Extravehicular Activity (EVA), where space travelers exit their spacecraft to perform tasks in the vacuum of space, has become a fairly routine and necessary part of space operations. Today, EVAs are regularly performed by the crew of the International Space Station (ISS) to set up and recover experiments, repair and maintain ISS systems as well as integrate new components of the station. Since the first EVA was performed by Soviet cosmonaut Alexei Leonov over a half century ago during the Voskhod 2 mission (see “The Mission of Voskhod 2”), well over 200 individuals have stepped out of their spacecraft to perform EVAs mainly from the US and Russia (or the now defunct USSR).

While the majority of these individuals performed EVAs from Earth-orbiting space stations like ISS and its predecessors or in connection with dozens of missions with the American Space Shuttle, a tiny minority performed them far from the Earth. The most memorable of these were EVAs of a dozen NASA astronauts on the lunar surface as part of the historic Apollo lunar landing missions between 1969 and 1972. Not as well known were EVAs which took place in deep space during the last three Apollo lunar flights as the crews were returning to the Earth. Instead of the Earth filling half the sky as it does during EVAs in orbit, our home world appeared as a distant crescent during these historic spacewalks. With the prospects of EVAs being performed in deep space as part of new missions to the Moon and beyond, it is worth reviewing the Apollo deep space EVAs.

The Apollo J-Series Missions

With the first four Apollo lunar landing missions eventually pushing the baseline spacecraft design to its practical limits, upgraded hardware was required to further the scientific exploration of the Moon. These upgrades were introduced with J-series missions starting with the flight of Apollo 15 in 1971. Both the Lunar Module (LM) and Command-Service Module (CSM) were upgraded to include more consumables to support longer stays on the lunar surface and in orbit as well as an array of additional equipment to aid in lunar studies. These upgrades increased the launch mass of the Apollo spacecraft by 2.4 metric tons necessitating changes to the Saturn V launch vehicle to improve its performance as well. One of the more memorable pieces of additional equipment carried by the J-series LM was the battery-powered Lunar Roving Vehicle (LRV) which allowed the pair of visiting astronauts to travel many kilometers across the lunar surface to explore far from the LM during visits which were now to last three days – twice the length of earlier Apollo landing missions.

While changes to the LM in support of surface exploration received a lot of attention, changes were also made to the CSM in order to meet a significantly expanded set of science objectives from lunar orbit. Sector I of the Apollo SM immediately behind the CM crew hatch, whose 8.5 cubic meter volume had been empty on earlier missions save for ballast and (after the Apollo 13 accident) a spare cryogenic oxygen tank, would now house the Scientific Instrument Module (SIM). The SIM consisted of a suite of instruments to study large swaths of the Moon from orbit. The first two J-series missions also carried the 36-kilogram Apollo Particles and Fields Subsatellite (PFS) which would be deployed from the SIM into lunar orbit to continue studying the lunar environment after the astronauts had departed for home (see “Vintage Micro: The Apollo Particles and Fields Subsatellites”).

While the mix of instruments carried by the SIM was altered for the last J-series mission, Apollo 17, all three missions incorporated a set of photographic cameras to map the lunar surface from orbit for the Apollo Orbital Science Photographic Team headed by Frederick J. Doyle of the US Geological Survey. The largest of these was the 152-kilogram 24-Inch Panoramic Camera which was based on Itek’s KA-80A aerial reconnaissance camera in use by the USAF. This camera used a rotating f/3.5 lens system with a 610 mm focal length to create photographs which covered an area 21.7 by 340 kilometers from a nominal 111-kilometer lunar orbit. Sets of overlapping images would be taken making stereo measurements of the scene being observed possible. With a resolution on the order of one meter, these photographs would be comparable to the best acquired of selected sites during NASA’s Lunar Orbiter missions of 1966 and 1967 (see the Lunar Orbiter page for descriptions of these missions and their hardware). About 2,000 meters of large format photographic film capable of recording 1,650 frames were carried in a 33-kilogram cassette.

