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CRMcNeill
Director of Engineering
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Location: Redding System, California Sector, on the I-5 Hyperspace Route.
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 Posted: Thu Feb 05, 2015 7:18 pm Post subject: The Difference Between Landspeeders and Airspeeders |
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So, this one has always bugged me a little...
WEG has always stated that landspeeders and airspeeders both use repulsorlifts, and the original SW novel stated that repulsorlifts only worked in the presence of existing gravity fields by pushing away from it.
The problem is that, if landspeeders use the same drive system (repulsorlifts) as airspeeders, then landspeeders should be able to hit the same altitudes as airspeeders (in the hundreds or thousands of meters range). And yet, per the RAW, they are all stuck within 1 to 2 meters of the ground, even though their drive system (nominally, at least) has nothing at all to do with the ground, and everything to do with pushing against gravity.
My solution? While both airspeeders and landspeeders use repulsorlifts to provide lift, they use differing drive systems to provide thrust.
In the case of landspeeders, thrust is provided by a tractor field that grips the ground directly underneath the speeder, pulling against the ground in the direction of travel indicated. Because the tractor field is spread evenly across the entire underside of the vehicle (and beyond it in the case of rough-terrain landspeeders), it causes little to no disruption or damage to the surface as it passes.
Airspeeders, on the other hand, do not require contact with the ground at all. Their thrust is derived from a gravitic impeller field that propels the speeder in the indicated direction. The impeller can provide thrust in any direction at relatively low speeds, but high velocities require the additional thrust of a fusion or ion engine.
Thoughts?
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Theodrim
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| Posted: Thu Feb 05, 2015 7:56 pm Post subject: |
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I always just wrote it off that landspeeders being cheaper and smaller (generally speaking), used weaker, bare-bones repulsorlifts just powerful enough to keep the vehicle from making contact with the ground. Just because they both use repulsorlifts doesn't mean they use the same repulsorlifts.
It's like saying "what's the difference between a moped and a Kawasaki Ninja? They both use internal combustion engines." |
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Whill
Dark Lord of the Jedi (Owner/Admin)
Joined: 14 Apr 2008
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Location: Columbus, Ohio, USA, Earth, The Solar System, The Milky Way Galaxy
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| Posted: Thu Feb 05, 2015 7:57 pm Post subject: |
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Landspeeders do seem to remain a consistent distance above the ground as they travel over hills (like the Trade Federation tanks in TPM). I agree that at least some repulsorcraft would have to have some other form of propulsion.
I've thought about this too, but the ones that got me thinking about it were the craft that hovered above but close to the surface of water, as seen in a couple WEG modules. How do the vehicles only hover above the water but can't go higher? Are they based on a planet's sea level? Even that is not always consistent due to tidal forces from a moon or moons.
I can't see tractor beams providing thrust on water speeders because you would think that water would just be pulled back to the ship rather than the skimmer being pulled forward. Actually, I would think tractor beams wouldn't always work with landspeeders either because terrain changes on the ground could cause the tractors to grab onto something loose that is pulled back to the landspeeder instead of pulling the landspeeder forward.
But at the moment I don't have an alternate explanation for how repulsor tech actually works. It's good question!
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CRMcNeill
Director of Engineering
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Location: Redding System, California Sector, on the I-5 Hyperspace Route.
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| Posted: Thu Feb 05, 2015 8:30 pm Post subject: |
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| Theodrim wrote: | | Just because they both use repulsorlifts doesn't mean they use the same repulsorlifts. |
Strictly speaking, there is only one kind of repulsorlift in the SWU, with the restriction that it only works in a gravity well, as it requires a mass to push against.
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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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CRMcNeill
Director of Engineering
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Location: Redding System, California Sector, on the I-5 Hyperspace Route.
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| Posted: Thu Feb 05, 2015 8:47 pm Post subject: |
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| Whill wrote: | | I've thought about this too, but the ones that got me thinking about it were the craft that hovered above but close to the surface of water, as seen in a couple WEG modules. How do the vehicles only hover above the water but can't go higher? Are they based on a planet's sea level? Even that is not always consistent due to tidal forces from a moon or moons. |
My explanation (as part of my original post) is that the tractor field used by landspeeders has a very limited range (2-3 meters) and must remain in close proximity to a surface to function. In case the landspeeder drifts too high, the pilot can reduce power to the repulsorlift system, allowing gravity to have a fraction of its normal effect, and thus pulling the landspeeder back close enough to the ground for the tractor field to take effect. In short, a landspeeder's altitude range is based solely on its clearance over whatever surface is underneath it.
| Quote: | | I can't see tractor beams providing thrust on water speeders because you would think that water would just be pulled back to the ship rather than the skimmer being pulled forward. Actually, I would think tractor beams wouldn't always work with landspeeders either because terrain changes on the ground could cause the tractors to grab onto something loose that is pulled back to the landspeeder instead of pulling the landspeeder forward. |
Actually, the possibility of that would be far less than what you get with modern wheeled vehicles. In a car, all of the forward thrust is generated through the points where the drive wheels touch the ground, usually little more than a square foot of total area. Part of the reason why a four-wheel drive pickup is better suited to difficult or loose terrain is because the distribution of thrust is doubled over that of a two-wheel drive vehicle (four drive wheels instead of two). Indeed, one of the main attractions for tank treads over wheels on armored vehicles is because of both distribution of weight and distribution of thrust (two strips of tread running most of the length of the vehicle, as opposed to four patches of wheel-to-ground contact).
