Atmospheric operation of small craft, incorrect assumptions

[DFW]

As written on pg. 56 High Guard:
"A standard–hull small craft may still enter atmosphere, but is
very ungainly and ponderous, capable of only non–lift generating
powered flight."

This is a VERY strange statement. A vehicle using a gravitic drive to maneuver in the atmosphere has much better options than a craft that requires lifting surfaces to operate. Our Air Force would LOVE to get rid of lifting surface fighters and exchange them for gravitic, non-lifting surface maneuver craft. Also, a cylinder rounded on both end with NO lifting surface would be much more aerodynamic than a craft designed as a lifting body due to induced drag.

The config section of the books needs to be rewritten.

 

[rust]

This is a VERY strange statement. A vehicle using a gravitic drive to maneuver in the atmosphere has much better options than a craft that requires lifting surfaces to operate.

Yes and no, because the lifting surfaces usually are an important part
of the craft's steering system. A gravitic maneuver drive would have to
be able to change the vector of thrust quickly around all three axis of
the craft to give it the same agility that a conventional aircraft with its
lift-plus-control surfaces has.

 

[DFW]

A gravitic maneuver drive would have to
be able to change the vector of thrust quickly around all three axis of
the craft to give it the same agility that a conventional aircraft with its
lift-plus-control surfaces has.

Actually, not even close to being true. A craft using gravitics to stay aloft can
hover and pivot. A craft relying on lifting surfaces is very limited based on its existing speed. Too low of a speed, very bad maneuverability, too fast, same + danger of destroying said lifting surfaces. I take it you aren't a licensed aircraft pilot?

 

[rust]

A craft using gravitics to stay aloft can hover and pivot.

Sure, but this is not what is required to fly a looping or Immelmann turn
or any other remotely complex maneuver.

 

[Sturn]

Actually, not even close to being true. ......... I take it you aren't a licensed aircraft pilot?

:roll:

Let's be civil please. I'm interested what has to be said on this subject, especially from those with knowledge over the matter and thus would prefer this discussion to stay in-flight (bad pun intended).

 

[DFW]

Sure, but this is not what is required to fly a looping or Immelmann turn
or any other remotely complex maneuver.

Correct. However, those maneuvers only exist because a craft that requires lift from the surfaces must maintain forward speed or, fall. Thus those actions you listed are FAR inferior to a gravitic lift system crafts ability. They are "complex" because of the need to maintain lift.

see: http://www.jjraymond.com/books/nonfiction/boyd.html

 

[barnest2]

I completely agree with somebody.
A grav driven craft wouldn't be able to pull fast ma, manoeuvres, because the thrust element is seriously less efficient at turning.

And as for the lack of need for fast/complex manoeuvres they are not just important because of the need for lift. They are needed for fast dogfights, something that isn't going to go away because of gravitics, its all about getting into the best position in relation to your opponent. Also, what about missile evasion, a ship ahs to be able to jink and pull hard, high speed turns, and in atmosphere, surely flight surfaces are essential for this.

No, i'm not a licensed pilot, but my stepdad is, ive flown a couple of times, and i am currently studying military history...

 

[DFW]

Depending on the model/description used the thrusters are highly restricted in their vectoring capablities, basically they provide thrust along one axis and loose efficiency if the ship tries to apply thrust outside of that axis.

Correct. So, instead of applying thrust outside of that axis, you spin to reorient the craft so that the thrust axis aligns with the desired new vector.
MUCH for effective for maneuver than a control surface lifting body craft must employ. It would be beyond silly to do it the other way.

 

[barnest2]

I assume traveller small craft have inertia compensator's of some description, or you would get squished when pulling high g manoeuvres such as those suggested above, yes?

 

[DFW]

I assume traveller small craft have inertia compensator's of some description, or you would get squished when pulling high g manoeuvres such as those suggested above, yes?

They do but, you won't experience more Gs than can be delivered by your thrusters. Unless, you are referring to the lifting body maneuvers...

 

[DFW]

And as for the lack of need for fast/complex manoeuvres they are not just important because of the need for lift. They are needed for fast dogfights,

Actually, incorrect. They only exist because of the need to maintain minimum IAS (indicated air speed) to keep from stalling. Otherwise, they are a total waste of energy and time.

BTW - this is why thrust vectoring on the F-22 & Russians planes is such a BIG deal. See also Falkland air to air battles...

 

[far-trader]

Depending on the model/description used the thrusters are highly restricted in their vectoring capablities, basically they provide thrust along one axis and loose efficiency if the ship tries to apply thrust outside of that axis.

Correct. So, instead of applying thrust outside of that axis, you spin to reorient the craft so that the thrust axis aligns with the desired new vector.

