The Fifth Mission:

The First Lunar Landing

16 July–24 July 1969

Background

Apollo 11 was a Type G mission, a piloted lunar landing demonstration. The primary objective of the Apollo program was to perform a piloted lunar landing and return safely to Earth.

It was only the second time an all-experienced crew had flown an American mission (the first was Apollo 10), and it would be the last until space shuttle mission STS-26 nearly two decades later.

The crew members for this historic mission were Neil Alden Armstrong, commander; Lt. Colonel Michael Collins (USAF), command module pilot; and Colonel Edwin Eugene “Buzz” Aldrin, Jr. (USAF), lunar module pilot.

Selected as an astronaut in 1962, Armstrong had been the first civilian ever to command an American space mission when he was command pilot of Gemini 8, which featured the first-ever docking of two vehicles in space. Apollo 11 made him the first civilian to command two missions. Armstrong was born 5 August 1930 in Wapakoneta, Ohio, and was 38 years old at the time of the Apollo 11 mission. He received a B.S. in aeronautical engineering from Purdue University in 1955 and an M.S. in aerospace engineering from the University of Southern California in 1970, following the Apollo mission. His backup was Captain James Arthur Lovell, Jr. (USN).

Collins had been pilot of Gemini 10. He was born 31 October 1930 in Rome, Italy, and was 38 years old at the time of the Apollo 11 mission. Collins received a B.S. from the U.S. Military Academy in 1952 and was selected as an astronaut in 1963. His backup was Lt. Colonel William Alison Anders (USAF).

Aldrin had been pilot of Gemini 12. He was born 20 January 1930 in Montclair, New Jersey, and was 39 years old at the time of the Apollo 11 mission. Aldrin received a B.S. in mechanical engineering from the U.S. Military Academy in 1951 and an Sc.D. in astronautics from the Massachusetts Institute of Technology in 1963. Also in 1963, he was selected as an astronaut. Aldrin has the distinction of being the first astronaut with a doctorate to fly in space. His backup was Fred Wallace Haise, Jr.

The capsule communicators (CAPCOMs) for the mission were Major Charles Moss Duke, Jr. (USAF), Lt. Commander Ronald Ellwin Evans (USN), Lt. Commander Bruce McCandless II (USN), Lovell, Anders, Lt. Commander Thomas Kenneth “Ken” Mattingly II (USAF), Haise, Don Leslie Lind, Ph. D., Owen Kay Garriott, Jr., Ph. D., and Harrison Hagan “Jack” Schmitt, Ph. D. The support crew were Mattingly, Evans, Major William Reid Pogue (USAF), and John Leonard “Jack” Swigert, Jr. The flight directors were Clifford E. Charlesworth and Gerald D. Griffin (first shift), Eugene F. Kranz (second shift), and Glynn S. Lunney (third shift).

The Apollo 11 launch vehicle was a Saturn V, designated SA-506. The mission also carried the designation Eastern Test Range #5307. The CSM was designated CSM-107 and had the call-sign “Columbia.” The lunar module was designated LM-5 and had the call-sign “Eagle.”

Possible landing sites for Apollo 11 were under study by NASA’s Apollo Site Selection Board for more than two years. Thirty sites were originally considered, but the list was shortened to three for the first lunar landing. Selection of the final sites was based on high-resolution photographs taken by the Lunar Orbiter satellite, plus close-up photographs and surface data provided by the Surveyor spacecraft, which landed on the Moon.

The original sites were located on the visible side of the Moon, within 45° east and west of the Moon’s center and 5° north and south of its equator. The final site choices were based on the following factors:

Smoothness: Relatively few craters and boulders.

Approach: No large hills, high cliffs, or deep craters that could cause incorrect altitude signals to the lunar module landing radar.

Propellant Requirements: Least potential expenditure of spacecraft propellants.

Recycling: Effective launch preparation recycling if the countdown were delayed.

Free Return: Sites within reach of the spacecraft launched on a free return translunar trajectory.

Slope: Less than 2° slope in the approach path and landing area.

There were a number of considerations which determined the launch windows for a lunar landing mission. These considerations included illumination conditions at launch, launch pad azimuth, translunar injection geometry, sun elevation angle at the lunar landing site, illumination conditions at Earth splashdown, and the number and location of the lunar landing sites.

