A diagram showing the models of RS-25 used during the Space Shuttle programme, and two possible expendable versions.
NASA
<a rel="nofollow" class="external text" href="http://www.nasa.gov/centers/marshall/ppt/134663main_6976_coalition_MSFC_ESAS_Rollout-092205.ppt">MSFC and Exploration: Our Path Forward</a> (PPT). NASA (September 2005).