Apollo 10 was Rehearsal for Upcoming Moon Landing

‘America to the Moon’ Part 8 – The Way is Paved for a Lunar Landing

By Bob Granath

NASA recently marked the 50th anniversary of Apollo 10, the mission that served as the “dress rehearsal” for the first lunar landing two months later. The crew descended to within 47,000 feet of the Moon ensuring all was working as designed prior to making the actual touchdown.

Apollo 10 was the fourth piloted mission in the lunar landing program, testing all the procedures and components without actually landing on the moon. The mission included an all-up test of the lunar module (LM) by the second crew to orbit the Moon.

During a pre-launch briefing at NASA’s Kennedy Space Center in Florida, Apollo 10 commander Tom Stafford commented on the goals of Apollo 10.

“It will tie together all of the knots that we’ve had in the past, try to sort out the unknowns and actually pave the whole way for the lunar mission,” he said. “We’ll do everything exactly as the landing mission except the final descent on the surface and the ascent into orbit.”

On May 18, 1969, the veteran crew of Stafford, John Young and Gene Cernan became the first to lift off Launch Pad 39B at Kennedy.

Stafford was pilot on the Gemini VI rendezvous mission in December 1965 and commanded Gemini IX with Cernan in June 1966. On Gemini IX, Cernan performed America’s second spacewalk. John Young was pilot on Gemini III in March 1965 and commanded Gemini X in July 1966.

During Apollo 10, the first color television transmissions to Earth began three hours after launch when the spacecraft was 3,570 miles from Earth. On the three earlier Apollo flights, only black and white transmissions were possible.

As they arrived in lunar orbit three days later, the trio came from the backside of the Moon and spotted their home planet rising above the lunar horizon.

“We just saw Earthrise and it was magnificent,” Cernan said.

On May 22, Stafford and Cernan boarded the LM which they had named “Snoopy,” after the Peanuts comic strip character. They undocked from the command module, named “Charlie Brown,” leaving Young orbiting about 60 miles above the Moon.

The LM’s descent propulsion system engine was fired for 27 seconds, dropping down to a mere 47,400 feet above the lunar surface.

“We is down among ’em, Charlie,” Cernan said to fellow astronaut Charlie Duke, serving as spacecraft communicator in Mission Control at the Manned Spacecraft Center (now Johnson Space Center) in Houston.

On the next mission, the final powered descent to landing would begin from this altitude.

“It’s a fantastic sight,” Stafford said observing the Moon’s terrain. “It has different shades of browns and grays.”

He and Cernan surveyed and photographed the Sea of Tranquility landing site chosen for Apollo 11, and practiced the approach that would refine knowledge of the lunar gravity needed to calibrate the powered descent guidance system for a landing.

Upon separation of the ascent stage, Stafford and Cernan rode out a momentary gyration in the lunar lander’s motion due to a faulty switch setting. They then fired the ascent engine boosting them to a rendezvous and docking with Young in the command module.

The mission put NASA’s flight controllers and extensive tracking and control network through a rehearsal. Except for the touchdown on the moon, the mission went exactly as a landing would have gone, both in space and on the ground.

While all lunar missions entered the atmosphere at similar speeds, Apollo 10 set the record for the highest velocity attained to date by a piloted vehicle at 24,791 mph during reentry.

Describing the view out the window, Cernan said the re-entry was like being in “a ball of white and violet flame.”

Splashdown occurred in the Pacific Ocean on May 26, 1969, with the astronauts and spacecraft recovered by the aircraft carrier USS Princeton.

Noting that successful completion of Apollo 10 led to the next flight being the first to attempt to achieve President John F. Kennedy’s goal of landing on the lunar surface, NASA Associate Administrator for Manned Spaceflight, Dr. George Mueller, had high praise for the agency’s team.

“Congratulations on a job well done,” he said. “Apollo 10 is a magnificent step towards our immediate goal of landing men on the Moon. I would like to ask you to pass on to each of the people of your organization my sincere appreciation for the dedication and perseverance that has led us to the threshold of landing men on the Moon.”

EDITOR’S NOTE: This is the eighth in a series of feature articles marking the 50th anniversary of NASA’s Apollo missions to the Moon. During the 1960s and early 1970s, the space agency and its contractors sent astronauts from Earth beginning a period of exploration that will lead to pioneering flights planned for the 21st century. Next, read about the historic mission that met President John F. Kennedy’s goal.

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