Terminal Countdown Demonstration Test

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The Terminal Countdown Demonstration Test ( TCDT ) is an important part of the preparation for the launch of US rockets, especially the space shuttle . He gives the crew and the launch control teams one last opportunity to familiarize themselves with the equipment for the flight, the launch procedures and the safety precautions at the launch site.

Sequence of a TCDT on the space shuttle

The exact process varies from mission to mission, but remains basically the same.

On the first day, the crew lands in their T-38 jets on the Shuttle Landing Facility at the Kennedy Space Center , where they are greeted by the press and the heads of the KSC. If there is still enough time, the crew inspects the space shuttle's payload bay. Otherwise this will take place the following day. In the evening, the commander and pilot go to the Shuttle Landing Facility again to simulate a few landings in the Shuttle Training Aircraft . They wear their take-off and landing suits.

The second day takes place entirely at the launch pad. If it was not possible the day before, the payload bay will first be examined on that day. This is followed by a briefing and demonstration of the safety precautions on the launch pad. After that, the crew traditionally gives a press conference before they learn how to use the rescue tank. On this day, too, the commander and pilot make test approaches.

The third day is used to simulate a start with subsequent RSLS abort for the crew of the shuttle, the start and mission control center. The simulation starts at T-3h and Counting and ends with a simulated shutdown of the main engines at T + 8m. Then the RSLS demolition simulation begins, during which the shuttle crew goes to the cable car rescue system demonstrated the day before and triggers it. However, they do not leave as this saves the time to fetch the gondolas back. On the same day, but no later than the following day, the crew leaves the KSC and returns to the Lyndon B. Johnson Space Center .

TCDTs on unmanned missiles

TCDTs also take place with unmanned rockets. In contrast to the Shuttle-TCDT, only the countdown simulation takes place.

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