Launch Vehicle Digital Computer

The Apollo Launch Vehicle Digital Computer (LVDC) was one of the major components of the Instrument Unit fitted to the S-IVb stage of the Saturn V and Saturn 1B rockets. Its primary role was to provide an autopilot for the Saturn from launch to orbit insertion, but it also supported pre- and post-launch checkout of the Saturn hardware.

By today's standards it was extremely slow, with an add operation taking 82 microseconds (vs a fraction of a nanosecond on a Pentium-4) and a memory holding only 4095 28-bit words, equivalent to less than sixteen kilobytes. However, in the 1960s it was a sophisticated system, and easily capable of flying a two-thousand ton rocket into a hundred mile high orbit.

Unfortunately, unlike the Apollo Guidance Computer, the software which ran on the LVDC seems to have vanished. While the hardware would be fairly simple to emulate, the only remaining copies of the software are probably in the core memory of the Instrument Unit LVDCs of the remaining Saturn V rockets on display at NASA sites.

References

• IBM, Saturn V Launch Vehicle Digital Computer, Volume One: General Description and Theory, 30th November 1964
• Boeing, Saturn V Launch Vehicle Guidance Equations, SA-504, 15th July 1967