Exploring the Unknown: Selected Documents in ... - The Black Vault

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First Steps into Space: Projects Mercury and Gemini
Subsystem or Component
Reliability Category
Manual Control System Class 1
Retro-rocket system Class 1
Parachute Landing System Class 1
Ground Environment system Class 1
Recovery operation Class 1
Pilot and Pilot training Class 1
*Landing Bag Class 2
*Environmental control system Class 2
*Automatic Stabilization and
Class 2
Control System
*Booster (Redstone or Atlas) Class 3
*Telemetry Class 3
The starred items require a few brief remarks, which follow:
Abort Sensing and Implementation System (ASIS): In light of the
necessity to provide maximum safety to the pilot with 80% (approximately)
booster reliability, critical attention must be focused on the abort sensing system.
This system provides the warning of impending failure and automatic aborting of
the flight to avoid danger to the pilot. Within itself it is completely redundant for
reliability. Other systems, i.e., ground control and pilot over-ride provide further
redundancy in an “after the fact” manner for separating of the pilot from the
booster; however, the abort sensing system gives the earliest warning and therefore
the maximum capability of safety to the pilot in the event of an abort. Viewed in
this manner, it is imperative that this system have as high a reliability as possible.
The discussions during the ad hoc panel meetings left some questions
on the reliability of the ASIS which were not included in the NASA summary. It
has been flown open and closed loop on Atlas flights with no apparent failures
to operate as designed. The slosh problem in the last (MA-2) Atlas/Mercury
[7] flight showed roll oscillations which were near the initiating limits of the
ASIS. Admittedly, this condition is not extraordinary to expect at this stage of
development, but one of the suggested solutions to the roll rate problem may
involve changing the roll rate limits on the ASIS. If the ASIS on the Redstone
missile is ready for a manned flight and utilizes the same design philosophy as the
Atlas ASIS, then the limit settings for abort should not be amenable to change.
These functions should have been settled beyond any doubts by impending
disaster criteria and not be changed to adapt to a missile fix. It is recommended
that NASA probe again into the reliability of the ASIS to insure to themselves that
the system reliability is adequate.
Landing Bag: This buffer against landing shock performs its function well.
The steel binding straps, however, have been observed to fatigue under prolonged
wave action and the capsule has been punctured when struck by the heat shield.
Redesign and test are being vigorously pursued to eliminate these problems. This