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

Exploring the Unknown 183
must be a Class 1 item before the date of the MR-3 manned ballistic mission and
it seems likely that satisfactory solutions can be obtained by the present research
program and engineering drop tests.
Environmental Control System: Due to the critical role of the environmental
control system in the success of the Mercury program, a more detailed engineering
review of this system was conducted with members of the NASA Space Task Group
at Langley Field, Virginia during the days of 15 and 16 March 1961.
The idea of using a single gas, O 2
, atmosphere, in both the suit and capsule
to simplify the system appears to be reasonable from an engineering standpoint if
it meets the biomedical requirements. The environmental control system is capable
of operating completely automatically if required and still provide redundancy in
many areas against failure. In the automatic mode the only single point of failure
without backup appears to be with the emergency oxygen rate valve. However, with
man functioning in the system, this valve can be manually operated.
From the limited drawings available for inspection, good mechanical
designs practices appear to have been followed. This conclusion also is confirmed
by the results of what testing has been done to date. To the best knowledge of the
panel at the present writing, the complete unit incorporating the final design
of the ECS has not been subjected to full environmental and vibration testing.
In the absence of such testing, it is impossible a priori to categorize this critical
subsystem as a class 1 item. Such tests should be performed so that any doubts in
this area can be removed.
Automatic Stabilization and Control System: This system is not critical
for suborbital missions; it is mandatory for the later orbital missions. Both the
automatic and manual systems have in the past had peroxide corrosion [8]
problems in the valves. It is probable that new drying methods and procedural
improvements have corrected this condition. The automatic system is much more
complex than the manual, and a Class 2 categorization of the system is probably
fair. However, in the event of a failure of the ASCS, a functioning pilot can bring
the capsule in under manual control from an orbital flight.
Booster: There is a good deal of flight data on both the Redstone and
Atlas boosters. These indicate reliabilities of the order of 75 to 80%. However, the
Redstone used in the Mercury program is a modified version and a vibrational
problem was observed in the MR-2 flight. Several fixes were applied including a
filter in the control system to eliminate control vane flutter and stiffening to dampen
airframe vibrations in the control section of the booster. These fixes were tested in
the MR-BD flight of 3/24/61 and appear to have been completely successful.
The relative unreliability of boosters is not per se a cause of alarm;
booster failure will invalidate the mission, will of necessity reduce the probability
of astronaut survival, but will not necessarily reduce it below an acceptable value.
Telemetry: Some failures or outages of telemetry are to be contemplated,
most of which do not endanger the astronaut. Absence on the ground of biomedical
data (particularly if a simultaneous outage of all three communication channels