# How long does it take to power up/shut down a warp core?

The warp core seems to be an immensely powerful and vital part of a starship. I'm pretty certain that when there have been issues with them, captains have been advised that it takes a significant amount of time to restart them or make any important changes. Yet, presumably in a shuttlecraft, they are switched on and off pretty frequently. Or are they kept on even when sitting in a hangar?

So, how long does it take to switch on or power down a warp core?

• About ten minutes each way. Much quicker if the ship is already warmed up which I'd guess would be the case with the ship's shuttles. – Valorum Aug 10 '15 at 21:00
• @Richard Is that your 'I'm writing an answer' comment? – ThruGog Aug 10 '15 at 21:07
• Yes. I'll have a stab at this. – Valorum Aug 10 '15 at 21:35

## Starting the core

The problem with answering this question is the way it's framed. Starting (or rather restarting) the warp core occurs in a variety of distinct stages;

• Heating up the chamber
• Allowing antimatter to enter the chamber
• Refining the mixture to allow warp plasma to be generated.

The second and third part of the sequence appears to only take a few minutes (at most) and we actually see an entire start sequence in TNG: Phantasms. The problem is that it's impossible to determine how long was spent priming the chamber in the first place.

The TNG Technical Manual describes the startup procedure in great detail but only refers to the first part of the process being done "slowly" without indicating if this is intended to take minutes or hours.

The normal power-up sequence of the engine, as managed by the MCPC, is as follows:

1. From a cold condition, the total system temperature and pressure is brought up to 2,500,000K using a combination of energy inputs from the electro plasma system (EPS) and the MRI, and a "squeeze" from the upper magnetic constrictors.

2. The first minute amounts of antimatter are injected from below by the ARI. The lower MCS array squeezes the antimatter stream and matches its aim with the MRI above, so that both streams land at exactly the same XYZ coordinates within the M/ARC. The largest reaction cross-section radius is 9.3 cm, the smallest 2.1 cm. The stream cross-sections of the upper and lower MCS can vary, depending on the power level setting.

3. The engine pressure is slowly brought up to 72,000 kilopascals, roughly 715 times atmospheric pressure, and the normal operating temperature at the reaction site is 2 x 1012K. The MRI and ARI nozzles are opened to permit more reactants to fill the vessel. The ratio is adjusted to 10:1 for power generation. This is also the base ratio for making Warp 1 entry. The relative proportions of matter and antimatter change as warp factors rise until Warp 8, where the ratio becomes 1:1. Higher warp factors require greater amounts of reactants, but no change in ratio.

Other start-up modes are available, depending on the specifics of the situation.

## Shutting down the core

Normal shutdown

The core itself can be taken "offline" within a matter of seconds by simply mis-aligning the warp plasma conduits. This prevents the plasma from reaching the engines.

Under normal circumstances, it appears that shutting down the entire core is generally a no-no since it results in having to extensively recalibrate the chamber and start a new reaction cycle. This could, presumably, take hours to fix if it's not done properly.

It's certainly possible to start a warp core from "cold" (e.g. without priming the chamber first) so it's reasonable to assume that shuttlecraft are merely kept in a state of readiness without actually having the warp core online at all times.

TORRES: Check again. Come to join the party? We're trying to cold start the warp core for the fifteenth time. - Voy: Human Error

As far as shutdown procedures are concerned, again, we can turn to the Manual.

The normal shutdown of the WPS involves valving off the plasma to the warp field coils, closing off the reactant injectors, and venting the remaining gases overboard. The impulse propulsion system (IPS) would continue providing ship power. In one shutdown scenario, the injectors would be closed off and the plasma vented simultaneously, the system achieving a cold condition within ten minutes. High external forces, either from celestial objects or combat damage, will cause the computer to perform risk assessments for "safe" overload periods before commanding a system throttleback or shutdown.

And the system can also be shut down in a far more dramatic (albeit more damaging) way if the need arises, basically by dumping the core and

Fuel and power supplies are automatically valved off at points upstream from the affected systems, according to computer and crew damage control assessments. Where feasible, crews will enter damaged areas in pressure suits to assure that damaged systems are rendered totally inert, and perform repairs on related systems as necessary. If the WPS is damaged in combat, crews can augment their normal pressure suits with additional flexible multilayer armor for protection against unpredictable energy releases. Engineering personnel may elect to delay effecting system inerting until the ship can avoid further danger. Exact repair actions dealing with damaged WPS hardware will depend on the specifics of the situation.

## Shutdown and Restart

This is actually rather easier to answer since we actually see it happen in Voyager: Cathexis, Tuvok shuts the engine down. Torres then needs two hours to get it back up and running:

JANEWAY: You've initiated an emergency warp core shutdown.

TORRES: What?

JANEWAY: Too late. The warp core is offline. It'll take at least two hours to regenerate the dilithium matrix. Ensign, get the rest of the systems back online. Apparently, you've just crashed the main computer, locked out the Bridge and stopped this ship cold. Do you want to tell me why?

• So it's pretty quick to start it up or shut it down, but to do a restart takes considerably longer? Or is this due to the conditions in this episode do you think? – ThruGog Aug 11 '15 at 9:10
• @thrugog - The implication is that much like a real world nuclear reactor, the faster you close it down, the more damage you do to it. – Valorum Aug 11 '15 at 11:24

Remember Scotty wrote most of the manuals for the Federation's engines, so he fudged on time so he would be considered A MIRACLE WORKER. He said this to Lt. Commander Geordi La Forge when he guest started on TNG's Relics. "Star Trek: The Naked Time (#1.4)" (1966) The crew is infected with a mysterious disease that removes people's emotional inhibitions to a dangerous degree. http://www.imdb.com/title/tt0708473/

Uhura: [over the intercom] Entering planet's outer atmosphere, sir. Scotty: Captain! Capt. Kirk: What is it? Scotty: He's turned the engines off. They're completely cold. It'll take 30 minutes to regenerate them. Uhura: [over the intercom] Entering planet's outer atmosphere, sir. Ship's outer skin is beginning to heat, Captain. Orbit plot shows we have about 8 minutes left. Capt. Kirk: Scotty! Scotty: I can't change the law of physics! I've got to have 30 minutes!

Capt. Kirk: The purpose of a briefing, gentlemen, is to get me answers based on your abilities and experience. In a critical orbit there's no time for surprise. Scotty: Unless you people on the bridge start taking showers with your clothes on, my engines can pull us out of anything. We'll be warping out of orbit within a half second a' getting your command.

• I'm reasonably sure that he was trying to restart the sub-light engines, not the warp drive. – Valorum Dec 15 '16 at 15:15