As an expert in the field of space exploration, I am well-versed in the history and details of various missions, including Apollo 15. Apollo 15 was indeed the fourth mission to successfully land humans on the Moon, and it was a significant milestone in the Apollo program for several reasons. This mission, launched on July 26, 1971, was notable for being the first to utilize the Lunar Roving Vehicle, or LRV, which greatly expanded the astronauts' range and capabilities on the lunar surface.

The primary objective of Apollo 15 was to explore the Hadley Rille and the Apennine Mountains, an area rich in geological diversity. The LRV was instrumental in achieving this goal, as it allowed astronauts David R. Scott, James B. Irwin, and Alfred M. Worden to cover more ground and collect a larger number of samples than any previous Apollo mission. The LRV was an electric vehicle designed to operate in the lunar environment, and it was capable of traveling at speeds up to 8 mph (13 km/h) and had a range of about 56 miles (90 kilometers) on the Moon.

The mission was divided into three main phases: the journey to the Moon, the lunar landing and exploration, and the return to Earth. The journey was made aboard the spacecraft named Endeavour, which was the first to carry the Lunar Module Pilot (Irwin) and the Command Module Pilot (Worden) to the Moon while Scott, the Commander, piloted the Lunar Module (Falcon) to the surface.

During their stay on the Moon, the Apollo 15 crew conducted three extravehicular activities, or EVAs, and collected about 170 pounds (77 kilograms) of lunar samples. These samples were unique due to the mission's landing site, which was chosen for its potential to reveal more about the Moon's geologic history. The samples included basalt and breccia rocks, which provided valuable insights into the Moon's volcanic past.

The mission was not without its challenges. Apollo 15 faced a scare when the ascent engine of the Lunar Module did not ignite on the first attempt, which could have left the astronauts stranded on the Moon. However, the crew managed to troubleshoot the issue and successfully launched back to the Command and Service Module in orbit.

Upon their return to Earth, Apollo 15 was celebrated for its scientific achievements, but it was also marred by controversy. The astronauts were accused of violating NASA regulations by carrying unauthorized postage stamps on board for later sale, an incident that became known as the "Apollo 15 postage stamps controversy." This scandal led to a significant tightening of NASA's rules regarding personal items on space missions.

In summary, Apollo 15 stands out in the history of lunar exploration for its scientific contributions and the successful use of the Lunar Roving Vehicle, despite the controversy that followed its return. The mission's legacy is one of pushing the boundaries of human exploration and setting a precedent for future lunar missions in terms of technology and scientific discovery.

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Apollo 15 was the fourth mission to land men on the Moon. This mission was the first flight of the Lunar Roving Vehicle which astronauts used to explore the geology of the Hadley Rille/Apennine region. The LRV allowed Apollo 15, 16 and 17 astronauts to venture further from the Lunar Module than in previous missions.read more >>