An RL-10 rocket engine on display at the <a href="https://en.wikipedia.org/wiki/U.S._Space_%26_Rocket_Center" class="extiw" title="w:U.S. Space &amp; Rocket Center">U.S. Space &amp; Rocket Center</a>, with cutaway showing the tubing through the bell
<a href="//commons.wikimedia.org/wiki/User:Ke4roh" title="User:Ke4roh">James E. Scarborough</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>