Lit GAVs Junkie Base- The technical discussions of the GFFA (Armored Cavalry thread)

I think that the original idea was for them to be more fit for a police role than the more militarised AT-ST. This seems to go in line with the "Defense Pod" designation, their role in the first season of Rebels and the very little informations given in the recent Rebel Files book: "police patrols in the Rim worlds often incorporated AT-DPs".
My guess is that the production team did not think creating a model for a similar walker in the later seasons was worth the money, and the AT-DP ended up being used in scenarios such as the battle of Atollon or the assault of Agamar (although it is worth noting that the Arc Cannon walker uses AT-ST legs). The same had happened with the Lambda shuttle, which role was fit by the Sentinel-class landing craft until a model was made for the 4th season, or with the biker scouts that originally were just combat drivers.
As much as I love the series' many little EU nods (dark troopers, Brah'Tok gunships, hammerheads, Dreadnaughts..) most of them had a very brief appearence, and I think making models for the more iconic and common vehicles should have been prioritised.

 

While you are correct that typically you want to be under 500 ft AGL to evade enemy ground radar detection, since Desert Storm this tactic has been less effective and not practiced as much. Interdiction aircraft that used this technique such as the A-6 Intruder and the F-111 Aardvark have been retired. Their replacements such as the F/A-18 Super Hornet and the F-15E Strike Eagle tend to perform mid to high altitude strikes with precision guided weapons in the interdiction role - this keeps them high enough to avoid danger from low and mid level threat air defenses.

Close air support (CAS) can be performed from high altitude as well, but is more commonly closer to the deck, but much higher than 500 ft. If you were limited to 500 ft altitude you would have a VERY short window to fire when you nosed down the speeder/aircraft before you had to pull up. I would say CAS is reasonably performed in the 500-5000 feet range, with the aircraft gaining altitude, turning, aiming, firing, and turning away from the ground and the the enemy. They call this "popping".

Could the T-47 perform CAS more like a helicopter (ie. standing still) sure, but it would be a much easier target in this fashion. Maybe the T-47 is designed and utilized by the Rebellion as an anti-armour platform more than a CAS platform, we certainty see this during the Battle of Hoth. I have no problem with certain speeders having altitude restrictions resulting from manufacturer design, mission profiles, or available power.

 

Gotcha - I was looking at the topside flaps, and had missed the underside flaps completely. Cheerfully conceding your point here.

... until I start to think about how a downward-turning flap at the rear of the hull would actually work. My (limited) understanding is that rear elevators should nose-down a vehicle in flight, but the T-47s appear to simply drop vertically. So are they designed not to actually adjust altitude, but to keep the nose from tilting up (I'm now wondering if the descent, by increasing the density of air under the airframe, should increase the lift, and thus angle-of-attack?), and possibly also as dive-brakes to cancel out some acceleration force gained in the descent (we do not, of course, know the details of how repulsors work)...?

I ask because I don't really have much confidence in my own ability to figure out the aerodynamics, especially as repulsorlifts are sci-fi tech. But I'm curious about what flight characteristics we'd expect to see on aerodynamic grounds. Perhaps what you say works just fine, but I'm interested to know the details of what we'd expect to see.

The fact that the terrain as seen to the left in a cockpit shot falls away doesn't mean that the terrain beneath the T-47 falls away. That was my thinking, anyway. I did catch that part.

A STAR WARS spacecraft almost certainly uses repulsors to get into space - going far higher, and far faster, with far less aerodynamic lift, than any airspeeder...

@Long Snoot - I apparently have nothing to add, but I wanted to just nod so you know I hadn't missed your post. I think you're right about the AT-DP being designed for a different role - I'm reminded of the ridiculous number of different bodyworks that the British Army put on the Humber Snipe sports car in '39-'45 (or, with less options that include actual armour and guns, the difference between the Nazis' basic khaki off-road VW Beetles and the specialised amphibious soft-top version)...

Thanks for the informed answer.

I definitely think that the T-47's mission profile involves using those unguided cannons over cockpit sights - and anti-armour being a major part of that - with external telemetry not always guaranteed - so basically "running fire" from a helicopter in modern terminology (can T-47s hover? Presumably, but they'd be sitting targets if they did at Hoth); as I'd said a few posts earlier, I tend to think of the GFFA (and especially the Rebellion) as a scenario with no GPS-guidance, heavy jamming, especially of targeting systems, and opposing fighters with fire support from orbital space battleships contesting the higher altitudes, so I'd imagine that this "helicopter tactic" gains in significance (coupled with the sci-fi advantage of repulsor making flying vehicles less vulnerable to flak than things with wings or blades) - though I'd suppose the existence of a separate type for the high-level stuff is entirely credible.

