LM abort modes

In the continuing spirit of NASA's defence-in-depth philosophy, a series of PADs were read up to the crew that not only told them exactly when they were going to start their descent to the surface, but also what to do in the event of an abort being necessary at various times before, during and after the descent - in case the radio link were to fail. As the flights progressed, these PADs increased in complexity as planners learned from previous missions and made their procedures more elaborate. All these PADs were based around a single event, powered descent initiation (PDI) which was the moment the LM's main engine was ignited to start to slow the spacecraft and take it to the surface. Some PADs told the crew what to do if the landing was aborted before PDI, others were relevant if PDI did not occur. Yet more had details of the burns they should make if an abort was called during the descent -one relevant to the first 6 minutes, the other relevant to an abort between 6 minutes and touchdown. All these PADs were read to the crew and copied down onto forms in the checklist by the LMP.

By now, they were nearly ready to go to the Moon and pick up some rocks.

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