Streamlined Vs. Partially Streamlined

[BetterThanLife]

Time for a rather silly question that has been bothering me for some time. Why is it that only Streamlined ships can ground in a standard atmosphere? Or actually the better question is why is a Sphere or a Cylinder only considered partially streamlined?

Since the invention of Contra Gravity there is no reason for lifting surfaces on an Aircraft. Since the B-2 they have proved thre is no reason for vertical stabilizers (controlling yaw) on an aircraft. Since only one of the Canon ships that I have seen pictures of is a lifting body (The Safari ship) it appears fairly obvious that contra gravity keeps all starships from falling to the ground. (Though the F-4 Phantom, being the US Navy/Airforce evidence that if you strap enough engine to it even a brick can fly, might be a counter argument.) Now all current Civilian aircraft are Cylinders with lifting bodies (Wings) attached. And having studied a little about Aerodynamics, I know that a Sphere is actually a fairly low Coefficeint of drag shape (From any direction). Bullets (Especially boat tail bullets) are also extremely effecient aerodynamic shapes. So since lift isn't an issue why are Spheres and Cylinders only considered partially streamlined and why couldn't they ground on a planet with a standard atmosphere?

 

[Tanuki]

Probably because people were only thinking of hot re-entries when they wrote Traveller.

Given the constant G accelleration of Traveller ships there is no reason at all why any reasonably robust ship can't land on a planet with atmosphere. You just need landing gear or skids. If unstreamlined, you'll have to come in slow, matching ground speed of the planet's rotation and pretty much coming straight down -- probably a couple of hours for a safe entry at less than 50 mph. Come in slow and probably tail-first if just landing on drives; come in at any attitude you like if using contragrav for lift and maneuver drive for control.

A streamlined ship can come in a lot faster and may have aerodynamic surfaces for fine control.

Anyway, that's the way I've played it for years.

 

[Andrew Boulton]

MT, TNE, & T4 all separate streamlining from configuration (ie streamlining - USL, SL, or airframe - is an option that can be applied to the hull).

USL hulls are vulnerable to wind turbulance, making them unstable and dangerous to fly.

 

[rvatsaas]

A ship designed for space flight isn't necessarily designed to land either. Landing gear and suffient structure to hold form under gravity all takes extra mass

 

[aramis]

Tanuki:

No, you can't just match to rotation and come down... yyou need to match to winds aloft as you descend...

Part of SL is that landing gear...
Part of SL is an RCS that is atmosphere capable and doesn't poison the air.
PSL, as it is portrayed in Bk5, is really a streamlined design with no landing gear, and not designed for deep atmosphere landing.

Really, CT doesn't cover airframes at all.

 

[BetterThanLife]

Since Thruster Plates are a function of Gravitics, you can't poison the atmosphere with them. SInce Maneuver drives have no fuel requirement of their own they are not thrusters per say, they certainly aren't rocket, jet, ramjet, scramjet or other such engine. So since they don't intake fuel they aren't going to output exhaust, certainly not poisonous exhaust. (TNE might have some interesting drives that I am unaware of but starship drives in the CT/MT system are certainly reactionless, because they don't require a reaction mass.) Though messing with a gravitic field might have some interesting consequences for an ecosystem.

A Sphere is as close to an ideal aerodynamic shape as you are going to get. The problem with Spheres is they generate no lift unless you rotate them at ridiculus rates. They have a very low coeficient of drag from any direction, they are lift netural. (Which means you aren't going to generate lift by mistake or sudden gust of wind.) Updrafts, downdrafts, headwinds, tailwinds and cross winds will have little effect on them. The problem with Spheres is they are a pain in the butt shape to work with and in current applications they are lift neutral. (Which means you can't generate lift or downforce with it.) Now bigger spheres, give you room to work with. (Ie the Broadsword.) The Broadsword, as originally designed, has landing legs on the engine end of the ship. (Matter of fact in Adventure 7 the Broadsword is grounded on a planet with a standard atmosphere, which LBB5 says it can't be.)

