Assertion: space shuttle's engine | /r/HasAspect | less thrust
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text: As originally envisioned, both the Ares I and Ares V would have used a modified "throw away" version of the RS-25 engine, but in due course, because of the need to keep R&D costs down and to maintain a schedule set by NASA Administration Michael D. Griffin to launch the Ares and Orion by 2011, NASA decided (after the 2006 review) to switch to the cheaper RS-68 engine for the Ares V and to an uprated J-2 engine for the Ares I. Because of the switch to the less efficient RS-68, the Ares V was widened from 28.6 to 33 feet (8.72 to 10.06 m) to accommodate the extra propellants, while the Ares I was reconfigured to incorporate a fifth solid-rocket segment with the J-2X upper stage, as the new engine has less thrust than the original RS-25.