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Post by DocD83 on Feb 19, 2008 12:27:22 GMT -5
Well...no. All that mass way out there (and it is way out compared to the nacelles--no other Trek ship is so wide) makes it harder to spin. Anyway, there's probably a limit to how many thrusters you can have.
Same here. Stay strong, brother!
I don't have tech specs for Star Wars vessels (I only consider info revealed in the movies to be cannon, BTW, so...yeah...), but why couldn't an x-wing keep up with a capital ship? Smaller engines, yeah, but smaller vessel too.
[looks at star destroyer] [looks at mon cal ship] I think it's better to say the mon cal ships are the sports sedan to the Destroyer's parking enforcement 3 wheel electric buggy.
Weren't they supposed to have been converted civilian ships? (Yes, I know I'm breaking my rule on cannon.) It may have been all they could do to get shields. Compare to real life vessels--they pressed the Lusitania and other cruiseliners into service carrying ammo, soldiers, and supplies, but they didn't fit 12" artillery to them. A handful were lucky to get a couple hidden 4" guns to fend off u-boats expecting an easy kill.
Am I the only one who likes/remembers the B-wing?
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Post by PoolMan on Feb 19, 2008 12:36:55 GMT -5
Am I the only one who likes/remembers the B-wing? Oh HELLS no! I had the B-Wing toy when I was a kid, and I loved that thing. I'm pretty sure that was a Mon Cal design, too. |
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Rett Mikhal
Ghostbuster
Shorten your stream, I don't want my face burned off!
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Post by Rett Mikhal on Feb 19, 2008 19:04:04 GMT -5
Am I the only one who likes/remembers the B-wing? Oh HELLS no! I had the B-Wing toy when I was a kid, and I loved that thing. I'm pretty sure that was a Mon Cal design, too. It was Admiral Ackbar's design. I liked the B-wing until I actually flew one and realized it just combines the key weaknesses of the Y-wing and X-wing into one easily destroyable package: Slow as a Y-wing but also lacking the super shields and forced to carry only a handful of torpedoes. Well...no. All that mass way out there (and it is way out compared to the nacelles--no other Trek ship is so wide) makes it harder to spin. Anyway, there's probably a limit to how many thrusters you can have. Incorrect. Recall the first and second law of Statics. First Law: Sigma Fx+Fy...=0 Second Law: Sigma M1+M2...=0 Thusly M1 = -M2 Simply put, no matter what size your ship is or how big your engine is, unless you have at least TWO acting opposed to each other, turning is impossible. You may think if you just fire the right side engine you'll spin right, but you won't. You'll just move forward. Unless you fire the left side engine in reverse. Also, once again, mass and bulk are insignificant in space. If you are near a planet, yes, mass becomes important, but bulk still does not matter unless you are IN an atmosphere. Space is devoid of particles that could possibly stop you from moving. So even if your ship was shaped like a giant paper fan, you'd still have no problems maneuvering provided your thrusters worked in conjunction with each other. Although there ARE micro particles in space, they're so small that you'd have to go 20 times the speed of light just to make one Newton of force; equivalent to .224 pounds of force or a 3.5 ounce bag of popcorn falling from a foot above the ground. If anything, the wider saucer section would allow significantly stronger maneuverability if thrusters were placed on the widest sections. The further away the moments are the greater they are. Simple lever principle. A 10,000 Newton thruster placed 1000 meters away from another 10,000 Newton thruster will create 20 million newton-meters of rolling moment. A fully loaded B-17 weighs 250,000 newtons, so, it could create so much force it would cause a B-17 to roll 80 times per second. That's in an atmosphere. In space, it would be nearly infinite AND acceleration would be boosted by a factor of at least 9.81. And before any of you call the police. These aren't Star Trek physics. They're real physics. I read them in a real book. You're absolutely right, but, look at how big a Mon Cal is compared to an A-wing. They can afford space for as big a hyperdrive as then need. A-wings and X-wings have very finite space. One aspect that I'm happy is faithfully kept intact in all flight sim games is the A-wing's habit of crashing or blowing up after one semi-well placed shot because it was so cramped inside the fighter all the important systems were on top of each other. Good design... for ramming Super Star Destroyer's with.... RIP, Green Leader. True but the Mon Calamaris going into battle against the FRAGGIN DEATH STAR AND IMPERIAL NAVY is the same as sending, say, a five year old against the Third Reich's 1st Panzer Division and NOT giving him a super soaker. |
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Post by DocD83 on Feb 20, 2008 21:33:44 GMT -5
You are incorrect. A moment requires a force acting along a line some distance away from a point. (In this case, the point of interest is the center of gravity.) You say you have a statics book--find an example in there. The sum of the moments about a point are zero. To prove this, lay a ladder on the ground, and lift up on its middle rung. It'll lift more or less evenly. Then try lifting it by its top rung.
