Flare Sci-Fi Forums: Center of Mass: Very minor quasi-pseudo-gripe

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Posted by Guardian 2000 (Member # 743) on :

Okay, short of whipping out some awe-inspiring Voyager-esque technobabble, can anyone explain how in the world the Akiraprise/Pre-E/E-NX flies at impulse?

I refer you to the shot at http://flare.solareclipse.net/ultimatebb.php?ubb=get_topic&f=7&t=000764 , where one can see that the impulse engines of Enterprise are way below (dorsal of) any conceivable center of mass of the ship.

Granted, this is a minor point . . . the impulse engines of the Enterprise-Prime were up on the saucer, and even with her high-riding nacelles over the saucer, I can't imagine that the center of mass was at the back center of the saucer, unless those big honkin' nacelles were hella heavy.

However, many ships in the TNG universe have managed to find their impulse engines somewhere near the center of mass . . . the Galaxy, Ambassador, Akira, Constellation, Danube, Defiant (maybe), Intrepid (very maybe), New Orleans, Oberth (maybe), Sabre (very maybe), Sovereign, and the Klingon Vor'Cha (and maybe the K't'inga).

Exceptions do exist . . . the Nova, like the Enterprise-Prime, has impulse engines centered between nacelles and the rest of the ship . . . again, okay if the warp drive is hella heavy, but that seems a bit much unless the rest of the ship is made of tin foil. And a few ships are just hopeless (mainly the ones not mentioned, unless I just didn't know where the impulse deck was and couldn't find it by peeking at the Ex Astris Scientia side-views).

How do we account for the fact that the Enterprise-NX should be doing loop-dee-loops or else flying with her nose cocked down?

Just wondering,

Guardian 2000

Posted by Phelps (Member # 713) on :

Well, when in doubt, always make up an explanation using the word "subspace".

Posted by TSN (Member # 31) on :

Forcefields and "vectored exhaust", or whatever it was called.

That's awe-inspiring TNG-esque technobabble, BTW.

Posted by The359 (Member # 37) on :

Correct me if I'm wrong, but doesn't this not matter in the vacuum of space? Whatever direction the thrust is in, the object will go the opposite direction, but it wont "rotate" at all.

The only way the ship actually turns from any direction other then straight forward is through vectored thrust from the impulse engines and the RCS Thrusters.

Posted by TSN (Member # 31) on :

I wouldn't think so. For example, if you were out in space w/ a suit that had a rocket in the back of the helmet, and you activated it, you'd probably spin around "head over heels".

Posted by OnToMars (Member # 621) on :

Yes, that would happen. The closer the thrust is to the center of mass, the less lateral control you need.

There are other possible reasons for impulse being in the saucer on E-nil (such as space, saucer sep. occasions, etc.) but NX-01's mass is so completley unevenly distributed as to make it thoroughly nonsensical.

Posted by StyroFoam Man (Member # 706) on :

Just another case of WHAT WAS THE ENGINEER SMOKING WHEN HE DESIGNED IT.... Sort of like why did Kirk's Enterprise get ripped to shreads by the Reliant and survive and the E-D took a few hits and blew up... (Answer: The Writers)

Eh, when in doubt... Technobabble.

[ December 01, 2001: Message edited by: StyroFoam Man ]

Posted by CaptainMike (Member # 709) on :

Well, i agree with the Generations situation.

But the Reliant got the Enterprise because
a) the shields were down
b) they 'knew exactly where to hit us'
c) Kirk should have raised the shields, but screwed up.
d) the Reliant wasnt outclassed much by them.. it had more weapons!

