alt.hn

3/20/2026 at 12:14:59 PM

Show HN: FPGA soft-core of the Saab Viggen's 1963 airborne computer

 https://github.com/FormerLab/ck37-core

by FormerLabFred

3/20/2026 at 11:02:00 PM

Some background reading:

https://www.saab.com/newsroom/stories/2017/december/datasaab...

PDF:

http://www.datasaab.se/Papers/Articles/Viggenck37.pdf

Now we got it on a %50-100 FPGA board.

Half the size of a credit card. I guess the original computer onboard was 12-15 kgs

by FormerLabFred

3/20/2026 at 11:40:17 PM

Late in Sweden, back tomorrow (CET)

by FormerLabFred

3/21/2026 at 2:06:33 AM

What a great project. I wonder how the modern sensors stack up against the military version in times of jitter and drift, that might cause some surprises. Larger sensors have a lot of inertial filtering compared to smaller ones.

I also think that the MTBF target the original had will be vastly exceeded by this replica due to the reduction in component count, but it will probably be more susceptible to bitflips. But you won't be flying that high if you put this on a drone. Please post future updates.

by jacquesm

3/21/2026 at 9:27:13 AM

Great points!

This is experimental,

We need to address MEMS vs mechanical gyro noise profile

Gain constants in the nav kernel were tuned empirically for the original sensor suite.

Then we got SEU yes :)

noted, though flying at 30m AGL as the Viggen did in low-level attack mode keeps the cosmic ray exposure manageable

Will write a handover doc for Saab, they can do the rest of the dev :)

Yes will post updates

(we run two other drone projects, uas-phone-swarm for iOS and Android

There is a public blog post on it. Patreon/Formerlab

Modern smartphones more powerful than the ck37 tech)

by FormerLabFred

3/21/2026 at 9:40:06 AM

Flying smarthphones project introduced here:

https://www.patreon.com/posts/152446275

Public access

by FormerLabFred

3/21/2026 at 11:56:25 AM

You are doing something really interesting here in terms of discovering scaling of such algorithms with respect to vehicle size and sensor response, I'm super interested in what else you will discover. I'm also not aware of anybody doing something similar in the past.

by jacquesm

3/21/2026 at 3:56:26 PM

We had to rewrite the main system so those who are not into code and tech much could run it more easily. They are used to MarineTraffic and VesselFinder web sites.

This is tailor made for them, check loitering, export CSV.

Main system is no secret, but it got loads of ML and frontend is a bit messy. But one day we will ship it too.

If you check the link to GUR War and Sanctions web site in the README, they got a map where they plot harbors and similar. The main Shadow Fleet Tracker does next port prediction and handles flag change. We’ll sort mire user-friendly frontend and onboarding for the main version in future. Then people can use it as they need.

Thanks for all the feedback folks! Will try to reply a few times a day here. And post some more blog articles.

by FormerLabFred