[6] During the first docking, Pilot David Scott planned to perform an ambitious, two-hour-and-10-minute extra-vehicular activity (EVA), which would have been the first since Ed White's June 1965 spacewalk on Gemini IV.

Then he was to move back to the Gemini and test a minimum-reaction power tool by loosening and tightening bolts on a work panel.

[6] During the EVA, after Armstrong undocked from the Agena, Scott was to don and test an Extravehicular Support Pack (ESP) stored at the back of the spacecraft adapter.

This was a backpack with a self-contained oxygen supply, extra Freon propellant for his Hand Held Maneuvering Unit, and a 75-foot (23 m) extension to his tether.

Everything worked perfectly; the Agena put itself into a 161-nautical-mile (298 km) circular orbit and oriented itself to the correct attitude for the docking.

Their first course adjustment was made at one hour and 34 minutes into the mission, when the astronauts lowered their apogee slightly with a five-second Orbit Attitude and Maneuvering System (OAMS) thruster burn.

When they were over Mexico, Jim Lovell, the Houston capsule communicator, told them they needed one last correction, a 2.6 feet per second (0.79 m/s) speed addition.

At 3 hours, 48 minutes and 10 seconds into the mission they performed another burn that put them in a circular orbit 15 nautical miles (28 km) below the Agena.

Shortly before radio blackout, Mission Control cautioned the astronauts to immediately abort the docking if any abnormalities occurred with the Agena.

Scott switched the Agena control back to ground command, while Armstrong struggled to stabilize the combined vehicle enough to permit undocking.

Scott then hit the undock button, and Armstrong fired a long burst of translation thrusters to back away from the Agena.

Planes were also dispatched, and U.S. Air Force pilot Les Schneider spotted the spacecraft as it descended precisely on time and on target.

After release, they were brought by limousine to waiting helicopters where they flew to Kadena Air Base and then on to Florida on a C-135.

As part of the investigation into the mishap, ground controllers tested the Agena stage for the next several days by ordering it to perform various in-orbit maneuvers until exhausting its propellant and electrical power.

Four months later, the crew of Gemini 10 rendezvoused with the inert Agena and astronaut Michael Collins retrieved its micrometeorite collector.

Quote from Flight: My Life in Mission Control by Chris Kraft, page 256: Engineers tore into the OAMS system when the spacecraft got home and found a short circuit that made one thruster fire continuously.

The OAMS was rewired so that a short circuit would always give us a dead thruster, not one that kept firing until a circuit breaker was opened by an astronaut.The Deputy Administrator of NASA, Dr. Robert Seamans, was attending a celebratory dinner sponsored by the Goddard Space Flight Center, at which Vice President Hubert Humphrey was the guest speaker, when the problem arose.

It declared: "It is NASA policy to investigate and document the causes of all major mission failures which occur in the conduct of its space and aeronautical activities and to take appropriate corrective actions as a result of the findings and recommendations.

This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.