In Star Trek Beyond, they fix up the old Federation ship, USS Franklin. It wasn't made to fly in atmosphere, so in order to take off they need to propel it off a cliff and reach terminal velocity before the impulse engines can fire. (From what I can recall from a single viewing - if any of those assumptions are wrong please correct.)

What I don't understand is how does terminal velocity allow impulse engines to just "start working"?

  • 8
    Because terrible writing.
    – Valorum
    Aug 6, 2016 at 12:36
  • 2
    Maybe they were out of fuel and the distance traveled at terminal velocity is what it took to collect enough hydrogen via the bussard collectors? Sounds pretty silly to me.
    – Shamshiel
    Aug 6, 2016 at 12:36
  • 1
    It was not the laws of physics, it was the Rule of Cool. Were it not already slated to be used at the climax of the movie, I'm certain that the resonant vibrations from Sabotage would have been necessary to counter-strafe the new clanex recompensators.
    – gowenfawr
    Aug 6, 2016 at 14:04
  • 1
    Here's a question. If there was a chance that the ship could plough into the ground, killing all on board, why didn't they have the crew off the ship when they took off, then beam them back on board when it was safe?
    – Valorum
    Aug 14, 2016 at 12:50
  • Putting Treknobabble to one side, the writers need to learn the difference between a "jump start" and a "bump" start (also known as a push or clutch start). It was launched off a cliff, there were no cables attached to another ship or slave battery at any time.
    – Zara
    Dec 3, 2016 at 8:06

3 Answers 3


The quote from the film is

Kirk: Scotty, can you get this thing started?

Scott: Started yes, Sir. Flying, that's a different thing. These old vessels, they were built in space. They were never supposed to take off from atmosphere.


Chekov: We have to achieve terminal velocity in order for the stabilizers to provide lift.

Quite why this is the case isn't explained other than it being treknobabble to explain why they need to push the ship off of the cliff.

Stabilizers are, at least in the Abramsverse, an integral part of starship atmospheric flight

“Mr. Sulu,” Spock exclaimed, “divert all remaining power to stabilizers!” “Doing what I can, sir,” the helmsman replied as he desperately fought to comply. “Doing what I can.”
Spock tried his best to see that the Enterprise’s vanishing energy resources were parceled out meticulously among the ship’s most critical active systems. While life support drew the most attention, he and Sulu attempted to steady the starship’s wildly skewing and rapidly failing artificial gravity. If he couldn’t stabilize it any better, there was a good chance a large percentage of the ship’s crew would never be able to make it to their assigned evacuation stations. Yet if he shunted power from life support to the precessers, there was a chance atmospheric pressure would fall too low and kill everyone on board.

Star Trek Into Darkness - Official Novelisation

  • Good work, +1. I think this is the best we'll get. (Too bad there's no one associated with the reboot films here at the Vegas convention for me to ask.)
    – Praxis
    Aug 6, 2016 at 16:14
  • @Praxis - I'm still kicking myself about missing the IAMA on Reddit with Justin Lin and Simon Pegg.
    – Valorum
    Aug 6, 2016 at 16:22

Spaceships in atmosphere are usually depicted as flying due to downward force from an engine, like a hovering harrier. Since the Franklin wasn't designed to fly in atmosphere, it may not be able to direct sufficient force in a downward direction to effect a vertical takeoff.

So, if it can't just take off straight up, it must need to generate lift a different way. Assuming that the ship is producing lift via Bernoulli's Principle and an airfoil, needing a jump start makes perfect sense.

The lift generated by an airfoil is dependent upon the speed at which the craft is moving through the air. This means that the craft needs to get going fast before it can actually fly. This is why commercial aircraft require long runways, so they can get up to speed. As you may have noticed, there was no runway in front of the Franklin.

Therefore, before the ship could fly under its own power, it needed to get going fast enough that the stabilizers could keep it flying, despite providing minimal lift on their own. This required falling off a cliff.

In other words, it's just what Chekov said:

We have to achieve terminal velocity in order for the stabilizers to provide lift.

  • This answer seems like a reasonable rationalisation. However it would be improved with evidence that the Franklin had the properties of an airfoil.
    – Blackwood
    Aug 13, 2016 at 4:15
  • @Blackwood That would be great, I agree. The only evidence I have of that is that it was able to fly, and that it seems to be what is implied by the events of the movie. Perhaps if I had a copy of the movie I could come up with something else.
    – DCShannon
    Aug 13, 2016 at 4:28
  • All signs point to the stabilisers being some sort of anti-grav system rather than aerofoils. Giving them more power wouldn't work otherwise.
    – Valorum
    Aug 13, 2016 at 7:37
  • @Valorum I'm assuming that the stabilizers are some sort of propulsion system, i.e. "stabilizing thrusters". If you have some evidence regarding what they actually are, that would certainly be useful.
    – DCShannon
    Aug 14, 2016 at 12:34
  • @dcshannon - Alas, I have nothing. These new films favour dramatic content over any semblance of technical coherence. That being said, in the previous film Spock gives his stabilisers more power to make them be more stabilising.
    – Valorum
    Aug 14, 2016 at 12:48

They specifically get the inspiration from the idea of the jumpstart. Then they basically "push started" the starship. So I'm assuming the older starships have a manual transmission, and they popped the clutch after getting up to speed. On a car, the wheels transmit the motion to the engine and engaging the engine suddenly can get the engine running without a battery. So, I guess there's something that rotates or moves on the basis of the air (or solar wind?) traveling on the outside of the hull, and engaging the engines suddenly allowed them to start without the power cells working.

But honestly, this part of the movie bothers me more than anything else they've done. It just makes no sense at all!


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