The Constitution-class starship is one of the most recognizable ships of the Federation's starfleet and is a definitive symbol for the "Star Trek" franchise. This article deals with the performance of one of the most famous starships of this class, the refitted USS Enterprise, in the first Star Trek feature film: Star Trek: The Motion Picture. Impulse drive is the propulsion system that many ships in Star Trek use to get around while inside solar systems and traveling below the speed of light (termed "sublight propulsion"). Though this propulsion system commonly takes a back seat to the more prominent warp drive (which normally moves ships faster than light), it is nonetheless an impressive technology with capabilities that are often taken for granted in the grand scheme of interstellar space travel. In comparison to the distances which separate the stars, the distance between the planets in the solar system can seem quite negligible, but in comparison to even the most extended modern human journeys, they are not. This article should help to better illustrate the still-vast distances between planets that orbit the sun, as well as how impulse drive has been used to deal with traversing them.

The newly refitted Enterprise waits in drydock above Earth

There is a basic timeline to consider which is illustrated in The Motion Picture that begins when the Enterprise is first launched from drydock above Earth (about 32 minutes into the movie if you wish to follow along). In this timeline, there are five key events to consider:

1.		2.		3.		4.		5.
	Leaving Drydock		Leaving Orbit		Engage Impulse		En Route		Arrival at Jupiter

According to the National Space Science Data Center, the distance between Earth and Jupiter varies from about 968 million kilometers (maximum) to 588 million kilometers (minimum); anywhere from about 1,529 to 2,518 times the distance from the Earth to the moon.

Given these distances, deriving a range of how fast (on average) the Enterprise was moving from Earth to Jupiter would also require a measure of the time it took to cross this distance. One possible way to find a value would be to look at screen time; literally how much time passed between the shot where the Enterprise is shown leaving Earth and the shot where it is seen flying past Jupiter. But movies often take artistic liberty with the passage of time for the sake of keeping the audience interested or to enhance a sense of suspense or drama. Fortunately for us, in this instance Captain Kirk himself provides a value:

Shortly after passing Jupiter, there is a voiceover of Captain Kirk making an entry in his log. He describes their current situation and also gives the audience a time value of how long they've been traveling inside of the Solar System: 1.8 hours, or 108 minutes. This makes it possible to derive a range of speeds the Enterprise would have to be moving at in order to reach Jupiter in the time allotted.

Average Velocity can be derived by the following formula:
Average velocity = Distance / Time

If Jupiter were it's closest to Earth, the distance would be about 588,500,000 kilometers; the time would be about 108 minutes, or about 6,480 seconds. This works out to an average velocity of about 90,818 kilometers per second, or about 1/3 the speed of light.

If Jupiter were it's farthest from Earth, the distance would be about 968,100,000 kilometers; the time would still be about 6,480 seconds. This works out to an average velocity of about 149,398 kilometers per second, or about 1/2 the speed of light.

That's extremely fast, but still sublight; all of this occurred before Kirk decided to risk engaging the warp drive (which resulted in a wormhole accident because of an engine imbalance).