Yikes, I'm so glad that rear end never appeared on screen! It also suggests that someone misunderstood the function of the travel pod - it's not something that was ever supposed to operate anywhere but short distances over a micro gravity environment, where small thrusters would be more than sufficient. Probably true (I can imagine someone asking "why hasn't this rocket ship got a rocket on the back?") but it also continues a trend begun in TMP of explicitly showing more "realistic" (i.e. 20th century) rocket technology on Starfleet vessels, such as the RCS thrusters.