The time of a lunar landing was determined by the location of the lunar landing site and by the acceptable range of sun elevation angles. The range of these angles was from 5° to 14° and in a direction from east to west. Under these conditions, visible shadows of craters would aid the crew in recognizing topographical features. When the sun angle approached the descent angle, the mean value of which was 16°, visual resolution would be degraded by a “washout” phenomenon where backward reflectance was high enough to eliminate contrast. Sun angles above the flight path were not as desirable because shadows would not be readily visible unless the sun was significantly outside the descent plane. In addition, higher sun angles (greater than 18°) could be eliminated from consideration by planning the landing one day earlier where the lighting is at least 5°. Because lunar sunlight incidence changed about 0.5° per hour, the sun elevation angle restriction established a 16-hour period, which occurred every 29.5 days, when landing at a given site could be attempted. The number of Earth-launch opportunities for a given lunar month was equal to the number of candidate landing sites.

The time of launch was primarily determined by the allowable variation in launch pad azimuth and by the location of the Moon at spacecraft arrival. The spacecraft had to be launched into an orbital plane that contained the position of the Moon and its antipode at spacecraft arrival. A 34° launch pad azimuth variation afforded a launch period of 4 hours 30 minutes. This period was called the “daily launch window,” the time when the direction of launch was within the required range to intercept the Moon.

Two launch windows occurred each day. One was available for a translunar injection out of Earth orbit in the vicinity of the Pacific Ocean, and the other was in the vicinity of the Atlantic Ocean. The injection opportunity over the Pacific Ocean was preferred because it usually permitted a daytime launch.

Launch Preparations

The terminal countdown started at T-28 hours, 21:00:00 GMT on 14 July. The scheduled holds of 11 hours at T-9 hours and 1 hour 32 minutes at T-3 hours 30 minutes were the only holds initiated. The start of the S-II stage LH2 loading was delayed 25 minutes due to a communications problem in the Pad Terminal Connection Room. However, the lost time was recovered during the scheduled countdown hold at T-3 hours 30 minutes.

A high-pressure cell in the Atlantic Ocean off the North Carolina coast, along with a weak trough of low pressure located in the northeastern Gulf of Mexico, caused light southerly surface winds and brought moisture into the Cape Kennedy area. These circumstances contributed to the cloudy conditions and distant thunderstorms observed at launch time. Cumulus clouds covered 10 percent of the sky (base 2,400 feet), altocumulus covered 20 percent (base 15,000 feet), and cirrostratus covered 90 percent (base not recorded); the temperature was 84.9° F; the relative humidity was 73 percent; and the barometric pressure was 14.798 lb/in2. The winds, as measured by the anemometer on the light pole 60.0 feet above ground at the launch site, measured 6.4 knots at 175° from true north.

Ascent Phase

Apollo 11 was launched from Kennedy Space Center Launch Complex 39, Pad A, at a Range Zero time of 13:32:00 GMT (09:32:00 a.m. EDT) on 16 July 1969. The planned launch window for Apollo 11 extended to 17:54:00 GMT to take advantage of a sun elevation angle on the lunar surface of 10.8°.

Between 000:00:13.2 and 000:00:31.1, the vehicle rolled from a launch pad azimuth of 90° to a flight azimuth of 72.058°. The S-IC engine shut down at 000:02:41.63, followed by S-IC/S-II separation and S-II engine ignition.

The S-II engine shut down at 000:09:08.22, followed by separation from the S-IVB, which ignited at 000:09:12.2. The first S-IVB engine cutoff occurred at 000:11:39.33, with deviations from the planned trajectory of only -0.6 ft/sec in velocity and only -0.1 n mi in altitude.

The S-IC stage impacted the Atlantic Ocean at 000:09:03.70 at latitude 30.212° north and longitude 74.038° west, 357.1 n mi from the launch site. The S-II stage impacted the Atlantic Ocean at 000:20:13.7 at latitude 31.535° north and longitude 34.844° west, 2,371.8 n mi from the launch site.

The maximum wind conditions encountered during ascent were 18.7 knots at 297° from true north at 37,400 feet, with a maximum wind shear of 0.0077 sec-1 at 48,490 feet.

