Apollo 15

Firsts

First automotive vehicle on the Moon.
First of the Apollo “J” missions, which doubled the time spent on the lunar surface and conducting “moonwalks,” compared to the previous record-holder, Apollo 14.

Key Dates

Launch: July 26, 1971

Lunar Orbit Insertion: July 29, 1971

Lunar Landing: July 30, 1971

Lunar Surface Departure: Aug. 2, 1971

Recovery on Earth: Aug. 7, 1971

Results

Apollo 15 was the fourth mission in which humans walked on the Moon and the first in which they drove. It kicked off a series of missions in which astronauts spent twice as much time on the lunar surface in general -- and outside the lunar module in particular -- than the previous record holder, Apollo 14. And with the help of the first automotive vehicle designed not only for off-road but for off-planet use, the astronauts of Apollo 15 explored a more diverse region of the Moon than ever before and brought nearly as much lunar rock and soil back to Earth as the previous two Moon-landing missions combined.

On July 30, 1971, as Alfred M. Worden piloted the command module “Endeavor” in lunar orbit, Apollo 15 Commander David R. Scott and James B. Irwin, pilot of the lunar module “Falcon,” descended to the Mare Imbrium (Sea of Rains) region at the foot of the Apennine mountain range. They touched down with two of Falcon’s landing pads just over the edge of a small crater that the astronauts had not been able to see through the dust raised by their rocket engine, causing the lunar module to tilt. But they were stable enough to continue their mission.

Scott removed Falcon’s upper hatch, stood on the engine cover and spent 33 minutes photographing the surroundings and describing what he saw to scientists in Houston.

Motoring on the Moon

They unfolded and deployed their lunar rover the following day. Specially designed for operation at 1/6 Earth’s gravity, it could carry 180 pounds (82 kilograms) of astronauts, gear and samples on the Moon (which would weigh 1,080 pounds or 490 kilograms on Earth), more than twice the rover’s weight, but risked collapse if accidentally sat upon while still on Earth. Though its range was 40 miles (65 kilometers) at speeds up to 11 mph (17 kilometers per hour), the astronauts were restricted to an area 3 miles (5 kilometers) from the lunar module so they could walk back if the rover broke down.

Over the course of nearly 67 hours on the lunar surface, Scott and Irwin conducted three EVAs (extravehicular activities), during which they sampled three distinct types of structures: the Apennine Front, which had been produced by the collision of a large asteroid or comet with the Moon; a series of horizontal lava flows that filled part of the impact basin; and a ray of ejecta from a large, geologically young crater that formed after the basin was filled.

Among the rocks they collected was one that was later dubbed the “Genesis Rock.” It was a very pure specimen of anorthosite, a type of rock believed to have floated like icebergs in the magma oceans that constituted the Moon’s outer layers early in its history. It was found to be more than 4 billion years old and was the most ancient whole rock recovered from the lunar surface to that point. The prospect of finding such rocks was one reason the landing site had been selected.

They also photographed a section of Hadley Rille, a steep-walled fissure about 0.9 mile (1.5 kilometers) wide and 1,300 feet (400 meters) deep, which winds for more than 60 miles (100 kilometers) along the foot of the Apennine mountain range; drilled core samples to a depth of 8 feet (2.5 meters); and set up the Apollo Lunar Surface Experiments Package (ALSEP).

Thanks to the television camera mounted on the rover, scientists back on Earth could for the first time see live coverage everywhere the astronauts went, not just at the landing site. The camera could be controlled from Earth, enabling scientists to look around for interesting features while the astronauts conducted their tasks.

Salute to Galileo and Fallen Astronauts

At the end of the final EVA, Scott performed a televised sequel to the experiment Galileo is purported to have conducted at the Tower of Pisa. He dropped a hammer and a feather together in the lunar vacuum and observed that they struck the ground at the same time.

The astronauts left behind a memorial to the 14 astronauts and cosmonauts known to have died during the U.S. and Soviet space programs (two Soviet cosmonaut deaths were unknown to the U.S. at the time). It consisted of a small figurine called the “fallen astronaut” and a plaque on which the 14 names were inscribed.

While Scott and Irwin explored the lunar surface, Worden conducted experiments from lunar orbit which provided information about the chemical composition of large areas of both the far and near sides of the Moon. Endeavor’s highly inclined orbit enabled Worden to see features that no previous observers had seen, and he transmitted descriptions to Earth each time he crossed the near side of the Moon. On his 15th orbit, he spotted Falcon on the surface and relayed its position to Houston.

Falcon lifted off from the Moon on August 2 after nearly 67 hours on the surface, of which 18 hours, 35 minutes had been spent outside the lander. Over the next two days, the three reunited astronauts jettisoned the lunar module and sent it crashing into the Moon, conducted further orbital experiments, and released a subsatellite (PFS-1) into lunar orbit to map the lunar gravity field and study the Moon’s plasma, particle and magnetic-field environments.

Particle and Fields Subsatellite

This small satellite was designed around a hexagonal structure with a diameter of 14 inches (35.6 centimeters) that was equipped with three instrument booms. The power supply came from solar panels and chemical batteries. The instruments measured the strength and direction of interplanetary and terrestrial magnetic fields, detected variations in the lunar gravity field, and measured proton and electron flux.

The satellite confirmed Explorer 35’s finding that while Earth’s magnetic field deflects the incoming solar wind into a tail, the Moon acts as a physical barrier due to its weak field and creates a “hole” in the wind. An electronic failure on Feb. 3, 1972 formally ended the mission. Although it originally had a one-year design life, all mission objectives were fulfilled.

Return to Earth

On August 4, they fired their main engine to set course for Earth. The next day, Worden carried out the first deep-space EVA by exiting the command module and making three trips to the Scientific Instrument Module bay at the rear of the service module to retrieve film canisters and check the equipment.

Endeavor splashed down in the Pacific Ocean on August 7 some 330 miles (530 kilometers) north of Honolulu, Hawaii, about 6 miles (10 kilometers) from the recovery ship USS Okinawa. It hit the water somewhat harder than planned beca
use one of its three main parachutes failed to open. Mission elapsed time was 295 hours, 11 minutes, 53 seconds.

This was the third space flight for Scott (after Gemini 8 and Apollo 9) and the first for both Worden and Irwin. The backup crew for this mission consisted of Richard Gordon, Vance Brand, and Harrison Schmitt. Command module Endeavor is on display at the USAF Museum at Wright-Patterson Air Force Base, Dayton, Ohio.

- Credit: NASA