A Scoutship is obviously not a lifting body but is aerodynamic enough to cut through the air in 3 directions (Actually virtually any direction in plane 90 degrees off centerline in either direction.). A Empress Marvara is aerodynamic enough for only one direction of travel(Forward). The Broadsword would encounter a slightly higher Coeficient of Drag going backwards (Towards the engines.) but would otherwise be fine travelling through an atmosphere. Now assuming the engines are directional, at least for higher degrees of thrust, it would be a good thing to have a higher Coefficient of drag while decellerating. (Though Standard Starship designs don't appear to be designed to fly tail down in relationship to the ground especially while landing, so how much weight the idea of having to point your engines has is beyond me.)

Just some silly thoughts. The obvious answer is "because that is the way the rules are written!" But as far as hard science goes it doesn't make lots of sense to me.

Originally posted by Aramis:
Tanuki:

No, you can't just match to rotation and come down... yyou need to match to winds aloft as you descend...

Part of SL is that landing gear...
Part of SL is an RCS that is atmosphere capable and doesn't poison the air.
PSL, as it is portrayed in Bk5, is really a streamlined design with no landing gear, and not designed for deep atmosphere landing.

Really, CT doesn't cover airframes at all.

 

[aramis]

A sphere also can't be made easily landing capable.

I wasn't referencing MT at all; MT doesn't use PSL. (USL, SL, and AF are the MT cats.)

Bk5 (HG2, specifically; not the rapidly changed out HG1 Bk5) and Bk2 don't actually state WHAT kind of thrust is used... just how much and how used.

HG1 stated fusion rockets.

A flattened sphere can be a lifting body (either by angle of attack, or differential flattening), and has a much more stable way to put landing gear down.

Also, skimming requires a hull that is capable of a couple thousand KPH in an atmosphere equivalent to the stratosphere... where there is enough atmosphere to ram into the scoops usefully.

Skimming requires PSL.
Landing requires SL. At least if there's an atmosphere.

And one thing not mentioned in CT directly: just cause you can land don't mean you can take off again...

 

[Tanuki]

Originally posted by Aramis:
A sphere also can't be made easily landing capable.

You think so? Check out Peter Vernon's Golfball Class Trader at: http://www.sff.net/people/kitsune/traveller/peter/starships.html

 

[BetterThanLife]

Originally posted by Aramis:
A sphere also can't be made easily landing capable.

If you read Adventure 7 Broadsword you will see that the 4 legs attached to the Sphere on the engine/Cutter exit end are described as landing legs. (They also happen to have the Missile Turrets mounted on them.) There are troop marshalling areas and airlocks for ground disembarkment there as well. With lifts to get the material from the ground to the ship's interior and vice versa. Most of the design appears to assume that the ship can indeed land. The Main Airlock, for interfacing with space docking maneuvers is at the top of the ship and is unsuited for cargo and large scale personnell transfers. (It leads to the Owner's suite and is suitable for entertaining clients but not for transferring troops.

) Though the only real bulk cargo access is through the spare cutter modules.

 

[BetterThanLife]

Originally posted by Aramis:
Bk5 (HG2, specifically; not the rapidly changed out HG1 Bk5) and Bk2 don't actually state WHAT kind of thrust is used... just how much and how used.

A flattened sphere can be a lifting body (either by angle of attack, or differential flattening), and has a much more stable way to put landing gear down.

Also, skimming requires a hull that is capable of a couple thousand KPH in an atmosphere equivalent to the stratosphere... where there is enough atmosphere to ram into the scoops usefully.

True it is never stated in HG2 or LBB2 what kind of thrust it is but since it doesn't require fuel or reaction mass then they certainly aren't thrusters. (Since it draws power from a Fusion plant then it is some kind of Electric engine or equivalent closed system.) Unless it is an electric engine spinning a big prop it isn't going to generate thrust in a conventional current technology sense.

As for some shapes being capable of lifting bodies, absolutely a Flatened sphere, a wedge, or a cone shape can be lifting bodies, even a close structure can be a lifting body. However only one of the canon ships is actually a lifting body, the Safari Ship. None of the other designs even attempted to appear to be so. (Though a case can be made for the FASA Stayaow Class Combat Scout and Ninz Scout, being lifting bodies they aren't stated as being such.) The wings, on those designs that have wings, definitely don't have the cross section to do more than slightly enhance stability and look cool. And they appear to be more cool looking than functional.