Parking orbit conditions at insertion, 000:11:49.33 (S-IVB cutoff plus 10 seconds to account for engine tailoff and other transient effects), showed an apogee and perigee of 100.4 by 98.9 n mi, and an inclination of 32.521°, a period of 88.18 minutes, and a velocity of 25,567.8 ft/sec. The apogee and perigee were based upon a spherical Earth with a radius of 3,443.934 n mi.

The international designation for the CSM upon achieving orbit was 1969-059A, and the S-IVB was designated 1969-059B. After undocking at the Moon, the LM ascent stage would be designated 1969-059C and the descent stage 1969-059D.

Earth Orbit Phase

After in-flight systems checks, the 346.83-second translunar injection maneuver (second S-IVB firing) was performed at 002:44:16.20. The S-IVB engine shut down at 002:50:03.03, and translunar injection occurred ten seconds later, after 1.5 Earth orbits lasting 2 hours 38 minutes 23.73 seconds, at a velocity of 35,545.6 ft/sec.

Translunar Phase

At 003:15:23.0, the CSM was separated from the S-IVB stage and transposed and docked with the LM at 003:24:03.7. The docked spacecraft were ejected from the S-IVB at 004:17:03.0, and a 2.93-second separation maneuver was performed at 004:40:01.72. A ground command for propulsive venting of residual propellants targeted the S-IVB to go past the Moon and into solar orbit. The lunar radius of closest approach of the S-IVB to the Moon was 2,763 n mi at 20:14 GMT on 19 July at 078:42. The point of closest approach to the lunar surface was 1,825 n mi. The orbital parameters after passing the from the lunar sphere of influence resulted in a solar orbit with an aphelion and perihelion of 82.000 million by 72.520 million n mi, a semi-major axis of 77,260 million n mi, an inclination to the ecliptic of 0.3836°, and a period of 342 days. The velocity increase relative to Earth from the lunar encounter was 0.367 n mi/sec.

An unscheduled 16-minute television transmission was recorded at the Goldstone Tracking Station starting at 010:32. The tape was played back at Goldstone and transmitted to Houston starting at 011:26.

Trajectory parameters after the translunar injection firing were nearly perfect. A 3.13-second midcourse correction of 20.9 ft/sec was made at 026:44:58.64 during the translunar phase. During the remaining periods of free-attitude flight, passive thermal control, a rotating “barbecue”-like maneuver, was used to maintain spacecraft temperatures within desired limits.

An unscheduled 50-minute television transmission was accomplished at 030:28, and a 36-minute scheduled transmission began at 033:59. The crew initiated a 96-minute color television transmission at 055:08. The picture resolution and general quality were exceptional. The coverage included the interior of the CM and LM and views of the exterior of the CM and Earth. Excellent views of the crew accomplishing probe and drogue removal, spacecraft tunnel hatch opening, LM housekeeping, and equipment testing were broadcast.

During the latter transmission, the commander and lunar module pilot transferred to the LM at 055:30 to make the initial inspection and preparations for the systems checks that would be made shortly after lunar orbit insertion. They returned to the CM at 057:55.

At 075:49:50.37, at an altitude of 86.7 n mi above the Moon, the service propulsion engine was fired for 357.53 seconds to insert the spacecraft into a lunar orbit of 169.7 by 60.0 n mi. The translunar coast had lasted 73 hours 5 minutes 34.83 seconds.

Lunar Orbit/Lunar Surface Phase

During the second lunar orbit, at 078:20, a scheduled live color television transmission was accomplished, providing spectacular views of the lunar surface and the approach path to landing site 2.

After two revolutions and a navigation update, a second service propulsion retrograde burn was made. The 16.88-second maneuver occurred at 080:11:36.75 and circularized the orbit at 66.1 by 54.5 n mi. The commander and lunar module pilot then transferred to the LM and, for about two hours, performed various housekeeping functions, a voice and telemetry test, and an oxygen purge system check. LM functions and consumables checked out well. Additionally, both cameras were checked and verified operational. The pair then returned to the CSM. At 095:20, they returned to the LM to perform a thorough check of all LM systems in preparation for descent.

