Quick Thinking Demonstrated Value of the Human Element

By Bob Granath

In late 1966, the final Gemini mission was launched into the skies over Cape Kennedy Air Force Station. At Mission Control in Houston, Dr. Chris Kraft, NASA’s director of Flight Operations, turned to Dr. Robert Gilruth, director of the agency’s Manned Spacecraft Center, and said, “Thank God we never had to use those ejection seats.” But, if not for a test pilot’s quick thinking, two astronauts would have during an attempt to launch a Gemini mission a year earlier.

Gemini VI turned out to be one of the most harrowing moments in the history of America’s still young space program. On Dec. 12, 1965, all had proceeded well right up to ignition of the twin Titan II rocket’s first stage engines. Astronaut Alan Bean was serving as capsule communicator, or capcom, in Mission Control in Houston.

“3, 2, 1, ignition . . .  we have a shutdown Gemini VI,” he said.

After about 1.5 seconds of firing, the rocket’s engines abruptly stopped. While there was no liftoff, cockpit instrumentation indicated the rocket had launched. If that were true, the rocket would fall back to the launch pad in a catastrophic fireball.

Mission rules dictated that command pilot Wally Schirra immediately pull a D-shaped ring and activate the ejection seats, blasting him and fellow astronaut Tom Stafford safely away from the fully fueled Titan rocket. However, Schirra’s experience from his Mercury 8 flight in 1962 paid off.

“I knew we hadn’t gone anywhere,” he said in 1990 as I spoke to the veteran of Mercury, Gemini and Apollo during a reception at the opening of the U.S. Astronaut Hall of Fame.

He did not feel the motion of liftoff. Therefore, the consummate test pilot chose not to eject.

“This proves that man is better programed than any computer,” he said.

Later Stafford would say. “I looked over at Wally. He wasn’t doing anything, so neither did I.”

During the flights of Project Mercury, America’s first human spaceflight program, an escape tower atop the spacecraft could have pulled the capsule with the astronaut aboard to safety away from a failing or exploding rocket. Parachutes would have lowered the capsule to a splashdown off shore from the Florida spaceport. In the mid-1960s, a similar system was being planned for the upcoming Apollo lunar landing program.

For the two-man Gemini spacecraft, ejection seats were installed for emergencies on the launch pad or during the early launch phase to an altitude of 15,000 feet. After a ground command or one of the astronauts pulling a D-shaped ring, military-type jet ejection seats would have propelled the crew up and out of the spacecraft. Parachutes then would open allowing a safe landing in the Atlantic Ocean for recovery by rescue crews.

Schirra expressed doubts about the ejection seat system.

“My main concern was the rockets on the base of the ejection seats would be firing into a spacecraft cockpit that had been soaked with pure oxygen for the better part of an hour and a half,” he said.

In a NASA oral history interview in 1997, Stafford expressed a similar view.

“We would have been two Roman candles going out because we were (in a spacecraft at) 15 or 16 psi, pure oxygen soaking the cockpit,” he said. “It would have, at least, burned our (pressure) suits.”

Schirra explained that the checkouts of the ejection seats had been limited.

“They did have some tests at (Naval Air Weapons Station) China Lake (near Ridgecrest, California) where they had a simulated mock-up-up of Gemini capsule (on a rocket sled), but what they did was fill it full of nitrogen,” Schirra said. “They didn’t have it filled full of oxygen in the sled test.”

Prior to Apollo, Mercury and Gemini astronauts flew in capsules in which the environmental control system provided pure oxygen for breathing air. That changed after an electrical spark in the Apollo 1 cockpit, pressurized with pure oxygen, erupted into an inferno. The blaze took the lives of the crew of Gus Grissom, Ed White and Roger Chaffee.

“We now know about the dangers of (pure) oxygen in the fire on Apollo 1,” Schirra said. “Would (the rockets of the ejection seats) cause a fire or explosion?”

Rendezvous and Docking

The original plan for Gemini VI was to launch an unpiloted Agena upper stage atop an Atlas rocket on Oct. 25, 1965. As the target vehicle completed its first orbit, a Titan II rocket was to lift off with Schirra and Stafford aboard. Gemini VI then would rendezvous and dock with the Agena.

After the Atlas rocket lifted off, the Agena’s secondary engines fired to separate it from the launch vehicle. However, immediately after the Agena’s primary engine fired, telemetry was lost and the target vehicle failed to reach orbit. The launch of Gemini VI was postponed.

Since the next Agena target vehicle would not be ready for several months, a new plan began to take shape for Schirra and Stafford.

According to “On the Shoulders of Titans: A History of Project Gemini,” Walter Burke, spacecraft chief at McDonnell Aircraft Corp., and his deputy, John Yardley, asked, “Why couldn’t we launch a Gemini as a target instead of an Agena?” McDonnell was the contractor that built the Gemini spacecraft.

NASA officials at the agency’s headquarters in Washington D.C., Cape Kennedy (now Cape Canaveral) and the Manned Spacecraft Center (now Johnson Space Center) quickly began drawing up a plan to orbit Gemini VII on its planned two-week mission and, if there was no serious damage to Launch Complex 19, send up Gemini VI to rendezvous.