Also carried by all three J-series missions was the 125-kilogram 3-Inch Mapping Camera built by Fairchild. This camera used a 76 mm, f/4.5 lens to record images on large format photographic film which covered an area of 170 by 170 kilometers from a nominal 111-kilometer orbit with a resolution of about 20 meters. A total of 460 meters of film allowed 3,600 frames of the lunar surface to be recorded. Also incorporated in this unit was a star camera which permitted the pointing of the Mapping Camera to be precisely determined. It used a 76 mm f/2.8 lens whose alignment with the Mapping Camera was precisely known to record images of star fields on 155 meters of 35 mm film. Both sets of film were carried in a common cassette with a mass of 16 kilograms.

In order for the exposed photographic film from these cameras to be returned to Earth for processing and analysis, an EVA had to be performed to remove them from the SIM and stow them inside of the CM with the crew. This task fell upon the J-series missions’ command module pilot (CMP) with the lunar module pilot (LMP) assisting at the crew hatch while the commander piloted the spacecraft and monitored its systems inside the CM. In order to aid the CMP during EVA, the J-series SM included a set of hand rails around the SIM to allow him to move from the CM and around the SIM. The SIM itself also incorporated a strategically placed foot restraint to free the astronaut’s hands so that he could more easily remove the pair of film cassettes from the cameras. During the EVA, two of the sets of reaction control engines on the SM used for attitude control which were closest to the SIM, Qauds A and B, would be deactivated to prevent them from firing while the CMP was nearby during the EVA.

For the EVA, the CMP wore a version of the then-new A7LB space suit first introduced for the Apollo 14 lunar surface EVAs. The main improvement of the A7LB suits from the A7L space suits employed during the earlier Apollo missions was the inclusion of a waist joint to provide greater mobility when the suit was pressurized. The A7LB-CMP variant of the suit to be worn by the CMP was essentially identical to the A7LB-EV worn by the Apollo astronauts on the Moon save for the exclusion of features to support lunar surface EVAs (e.g. attachment points for tools and other equipment) and was modified to interface with the Apollo CM. During the EVA, the CMP would wear the commander’s used lunar extravehicular visor assembly (which would be returned from the Moon with the crew) with its distinctive red stripe to help protect the A7LB-CMP’s bubble-like pressure helmet and shield the CMP from the Sun.

During the EVA, the CMP would wear a 7.4-meter tether to connect himself to the spacecraft via a panel added to the J-series CM interior near the crew hatch. In addition to securing the CMP to the spacecraft, this tether supplied the astronaut with oxygen and provided a communications link. In case a problem developed with the tether which prevented fresh oxygen from reaching the CMP, an oxygen purge system was carried behind the astronaut’s head which was identical in design to those carried by the Apollo astronauts during their lunar surface EVAs atop of their back pack-like Portable Life Support System (PLSS). This system consisted of a pair of oxygen bottles pressurized to 40,500 kilopascals which could supply 30 to 75 minutes of oxygen to the CMP. The “transearth EVA”, as it would be called, would take place during the first full day after the CSM had departed to Moon for home and last around one hour.

Apollo 15

The first J-series mission was Apollo 15 launched on July 26, 1971. The CMP who would perform the first transearth EVA during this mission was 39 year old USAF Major Alfred M. Worden. Al Worden graduated from the US Military Academy at West Point in 1955 and had been an instructor at the Aerospace Research Pilots School before being selected as part of NASA’s fifth group of astronauts in April 1966. The LMP who would be assisting Worden during the transearth EVA was USAF Lt. Colonel James B. Irwin who was also part of NASA’s fifth group of astronauts and, like Worden, was making his first spaceflight. The Apollo 15 commander was USAF Colonel David R. Scott – a veteran astronaut who had flown previously as the pilot on the Gemini 8 mission in 1966 (see “Gemini 8: The First Docking in Space”) and as the CMP for the Apollo 9 mission in 1969 which performed the first tests of the LM with a crew in low Earth orbit (see “Apollo 9: Giving the ‘Spider’ Wings“).

