NASA Apollo 6 paved America's Pathway to the Moon

ATLANTA -- As America recalls the golden anniversary of mankind's first voyage to the moon this December, the lesser known flight of Apollo 6 cleared a major hurdle for NASA as it paved the country's pathway toward lunar orbit.

Designed as a test flight article and flew unmanned, the flight of Apollo 6 fifty years ago tested not just the spacecraft itself, but launched the largest rocket America ever flew on a second and final critical mission to ensure the astronauts safety.

Today, the Apollo 6 command module rests at the Fernbank Science Center in East Atlanta. The spacecraft is on public display at the science center and remains a testament to the Earth orbiting test flight which flew on April 4, 1968.

The launch of the second Saturn 5 with Apollo 6 (AS-502) a top lifted-off at 7:00:01 a.m. EDT, from Florida's Kennedy Space Center. The nearly 365-foot tall rocket darted into a blue morning sky without a crew, however loaded with a wealth of science instruments and video cameras for engineers to reseach in the months that followed.


Once launched, flight controllers began to notice the rocket was shaking a bit as it ascended through the atmosphere. The five massive F1 engines at the base of the rocket's first stage performed well for the first two minutes, and then, according to a 1968 NASA memo, "there were thrust fluctuations that caused the vehicle to bounce like a giant pogo stick for about 30 seconds."


Higher than planned G-forces were recorded aboard the computers located inside the command module. "Except for the bouncing and the loss of a piece of the panel in the adapter, the first stage did its job," NASA added.

Engineers call it a POGO effect, an up and down vibration in the rocket's first stage which added seven-tenths extra G-forces. It was enough of a shake to have impaired a crew's vision had they been on board.

The Saturn 5's erratic first stage then separated on time and the controllers noticed the second stage began to shake as well as the rocket flew faster and faster. Two of the second stage's five J-2 engines then shut down by an abort system due to a liquid hydrogen fuel line which broke due to the continuation of the POGO effect. This prevented the spacecraft from achieving its planned orbit insertion of 177 km.

On the next Saturn 5 flight that December, engineers added more helium to the oxygen fuel lines to stabilize the engine's vibrations. It worked and the rocket sped all the way to lunar orbit as Frank Borman, James A. Lovell, and William Anders became the first humans to reach the moon aboard Apollo 8.

The thrust of AS-502s launch on April 4, 1968. (NASA)

One other issue was discovered in post flight data analysis. The support beam for the center engine of the second stage shifted nearly 18 inches, according to flight director Chris Kraft, "and came perilously close to structural failure".

Kraft states in his book Flight (2001) that "if a beam broke, the the entire second stage would fail catastrophically. It would explode." This shaky dress rehersal flight was providing engineers with enough data to smooth out several issues in time for the next launch -- Apollo 7 and its three person crew.

Apollo flew up to 228 miles above Earth and sailed upon the ocean of space much like a boat being checked out before she carries a crew. After nearly seven full orbits of our planet, the craft reentered the atmosphere and splashed down at 5:23 p.m. -- nearly 10 hours after launch. It was then recovered by the U.S.S. Okinawa five hours later, and 80 km off target, in good condition.

Once you view the exciting exhibits at Fernbank, you discover the spacecraft resting near the center's planetarium. As you view the module, be sure to examine the underneath region of the space craft known as the heat shield.

It is this region which withstood around 2,500 degrees of heat caused by friction as it hit earth's atmosphere on the way home. Peer inside the craft through it's single window; and scan the thrusters located around it's base.

Since the mid-1970's, the Apollo 6 module has been a fixture of the Fernbank Science Center. Visitors can pause to reflect on the center's own piece of space history with one of the spacecraft which paved the way for deep space travel.

"Having a spacecraft of U.S. and world aerospace history at Fernbank Science Center on its 50th Anniversary is a great honor," Fernbank's Exhibit Designer Tony Madden said. "We understand the sacrifices, dedication, and achievements this Apollo command module represents."

NASA Apollo 6 CM rests today at Fernbank Science Center, Atlanta. (Atkeison)

As the late Dr. Ralph Buice of Fernbank recalled many years ago, during many of the crewed Apollo flights to the moon, it was the telescope at Fernbank which aided in the tracking of the spacecraft. A special image intensifier, he pointed out, was borrowed from Cape Canaveral.

"Fernbank astronomers attached the intensifier, which was capable of increasing the light gathering power of a telescope over 100,000 times, to the back of the 36-inch telescope in the observatory using high resolution television cameras and a fiber optics system," Dr. Buice said. "When the telescope was pointed in the direction of the Apollo and the intensifier turned on, the spacecraft appeared on the television screen traveling through a shining field of stars."

The video was so good that the networks used the telescope video both live and in playback mode during the news.

"As a result of Fernbank Science Center’s contributions to the space program and the tracking of the Apollos, the Smithsonian Institution provided the Apollo 6 spacecraft for display in Fernbank’s exhibit hall in appreciation," he added. The spacecraft has remained at the center for 45 years.

(Charles A. Atkeison reports on aerospace and science. Follow his updates on social media via @Military_Flight.)