E-1
... that Rocketdyne's E-1 rocket engine never saw production, but gave NASA confidence to develop the F-1 that powered the Saturn V to the Moon?
... that <a href="./Rocketdyne" id="mwAq8" rel="mw:WikiLink" title="Rocketdyne">Rocketdyne</a>'s <b id="mwArA"><a class="mw-redirect" href="./E-1_(rocket_engine)" id="mwArE" rel="mw:WikiLink" title="E-1 (rocket engine)">E-1</a></b> <a href="./Rocket_engine" id="mwArI" rel="mw:WikiLink" title="Rocket engine">rocket engine</a> never saw production, but gave <a href="./NASA" id="mwArM" rel="mw:WikiLink" title="NASA">NASA</a> confidence to develop the <a class="mw-redirect" href="./F-1_(rocket_engine)" id="mwArQ" rel="mw:WikiLink" title="F-1 (rocket engine)">F-1</a> that powered the <a href="./Saturn_V" id="mwArU" rel="mw:WikiLink" title="Saturn V">Saturn V</a> to the Moon?