A.2.2.6 Central Processing Unit *
A.2.2.7 Central Processing Unit Selection
A central processing unit (CPU) is a description of a class of logic machines that can execute computer programs. The CPU is one of the most crucial components of any electrical system and, because of its importance, typical launch vehicle CPUs are extremely expensive. For our application, the CPU will function as our primary flight computer.
The RAD6000 radiation-hardened single board computer was manufactured by IBM for BAE Systems and has been used onboard numerous NASA spacecraft. In addition to 77 satellites (as of 2003), the processor is/was used in the Spirit and Opportunity Mars rovers, the Mars Pathfinder lander, the Deep Space 1 probe, and the Genesis and Stardust sample return missions. The computer has a maximum clock rate of 33MHz and a processing speed of about 35 MIPS. In addition to the CPU itself, the RAD6000 has 128MB of ECC RAM. A typical RTOS running on NASA's RAD6000 installations is VxWorks and the flight boards in this system have switchable clock rates of 2.5, 5, 10, or 20 MHz. The unit cost for a RAD6000 Central Processing Unit is approximately $250,000. Because of the high cost of this system, other options were considered.
Commercial CPUs are not radiation-hardened and do not undergo the extensive testing procedures that the space-rated CPUs do. These CPUs are mass produced with a variety of possible specifications and have a very large price range. Based upon the current cost of a commercial computer, we are able to estimate this cost to be approximately $1,000. We budgeted $10,000 for this system to account for redundant hardware, an extended software development cycle, and radiation hardening. We think this system will be sufficient for use in our launch vehicle due to the relatively low altitude of our flight and the minimal processing power required.
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Author: Nicole Bryan