The Practicle aspects of Hover Tank design. Discus not Argue

[Dr. Yo]

Very well thought out, though I don't know why you'd want to make
the effect null in a vacuum. The idea of the effect carryiong over to
physiological effects is very good thinking.

[rallymodeller]

It's just the propulsors that don't work in a vacuum -- nothing to push against. The levitation parts work jut fine. If the tank had to operate in zero pressure, some sort of reaction jet system would be needed.

I'm a big believer in the "nothing for free" idea when it comes to "magic tech". Like the disorientation effect in the Alderson Drive, or how lasguns affect Holtzmann shields in Dune.

[Butters]

I've noticed that most of the designs, started and discussed, are using future tech/SF-ish technologies. If a 'hovertank' uses other technologies, such as ducted fans, air cushions, direct fan lift or rocket power, does it still qualify as a hovertank?

[rallymodeller]

I've noticed that most of the designs, started and discussed, are using future tech/SF-ish technologies. If a 'hovertank' uses other technologies, such as ducted fans, air cushions, direct fan lift or rocket power, does it still qualify as a hovertank?

I've got to ask you one question. Does it hover? DOES IT?

Can't see why not. In the Twilight 2000 Soviet Vehicle Guide there was a small (10 troops) hovercraft armed with a big gun of some sort -- might have been a 125mm Rapira but I can't recall.

[HWR MKII]

I've noticed that most of the designs, started and discussed, are using future tech/SF-ish technologies. If a 'hovertank' uses other technologies, such as ducted fans, air cushions, direct fan lift or rocket power, does it still qualify as a hovertank?

If no part of the vehicle touches the ground while in motion then yes. Many great opportunities here guys. Let the ideas loose.

[Patrik]

Small Tactical Aerial Mobility Platform

I mean really, why could the not make this work?

[Old Wombat]

Small Tactical Aerial Mobility Platform

I mean really, why could the not make this work?

Technology, that's the simple answer;
With computer assisted attitude control the STAMP probably could work now, but;
In the 60's (50's?) with manual controls only? Not a hope in Hades.

Just like the Osprey, for which predecessor ideas were floated in the 50's & 60's but canned because of the lethal instability of the craft in flight. Now, with nano-accurate sensors & sufficiently powerful computer assisted attitude controls, she flies!

However, your next question becomes; "Is it of sufficient benefit to the military to balance the cost of further development?"

Answer; "Probably not."

[Dr. Yo]

Umm, early '70s, Wombat-but I suspect a part of the reason for
the failure of the STAMP was its thirty-mile range. Its the sort of thing
that could be mitigated, but probably not enough to make it tactically
useful. It does seem a little odd that none of the non-helicopter
lifters of the past fifty years have seen any kind of military or
civil success. Every time I see an ambulance craawling down the
shoulder in rush hour traffic, I think what a boon the old Piasecki
airjeep would have been in such circumstances.

[Old Wombat]

Umm, early '70s, Wombat

That'll teach me for ignoring the text merely because I can't read it, huh.

Still, there have been some big techno-leaps since the early-70's, too.

[Wug]

The problem is the inherent inefficiency of keeping something in the air with jet thrust instead of lift.

[Patrik]

Yeah, but it looks like fun and could go places a heli could not.

With a range of 50km it's not quite as bad as say the jet packs of the same era.

[Joseph C. Brown]

Pure thrust flight has been an on-going dream... Like the (vaporware) Phalanx Dragon LHX contender:

http://www.picturetrail.com/sfx/album/view/9335102

I think I have more illustrations of that bird on that Picturetrail page than can be easily found around the Web

[Old Wombat]

Now that looks like it could have had potential!

[publiusr]

Good fighter for the Leif'

[Joseph C. Brown]

I've certainly given that some thought - given the handwavium tech we'd require to make a Leif work, some of it could certainly applied to a stylish fighter.

