Editing Model rocket (section)

===First letter===

The letter at the beginning of the code indicates the motor's total [[impulse (physics)|impulse]] range (commonly measured in [[newton (unit)|newton]]-seconds). Each letter in successive alphabetical order has up to twice the impulse of the letter preceding it. This does not mean that a given "C" motor has twice the total impulse of a given "B" motor, only that C motors are in the 5.01-10.0 N-s range while "B" motors are in the 2.51-5.0 N-s range. The designations "¼A" and "½A" are also used. For a more complete discussion of the letter codes, see [[Model rocket motor classification]].

For instance, a B6-4 motor from Estes-Cox Corporation has a total impulse rating of 5.0 N-s. A C6-3 motor from Quest Aerospace has a total impulse of 8.5 N-s.<ref>National Association of Rocketry web site: {{cite web |url=http://nar.org/SandT/NARenglist.shtml |title=National Association of Rocketry &#124; NAR Certified Motors |access-date=2006-07-29 |url-status=dead |archive-url=https://web.archive.org/web/20060813110342/http://nar.org/SandT/NARenglist.shtml |archive-date=2006-08-13 }}</ref>