Artifical Gravity & Inertia Dampers

[mike wightman]

CT starship details were always very sketchy.

S7 and the adventures which featured ships contained more details about artificial gravity and acceleration compensators (notice how everyone eventually switches to the Star Trek term?) but crucially no details about how they work. Nor were they ever included in the ship design sequence or Striker for that matter.

Original CT implied manaeuver drives are reaction drives then HG1 flat out stated they are fusion rockets.

By revised edition and HG2 the nature of maneuver drives became a mystery again, and then came MT...

 

[Ishmael]

You are misunderstanding. The turbulence you experience in an airplane is GREATLY magnified by the fact that the craft has wings. Without wings, it is nothing to worry about unless you are flying into REALLY extreme weather like a tornado or a violent thundercloud. Which is EASILY avoidable.

The Scout is a dart, not a wing.

An analogy for non-pilots: Motor boat vs. sail boat. The wind suddenly changes directions or suddenly picks up. Which craft rolls more?

It has little to do with whether a craft has a wing or not. It has everything to do with the amount of surface area available for fluid/air flow to act against vs inertia.The sailboat has much greater surface area for the wind gust to act against than the motorboat, thus the wind force will act against the sailboat in a proportionally greater manner. All an airplane's wings do is to add extra surface area for the flow to act upon.

The classic 'scout' shape can act as a wing and will provide lift although not as efficiently as a NACA profile which may be optimized for a greater lift/drag ratio within its expected performance envelope.
And the 'scout' does have a mush greater amount of surface area per unit volume than a box or a sphere.

Grav tech is not a magical panacea which can allow folk to ignore various unpleasantness.

 

[Carlobrand]

It has little to do with whether a craft has a wing or not. It has everything to do with the amount of surface area available for fluid/air flow to act against vs inertia.The sailboat has much greater surface area for the wind gust to act against than the motorboat, thus the wind force will act against the sailboat in a proportionally greater manner. All an airplane's wings do is to add extra surface area for the flow to act upon.

The classic 'scout' shape can act as a wing and will provide lift although not as efficiently as a NACA profile which may be optimized for a greater lift/drag ratio within its expected performance envelope.
And the 'scout' does have a mush greater amount of surface area per unit volume than a box or a sphere.

Grav tech is not a magical panacea which can allow folk to ignore various unpleasantness.

Wouldn't the classic scout have much less surface area per unit volume than, say, a 737? And, the classic wing - as I understand it - generates lift because the top is curved: air flows faster over the top than the bottom, creating lower pressure above the wing that generates lift. Near as I can tell, the scout is symmetrical in profile and would have to maintain a slight nose-up position to generate lift, no? Thus, more sail-like than wing-like.

A 737 - I use that because that's usually what I've ended up flying on - presents a wing area of 102 square meters for a maximum weight of between 50 and 58 tons. Length is a bit over 30 meters, body width is 3.76 meters, that'd have to be added on too, I guess. +113? 215? That's from the Wiki article on the 737.

A scout is 37.5 meters length by 24 meters width - 450 meters surface area? That angle adds a wee bit, but my geometry's not up to snuff. Mass by Megatrav's over 900 tons.

So, ignoring other factors - like whether the wings would act like a spring causing the center cigar-section to bounce up and down - the scout presents over twice the surface area but 15 to 18 times the mass, which implies that at the same speed it would be much more resistant to being displaced by turbulence. I'm not really sure of the physics, whether surface area is more critical or cross-sectional area or what, but it's pretty clear that the scout, despite its flatness, is much denser and therefore less susceptible to being shoved about by the same magnitude of external force.

 

[HG_B]

It has little to do with whether a craft has a wing or not.

Incorrect. A tremendous amount of the turbulence felt is because of the fact that the plane is using lifting surfaces to maintain position in 3 dimensions. Rapid changes in lift on all control surfaces is the main factor.

(see data on microbursts and precisely & aeronautically why they cause the effects that they do.)

In addition, modern airliners are EXTREMELY lightweight compared to a Trav star ship with its VERY heavy duty construction. An apt comparison (sans wings) might be a box kite measuring 20' x 10' x 10', add some lightweight engines + fuel vs. an M2 Bradley.

 

[Carlobrand]

Can you imagine spending years doing ground-to-orbits on starships and boats, and then flying as a passenger in a TL7 airplane? Scary!

 

[HG_B]

Can you imagine spending years doing ground-to-orbits on starships and boats, and then flying as a passenger in a TL7 airplane? Scary!

Kinda like spending years riding a passenger train back & forth across the US then, going across on a covered wagon where there are no paved roads...

Also, when you park your airplane outside where there might be high wind, don't forget to put the lift spoilers on the wings. That wind can flip your aircraft over due to sudden lift created. For some reason they aren't needed if you take the wings off & have no lift producing surfaces.

 

[Patron Zero]

My sincere appreciation for the clarification and opinions provided, that's what I like about this forum is that there's no 'special classroom' for those in search of such information.

