'Exploration at Its Greatest': 45 Years Since the Mission of Apollo 15 (Part 2)

Dave Scott works with the Lunar Roving Vehicle (LRV) on the slopes of Hadley Rille during Apollo 15. Photo Credit: NASA

Dave Scott works with the Lunar Roving Vehicle (LRV) on the slopes of Hadley Rille during Apollo 15. Photo Credit: NASA

Since the evening of 20/21 July 1969, it had become something of a tradition for the commander of each Apollo lunar landing mission to make a comment as he took his first steps on the Moon. Following Neil Armstrong’s historic words to the tongue-in-cheek quip made by Apollo 12’s Pete Conrad to Al Shepard’s remark about the figurative and literal length of his journey to the Moon, it was widely expected that Apollo 15 Commander Dave Scott would continue the tradition. And for an astronaut whose career started as an Air Force fighter pilot, but who was gradually won over by the science of geology, Scott’s words at 9:29 a.m. EDT on 31 July 1971—45 years ago, today—were wholly appropriate. “As I stand out here in the wonders of the unknown at Hadley,” he said as he became the seventh son of Earth to set foot on another celestial body, “I sort of realize there’s a fundamental truth to our nature: Man must explore. And this is exploration at its greatest!”

As outlined in yesterday’s AmericaSpace history article, Scott and Apollo 15 Lunar Module Pilot (LMP) Jim Irwin were tasked with spending almost three days exploring the mountainous region of Hadley, located deep in the Moon’s Apennine Mountains, on the first so-called “J-series” mission. Theirs benefited from a long-duration Lunar Module (LM)—which the all-Air Force crew nicknamed “Falcon”—together with long-duration space suits and the battery-powered Lunar Roving Vehicle (LRV). The latter, known as the “rover,” would allow Scott and Irwin to explore a far broader area of the Moon’s terrain than their predecessors. Meanwhile, in orbit, Apollo 15 Command Module Pilot (CMP) Al Worden operated a complex battery of research instruments aboard the Command and Service Module (CSM) Endeavour.

Apollo 15, originally the last of the H-series lunar landing missions, evolved to become the first member of the J-series, following the tumultuous events of 1970. Photo Credit: NASA

Apollo 15, originally the last of the H-series lunar landing missions, evolved to become the first member of the J-series, following the tumultuous events of 1970. Photo Credit: NASA

With Dave Scott having just become the seventh man on the Moon, the time soon came for Irwin to join him in eighth place. The pair quickly set to work deploying the rover from its berth in Falcon’s descent stage. To do so, they tugged on a series of pulleys and braked reels, and it required both of them, working in tandem. As it flopped into the lunar dust, the rover was secured with pins. Scott clambered aboard to give it a test drive and the front steering seemed to be inoperable, requiring them to rely instead on rear-wheel steering. After installing the color television camera and loading up the geology tools, they buckled themselves aboard and set off. Reaching peak speeds of 5-6 mph (8-9.5 km/h), it was a bouncy ride and if the rover hit a rock, it literally went airborne for a couple of seconds. Irwin later likened it to a bucking bronco or an old rowing boat on a rough lake.

“I’ve never liked safety belts,” he wrote in his memoir, To Rule the Night, “but we couldn’t have done without them on the rover. You could easily get ‘seasick’ if you had any problem with motion.” In fact, Irwin’s seat belt turned out to be too short and before they could set off Scott had to come around to his side of the rover to buckle him in properly. “We didn’t realize,” Irwin explained, “when we made the adjustments on Earth, that at one-sixth-G the suit would balloon more and it would be difficult to compress it enough to fasten the seat belt.”

The rover was also slightly different to drive than the training version they had used on Earth. Scott found that he had to concentrate all of his energies simply driving and keeping track of craters—the harsh glare of sunlight made the terrain appear deceptively smooth, literally “washing-out” surface features, as hummocks and furrows appeared out of nowhere, at a split-second’s notice. Its maneuverability was good (“it could turn on a dime,” Scott recalled in his memoir, Two Sides of the Moon), but its wheels kicked up enormous rooster-tails of dust, which were thankfully deflected by its fenders. As the navigator, Irwin tried to plot their course on the map, but had difficulty identifying their route because they were uncertain of precisely where they had set Falcon down. However, the towering bulk of nearby Mount Hadley Delta was clear to see, with St. George Crater—an enormous gouge the size of two dozen football fields—on the lowermost slopes, and all they had to do was drive with it on their port quarter and they knew that eventually they would come upon Hadley Rille.