Since Worden was the first to make the transearth EVA, he was able to uncover a number of issues with the original EVA plans during training sessions in a neutral buoyancy tank (where astronauts simulated weightlessness in a large pool) and on board a modified KC-135 (where the aircraft, popularly known as the “Vomit Comet”, would repeatedly fly parabolic arcs to create weightless conditions for up to a half minute at a time). One of the more notable changes made to the EVA based on Worden’s experience was to the procedures to transfer the cassettes of exposed film from the SIM to the CM. Originally, a clothesline-like lanyard system was to be employed to move the cassettes to the LMP waiting at the crew hatch. Worden found that it was easier just to carry the cassettes himself one at a time to the CM and pass them on to Irwin after each had been removed from their cameras.

After a good start to the mission, the Apollo 15 CSM Endeavour docked with the LM Falcon entered lunar orbit on July 29, 1971 at 20:12:25 GMT. With the panel covering the SIM successfully jettisoned 4 hours and 25 minutes earlier (where it would fly past the Moon and into solar orbit), the first round of orbital science photography started just two hours after reaching orbit. The following day, Scott and Irwin entered Falcon and descended to the lunar surface to begin their three-day mission to explore the region around Hadley Rille. In the mean time, Al Worden started his duties in lunar orbit including executing an extensive science program which included the SIM instruments.

Falcon lifted off from the lunar surface with Scott, Irwin and 77 kilograms of lunar samples on board at 17:11:23 GMT on August 2. The LM ascent module rendezvoused and docked with Endeavour with Al Worden on board two hours later. The LM, now empty of its crew, samples and other gear required for the balance of the mission, was jettisoned at 01:04 GMT on August 3. The reunited Apollo 15 crew spent the next two days in lunar orbit completing their science program and deploying the PFS subsatellite. Endeavour ignited its main engine for TEI (Trans-Earth Injection) at 21:22:45 GMT on August 4 to start the three-day trip home.

Although the flight plan called for the 48-minute transearth EVA to take place at 15:34 GMT the next day after the astronauts’ first post-TEI sleep period, Al Worden spent a couple of hours before bedtime preparing the CM for the EVA to get a bit of a head start on the next day’s activities. With the cabin in good shape the next morning when the crew awoke, the crew had breakfast then worked methodically through their EVA checklists with the donning their A7LB space suits starting about an hour before the EVA. Despite the two-hour head start afforded by Worden’s efforts the previous evening, the crew finished their preparations on schedule taking extra time to make sure everything was perfect for the EVA.

With Scott at the controls of the CSM, the slow “barbeque roll” mode of the spacecraft (which helped even out solar heating during flight) was stopped so that the SIM was in sunlight. After depressurizing the cabin and performing suit integrity checks, the CM crew hatch was opened and Al Worden stepped out into space at 15:31:12 GMT on August 5 just a couple of minutes ahead of the prelaunch schedule. Worden’s first task was to set up a television camera on the end of a boom at the hatch so that ground controllers and the public could watch the activity at the SIM first hand starting about three minutes into the EVA.

Worden made three trips between the crew hatch and the SIM: the first two to retrieve the pair of film cassettes and hand them off to Jim Irwin while the third was to check out the condition of the SIM instruments themselves. During the transfer of the film cassettes, tasks proved to be easier than they had been in zero-g training back on Earth helping to speed along the process. During this last trip to the SIM to inspect the instruments, Worden was unable to find an obvious cause for the failure of Mapping Camera’s extend/retract mechanism (which was stuck in the extended position) and also noted that the 7.3-meter boom for the S-165 Mass Spectrometer experiment (designed to study the composition of the Moon’s tenuous atmosphere) had not fully retracted. Overall, the EVA went well and the only complaint was that Worden felt his tether was a bit short at times especially when he was at the far end of the SIM. Television transmissions from outside the CSM were ended at 16:02 GMT and the equipment returned to the cabin with Irwin’s help.

Al Worden ended his deep space EVA at 16:10:19 GMT after spending 39 minutes and 7 seconds outside the spacecraft – nine minutes less than had been scheduled. After securing the hatch, the cabin was repressurized with Worden using some oxygen in his now superfluous EVA oxygen purge system to help out. Scott then set the CSM back into its slow roll for thermal control. The first deep space EVA proved to be a complete success with the end of the Apollo 15 mission coming with a splashdown in the Pacific Ocean at 20:45:53 GMT on August 7, 1971.

