More Details for 1965-12-09
Original archive entry. The text, images and links below are kept as they were written.
Fire-till-touchdown not feasible for the Apollo LEM
Preliminary results of the "fire-till-touchdown" study by Grumman indicated that this maneuver was not feasible. The engine might be exploded by driving the shock wave into the nozzles.
The base heatshield temperature would exceed 1,789K (5,000 degrees F), which was high enough to melt portions of the structure, possibly causing destruction of the foot pads. The allowable pressure on the nonstructural elements of the base heatshield would be exceeded; and the descent engine flow field would tend to cause a "POGO" effect which would cause landing instability and could prevent engine cutoff.
As an outgrowth of the study, the landing probes would have to be made longer (137.1 to 187.9 cm (54 to 74 in) with automatic cutoff, 228.6 to 304.8 cm (90 to 120 in) with manual cutoff). The probe switches would be moved from the tip of the probe to the base, which was objectionable from the standpoint of a possible false reading due to probe dynamics.