Rad-hard company designs non-volatile memory for megarad environments

MANASSAS, Va.–Storage technology for future space missions to the deepest parts of the solar system will require not only enhanced non-volatile memory capacity for video and other data but improved radiation immunity that current technologies do not provide.

By John McHale

MANASSAS, Va.–Storage technology for future space missions to the deepest parts of the solar system will require not only enhanced non-volatile memory capacity for video and other data but improved radiation immunity that current technologies do not provide.

Engineers at BAE Systems in Manassas, Va., partnered with Ovonyx in Rochester Hills, Mich., to develop C-RAM–or chalcogenide random-access memory–for spacecraft. The C-RAM hard drive is for applications requiring large amounts of radiation-hardened, non-volatile memory.

Space systems designers needed to upgrade non-volatile memory in space applications, says Vic Scuderi, manager of satellite electronics at BAE Systems. The older standards such as FLASH and EEPROM do not have the performance capability nor necessary radiation immunity; EEPROM only has an immunity of 100,000 rads, he continues.

C-RAM provides 20 times the tolerance to total-dose radiation over current EEPROM designs and four to 16 times the density of competing non-volatile memory technologies, according to BAE Systems’ fact sheet.

C-RAM also only uses one 3.3-volt power supply for programming and operation where EEPROM needs two power supplies. For upcoming NASA missions toward Jupiter and its moon, Europa, the spacecraft will see radiation levels of 4 to 10 megarads, so a replacement was needed, Scuderi says. CRAM offers the necessary megarad immunity and performance capability needed for the solid-state recorders to efficiently record and download data from these missions, he adds.

C-RAM will be offered in two total-dose immune levels, 500-kilorad and 1-megarad. According to BAE Systems, it is also 1,000 times more single event upset (SEU) immune than EEPROM.

The Space Vehicles Directorate of Air Force Research Laboratory at Kirtland Air Force Base, N.M., and other agencies funded this effort, BAE Systems officials say.

BAE Systems’ C-RAM offers 70-nanosecond read-cycle times and 500-nanosecond write-cycle times (100 times faster than EEPROM), requires low operating and standby power, and is latchup-immune.

Ovonyx experts provided the C-RAM technology and BAE Systems performed the radiation-hardening of the devices.

The technology, called Ovonic Unified Memory (OUM), is similar to how read-write CD and DVD technology uses a laser to record data, Scuderi says. “In space it is not yet feasible to use a laser,” so another method is needed. Ovonyx writes to the drive with small transistors that electrically charge the phase-changing Chalcogenide material.

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