Or sit in a rolling/swivelling office chair and discharge a fire extinguisher--first hold it by your chest and fire forward, then at arm's length to your side and fire in the same direction.
Also not true. The only thing not being in an atmosphere saves you is having to concern yourself with aerodynamics. As far as mass goes, mass is a constant regardless of the gravitational field you're in (it is weight that changes, according to Newton's second law F=ma). With regards to thrust, the key is momentum--which is all masses and velocities, and therefore independent of gravity.
Spin rates are a dynamics problem, but you're treating it as a statics one. Yes the forces are greater, but it has more to do if the mass is spread out.
To illustrate the effects of spreading a mass out, sit in an office chair with your arms out and have someone start you spinning. As you draw your arms in, you spin faster.
I still don't see your point. Look how big a carrier is compared to an F-14. Are you saying a carrier can go mach 2? Granted their top speed is classified....
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Post by Hucklebubba on Feb 20, 2008 22:30:19 GMT -5
Am I the only one who likes/remembers the B-wing? My obsessive/compulsive need for symmetry makes me like the B-wing in combat mode, but feel unnerved by it in transit mode. It's the same thing that still bugs me about the Falcon; having the control center way out to one side of the ship's mass. The thing that most impresses me about the B-wing in the X-wing series of games for the PC ([snob]A much more canon-accurate representation of capabilities than the Rogue Squadron console games[/snob]) is the obscene hammering it can take. In a game where both the X-wing and A-wing essentially become flying powder kegs once their shields drop, and even the sturdy Y-wing can generally only take two or three hull strikes before going tits-up, the B-wing stands out as a veritable laser-masochist. No shields? No problem! |
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Rett Mikhal
Ghostbuster
Shorten your stream, I don't want my face burned off!
Posts: 377
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Post by Rett Mikhal on Feb 21, 2008 21:42:05 GMT -5
Am I the only one who likes/remembers the B-wing? My obsessive/compulsive need for symmetry makes me like the B-wing in combat mode, but feel unnerved by it in transit mode. It's the same thing that still bugs me about the Falcon; having the control center way out to one side of the ship's mass. The thing that most impresses me about the B-wing in the X-wing series of games for the PC ([snob]A much more canon-accurate representation of capabilities than the Rogue Squadron console games[/snob]) is the obscene hammering it can take. In a game where both the X-wing and A-wing essentially become flying powder kegs once their shields drop, and even the sturdy Y-wing can generally only take two or three hull strikes before going tits-up, the B-wing stands out as a veritable laser-masochist. No shields? No problem! It isn't even very aerodynamically feasable when the S-foils are closed. It's a flying wing, yeah , but one wing is longer than the other. You'd think that thing would spin out of control like hell. Also the heavy gyroscoping cockpit is on the ass end of the small wing, and so is the engine, AND, just to celebrate its unaerodynamics, the vertical stabilizers FOLD DOWN. Secondly, it doesn't make sense it is so heavily armored. Look at it. It's a flying wing. A thin wing. What sense does that make? The Y-wing and X-wing look like they have an armor/component stoich of 100. You are incorrect. A moment requires a force acting along a line some distance away from a point. (In this case, the point of interest is the center of gravity.) You say you have a statics book--find an example in there. The sum of the moments about a point are zero. To prove this, lay a ladder on the ground, and lift up on its middle rung. It'll lift more or less evenly. Then try lifting it by its top rung. Or sit in a rolling/swivelling office chair and discharge a fire extinguisher--first hold it by your chest and fire forward, then at arm's length to your side and fire in the same direction. Yes, I am very aware how moments work. What they say about being in line is a lie, however; moments can be three dimensional with a vector quantity on the i, j, and k components. That's not what I was arguing. What I was arguing was that even if you had a ship a mile long and only an engine on one side, the damn thing wouldn't turn. The one engine would only make one force, in one direction. Take a look at the RCS on the space shuttle or Apollo shuttles. They're covered in thrusters on every side and have one gigantic main engine for controlled speed burns. Think of it like this. Imagine you're underwater and you have a portable propeller. If you keep it at one one angle, 270 degrees with respect to you (thus pointing back) it wouldn't matter where you