[Old Wombat]

Bringing this across from rallymodeller's thread on "Navy Hovertanks":-

My take on this;

A "tank" is a land vehicle, once it becomes a seagoing vessel it becomes a "ship" or "boat".

Anti-gravitational devices basically make any such powered vehicle an aircraft.

Air cushion vehicles over water are subject to water displacement, as are other water craft. A tank is a heavy, dense object lacking a sufficient base area to stay afloat. Unless the fans can displace 50/60/70 tonnes, which is 50/60/70 cubic metres of water below the tank it's going to sink. This can, to some extent, be negated by constant high speed motion but this means that the "sea-tank" can neither slow down nor stop, making it next to useless for most maritime roles.

A "repulsor" type lifting device vehicle is, basically, the same as an air cushion (hovercraft/ground effect) vehicle and has a displacement effect.

[rallymodeller]

Bringing this across from rallymodeller's thread on "Navy Hovertanks":-

My take on this;

A "tank" is a land vehicle, once it becomes a seagoing vessel it becomes a "ship" or "boat".

Anti-gravitational devices basically make any such powered vehicle an aircraft.

Air cushion vehicles over water are subject to water displacement, as are other water craft. A tank is a heavy, dense object lacking a sufficient base area to stay afloat. Unless the fans can displace 50/60/70 tonnes, which is 50/60/70 cubic metres of water below the tank it's going to sink. This can, to some extent, be negated by constant high speed motion but this means that the "sea-tank" can neither slow down nor stop, making it next to useless for most maritime roles.

A "repulsor" type lifting device vehicle is, basically, the same as an air cushion (hovercraft/ground effect) vehicle and has a displacement effect.

Thanks for bringing this over here. I really should have done so in the first place.

If it is a repulsor-type vehicle, it has one advantage a standard "displacement"-type vehicle does not: you can alter the shape of the repulsor fields to provide more "virtual displacement area". Call it the "snowshoe"-effect. Spread over a wide enough area, a 70-ton tank would be able to float above the water (albeit maybe not very high). Having the ability to alter the shape/contour of the repulsor fields would come in handy here. Certainly would be an interesting visual: the tank sitting over a "pit" or "crater" of water the shape of the repulsor field...

Here's where I agree with you, Wombat. As I said in the other thread, I'm starting to think of my design more as a WIG-effect vehicle with the repulsors acting in place of the wing- and thrust-provided air cushion. Otherwise (and at low speeds), it's a small boat with a big gun. The main difference between my design and a WIG is that mine is less of an aircraft and more like a well-armored boat (that just happens to be really, really fast). The repulsors allow more mass to be lifted, is all.

Another option for marine repulsor applications is to lower the draft of large ships, like LSTs and so forth. They can't come right out of the water, but they can lift themselves up some to be able to beach themselves and then self-recover when they need to get off said beach -- or if they need to navigate shallow waterways.

Also, as was was mentioned by Dr. Yo in the other thread, it would make submarine control interesting. Being able to have depth control of a submarine without adding or removing water from ballast tanks would make depth control almost instantaneous and very precisely controlled.

[Old Wombat]

That's not a problem, rallymodeller!

Just thought I'd bring these over, too.

LCAC (Landing Craft Air Cushion) can carry a single M1A1 Abarms or a passel of smaller craft.

http://en.wikipedia.org/wiki/Landing_Craft_Air_Cushion

Lightly armored hovercraft were used in Viet Nam as riverine craft

http://www.hoverclubofamerica.org/forum ... wtopic=532

Followed by;

Well?

Is a tank the size of an Abrams sitting on a base roughly the size of a LCAC (about, what, 8 times the base area of the Abrams?) a practical vehicle?

The PACV's massed about 7 tonnes operational with a base area of about 81m^2 [0.086t/m^2], an Abrams (for example) masses over 60 tonnes with a base area of only 29m^2 [2.07t/m^2].

