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>The two most unscientific words in Star Trek are probably "full stop" Such a promising article, and then they completely miss the mark THERE IS NO SUCH THING

>The two most unscientific words in Star Trek are probably "full stop" Such a promising article, and then they completely miss the mark THERE IS NO SUCH THING AS A FULL STOP IN SPACE. There is no frame of refernece to stop against. It's completely meaningless, and has nothing to do with limitations of deceleration

nomel 4y ago
Oh, that’s silly, for a practical context, which flying a spaceship would be. Practically, it would be relative to the nearest large body/galaxy/pair, and depend on context, which would almost always be understood. For example, if you’re observing a planet, full stop would be relative to that planet.
- paulsutter 4y ago
  So full stop means either go to geosynchronous orbit or fall to the surface?
  - nomel 4y ago
    Since human occupied spaceships are never meant to fall from space, except for the illegal suicide vessels found near Vermiticus 4, I think the practical answer would be geosynchronous orbit.
spuz 4y ago
Presumably at those speeds, the frame of reference would be the galaxy and the interstellar material in which the ship travels. If your ship were to match the average speed of this material, then you could claim to be at a stop. If the concern was to prevent damage due to collision with this material, then it makes sense that in order to "stop" you would actually have to match the speed of the material that you are moving through.
jcrawfordor 4y ago
This really all stems from a misunderstanding of what "full stop" or "all stop" (all engines, for vessels that commonly operate only some engines for cruising) means. "full stop" is a position on the engine telegraph that tells engineering to stop the engine or take it out of gear, depending on the type of propulsion setup. It has nothing to do with the speed of the ship relative to anything, after the "full stop" order is given the ship will continue to move forwards by momentum. If the captain actually wants to stop as soon as possible they will order "full astern," which signals engineering to run the engine in reverse at normal full speed, effectively braking. Because oceangoing ships stop on their own reasonably quickly this is usually more of an emergency maneuver. The fact that motion is relative is already quite true at sea in our own world, where in at-sea operations your position relative to other vessels can matter much more than your position relative to the earth. In other words this issue is not at all new or specific to space. More basically, though, today and presumably centuries into the future "full stop" is not an order to stop the ship, it's an order to stop the engine. The order is "full stop" because large marine engines are traditionally directly coupled to the propshaft and cannot "idle" per se. On these types of systems, still common on large vessels, there is some nuance depending on the engine setup between "standby," "stop," and "finished" which are traditionally all positions on the engine telegraph that do more or less the same thing but give different instructions to the engineer operating the engine as far as preparations for the near future. On top of this most ships today the "engine telegraph" is not really used when underway and the telegraph sender on the bridge actually controls the engine directly via automation, but usually this only allows for speed changes and not stopping or reversing, which still requires that engineering take over engine control due to the preparations and checks that must be done when stopping and starting the engine. Rather than telegraph bells this is more likely to be a phone call these days.
deleted 4y ago
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nomel 4y ago

Oh, that’s silly, for a practical context, which flying a spaceship would be. Practically, it would be relative to the nearest large body/galaxy/pair, and depend on context, which would almost always be understood. For example, if you’re observing a planet, full stop would be relative to that planet.

paulsutter 4y ago
So full stop means either go to geosynchronous orbit or fall to the surface?
- nomel 4y ago
  Since human occupied spaceships are never meant to fall from space, except for the illegal suicide vessels found near Vermiticus 4, I think the practical answer would be geosynchronous orbit.

spuz 4y ago

Presumably at those speeds, the frame of reference would be the galaxy and the interstellar material in which the ship travels. If your ship were to match the average speed of this material, then you could claim to be at a stop. If the concern was to prevent damage due to collision with this material, then it makes sense that in order to "stop" you would actually have to match the speed of the material that you are moving through.

jcrawfordor 4y ago

This really all stems from a misunderstanding of what "full stop" or "all stop" (all engines, for vessels that commonly operate only some engines for cruising) means. "full stop" is a position on the engine telegraph that tells engineering to stop the engine or take it out of gear, depending on the type of propulsion setup. It has nothing to do with the speed of the ship relative to anything, after the "full stop" order is given the ship will continue to move forwards by momentum. If the captain actually wants to stop as soon as possible they will order "full astern," which signals engineering to run the engine in reverse at normal full speed, effectively braking. Because oceangoing ships stop on their own reasonably quickly this is usually more of an emergency maneuver. The fact that motion is relative is already quite true at sea in our own world, where in at-sea operations your position relative to other vessels can matter much more than your position relative to the earth. In other words this issue is not at all new or specific to space. More basically, though, today and presumably centuries into the future "full stop" is not an order to stop the ship, it's an order to stop the engine. The order is "full stop" because large marine engines are traditionally directly coupled to the propshaft and cannot "idle" per se. On these types of systems, still common on large vessels, there is some nuance depending on the engine setup between "standby," "stop," and "finished" which are traditionally all positions on the engine telegraph that do more or less the same thing but give different instructions to the engineer operating the engine as far as preparations for the near future. On top of this most ships today the "engine telegraph" is not really used when underway and the telegraph sender on the bridge actually controls the engine directly via automation, but usually this only allows for speed changes and not stopping or reversing, which still requires that engineering take over engine control due to the preparations and checks that must be done when stopping and starting the engine. Rather than telegraph bells this is more likely to be a phone call these days.

deleted 4y ago

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