RL10 clarifications

[zorg2044]

Made a couple of changes to the Centaur pages regarding the RL10s for Centaur II and III.

Centaur II

LV	Engine
Atlas II	2xRL10A-3-3A
Atlas II-A	2xRL-10A-4
Atlas II-AS	2xRL-10A-4
Atlas III-A	1xRL10A-4

Centaur III

LV	Engine
Atlas III-B	1x or 2x RL10A-4
Atlas II-A	1x or 2x RL-10A-4
Atlas V	1x or 2x RL-10A4-2
Atlas V (present day)	1x or 2x RL-10C-1

• Per the Lockheed Martin payload planners guide covering Atlas II-A, II-AS, III-A and III-B, the extendible nozzle is optional on versions of Centaur II and III applicable to those LVs. This thread shows some photographic evidence of the variation in nozzle choice on Atlas III https://forum.nasaspaceflight.com/index.php?topic=2574.0

• The 2010 Atlas V payload planners guide, the most recent publicly available specifies a fixed nozzle for single engine centaur and extendible for dual. However the DEC was never used until recently for Starliner and the footage shows a fixed nozzle RL10-C-1 in use. https://youtu.be/HneVxAmYcaA?t=15291

[zorg2044]

keeping this issue open as I want to double check a couple of points and sort out the precise versions of the RL10-A4 and any differences in case they're relevant to our configs.