Undocking occurred at 100:12:00 at an altitude of 62.9 n mi. This was followed by a CSM reaction control system 9.0-second separation maneuver at 100:39:52.9 directed radially downward toward the center of the Moon as planned. The LM descent orbit insertion maneuver was performed with a 30.0-second firing of the descent propulsion system at 101:36:14.0, which put the LM into an orbit of 58.5 by 7.8 n mi.

The 756.39-second powered descent engine burn was initiated at 102:33:05.01. The time was as planned, but the position at which powered descent initiation occurred was about 4 n mi farther downrange than expected. This resulted in the landing point being shifted downrange about 4 n mi.

The first of five alarms occurred at 102:38:22 because of a computer overload, but it was determined that it was safe to continue the landing. The crew checked the handling qualities of the LM at 102:41:53 and switched to automatic guidance ten seconds later. The landing radar switched to “low-scale” at 102:42:19 as the LM descended below 2,500 feet altitude. The LM was maneuvered manually 1,100 feet down range from the preplanned landing point during the final 2.5 minutes of descent. The final alarm occurred at 102:42:58, followed by the red-line low-level fuel quantity light at 102:44:28, just 72 seconds before landing.

During the final approach, the commander noted that the landing point toward which the spacecraft was headed was in the center of a large crater that appeared extremely rugged, with boulders of five to ten feet in diameter and larger. Consequently, he switched to manual attitude control to translate beyond the rough terrain area.

The LM landed on the Moon at 20:17:39 GMT (16:17:39 EDT) on 20 July 1969 at 102:45:39.9. Engine shutdown occurred 1.5 seconds later. The LM landed in Mare Tranquilitatis (Sea of Tranquility) at latitude 0.67408° north and longitude 23.47297° east and 22,500 feet west of the center of the landing ellipse. Approximately 45 seconds of firing time remained at landing.[1]

For the first two hours on the lunar surface, the crew performed a checkout of all systems, configured the controls for lunar stay, and ate their first post-landing meal. A rest period had been planned to precede the extravehicular activity of exploring the lunar surface but was not needed.

After donning the back-mounted portable life support and oxygen purge systems, the commander prepared to exit the LM. The forward hatch was opened at 109:07:33 and the commander exited at 109:19:16. While descending the LM ladder, he deployed the Modular Equipment Stowage Assembly from the descent stage. A camera in the module provided live television coverage as he descended. The commander’s left foot made first contact with the lunar surface at 02:56:15 GMT on 21 July (22:56:15 EDT on 20 July) at 109:24:15. His first words on the lunar surface were, “That’s one small step for man, one giant leap for mankind.”

The commander made a brief check of the LM exterior, indicating that penetration of the footpads was only about three to four inches and collapse of the LM footpad strut was minimal. He reported sinking about one-eighth inch into the fine, powdery surface material, which adhered readily to his lunar boots in a thin layer. There was no crater from the effects of the descent engine, and about one foot of clearance was observed between the engine bell and the lunar surface. He also reported that it was quite dark in the shadows of the LM, which made it difficult for him to see his footing.

He then collected a contingency sample of lunar soil from the vicinity of the LM ladder. He reported that although loose material created a soft surface, as he dug down six or eight inches he encountered very hard, cohesive material.

The commander then photographed the lunar module pilot as he exited at 109:37:57 and descended to the lunar surface at 109:43:16.

Following the LMP’s descent to the surface, the crew unveiled a plaque mounted on the strut behind the ladder, and read its inscription to their worldwide television audience. The plaque read:

HERE MEN FROM THE PLANET EARTH

FIRST SET FOOT UPON THE MOON

JULY 1969, A.D.

WE CAME IN PEACE FOR ALL MANKIND.

The plaque featured the signatures of the three Apollo crew members and President Richard M. Nixon. Next, the commander removed the television camera from the descent stage, obtained a panorama, and placed the camera on its tripod in position to view the subsequent surface extravehicular operations.

The lunar module pilot deployed the solar wind composition experiment on the lunar surface in direct sunlight and to the north of the LM as planned.

At 110:09:43, the pair erected a three-by-five-foot United States flag on an eight-foot aluminum staff. A conversation between President Richard M. Nixon and the LM crew was held at 110:16:30. The conversation originated from the White House and included congratulations and good wishes.