Um, X-wings...?

You are, of course, entirely entitled to disagree, and welcome to point out anything I'm being inept about.

- The Imperial Ewok

 

Eh, in the shot I mentioned, specifically 0:50 to 0:54, there seems to be a ridge coming up right underneath the speeder, since it keeps a level flight throughout the shot without reacting to the ground. Also, there's this shot earlier where four speeders quite clearly pass over another ridge, one drops down and the others stay the same level or increase their height over the same plain: https://i.imgur.com/MzaYNHY.png

 

The point I'm making is that the "dip" between the two ridges is only really seen off to the left from the cockpit - the ground beneath the speeder could be much more level, with only a slight (visible) rise in altitude at the end to cross the ridge.

There's no problem with a T-47 initiating a climb, as the two on either flank of Rogue Two do (no-one is saying they're at maximum altitude here), or with turning left to avoid the dip and maintain level flight (as the one at the rear does, before initiating a slight climb). What I'm arguing is that, either as a function of the way repulsors work or a feature of the standard "cruise" setting, the T-47 normally keeps a level altitude above the terrain, following over the dips. This seems to me to be compatible with what we see in the movie.

- The Imperial Ewok

 

Oh I see what you mean now. A minimum distance from ground setting, like a system that stops you from crashing into the ground in arcade flying video games. It is possible that Rogue 2 uses something like this. I would like to think that this isn't a function of the repulsorlifts alone though, but instead the repulsor lifts being told by a terrain following computer system to work in combination with the aerodynamic surfaces to automatically avoid hitting the ground.

 

I've finally got my hands on the "Dawn of Rebellion" RPG Sourcebook and it openly confirms my impression that AT-DP is meant for urban patrol:
"cousin to the Imperial Army's new AT-ST, the AT-DP was designed primarily for policing instead of frontline combat. Unlike the boxy AT-ST, the AT-DP has a long, more rounded hull witha narrow cross section that allows it to move easily trough dense urban environements."

 

It does that after the four pass over the ridge and only the first speeder does any kind of dip into the plateau.

Nothing of the sort is seen in the actual Battle of Hoth, where the speeders are flying both high and low on the plain against the AT-ATs.

 

You wouldn't need a computer, just a simple altitude sensor (radar, sonar, lidar, or whatever) connected mechanically to the repulsor. The tactical usefulness is pretty obvious.

That said, the question of how repulsorlifts "work" is one we don't know enough about for me to comfortably rule out some effect relating to height-above surface - we know that the powerful repulsors of the Falcon can easily "purchase" on objects as small as asteroids...

I can't shake the thought that the AT-ST, with multiple weapons systems of moderate size, fought on-screen with the blast shields raised and the commander looking out the open hatch, has a primary reconaissance/anti-personnel role, whereas the AT-DP has a more enclosed cockpit with a single heavy blaster that can be aimed independently of the turret rotation by the dedicated gunner, trading versatility for arc-of-fire and powerful punch. That to me looks like a more dedicated anti-armour weapon, which at first sight seems odd for a "policing" vehicle.

I'm guessing that the "policing" role may actually involve the need to level buildings being used as Rebel outposts and fight at least improvised armoured opposition without additional artillery support, rather than the more conventional "light cavalry" role which is performed by the AT-ST - patrol, screening heavy units, and running down exposed infantry and retreating opposition, while relying on AT-ATs for the heavy-combat punch against opposing armour. If I was fighting anything armoured with one of these, I'd want an AT-DP for sure.

And conversely, the AT-DP is not given grenades and autofire, which the crew might otherwise be panicked into using against crowds...

Yes, but only the first speeder continues on a course into the dip - the second and third initiate a sharp climb towards higher ground, the one at the rear turns left to avoid the dip and then climbs slightly before heading off-screen.

All I'm really saying is that the shots of the T-47s in ESB are consistent with a system where the standard "level flight" setting over dips and ridges follows those dips and ridges more-or-less automatically, either as a result of a simple "autopilot" setting, or as a direct result of the way repulsors work.

