Skylab was the fourth manned space program of the National
Aeronautics and Space
Administration to be supported by computers, programs
and people of the International Business
Machines Corporation during the 20th century.
Computer processing of such data as orbital trajectory
and spacecraft monitoring that previously served the Mercury,
Gemini and Apollo programs were critical to the success
of the Skylab experiments. In addition, both onboard and
ground computers helped in the scheduling and execution
of Skylab activities.
Special Skylab electronic equipment and programs were
produced by IBM in Owego, N.Y. and Huntsville, Ala. Standard
IBM installations at the Goddard Space Flight Center,
Greenbelt, Md., and the Lyndon
B. Johnson Space Center in Houston helped to monitor
the Skylab missions with programs developed by IBM. An
IBM team was responsible for launch support activities
at the John F. Kennedy Space Center in Florida.
Instrument Units
Each launch vehicle used during the Skylab mission employed
an IBM-built instrument unit to provide guidance and
control functions from launch until earth orbit was
achieved.
The instrument unit atop
the Saturn V guided the Skylab itself into orbit, and
arranged the Skylab's equipment for use by the astronauts
when they arrived onboard. The instrument unit also controlled
the jettisoning of the protective payload shroud and activated
the onboard life support systems, started the solar inertial
attitude maneuver, deployed the Apollo Telescope mount
at a 90-degree angle and deployed Skylab's solar wings.
In addition, this instrument unit turned on the onboard
computers and gave them control of the space station.
Onboard Computers
Two IBM computers in the Skylab controlled the orientation
of the laboratory throughout the mission. The lab's
solar panels, from which electrical power was obtained,
had to face the sun directly to achieve maximum efficiency.
The onboard computers, which were arranged redundantly
for added reliability, were models of IBM's System/4Pi,
a computer series designed for the special weight and
environmental requirements of aerospace applications.
They were built at IBM's facility in Owego and fitted
and programmed for the mission in Huntsville.
Each of the IBM computers aboard Skylab weighed 100 pounds
and measured 19 by 7.3 by 31.8 inches. They were capable
of handling more than 100 signals to Skylab attitude control
equipment.
Two other electronic units associated with these computers
were built by IBM in Huntsville: the workshop computer
interface linked the computers with each other and with
sensors and control devices; and a memory load unit was
able to refresh computer programs in the event of electrical
interference disrupting the computers' memories.
Goddard Space Center
IBM's Federal Systems Division developed the Goddard
Real-Time System for the Apollo missions. As on Apollo,
it was employed on two IBM
System/360 Model 75s during the Skylab mission. These computers processed
data from radar stations, remote sites and tracking
ships which made up NASA's Manned Space Flight Network.
IBM personnel at Goddard were responsible for operating
and maintaining tracking displays and recording equipment,
as they did during the Gemini and Apollo programs.
Lyndon B. Johnson Space Center
At the Johnson Space Center the data facility for ground
controllers was called the Real-Time
Computer Complex (RTCC).
These computers processed the tracking and
onboard monitoring data streaming into Houston for the
control consoles of NASA engineers.
They also accumulated and processed data from Skylab's
experiments.
The RTCC, consisting of five Svstem/360
Model 75s,
was operated and maintained by IBM.
During the Skylab mission, four of the computers had specific
functions to carry out, and the fifth machine backed up
the other four.
Among the responsibilities of the Model 75s were mission
operation computer programs, the Skylab Terminal System,
simulation programs and the earth resources interactive
processing system.
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