posted
An RCS would not be sufficient. Imagine this scenario: You turn on a SSF to lower the effecive mass of the ship. Then you turn on your impulse engines (essentially a fusion rocket) and your ship moves very fast. Fine. Then you want to stop so you turn off the SSF, your ship is effectively more massive, so it slows down. Good. Problem is, even though you are travelling slower, since the ship is now more massive (effectively) the ship still has the SAME momentum, no change there... That means that you still need an equal force to stop the ship as it took to get it moving, this is from the impulse engines. The RCS will not be able to produce nearly the same thrust as the impulse engines and would not stop the ship (unless you had a very long burn).
That's why I still think something like the IDF still needs to be involved somehow. You need a device that actually reduces the kinetic energy of the ship without producing an equal but opposite thrust.
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quote:Originally posted by Capt_Frank_Hollister: An RCS would not be sufficient. Imagine this scenario: That's why I still think something like the IDF still needs to be involved somehow. You need a device that actually reduces the kinetic energy of the ship without producing an equal but opposite thrust.
What about using the sheilds to vector the thrust? I recall reading about that somewhere besides the ST:TNG tech manual.
posted
It's a possibility, but one I'm not particularly fond of for one main reason: That's the sort of thing that should be corroborated by on-screen evidence; my scheme is essentially "invisible" and thus would fit better with on-screen evidence.
There's also a more general problem I have with the switching-off-the-SSF-to-slow-down scheme. In order to slow the ship down from relativistic speeds to something that could in any way be considered "slow" would require an effective change in mass of many orders of magnitude. I had always been under the impression that the SSF only reduced the ship's effective mass by less than 50% and not more than 90% (figures I just pulled out of my... well, never mind). I figured it just made the ship a bit less massive, not light as a feather.
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quote:Originally posted by Capt_Frank_Hollister: It's a possibility, but one I'm not particular fond of for one main reason: That's the sort of thing that should be corroborated by on-screen evidence; my scheme is essentially "invisible" and thus would fit better with on-screen evidence.
I agree that Occam's razor holds, I just lack really good data on those systems.
I'm looking at McMaster's bridge blueprints and several systems are presented for the helmsman but no specifics. There are controls for stop, three rates forward and three reverse. There's also an indication that Manuevering is a seperate system as are Propulsion, Communications, Sensors, Weapons, and Computer systems.
quote:Originally posted by Capt_Frank_Hollister: It's a possibility, but one I'm not particularly fond of for one main reason: That's the sort of thing that should be corroborated by on-screen evidence; my scheme is essentially "invisible" and thus would fit better with on-screen evidence.
I like the forcefield idea since it explains the wierd positioning of impulse engines on some ships. Note that in the various brigs, air does not show up on the forcefields, so perhaps thrust wouldn't either. Of course, the forcefields would need to be rather powerful to contain the thrust, but combined with the subspace field, it would presumably be managable.
quote:: There's also a more general problem I have with the switching-off-the-SSF-to-slow-down scheme. In order to slow the ship down from relativistic speeds to something that could in any way be considered "slow" would require an effective change in mass of many orders of magnitude. I had always been under the impression that the SSF only reduced the ship's effective mass by less than 50% and not more than 90% (figures I just pulled out of my... well, never mind). I figured it just made the ship a bit less massive, not light as a feather.
On the first DS9 episode the station moved quite a bit with weak thrusters. The time without the subspace field would be two months, but with the field, the movement was fairly quick (under a day, but I don't remember exactly). This means that the subspace field reduced the mass by at least two orders of magnitude, and probably quite a bit more.
quote:Originally posted by Capt_Frank_Hollister: You turn on a SSF to lower the effecive mass of the ship. Then you turn on your impulse engines (essentially a fusion rocket) and your ship moves very fast. Fine. Then you want to stop so you turn off the SSF, your ship is effectively more massive, so it slows down. Good. Problem is, even though you are travelling slower, since the ship is now more massive (effectively) the ship still has the SAME momentum, no change there...
Why would a ship slow down if its more massive?
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When the SSF of a ship is turned off, the ship maintains the same kinetic energy but its effective mass is increased. Using the above equation, for this to be true, the velocity of the object must be reduced in order for the now more massive object to have the same kinetic energy. If the velocity of the object did not decrease, then it would gain kinetic energy from an undefined source and thus violate the first law of thermodynamics (energy cannot be created nor destroyed, in this case created).