positioned it within reason; you'd always go forward and not to the left or right or up or down. If you attached it to thin pole 20 meters long, yeah, I can see that your drag through the water would make you EVENTUALLY turn left. But that's my next point. "If the force is greater than the resistance, motion will result...." Space offers practically no resistance. Resistance is friction, and defined as the force of two surfaces in contact. Since space only contains only minimal PPM of dust or fine particles it offers negligible amounts of resistance to movement. Recall the experiment carried out by Apollo 15 on the moon's surface, which lacks any atmosphere. A hammer and a feather with the same amount of force (in this case, the moon's gravity, which could easily just be thrust) move at the same speed, despite the feather having significantly less mass. Since space itself has almost no mass it makes almost no resistance no matter how big or oddly shaped your ship is. That's due to changing your moment of inertia. It's the same as trying to spin an unboiled egg vs a boiled one. Since the boiled egg is a rigid system it spins constantly while the liquid egg changes constantly and cannot spin well. Moment of inertia is measured in kg/m^2. Kinetic Rotational Energy, T, when simplified from integration, is defined as T = 1/2*I*w^2, where I is the moment of inertia and w is angular velocity in radians per second. Theoretically, we're both right. As per the formula, you're right; you need more energy to spin something that has more distributed mass than concentrated. However, as previously stated, space has no resistance. This would mean any amount of force is significant because none is lost to friction. Ah, I see, you're comparing the size of a hyperdrive to the size of a propulsion engine. I can see that. There's no real evidence to prove you wrong. You're saying as the ships get bigger it takes so much energy (E=MC^2) to move them that it's all proportionally close. This would explain how the Falcon is so fast - a combination of good hyperdrive and small size. Since hyperdrive is all technobabble there's no real right answer but your analogy makes a lot of sense. Also, I just want to comment this is one of the longest and most intelligent argument I've had in a long time and I've been in college for three years. Don't. Trust. College. Kids. THEY'RE ALL RETARDED. |
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Post by Hucklebubba on Feb 21, 2008 22:43:05 GMT -5
Secondly, it doesn't make sense it is so heavily armored. Look at it. It's a flying wing. A thin wing. What sense does that make? Perfect sense, in the context of fictional physics. I'm thinking specifically of Finestein's First Law of Attribute Balance, which, in paraphrase, states that big things are tough and slow and small things are fast and weak. In other words, the B-wing doesn't get high marks for resiliency because it employs a top-of-the-line shield generator and experimental alloy hull plating, but rather, because it's about half-again as massive as the appropriately second-most durable and not-quite-as-slow Y-wing. Its size also allows for a complete exemption of its pronounced winginess and resultant probable frailty in a real-life setting. For another illustration; the A-wing isn't fast and maneuverable because it has a powerful propulsion system and a highly efficient vernier suite, the A-wing is fast and maneuverable because it's frightfully fragile, features a mediocre weapons loadout, and, perhaps most importantly, is the size of a Geo Metro. |
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Post by DocD83 on Feb 22, 2008 16:23:49 GMT -5
Good, because nothing I said precludes the vectors being 3-D. One force, yes, but unless it is in line with the center of gravity it'll cause the sum of the moments to be > 0, introducing an angular acceleration. There's a very good example in my dynamics book (Meriam and Kraige Dynamics fifth edition, page 273): a frame with 3 radial arms of length r with masses on the ends is subjected to a force F in the x-direction, b disance along the arm which lies in the y-direction. It ignores all other forces (gravitational and aerodyamic), so it applies to this discussion. The problem is solved in two steps: Step 1, F = ma, resulting in a linear acceleration F/(3*m). This is what you're thinking about. Step 2, sum of moments about the center of gravity = the change in angular momentum. The sum of moments is just F*b. The right hand side takes more work, but in the end you get a nonzero angular acceleration: (F*b)/(3*m*r^2). Interesting that you should bring up marine thrusters.... Anyway, this is demonstrably untrue. Many ships have bow thrusters, which is nothing but a transverse thruster on the bow. There is only one and it turns ships nicely. Other ships have their props mounted on rotating pods (Azipods, I believe is a brand name for it), which either work solo or in groups, but the groups are often pointed