A 747 is obviously a close structure, made up of 5 wedges, and 5 cylinders (Unless you count the structure that holds the small cylinders (The engines) under the large wedges (the wings) to be an additional 4 wedges. So according to Traveller rules it can't function in an atmosphere and certainly can't land and take off.

Thinking about it, one would have to categorize the Wright Flyer as a Dispersed structure according to Traveller identification.

Not that the Wright Flyer was capable of much flight. But it certainly did operate inside an atmosphere.

 

[clementk]

2001 had a great lunar landing sequence with a spherical smallcraft. The graphics on the landing computer were later reused in Bladerunner and IIRC another movie. The design's the main thing here, since it wasn't in atmo.

See
http://www.palantir.net/2001/gallery/station.html
for some pics.

Casey

 

[Andrew Boulton]

BR reused a display from Alien. I don't think it came from 2001.

 

[clementk]

Originally posted by Andrew Boulton:
BR reused a display from Alien. I don't think it came from 2001.

Either my memory of the imdb entry for 2001 or bladerunner is faulty or it's been corrected since I'd last checked. The bladerunner entry still has references to Kubrick's influence and the end footage used from The Shining (see the trivia section).

A good excuse to rewatch all three over the Holidays!

 

[clair_rand]

"Since the B-2 they have proved thre is no reason for vertical stabilizers (controlling yaw) on an aircraft"...

Have a look for the Go-229 or any of teh Horton aircraft from WWII era.. if you think you actually *need* all that CPU horsepower to make a flying wing actually work..

always liked the GURPS space method of streamlining.. basically it helps.. but with a strong enough hull it doesn't matter much, cept streamlinign can provide lift and thus save fuel.

traveller never really cut it for me in atmosphere, now adding the required bits to the UCP sequence would probably get complicated, wing efficencies etc but hell it could be way cool

 

[mike wightman]

One of the features of the T20 design system is that, while based on High Guard, the streamlining of most hull configurations can be upgraded by spending money on them.

 

[BetterThanLife]

Originally posted by Sigg Oddra:
One of the features of the T20 design system is that, while based on High Guard, the streamlining of most hull configurations can be upgraded by spending money on them.

Money, space and computer power. But yes you can land everything but Asteroids and Dispersed structures in T20. At least in theory.

 

[aramis]

Guys, the Broadsword and Golfball basically proves my point about spheres:
in the golfball, a very small portion of hull has been stressed to take the full deadweight. Works OK, if you have gravitics, but if you have any kind of reaction thruster, that's going to make the "unloading zone" pretty much slag. additionally, it'll have a stability issue if not landed on really flat terrain. (you need to keep the Center of Gravity between/above the edges of the landing gear... the shown gear is a small plate...)

In the Broadsword, a significant chunk of the ships tonnage to landing legs... sure, they are used for other purposes, but it's no longer aerodynamically a sphere.

The third approach would be fold-out or extensible legs... get the stability when down, and the aerodynamics when not. But that is aadded complexity, and proportionately much further to go for the legs than on a flattened sphere.

 

[BetterThanLife]

Originally posted by Aramis:
Guys, the Broadsword and Golfball basically proves my point about spheres:

<Snip!>

In the Broadsword, a significant chunk of the ships tonnage to landing legs... sure, they are used for other purposes, but it's no longer aerodynamically a sphere.

The Broadsword is more sphere than the Marvara and the Subsidized Merchants, as described and drawn in Supp 7, are Cones. (Especially the Marvara.) Remember that the shape desiginator is a general shape, not a precise shape. Afterall the venerable Type-S is either a pointed wedge or a flatened cone. (Supp-7 and 9 both say it is a cone but MT and T20 both call it a wedge.) It certainly isn't a nice round cone and most wedge shapes are pointed in only 2 dimensions (Ever split wood?) giving you an edge not a point. The X-Boat is listed as a sphere but is obviously a cone. (Though the front appears to be round.)

