Grav vehicle dogfighting tactics?

[PFVA63]

Hi,

A thought came to me last night that, if a grav vehicle may be operating in an atmosphere and that atmosphere is imparting forces on the grav vehicle (such as lift and drag etc), especially when the direction of motion of the grav vehicle is at an angle to the local airstream flow, then it might be worthwhile to make the craft hullform a hybrid design which tries to make use of those external forces.

Specifically since most any relatively streamlined shapes (including flat plates) develop some amount of lift when at an angle to the local flow around them, and any shape moving through the atmosphere will develop drag, then if the shape of the grav vehicle is designed to efficiently generate lift at the speed ranges it is likely to be operating at, in the typical atmospheres that it might likely find itself in, then less of the G's its capable of producing would have to be used to counter the planet's natural gravity and more could likely be applied to providing thrust in the direction that you want the craft to go.

 

[mike wightman]

I'm beginning to think the ideal shape is going to be an ellipsoid.

Isn't this how T4 said grav vehicles would go?

 

[PFVA63]

Hi,

I guess a question that needs to be asked is what velocity are we talking about for these type craft since, if they are moving through an atmosphere they will generate drag that the thrust from the grav drives must counter (since Thrust generated will be equal to the craft mass times its acceleration, or in other words F = ma).

The overall speed that the craft will be able to attain should be a function of its wetted surface area, the atmospheric density and its coefficient of drag (which can vary with speed/speed regime). In general I'd suspect that the best shape for such a craft will likely be dependent on whether it is expected to only operate sub sonically, trans sonically, super sonically, or even hyper sonically.

One additional issue that I think(?) might also come into play is that even if a craft's grav plates can only produce enough thrust to propel the craft up to a given speed in the atmosphere, if it is entering the atmosphere from orbit it can potentially be travelling at a much higher velocity than that and as it de-orbits I believe it will loose speed as the atmosphere gets thicker and drag increases. As such, even if the craft's normal propelled speed in an atmosphere is one value, in a de-orbit it may be higher and if the drag and turbulence generated by the craft as it encounters the increasing density of the atmosphere on its way down it may experience controllability issues, etc.

I suppose potential options for dealing with this issue could be to either try and select a hull shape that has decent drag characteristics over a wide range of potentially encountered speeds in the atmosphere, or to set a maximum not to exceed speed for the craft and then develop de-orbiting methodologies to keep craft speed under these limits, though to be honest I'm not really sure how all that might be done.

Just some thoughts

PF

 

[PFVA63]

I'm beginning to think the ideal shape is going to be an ellipsoid.

Isn't this how T4 said grav vehicles would go?

Hi,

Here's an example of what I think grav vehicles might look similar to.

Its a Japanese Hypersonic test vehicle but it also looks like its well shaped to have a lot of usable internal volume which kind of seems to me could make it both a useful shape for a transport while also being a reasonably streamlined vehicle that could safely transit through a hypersonic speed regime during de-orbit and into a lower subsonic speed regime that it might more typically operate in.

http://www.rocket.jaxa.jp/fstrc/0c02.html

 

[Carlobrand]

HG_B: a disc shape is fine for forward, backward and left and right in the atmosphere, but if it tries to go vertical up or down at those speeds, it will tear itself apart. So it has to take some aerodynamic flight characteristic while in denser part of the atmosphere. In space however, it one mean mother....

Given that we're discussing dogfighting, I don't think the typical Traveller combat vehicle's going to be in much danger of tearing itself apart. They'll be pretty decently armored, and they'll be designed for dogfighting - which is to say they'll be designed to do unlikely things as a means of evading incoming fire and pursuing nimble opponents. Tumble might be a problem, but I don't see them coming apart.

Occurs to me that stability is not necessarily a positive in a dogfighter. You want something nimble, and you've got computers to help you maintain control in the face of instability. A predictable instability can be tapped into to promote a more rapid change in facing. I think what you want is something that gives the minimum possible cross-section to an attacker while being able to use its shape to tap into aerodynamic forces to change bearing and vector rapidly. As Ishmael pointed out, a winged vehicle (or, IMO, any shape designed to take maximum advantage of the air) is going to have a maneuver advantage over a vehicle using solely its drives for maneuver.