 

[Ishmael]

Wouldn't the classic scout have much less surface area per unit volume than, say, a 737? And, the classic wing - as I understand it - generates lift because the top is curved: air flows faster over the top than the bottom, creating lower pressure above the wing that generates lift. Near as I can tell, the scout is symmetrical in profile and would have to maintain a slight nose-up position to generate lift, no? Thus, more sail-like than wing-like.

You have to make comparisons based on shapes of equal volume. Otherwise scaling laws ( cube-square laws ) would effect the outcome. The wedge shape has among the highest surface area-to-volume ratios of any of the convex shapes listed in Traveller ship building rules.
In any case, its the area acted upon by the 'turbulence' , regardless of whether its in the form of a fuselage/hull, or in the form of a wing, that matters. Area is a pretty important variable when calculating wind loads as the wind pressure acting on an area is the force felt.

the wedge shape can be considered as a symmetrical airfoil with an angle of zero lift equal to zero ( camber of zero ). So it must have a small positive angle of attack to generate lift. The wedge shapes are best suited for super- and hyper- sonic flight with the single wedge airfoil being stable enough for NASA to use it as a stabilizer on the x-15 project despite its greater drag than a double wedge airfoil.
The x-51 waverider doesn't even have ( or need ) wings as described by Traveller.
You don't need classic wings with classic NACA airfoils to create lift.
And even with classic wings, the surface area is of great importance in determining total lift.

So, ignoring other factors - like whether the wings would act like a spring causing the center cigar-section to bounce up and down - the scout presents over twice the surface area but 15 to 18 times the mass, which implies that at the same speed it would be much more resistant to being displaced by turbulence. I'm not really sure of the physics, whether surface area is more critical or cross-sectional area or what, but it's pretty clear that the scout, despite its flatness, is much denser and therefore less susceptible to being shoved about by the same magnitude of external force.

See, now its being decided that its the greater mass ( inertia ) that's determines how susceptible to turbulence a spaceship is and not whether or not it has, so-called, wings? I can buy that, but all other things being equal, a ship with greater surface area will be affected more than a ship with less surface area regardless if that area is in the form of wings or not.

---------------

HG_B: you might want to read a couple of aerodynamics textbooks to see how flow acts upon surfaces.
Also, you seem to have moved away from 'lack of wings' preventing turbulence from affecting a ship, the 'huge mass' preventing turbulence from affecting ships.
Huge mass will require huge power to accelerate, and that will have a lot of knock-on effects and perhaps a few unintended consequences... at least unless one departs from physics.( thruster inefficiencies over unity )

 

[Fritz_Brown]

The way Grav drive works in my game (MgT) is that the entire craft is affected by the G-drive.

Yeah, that's what I said in the beginning. And, how I started this fight.

Grav tech is not a magical panacea which can allow folk to ignore various unpleasantness.

It can be, if you want it to be. But, it's probably more fun for most of us if it isn't.

Also, when you park your airplane outside where there might be high wind, don't forget to put the lift spoilers on the wings.

You're talking a very light craft, there. Or you're talking more than gale force winds.

In any case, its the area acted upon by the 'turbulence' , regardless of whether its in the form of a fuselage/hull, or in the form of a wing, that matters. Area is a pretty important variable when calculating wind loads as the wind pressure acting on an area is the force felt.

Area isn't the only variable, however. One thing that hasn't been mentioned, but is a factor in why a winged body might bounce more than a solid lifting body: flexibility. Wings are built to be flexible - so, often, the response by the wings will be out of concert with the body's reaction. The flexibility actually helps the wings stay "strong" in response to the variables in lift and drag affecting it, but it can amplify the felt response in the fuselage, as well. (In some cases, it will lessen the felt turbulence.)

 

[aramis]

Yeah, that's what I said in the beginning. And, how I started this fight.


It can be, if you want it to be. But, it's probably more fun for most of us if it isn't.


You're talking a very light craft, there. Or you're talking more than gale force winds.


Area isn't the only variable, however. One thing that hasn't been mentioned, but is a factor in why a winged body might bounce more than a solid lifting body: flexibility. Wings are built to be flexible - so, often, the response by the wings will be out of concert with the body's reaction. The flexibility actually helps the wings stay "strong" in response to the variables in lift and drag affecting it, but it can amplify the felt response in the fuselage, as well. (In some cases, it will lessen the felt turbulence.)

A 50MPH wind can flip a C-130 from the right angle. That's just shy of gale force. A 40 knot wind can flip a dehaviland twin otter or a ford Tri-motor.

Any wind at or above stall speed from a quartering angle can flip a plane easily; many can do so below stall speed, since even a stalled wing is generating some lift.

 

[HG_B]

I can buy that, but all other things being equal, a ship with greater surface area will be affected more than a ship with less surface area regardless if that area is in the form of wings or not.

Now, THAT'S funny. Really, not being snarky. Well, maybe funny only to pilots.

 

[aramis]

Now, THAT'S funny. Really, not being snarky. Well, maybe funny only to pilots.

