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NASA and its IBM computers

August 05, 2022
by Mark Ollig

The Real-Time Computer Complex (RTCC) is located at the NASA Mission Control Center in Houston, TX.

In 1962, the RTCC housed several IBM large-scale data processing mainframe digital computers.

Think of the RTCC as the computing brain that processes mountains of data to guide nearly every portion of a NASA spaceflight mission. Flight controllers and engineers in the Mission Control Center depended on the RTCC.

On April 11, 1970, a portion of the Apollo 13 command service module exploded while it was halfway to the moon. Numerous voices from flight controllers in the Mission Control room desperately attempted to ascertain how serious the situation was while communicating with the astronauts aboard the Apollo 13 command module.

NASA Flight Director Gene Kranz directs his Mission Control team by clearly and firmly saying, “OK, listen up … Quiet down, people. Procedures, I need another computer up in the RTCC.”

The quick thinking and resourcefulness of NASA flight controllers and engineers, along with the courage and professionalism of the Apollo 13 astronauts, resulted in their safe return to earth.

Credit for their safe return should also be acknowledged to the five high-performance IBM System/360 Model 75 computers in the RTCC.

About 16 years earlier, the 1954 IBM 704 digital mainframe computer operated using a low-level assembly language and a high-speed magnetic core storage memory, replacing the electrostatic tube storage used in previous IBM computers.

In 1957, Sputnik 1, Earth’s first artificial satellite, was tracked during its orbit around the planet by two IBM 704 computers.

In 1959, the IBM 1401 mainframe computer was built using a high-level programming language with FORTRAN (Formula Translation/Translator) computer language coding system created by IBM programmer John Backus in 1957 and tested on the IBM 704.

Backus said FORTRAN took what had previously required 1,000 machine statement instructions to be written in only 47 statements, significantly increasing computer programmer productivity.

In 1961, NASA launched two crewed Mercury suborbital flights. IBM 7090 computers installed in NASA Ames Research Center assisted engineers and mission flight controllers by quickly performing thousands of calculations per second.

The 1965 NASA Gemini spacecraft’s 59-pound onboard digital guidance computer was manufactured by IBM. It used a 7.143-hertz processor clock and could execute more than 7,000 calculations per second.

In 1969, IBM’s computer reliability was credited with keeping Apollo 12 on its proper trajectory after a potentially catastrophic event.

On Nov. 14, 1969. About 37 seconds after the Apollo 12 Saturn V rocket left the launchpad from Cape Canaveral, two lightning bolts struck it, knocking out all of the command module’s onboard instrumentation systems and telemetry with Mission Control in Houston.

“What the hell was that?” shouted Apollo 12 command module pilot Richard Gordon after lightning struck the Saturn V rocket traveling at 6,000 mph.

Fortunately, two-way radio communications were still functioning between Mission Control and the command module spacecraft.

“I just lost the whole platform,” Apollo 12 mission commander Charles Conrad Jr. radioed Mission Control. “We had everything in the world drop out,” he added.

The static discharge from the lightning caused a voltage outage, knocking out most of the Apollo 12 command module control systems, including the disconnection of its vital telemetry communications link with Mission Control.

Loud, overlapping voices could be heard in Mission Control as engineers and flight controllers worked on what course of action to take.

Fortunately, the Apollo 12 Saturn V rocket did not deviate from its planned trajectory. Instead, the IBM 60-pound Launch Vehicle Digital Computer (LVDC) housed inside the Instrument Unit section of the rocket’s third stage contained the required processing power to continue the Saturn V’s programmed course.

Meanwhile, Mission Control engineers saw strange data pattern readings on their control screens and desperately worked to find a solution.

NASA Mission flight controller and engineer John Aron recalled similar data patterns during simulation tests. He remembered it meant the Signal Conditioning Electronics were down.

“Flight, try SCE to AUX,” Aaron recommended to Mission Flight Director Gerry Griffin.

Griffin instructed the recommendation to be radioed to the astronauts in the command module.

One minute after the lightning strike, Mission Control radioed the astronauts in the Apollo 12 command module with the following:

“Apollo 12, Houston. Try SCE to Auxiliary. Over.”

There was a brief pause as the astronauts heard what they thought was the acronym “FCE” instead of “SCE.”

“Try FCE to Auxiliary. What the hell is that?” Conrad questioned Mission Control.

“SCE – SCE to Auxiliary,” Mission Control slowly repeated with emphasis.

Apollo 12 pilot astronaut Alan Bean was familiar with the SCE switch inside the command module. So, turning around in his seat, he flipped SCE to AUX, which restored and normalized the command module instrumentation data and telemetry transmissions.

Apollo 12 was able to complete its mission to the moon, thanks in significant part to the reliability of the IBM LVDC and, of course, Aaron’s “SCE to AUX.”

In 1962, science fiction writer Arthur C. Clarke witnessed a demonstration in Bell Labs where its scientists used the IBM 7094 computer to create a synthesized human voice singing the song “Daisy Bell (Bicycle Built for Two).”

This demonstration by the IBM computer inspired Clarke to write a much-remembered scene in the 1968 science fiction movie “2001: A Space Odyssey” featuring the somewhat sentient “Heuristically programmed ALgorithmic” computer known as the HAL 9000.

In the movie, the HAL 9000 computer is singing “Daisy Bell (Bicycle Built for Two)” while deactivating to inoperability as astronaut David Bowman removes its computing modules.

For the record, the HAL 9000 was not an IBM computer.


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