Monday, June 18, 2007

---ISS Fixed 

Spaceflight Now | STS-117 Shuttle Report | Station computers brought to life after impromptu repair
Spaceflight Now | STS-117 Shuttle Report | Two more space station computers revived
Cosmic Log : Obsolete chips in space
ESA Microelectronics page
tsc691e.pdf (application/pdf Object)
In another .22LR-in-the-fusebox save, Russians on the ISS bypassed faulty surge-suppression switches on the power supplies of the malfunctioning flight control computers, and got them to reboot and run. Further testing showed that the critical control functions were performing properly. The switches may have been affected by power changes when the new U.S. solar arrays were connected. Of course, the surge-protection capacity of some pieces of wire is pretty much negligible.
Alan Boyle's weblog at MSNBC has some interesting details about the command-and-control computers used by the Russians. They are a radiation-hardened Sparc v7 design, circa 1987. From the ESA documentation, they couldn't even put the CPU on a single chip at the point of deployment (they managed it later), but the computing “core” is on three separate chips. They do have tri-state outputs. Problems I can find include floating point errors, a tendency for bits loaded into the registers to cause adjacent bits to flip values, and lockups in the fault-handling registers. It might be interesting to compare them to computers in use in “fly-by-wire” aircraft systems.
Memories....my flight hardware experience included an EVA systems battery charger which used an Intel automotive ABS processor to “reprogram” the output from the 6502 (predating the 6510's in the Commodore 64's in the bottom of my closet) installed in an early-'80's-vintage commercial charger, and a respiratory mass spectrometer which was “controlled” by an “analog computer”---essentially a pile of often-mutually-contradictory op-amps which were essentially impossible to calibrate all at the same time. An astonishing percentage of “spaceflight hardware” is dirty, poorly maintained, mismanaged, obsolete junk.


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