The whole point of the movie was that Kirk no longer felt like the guy who saved the day, was no longer invincible, so therefore he screwed up badly by not raising the shields. This was the writers, like you said, but they explained the tech end of it very well with the shields down/precise shot excuse. Besides the Reliant doesnt outclass the 1701 much weaponwise.. its got more torpedoes and woo 'mega-phasers' Dont think that because 1701 was bigger, it was stronger (Starfleet makes 'tough little ships')

Posted by Timo (Member # 245) on :

Perhaps we could stop the NX-01 from cartwheeling by saying that the nacelles of this design have their own impulse engines at the aft ends. Or that the mass of the nacelles is variable, and goes all the way down to zero if needed - after all, subspace fields are supposed to lower the inertial mass, and what else is a warp nacelle but a honking big subspace field generator?

Generally, UFP starships have tended to have their nacelles close to the "thrust plane", so we have been able to assign the nacelles just about any percentage of the ship's total mass. Zero works just fine for most designs. The Constitution configuration is yet another case of this. Unfortunately, it has the secondary hull inconveniently far away from the "thrust plane"... So in fact, it's the one design that creates problems!

Timo Saloniemi

Posted by Cubic Centimeter (Member # 747) on :

Either the exhaust is directed +Y, or maybe there is a ballast mass somewhere in the forward area of the ship. Then again, with things like inertial dampeners, you don't need to have ballast or +Y thrust vectors. You just need to adjust the inertia of the nacelles, or the ship. Pick one.

cm^3

Posted by Guardian 2000 (Member # 743) on :

quote:
Originally posted by Timo:
Perhaps we could stop the NX-01 from cartwheeling by saying that the nacelles of this design have their own impulse engines at the aft ends. Or that the mass of the nacelles is variable, and goes all the way down to zero if needed - after all, subspace fields are supposed to lower the inertial mass, and what else is a warp nacelle but a honking big subspace field generator?

That would, at least, reduce the loop-de-looping . . . nifty idea.

quote:
Generally, UFP starships have tended to have their nacelles close to the "thrust plane", so we have been able to assign the nacelles just about any percentage of the ship's total mass. Zero works just fine for most designs. The Constitution configuration is yet another case of this. Unfortunately, it has the secondary hull inconveniently far away from the "thrust plane"... So in fact, it's the one design that creates problems!
Timo Saloniemi

Well, actually, if one assumes that the Constitution nacelles are heavy as all hell, then the rest of the ship could be of equal mass . . . then it would work out, *roughly*, since the nacelles are above the centerline of the saucer.

G2k

Posted by OnToMars (Member # 621) on :

Either the exhaust is directed +Y, or maybe there is a ballast mass somewhere in the forward area of the ship. Then again, with things like inertial dampeners, you don't need to have ballast or +Y thrust vectors. You just need to adjust the inertia of the nacelles, or the ship.

Unneccessary complexity. Bad engineering.

[ December 04, 2001: Message edited by: OnToMars ]

Posted by The_Tom (Member # 38) on :

Well, blame Probert and Sternbach, because they made those mistakes on the Galaxy and Intrepid.

Posted by Cubic Centimeter (Member # 747) on :

quote:
Originally posted by OnToMars:

Unneccessary complexity. Bad engineering.

I agree. But something has to keep it from going loop the loop. If pressed I would say that they probably just point the impulse nozzels +Y.

cm^3

Posted by OnToMars (Member # 621) on :

How was that mistake made on the Galaxy? Assuming that starships are for the most part balanced so their center of mass lies in the neck (on cruiser configured vessels anyway), then the Galaxy's engines are perfectly placed. The Eng hull's is probably directly on the axis of center of mass and the saucer engines are symmetrical to each other. Like I said, the closer the engine is to the axis of center of mass, the less lateral control it needs. Since both engines are equadistant from the axis, the lateral control each one needs is identical to the other engine. That's good engineering.

As for the Intrepid, I'm forced to agree. The best explanation that I can come up with - one which I don't like - is that the placement of the nacelles in the 'impulse' position allows for better manuevarability during impulse (as opposed to the up, which allows better speed or something at warp). Somehow, this is beneficial for impulse and simultaneously allows for the placement of the impulse engines themselves on the axis of the warp field generation.