Note that prior to 1968 and the metric conversion, the NAR Total Impulse chart was a bit different.

It didn't nicely double over the whole range.

1/4A 0 - .175 lb-sec
1/2A .176 - .350 lb-sec
A .351 - .700 lb-sec
B .701 - 1.200 lb-sec Whoops!
C 1.201 - 2.00 lb-sec Whoops! again!
D 2.01 - 4.00 lb -sec ah, back to doubling
E 4.01 - 8.00 lb-sec
F 8.01 - 16.00 lb-sec

__________________
Roy
nar12605