Cresting the top of a ridge, they were rewarded with their first unearthly glimpse of Hadley Rille and gained a clear awareness of its enormous size. Half an hour after leaving Falcon, they made their first scheduled halt at a place called “Elbow Crater,” right on the rim of the rille at the base of the mountain. From here, Scott took a series of pictures of the far side of Hadley Rille, whose interior wall showed clear evidence of layering in outcrops not far below its rim, and the two men took a few minutes to gather samples. Next, they set off toward the rim of St. George Crater. It had been expected that the area would be littered with large blocks of rock, but upon finding the flank of the mountain remarkably clean, Scott decided to halt short of the rim and sample an isolated boulder. It was more than 3.3 feet (1 meter) across and its “half-in-half-out” nature, part-buried in the soft soil.

Haunting view of Jim Irwin with the lunar rover, backdropped by the grandeur of Mount Hadley. Photo Credit: NASA

Haunting view of Jim Irwin with the lunar rover, backdropped by the grandeur of Mount Hadley. Photo Credit: NASA

Simply walking was as strange as the world upon which they were now operating. It felt, Irwin explained, very much like walking on the surface of a trampoline, although the bulk of the space suit made it virtually impossible to move in a natural, Earthly gait. “When you don’t have the weight of your legs available to push against the suit,” he wrote, “you are constrained as to how far you can move. Consequently, you just use the ball of your foot to push off. That’s why we looked like kangaroos when we walked. We flexed the boot and that pushed us forward.”

“One of the Moon’s most striking features,” Scott related, “was its stillness. With no atmosphere and no wind, the only movements we could detect on the lunar surface, apart from our own, were the gradually shifting shadows cast to the side of rocks and the rims of craters by the Sun slowly rising higher in the sky.” There was absolutely no trace of anything which exhibited either life or color or movement and the only sound came from the gentle hum of life-sustaining machinery in their backpacks, the hiss of the air flowing through their suits, or the crackle of each other’s voices or the voice of Houston in their earpieces.

The problem of judging distances had been noted by earlier crews. “There’s nothing of scale which is familiar,” Scott told the Apollo Lunar Surface Journal. “There are no trees, there are no cars, there are no houses … and, as an example, we all know what size trees are in general. There are no trees and there’s nothing in the landscape that has any familiarity. There’s no ‘hook.’ So when you look out there, you see boulders, but you can’t really tell whether it’s a large boulder at a great distance or a small boulder nearby. If it’s very nearby, it’s easy because you can run out along the ground and start calibrating your eyes. If you’re looking close to the LM, you know what three or four inches are, but as you start going out, you start losing your perspective, because there’s nothing to measure out there. It’s a very interesting phenomenon that everybody gets fooled on these distances.”

Having said this, Scott added that the tracks of the rover lent some indication of distance. “Once you have some tracks,” he said, “you can start seeing things. As an example, up on the side of Hadley Delta, looking back at the Lunar Module, boy, it was small!” In the absence of an atmosphere or the slightest trace of haze, Falcon appeared far closer and far smaller than it actually was. “But it gives you a scale of how far away it is,” Scott concluded. Even decades later, Scott expressed frustration with his inability to describe how it felt: The ability of his eyes and how well they transmitted images to his brain was good on the Moon. Yet there was nothing on Earth to compare with it.