Here is a video of the Apollo 15 transearth EVA television coverage:

Apollo 16

The CMP who would perform the transearth EVA during the second J-series mission, Apollo 16 launched on April 16, 1972, was US Navy Lt. Commander Thomas K. (Ken) Mattingly II. Ken Mattingly was a 36 year old rookie astronaut who entered military service in 1958 and flew various carrier-based aircraft. When he was chosen as part of the fifth group of NASA astronauts in 1966, he was a student at the Air Force Aerospace Research Pilot School. Mattingly was originally suppose to fly as the CMP on the ill-fated Apollo 13 mission but was replaced by his backup, John Swigert, just three days before launch because he had been exposed to German measles. The LMP of the Apollo 16 mission who would assist Mattingly during his EVA was USAF Lt. Colonel Charles M. Duke, Jr. who was also part of NASA’s fifth astronaut group making his first spaceflight as well. The mission commander was veteran astronaut US Navy Captain John W. Young. Young had previously flown as the pilot on the Gemini 3 mission in 1965 (see “The Mission of Gemini 3”), the command pilot of the Gemini 10 mission in 1966 (see “Gemini 10: Dual Rendezvous in Space”) and as the CMP for the Apollo 10 lunar mission in 1969 which served as a dress rehearsal for the successful Apollo 11 lunar landing mission (see “Apollo 10: The Adventure of Charlie Brown & Snoopy“).

As the Apollo 16 CSM Casper, with the LM Orion in tow, approached the Moon three days into the mission, the SIM cover was successfully jettisoned at 15:53:01 GMT on April 19, 1972 exposing the bay’s instruments to space. The combined Apollo 16 spacecraft entered lunar orbit at 20:28:42 GMT and the crew began their preparations for the lunar landing scheduled for the next day. Orion separated from Casper at 18:07:31 GMT on April 20 but an oscillation was noted in the secondary system which controlled the gimbal of the SM’s main engine as Casper was preparing to circularize its orbit to support science observations. The two spacecraft were subsequently maneuvered into a station keeping mode in lunar orbit as the problem with the SM was diagnosed by engineers back on Earth. Fortunately, 5¾ hours later, John Young and Charlie Duke were given the green light for landing and beginning their three-day mission to explore the Descartes Highlands while Ken Mattingly began his program of science experiments in orbit.

Young and Duke lifted off from the lunar surface at 01:25:47 GMT on April 24, 1972 and docked with the CSM with Mattingly on board just over two hours later. Once the crew had transferred to Casper along with 96 kilograms of lunar samples and assorted equipment required for the rest of the mission, the empty ascent stage of Orion was undocked at 20:54:12 GMT. Unfortunately, the extended mission in orbit was cut short by a day by Mission Control over concerns with the SM’s propulsion system gimbal curtailing further studies of the Moon from lunar orbit. The only major issues related to the SIM were with the 7.3-meter long boom of the S165 Mass Spectrometer which failed to retract upon command before TEI (and was subsequently jettisoned instead at 21:17:12 GMT) and the subsatellite which was deployed into a less than optimal orbit because Casper’s final orbit-shaping maneuver had been cancelled again due to the gimbal issue. TEI took place at 02:15:33 GMT on April 25.

During the beginning of their journey back home, the Apollo 16 crew performed experiments as well as some housekeeping duties including about an hour of prep work for the transearth EVA before starting their first post-TEI sleep period. After breakfast the next morning, the crew began their preparations in earnest for the EVA to come. This transearth EVA was scheduled to last about 70 minutes and included an extra task not performed during the Apollo 15 mission: the deployment and recovery of a microbial environment exposure device (MEED) on a boom that would be attached to the CM hatch. This was part of the M-191 Microbial Response in Space Environment experiment where representative types of microorganisms were exposed to space for ten minutes to determine how they would be affected by various types of space radiation.

