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Editorial: Thoughts of Spring and Processors
Kevin Krewell - Editor in Chief (11/22/2004)
excerpt from http://www.mdronline.com/mpr/

Microprocessor Count for SpaceShipOne

There is a theme to the rest of this editorial--microprocessors surround
us and can take us into space or to the shopping mall. After my last
editorial, I decided it would be interesting to check just how many
microprocessors are on SpaceShipOne. I received an email response from
Scaled Composite LLC employee Peter Siebold, whose title is SpaceShipOne
avionics and simulation project engineer and SpaceShipOne test pilot as
well. His response:

"Bottom line is it depends on where you draw the line. All our
communication radios are modern digital variants, which all have some
form of DSP or microprocessor (3). We have two GPS receivers on board,
which by themselves also have a microprocessor each (2). We have a motor
controller which helps the pilot out by turning the rocket off before
anything bad can happen (1). We have at least two microcontrollers
(PICs) which do various things, such as help turn off the motor after a
fixed amount of burn time and converting outside pressure readings for
our transponder (2). We also have two very accurate pressure transducers
which are digital and have an embedded microcontroller in each (2). Our
main avionics suite has a total of two Intel Pentium III 800MHz
microprocessors (2). We also have a backup air-data display, which I
presume has at least one microprocessor (1). So to add these all up, 13,
and I bet I missed one or two. We do, however, consider this simple."

The SpaceShipOne design reminds me of what Albert Einstein said:
"Everything should be made as simple as possible, but not simpler."

The 15 or so processors in SpaceShipOne add up to fewer than are in most
cars today, as there has been an explosion in microprocessors in
automobiles during the past decade. My 1996 Mazda Miata is almost all
manual: the transmission, convertible top, A/C, windows, doors, and
brakes (no antilock) are all manual. The number of processors in my
Miata likely includes one or two in the engine-management unit, one in
the aftermarket stereo, and one for the airbag system. That's probably
all of three to four.

On the other hand, last year I splurged on a new, rotary-engine-powered,
2004 Mazda RX-8. I've owned two Mazda RX-7s in the past ('82 and '86)
and I love the free-revving rotary engine. This car, unlike the Miata,
came with power everything, except I got the manual transmission. There
are very likely processors in the climate control, instrument panel
cluster, radio, antilock brakes, traction control, engine management,
tire-pressure monitor, power-window controller, interior light
management, and door locks. And that's for a sports car. A modern luxury
car can have more than 60 processors.

Think about it. You can reach the edge of space in a vehicle that has
about 15 microprocessors, but driving your car, on the ground, can
require the coordinated action of 50 or more!