pardo@june.cs.washington.edu (David Keppel) (01/08/89)
[From: comp.arch,comp.misc,comp.lang.misc,comp.protocols.misc] In article <2702@rti.UUCP> bcw@rti.UUCP (Bruce Wright) writes: >[Classic Fortran "do 100 i=1,10" vs. "do 100 i=1.10"] >[...] until the satelite got dumped in the ocean and NASA had lots >of egg on its face. That's an URBAN LEGEND!!! Fortran may deserve bashing, but the rumor that it crashed a satellite launcher is false (and should be put to rest). The real story is as follows: a formula was written with a logical "complement". Somewhere between the original formula and its implementation in ASSEMBLY language, the complement was dropped. This was discussed at length a while back on comp.risks and several other newsgroups. Followups to comp.software-eng. ;-D on ( I take risks, I read USENET! ) Pardo -----------> Excerpt from comp.risks (RISKS Digest 5.73): <------------ Date: Sun, 13 Dec 87 05:30:10 PST >From: hoptoad.UUCP!gnu@cgl.ucsf.edu (John Gilmore) To: RISKS@KL.SRI.COM Subject: Finally, a primary source on Mariner 1 My friend Ted Flinn at NASA (flinn@toad.com) dug up this reference to the Mariner 1 disaster, in a NASA publication SP-480, "Far Travelers -- The Exploring Machines", by Oran W. Nicks, NASA, 1985. "For sale by the Superintendent of Documents, US Government Printing Office, Wash DC." Nicks was Director of Lunar and Planetary Programs for NASA at the time. The first chapter, entitled "For Want of a Hyphen", explains: "We had witnessed the first launch from Cape Canaveral of a spacecraft that was directed toward another planet. The target was Venus, and the spacecraft blown up by a range safety officer was Mariner 1, fated to ride aboard an Atlas/Agena that wobbled astray, potentially endangering shipping lanes and human lives." ..."A short time later there was a briefing for reporters; all that could be said -- all that was definitely known -- was that the launch vehicle had strayed from its course for an unknown reason and had been blown up by a range safety officer doing his prescribed duty." "Engineers who analyzed the telemetry records soon discovered that two separate faults had interacted fatally to do in our friend that disheartening night. The guidance antenna on the Atlas performed poorly, below specifications. When the signal received by the rocket became weak and noisy, the rocket lost its lock on the ground guidance signal that supplied steering commands. The possibility had been foreseen; in the event that radio guidance was lost the internal guidance computer was supposed to reject the spurious signals from the faulty antenna and proceed on its stored program, which would probably have resulted in a successful launch. However, at this point a second fault took effect. Somehow a hyphen had been dropped from the guidance program loaded aboard the computer, allowing the flawed signals to command the rocket to veer left and nose down. The hyphen had been missing on previous successful flights of the Atlas, but that portion of the equation had not been needed since there was no radio guidance failure. Suffice it to say, the first U.S. attempt at interplanetary flight failed for want of a hyphen." ------------------------------------------------------------ >From: mink%cfa@harvard.harvard.edu (Doug Mink) To: risks@csl.sri.com Subject: Mariner 1 from NASA reports JPL's Mariner Venus Final Project Report (NASA SP-59, 1965) gives a chronology of the final minutes of Mariner 1 on page 87: 4:21.23 Liftoff 4:25 Unscheduled yaw-lift maneuver "...steering commands were being supplied, but faulty application of the guidance equations was taking the vehicle far off course." 4:26:16 Vehicle destroyed by range safety officer 6 seconds before separation of Atlas and Agena would have made this impossible. In this report, there is no detail of exactly what went wrong, but "faulty application of the guidance equations" definitely points to computer error. "Astronautical and Aeronautical Events of 1962," is a report of NASA to the House Committee on Science and Astronautics made on June 12, 1963. It contains a chronological list of all events related to NASA's areas of interest. On page 131, in the entry for July 27, 1962, it states: NASA-JPL-USAF Mariner R-1 Post-Flight Review Board determined that the omission of a hyphen in coded computer instructions transmitted incorrect guidance signals to Mariner spacecraft boosted by two-stage Atlas-Agena from Cape Canaveral on July 21. Omission of hyphen in data editing caused computer to swing automatically into a series of unnecessary course correction signals which threw spacecraft off course so that it had to be destroyed. So it was a hyphen, after all. The review board report was followed by a Congressional hearing on July 31, 1962 (ibid., p.133): In testimony befre House Science and Astronautics Committee, Richard B. Morrison, NASA's Launch Vehicles Director, testified that an error in computer equations for Venus probe launch of Mariner R-1 space- craft on July 21 led to its destruction when it veered off course. Note that an internal review was called AND reached a conclusion SIX DAYS after the mission was terminated. I haven't had time to look up Morrison's testimony in the Congressional Record, but I would expect more detail there. The speed with which an interagency group could be put together to solve the problem so a second launch could be made before the 45-day window expired and the lack of speed with which more recent problems (not just the Challenger, but the Titan, Atlas, and Ariane problems of 1986 says something about 1) how risks were accepted in the 60's, 2) growth in complexity of space-bound hardware and software, and/or 3) growth of the bureaucracy, each member of which is trying to avoid taking the blame. It may be that the person who made the keypunch error (the hyphen for minus theory sounds reasonable) was fired, but the summary reports I found indicated that the spacecraft loss was accepted as part of the cost of space exploration. Doug Mink, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA Internet: mink@cfa.harvard.edu UUCP: {ihnp4|seismo}!harvard!cfa!mink ---------> End excerpt from comp.risks (RISKS Digest 5.73): <---------- -- pardo@cs.washington.edu {rutgers,cornell,ucsd,ubc-cs,tektronix}!uw-beaver!june!pardo