Yep. There's a reason you spend 4+ hours of your instruction learning to tie down your planes... (1-3 in ground school, and 3-6 with your CFI supervising tie-down. And in Alaska, also learning how to plant tie-down stakes for remote and improvised fields. My solo pre-plan included two airports without extant tiedowns... one of which was an abandoned navigational station.)

Every year, planes at Anchorage International are damaged by other planes that were improperly tied down and flipped in 30-40kt winds.

 

[Ishmael]

so what you are both saying is this....

given 2 airplanes of equal mass, they both have an equal chance of flipping even though plane #1 has a relatively tiny surface area and the other has a relatively huge surface area? really? Is it because of the wings? or because of total surface area per unit mass or are you saying that zeppelins and lifting bodies don't need to be tied down because they have no wings.....
or that the lift and drag equations only applies to wings.

now THAT'S funny

and that traveller starships are so massive that they won't need to be tied down despite having insane amount of surface area relative to typical airplane? the frontal x-section of a 10 ton small craft is about 14m^2...just slightly less than the wing area of a piper cub, but it masses too much to be bothered with wind gusts?

 

[aramis]

so what you are both saying is this....

given 2 airplanes of equal mass, they both have an equal chance of flipping even though plane #1 has a relatively tiny surface area and the other has a relatively huge surface area? really? Is it because of the wings? or because of total surface area per unit mass or are you saying that zeppelins and lifting bodies don't need to be tied down because they have no wings.....
or that the lift and drag equations only applies to wings.

now THAT'S funny

and that traveller starships are so massive that they won't need to be tied down despite having insane amount of surface area relative to typical airplane? the frontal x-section of a 10 ton small craft is about 14m^2...just slightly less than the wing area of a piper cub, but it masses too much to be bothered with wind gusts?

Given the same mass but different wing area (but otherwise identical bodies), the one with the lower stall speed is the one that will flip first if both are parked facing the same way.

A C119 needs to be tied down in 50+kt winds (stall is about 45Kt as configured for the Airline I used to day labor for, with full flaps; about 70 with flaps up), the one with the wings off didn't even budge in 100kt winds.

 

[HG_B]

Yep. There's a reason you spend 4+ hours of your instruction learning to tie down your planes... (1-3 in ground school, and 3-6 with your CFI supervising tie-down. And in Alaska, also learning how to plant tie-down stakes for remote and improvised fields. My solo pre-plan included two airports without extant tiedowns... one of which was an abandoned navigational station.)

Every year, planes at Anchorage International are damaged by other planes that were improperly tied down and flipped in 30-40kt winds.

When I was younger I was out of Stapleton (Denver) and we had the same problem. BTW, did ya know Stapleton is where Fujita first studied microbursts? Lots of rough weather along the Front Range there.

Anyway, I hope I'm fortunate enough to get to Alaska someday. It's conditions produce some the best Gen Av pilots.

 

[Vladika]

The average person really has no real concept of wind forces power or effect.

The Bernoulli effect is what causes pressure differences and "lift" on a wing.

The question/example of the scout ship hull should not be lightly dismissed. (It is certainly heavy enough for earth wind conditions but...not every planet is earth).

The point is that wind on any flat surface can and does produce a "suction" effect when blowing across the plane. Ever notice that flat roofed buildings are often "ballasted" with gravel holding down the roof due to that suction effect?

Wind loads are NEVER taken lightly by civil engineers and there is an enormous number of differing effects that must be known, understood and continually researched to understand those forces and how they work in differing situations. Safely designing for wind loads is both an art and a science.

 

[Fritz_Brown]

A 50MPH wind can flip a C-130 from the right angle. That's just shy of gale force. A 40 knot wind can flip a dehaviland twin otter or a ford Tri-motor.

I was thinking something more like a 707 and up. You know, a real plane. That's probably more in the weight class of a starship. A KC-135R had a takeoff speed around 100knots at its lightest, IIRC (it's been a long time).

Lots of rough weather along the Front Range there.

Oh yeah. Definitely an exciting place to have your first experience flying. (Gliders, Cessna 172s, and T-37s eventually.)

 

[HG_B]

I was thinking something more like a 707 and up. You know, a real plane. That's probably more in the weight class of a starship. A KC-135R had a takeoff speed around 100knots at its lightest, IIRC (it's been a long time).

An airliner isn't ANYWHERE in the weight range of a starship, for its volume. Maybe ~1/5 the weight at most.

 

[HG_B]

The point is that wind on any flat surface can and does produce a "suction" effect when blowing across the plane. Ever notice that flat roofed buildings are often "ballasted" with gravel holding down the roof due to that suction effect?

Bad example. The roof experiences that effect because of the lowered pressure as the wind isn't blowing beneath it, only over one side. A slab exposed on both sides to the same wind doesn't experience that effect.

 

[aramis]

Bad example. The roof experiences that effect because of the lowered pressure as the wind isn't blowing beneath it, only over one side. A slab exposed on both sides to the same wind doesn't experience that effect.

Ahem... Tacoma Narrows Bridge....