Star Trek Impulse drive and how do they stop the thing?

Star Trek Impulse Drive

Since I don’t have any builds going at the moment I thought I would talk about some Star Trek tech. Now there are a lot of people who talk about Star Trek tech, with one of the best being Trekyards on Youtube, but I haven’t talked about it, so there.

Star Trek’s Impulse Drive.

Of all the future tech Star Trek uses one of the least detailed is the ‘impulse drive’. Which is rather odd as it’s probably the technologies that is closest to our own.

What we do know is this; it’s a standard Newtonian reaction drive, it is powered by fusion reactors (TOS timeline) and has a maximum speed is about ¼ c (¼ the speed of light). Now how it works, to my knowledge, this has never been said in canon. What we can guess is it’s, probably, not an ion drive as Scotty commented that the aliens in ‘Spock’s Brain’ (ugh) could tech them something about ion propulsion. And it’s defiantly not chemical as that would not get you anywhere near the speed of ¼ c.

(Since I mentioned the abysmal ‘Spock’s Brain’, a side note of the 3rd season of Star Trek TOS. A lot of people really rag on the third season episodes as being much worse then the first two seasons. Now, ‘Spock’s Brain’ and ‘and the children shall lead’ DID come from that season. But, ‘The Enterprise Incident’, ‘The Paradise Syndrome’, ‘For the world is hollow..’ and ‘Let that be your last battlefield’ among others also came from the third season. So give them a break.)

Atomic explosions as thrust? Could they just be funneling a fusion explosion out the back of the impulse vents? Possibly. In the Star Trek universe, it is fairly obvious that they are really good and magnetic containment. Even in battle the anti-matter storage never manages to touch the matter containment walls. So, if you used a magnetic containment to focus the explosion out the back of the craft, that would produce considerable thrust without melting the walls of the thruster. Would it be enough to get the Enterprise up to ¼ c? I have no idea. Some of the estimates I have read for atomic propulsion have it maxing out at about tenth of the speed of light. But, that is our current estimates, their mileage may vary.

But there is a problem. The ships of Star Trek only have the impulse on the back of the ships and we never see the ships turn around to slow down. To slow down a star ship traveling at ¼ c you need to thrust the same amount of energy that got you to ¼ c, in the opposite direction. The small thrusters on the front of the craft would not be anywhere strong enough. So what do they do? Do they, quickly, turn the ship around then turn it back and we just don’t see it? From what I have seen, that doesn’t seem to be the case. Instead, they just seem to turn the impulse engines off.

(Now before someone writes me as says, ‘Get a life! They did it that way because it would make more sense to 1960 audiences that knew nothing of ‘conservation of momentum’ or other geeky long haired physics crap like that. Well, OK, I don’t have a life but that’s beside the point. 🙂 To make good sci-fi your world needs to comply, mostly, with the real world and this is one point where Star Trek really falls down.)

So how do they stop?

Lots of jets use thrust re-directors on the back of the engines to re-direct thrust forward to slow down the plane. We don’t see any such devices on or around the impulse thrusters, although they could be hidden but I doubt it. They could also be using some form of a force-field to do the redirection, but that wouldn’t work with the series Enterprise since they were still developing force-fields at the time.

What about something exotic like negative energy? An interesting thing about negative mass is if you pushed on it it would push back. The more you tried to push it forward the more it would try to push in the opposite direction. Very strange. Blast a thrust of negative mass/energy out the back and you slow the ship down. In warp theory you would need negative energy to work so that tech would probably be available.

Another option is use the warp drive to slow the ship. Just quickly warp the ship backward and the ship stops. Since you would be under the speed of light you would not need to invoke the warp bubble so a quick stretching of space behind the ship would easily bring it to a stop. You would be doing the equivalent of creating a gravity well behind the ship.

Enough on stopping the ship. As with any Star Trek tech, you can always come up with some of making it fit.

There is lots of diagrams and explanations in the various non-canon and somewhat canon books out there if one wants to read up on the impulse drive, have fun. I read a lot of those books myself and rather enjoy them.

Anyway, that’s it for now.

Be cool, the field mouse


3 thoughts on “Star Trek Impulse drive and how do they stop the thing?

  1. I find myself falling down these rabbit holes of questions around lots of televised Science Fiction. They are fun little problems to think about, the whole concept of acceleration and deceleration in space is a fun one (and often raises a lot of questions when it comes to shows or movies). Good post


  2. I like to think about all the “impossibility” of these things (Star trek, star wars, back to the future etc. etc.) as, well… because their reality is far different then ours. Haha! But even saying that, I still get caught up in the “no way that would work” sort of thing for so many “laws” being broken. Don’t get me started on The Matrix. Ahhh movies, (and TV) gotta love em.


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