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

Exploring the Unknown 249
The Mercury program taught us not to stack the components on top of
each other. It forces limited access, and the failure of one component during
checkout makes it necessary to pull out other functioning systems to replace the
malfunctioning part. For instance, in the MA-6 flight the short life carbon dioxide
absorber in the environmental control system had to be replaced since checkout
took longer than had been planned. This replacement required eight major
equipment removals and four revalidations of unrelated subsystems for a total
delay of 12 hours. All of these problems of course resulted from weight and space
constraints brought about by payload limitations.
For the Gemini and Apollo spacecraft, the equipment will be modular
and replaceable, allowing the substitution of alternate parts without tearing out
whole subsystems.
We depend quite a bit on the automatic systems for retrosequence but
man has proven that he can and does play an important role in the reentry
process. The only manned flight in which the automatic system for reentry was
used completely was at the end of Walter Schirra’s six orbits. In all other flights,
the astronaut took over and performed at least one part of the reentry manually
because of some malfunction which had occurred during the flight.
As we move into the Gemini and Apollo programs, a maneuvering
capability has been built into the spacecraft to allow changes in flight path both
while in orbit and during reentry into the atmosphere.
The translation engines provided will allow modifications to the orbit for
rendezvous with other vehicles in orbit. Also, by use of an offset center of gravity,
the spacecrafts will have and L/D capability not provided in the Mercury vehicle.
This will allow the onboard computers to select a particular landing point at any
time during the flight and after retrofire or atmospheric reentry the vehicle can
be maneuvered within a given footprint to reach this desired landing area. The
astronauts will provide the necessary back-up to these complex systems and can at
any time assume manual control of the system so that a proper and safe landing
can be assured.
[6] Our experience with the Mercury network changed our thinking
about the operation of this worldwide tracking system for manned flights. In the
initial design of the network, we did not have voice communication to all the
remote sites.
But we soon found that in order to establish our real time requirement
for evaluating unusual situations, we needed the voice link. When we started the
program, the determination of the orbital ephemeris was a process that could take
several orbits to establish. We could not tolerate such a condition in a manned
flight so we set up a worldwide network which would maintain contact with the
astronaut approximately 40 minutes out of every hour. But continuous voice
contact with the astronaut has proven unnecessary and in many cases undesirable.
While we retain the capability to contact an astronaut quickly, we have tried to
reduce the frequency of communications with the spacecraft.