ATHENA computer

The UNIVAC Athena computer was the processor for ground commands to the HGM-25A Titan I intercontinental ballistic missile (ICBM) as part of Western Electric's missile guidance system. The Athena was the "first transistorized digital computer to be produced in numbers" and computing Titan flight data to the necessary burn-out point to start a ballistic trajectory toward the target. Consisting of ten cabinets plus console on a 13.5 by 20 foot (4.1 by 6 m) floor pan. On-board Titan attitude control rolled the missile to maintain the missile antenna aligned to the ground antenna. Computer outputs were transmitted to the missile from a ground transmitter a "quarter mile out" (0.6 km).^[1] Completed in 1957, the Athena weighed 21,000 pounds (9500 kg).^[2]

The Athena used a Harvard architecture design with separate data and instruction memories^[3] by Seymour Cray at Sperry Rand Corporation and cost about $1,800,000.^[4] Used with the computer were the:

• AN/GSK-1 Computer Set Console (OA-2654)^[5]
• Friden, Inc. terminal with paper tape equipment^[2]
• "massive motor-generator set with 440 volt 3 phase AC input [that] weighed over 2 tons" at remote locations^[6]
• input from one of two large AN/GRW-5 Western Electric radars in silos each with "20 foot (6 m) tall antenna" raised prior to launch and locked to the raised Titan's "missileborne antenna".^[7][1]

The "battleshort" mode ("melt-before-fail") prevented fail-safe circuits such as fuses from deactivating the machine e.g., during a missile launch.^[8] The last Athena-controlled launch was a Thor-Agena missile launched in 1972 from Vandenberg Air Force Base in California, the last of over 400 missile flights using the Athena.^[9][10] The 26 Athena computers, when declared surplus by the Federal Government, went to various United States universities. The one at Carnegie was used as an undergraduate project until 1971, when the former electrical engineering undergraduate students (Athena Systems Development Group) orchestrated its donation to the Smithsonian Institution.

References

1. "Archived copy" (PDF). Archived from the original (PDF) on 2012-09-16. Retrieved 2013-08-22.
2. http://www.silogic.com/Athena/Athena.html
3. McMurran, Marshal William Achieving Accuracy A Legacy of Computes and Missiles, Bloomington, Indiana: Xlibris, 2008, ISBN 978-1-4363-8106-2, p. 141
4. "UNIVAC 24-bit computer genealogy".
5. http://www.silogic.com/Athena/1968%20Athena%20User%27s%20Manual%20%28grayscale%29.pdf
6. United States Air Force The T.O. 21M-HGM25A-1-1 Technical Manual Operation and Organizational Maintenance HGM-25A Missile Weapon System, United States Air Force, 1964, Figure 1-43
7. United States Air Force The T.O. 21M-HGM25A-1-1 Technical Manual Operation and Organizational Maintenance HGM-25A Missile Weapon System, United States Air Force, 1964, paragraph 1-159
8. DiVecchio, Mark. "Univac Athena Missile Guidance Computer".
9. Shufelt, Wayne. "Letter Concerning the Last Athena guided Missile Launch" (PDF).
10. "Information Technology Pioneers". Retrieved February 11, 2016.