The Broadsword does have blended projections, but they are aerodynamically blended to the back of the hull and the direction of travel is still a sphere to the oncoming wind and at least 80% sphere to cross winds. The only direction it appears to be less than 80% sphere is from directly astern. (See page 25 of Adventure 7 and calling it less than 80% sphere from astern is being generous.) On the other hand the only CT, GDW canon ships that the deckplans actually show the landing gear is the Broadsword. The Scout/Courier-Seeker shows only the Rear two of the assumed three landing struts (The front one for ideal stability would be in the middle of the Cargo Hold and up into the Bridge.) and the rest of the ships don't show where the landing gear is. The Far Trader shows well over the 200 Dtons but doesn't show any provision or space for Landing gear at all. (If I missed a set of deckplans I appologize, I don't own everything published.)

BTW the standard Launch, Ship's Boat, Slow Boat, Cutter, the Kininur's Pinace, the Leviathan's Shuttle and Pinnace and the Safari ship's Launch are all clearly cylinders and therefore shouldn't be capable of landing. (Though in all fairness the Safari Ship's Launch is a flattened Cylinder.)

 

[aramis]

Cylinders share much of the smae problem as spheres for landing gear... but generally have a long axis which is usually stable.

I'm not saying you can't have a "Landing gear equipped sphere", I'm saying it's less stable or takes more materials than say, a flattened sphere. Or a flattened pyramid with a diamond shaped base... I always assumed the third landing leg was up in the avionics bay, BTW, and the thing leans down in front...

The only real distinction in Bk5 between PSL and SL is that SL can land safely and repeatedly.

That spheres are not inherently assumed to be SL immplies little more to me than "It costs CrX per ton to restress the hull to handle the LG". Kind of like how certain fighters today are designed identically except for after-fusilage framing to take a carrier hook on the naval model, versus a much lighter afterfusilage framing on the airforce model...

 

[BetterThanLife]

A Sphere is inherently a stronger shape than most other shapes. (I think an egg is just a little stronger as a basic shape but they are close.)

If the Forward gear on the Scout is in the Avionics bay then it is much smaller than the rear gear and would have to be shorter than the main gear even though the front strut would have to be longer than the back struts because the shape is narrower (From a cross section perspective) and slopes up from tail to nose. Yet the lower cargo hold is towards the front of the craft instead of towards the rear where teh craft is thicker.

But what makes landing gear stable. It would imply a stable 3 or four points around the center of gravity of the ship that would be inherently stable standing still instead of being off center and having a tendency to tip. (BY the location of the landing struts on teh Broadsword they are on the perimeter of the sphere so are inherently stable. Then also connect to the equator of the sphere so they are not only at the edge of the sphere and equidistant from the center in placement but because they are connected at the equator the ship is inherently stable on its gear in 3 dimensions.

A Type-S by comparison has its rear struts too far forward and actually close to the CG of the ship, by virtue of the shape. The majority of the mass is in the rear of the ship and therefore the CG is quite a bit farther back than a line hapfway between the front and the back of the ship. One might even be able to argue that the Rear Struts are actually a little ahead of the CG. (And therefore the ship couldn't be stable in a landing situation. It would tend to flip up onto its tail.(Especially with a light fuel load.)

Now the Golfball would be less stable as the legs are close to teh center line, at least in the pics. (Unlike the Broadsword which has a wide stance.) IT would be therefore fairly easy to tip over.

Originally posted by Aramis:
Cylinders share much of the smae problem as spheres for landing gear... but generally have a long axis which is usually stable.

I'm not saying you can't have a "Landing gear equipped sphere", I'm saying it's less stable or takes more materials than say, a flattened sphere. Or a flattened pyramid with a diamond shaped base... I always assumed the third landing leg was up in the avionics bay, BTW, and the thing leans down in front...

The only real distinction in Bk5 between PSL and SL is that SL can land safely and repeatedly.

That spheres are not inherently assumed to be SL immplies little more to me than "It costs CrX per ton to restress the hull to handle the LG". Kind of like how certain fighters today are designed identically except for after-fusilage framing to take a carrier hook on the naval model, versus a much lighter afterfusilage framing on the airforce model...