Elsewhere in the movie, we see T-47s climbing for extra altitude, or flying flat-out over a surface that does not have dips and ridges - which are different scenarios that do not contradict that posit.

That's because, as you say, they're on a plain, without the sort of variations that we see Rogue Two navigating earlier in the movie.

To be clear, the unquestioned ability of the T-47 to climb to varying altitudes has nothing to do with the idea that, once leveled out at a certain height above the surface, they tend to "follow the contour" without direct input from the pilot.

The reasons why they "follow-the-contour" may, however, have some relevance to the original question of their maximum practical altitude (as I said, I'm fine with the listed limit of 175m above whatever surface they're on, either due to the way repulsor tech works, or mechanical limiters).

- The Imperial Ewok

 

My original point though was that is only a thing because of -now legends- video games. At no point in TESB do we see a snowspeeder stalling at 175m from the ground, and for a craft that does create lift through aerodynamics, that maximum altitude is ridiculous as 175m is basically the same as sea level in air density.
I'm saying a gameplay limitation in a video game doesn't have to be translated into a canon technical limitation that makes no sense. I mean the Battlefield games have modern fighter aircraft that can't climb higher than a certain very low altitude, and that doesn't need to be explained in that universe. In my opinion the snowspeeder is an attack aircraft far more advanced than ours today, so it shouldn't perform significantly worse.

 

Which game, though? Maybe I missed where this was discussed, but I'm not aware of what the evidence for your statement is...

As to the practicalities, what makes you think aerodynamic lift is significant to the snowspeeder's performance - the thing is primarily powered by sci-fi hover-tech, and while that youtube video you shared of a flying model version of the T-47 is immensely cool, what we see there - essentially a twin-prop styrofoam drone - has neither the same power/weight ratio nor the same aerodynamic profile as the "real" thing...

I've explained above why I think 175m is a valid performance ceiling that might be mechanically-limited, or else designed-in in terms of repulsor performance. I see the T-47 as basically the Rebel equivalent of a helicopter or even a wheeled scout car - they already have a vehicle for the role you're discussing, namely the X-wing...

- The Imperial Ewok

 

Almost every star wars game with a Hoth level, which is quite a few.

But surely it is similar. Repulsorlift engines negate the effect of gravity, making the craft effectively very light and thus not requiring large engines to create forward thrust.

Gravity is the same at sea level as it is at 175m, so if the snowspeeder can lift of the floor off the hanger floor, then it can rise above 175m. Really the only thing that should stop the snowspeeder from slowly rising right up into space should be a lack of life support. Without a pressurised cockpit or oxygen masks, the snowspeeder would be realistically limited to below 15,000 ft, a reasonable altitude for a ground attack aircraft I think. Also remember civilian speeders on Coruscant in the PT, quite happily traveling along in airlanes thousands of feet above ground.

 

Or the cloud cars of the same film, though for both them and the Coruscant speeders, they might have bigger repulsorlift engines than the T-47. Then again, a generation before, we had space-capable micro-fighters like the Actis, which is as minimal as you can get in terms of engine volume.

 

Couple of thoughts:

-The follow the contour may be an autopilot mode available on the T-47, this mode would be ideal for search and rescue.
-I agree that the lift generated by a styrofoam T-47 does not mean that a real-world durasteel T-47 could generate enough lift to fly.
-I'm curious about the effectiveness of starfighters within a planetary atmosphere. The seem limited to about Mach 1.2. They would however have more maneuverability with repulsorlift engines, and more flexibility with operating at various altitudes (altitude/orbit) vs planes.
-We've seen that speeders can operate at high altitudes (cloud car, AOTC), and the X-34 is limited to 1 meter of altitude. So I think a speeders can have a maximum altitude of anywhere in between, depending on their design: power, engines, and even aerodynamics.
-It's quite possible the cold weather modifications made to the Hoth T-47s limited their original maximum altitude.

 

Yes, but this doesn't necessarily mean that the that the T-47 has a "ceiling" originated in the games (yes, this sort of thing is a regular feature of game mechanics, but simultaneously, the idea that speeders have a relatively low "ceiling" is quite widespread in pre-reboot material for vehicles that have never appeared in games).

Do you know if any of the games specifically limit the T-47 to 175m, out of interest?

You may be right here (and part of the reason I'm asking is that I don't want to waste time on this puzzle if there is an easy answer like Shadows of the Empire)... but I hope you can see why I feel like we don't yet have a definitive answer?