In the case of my concept for landspeeders, rather than focusing the thrust onto a few points of contact under the vehicle, you are distributing evenly across the entire underside. So yes, you could still potentially scratch gravel or throw up some debris (recall the grass rippling under the MTTs in TPM), but that would actually be less likely than it would with a tank or car.
As far as water travel, it would also be feasible. Think of the tractor field like a high-tech paddle wheel (or even like the tread on a snow-mobile) taking up the entire underside of the vehicle, pushing against the surface of the water to create thrust. It would certainly displace water and create a wake behind the vehicle, but it could work. If the vehicle is intended primarily for land operations and ends up on the water, performance restriction would certainly be appropriate, and vice versa. You could even have amphibious repulsorlifts, equally at home either on water or on land.
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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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Joined: 17 Jul 2005
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| Posted: Thu Feb 05, 2015 10:17 pm Post subject: |
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| Theodrim wrote: | I always just wrote it off that landspeeders being cheaper and smaller (generally speaking), used weaker, bare-bones repulsorlifts just powerful enough to keep the vehicle from making contact with the ground. Just because they both use repulsorlifts doesn't mean they use the same repulsorlifts.
It's like saying "what's the difference between a moped and a Kawasaki Ninja? They both use internal combustion engines." |
You also have the issue that Starships also use repulsorlift engines, and its 'safer for the environment for them to use those while in atmosphere rather than sublights..
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CRMcNeill
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| Posted: Thu Feb 05, 2015 11:59 pm Post subject: |
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| garhkal wrote: | | Theodrim wrote: | I always just wrote it off that landspeeders being cheaper and smaller (generally speaking), used weaker, bare-bones repulsorlifts just powerful enough to keep the vehicle from making contact with the ground. Just because they both use repulsorlifts doesn't mean they use the same repulsorlifts.
It's like saying "what's the difference between a moped and a Kawasaki Ninja? They both use internal combustion engines." |
You also have the issue that Starships also use repulsorlift engines, and its 'safer for the environment for them to use those while in atmosphere rather than sublights.. |
Uh, were you replying to him or me?
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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: Fri Feb 06, 2015 4:10 pm Post subject: |
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Both.
So we have low riding speeder bikes and land speeders, high flying air speeders and cloud cars, and starships all using repulsor engines, but all with different flight ceilings.
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CRMcNeill
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Location: Redding System, California Sector, on the I-5 Hyperspace Route.
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| Posted: Fri Feb 06, 2015 4:18 pm Post subject: |
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| garhkal wrote: | Both.
So we have low riding speeder bikes and land speeders, high flying air speeders and cloud cars, and starships all using repulsor engines, but all with different flight ceilings. |
Exactly, but that ties in with my original point them using repulsors for lift, but differing modes of providing thrust. Starships would be like airspeeders writ large.
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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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Theodrim
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| Posted: Fri Feb 06, 2015 10:47 pm Post subject: |
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| crmcneill wrote: | | Strictly speaking, there is only one kind of repulsorlift in the SWU, with the restriction that it only works in a gravity well, as it requires a mass to push against. |
That doesn't mean all repulsorlifts have the same configuration, energy requirements, or power output. That just means all repulsorlifts operate on the same scientific and technological bases.
Compared to reality, there's only one "kind" of internal combustion engine (fuel plus oxidizer combusts in an enclosed chamber, creating heat and pressure which is converted into mechanical energy), but internal combustion engines vary wildly in fuel requirement and power output. Weed eaters and Bugatti Veyrons both use internal combustion engines, but they're nothing alike. |
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CRMcNeill
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| Posted: Fri Feb 06, 2015 11:21 pm Post subject: |
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| Theodrim wrote: | That doesn't mean all repulsorlifts have the same configuration, energy requirements, or power output. That just means all repulsorlifts operate on the same scientific and technological bases.
Compared to reality, there's only one "kind" of internal combustion engine (fuel plus oxidizer combusts in an enclosed chamber, creating heat and pressure which is converted into mechanical energy), but internal combustion engines vary wildly in fuel requirement and power output. Weed eaters and Bugatti Veyrons both use internal combustion engines, but they're nothing alike. |
And just as internal combustion engines all rely on the same basic concept to produce power (fuel-air explosion pushes a piston which causes a shaft to rotate which produces power), so also do all repulsorlifts work on the same principle in the SWU, specifically, that they function only so long as they have a gravity field to push against. There is no mention in the description of pushing against the ground (you have to get into the EU to find anything that hints at that). Therefore, if a vehicle is equipped with repulsorlifts of sufficient power to lift it off the ground (i.e. sufficient to override local gravity), and those repulsorlifts push against the planet's gravity field, not the ground underneath the vehicle, then there is no technological basis for restricting their altitude above ground. Indeed, if power restrictions are an issue, repulsorlifts will require less energy the further above ground they get (gravity's pull becomes less and less as you move further away from the mass causing the gravity well).
