[SIGCIS-Members] whirlwind, radar and real-time tracking

Mark Priestley m.priestley at gmail.com
Fri Apr 23 23:56:46 PDT 2021

Hi Guy,

I'm loving your work on these early Whirlwind programs! I've only dipped a
toe into the early WW archives, but here's a couple of comments that are
probably more like questions to the list ...

Surely WW inherited its real-time control ambitions from the original aim
to built an analogue flight simulator? So when they switched to a digital
approach, they inherited an RTC problematic that was quite distinct from
the more purely computational ambitions of the other late-40s computer
projects. I'm struck in reading the project reports, for example, that
analogue-to-digital conversion, for example, is a big topic that doesn't
appear anywhere else. And I think the flight simulator plan wasn't given up
until 1947 or 1948?

Also possibly of interest is the air traffic control project that they
started in 1949 (intriguingly led for a while by Gordon Welchman, of
Bletchley Park fame). Perhaps this was in part motivated by the obvious
crossover to defence applications. I haven't followed it far enough to see
what happened, but they started out investigating how to convert radar data
to plane coordinates, and something called "maintaining private line
communication" with aircraft. All of which sounds like grist to the
interception program's mill.

So while I've nothing really to add to the great comments of the other
respondants, I wonder if digging deeper into the background both of WW and
MIT might "demystify" to some extent the novelty of applying a digital
machine to real-time control.


On Fri, 23 Apr 2021 at 21:41, Guy Fedorkow <guy.fedorkow at gmail.com> wrote:

> Greetings Colleagues,
>    I've been working on restoring a 1951 Whirlwind program, written at
> MIT, used to demonstrate real-time tracking of aircraft with radar for
> the purposes of guiding an interception (the Cold War was in full flight
> in the 1950's).  This work ultimately led to the massive SAGE air
> defense network in the US.
>    You can see some rather informal preliminary notes on the work at
> https://www.historia-mollimercium.com/whirlwind/WW-Track-while-Scan-Draft-Notes-v1.pdf
>    The program does work in simulation; you can see a four-minute video
> of the simulator running an intercept at
> https://www.historia-mollimercium.com/whirlwind/Track-while-scan-Apr-23-2021.mp4
>    Spoiler alerts: The original really did display moving dots on a CRT,
> but the graphics are "spartan" to say the least.  And nothing in
> particular happens when the intercept actually happens.
>    Would anyone know of contemporaneous work involving digital computers
> for either radar tracking or real-time computing around 1951?  I think
> all the familiar digital computers from those years were used in
> applications where batch operation was perfectly acceptable, e.g.,
> computing ballistics tables.
>    Innovations like this rarely occur in a complete vacuum, but I don't
> see references to any similar digital computing projects.
>    If anyone has pointers, do let me know!
> Thanks
> Guy Fedorkow
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