No, the repulsor actively lift the vehicle (obvious examples of "stationary hover" include Luke's landspeeder being pulled over by the stormtrooper checkpoint at Mos Eisley, and the Droid Army's repulsor armour halting to fight the Gungans at Naboo) - "lift" is provided by the repulsors, the thrusters then move the vehicle forward, and any aerodynamic effect is only a secondary effect of forward thrust (and may in fact need to be countered by the steering system).

As I said already, the limit is quite possibly a "programmed" restriction (keep below radar, avoid getting in the way of X-wing patrols, use power efficiently). The apparent "follow-the-contour" movements may also be dictated by something other than the basics of repulsor performance.

That said, we don't know enough about how the sci-fi tech of repulsors is suposed work to know how they respond to a slope. Possibly proximity is relevant to them in some way.

The speeder chase in Ep.II does seem to be quite high-altitude (anyone ever estimated this?), but the vehicles involved may have very different power/weight and range paramenters and the "lanes" may also be assisted by some kind of fixed ground tech. The higher lanes we see more distantly may largely be used by large pressurised "trams" and actual spaceships, too.

The Eta-2 is actually an incredibly minimal vehicle in every sense, compared with the bulky, armoured T-47, and may, therefore, be using a much more powerful type of propulsion that uses a much higher proportion of hull weight and volume (but with only "minimal repulsorlift projectors for take-off and landing" per the ICS, does the Eta-2 have the same endurance and combat usefulness at 175m as the T-47 does? Possibly not...)

I don't think I disagree with any of what you said (which isn't the same as saying you agree with everything I said, mind you).

Maybe you explained your position better than I did mine, though.

- The Imperial Ewok

 

I had never considered this, but I think you're right. I'm just thinking about the three aft facing turbines on the X-34.

BUT...Wookiepedia (canon) states: Repulsorlift was a technology that allowed a craft to hover or even fly over a planet's surface by pushing against its gravity, producing thrust.[1]. [1] is Star Wars: The Force Awakens: Incredible Cross-Sections.

 

Yes repulsor lift engines create "lift" by using gravity, (or antigravity as it is going up not down). Gravity is just acceleration. So if a craft had a repulsorlift engine creating 1G of lift, the craft would appear to be weightless when level with the pull of gravity. Hovering ground vehicles I think would have to have repulsorlifts that only create a lift acceleration of under 1G (or whatever the planet's gravity is).This would create a very lightweight, large mass craft that could be made to hover just above the ground by blowing air down underneath the craft like a hovercraft. I think you see this kind of action under the Trade federation tanks, grass and air is blown around.

 

Thanks. I think the X-34's turbines are simply the forward-thrust propulsion - they're lightweight (what you want when you're using antigravs), efficient for fast travel, and perhaps to a certain extent look cool as a sales pitch. Also, I always liked the idea that turbines, which we consider to be high-end, high-speed tech, are used in the GFFA for a second-hand car which a teenager maintains in his uncle's garage.

To confirm that repulsorcraft can hover, we also see Rey's twin-turbine speeder-bike "parked" by hovering in TFA (in one scene, there's a small structure flipped-down to rest on the ground, but that's just the cargo frame that she's unloading, and cannot support the vehicle). This is evidently a low-power idle that she can leave the machine in for extended waits.

We don't know how repulsor vehicles use gravity, and there are examples which appear to be actively levitated without using aerodynamic lift or being hovercraft. See Rey's speeder for a very good example of a vehicle that just sits there on repulsors with the thrusters off. Or the X-wings taking off in ANH.

Perhaps this difference in POV is why we've been confusing each other over the T-47?

EDIT: I wrote the rest before I read the reply by @Blackhole E Snoke so I started from the POV that repulsors are "active hover" tech, not mass-minimizing tech that requires a second propulsion system for actual lift... that's a different discussion.

Widening the discussion a bit, beyond the individual replies...

One thing that might be interesting to discuss in this thread is the various power and forward-thrust systems employed by repulsorcraft.

Some of them, such as the X-34 and V-35 speeders on Tatooine, the speeder stolen by Skyguy in Ep.II, and Rey's bike in TFA, have readily-identifiable turbine engines. In Solo, this also seems to be the case with the Corellian speeder and the sidecar swoop, which share the same type of engine unit.

