Mercury-Atlas 6

18 February 2021 3854 view(s) 7 min read
Mercury-Atlas 6

Mercury-Atlas 6 header

Mercury-Atlas 6

Mercury Atlas 6 launch

Mercury-Atlas 6 was the very first American orbital spaceflight, which took place on February 20, 1962. Astronaut John Glenn piloted Friendship 7 spacecraft, and NASA operated the mission as part of Project Mercury. It was the fifth ever human spaceflight. 

Glenn boarded Friendship 7 on February 20, 1962, at 11:03 UTC, following a 90-minute delay due to the necessary replacement of a faulty component in the spacecraft's guidance system. The hatch was bolted in place just over an hour later, and the spacecraft was launched at 14:47 UTC after another two hours of holds. As the Atlas rocket and Friendship 7 reached maximum dynamic pressure, aka max Q, and Glenn reported, "It's a little bumpy about here." Soon after, the flight smoothed out, and two minutes and 14 seconds after launch, the booster engines cut off and dropped away. Then, right on schedule, at two minutes and twenty-four seconds, the escape tower was jettisoned. After, the Atlas rocket and the Friendship 7 spacecraft pitched over further, giving Glenn his first view of the horizon. He described the view as beautiful, looking eastward across the Atlantic. By 14:52 UTC, Friendship 7 was in orbit. Glenn received word that the Atlas rocket had boosted the MA-6 into a trajectory that would hold for at least seven orbits. However, computers at the Goddard Space Flight Center in Maryland indicated that the MA-6 orbital parameters appeared good enough for almost 100 orbits. 

John Glenn looking at Friendship 7 noseartFriendship 7 then began its first orbit with all systems go. While crossing over the Canary Islands in the Atlantic, controllers reported all capsule systems in perfect working order. Later Glenn told the tracking station team that he could see a dust storm while over Kano, Nigeria. Kano flight communicators told him that the winds had been quite heavy for the past week. During this time, Glenn took control of the spacecraft and started a major yaw adjustment. Glenn noticed that the attitude indicators did not display what he observed was the real spacecraft attitude, but regardless he was pleased to be facing forward on his orbital path.

While transversing over the Indian Ocean, Glenn observed his first sunset from orbit. He reported the sky in space was very black with a thin band of blue along the horizon. Glenn also noted in his opinion the sun had set quickly, but not as fast as he had expected. There was a reduction in light intensity for five or six minutes, and brilliant orange and blue layers spread out on both sides of the sun, spreading gradually toward the horizon.

John Glenn during Prelaunch activitiesNearing the Australian coastline, as he continued his journey on Earth's night side, Glenn made landmark, weather, and star observations. He looked for but failed to see zodiacal light, the dim light phenomenon because his eyes didn't have enough time to adapt to the darkness. The spacecraft came into the Mercury Tracking Station's radio range in Muchea, Australia, where Glenn reported that he felt fine, and there had been no problems but that he saw what he thought was the outline of a city. The site operator informed Glenn that he was most likely looking at Perth's city lights and the satellite town of Rockingham. This was correct; many people in Perth had turned their lights on to be visible as Glenn passed over.

After this, Glenn had a short 45-minute "night" and prepared to view his first sunrise from orbit from the periscope. As the sun rose, he saw thousands of little sparkling specks floating outside the capsule. He was concerned and momentarily felt that the spacecraft was tumbling or that he was looking into a starfield. However, a good look out of the window corrected this, and he became sure the "fireflies" he saw were streaming past his spacecraft from ahead. They didn't seem to be coming from the spacecraft, and they quickly disappeared as Friendship 7 moved into direct sunlight. It was later found that this visual phenomenon was probably small ice crystals venting from onboard spacecraft systems. 

Glenn entering Friendship 7 pre-launchFlight systems controller Don Arabian, as Friendship 7 crossed Cape Canaveral for the start of the second orbit, noticed that "Segment 51", a sensor providing data on the spacecraft landing system, gave an odd reading. The sensor was indicating the landing bag and heat shield were no longer locked in position. If this were true, the heat shield was only held to the spacecraft by the retro package's straps. All tracking sites were ordered by Mercury Control to monitor "Segment 51" closely and advised Glenn to ensure the landing-bag deploy switch was in the "off" position. Glenn became suspicious when site after site asked him to make sure that the landing-bag deploy switch was off but was not immediately aware of the problem. During this time, Friendship 7 was crossing the Atlantic for the second time. Still, Glenn was busy manually keeping the spacecraft's attitude correct and trying to accomplish as many of the flight plan tasks as possible. 

