Question: In the original film, the Discovery's onboard computer states: "I am a HAL 9000 Computer, Production Number 3. I became operational at the HAL plant in Urbana, Illinois, on the 12th of January, 1992." So, "HAL" was a manufacturer identification prefix (standing for Heuristically-programmed ALgorithmic Computers), "9000" was its model number, and "No.3" was its production lineage. In this sequel, however, Dr. Chandra is chatting with one of HAL's earth-based twin computers which has a feminine voice and is called "SAL"; but how can they arbitrarily change its manufacturer identification prefix? Being produced by the HAL plant in Urbana, Illinois, and being identical to the computer aboard the Discovery, the twin's name should have a different production number, but it should still be called "HAL," should it not?
Question: One thing that always confused me is why was it necessary to jettison Discovery after it was used as a booster rocket? Why couldn't they just keep it attached to the Leonov as they made their escape?