Mercury Redstone-1

The purpose of the MR-1 flight was to test the Mercury and Redstone spacecraft in a suborbital mission. This flight would also test the automation of the spacecraft and landing systems, as well as the launch, tracking, and search and rescue operations on the ground ^{[3] [4]} . The flight would also test an automatic emergency rescue system (CAC), which would operate in open loop mode. This meant that (CAC) should report on the situation requiring an emergency termination of the flight, but not stop the flight itself. Since there was no astronaut in the capsule, this was not a safety problem, and the pilot would have assessed the situation - to stop or not the flight itself.

The mission used the spacecraft Mercury No. 2 and the Redstone-1 launch vehicle. NASA used the "MR-" prefix for both the Mercury-Redstone missions and the numbering of the launch vehicle. Sometimes, as in this case, the mission and numbering of the launch vehicle coincided, but this was not always the case. The first launch attempt was scheduled for November 7, but was canceled due to problems in the last minute with the capsule, so the launch was postponed to November 21. ^{[5] [6]}

That day, after a normal countdown, the Mercury-Redstone engine started at 9:00 AM Eastern time (2:00 PM GMT). However, the engines died out immediately after the start. The rocket climbed only 4 inches (10 cm) and landed on the launch pad. She swayed a little, but remained upright and did not explode. It was very strange ^{[4] [5] [7]} .

Immediately after the Redstone engines stopped, the CAC engines of Mercury worked and the tower flew off, leaving the capsule attached to the rocket. The SAS tower rose to a height of 1,200 m and landed at a distance of 370 m. Three seconds after the operation of the SAS engines, the capsule fired a parachute; then the main and reserve parachutes fell, and the radio antenna came out ^{[4] [5] [7]} .

In the end, everything froze. Meanwhile, a fully-fueled, slightly trembling Redstone rocket and a Mercury capsule stood on the launch pad ready for launch. Among the pyrotechnics there was a brake capsule DU, and the Redstone rocket itself could self-destruct, whose system was still active. In addition, the main and reserve capsule parachutes tilted the rocket, threatening to tip it if they caught enough wind. Fortunately, the weather was favorable. The technicians had to wait until the next morning when the batteries in the rocket and capsule sat down and Redstone's liquid oxygen evaporated. Only then could they start working with a safe rocket ^{[5] [8]} .

The study showed that Redstone’s engine shutdown was due to two electrical cables that had come off in the wrong sequence. These were a control cable that provided various data and rocket control, and a power cable that provided battery power. Both cables were connected to the rocket in the regular place of one of its keels and separated at launch. The control cable was supposed to separate first, then the power cable. For this launch, the control cable was longer than necessary - this was designed for the Redstone military rocket, for the Mercury-Redstone a shorter one was enough. The control cable was clamped to compensate for its length, but when the rocket started, the clamp did not work and the control cable did not separate. As a result, the control cable separated approximately 29 milliseconds after the power ^{[7] [9]} .

During this short interval, a power outage caused a substantial current to flow through the electrical relay, which was supposed to give a command to stop the engines, as at the end of the flight. This triggered relay issued a command to the rocket to shut off the engines and sent a signal to the capsule about their "normal shutdown." Under normal circumstances, when the capsule received this signal during the flight, two things would happen: the shooting of the SAS tower, which was no longer needed, and after the rescue tower was gone, the capsule would separate itself from the spent rocket. In the case of MP-1, the capsule actually shot the tower, as it was planned, but did not shoot itself from Redstone. The system was designed so that this separation occurs only after the acceleration of the rocket has almost ceased so that the capsule is not shot down by the still accelerating launch vehicle. Separation would occur if capsule acceleration sensors detected overload as tending to 0 g, as if the engines had stopped and the rocket began to fall freely. However, in the case of MP-1, Redstone was not in free fall, but stood on the launch pad. In such a situation, the sensors determine such an “acceleration” as a constant 1 g. Because of this acceleration, the capsule and rocket did not separate ^{[4] [10]} .

SAS turret firing activated the capsule parachute system. Since the altitude was below 3,000 m, the atmospheric pressure sensors issued a command to work in the usual sequence, the brake parachute was thrown first, then the main one. But since the main parachute did not support the weight of the capsule, the parachute system “did not feel” the load on the slings, the automatics considered that the main parachute failed and deployed a reserve parachute. Since the automation regarding the “sensation of abnormal termination of work” of Redstone engines in this flight was in the “open loop” version, the engine shutdown did not cause the CAC to trip. However, the system reported an abort condition, so it functioned properly. ^{[7] [9]}

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  Before the start.

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  MP-1 at the time of “Ignition”

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  MP-1 triggering SAS

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  Ship No. 2 used in the flights of MP-1 and MR-1A

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  Ship number 2 in 1959

• Gemini