That's a surface pressure 24 times greater than the PACV.

[rallymodeller]

I was just musing over my grav tank design and I realized something:

None of the rules regarding "floating" vehicles apply to any sort of repulsorlift system -- if the author says they don't. After all, any adverse or beneficial effects can be added in or removed by the author as they see fit. Heck, Trek is basically built on this premise -- there's more real science and physics in an episode of Sesame Street than an episode of Star Trek.

As Niven once pointed out: any super-tech item only has to be internally consistent. We don't have FTL travel, yet the "rules" of Warp Drive are well established -- until they need to be changed to fit the story.

So I say the same goes for antigravity. Seeing as how it violates a basic law of physics anyway, have fun with it.

In any event, here are some random musings I had regarding how to get around some of the raised questions about an antigrav vehicle:

1: Cannon Recoil. This one's the biggie. Fire a cannon off in a vehicle that has essentially no ground resistance, and the thing should shoot off in the other direction like an air-hockey puck, right? Not necessarily. What if the recoil is passed down through the field as a scalar effect or at right angles? What say there is a "delay" effect that resists sudden motions? The side effects of this might be interesting to consider as well -- if it is a right-angle effect treat it like the gyroscopic "rule of thumb" and when the cannon is fired the tank slews/yaws to the side. That could also affect the design of the tank and favor turreted designs that can keep the cannon on target.

2: Hills/Slopes/Water. Again with the no ground resistance, one would think that the hypothetical tank would want to slide downhill or follow the terrain to the lowest point. Again, depends on how you want the repulsor system to work. How's this: the system is designed to remain at a set gravitational constant and requires adjustment to change the relationship to that constant. Think of a submarine here, blowing or adding ballast to rise/fall. This would also, as a side-effect, solve the problem of traveling over water as the grav system is not pushing against anything; rather, it is holding something where it is by "latching" onto the local gravitational field itself. It is, in effect, a "gravitational-displacement" system. Also some interesting effects with this, as local gravitational effects might be warped slightly by such a system depending on the size of the vehicle being "lifted", what with the displaced gravity and all.

I'm sure there are other issues, but the point remains. Grav systems just don't have to follow conventional physics at all, if you don't want them to.

[DOMENECH1776]

So I say the same goes for antigravity. Seeing as how it violates a basic law of physics anyway, have fun with it.

I prefer to see it as gravity violating the basic law of physics.
Since we don't float away, we're commiting gravity,
and disobeying the law of antigravity
That makes us all law breakers.
Which means that we're all bad boys.
Chicks dig bad boys.
.......
.......
Where are all the damn chicks?

[Butters]

...as local gravitational effects might be warped slightly by such a system depending on the size of the vehicle being "lifted", what with the displaced gravity and all.

I had an intresting visual: a grav tank moving through a small European town, past a cafe, where the wine in the glasses pushed up against the side of the glass as the tank passed.

[Blappy]

...as local gravitational effects might be warped slightly by such a system depending on the size of the vehicle being "lifted", what with the displaced gravity and all.

I had an intresting visual: a grav tank moving through a small European town, past a cafe, where the wine in the glasses pushed up against the side of the glass as the tank passed.

This conjures up all kinds of neat images.

[Butters]

...as local gravitational effects might be warped slightly by such a system depending on the size of the vehicle being "lifted", what with the displaced gravity and all.

I had an intresting visual: a grav tank moving through a small European town, past a cafe, where the wine in the glasses pushed up against the side of the glass as the tank passed.

This conjures up all kinds of neat images.

Ya know, it does, don't it?

Hmmm. Google search

[Dr. Yo]

I was looking in at ARC and spotted a terriic scratch-built PACV in
1/35. The Aircraft Resource center doesn't seem to allow direct links,
but if you scroll down on the main page you'll come to it.

http://www.aircraftresourcecenter.com/G ... rt/00.shtm

(I fixed it for you Doc. Moderator)