And with what mechanism do you spin your craft to reorient the thrust? (1)

I suggest you look at the rules as stated and take that as the presumed basis of design. Rather than assuming that the rules as stated are wrong because they don't fit your conception of how grav drives work.

Clearly whatever way things work under the rules as written means standard hulls are a disadvantage. This implies that grav drives are not very good for high maneuverability. They provide lift, and generally not enough of that to do more than hover and accelerate or turn slowly. The Air Force would not be interested in anything like that, at least not for combat. Performance poorer than current helicopters with the only advantage being a lack of rotor wash and clearance needs.

I see no need to rewrite the section. You just need to fit your concepts to the way it's written. Or simply change it for your TU to fit your concepts.

(1) I've seen high speed gyroscopes suggested. With crazy revolutions, and high density, you brake against the spin to quickly reorient. The problem being the explosive hazard if the gyroscope is damaged (combat) or fails. I've used small fueled thrusters at times. Generally though it's always been the grav drive itself that does the reorientation, by applying off-axis thrust. So it's slow. Hence grav craft are not good combat craft and do poorly in high winds.

 

[far-trader]

I assume traveller small craft have inertia compensator's of some description, or you would get squished when pulling high g manoeuvres such as those suggested above, yes?

They do but, you won't experience more Gs than can be delivered by your thrusters. Unless, you are referring to the lifting body maneuvers...

I've long preferred my small craft to not have inertial compensation for the game feel. Stating that the small size doesn't permit the required systems. With the limited Gs of Traveller drives they aren't required. Pressure suits are more than adequate for even 6G fighters. In space. Where one is strapped into a proper seat.

Yes, if performing rapid attitude changes, such as airframe atmospheric maneuvers, then you can easily exceed safe Gs imposed. Which DFW is a problem with your concept of quick reorientation of grav drive craft and thrust application on a new axis. That will act the same way as high speed airframe maneuvers so you will need some form of compensation. And you will apply similar stresses to the craft. Stresses it is not designed to take since it is built as a standard hull. Another point suggesting that grav drives in Traveller are not capable of high speed reorientation as you imagine it.

 

[barnest2]

Actually, incorrect. They only exist because of the need to maintain minimum IAS (indicated air speed) to keep from stalling. Otherwise, they are a total waste of energy and time.

BTW - this is why thrust vectoring on the F-22 & Russians planes is such a BIG deal. See also Falkland air to air battles...

So manoeuvring into an advantageous position in a dogfight is a waste of energy in time? like the harriers had to do in the Falklands? Sure, when you add missiles, dogfighting becomes less important, but the small fighter is only armed with a pulse laser... so dogfighting, yes? And yes thrust vectoring is very important, it allows a fighter to turn a lot tighter than they used to be able too, while maintaining air speed... for dogfighting...

 

[rust]

I take it you aren't a licensed aircraft pilot?

No, I only served a couple of years with the support personnel of a
fighter-bomber wing and had to suffer more pilot talk and air combat
and ground support techniques discussions than I had ever feared.

For example, the best method for a safe bombing run seems to be to
get in low and fast, then turn upwards and sidewards away from the
blast at high speed, and finally downwards and back home again, a
maneuver difficult to imagine with a pure gravitics drive.

If you want to look it up, it is called a "low - high - low" bombing run,
and there were (and probably still are) endless discussions between
its "fans" and those of a "high - low - high" bombing run, which is a no
less complex maneuver.

 

[DFW]

So manoeuvring into an advantageous position in a dogfight is a waste of energy in time?

No, necessary but, those maneuvers become instantly obsolete with the advent of grav drives.

 

[DFW]

, a maneuver difficult to imagine with a pure gravitics drive.

Not at all. Nothing to prevent a grav vehicle moving and turning away, it just does it better. You don't even have to factor in induced drag as you have no lift producing surfaces and you don't lose the energy needed to create lift.

Basic aeronautics...

 

[far-trader]

So manoeuvring into an advantageous position in a dogfight is a waste of energy in time?

No, necessary but, those maneuvers become instantly obsolete with the advent of grav drives.

With your vision of the way grav drives work perhaps, if I understand your take which is not, I'll repeat, the way Traveller grav drives are generally presented. Traveller grav drives are generally slow, low thrust, limited maneuverability. You need to think much more like contemporary helicopters and much much less like mythical flying saucers.

 

[rust]

@ DFW

Well, since we obviously have quite different ideas what a gravitic drive
is capable of and no real world example to experiment with, this discus-
sion seems pointless, and I am out of it. :wink:

 

[barnest2]

DFW, why exactly do they become instantly obsolete. This low-high-low trick is about minimum exposure to AA weapons, and therefore minimum risk... i dont understand why this would become obsolete.

ETA: at least, as far as i understand the tactic...