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MrNexx
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 Posted: Wed Jun 15, 2016 11:57 am Post subject: Repulsorlifts |
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This is pretty well based off CR's stuff about repulsorlifts in the "Update Existing Vehicle Stats" thread. I'm quoting a couple of his posts here to form a jumping off point, 'cause I have a related idea, and figured moving general discussion of repulsorlifts off his Stats thread might keep it a bit clearer.
| CRMcNeill wrote: | Okay... (deep breath)
You just stumbled into this for the first time, so I'm going to answer, but I'm only going to say this once. The central premise of the functioning of repulsorlifts, as described in the novel for ANH, is this:Repulsorlifts push against an object's gravity field, not the physical object itself. As such, how high a repulsorlift-equipped vehicle can get off the ground is not a function of how much power it needs push further away from the ground, but rather, whether it had enough power to lift the vehicle's entire mass off the ground in the first place (in effect, rendering that mass weightless).
Once the vehicle's weight is negated by the repulsorlift's counter-gravity effect, changing altitude is child's play. Even assuming it takes 80 or 90% of a repulsorlift's power to neutralize the vehicle's full weight, turning it up the extra 10% will actually make the craft buoyant, causing it to move up, away from the ground all on its own, with the only upward limit being the point where the repulsorlifts no longer have sufficient gravity field to push against (an essential requirement, also per the ANH novel), which is about 72,000 kilometers up, or six planetary diameters (again, per the ANH novel).
Based on the above, the idea that an anti-gravity device pushes against the ground just doesn't hold water.
As such, my alternate theory is been that the difference between landspeeders and airspeeders is that, while both use repulsorlifts to produce lift (by neutralizing the vehicle's weight), landspeeders use a drive system that requires them to stay near the ground, while airspeeders do not.
As such, your suggestion of basing landspeeder altitudes on power availability is right, but for the wrong reasons. The power issue is not connected to the repulsorlifts (which demonstrate they have enough power already by the simple expedient of being able to lift the vehicle off the ground in the first place and keep it there), but to the tractor-beam-tech based drive field underneath the vehicle that must grip the ground to push/pull the vehicle forward. The higher up the vehicle goes, the stronger the drive field must be to continue exerting force against something that is further away. |
| CRMcNeill wrote: |
The theory I went with for speeder bikes and swoops was that their mass was so low compared to their total power output that their traction drives were able to maintain grip and forward thrust from much higher off the ground (in the 30-35 meter range).
In effect, power needed (P) would be a function of distance (D) and mass to be moved (M), so P=DxM.
So for something like a Floating Fortress, with a mass of, say, 40, and a D of 2 meters, the power requirement would be 80.
For a speeder bike, with a mass of 1, and a D of 30, the power requirement would be 30.
Airspeeders, on the other hand, would also use a tractor-based drive system, but this would be more of an impeller field, almost like projecting a tractor beam on itself, which could then move the vehicle in any direction (although I'm thinking that positioning in the vehicle would have it's most effective and efficient thrust be forward motion, with reduced speeds for rearward or lateral). This would free the vehicle of proximity to the ground (and would be functionally identical to the repulsorlift systems on starships), but would cost in stability and low level operations. This is because, unlike the traction drive, the impeller drive doesn't have contact with the ground, and can thus be driven into the ground if the pilot isn't careful. |
(CR, if you want me to change the stuff in the initial post some way, let me know; I want this to be a jumping off point in the first post)
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Last edited by MrNexx on Wed Jun 15, 2016 12:16 pm; edited 1 time in total |
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MrNexx
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| Posted: Wed Jun 15, 2016 12:02 pm Post subject: |
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So, here's the thought that led me to create a new post, referencing back to this thread about Tramp Freighters Underwater.
Given that Repulsorlifts work by moving one within a gravity field, the tramp freighter could work just fine underwater on repulsor alone. But then you start thinking about landspeeders, and the question of whether or not they can go over water (which was raised in another thread that I don't care to track down). Given the technology outlined, it should be possible... but what if it's not a simple matter? What if, using the traction drive idea (i.e. the repulsorlift provides lift, but the traction drive grabs onto the surface beneath you to provide acceleration), one has to make on the fly adjustments when traveling over liquids... not impossible, but the kind of thing a manufacturer might block out on their standard model, and so wouldn't be possible without aftermarket modification?
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CRMcNeill
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| Posted: Wed Jun 15, 2016 12:02 pm Post subject: |
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No changes necessary from my POV. Fire away.
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CRMcNeill
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| Posted: Wed Jun 15, 2016 1:44 pm Post subject: |
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Considering the nature of an airtight object to float in water, if the goal is to submerge the ship, it might actually be necessary to invert the repulsorlift, actually augmenting the natural pull of gravity to force a buoyant object below the surface.
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"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.
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garhkal
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| Posted: Sat Jun 18, 2016 11:54 pm Post subject: |
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Good point. A ship could easily have positive buoyancy to keep it afloat for a while..
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CRMcNeill
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| Posted: Sun Jun 19, 2016 6:36 pm Post subject: |
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| MrNexx wrote: | | What if, using the traction drive idea (i.e. the repulsorlift provides lift, but the traction drive grabs onto the surface beneath you to provide acceleration), one has to make on the fly adjustments when traveling over liquids... not impossible, but the kind of thing a manufacturer might block out on their standard model, and so wouldn't be possible without aftermarket modification? |
I'd say that the traction drive is usable over water, but that because it is exerting force on a much more fluid surface than solid ground, it has the effect of reducing speed and creating a noticeable wake. Much like landspeeders, a water-speeder would be relatively slow if using repulsorlifts only, and would need to augment its speed with some sort of booster drive, like the magnetohydrodynamic drive installed on the DeepWater-Class Light Freighter. The effect would be of a repulsorlift vehicle hovering a few inches off the water, with a drive pod extended down into the water itself, like a hydrofoil...
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CRMcNeill
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| Posted: Sun Jun 19, 2016 7:16 pm Post subject: |
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It's also possible that repulsorlifts are integrated into non-repulsorlift vehicles. For instance, a walker could incorporate repulsorlift suspensors to reduce its weight, and thus its ground pressure. Non-drive repulsorlifts could explain several physically impossible vehicles...
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"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.
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Whill
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MrNexx
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| Posted: Wed Jun 22, 2016 11:43 am Post subject: |
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| Whill wrote: | | CRMcNeill wrote: | | Non-drive repulsorlifts could explain several physically impossible vehicles... |
...with a physically impossible technology. Yes, they could very easily.  |
Fantasy and soft science fiction is the art of piling impossibility upon impossibility until you get plausibility. 
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