NASA Office of Logic Design

NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.

Memory Requirements for the Launch Vehicle Digital Computer (LVDC)

J.J. Rocchio
Bellcomm, Inc.

April 25, 1967



The Launch Vehicle Digital Computer (LVDC) has a modular memory system with a maximum capacity of eight modules. Each module has 16 sectors, for a total of 28 sectors (64 duplexed sectors) in all.

Memory requirements have grown to the point that, although four modules were flown on AS 201, eight are planned for AS 501-504. The possibility of depletion of all memory reserves has led to:

  1. studies of memory augmentation methods;
  2. reevaluation of current and anticipated memory requirements;
  3. consideration of some reprogramming to utilize memory more efficiently.

At this time, expected reserve capacity in the LVDC memory is about 18% (12.9 sectors duplex) of total capacity for AS 501, and only 11% (6.9 sectors duplex) for AS 504. This is considered insufficient to provide an adequate margin for new requirements and contingencies. It is therefore recommended that the memory savings identified in the IBM LVDC Memory Utilization Study as being "readily obtainable" be implemented. This action would increase the reserve to 31% (19.6 sectors duplex) for AS 501 and 24% (15.2 sectors duplex) for AS 504. Additional study of future Saturn operations is needed to establish requirements for a Saturn V Auxiliary Memory Unit.

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