Apollo 15, Lunar Surface - EVA-1

EVA-1

Throughout the astronauts' sleep period, Mission Control had watched with some concern as the pressure inside descent stage oxygen tanks of the LM slowly dropped. To conserve power during the night, the LM was run on a low data rate telemetry stream, so Mission Control could not tell the exact cause. Unwilling to wake the crew they decided to wait until they had woken up.

In the end, Flight Director Peter Frank chose to wake the crewmen an hour early and got them to turn back on the high data rate telemetry. With this they saw that the valve of the Urine Transfer Device was open even though the receptacle was capped. A total of about 8 out of 95 pounds (3.6 out of 43 kg) of oxygen had been lost. About half of the total amount was reserve. Scott and Irwin would state in the post-flight Technical Debrief that Mission Control should have awakened them as soon as the leak was detected.

Once they were awake, it was decided to start their preparations for the first lunar EVA of their mission. As with everything in Apollo, it was an involved procedure. Not only did they have to prepare Falcon, but had to don their space suits. Apollo 15 was the first crew that got to sleep in long johns rather than having to stay in their space suits. It would not be until four hours after waking up that Mission Control gave the Go to depressurize the LM.

As Scott became the seventh man to step onto the lunar surface, he said:

"As I stand out here in the wonders of the unknown at Hadley, I sort of realize there's a fundamental truth to our nature. Man must explore. And this is exploration at its greatest."

After inspecting the LM, Scott began to unpack the Modularised Equipment Stowage Assembly (MESA), which was attached to the side of the LM and carried the Apollo TV camera, sample bags, batteries, CO₂ scrubbers for the space suits, and other equipment needed while the astronauts were outside the spacecraft. About seven minutes after Scott stepped outside Irwin is on the surface.

Irwin's first task was to collect a contingency sample of lunar rock. This was collected in case of an emergency, i.e., suddenly having to leave the lunar surface within the first few minutes. In such an event having a contingency sample meant that the crew would not return to earth empty-handed. However, the contingency sample was not of much value because the ground surrounding the landing site had been disturbed by the LM descent engine.

After Scott positioned the TV camera on a tripod so Mission Control could see the deployment of the Lunar Rover, he and Irwin began the process by pulling on two lanyards. These released the Rover and let it swing down on hinges. As it did, it began to unfold. They experienced some problems at first due to the angle the LM was sitting on, but within minutes it was on the ground almost ready to go.

Scott had the honor of the first test drive, taking it around the LM. The Rover had both front and back steering, but Scott found that only the rear-wheel steering was working (mysteriously the front steering would be working at the start of the second EVA). Other difficulties came from how their space suits did not bend very much when they sat down. When training on Earth, their body weight had forced the suits down, but on the Moon, they ended up reclining in the seats. Apart from the steering there were no other problems and the crew set about loading up the Rover for their first geological traverse.

The astronauts could not travel any farther than the distance they could walk with the remaining oxygen in their Portable Life Support Systems (PLSS). So the earlier they set out, the farther they could travel. They would travel to the farthest point of the traverse and then work their way back. On EVA-1 they would travel to the base of Hadley Delta via the Rille. Their first target was the crater dubbed Elbow crater, so-called as it sat at a bend in the Rille. The first EVA also served an important task of working out exactly where they had landed. The Rover carried a navigation system that could calculate the distance and direction of a known starting point. By travelling to a known point this could be calibrated.

Scott set off at 9 km/h (6 mph), slow by terrestrial standards, but due to the lowness of the chassis of the Rover and the roughness of the surface, the astronauts would say it seemed quite quick. Throughout the journey, the astronauts had trouble identifying where they were. Due to not knowing exactly where the landing site was and over-enhanced maps, little was familiar. But the route chosen for this first drive had been picked with this in mind. By driving along the side of the rille it would be hard to miss their target.

After arriving at Elbow, Irwin's first task is to take a panorama of the site. At the same time Scott aligned the S-band antenna of the Rover with the Earth. This allowed Mission Control to operate the TV camera. Ed Fendell was in charge of controlling the camera and took his own pan so geologists in the backroom could see the site. The backroom kept track of everything that astronauts did on geology. As a sample was collected they would note its number, location and description on a card.

Scott and Irwin took a radial sample of the crater, taking samples at increasing distances in a straight line from the rim of the crater. After placing the photocalibration gnomon to the west of each sample, it was photographed, before being collected and placed into a numbered bag. Within ten minutes they had gathered four rock samples and it was time to move onto Station 2 — St George.

Five hundred meters south of Elbow was the 2 km wide St George crater. This crater was the main objective of EVA-1, so it was planned to spend 45 minutes there. The flight plan had called for them to use the crater as a way of investigating the interior of Hadley Delta by collecting its ejecta. But as they approached they found there was no ejecta so it was decided not to bothering visiting the rim of St George. Instead they travelled to a boulder sitting in the open by a 6 meter crater.

The rock they stopped at was about 5 feet (1.5 m) across. The larger a rock is, the more likely it was formed in the area, instead of being thrown there by an impact. Firstly they took a soil sample at the base of the rock, then another from a small depression down the hill a bit. Scott announced that after this they would roll the rock over and sample the soil from underneath it. After a couple of futile attempts they managed to chip some pieces off it. In A Man on the Moon Andrew Chaikin writes that Dale Jackson of USGS was having dinner with some astronauts that night in Houston and happily proclaimed that "they did everything but fuck that rock." Other samples in the area were made using a specially designed rake with tines spaced 1 cm apart to collect small pebbles from the regolith. The last task at Station 2 was to take a core sample. This was done using a tube driven into the ground by a hammer.

Mission Control announced that it had decided to cancel a planned stop at a crater named Flow due to time constraints. Thus the astronauts boarded the Rover and drove back past Elbow and on their way to the LM. About 125 meters before a crater named Rhysling, Scott spied a large piece of vesicular basalt sitting by itself. Not wanting to just leave it there, he stopped the Rover. The stop was unplanned so he just told Mission Control his seatbelt had come loose, but quickly got off the Rover, ran over to the rock, using his collection tongs for a calibration in the photos, took a sample and got back to the Rover. During this time, Irwin distracted Mission Control by describing the surrounding craters. It was not until the sample boxes returned to Earth that the stop was discovered.

Back at Falcon, Scott and Irwin set about deploying the Apollo Lunar Surface Experiment Package (ALSEP). Scott would drill the holes for the heat-flow experiment and put in the probes, while Irwin would set up the rest of the equipment. The ALSEP consisted of the passive seismic experiment, lunar surface magnetometer, solar wind spectrometer, suprathermal ion detector, cold cathode gauge experiment, lunar dust detector and the heat-flow experiment. Not included in the ALSEP but deployed by Irwin as well were the Lunar Laser Ranging Experiment (LRRR) and the solar wind composition experiment. The ALSEP equipment was attached via cables to the Central Station powered by an radioisotope thermoelectric generator.

Scott had major trouble with the drilling. The first 40 cm were easy, but from then on it became more and more difficult. After 1.6 m, half of what was planned, he could get no further and Mission Control told him to just emplace the probes and start on the next hole. The extreme torque had locked the chuck meaning it had to be freed with a wrench, further delaying him. He could only get 1 meter into the ground on the second hole before Mission Control called it a day and told them to return to the LM.

They had been outside for 6½ hours. Returning to the LM gave the crew a much needed rest. Irwin was dehydrated as his water bag hadn't worked, and he had gone over seven hours without liquids.