Heading back toward Falcon after a little more than two hours, the two men could take great pride in their achievements so far. Yet they still had a sizeable portion of work to do before returning inside. Of primary importance was the assembly of their Apollo Lunar Surface Experiments Package (ALSEP). Scott picked a spot a few hundred feet from the lander and Irwin lugged it over, one pallet on each end of a carrying bar, not dissimilar to a giant dumbbell. On his cuff checklist, Irwin checked a small “map” of where each component was supposed to go. Meanwhile, Scott was experiencing his own problems. One of the ALSEP’s experiments was the heat-flow investigation. This had been assigned to the ill-fated Apollo 13 mission, but never made it to the Moon.

The Lunar Roving Vehicle (LRV), pictured here with Apollo 15 Lunar Module Pilot (LMP) Jim Irwin, was of fundamental importance in enabling the crews of the J-series Apollo missions to expand the scope of their scientific exploration. Photo Credit: NASA

The Lunar Roving Vehicle (LRV), pictured here with Apollo 15 Lunar Module Pilot (LMP) Jim Irwin, was of fundamental importance in enabling the crews of the J-series Apollo missions to expand the scope of their scientific exploration. Photo Credit: NASA

It required Scott to use a small, box-like drill to bore a couple of deep holes into the surface and emplace a pair of temperature probes. He would then drill a third hole for a core sample. He made excellent progress on the first hole, reaching a depth of 1.6 feet (0.5 meters), then met a hard subsurface. Despite leaning on the drill to give it extra bite, he fell behind schedule and was advised to insert the first set of probes. The second hole proved even harder, and Mission Control called a halt with the drill only a couple of feet into the ground. Capcom Joe Allen told Scott to take a breather, then help Irwin with deploying the retroreflector and a solar-wind experiment. They would have to complete the drilling later. Their first Moonwalk ended slightly earlier than planned, after 6.5 hours. Back inside Falcon, both men were exhausted. The stress of driving and the toughness of handling the drill for the heat-flow experiment had worn out Scott’s hands and forearms. Irwin described the pain in his fingers as excruciating.

They took each other’s gloves off to inspect the damage: Perspiration poured from them, but there was no evidence of bleeding or bruising. Then they realized that their fingernails, which had grown during the last five days, had been immersed in sweat for the last seven hours. To aid movement, their gloves had been designed to fit tightly against the tips of their fingers; the pressure and the pain was on the ends of the nails. Irwin resolved to cut his nails and advised his commander to do the same, but for some reason—perhaps fearful that it might compromise his own dexterity on the surface—Scott declined.

Irwin was also uncomfortable. A problem with his drinking water bag had left him absolutely parched for more than seven hours. “There was a nozzle that you’d bend down to open a valve so you could suck the water out and drink it within the protection of the space suit,” he explained, “but I could never get my drink bag to work and I never got a single drink of water during the whole time I was out on the surface of the Moon.” He did, however, manage to gobble down a fruit stick inside his helmet and that helped him to keep going when the time came to assemble the ALSEP. Now, having doffed his suit, Irwin guzzled water like a jogger, then settled down with Scott for their second night on the Moon.

“Settled” probably was not an appropriate word, for conditions inside Falcon cannot have been pleasant: With the presence of all the rocks and soil specimens, the smell of the Moon—a strong, gunpowder-like aroma—pervaded the air and dust covered everything. They stashed their filthy suits at the back of the cabin, making sure that the gloves were fitted, so as not to impair their seals, then debriefed to Houston and bedded down for their second night’s sleep on the Moon. The next two EVAs would bring tremendous scientific discoveries, which continue to resonate to this day.

 

 

The concluding parts of this series will appear next weekend.

 

 

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6 comments to ‘Exploration at Its Greatest’: 45 Years Since the Mission of Apollo 15 (Part 2)

  • James

    “He would then drill a third hole for a core sample. He made excellent progress on the first hole, reaching a depth of 1.6 feet (0.5 meters), then met a hard subsurface. Despite leaning on the drill to give it extra bite, he fell behind schedule and was advised to insert the first set of probes.”

    In the future being able to ‘drill and dig deep into’ the Lunar regolith will be a crucial ‘must be able to do’ survival skill using some type of drill and backhoe on a heavy equipment machine.

    Why?

    Astronauts on long Lunar surface missions will need to use five or more meters of regolith as ISRU radiation shielding.

