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Museum Pieces: Mercury Redstone 1, the "Four-Inch Flight" [1]
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Date: 2025-06-03
The failed MR-1 mission in November 1960, the first test flight of the Mercury-Redstone booster and spaceship, became known as the “Four-Inch Flight”.
"Museum Pieces" is a diary series that explores the history behind some of the most interesting museum exhibits and historical places.
The plug that caused the problems
The early tests of the Mercury system were plagued by failures.
In August 1959, the Little Joe 1 test of the abort system ended when an electrical problem caused the Launch Escape Rocket to fire with 30 minutes still left on the countdown clock, while the batteries were still being charged and the pad was still being evacuated. The boilerplate Mercury and the escape rocket went off to land in the ocean and were destroyed, while the solid-fueled Little Joe booster remained behind on the pad.
Then, in September, the Big Joe 1 test was intended to measure the forces imposed on the spacecraft during re-entry. This involved launching a Mercury atop an Atlas rocket. On the first launch attempt, however, the Atlas engines malfunctioned and aborted on the pad. A few days later a second attempt was made. This time the Atlas lifted off perfectly, but then the secondary stage refused to separate. (The Atlas had a configuration that was referred to as a “stage and a half”, in which the main engine and two smaller engines ignited at takeoff, and during ascent the skirt containing the small engines dropped away, leaving the main engine to continue burning.) With the extra weight of the secondary stage, the main engine struggled to reach altitude and burned up all its fuel. This in turn threw the mockup spaceship off-course, and although the heat shield functioned perfectly during re-entry and the craft was successfully recovered, NASA was concerned about the flight malfunction, and questions began to be raised about whether the Atlas was a suitable booster for manned flights.
But in July 1960 NASA went ahead with Mercury-Atlas 1, a full-up test flight with a Mercury craft mated to an Atlas booster. This test failed when the Atlas exploded one minute after leaving the launch pad.
Confident that the issues with the Atlas would eventually be worked out, NASA now went ahead with its tests of the Redstone booster, and Mercury-Redstone 1 was scheduled for November 1960. It would be an all-up test of the mated spacecraft and booster and of the launch procedures.
When the countdown reached zero, the Redstone’s engines ignited and the rocket began to lift itself off the pad. Then, suddenly, the engines shut down. The rocket, which had only traveled three or four inches, dropped back down onto the launch pad. Fortunately, it did not fall over and explode. But as it sat there on the pad, the Launch Escape System suddenly ignited, the escape rocket flew off (without the Mercury capsule), and the parachute pack in the craft’s nose popped out and draped itself along the side of the rocket.
The stunned flight controllers were unsure what to do. The Redstone was fully-armed and full of explosive fuel, and the flapping parachute could, if caught by the wind, pull the whole thing over and destroy the entire launch pad. In addition, the retro-rockets on the Mercury or the self-destruct charges in the booster could go off at any moment and ignite the fuel. It was unsafe for anyone to even approach the site to drain the fuel from the rocket.
Someone suggested, apparently seriously, that they take a hunting rifle and shoot the booster full of holes to let all the fuel out. But cooler heads prevailed, and it was decided to just sit and wait for the battery to go dead and for the liquid oxygen fuel to boil off and evaporate. It took all night.
It was a crushingly embarrassing failure. And because NASA missions were out in the open in front of the press, unlike the Soviets who did all their launches in secret and only publicized the successes, the failure happened on live TV for everyone to see. Newspaper headlines went wild (it was quickly dubbed the “Four-Inch Flight” or the “Champagne Cork”), and morale in NASA plunged.
After an investigation, NASA deduced what had happened. The booster had two plugs that were attached to the pad, one for the electrical system and one for the control system. These were supposed to be pulled out upon launch, with the control cable disconnecting first. However, on this rocket the control cable had come from a military version of the Redstone rather than the civilian versions provided to NASA, and it was slightly too long, and now did not disconnect until 29 milliseconds after the electrical plug had already been pulled.
This tiny delay caused a power surge which tripped one of the electrical relays, mistakenly telling the rocket to cut off the engines. This in turn falsely indicated that the rocket had reached altitude, which led the escape rocket to jettison itself as it would normally do. Then the Redstone’s barometric sensors found that the rocket was below 10,000 feet in elevation—which automatically triggered the drogue and main parachutes to deploy. Finally, when sensors could feel no weight being supported by the main parachute, they concluded that the main chute had failed, and deployed the reserve. The whole thing had taken mere seconds.
With the mystery solved, the issue was fixed with a new extension to ground the electrical cable, and the test was re-scheduled. The undamaged Mercury was re-used for the successful “Mercury-Redstone 1A” test flight in December.
The Redstone rocket used in the MR-1 test, on exhibit at the Marshall Spaceflight Center in Huntsville AL
Today, the failed plug from the launch is part of the collection of space artifacts at the American Space Museum and Walk of Fame in Titusville FL. The MR-1 Redstone booster is on exhibit in the Rocket Garden at the Marshall Spaceflight Center museum in Huntsville AL. The MR-1 Mercury craft was put on display at the NASA Ames Exploration Center in California. (It is currently out on loan.)
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