Ken Mattingly started his deep space EVA at 20:33:46 GMT on April 25, 1972 just a minute and a half behind schedule. His first task was to set up the television camera which began transmissions of his activities back to Earth shortly thereafter. As with the earlier transearth EVA, Mattingly retrieved the pair of film cassettes from the cameras during two separate trips to the SIM and passed them to Charlie Duke while Young monitored the spacecraft systems from his seat. And like the earlier transearth EVA, Mattingly found that the procedure was easier than it had been during training back on Earth. During his third trip to the SIM to inspect the condition of the instruments, Mattingly noted the presence of bubbles in the thermal coating of the SM exterior. These were especially noticeable near Quad B (one of the set of SM reaction control thrusters near the SIM which had been deactivated for the EVA) although they did not seem to be confined to the areas near the thruster nozzles.

About 50 minutes into the EVA, Mattingly opened the MEED and placed it on the CM hatch while Charlie Duke and ground controllers kept the time for the experiment’s ten-minute exposure to space. While Mattingly had opened the MEED easily enough, he did experience some trouble trying to close it at the end of its exposure time. He eventually got it partially closed and passed it inside to Duke and Young who were able to seal it. Television coverage ended about 69 minutes into the EVA and Mattingly passed the television camera along with the MEED.

Ken Mattingly reentered to the CM cabin upon finishing his activities with the EVA officially ending at 21:57:28 GMT after a duration of one hour, 23 minutes and 42 seconds – just shy of 14 minutes longer than scheduled. With the successful conclusion of the second transearth EVA of the J-series, the crew of Apollo 16 settled into their routine for the last two days of their mission which ended with a splashdown in the Pacific at 19:45:05 GMT on April 27, 1972.

Here is a video of the Apollo 16 transearth EVA television coverage:

Apollo 17

The third and final J-series mission was that of Apollo 17 launched in the early morning hours of December 7, 1972. The CMP for this mission who would perform the transearth EVA was 39 year old US Navy Commander Ronald E. Evans who, like Worden and Mattingly before him, was part of NASA’s fifth group of astronauts and would be making his first spaceflight. Before being selected as an astronaut in April 1966, Ron Evans had been a carrier-based naval aviator and combat flight instructor. Supporting Evans during his transearth EVA as LMP was Dr. Harrison H. (Jack) Schmitt who was a trained geologist making his first spaceflight after being selected as a scientist-astronaut in June 1965 as part of NASA’s fourth group of astronauts. The Apollo 17 mission commander was US Navy Captain Eugene A. Cernan. Cernan was a veteran astronaut who had previously flown as the pilot on the Gemini 9 mission in 1966 (see “The Angry Alligator and the Snake: The Mission of Gemini 9”) and as the LMP of the Apollo 10 lunar mission in 1969 (see “Apollo 10: The Adventure of Charlie Brown & Snoopy“).

While the Panoramic and Mapping Cameras were retained for the Apollo 17 mission, the mix of other instruments in the SIM for this mission was very different. The main impact on the tasks Ron Evans would need to perform during his transearth EVA involved the new S-209 Lunar Sounder experiment which would direct ground penetrating HF and VHF pulses towards the Moon to characterize its subsurface structure to depths of about 1.3 kilometers. The sounding data from this experiment were optically recorded on 70 mm photographic film whose cassette would need to be retrieved along with the film cassettes of the cameras.

The Apollo 17 CSM America and the LM Challenger arrived in lunar orbit 19:53:55 GMT on December 10, 1972. With the SIM bay’s cover being successfully jettisoned 4 hours and 48 minutes earlier (after which it followed a trajectory past the Moon and into solar orbit as had happened during the earlier missions), the new suite of SIM instruments was ready to go to work. Gene Cernan and Jack Schmitt entered Challenger and undocked from America at 17:20:56 GMT on December 11 to land in the Taurus-Littrow Valley for three full days of surface exploration leaving Ron Evans to perform his tasks in lunar orbit.

Challenger lifted off from the lunar surface at 22:54:57 GMT on December 14 carrying Cernan, Schmitt and the almost 111 kilograms of lunar samples they had gathered. The LM ascent module rendezvoused and docked with America 2¼ hours later where Ron Evans had performed his solo mission. After the crew had transferred themselves, the lunar samples and other gear they still required to the CSM, the now empty LM ascent stage was jettisoned at 04:51:31 GMT on December 15 to be intentionally crashed into the lunar surface. The reunited crew spent the next 42 hours in lunar orbit completing their science program. America ignited its main engine for TEI at 23:35:09 GMT on December 16 as the last Apollo mission left the Moon for home.