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posted
The more I think I about it the more I like the IDF scheme. What we need to stop the ship (without turning the ship around a firing the impulse engines the other way) is some device that can bleed te kinetic energy (KE) of the ship of into another form. The most likely interface would be some treknological field projected over the entire ship, like the IDF. Thinking of inirtia as an object's resistance to a change in its motion unless acted upon by a force proprtional to the change in motion and the objects mass, in bleeding off the ship's KE we really are dampening the ships inirtia, at least in effect. We would be changing its motion (slowing it down) without exerting a force, a motion that would otherwise be maintained by its inirtia. IDF really seems to fit the bill.
Also, if it were the case that the kinetic energy could be transfered to a working fliud on board the ship, perhaps in the form of heat (and maybe converted and pumped into the EPS system), this scheme would have significant advantages over simply turning the ship around and firing the engines. Why? Because you would actually be recovering a good deal of the energy that you expended getting the ship going. It's like modern electric hybrid cars that use a generator attached to the wheels to recharge the batteries of the car when breaking, energy which initially came from those same batteries. Thus this scheme would be the prefered method of slowing and stopping the ship rather then expending more energy (that would be lost) in firing the engines again.
Finally, if the IDF was applied asymetricly across the ship, it might explain why ships in Star Trek turn more like cars or airplanes rather than how one would expect them to behave in frictionless space. (And this method would, again, conserve energy).
Thoughts?
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posted
If you're trying to make it realistic (i.e. considering things like conservation of energy, momentum, etc) just remember that since motion is relative, any trick you can use to "stop" can also be used to "start".
If you have a Plot Device that can slow a ship from 0.5c to 0c in time T using energy E, then simply by changing your reference frame (putting the camera somewhere else, as it were) you can use the same device to accelerate from 0c to 0.5c in time T with energy E.
Most Star Trek physics can only be salvaged by appealing to a privileged reference frame - this is probably another one of those cases where you just have to assume coming to rest with a special frame takes far less energy than accelerating relative to the special reference frame. Once you've established that, any sort of magical device or field can work.
Interestingly, this is the opposite assertion of the "subspace anchor" theory in dominance before the TNG:TM came out. At that time, the concern was how ships slowed from warp speed, and the idea was that the ship needed some active mechanism to overcome "warp inertia". Now it is generally assumed that a ship must expend constant energy to stay in warp, otherwise it will revert to relativistic speeds.
posted
True. Star Trek, and most people's intuitions for that matter, generally apeal to an "objective" reference frame which doesn't really exist. I think that that object reference frame is itself a "Plot Device," as you call it. If you want, you could call the subspace field this this objective reference frame. In many way the subspace field has always been analogous to the theorized (and disproven) "ether." Star Trek basically renamed it and started assigning all kinds of magical properties to it.
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quote:Originally posted by Capt_Frank_Hollister: You turn on a SSF to lower the effecive mass of the ship. Then you turn on your impulse engines (essentially a fusion rocket) and your ship moves very fast. Fine. Then you want to stop so you turn off the SSF, your ship is effectively more massive, so it slows down. Good. Problem is, even though you are travelling slower, since the ship is now more massive (effectively) the ship still has the SAME momentum, no change there...
Why would a ship slow down if its more massive?
It would'nt, but the lower mass would allow RCS to slow the ship.
Personally, I think the Impulse Engines affect spacetime in whatever direction their field is tuned to -regardless of which direction the glowy vent is pointing. It's NOT a rocket providing conventional thrust- if it were, landing shuttles would be nailed by it's wake on almost every class of starship.
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posted
Ah, but they are essentially rockets, with vectored thrust to boot. Landing shuttles would only be harmed if the impulse emgines were actually in the middle of a burn.
And turning off the SSF and increasing the effective mass of the ship would indeed slow a ship down. Otherwise, the ship would violate the first law of thermodynamics. See my post about five posts up using the equation for kinetic energy It just wouldn't be able to bring it to a stop. My post at the top of the page explains why the RCS would not be able to stop the ship.
And I don't mean to harp on it, but the impulse engines didn't have SSF generators until teh Ambassador class.
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posted
When I originally posted this topic, I didn't know if there was an 'official' method for stopping a starship. Since I have been talking to Ed Whitefire for the interview, I have found out that there was, but you will have to wait for the interview.
That said, I think that there have been a number of good theories put forward.
posted
"Official" is whatever I say an any given moment.
...and no, the Impulse engines are not rockets: we see them glowing even when the ship is at full stop and not all ships display any impulse vent (The Nebula, Hediki, many freighters and shuttles, all Romulan ships)
If they were "rockets" or directed thrust, why are some impulse systems blue?
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