The Gemini VII crew of astronauts Frank Borman and Jim Lovell lifted off from Cape Kennedy on Dec. 4, 1965. The 14-day Gemini VII mission was an effort to better understand how humans adapt to prolonged periods of microgravity.

As the rocket exhaust from the Gemini VII liftoff began to clear, teams were standing by to begin preparing for Gemini VI. It was a record turnaround between missions launched from the same pad. The countdown proceeded smoothly until the unexpected shutdown as the Titan rockets engines began building up to 430,000 pounds of thrust.

In the tense moments following the Gemini VI engine shutdown, capcom Bean reported that launch vehicle safing was underway and launch pad crews soon would return to assist the two astronauts.

“Gemini VI, Be advised, it will be about approximately 20 minutes before we can get out there,” Bean said.

“That’s OK,” said Schirra. “We’re just sittin’ here breathing.”

Bean also reported that launch controllers believed they had pinned down the primary cause of the engine shutdown.

“Initial evaluation is the possibility a tail plug may have fallen off,” he said.

Schirra explained the “tail plug” was an electrical cable attached to the bottom of the Titan II rocket. At liftoff, the motion of the rocket going up simply unplugs itself. Once disconnected, the cable sends a signal to the cockpit instrument panel, the blockhouse near the launch pad and to Mission Control that liftoff had taken place.

“That’s why we had the signal that liftoff had occurred,” Schirra said.

In the minutes after the aborted launch, crews returned the gantry-like erector around Gemini VI and the Titan rocket. They assisted Schirra and Stafford out of the spacecraft, while other ground crews confirmed an electrical plug prematurely dropped off the base of the booster. For future launch attempts, the plugs were designed to better stay in place.

Another Problem

“The cable coming unplugged at ignition wasn’t the only problem,” Schirra said.

Engineers, including Ben Hohmann of the Aerospace Corporation, carefully scrutinized telemetry from the first stage’s two engines and found a second issue. Aerospace was the contractor responsible for monitoring launch vehicles.

Schirra explained in his 1988 book, “Schirra’s Space,” that Hohmann noticed that the Titan rocket began experiencing thrust decay before the plug dropped off. Additionally, fuel was leaking out of a pressure relief valve. Engine number 1 nearly reached 100 percent thrust at shutdown. However, engine number 2 never transitioned to in-flight performance levels.

A technician inspecting the rocket engines at the launch pad identified the problem. At the Titan rocket’s prime contractor, Martin Marietta, in Baltimore, Maryland, a small, plastic dust cover was left inside the gas generator when the first stage booster was assembled months earlier. The dust cover blocked the flow of oxidizer and that, too, would have caused an engine shutdown.

It is unclear if that would have occurred before or after liftoff.

According to NASA’s “Launch Vehicle No. 6 Flight Evaluation,” had the inadvertent electrical plug disconnect not occurred, the emergency detection system would have sent a shutoff command to the Titan at T + 2.2 seconds due to the loss of engine number 2 chamber pressure. Since launcher release and liftoff would not take place until T + 3.2 seconds, the report said, a pad fallback still would not have occurred in this scenario and the astronauts would have been safe.

Schirra believed a shutdown caused by the dust cover would have occurred following liftoff.

“The dust cover would have caused an engine shutdown about the time we cleared the (Launch Complex 19) tower,” Schirra wrote in his book. “Then, we would have had to eject. I still breathe a sigh of relief thinking about how close we came.”

‘Cool Precision Under Stress’

Many in NASA’s leadership had high praise for Schirra’s reaction to the launch abort. These include the agency’s Administrator Mike Griffin responding to news of the former astronaut’s death on 2007.

“The fact that the mission flew at all will be known as a testimony to Wally’s cool precision under stress,” he said. “Gemini VI experienced the first on-pad engine shutdown in human spaceflight history. The crew stayed onboard, saving the mission and quite possibly the program.”

During an interview with Schirra at the San Diego Air & Space Museum on Sept. 24, 1999, British author Robert Godwin asked Schirra why he didn’t pull the eject handle. As is the usual case, heroes downplay their achievement.

“On Gemini VI, the booster acted strangely,” Schirra said. “I had a flight before. There were only a few people who flew before. I’m only the third person after Grissom and (Gordon) Cooper who was having a second flight. I knew what if felt like to liftoff. I knew right away, even though I had all the electronic signals that I had liftoff — the (mission elapsed time) clock had started, launch control said liftoff, Mission Control confirmed liftoff. I knew we hadn’t had liftoff.”

By the day after the second Gemini VI postponement, NASA and Martin Marietta officials were confident another launch attempt could be scheduled for Dec. 15, 1965. This time Schirra and Stafford were successfully on their way completing the first-ever rendezvous between two spacecraft in orbit. It was a transformative capability that was not only necessary for the Apollo Moon landing missions, but also crucial in building and operating the International Space Station.

The simultaneous flights of two piloted spacecraft also were major strides forward in advancing NASA’s capabilities in human spaceflight. Additionally, the dual missions of Gemini VII and Gemini VI marked the point in which the United States clearly pulled ahead in the space race with the Soviet Union leading to the Apollo missions to the Moon.

© 2024 SpaceAgeChronicle.com All Rights Reserved