Lunar Lander Images

Lunar Lander Simulator

This was our most ambitious project. It started off as nothing but a squarish vehicle that dropped from the top of the screen to the bottom, much like the commercial Lunar Lander in the arcades of the time. You turned the engine on or off and tried not to hit too hard.

Eventually, we had the capability to descend from orbit, flying over a pseudo-randomly generated terrain. You controlled your horizontal velocity (which started at about 5500 fps when running in the “deorbit” mode) and vertical velocity by throttle and pitch. You controlled pitch by commanding a pitch rate or, if you were incredibly foolhardy brave, by turning on and off jets. An onboard guidance system could fly the entire profile for you, selecting a candidate landing site and taking you to it. Of course, that option was for wusses.

Along the way, you had to deal with numerous failures (how numerous and how bad depended on the skill level). You could have pitch jets fail (on or off), navigation biases or dispersions, fuel tank leaks or failures, computers failing, even a main engine failure. Fortunately, we had an abort mode that separated the top stage of the LM and took you out (assuming you were within the allowable pitch and pitch range).

The grid of lights are called DDDs (Digital Display Drivers), which are commonly used at NASA. The engine characteristics and mass properties of the LM are accurate.

We also had much simpler modes for beginners, which basically involved just throttling the engine up and down as you descended to the landing site.

These images are from the final version of the program. These are actual screen shots; I rewrote the entire program into C++ for the PC. Visually and functionally, however, it is virtually identical to the HP (even down to the monochrome green graphics).

NOTE: One earlier version had a different abort sequence: the pilot ejected from the LM, his/her chute opened–only to collapse, since there’s no air on the moon–and then he/she flapped his/her arms wildly until landing safely on the surface. At that point, the pilot would throw his/her arms up and grin wildly. I say “he/she” because the pilot could be of either gender. Don’t ask about THOSE graphics…. (Sadly, that version is lost to antiquity.)

Leave a Reply