SR-71 Drafting Base-sheet
Our last newsletter was wrapped around the idea “Underwater Internet of Things,” proposing a framework that considers the bio-acoustic impacts of marine communication systems that, due to the biophysics of ocean habitats, could really destroy the habitability of the ocean for most critters that live in it. Or not.
All technical communication systems hinge on disambiguation, so a common strategy is to build a data architecture that provides as much information as required at any level in the architecture to effectively execute subordinate or structural tasks.
This sort of data structure requires information being instantaneously available at any level – synchronized to all other levels, implying one or more data channels being continuously active.
This poses a few adjunct problems, particularly when the data being transmitted is in sensory bands perceivable by the critters that dwell the same habitat.
But there is more surreptitious angle on this; that data being continuously exchanged is not secure – and is thus is subject to surveillance and interruption. I was introduced to this concept as a kid when my father was working on the SR-71 spy plane at Lockheed’s acclaimed “Skunkworks.”
A spy plane needs to be “invisible,” so both the data inputs and outputs need to be as quiet as possible. My dad designed the stellar-inertial navigation system for the “Blackbird.” Using celestial siting, and defining x, y, and z inertial axis’ from a gyroscope, the plane was able to silently navigate over the Soviet Union during the Cold War without depending on the western LORAN (Long Range Navigation) system to know where it was.
And it also needed to be accurate. At Mach 3+ (three times the speed of sound), if it was one degree off course, in two minutes it would be a mile off course. So the navigation system was self contained and didn’t need to reconcile with any external inputs (except the silent stars).
The communication system was equally surreptitious, and in 1964, one of the first uses of “Spread Spectrum” frequency-hopping communication.
Conceived of by Hollywood glamor actress Hedy Lamarr, and composer George Antheil. The idea was to have radio transmission frequencies jump around like a player piano jumps around notes assigned by a piano roll. If you synchronize the transmitters and receivers to the same frequency-hopping sequence, they only look for the information they need at exactly the time they need it.
In this manner they were able to communicate clearly at 40dB below the ambient radio-frequency noise floor. The only signal above the noise floor was one 5 Watt blip that established sync. Once locked they could carry on communication at distances of up to 600 miles over the horizon using only 5 milliWatts of broadcast power. Very quiet.
(Unfortunately for Hedy and George, by the time the US Military started using their technology, the patent had run its course.)
If this approach was employed in the Underwater Internet of Things – establishing communication channels predicated on unique frequency-shift sequences specific to the particular communication channels, it might go far in allaying our concerns about turning the entire ocean into a digital-communications mosh pit.
Of course we know this technology today as what our cellphones use on our telecommunication super-highways – hosting millions of discrete, concurrent communication channels without any car crashes. And all relatively quiet.