    “Five meters of soil will provide the same protection as the Earth’s atmosphere– equivalent to 1,000 g/cm2 of shielding.”

    From: ‘How much radiation will the settlers be exposed to?’
    At: http://www.mars-one.com/faq/health-and-ethics/how-much-radiation-will-the-settlers-be-exposed-to

    Note:

    “Zeitlin and his colleagues estimate that astronauts would be exposed to about 0.66 Sievert (Sv) — the unit scientists use for measuring radiation — of galactic cosmic ray radiation during the round-trip to Mars, not including their time spent on the surface of the Red Planet. About 1 Sv of radiation exposure is usually associated with about a 5 percent bump in fatal-cancer risk later in life.”

    From: ‘Mars-Bound Astronauts Could Face Higher Risk of Cancer’ By Miriam Kramer, Space.com Staff Writer May 30, 2013 At: http://www.space.com/21359-mars-radiation-manned-mission.html

    Currently, “the annual exposure caused by GCR on the lunar surface is roughly 380 mSv (solar minimum) and 110 mSv (solar maximum). The analysis of worst case scenarios has indicated that SPE may lead to an exposure of about 1 Sv.”

    From: ‘Radiation exposure in the moon environment’ By Guenther Reitz, Thomas Berger, and Daniel Matthiae in “Planetary and Space Science” Volume 74, Issue 1, December 2012, Pages 78–83.
    At: http://www.sciencedirect.com/science/article/pii/

    Of course, sometimes things may change significantly on the surface of the Moon and Mars and in the Deep Space environment.

    “If the sun is entering another grand minimum period, the assumption we may be able to fly Mars missions during solar maximum will not hold, at least not for the next twenty years. Furthermore, slowly declining solar activity beyond what we’ve experienced in the past fifty years infers that GCR activity will increase to levels we have not seen in the time of human space travel. An analysis of the historical GCR spectra is given by Bonino, et al. and shows that during the Maunder minimum the GCR flux more than doubled compared to the GCR flux of the past fifty years, and during the Dalton minimum, the GCR flux during the solar minimum was anywhere from 1.5 to 2 times larger than the current solar minimum GCR levels23.” Page 7

    And, “Thus, if the predictions of the solar cycle are correct, then over the next thirty to fifty years, we will see an increase in the overall GCR flux. The flux during solar maximum will be similar to the flux we are currently experiencing at solar minimum and the flux at solar minimum will be 1.5 to 2 times higher than we’ve ever experienced. Consequently, we will not be able to complete a three-year Mars mission without heavily shielded spacecraft
    and faster traverse times (via new propulsion methods).” Page 8

    From: ‘Estimating the Effects of Astronaut Career Ionizing Radiation Dose Limits on Manned Interplanetary Flight Program’ By Steven L. Koontz, Kristina Rojdev, Gerard D. Valle, John J. Zipay, and William S. Atwell 2013
    At: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130013437.pdf

    Astronauts and their helpful robots on the Moon, Phobos, Mars, and Ceres will need to dig deep and bury their habitats, workshops, garages, and spaceship hangars.

    Thank you Ben Evans! I’m looking forward to reading the “concluding parts of this series” of interesting articles.

  • James

    “He would then drill a third hole for a core sample. He made excellent progress on the first hole, reaching a depth of 1.6 feet (0.5 meters), then met a hard subsurface. Despite leaning on the drill to give it extra bite, he fell behind schedule and was advised to insert the first set of probes.”

    In the future being able to ‘drill and dig deep into’ the Lunar regolith will be a crucial ‘must be able to do’ survival skill using some type of drill and backhoe on a heavy equipment machine.

    Why?

    Astronauts on long Lunar surface missions will need to use five or more meters of regolith as ISRU radiation shielding.

    “Five meters of soil will provide the same protection as the Earth’s atmosphere– equivalent to 1,000 g/cm2 of shielding.”

