Apollo 15: Into the Mountains of the Moon

Apollo 15 was sent to the Moon in July 1971, its primary mission goals to explore the spectacular Hadley-Appenine region, carry out scientific experiments from orbit and evaluation of new and improved Apollo equipment,including the Lunar Rover. Here is the story ofˆà possibly the most ambitious Apollo moon landing.

Scott, Worden and Irwin (Image credit: NASA)

The next time you see the full Moon high in the south, look carefully at the centre of the northern part of the Moon’s near side. About a quarter of the way down the disc are the two blotches of the Mare Imbrium and Mare Serinitatis. Between them is a mountain range, Montes Apenninus, named after the Apennine Mountains in Italy. In this lunar mountain range lies the 4.6 km peak of Mt Hadley. It was at the plain below Hadley that three men from the planet Earth landed in July 1971, their mission to make one of the greatest scientific explorations ever. This was Apollo 15.

Apollo 15’s landing site, note Hadley Rille in the photograph and craters named for a couple of classic SF novels. (Image credit; NASA)

Apollo 15 was launched moonward from Kennedy Space Center on 26 July 1971 (the day my brother was born!) on a Saturn V rocket. Compared to the Saturn used by the previous Apollo missions, this one was upgraded to send a heavier payload to lunar orbit. ˆàSqueezed into the Command Module Endeavour was Commander David R. Scott (1932- ), Lunar Module pilot James B. Irwin (1930-91) and ˆàCommand Module Pilot Alfred M. Worden(1932- ). Scott was a veteran of Gemini 8 and Apollo 9, but his crewmates were both entering space for the first time.

Apollo 15 deploying its subsat in a pre-flight artist’s impression. (Image credit: NASA)

This was the first of the òÀÜJ-seriesòÀÝ Apollo landings (and thanks to cuts to NASAòÀÙs budget there would be only three of these), designed for a longer stay and to enable a rigorous scientific investigation of the landing site. It was just two years since Apollo 11, but the technology was enormously improved. Apollo 15òÀÙs Lunar Module Falcon carried an improved engine and larger fuel load, enabling more equipment and supplies to be carried plus a longer hovering time to allow its crew to make a pinpoint landing. Among its cargo was a Lunar Roving Vehicle (LRV), a 4-wheel drive electric car created by Boeing to widen the terrain visited by the astronauts. The astronauts themselves wore A7L spacesuits, enhanced and made more comfortable (essential for longer EVAs) on the basis of experience from previous missions. Importantly, they were easier to take off and put on. J Series crews could strip down to their longjohns to sleep in hammocks stretched across the LM’s cabin.The Command Service Module, home to Worden while his colleagues explored the surface, was a newer and better model too. A panel could be jettisoned from the drum-shaped Service Module to reveal the SIMBAY, a battery of instruments including a deployable subsatellite to map the Moon’s gravitational field and a powerful survey camera to make detailed images of the MoonòÀÙs battered peaks and plains.

A panorama assembled from images taken by David Scott during his “stand up EVA”. The view is to Falcon’s rear, note the VHF antenna and the subtleties to the tones of the lunar surface. (Image credit NASA)

NASAòÀÙs army of technicians was by now making it look very easy send people across deep space to land on another world. Everything went smoothly, too smoothly perhaps as the mission provoked very little interest from the general public; ˆàperhaps NASA should have played up the drama.ˆà Laden with tools and scientific gear, the Lunar Module Falcon swooped low over the Apennines before descending vertically to touch down near Hadley Rille on 30 July 1971. To be exact, the craft sat at a pronounced tilt 600 m from the planned landing site in a region of the Mare Imbrium called Palus Putredinus, the unattractively named Marsh of Decay. Scott and Irwin found the terrain in the area to be cratered and rolling with a towering backdrop of nearby mountains (Scott took several unique panoramic images by standing on the LMòÀÙs Ascent Engine housing and poking his head and shoulders through the docking hatch on FalconòÀÙs roof). The Apennine Mountains, envisioned as steep and jagged, turned out to be gently rounded by nearly four billion years of micrometeoroid impacts. These mountains were why this place had been selected as a landing site. They were suspected to be composed of ancient primordial rock unchanged from the Moon’s then mysterious birth, samples of their material ought to litter the lava plain to provide clues to the Moon’s origin. Another attraction was Hadley Rille, a deep and sinuous channel 450 m deep which wriggled for hundreds of kilometres across the plain.