As with the earlier J-series missions, preparations for the planned 68-minute transearth EVA started not long after the crew woke up from their first post-TEI sleep period. The crew ended up about a half an hour ahead of schedule as they methodically worked their way through their checklist and prepared for the EVA. That half hour was lost, however, due to minor issues with the crew hatch probably due to residual air still in the cabin after depressurization as a result of spacesuit outgassing. Ron Evans officially started his EVA at 20:27:40 GMT on December 17 just 12 minutes behind the prelaunch schedule and about 290,000 kilometers from Earth. Within a couple of minutes, Evans had set up the television camera which allowed his activities to be monitored in real-time back on Earth.

Less than a half an hour into the EVA, Evans had retrieved the film cassette from the Panoramic Camera and passed it along to Jack Schmitt waiting in the crew hatch. This was followed 13 minutes later by the remaining film cassettes. Once again, all the activities went smoothly with no major issues encountered. Just had been observed during the Apollo 16 EVA, Evans noted the thermal control paint flaking off of the SM exterior. Evans reentered the spacecraft at 21:13 GMT after passing the television camera inside and closed the hatch with a little difficulty again because of suit outgassing. The last transearth EVA of the Apollo program officially ended at 21:33:24 GMT with a duration of 65 minutes and 44 seconds – just a few minutes shorter than scheduled.

With the transearth EVA now completed, the Apollo 17 crew stowed their gear and spent the remaining two days of their flight performing their usual mix of tasks as well as preparing for their return to Earth. The Apollo 17 mission ended with the successful splashdown of the CM in the Pacific Ocean at 19:24:59 GMT on December 19, 1972. Not only did this mark the last time that humans would visit the Moon, it was also the last time (so far) that anyone performed a deep space EVA far from the safety of the Earth.

Here is a short video excerpt of the Apollo 17 transearth EVA television coverage:

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Additional Related Videos

Here is a NASA documentary from 1971 about the Apollo 15 mission entitled In the Mountains of the Moon.

Here is another excellent NASA documentary from 1972, Nothing So Hidden, which provides a summary of the Apollo 16 mission.

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Finally, here is a NASA documentary from 1973 covering the achievements of the Apollo 17 mission entitled On The Shoulders of Giants.

Related Reading

“Vintage Micro: The Apollo Particles and Fields Subsatellites”, Drew Ex Machina, November 23, 2014 [Post]

General References

Apollo 15 – Press Kit, NASA Press Release 71-119, July 15, 1971

Mission Director’s Summary Report, Apollo 15, NASA, August 7, 1971

Apollo 15 Technical Crew Debriefing, MSC-04561, NASA, August 14, 1971

Mission Operation Report – Apollo 16 Mission, M-933-72-16, NASA, April 3, 1972

Apollo 16, NASA Press Release 72-64, April 6, 1972

Mission Director’s Summary Report, Apollo 16, NASA, April 27, 1972

Apollo 16 Technical Crew Debriefing, MSC-06805, NASA, May 5, 1972

Apollo 17, NASA Press Release 72-220K, November 26, 1972

Mission Operation Report – Apollo 17 Mission, M-933-72-17, NASA, November 28, 1972

Post Launch Mission Operation Report – Apollo 17 Mission, M-933-72-17, NASA, December 19, 1972

Apollo 17 Technical Crew Debriefing, MSC-07631, NASA, January 4, 1973

Richard W. Orloff and David M. Harland, Apollo: The Definitive Sourcebook, Springer-Praxis, 2006

Robin Wheeler, “The ITEK Panoramic Camera”, NASA History Web Site, last updated February 17, 2017 [Link]

Robin Wheeler, “The Fairchild Lunar Mapping Camera”, NASA History Web Site, last updated February 17, 2017 [Link]

Al Worden and Francis French, Falling to the Earth: An Apollo 15 Astronaut’s Journey to the Moon, Smithsonian Books, 2012