So, even though the repulsorlifts on a T-47 Airspeeder vary wildly in power output and fuel requirements from those on a Victory-Class Star Destroyer, they both function on the same principle of repulsorlift; that is, they push against gravity, not the ground.
My alternate theory? If it's a landspeeder, it is not actually a repulsorlift. What it actually uses is a pressor field (a sort of anti-tractor beam, if you will), that pushes against the ground, thus raising the landspeeder up and off the ground. However, based on observable evidence (i.e. that landspeeders continue to hover when not in operation), this theory is less likely than my original.
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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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atgxtg
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| Posted: Sat Feb 07, 2015 9:46 am Post subject: Re: The Difference Between Landspeeders and Airspeeders |
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| crmcneill wrote: |
My solution? While both airspeeders and landspeeders use repulsorlifts to provide lift, they use differing drive systems to provide thrust.
Thoughts? |
It's lift that gives a flying vehicle altitude. Forward thrust is speed. If they both use the same lift system then you are right back in the same boat.
A more feasible solution would be that the landspeeders just don't have as powerful a repulsorlift engine.
Oh, also landspeeders seem to lack wings, while airspeeders seem to have them, suggesting that they are relying on the wings for some of their lift. Maybe the respulsorlift can only negate so much gravity (that would make a lot of sense, otherwise the speeder would drift into space as it and the planet moved in different directions) and the wings provide that extra amount needed to gain altitude. |
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CRMcNeill
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| Posted: Sat Feb 07, 2015 11:02 am Post subject: Re: The Difference Between Landspeeders and Airspeeders |
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| atgxtg wrote: | It's lift that gives a flying vehicle altitude. Forward thrust is speed. If they both use the same lift system then you are right back in the same boat.
A more feasible solution would be that the landspeeders just don't have as powerful a repulsorlift engine. |
Sometimes, I am moved to wonder if people even read my previous posts before replying. I've already answered this at least once.
My point is that, if both landspeeders and airspeeders are repulsorlifts, they derive their lift from pushing against gravity, not the ground underneath them. By definition, repulsorlifts function anywhere, at any altitude, so long as they have a gravity field to push against. A vehicle with sufficient repulsorlifts to make it float .5 meters above the ground will float just as easy at 50 kilometers up, because in either circumstance, the vehicle's repulsorlifts are pushing against gravity, not the surface of the planet.
Your argument that the landspeeder repulsorlifts are weaker is flawed, because, assuming that power requirements increase in direct proportion to the gravity field being countered, that gravity field would actually become infinitesimally less at higher altitudes, simply by virtue of being further away from the mass causing the gravity.
As such, if we wish to continue assuming that landspeeders must stay near the ground while airspeeders do not, even though they utilize the same gravity-neutralizing fields to produce lift, there must be a reason.
My explanation is that, while a landspeeder's repulsorlifts could conceivably allow it to float at any altitude, its thrust system requires close proximity to a solid surface, while an airspeeders does not.
| Quote: | | Oh, also landspeeders seem to lack wings, while airspeeders seem to have them, suggesting that they are relying on the wings for some of their lift. |
I don't know where you are getting the idea that airspeeders have wings. The T-47 and Storm IV from ESB are both airspeeders, and neither of them has a wing or a lifting body type. I don't remember any of the prequels era airspeeders being winged, either.
| Quote: | | Maybe the respulsorlift can only negate so much gravity (that would make a lot of sense, otherwise the speeder would drift into space as it and the planet moved in different directions) and the wings provide that extra amount needed to gain altitude. |
But that doesn't explain how capital ships like the Venator or the Victory can use them to hover effortlessly.
Now, I could believe that a landspeeder's repulsorlifts did not fully support all of its weight, if only as a method to keep it from drifting off into the sky every time a breeze blows by. However, this in turn requires the assumption that there is something else there to keep it from dropping straight to the ground. Such as a tractor field under the vehicle.
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jmanski
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| Posted: Sat Feb 07, 2015 11:48 am Post subject: |
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The explanation that an airspeeder has more power than a landspeeder is not flawed, IMHO. The SR-71 required massive engines to take it to record-breaking altitudes.
My .02: landspeeders are designed to stay close to the ground so they have a small engine (like a car), airspeeders are designed to fly so they have wings and a more powerful engine (like an airplane).
There are cars that are able to add parts and fly. Perhaps there are landspeeders that add parts and fly.
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cynanbloodbane
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| Posted: Sat Feb 07, 2015 12:57 pm Post subject: |
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There is a way of looking at the where you could both be right.
Assuming air & land speeders are propelled by the same technology, aka repulsor-liftsthat provide lift and thrust anywhere in a gravity field, than it could be fair to say that the difference is all in its mode of flight stabilization. Land speeders use low output tractor and repulsor fields that require close proximity to a relatively flat surface, while air speeders have a more complex avionics thrust package designed for 3 dimensional use. In short the ceiling is determined by its stabilization system. The use of low power/range repulsor & tractor fields could also be used to explain the ability to hover even while powered down.
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