Glenn's spacesuit temperature was too warm and had been steadily increasing since the second orbit's start. He tried to adjust the internal suit temperature as he crossed the Indian Ocean, but upon approaching Woomera, Australia, a warning light came on, signaling him of excess cabin humidity. Glenn had to balance his suit for the rest of the flight carefully. Another warning light came on while he was still over Australia,  indicating that the automatic control system's fuel supply was just above half. Mercury Control then recommended Glenn let the spacecraft drift to conserve fuel. There were no problems for the remainder of the second orbit for Friendship 7. Glenn continued to manually control the spacecraft's attitude, not letting it drift too far out of alignment. However, in doing so, he consumed more fuel than the automatic system would have.

Glenn in orbit inside Frienship 7The third orbit of Friendship 7 was uneventful and was focused primarily on preparing for re-entry. The spacecraft lost altitude in its re-entry glide over the continental United States as it headed toward splashdown in the Atlantic. Glenn heard noises that sounded like something was brushing against the capsule as he passed over the Texas tracking station. A strap from the retro package had broken partially loose and was hanging over the spacecraft window as it was consumed in the re-entry plasma stream. The spacecraft control system was working optimally, but the manual fuel supply was down to 15 percent, with the peak of re-entry deceleration was still to come. Glenn, at this point, switched to fly-by-wire and the automatic tank supply. This combination had more available fuel. 

The spacecraft was after that experiencing peak re-entry heating, and Glenn reported he thought the retro pack had jettisoned when he saw chunks coming off and flying by the window. He feared the fragments he was seeing were disintegrated heat shield pieces. The chunks he saw were pieces of the retro package breaking up in the re-entry fireball. Friendship 7 began oscillating severely after passing the peak g region, and Glenn could not control the ship manually. The spacecraft was oscillating over 10 degrees on both sides of the vertical zero-degree point. Glenn later said he felt like a falling leaf during that event. He activated the auxiliary damping system, which helped stabilize the oscillation. However, fuel in the automatic tanks was getting low. 

Friendship 7 on display in National Air and Space MuseumThe automatic fuel supply ran out quickly, and manual fuel ran out a minute later, just before drogue chute deployment, and the oscillations resumed. Glenn decided to deploy the drogue chute at 35,000 feet (10 km) to regain attitude stability manually, but just before he was able to reach the switch, at 28,000 feet (8.5 km), the drogue chute opened automatically instead of the programmed 21,000 feet (6.4 km). The spacecraft regained stability, and Glenn reported that everything was in good shape afterward. The periscope opened at 17,000 feet (5 km) and was available for him to use. Glenn attempted to look out of the overhead window instead, but it was coated with so much film and smoke that he could see very little.

Friendship 7 splashed down 40 miles (64 km) short of the planned landing zone in the North Atlantic. Retrofire calculations had not taken spacecraft weight loss due to the use of onboard consumables into account. A destroyer from the US Navy, the USS Noa, had spotted the spacecraft when it was descending on its parachute and reached the Friendship 7 capsule 17 minutes after splashdown. Once the spacecraft was on deck, Glenn attempted to leave the spacecraft through the upper hatch, but it was too hot inside for him to reach it. Instead, Glenn decided to blow the side hatch; he told the ship's crew to stand clear, and he hit the hatch detonator plunger with the back of his hand. The detonator plunger recoiled and cut through his glove, and injured his knuckles. The hatch came off with a loud bang, and the first U.S Navy Seal, Harry Beal, pulled Glenn out of the spacecraft. A smiling Glenn exited Friendship 7, and his first words back on Earth were, "It was hot in there!"

During this mission, the achievements made set the tone for the future of space travel. Without the success of this first Mercury orbital spaceflight, the Gemini, Apollo, and Space Shuttle programs that followed may never have been possible.