    From: ‘How much radiation will the settlers be exposed to?’
    At: http://www.mars-one.com/faq/health-and-ethics/how-much-radiation-will-the-settlers-be-exposed-to

    Note:

    “Zeitlin and his colleagues estimate that astronauts would be exposed to about 0.66 Sievert (Sv) — the unit scientists use for measuring radiation — of galactic cosmic ray radiation during the round-trip to Mars, not including their time spent on the surface of the Red Planet. About 1 Sv of radiation exposure is usually associated with about a 5 percent bump in fatal-cancer risk later in life.”

    From: ‘Mars-Bound Astronauts Could Face Higher Risk of Cancer’ By Miriam Kramer, Space.com Staff Writer May 30, 2013 At: http://www.space.com/21359-mars-radiation-manned-mission.html

  • James

    Currently, “the annual exposure caused by GCR on the lunar surface is roughly 380 mSv (solar minimum) and 110 mSv (solar maximum). The analysis of worst case scenarios has indicated that SPE may lead to an exposure of about 1 Sv.”

    From: ‘Radiation exposure in the moon environment’ By Guenther Reitz, Thomas Berger, and Daniel Matthiae in “Planetary and Space Science” Volume 74, Issue 1, December 2012, Pages 78–83.
    At: http://www.sciencedirect.com/science/article/pii/…

    Of course, sometimes things may change significantly on the surface of the Moon and Mars and in the Deep Space environment.

    “If the sun is entering another grand minimum period, the assumption we may be able to fly Mars missions during solar maximum will not hold, at least not for the next twenty years. Furthermore, slowly declining solar activity beyond what we’ve experienced in the past fifty years infers that GCR activity will increase to levels we have not seen in the time of human space travel. An analysis of the historical GCR spectra is given by Bonino, et al. and shows that during the Maunder minimum the GCR flux more than doubled compared to the GCR flux of the past fifty years, and during the Dalton minimum, the GCR flux during the solar minimum was anywhere from 1.5 to 2 times larger than the current solar minimum GCR levels23.” Page 7

    And, “Thus, if the predictions of the solar cycle are correct, then over the next thirty to fifty years, we will see an increase in the overall GCR flux. The flux during solar maximum will be similar to the flux we are currently experiencing at solar minimum and the flux at solar minimum will be 1.5 to 2 times higher than we’ve ever experienced. Consequently, we will not be able to complete a three-year Mars mission without heavily shielded spacecraft
    and faster traverse times (via new propulsion methods).” Page 8

    From: ‘Estimating the Effects of Astronaut Career Ionizing Radiation Dose Limits on Manned Interplanetary Flight Program’ By Steven L. Koontz, Kristina Rojdev, Gerard D. Valle, John J. Zipay, and William S. Atwell 2013
    At: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130013437.pdf

    Astronauts and their helpful robots on the Moon, Phobos, Mars, and Ceres will need to dig deep and bury their habitats, workshops, garages, and spaceship hangars.

    Thank you Ben Evans! I’m looking forward to reading the “concluding parts of this series” of interesting articles.

    • James

      “We observed that the variations from maxima to minima during the past two centuries are 3-4 times larger than those calculated on the basis of the GCR fluxes observed during the past four decades, extrapolated back in time on the basis of their dependence on the sunspot numbers. The results indicated that during prolonged solar quiet periods the GCR flux was much higher (weaker interplanetary magnetic field) than during the recent individual solar
      cycle minima.”

      From: COSMOGENIC 44Ti IN CHONDRITES AND GALACTIC COSMIC RAY VARIATIONS SINCE THE MAUNDER MINIMUM. By G. Bonino, G. Cini Castagnoli, D. Cane, C. Taricco, and N. Bhandari
      64th Annual Meteoritical Society Meeting (2001) At: file:///C:/DOCUME~1/think/LOCALS~1/Temp/Cosmogenic_Ti44_in_Chondrites_and_Galactic_Cosmic_.pdf

      Yep, burying habitats deeply on the Moon, Phobos, Mars, and Ceres seems like a good idea.

  • […] peaks, football-field-sized craters, and a 25-mile-long (40-km) gorge, known as Hadley Rille. As outlined in last week’s AmericaSpace history articles, the discoveries made by Apollo 15 revealed more about the history and evolution of the lunar […]

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