6.08.2018

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On this day in 1971, a fully-suited astronaut poked his helmeted head out of the side hatch of the Command and Service Module (CSM), named “Endeavour”, and into an environment unlike any other. Al Worden—one of three astronauts aboard Apollo 15, our fourth successful manned lunar landing mission—was tasked with retrieving film from cameras in the Scientific Instrument Bay (SIMBay) in the service module. To do that, the 39-year-old Worden had to clamber, hand-over-hand, across a distance of 30 feet (9 meters), and back again. And although the intricate feat of “spacewalking” had been performed several times by Worden’s day, up until 5 August 1971 all had been performed in low-Earth orbit or on the surface of the Moon. Worden remains one of only three humans to have made a “deep space walk” in the cislunar void between Earth and our nearest celestial neighbor.

Artist’s concept of Al Worden’s cislunar EVA to recover film cassettes from the SIMbay. Crewmate Jim Irwin monitors the proceedings from the command module’s open hatch. Image Credit: NASA

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The final three manned missions to lunar distance—Apollo 15 in the summer of 1971, Apollo 16 late the following spring and Apollo 17 in December 1972—were also the most complex. Known as the “J-series”, they were characterized by an upgraded Lunar Module (LM), capable of three-day stays on the lunar surface, and a CSM brimming with SIMBay instrumentation to closely survey the Moon. Whilst the Commanders and Lunar Module Pilots (LMP) for each flight descended to the rugged terrain of Hadley-Apennine, Descartes and Taurus-Littrow, the Command Module Pilots (CMPs) remained in orbit, overseeing an intensive program of observations and measurements.

Since the cylindrical service module could not survive re-entry into Earth’s atmosphere, it was imperative that the CMPs ventured outside to retrieve their camera film during the return journey. On Apollo 15, Al Worden performed the feat, followed by Ken Mattingly on Apollo 16 and, lastly, by Ron Evans on Apollo 17. The deep-spacewalks, or “Trans-Earth” Extravehicular Activities (EVAs), would occur further from Earth than ever before. In fact, the Moon—just 60,000 miles (100,000 km) distant—loomed large in the astronauts’ view, whilst the Home Planet resembled a blue-and-white football, 180,000 miles (300,000 km) in the opposite direction.

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Spacewalks were not originally the intended means of getting SIMbay film back aboard the command module. In a May 2000 oral history for NASA, Worden noted that other methods were discussed, including a clothesline-like reel, but a spacewalk proved the most practical option. “There had already been some preliminary work on how to get this film out of the SIMbay,” Worden told the NASA oral historian. “Of course, it had been in the pipeline for several years and there were a lot of schemes to get the film from…the back of the Scientific Instrument Module all the way up into the command module, a distance of about 30 feet. How do you get out there safely so that you don’t lose it, so that you don’t hurt something? One of the schemes was…an “arm” on a hinge that would go out and pick up the film and…bring it back by the hatch, where you could pick it up.”

When Worden performed the first trans-Earth EVA on 5 August 1971, he had rehearsed every step over 300 times. “The EVA itself was kind of unique,” Worden said of the relatively brief, 39-minute excursion, “sort of a unique perspective. I did have a chance to stand up on the outside [of the service module] and look. I could see the Moon and the Earth at the same time; and if you’re on Earth, you can’t do that, and if you’re on the Moon, you can’t do that! It’s a very unique place to be. I guess our biggest concern was that we had everything tied down so that when we opened the hatch, we didn’t have something go wandering off into space! But outside of that, it was pretty easy.”

Apollo 17 astronaut Ron Evans hauls the cylindrical film canister from the SIMbay mapping camera back to the safety of the command module, during humanity’s most recent deep-space EVA, 45 years ago, today. Photo Credit: NASA

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Since the spacecraft’s cabin was reduced to vacuum for the trans-Earth EVAs, it was necessary for Commander Dave Scott and LMP Jim Irwin to also be fully suited. Irwin recalled that opening the hatch created an effect not dissimilar to a vacuum cleaner, as all unsecured objects began drifting around, including toothbrushes and cameras. Unlike terrestrial spacewalks, the astronauts were surrounded by the pitchest blackness and one of the few sources of illumination was sunlight, reflecting and glinting off the shiny surface of the service module.

