|Re: HP 41 used on Shuttle at Air & Space Museum|
Message #7 Posted by Erik Wahlin on 9 May 2000, 11:30 a.m.,
in response to message #1 by Steve
Two of the HP-key note issues (Jan-April 1981 Vol. 5, No. 1 and March - May 1982 Vol. 6 No. 2) describe the HP-41C's that were used aboard the Columbia. There are also a few pictures showing them in use. One article described that the HP-41C was used to calculate deorbit-burn information, should data coming from mission control be interrupted or during an emergency. Two other programs helped balance Columbia prior to re-entry and another to pin-point Earth observation sites. The 41C's did not take place of the larger on board computers, but complemented them with personal computer convenience. The time module was also mentioned, as well as the HPIL peripherals. The other article described how the 41's were tested at white sands New Mexico (for shock, vibration and outgassing). As a result of the tests, certain modifications (which were not described) were made to certify them for flight. Special flight pouches with extra memory modules (each 41C had four mem. modules), extra batteries, a card reader and cards were used. For the first shuttle flight, one HP41C was dedicated to the center of gravity program (balance) and the other to acquisition of signal."The center of gravity program was used before reentry into the earth's atmosphere to compute the shuttle's present center of gravity and the amount of fuel to be burned in each tank to reach the required center of gravity for reentry. This center of gravity program was termed "flight critical" by NASA and necessitated extensive pre-launch testing of the calculators".
"The other program, the Acquisition of signal program, ran continually in the second calculator, starting at launch, so it could display at any time the next ground station that columbia could contact, when it would be in contact, the duration of that contact, and which frequency (UHF or S-band) could be used. And thanks to the continuous memory, the calculator did not have to be on during the whole flight". The article also mentioned that HP might make custom ROM modules for NASA to eliminate the need for memory modules