put Houston nearly a full Earth diameter away. [5]

By the normal rotation in place during Apollo, the backup crew would have been scheduled to fly on Apollo 13. However, Alan Shepard was given the Apollo 13 command slot instead. L. Gordon Cooper, Jr., Commander of the Apollo 10 backup crew, was enraged and resigned from NASA. Later, Shepard's crew was forced to switch places with Jim Lovell's tentative Apollo 14 crew. [6]

Deke Slayton wrote in his memoirs that Cooper and Donn F. Eisele were never intended to rotate to another mission as both were out of favor with NASA management for various reasons (Cooper for his lax attitude towards training and Eisele for incidents aboard Apollo 7 and an extramarital affair) and were assigned to the backup crew simply because of a lack of qualified manpower in the Astronaut Office at the time the assignment needed to be made. Cooper, Slayton noted, had a very small chance of receiving the Apollo 13 command if he did an outstanding job with the assignment, which he did not. Eisele, despite his issues with management, was always intended for future assignment to the Apollo Applications Program (which was eventually cut down to only the Skylab component) and not a lunar mission. [7]


Earthrise video captured by Apollo 10 crew

This dress rehearsal for a Moon landing brought the Apollo Lunar Module to 8.4 nautical miles (15.6 km) from the lunar surface, at the point where powered descent would begin on the actual landing. Practicing this approach orbit would refine knowledge of the lunar gravitational field [8] needed to calibrate the powered descent guidance system [9] to within 1 nautical mile (1.9 km) (LR altitude update lock)[ further explanation needed] needed for a landing. Earth-based observations, unmanned spacecraft, and Apollo 8 had respectively allowed calibration to within 200 nautical miles (370 km), 20 nautical miles (37 km), and 5 nautical miles (9.3 km). Except for this final stretch, the mission was designed to duplicate how a landing would have gone, both in space and for ground control, putting NASA's flight controllers and extensive tracking and control network through a rehearsal.

Mission parameters

  • Mass: CSM 63,648 pounds (28,870 kg); LM 30,735 pounds (13,941 kg)

Earth parking orbit

Lunar orbit

LM – CSM docking

  • Undocked: May 22, 1969 – 19:00:57 UTC
  • Redocked: May 23, 1969 – 03:11:02 UTC

LM closest approach to lunar surface

  • May 22, 1969, 21:29:43 UTC

On May 22, 1969 at 20:35:02 UTC, a 27.4 second LM Descent Propulsion System burn inserted the LM into a descent orbit of 60.9 by 8.5 nautical miles (112.8 by 15.7 km) so that the resulting lowest point in the orbit occurred about 15° from lunar landing site 2 (the Apollo 11 landing site). The lowest measured point in the trajectory was 47,400 feet (14.4 km) above the lunar surface at 21:29:43 UTC. [10]

Mission highlights

Shortly after trans-lunar injection, Young performed the transposition, docking, and extraction maneuver, separating the Command/Service Module (CSM) from the S-IVB stage, turning around, and docking its nose to the top of the Lunar Module (LM), before separating from the S-IVB. Apollo 10 was the first mission to carry a color television camera inside the spacecraft, and made the first live color TV transmissions from space.

LM Snoopy containing Stafford and Cernan, as inspected by Young after separation from Charlie Brown

After reaching lunar orbit three days later, Young remained in the Command Module (CM) Charlie Brown while Stafford and Cernan entered the LM Snoopy and flew it separately. The LM crew performed the descent orbit insertion maneuver by firing their descent engine, and tested their craft's landing radar as they approached the 50,000-foot (15,000-meter) altitude where powered descent would begin on Apollo 11. They surveyed the landing site in the Sea of Tranquility, then separated the descent stage and fired the ascent engine to return to Charlie Brown. The descent stage was left in orbit, but eventually crashed onto the lunar surface because of the Moon's non-uniform gravitational field; its location was not tracked.

Upon descent stage separation and ascent engine ignition, the Lunar Module began to roll violently because the crew accidentally duplicated commands into the flight computer which took the LM out of abort mode, the correct configuration for this maneuver. [11] The live network broadcasts caught Cernan and Stafford uttering several expletives before regaining control of the LM. Cernan has said he observed the horizon spinning eight times over, indicating eight rolls of the spacecraft under ascent engine power. While the incident was downplayed by NASA, the roll was just several revolutions from being unrecoverable, which would have resulted in the LM crashing into the lunar surface. [11]

The ascent stage was loaded with the amount of fuel 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. The fueled LM weighed 30,735 pounds (13,941 kg), compared to 33,278 pounds (15,095 kg) for the Apollo 11 LM which made the first landing. [12] 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." [13] [14] In his own memoir, Cernan wrote "Our lander, LM-4...was still too heavy to guarantee safe margins for a moon landing." [15]

After being jettisoned, Snoopy's ascent stage engine was fired to fuel depletion, sending it on a trajectory past the Moon into a heliocentric orbit. [8] [16] The Apollo 11 ascent stage was left in lunar orbit to eventually crash; all subsequent ascent stages were intentionally steered into the Moon to obtain readings from seismometers placed on the surface, except for the one on Apollo 13, which did not land but was used as a "life boat" to get the crew back to Earth, and burned up in Earth's atmosphere. [16] Snoopy's ascent stage orbit was not tracked after 1969, and its current location is unknown. In 2011, a group of amateur astronomers in the UK started a project to search for it. [17] [18]

Splashdown occurred in the Pacific Ocean on May 26, 1969, at 16:52:23 UTC, about 400 nautical miles (740 km) east of American Samoa. The astronauts were recovered by USS Princeton, and subsequently flown to Pago Pago International Airport in Tafuna for a greeting reception, before being flown on a C-141 cargo plane to Honolulu.

After Apollo 10, NASA required astronauts to choose more "dignified" names for their Command and Lunar Modules. This proved unenforceable: Apollo 16 astronauts Young, Mattingly and Duke chose Casper, as in Casper the Friendly Ghost, for their Command Module name. The idea was to give children a way to identify with the mission by using humor. [19] [20]

Hardware disposition

The Command Module Charlie Brown is currently on loan to the Science Museum in London, where it is on display. Charlie Brown's Service Module (SM) was jettisoned just before re-entry and burned up in the Earth's atmosphere.

After the insertion into trans-Lunar orbit, the Saturn IVB third stage was accelerated past Earth escape velocity and became a derelict object where it would continue to orbit the Sun for many years. As of 2015, it remains in orbit. [21]

Mission insignia

Apollo 10 space-flown silver Robbins medallion

The shield-shaped emblem for the flight 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 significant 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. [22]

'Space Music mystery'

In February 2016 Discovery Channel broadcast a TV show suggesting that the mission witnessed mysterious or alien signals while on the far side of the Moon. [23] The astronomers mention the odd whistling sound that lasted nearly an hour. It was speculated that this is an evidence for UFO coverup. According to space journalist James Oberg the sound was most probably radio interference between the Command Module and the Lunar Module landing vehicles. Describing it as "outer-space type music" was most probably due to priming, as suggested by Benjamin Radford. [24]



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