As an aviation enthusiast and retro computing enthusiast who had never heard of the Sprint missile system, your comments sent me on a bit of a research rabbit hole. I wanted to learn more about such an amazing missile intercept system and try to answer the question that immediately came up in my mind: could it be that a missile system designed in the 1960s could perform the same or more computationally intensive tasks than a modern Nvidia Jetson SOC?
The TL;DR is this: the Sprint missile system did nowhere near as complex of calculations as the Nvidia Jetson simulating fluid dynamics. The more complex version involves electro-mechanical systems, analog computing, and the differences between historical flight control systems and modern fly-by-wire systems.
I found
this PDF on the subsystems of the Sprint Missile system. Essentially, it details how there are 3 systems that work together to control an intercept using a Sprint Missile: ground-based radars, ground-based computers, and the Missile-Born Guidance Equipment (MBGE). The MBGE and the Autopilot subsystems are the only systems on the missile itself that do any sort of computation at all.
The Autopilot is an electro-mechanical system, not digital. If you've ever seen any of the older Air Data Computers that utilize advanced analog and mechanical systems to "compute" air speed and other telemetry from old jets then you'll have the right idea. Think gyros and mechanical springs, not digital circuits. So this leaves us with the MBGE to do any sort of digital computation at all. What did the MBGE do, exactly? From the PDF:
- To receive and decode missile command steering orders
- To receive and decode discrete commands for payload activation, destruct signals, or other purposes
- To receive and decode an autopilot gain control signal which is a function of computed dynamic pressure
- To transpond a beacon signal for ground station radar tracking purposes
The only part of this that was digital, at all, was the decoder: "The decoder employs transistorized digital techniques for message decoding, storage, and signal conditioning."
So, to be clear, all of the computation for intercept was done on the ground and sent to the Sprint via radio. The engineering behind the Sprint was very impressive! You mentioned one of the more interesting challenges here:
However, even that was done with an analog circuit that amplified and chose the strongest signal. There was no "complex computing algorithm" involved. They did this with good old fashioned electronics ingenuity. The only digital computation performed on the Sprint at all was decoding, storing, and conditioning those intercept signals. We are comparing a digital signal decode filter circuit to an entire computer performing a fluid dynamics simulation in real time. The Nvidia Jetson is multiple orders of magnitude more capable and complex than what was on the Sprint missile.
So what's the takeaway from all this? For one, modern military hardware with fly-by-wire systems require vastly more computing power for their flight control systems to perform essentially the same job as legacy electro-mechanical analog systems. The upside is that modern systems can push performance envelopes much further by having that real-time simulated fluid dynamics data.
Anyway, I truly find this subject fascinating and am not trying to prove anyone wrong. Comparing the Sprint Missile to a modern hypersonic missile system is just comparing apples and oranges.
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