HP42s в космической программе Space Shuttle

На глаза попалась интересная статья инженера NASA про использование калькулятора HP42s в космической программе Space Shuttle, в конце 80х годов.

I used the 42s while designing a new shuttle ascent abort guidance algorithm. In those days, getting time on the mainframe simulation was slow. We had to be very sure of the changes made to the simulation. Then we could run it in batch mode, then analyze the results. I could only get time every few days, so it was not a good tool for iterative design work. What I needed was a tool to validate the equations of motion before going to the mainframe. This is where the HP-42S comes in. I found it a lot easier to do all the prototype work on the 42S. Only after I verified the equations of motion, did I code it into the main simulation.

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After integrating, I developed a simulation on the HP-42S containing these equations. I programmed it to print out the altitude over time on the thermal printer. With the 42S I was able to rapidly validate the equations and prove the overall algorithm. I could also assess the effect of different burn attitudes to find the optimal thrust vector to maximize forward velocity while staying above the droop altitude limit.

I used the thermal printer to create graphs of the shuttle altitude profile under different initial conditions. I’d end up with graphs about 6 inches long showing the altitude going up, then drooping down, then up again. It was a beautiful thing to see the first time it worked and this perfect altitude profile printed out.