See listMAY 4 196767-FM1-36FM/Deputy ChiefSome things Ed Copps is worried about
Ed Copps (MIT) called the other day about some things that worry him. I figure if he's worried enough to call, it's probably worthwhile to dictate this note and send it to you.
As you recall, to help relieve our computer storage problem, we removed the automatic gimbal lock avoidance capability from CALCMANU – the space- craft computer processor which provides automatic attitude maneuvers. MIT has recently conducted a study which revealed that about 20% of the automatic attitude change maneuvers in a typical mission would now vio- late that constraint. Ed Copps has become rather concerned about this relatively high frequency. He feels that since the crew will be forced to override the computer so often they may lose confidence in CALCMANU altogether and will always choose to use the manual mode. Ed emphasized that if this were to happen, the RCS fuel requirements which their study showed to be relatively acceptable would rise drastically. Perhaps special emphasis will have to be given this matter in crew training.
One other thing that Ed was worried about at the same time was the space- craft change to lower the docking collar latch preload from 4000 lbs. to 600 lbs. This modification probably would lower the frequency of first structural mode for the CSM/LM configuration below the current estimated value of about 1.0 cps. As has been reported elsewhere, this would prob- ably require extensive redesign of the TVC Digital Autopilot filter, perhaps to the extent of requiring a completely “different control systems design” approach. This whole business apparently scares the hell out of Ed Copps, and I guess if I knew enough I would be frightened too.