What are good cross-setting and cross-system technology design and technology rating rules?
I think the original Fire Fusion & Steel for Traveller: The New Era is pretty good, but it probably overrates reinforced concrete, and it gets too complicated when designing entire vehicles as well as all their systems, power supply, any weapons, etc.
I picked up the revised Fire Fusion & Steel for Traveller 4, via DriveThroughRpg, but it drops the explanations, complicates the math, and drops the cybernetics, alternative ftl options, and so forth which made it usable across settings and systems.
There were also pretty good vehicle design rules for Space: 1889, and they work well with 19th-century technology plus isolated inventions [gasoline engine! deep-diving submarine! power of the sun!], but they fall short with 20th-century vehicles.
I looked at the free intro for the CORPS GGG [but not the corresponding VDS].
I’m not working on a space-opera setting right now, but I’d like a second check on contemporary armor penetration figures, for a Panzerblitz variant, and a first check on Roman-age torsion-artillery range figures. Unfortunately, FFS doesn’t cover mechanical artillery, GGG might not cover it, and GGG requires knowledge of the amount of propellant in each round for chemically-propelled artillery… data which is usually absent from publically-available manuals.