During the environmental evaluation, the lunar module pilot indicated that he had to be careful of his center of mass in maintaining balance. He noted that the LM shadow had no significant effect on his backpack temperature. He also noted that his agility was better than expected and that he was able to move about with great ease. Both crew members indicated that their mobility throughout this period exceeded all expectations. Also, indications were that metabolic rates were much lower than pre-mission estimates.

The commander collected a bulk sample, consisting of assorted surface material and rock chunks, and placed them in a sample return container. The crew then inspected the LM, finding the quads, struts, skirts, and antennas in satisfactory condition.

The passive seismic experiment package and laser ranging retroreflector were deployed south of the LM. Excellent PSEP data were obtained, including detection of the crew walking on the surface and later their movements inside the LM. The crew then collected more lunar samples, two core samples and about 20 pounds of discretely selected material. The LMP had to exert considerable force to drive the core tubes six to eight inches into the lunar surface.

The solar wind experiment was recovered after 1 hour 17 minutes exposure. The transfer of lunar sample containers to the LM began at 111:23. The crew entered the LM and closed the hatch at 111:39:13, thus ending the first human exploration of the Moon. The total time spent outside the LM was 2 hours 31 minutes 40 seconds; the total distance traveled was about 3,300 feet (1 km); and the collected samples totaled 47.51 pounds (21.55 kg).[2] The farthest point traveled from the LM was 200 feet (60 m), when the commander visited a crater 108 feet in diameter (33 m) near the end of the extravehicular period.

Ignition of the ascent stage engine for liftoff occurred at 17:54:00 GMT on 21 July at 124:22:00.79. The LM had been on the lunar surface for 21 hours 36 minutes 20.9 seconds. An orbit of 48.0 by 9.4 n mi was achieved at 124:29:15.67, 434.88 seconds after liftoff.

Several rendezvous sequence maneuvers were required before docking could occur 3.5 hours later. A 47.0-second coelliptic orbit maneuver at 125:19:35 raised the orbit to 49.3 by 45.7 n mi. A 17.8-second constant delta height maneuver at 126:17:49.6 lowered the orbit to 47.4 by 42.1 n mi. A 22.7-second terminal phase initiate maneuver at 127:03:51.8 brought the ascent stage to an orbit of 61.7 by 43.7 n mi. The 28.4-second terminal phase maneuver at 127:46:09.8 finalized the orbit at 63.0 by 56.5 for docking of the ascent stage and the CSM at 128:03:00.0. The two craft had been undocked for exactly 27 hours 51 minutes.

In the process of maneuvering the LM to docking attitude, while avoiding direct sunlight in the forward window, the platform inadvertently reached gimbal lock, causing a brief and unexpected tumbling motion of the LM. A quick recovery was made and the docking was completed using the abort guidance system for attitude control.

After transfer of the crew and samples to the CSM, the ascent stage was jettisoned at 130:09:31.2 at an altitude of 61.6 n mi, and the CSM was prepared for transearth injection. A 7.2-second maneuver was made at 130:30:01.0 to separate the CM from the ascent stage; it resulted in an orbit of 62.7 by 54.0 n mi. The ascent stage would remain in lunar orbit for an indefinite period.

The 151.41-second transearth injection maneuver was performed at 135:23:42.28 at an altitude of 52.4 n mi. A nominal injection was achieved at 135:26:13.69 after 30 lunar orbits lasting 59 hours 30 minutes 25.79 seconds, at a velocity of 8,589.0 ft/sec.

Transearth Phase

As in translunar flight, only one midcourse correction was required, a 10.0-second, 4.8-ft/sec maneuver, at 150:29:57.4. Passive thermal control was exercised for most of the transearth coast.

An 18-minute television transmission was initiated at 155:36; it featured a demonstration of the effect of weightlessness on food and water, as well as brief scenes of the Moon and Earth. The final color television broadcast was made at 177:32. The 12.5-minute transmission featured a message of appreciation by each crew member to all the people who helped make the mission possible.

Recovery

Because of inclement weather in the planned recovery area, the splashdown point was moved 215 n mi down range. The weather in the new area was excellent: visibility 12 miles, waves to 3 feet, and wind 16 knots.