Battlestar Galactica (the newer one) did something interesting. I recall one of the webisodes in which a human fighter escorting a Raptor was dueling a Cylon fighter that was after the Raptor - in atmosphere. At points, the two fighters were flying sideways trying to get shots at each other. That was surprising; I figured the human fighter for being dependent on rear thrust for forward motion, but it was able to turn sideways - briefly, at least - while maintaining forward motion.

 

[Almuric]

Why would a grav vehicle dogfight?

(1). At the TL you have grav vehicles, you also have lasers and high energy weapons, both with accurate ranges measured in several km and none of the aiming issues (lead, etc.) you have with a machine gun or cannon. It's probably in a turret mount; unlike a WWII-era machine gun turret, a turret-mount laser or plasma gun should not have the limitations that non-fixed mount weapons have when tracking a maneuvering target at several km away. (You may want to do some dogfighting if you let your foe get to <500 meters, but that's not very likely in a serious fight. Even then, your best bet is probably to stop and rotate the vehicle, much as you would do in space.)

(2) Grav vehicles have no stall speeds and can hover. If someone is on your tail, stop in mid air, turn around, and hose him down. If a missile is fired at you, duck behind a rise or tree, or halt, stabilize, and shoot down the missile.

I would expect grav vehicles to generally fight like attack helicopters, only more so, using terrain for cover; if caught at long range at high altitude, they'll probably evade while swiveling turrets to shoot; energy management is only semi-relevant, because the idea of getting on someone's tail is likely obsolete, and in any event it's impossible for a grav vehicle to stall like an airplane, so you can fight effectively - perhaps even MORE effectively - if you allow your energy (speed, etc.) to drop to near-zero; what matters is not your ability to maintain airspeed, but your ability to zig-zig which is dependent on the g-rating of your thrusters and is equally useful regardless of your vehicle's energy state.

Anyone who tries to dogfight against a combat grav vehicle equipped with energy weapons is going be as dead as someone trying to do a horse cavalry charge against a machine gun.


At high altitudes

 

[Carlobrand]

Why would a grav vehicle dogfight?

(1). At the TL you have grav vehicles, you also have lasers and high energy weapons, both with accurate ranges measured in several km and none of the aiming issues (lead, etc.) you have with a machine gun or cannon. It's probably in a turret mount; unlike a WWII-era machine gun turret, a turret-mount laser or plasma gun should not have the limitations that non-fixed mount weapons have when tracking a maneuvering target at several km away. (You may want to do some dogfighting if you let your foe get to <500 meters, but that's not very likely in a serious fight. Even then, your best bet is probably to stop and rotate the vehicle, much as you would do in space.)

(2) Grav vehicles have no stall speeds and can hover. If someone is on your tail, stop in mid air, turn around, and hose him down. If a missile is fired at you, duck behind a rise or tree, or halt, stabilize, and shoot down the missile.

I would expect grav vehicles to generally fight like attack helicopters, only more so, using terrain for cover; if caught at long range at high altitude, they'll probably evade while swiveling turrets to shoot; energy management is only semi-relevant, because the idea of getting on someone's tail is likely obsolete, and in any event it's impossible for a grav vehicle to stall like an airplane, so you can fight effectively - perhaps even MORE effectively - if you allow your energy (speed, etc.) to drop to near-zero; what matters is not your ability to maintain airspeed, but your ability to zig-zig which is dependent on the g-rating of your thrusters and is equally useful regardless of your vehicle's energy state.

Anyone who tries to dogfight against a combat grav vehicle equipped with energy weapons is going be as dead as someone trying to do a horse cavalry charge against a machine gun.


At high altitudes

Striker rules provide some advantage to high-speed high-agility vehicles. Stopping and hovering is usually a good way to get hit, hard. They also have some variation in armor strength by facing, so obtaining a good angle on someone may give you a chance at an attack through weaker armor - or forcing them to maneuver to avoid your attack could make them expose a weak face to another attacker. They also have sighting rules and terrain rules that a tank can use to reduce engagement ranges, and that make high-altitude a rather dangerous place to be. I think you're right that the classic dogfight maneuvering is unlikely - a grav tank could hypothetically go 180 to present frontal armor to a foe while flying backward, for example. However, some form of maneuver combat is still likely, at least as Striker rules portray it.