in the same direction and on the same end. I've seen single-person subs operate with vectored thrust ( here's one--you'll notice fixed fins, which are there to prevent the sub from turning too fast). They actually make handheld propellers to pull scuba divers through the water much as you described, and they are essentially vectored thrust. Yeah, look at Appollo 13. Remember how they lost power so that their RCS wasn't working, and mission control told them to stop dumping urine overboard because it was affecting their trajectory? I doubt they had two vents working together with that particular system. You're contradicting yourself. If atmophere is required for motion, then the falling motion of the hammer and feather would be impossible. Incidentally, the hammer and feather don't have the same force. They have the same acceleration, provided by the gravitational pull of (in this case) the moon. I was comparing energy density. Generally anything of the same technology has a similar power density unless one is really outdated. Many ships actually have jet engines ("gas turbine"--US destroyers, I think, have them), but the ship is just so massive there's no way to cram enough engines on there to compete with a fighter's power to weight ratio. Or, if there is, there woudn't be room for much else. If you don't mind my asking, what and where are you studying? |
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Post by DocD83 on Feb 23, 2008 8:09:07 GMT -5
I forgot this bit: You may find this interesting. |
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Rett Mikhal
Ghostbuster
Shorten your stream, I don't want my face burned off!
Posts: 377
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Post by Rett Mikhal on Feb 23, 2008 10:21:37 GMT -5
I forgot this bit: You may find this interesting. ( SHRIEKS.) Good golly miss molly! Two different size wings?! Two different size engines?! Asymmetrical construction?! That's a mass-production NIGHTMARE. Though reading the article, the fact it can run on one engine and doesn't pitch or yaw randomly is very impressive. I'm pretty sure the P-38 Lightning could run on one engine but most civilian twin props are just underpowered and crashing is almost assured. Which is a shame, because I've always been a fan of twin propulsion (like the F-14, 15, 22) and not of singular (F-16) because of the fact doubling up the systems gives a good amount of emergency redundancy. Yeah, you could argue it's twice as much to go wrong, but if one thing goes wrong in one engine it's not going to affect its brother. The P-51 with its turbocharged engine could be taken out as soon as one fuel line (the coolant line) was hit by a single bullet and good luck flying then. P-51 is still a marvelous plane besides that, but I'm babbling as always. Uh oh.... two engineers.... this is not good. This is never good.  I haven't taken a dynamics course yet (except Thermo) so I'll have to take your word as correct when it comes to this overblown star trek debate. No no, see this is why two engineers are bad. We're not understanding each other. A bow thruster usually works on an angle 0 with respect to X as opposed to the main propulsion's 270. They can make a very large moment and dynamic movement without the need for forward displacement or two engines working in reverse of one another. Also, you're right, the swivel props are called Azipods and I think they're by far the way of the future. In my stories all the non-atmospheric ships use azipods and the few Navy ships as well. I like to take what I see on the history/discovery channel and kick it up a notch. BAM. That was because of the same reason the bow thruster works. If you hold a pencil in your fingers, is it easier to turn it by rolling your fingers along the long side so it rotates or simply push the eraser side in the direction you want. Because the vents on the Odyssey were not in tandem with the engine they were using, it caused a push in whatever direction they dumped it. If they were using their engine while dumping urine (which is an amusing thought... like how the damn bus/plane always turns when YOU'RE in the bathroom), it probably would have made them spin slightly which would be bad considering they only had a few engines to spare after the explosion. I didn't say an atmosphere is required for motion, I said it makes resistance to motion. That's the basis of the whole argument. I'm basically saying since space offers negligible amounts of resistance to the point shapes and aerodynamics don't matter. Also, I said the force of the moon's gravity could easily just be the same as a thruster going in the other direction. The experiment proves if you stuck a 1000 newton thruster on an F-14 in space and a carrier in space they'd both win the... contest of forward displacement. Didn't want to make a bad rhyme there. |
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Post by PoolMan on Feb 23, 2008 12:10:18 GMT -5
Especially not an Illinois Nazi.
