Correct Physics in Trek

[T'Girl]

When Kirk orders "Ahead warp .5" in ST:TMP, he may have been telling Sulu to use impulse engines to accelerate to a speed equivalent to whatever warp .5 is equal to.

Under the original warp formula, warp speed is the cube of the warp number. Warp 6 was 216 times the speed of light. So warp 0.5 would be 0.125 of lightspeed, or 37,474 kilometres per second.

A speed change at some point would have been necessary in order to reach Jupiter in 1.8 hours.

 

[Psion]

When Kirk orders "Ahead warp .5" in ST:TMP, he may have been telling Sulu to use impulse engines to accelerate to a speed equivalent to whatever warp .5 is equal to.

Under the original warp formula, warp speed is the cube of the warp number. Warp 6 was 216 times the speed of light. So warp 0.5 would be 0.125 of lightspeed, or 37,474 kilometres per second.

A speed change at some point would have been necessary in order to reach Jupiter in 1.8 hours.

Yep! Even under the best circumstances Jupiter is almost four and a half hours away at warp 0.5 if we use the old equation.

On the other hand, if Jupiter is in opposition with the sun -- and therefore at its closest to Earth -- and Kirk's order translates out to half of warp one, then Jupiter would be a little less than 1.1 hours away. Unfortunately, at no point is Jupiter ever more than about 1.65 hours away at half the speed of light. This leaves between nine and forty-two minutes unaccounted for between the departure of Enterprise from Earth and the point at which she passes Jupiter.

Fortunately, physics comes to the rescue here, as I doubt the starship instantly accelerated to half the speed of light. For a variety of reasons, the Enterprise might not have followed a perfectly straight line, either.

 

[Ronald Held]

Without being rude, thsi thread is only for physics that is correct in this universe. I cannot present the Trek extension in this talk.
Friction at high speeds should melt/vaporize most objects if they are small enough.

 

[Crazy Eddie]

Unless the magical inertial dampers are working the problem with a steep atmospheric entry might be high G forces on the crew and crushing/breakup of the spacecraft structure.

Depending on the atmosphere, it's only about three or four gees for a really intense braking maneuver. A shuttlecraft ought to be able to handle that.

With a spacecraft entering an atmosphere I'm wondering if the heating isn't so much friction in the respect most people think of it or the tremendous temperature increase that would occur as an object traveling at fifteen thousand MPH or more compesses air that was a fraction of a second ago was at near vacuum pressure.

That is, in fact, EXACTLY what causes heating when a spacecraft hits the atmosphere. It has almost nothing to do with friction.

Encounter at Farpoint:

PICARD: From this point, no station aboard, repeat no station, for any reason will make use of transmitted signals or intercom. We'll try and take them by surprise. Let's see what this galaxy class starship can do. (to Worf) Lieutenant, inform engine room to prepare for maximum acceleration.
WORF: Aye, sir.
PICARD: Records search, Data. Results of detaching saucer section at high warp velocity.
DATA: Inadvisable at any warp speed, sir.
PICARD: Search theoretical.
DATA: It is possible, sir. But absolutely no margin for error.
PICARD: Using print-out only, notify all decks to prepare for maximum acceleration. Now hear this, Maximum, you're entitled to know, means that we'll be pushing our engines well beyond safety limits. Our hope is to surprise whatever that is out there, try and outrun it. Our only other option is to tuck tail between our legs and return to Earth as they demand.

They use "acceleration" and "speed" interchangeably for the most part, the same way the average person uses "mass" and "weight" interchangeably. They are related concepts, but "weight" and "speed" are both meaningless concepts in space, even if they are incorrectly used to describe things that DO make sense.

I don't think those terms are being used interchangeably in that example. Picard is calling for maximum acceleration in order to surprise Q, and the references to speed are all related to the speeds at which the saucer separation will occur, all of which would be warp speeds regardless of the acceleration curve.

Except, again, "speed" is meaningless in space. If the saucer and the drive section are both traveling at warp 9, then their relative speed is zero and the maneuver isn't actually all that difficult.

 

[Silvercrest]

With a spacecraft entering an atmosphere I'm wondering if the heating isn't so much friction in the respect most people think of it or the tremendous temperature increase that would occur as an object traveling at fifteen thousand MPH or more compesses air that was a fraction of a second ago was at near vacuum pressure.

That is, in fact, EXACTLY what causes heating when a spacecraft hits the atmosphere. It has almost nothing to do with friction.

Ah. And the "bouncing off the atmosphere" business? Could you, in fact, brake or deflect yourself more effectively by driving in at a steeper angle (and compressing more atmosphere)?

 

[Crazy Eddie]

It's not the angle that matters, it's really your trajectory relative to the plane of the atmosphere and -- more importantly -- the shape of your craft. When Jake's engines shut down he was (for some reason) already on a heading that would cause him to plunge into the atmosphere and die in a handful of seconds and he wouldn't have enough thrust to pull out of it in the end. By picking up speed, the theory goes, the aerodynamic forces of the craft itself could be used to change your trajectory more quickly, resulting in the "bounce" effect where you skip off the atmosphere.

Aerodynamics is key here: a flat rock can be skipped on the surface of a pond relatively easily; a more rounded rock would have to be thrown at MUCH higher speed to get the same effect. Jake had to pick up some speed so that he could use the belly of the shuttle as a surfboard and ride the pressure wave back up to a higher altitude (when he pulled his nose up at the right time) so he hit atmo in a belly flop instead of a swan dive.

 

[Silvercrest]

I see. That's the first time that scene ever made sense to me. Mostly.