After Worden’s experience, the next astronaut to perform a deep-space EVA was Apollo 16 CMP Ken Mattingly, during his own crew’s return from the Moon on 25 April 1972. Wearing Commander John Young’s helmet, equipped with gold-tinted Lunar Extravehicular Visor Assembly (LEVA), Mattingly an hour outside, collecting not only SIMBay film, but also setting up and later retrieving microbial samples in the command module’s hatch. He also lost—then found—his wedding ring, which had somehow gotten lost in the recesses of the spacecraft, before floating outside. It was LMP Charlie Duke who spotted the ring and Mattingly grabbed it and quickly put it into his pocket. “We had the chances of a gazillion-to-one,” Mattingly later recalled. It must have been a relief for his wife, Elizabeth.

Wearing Commander John Young’s red-striped helmet, Apollo 16 astronaut Ken Mattingly works outside the service module during his deep-space EVA in April 1972. Nearby, Charlie Duke assists from the command module’s hatch. Photo Credit: NASA

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With Worden’s 39-minute excursion and Mattingly’s 84 minutes spent outside, it would be Ron Evans on Apollo 17 on 17 December 1972 who would complete the most recent deep-space EVA. Early that morning, the crew removed the center couch in the command module, to give Evans the room he needed to get outside. LMP Jack Schmitt was positioned in the hatch to assist him, whilst Commander Gene Cernan handled the spacecraft systems.

For 2.5 hours, the three men labored in the limited elbow-room reserves of the command module to get themselves ready for the spacewalk. Cernan, whose own EVA on Gemini IX-A in June 1966 had encountered severe difficulties—partly due to the lack of hand-holds—advised Evans to take his time. “When you get out there, just take it nice and slow and easy,” he said. “You got all day long.” Cernan cautioned not to move too quickly and to feel his way along the exterior of the spacecraft. As the side hatch opened, Schmitt offered his own words of encouragement. “Nice day for an EVA, Ron. Go out and have a good time!”

Like Mattingly on Apollo 16, Evans was also wearing his commander’s helmet, equipped with red stripe and gold-tinted LEVA. Although he had griped that the gold visor made it hard for him to see anything inside the cabin, Cernan and Schmitt assured him that he would need its protection during the spacewalk.

Video Credit: NASA

As the hatch opened, a felt-tipped pen drifted outside. Next came Evans himself. Emerging into the void, he was presented with the electrifying view of a crescent Earth, straight ahead, before being arrested by the blinding glare of the Sun to his right. Cernan advised him to pull down his gold-tinted visor, which Evans promptly did. Having identified himself to Mission Control as “the CMP” for most of the mission, he seemed a little unsure of how to identify himself. “Houston, this is…let’s see…when you’re EVA, they use your name, don’t they?”

“Yessir, we’ll use it, Ron,” replied Capcom Bob Overmyer.

Evans’ first act was to install a pole for the television camera, after which he conducted a visual survey of the service module’s external skin. Some of the paint was blistered, he noted, which readily peeled off with the fingers. Humming to himself, Evans moved to the SIMbay and set himself up in the foot restraints. “Talk about being a spaceman,” he breathed. “This is it!” It was also surprising to witness Earth as a crescent, having seen the Moon in such a phase so many times during his life. “The crescent Earth is not like the crescent Moon,” Evans reflected. “It’s got kind of like…horns…and the horns go all the way around, and it makes almost three-quarters of a circle.”

In spite of the lightheardtedness, there was much work to do. He hooked a tether onto the SIMbay’s lunar sounder data-cassette, thereby ensuring that it would not float away. After returning the cassette to a waiting Schmitt in the command module’s hatchway, Evans returned to the rear of the service module to pick up the pan camera’s data-cassette. At one stage, he paused for a breather and offered a brief “Hi” greeting to his mother, wife and children.

All told, the three CMPs of Apollos 15, 16 and 17 were outside for a combined three hours and 11 minutes—41 minutes for Worden, 83 minutes for Mattingly and 67 minutes for Evans—and to this day they remain the only humans to have spacewalked in the vast cislunar gulf between Earth and the Moon. Perhaps in the near future, with America’s plans to return again to lunar distance, others will join them. But for now, these three intrepid astronauts remain the only members of an exclusive and unique club.

Quelle: AS