"Shapes"
The problem is that the nomenclature is a bit loosely used. Strictly speaking, a "shape" would be just that, a weapon casing filled with inert material so that it was of similar mass and C of G to the real thing and would thus have the same ballistic and aerodynamic characteristics. It's fine if all you want to do is load and unload it, carry it and (possibly) release it.
If you want to do a bit more then you need to develop a "training" or "drill" round. In addition to looking and weighing the same it may enable you to make pre-flight settings and may include a weapon response simulator (WRS) that provides the crew with the appropriate indications. The Vulcan used to carry a separate WRS (WRS 105) that could be used independently of a Shape and or in conjunction with the 28lb practice bomb. The WRS could be pre-programmed with a limit range of faults. All of these rounds were usually referred to as "shapes" although official documents may have used a different nomenclature.
You can then take things a stage further. Nuclear weapons are complex beasts with possibly multiple release modes. You not only need to test the ancillary systems in the design and testing phase but ensure they maintain serviceability when released to the front line. To achieve this you produce a number of rounds that are technically identical in all respects to the operational round except that they contain no fissile material. You would handle and store it in exactly the same way as the real thing and then return it to the manufacturing facility for strip inspection. You may even elect to drop a few for "proof" testing. In the UK these were described as "surveillance rounds". I never actually saw a surveillance round; they were quite rare; and I believe that most were issued to the RN as this was judged the most demanding environment. I suspect that these too would have sometimes been referred to as a "shape".
Then you get to the US weapons"..........er let's not go there, life is confusing enough!
YS
Last edited by Yellow Sun; 27th Aug 2017 at 07:14.