Some repulsorcraft, such as the Cloud Car in ESB and Darth Maul's speeder bike in TPM, have visible thrusters of unknown type, that may or may not be turbines (though in Maul's case this seems less likely, as there is no convenient intake and the propulsion emitters are a row of four tiny glowing green disk-shapes). Enfys Nest's swoop in Solo has no visible intakes, and a trio of thrust greeblies giving off a blue glowing effect, described in diagram sources as "triple-cluster turbothrust engines with ion boost" (or something like that).

Speeder bikes and swoops are often a bit more ambiguous about whether they even have thrusters. The speeder bikes in RotJ may have some sort of thruster, though this is less clear - there's an intake underneath, and details under the flaps at the back which look like thrust exhausts, but the intake may be for a turbo power system and the flap details may be something else. The Tatooine swoop in Ep.II, with an "intake" at the front and an "exhaust pipe" at the back, is another ambiguous example, though the Cross-Sections diagram implies this is a turbine that just looks like a motorbike engine. Dooku's swoop is supposed to have ion-engines, but I can't see any thrusters on the design.

Some vehicles definitely appear to be "pure repulsor" vehicles, using this technology for forward movement as well as levitation - this includes the hangar vehicles on Yavin in ANH and possibly also the Droid Army's MTT and AAT armoured vehicles in TPM, which have no obvious "thrusters" (in the pre-reboot canon, The Essential Guide to Warfare stated that the MTT used diesel motors for power, which was partially a sideways nod to Luke's turbines, and also reflected a desire to suggest that a repulsor is very "everyday" tech by GFFA standards).

This may also be the case for the pod-shaped Ubrikkian 9000 speeder parked outside the cantina in Mos Eisley (the LEGO cantina set identifies this as Greedo's ride, which I find neat and worth mentioning just for amusement value).

Zam Wessel's speeder, however, uses a system called "exodrive", in which force-fields are used to accelerate air across the streamlined bodywork and create thrust.

So, some questions for discussion (which I'm asking just for fun, as a curious fan) - what powers a T-47? Thrusters? Pure repulsors? Or a fancy "exodrive" system in the wings? And is the speeder bike from Jedi really a "repulsor-and-turbine" vehicle, or not...?

- The Imperial Ewok

 

Are environment specific troopers (sand, snow, shore, swamp, etc.) a case of regular stormtroopers equipping themselves for the operational environment, or are these trooper types permanently configured units? Was it chance that sandtroopers were stationed aboard the Devastator? Was it chance that snowtroopers were stationed aboard Death Squadron?

 

If I recall correctly, in the Mon Cala arc in TCW Mace Windu refers to reinforcements being delayed because of the time it would take to outfit a division for underwater combat. To my mind this would suggest that environment-specific gear is doled out to standard troops depending on specific situational requirements. If this is true, that approach may have carried over from the GAR to the Imperial Army. (On the flipside, I could be wrong and he may have been referring to the time it would take to form, equip, and train a new aquatic-specialized division from scratch.)

Extrapolating from this into speculation, it makes sense to me that while units preparing for deployment into a theater of combat would be equipped in advance for that environment, in the Imperial context where multirole Star Destroyers are patrolling the galaxy, their troop complements would be similarly multirole in their equipment and provisions. (Within reason, of course - I doubt even a large vessel like an ISD could carry enough of every possible kind of environment-specific gear for its entire troop complement at all times. But who knows.)

 

Do ISDs carry Dewbacks? The majority of the old Expanded Universe sources stated that the troopers we see on Tatooine represent a local garrison, separate from whatever "detachment" of the troops aboard Devastator was sent down by Praji...

That said, the stormtrooper force aboard a big ship might include a number of small specialised units, who can serve as part of the larger unit in standard urban/spaceshup environments (wearing standard armour), but detach for more specialised missions (complete with dewbacks, extra kit, and dirty armour)... say 50 men per ISD, giving a maximum of around 1,200 per sector, who could be combined into a larger unit for bigger missions?

- The Imperial Ewok

 

I would say no to that. Local garrisons on backwater worlds would have stables for local critters that be used for patrol purposes.

 

That's what always seemed more likely to me - but if you take this to be Praji's "detachment", you have to assume that there are Dewbacks aboard the ISD.

- The Imperial Ewok

 

Or there could be critter riding training as part of their training. Praji's detachment hit the garrison at Mos Eisley to pick the dewbacks then went into the field.

 

And we have art of stormtroopers riding other animals than dewbacks on other planets.