Jenny Winder
Space writer Astronauts usually hog the limelight, but Jenny checks out a book in which NASA’s ground control crew are the heroes.
Jack Clemons began work as part of the engineering team that supported NASA space missions in 1968, three days after the launch of Apollo 8, the first manned spacecraft to orbit the Moon. He was tasked with developing, writing and testing computer software to control the Command Modules’ re-entry through Earth’s atmosphere. At the time, this was done using a slide-rule, as the first hand-held calculator wasn’t available until 1972 and cost the best part of £2,000. Computer programs were handwritten in the computer language FORTRAN and typed onto cards in a punch card machine (one line of program per card).
Clemons’ memoir follows the ground teams through all the subsequent Apollo missions, including a detailed account of the Apollo 13 rescue, as well as the Skylab and Space Shuttle missions, up to the mid-1980s, and from the ridiculously primitive Display and Keyboard (DSKY) device on the Apollo Command Modules to the five flight computers aboard the Space Shuttle.
The team needed to anticipate every eventuality, calculating all the variables such as changes in geographic location and angle of re-entry. Even the time of year and the weather had to be taken into account, with alternative back-up plans in place.
The margins for error were tiny. In computer programming, the industry average is 10-12 errors for every 1,000 lines of code. Over the 30-year Space Shuttle programme, the error rate for computer code developed by IBM for the Onboard Flight Software went from 0.8 errors per 1,000 down to less than 1 error per 5,000 lines of code. That is closer to error free than any large complex software system before or since. The book has a very nice appendix covering frequently asked questions about Apollo and the Space Shuttle, which includes some interesting assessments of both the Space Shuttle Challenger and Space Shuttle Columbia disasters. This book is not just for computer geeks. If you have seen (and loved as much as I did) Ron Howard’s 1995 film Apollo 13, then you will love this insider’s tale of human space exploration from the point of view of the team back on planet Earth. Why should the astronauts get all the glory?
JENNY WINDER is a freelance science writer, astronomer and broadcaster