Falcon listing to the side and James Irwin tending to the LRV with Mt. Hadley in the background. The pile of foil marks where the LRV was unpacked. (Image credit: NASA)

Shortly after setting foot on the parched grey dust, Scott and Irwin unpacked the folded LRV from its nook in Falcon‘s descent stage. They pulled on two lanyards which released the Rover and let it swing down on its hinges. As it did, it began to unfold.ˆà Minutes later it was resting on its wire mesh tyresˆà and ready to go. Scott had the honour of the first test drive, soon he and Irwin were bouncing along towards Hadley Rille at 7mph. (The LRV was not the first wheeled vehicle to roll across the regolith, Lunokhod 1,ˆà a Soviet robot was wandering over the Mare Imbrium at that very minute and had been there since the previous December).ˆà In the next three days Scott and Irwin made three moonwalks accumulating 18 hours, 35 minutes outside the LM and drove 28 km. After the final EVA Scott performed a famous demonstration of a hammer and feather falling at the same rate in the lunar vacuum. The CSM remained in orbit overhead while Worden performed scientific experiments.

The LRV allowed the astronauts to leave the LM far behind. (Image credit: NASA)

Apollo 15òÀÙs crew, all former military airmen, took their role as scientists very seriously to the delight of geologists (a previous Apollo crew had disgruntled the scientists on the ground by taking a flippant attitude to collecting samples, but in contrast Scott and his crew had become genuine rockhounds). Thanks to the astronauts’ skills and enthusiasm, their new gear and the location, this was a hugely productive mission. Perhaps the most important sample found was the òÀÜGenesis RockòÀÝ, a lump of white crystalline anorthosite, possibly a piece of the MoonòÀÙs primordial crust. Apart from meteorites, this is the oldest object in human hands, dated at 4.5 billion years old, only 100 million years younger than the Solar System.

David Scott with the Appenines in the distance (Image credit: NASA)

The LM lifted off from the Moon on 2 August after nearly 67 hours on the lunar surface, during this time the astronauts had covered 27.9 km in the LRV, driving right the edge of Hadley Rille. They collected 77 kg of rock and soil samples, treasures more valuable than gold. After rejoining Worden, Endeavour set off towards its homeworld. On 5 August, between the Moon and Earth, Worden carried out the first deep space EVA when he exited the CM and made three trips to the instrument bay at the rear of the SM to retrieve film canisters.

All alone in the night: Al Worden at work between worlds. (Image credit: NASA)

There was a scary moment during the final minutes of the voyage. During descent, one of the three main parachutes failed to open fully, and the CM splashed heavily in the rolling waves of the Pacific Ocean 330 miles north of Honolulu, Hawaii, alarming but not injuring the crew. It was 7 August 1971. After this heroic homecoming, the three astronauts suffered a sudden fall from grace when their management discovered that Apollo 15’s crew had carried postal stamps to the Moon for resale at high prices to collectors. All three were disciplined and never flew in space again. Worden and Scott took desk jobs with NASA for a few years, while Irwin left the agency to become a preacher, involving himself in several quixotic quests to locate Noah’s Ark. Worden and Irwin both visited Armagh Planetarium in the 1970s.

Apollo 15 was in many ways the perfect Apollo mission, the men and their machines did everything that was expected of them. Those were great days!

(Article by Colin Johnston, Science Education Director)