The service module was jettisoned at 194:49:12.7, and the CM entry followed an automatic entry profile. The command module reentered Earth’s atmosphere (400,000 feet altitude) at 195:03:05.7 at a velocity of 36,194.4 ft/sec, following a transearth coast of 59 hours 36 minutes 52.0 seconds.

The parachute system effected splashdown of the CM in the Pacific Ocean at 16:50:35 GMT (12:50:35 EDT) on 24 July. Mission duration was 195:18:35. The impact point was 1.7 n mi from the target point and 13 n mi from the recovery ship U.S.S. Hornet. The splashdown site was estimated to be latitude 13.30° north and longitude 169.15° west.

After splashdown, the CM assumed an apex-down flotation attitude but was successfully returned to the normal flotation position in 7 minutes 40 seconds by the inflatable bag uprighting system. After splashdown, the crew donned biological isolation garments and exited the CM into a rubber boat, where they were scrubbed down with an iodine solution to protect against “lunar germs.” They were then retrieved by helicopter and taken to the primary recovery ship, where they arrived 63 minutes after splashdown. The CM was recovered 125 minutes later. The estimated CM weight at splashdown was 10,873.0 pounds, and the estimated distance traveled for the mission was 828,743 n mi.

The crew, the recovery physician, and a recovery technician, along with lunar samples, entered the Mobile Quarantine Facility aboard the recovery ship for transport to the Lunar Receiving Laboratory in Houston.

The CM and Mobile Quarantine Facility were offloaded from the Hornet in Hawaii 00:15 GMT on 27 July. The Mobile Quarantine Facility was loaded aboard a C-141 aircraft and flown to Houston, where it arrived at 06:00 GMT on 28 July.

The crew arrived at the Lunar Receiving Laboratory four hours later. The safing of the CM pyrotechnics was completed at 02:05 GMT on 27 July. The CM was taken to Ford Island for deactivation, after which it was transferred to Hickam Air Force Base, Hawaii, and flown on a C-133 aircraft to Houston, where it arrived at 23:17 GMT on 30 July.

The crew and spacecraft were released from quarantine on 10 August. On 14 August the spacecraft was delivered to the North American Rockwell Space Division facility in Downey, California, for postflight analysis.

All spacecraft systems performed satisfactorily. With the completion of the Apollo 11 mission, the national objective of landing humans on the Moon and returning them safely to Earth before the end of the decade was accomplished.

Conclusions

The Apollo 11 mission, including a piloted lunar landing and surface exploration, was conducted with skill, precision, and relative ease. The excellent performance of the spacecraft in the preceding four missions and the thorough planning in all aspects of the program permitted the safe and efficient execution of this mission. The following conclusions were made from an analysis of post-mission data:

The effectiveness of pre-mission training was reflected in the skill and precision with which the crew executed the lunar landing. Manual control while maneuvering to the desired landing point was satisfactorily exercised.

The planned techniques involved in the guidance, navigation, and control of the descent trajectory were good. Performance of the landing radar met all expectations in providing the information required for descent.

The extravehicular mobility units were adequately designed to enable the crew to conduct the planned activities. Adaptation to 1/6 g was relatively quick, and mobility on the lunar surface was easy.

The two-person pre-launch checkout and countdown for ascent from the lunar surface were well planned and executed.

The timeline activities for all phases of the lunar landing mission were well within the crew’s capability to perform the required tasks.

The quarantine operation from spacecraft landing until release of the crew, spacecraft, and lunar samples from the Lunar Receiving Laboratory was accomplished successfully and without any violation of the quarantine.

No microorganisms of extraterrestrial origin were recovered from either the crew or the spacecraft.

Hardware problems, as experienced on previous piloted missions, did not unduly hamper the crew or compromise crew safety or mission objectives.

The Mission Control Center and the Manned Space Flight Network proved to be adequate for controlling and monitoring all phases of flight, including the descent, surface activities, and ascent phases of the mission.

[1] According to the Apollo 11 Mission Report (MSC-00171), post?ight analysis revealed that there was 45 seconds of fuel remaining at lunar touchdown, not as little as 7 seconds as indicated by other sources.

[2] Official total in kilograms as determined by the Lunar Receiving Laboratory in Houston.