I HATE Illinois Nazis.
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Rett Mikhal
Ghostbuster
Shorten your stream, I don't want my face burned off!
Posts: 377
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Post by Rett Mikhal on Feb 23, 2008 12:52:41 GMT -5
Yes... Boston, Illinois... that's usually the state people think of when they hear Boston. (Other than the digestive track of a large and moving TORG.)
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Post by duckie on Feb 23, 2008 13:51:17 GMT -5
Methinks Poolman just dated himself with that quote... the kids of today don't have the bond to Jake and Elwood as much as the old-timers on this board...
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Post by DocD83 on Feb 23, 2008 14:19:58 GMT -5
Heh, I love that comic strip. I sent someone this one to explain why I missed the eclipse the other night. Given your previous posts, I am now very confused as to what your stance is. Earlier you were saying you needed two engines to turn. Now you're saying the single bow thruster is fine? Edited to add: Oh! Are you saying the bow thruster and the main engines are working in concert? They aren't. Not necessarily. The main usefulness of the bow thruster is when they're in a spot too tight to use the main engines much. Anyway, being in line with the center of gravity, the main engines wouldn't contribute to a moment. Look at that photo I linked--the sub only has one propulsor and no rudder. How does it turn? I don't see your point. In the pencil example, you're comparing rolling the pencil (as f I wanted to see the label) to turning it (as if I wanted it to point to something). Going back to what started this whole thing, I was referring to sluggishness in rolling the Enterprise D. To do so, you probably WOULD use paired thrusters, but you wouldn't HAVE to. As far as pairing with the thruster on the Odyssey, I'm afraid all I can do is point to my dynamics example again. Absent any other complicating factors, an off-center thrust will cause a translation AND a rotation. No companion force is required. We agree, then, aerodynamics don't matter. We disagree, however, about "shapes." By "shapes," I mean mass distribution. If the mass of the Enterprise D was arranged to have very low density at the edges and very high density in the core of the saucer as opposed to being roughly uniform as I assumed, my complaint about it goes out the window (pending further info), outline be damned. You're confusing force with acceleration again. Gravty imparts an acceleration directly, without regards to mass; hence, the two different masses have the same velocity at the same time. The forces are different, however, because F=ma (Newton's Second Law)--if the astronaut had dropped one on his bare foot, the hammer might have hurt while the feather would have been hardly noticed. Conversely a thruster imparts a force directly, and the acceleration has to be computed from that--F=ma rearranges to a=F/m. From this it is clear that, with constant force, acceleration decreases as mass increases. That's not to say you can't build up both to the same velocity, of course, it would just take longer. (They had recruitment ads for bus drivers at my college--"0 to 60 In Under 30 Minutes.") Think about it this way--if mass was irrelevant, why would NASA have those 3 giant main engines on the shuttle? Surely they could install the engines off the smallest sattelite and save all that weight, complexity, fuel, and cost. [irrelevancy] Have you heard of this new book called Liberal Fascism? [/irrelevancy] I'm 24 and I got it. I suddenly feel geezerly. Thanks, Duckie. |
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Post by duckie on Feb 23, 2008 14:32:35 GMT -5
I'm 24 and I got it. I suddenly feel geezerly. Thanks, Duckie. If it's any consolation, I'm pushing 40... can clearly remember when the original Blues Brothers came out in 1980. |
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