# Are Vessels in Star Trek able to travel at speeds between 0.25x and 1.0x the speed of light?

Based on what I recall, full impulse is 0.25c and warp 1 is 1.0c. Are ships in the Star Trek universe capable of travelling at speeds that span that interval?

If so, how and what do they call it?

Yes, they can: limiting full impulse at 0.25c is only a regulation, not a technical limitation.

According to the Star Trek TNG RPG Core Book by Last Unicorn Games, on page 246:

One-quarter the speed of light is the Federation standard for full impulse speed. Ships can exceed this speed, but usually do not; it's more energy efficient to go to warp speed.

Then on Star Trek RPG Player's Guide by Decipher, on page 195:

Most impulse drives allow speeds of .1 to .75c, but the most advanced models can propel a ship at speeds up to .95 c. Starfleet refers to .25c as "full impulse", since faster rates usually warrant travelling at warp speed instead. Only emergencies prompt captains to order higher impulse velocities.

We also see the Enterprise travel faster than .25c in The Motion Picture, as explained on the Impulse drive article on Memory Alpha:

In The Motion Picture, The Enterprise traveled at warp 0.5 from Earth to past the planet Jupiter, a distance of (at a minimum) 390,674,900 miles, in 1.8 hours, making that speed approximately equal to 97,026 kilometers per second (217,041,611 miles per hour), or roughly 1/3 light speed. The difference may be explained by differences in orbital precession between the two planets at the time, or, as with warp drive, there may be other variables involved.

• Did you or your source typo "warrant"? Commented Oct 25, 2019 at 13:36
• That was me, thanks for pointing it out.
– Sava
Commented Oct 26, 2019 at 12:10
• This is correct. "One quarter impulse is 1/4 speed of light." Commented Oct 30, 2019 at 16:07
• You're wrong @BAMF4bacon: 1/4 the speed of light (ie 0.25c in scientific notation) is full impulse. One quarter impulse is 1/16 the speed of light.
– Sava
Commented Oct 31, 2019 at 6:30

You can go faster then .25c outside of warp speed but the effects of time dilation would start to become obvious. Space travelers would have to deal with the stress of drastically outliving their loved ones who they leave behind.

Warp takes you out of the normal flow of spacetime so it does not have the same dilation effects.

• Can you offer any quotes or references to back up these bold statements? Commented Nov 12, 2019 at 19:53
• Actually, if I remember what I read correctly, the effect of time dilation are only truly felt for speed of .95c and above. Anything below would be negligible.
– Sava
Commented Nov 12, 2019 at 21:34