[AR] Re: Flight Computer

  • From: Paul Breed <paul@xxxxxxxxxx>
  • To: arocket@xxxxxxxxxxxxx
  • Date: Sat, 26 Dec 2015 10:55:06 -0800

The issue is likely to be sensors not CPU.
For small vehicles the moments of inertia are small and
sensor delays that would be unnoticeable on a Saturn 5 will make an 8 ft
rocket uncontrollable.






On Sat, Dec 26, 2015 at 9:16 AM, Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:

On Sat, 26 Dec 2015, snyder@xxxxxxxxxx wrote:

Fundamentally, I don't believe the processor capability of
modern equipment is much of an issue. Seems like the Titan III
GNC processor was running at something like 0.4 Mhz.


Moreover, clock speed isn't the whole story. The Saturn V guidance
computer (which flew not just orbit insertion, but also restart and boost
into lunar trajectory) had a 0.5MHz main clock, but it was bit-serial --
operating on data one bit at a time, not a word at a time. It needed 82us
to add two numbers (26-bit integers). It had hardware help with various
things that we'd now do in software, and its software was very carefully
written, but even so...

Computing power is just not an issue nowadays for such jobs, not if the
software is designed sensibly.

Henry


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