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  Space shuttle display electronics unit (DEU) / mass memory unit (MMU) test devices

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Author Topic:   Space shuttle display electronics unit (DEU) / mass memory unit (MMU) test devices

Posts: 11
From: Auburn, NY 13021
Registered: Sep 2006

posted 05-26-2012 03:20 PM     Click Here to See the Profile for wizardofeyes   Click Here to Email wizardofeyes     Edit/Delete Message   Reply w/Quote
With the end of NASA's space shuttle program, a certain three letter computer company scrapped the test system they had used to test and program critical parts of the space shuttle flight control system, and 850 pounds of historic electronics followed me home. All the interconnect cables were there, and all the lead/wire seals on the front were intact. Only thing missing was a COTS digital panel meter than someone had snagged.

The DEU (Display Electronics Unit) was the glass screen that displayed many flight parameters to the shuttle pilots. They were smart (for the time) units that could display not only text (plain, reverse, and blinking) but simple graphics with lines and circles, and unload many display tasks from the shuttle's main computers.

When the shuttle computers were designed, memory was bulky, slow, power hungry, and very expensive. NASA specified 64 kilobytes of memory for each display, but the entire typical mission programming required over 700K, which could not be fit into memory all at once. The MMU (Mass Memory Unit) was a compact, remotely located digital tape drive that could hold 8 megabytes of programming code, and could feed different program segments to the flight control systems as the mission progressed.

This system allowed the DEU and MMU to be programmed and tested before installation on the orbiter.

Overall view of system used to test the flight instrumentation displays (Display Electronics Unit) and Mass Memory Unit of the space shuttle

9 track Wang data tape drive (8" reels, 68 pounds, mounted at eye level), Mag tape formatter, Main test system power controller, External KB power adjuster (3 phase 400 Hz, 5VAC), System monitor unit — custom wirewrapped control computer, over 600 SN7400 series TTL chips on two planes. No EPROMs I could find, so the entire functionality must have been hardwired.

System Monitor unit, MIA Display unit (?Memory or Module interface Adapter?), EM Micromemory (probably magnetic core, no specs given, about 80 pounds!), 2 x 5 volt, 75 amp DC power supplies for MMU and DU, one 28 volt 40 amp DEU supply, and one Lambda rack with +/- 12V and -5 V supplies at a few amps. Power supplies weighed nearly 400 pounds. Hour meter on bottom power distribution rack shows zero hours!

Side panel for connections to DEU, DU (Display unit?) and MMU as well as keyboard and printer under test AGE, and GSE, with multiple test points. Also had two big flexible hoses for forced air cooling connections to the units under test.

I had to dismantle this system to get it out of the driveway, but only cut 4 wires in the process. I could reconstitute this unit, but would use modern switching power supplies for half the weight and much higher efficiency. Regrettably, the scrap dealer didn't get any of the vintage 8" mag tapes that would have driven the system.

Anyone have a spare DEU in their collection? It would certainly be neat to power it up again.

Many thanks to Allen Kent and James G. Williams for the DEU/MMU information contained in their very comprehensive article on Computers in Spaceflight.

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