Suggestion, Super-streamlined, and Lifting hulls.

[wbnc]

one option I was thinking of, and I wanted to see if it made sense to anyone else.

Allowing for hull modifications such as

Super streamlined: basically allows supersonic or hypersonic flight in atmo for a starship...streamlined flight capped as high subsonic/trans-sonic when fitted with Aerofins gives an additional DM, or boon to maneuvers in atmosphere.

cannot be retrofitted to a design
costs an extra 10% to the hull cost due to design expense.

Lifting body:
cannot be applied to a small craft or starship over 200 Dtons.
allows the ship to make a steep glide, and controlled landing without power....within horizontal distance of say current altitude of vessel x5

reduces power drain when operating in atmosphere. or at lest an atmosphere better than trace or thin.

can not be retrofitted, or removed, after construction
cost roughly the same as the areofin option..
tonnage no extra tonnage.


Flotation Hull: allows a ship to take off or land on water, and power down without sinking, or suffering ill effects from direct exposure to water or other non corrosive/destructive fluids.

can not be retrofitted after construction:
no extra cost or tonnage, cost covered by hull costs

 

[Tenacious-Techhunter]

Real lifting bodies aren't limited to just gliding. They can do powered flight too. Also, they can get really big, as well. See Boeing's upcoming replacement for traditional "tennis-ball cans with wings" airliners, featuring theater style seating. A lifting body is more about the shape being streamlined and producing lift; that's all.

In my mind, it would be better to say "hulls with 'x' streamlining of size 'y' displacement have 'z' top-speed in 'a' thickness atmosphere", and "hulls with lifting body get +'x' Agility in atmosphere".


With regards to floating hulls, this is a matter of three things:

Buoyancy, which is displacement vs. weight,
Distribution of that weight (so it doesn't float with the engines too far in the air or too far below the ater)
and the Pressure Limits of the Hull; see the Futurama episode where the crew visits the "Lost City of Atlanta".

Ultimately, I think all Traveller ships qualify as floating, provided the cargo or fuel isn't too heavy; the real issue is, is the bottom of the hull built for a speedy landing into the water, like an amphibious plane, or does it have to slow down first, and plop in vertically?

 

[wbnc]

Real lifting bodies aren't limited to just gliding. They can do powered flight too. Also, they can get really big, as well. See Boeing's upcoming replacement for traditional "tennis-ball cans with wings" airliners, featuring theater style seating. A lifting body is more about the shape being streamlined and producing lift; that's all.

In my mind, it would be better to say "hulls with 'x' streamlining of size 'y' displacement have 'z' top-speed in 'a' thickness atmosphere", and "hulls with lifting body get +'x' Agility in atmosphere".


With regards to floating hulls, this is a matter of three things:

Buoyancy, which is displacement vs. weight,
Distribution of that weight (so it doesn't float with the engines too far in the air or too far below the ater)
and the Pressure Limits of the Hull; see the Futurama episode where the crew visits the "Lost City of Atlanta".

Ultimately, I think all Traveller ships qualify as floating, provided the cargo or fuel isn't too heavy; the real issue is, is the bottom of the hull built for a speedy landing into the water, like an amphibious plane, or does it have to slow down first, and plop in vertically?

your right, the liftng body and blended fuselage is a very flexinble bit of technology. The lifting body approach was limited by technology for years. As controls, and materials get more advanced the winged can approach may go the way of the biplane.

I do think however it would be useful to separate a hull that is streamlined, to reduce wind resistance, and keep from being buffeted about in atmosphere, and a body that generates lift., can glide, and maintain some degree of safe operation without power going to it's drives.


The amphibious option would be for ships that are designed to routinely operate from the surface of a body of liquid. The hatches and airlocks are positioned above the water line, and it can load, unload, and stay on station for any amount of time.

eh can make low speed take of and landing without damage, and are designed ot spread out the center of gravity, and structural load in a way that allows it to float level, and stable...and wont cause warping, or damage to the hull.

both modifications would require some serious attention to detail. as well as give them properties not found in a vessel that is simply streamlined. Which means they would have to be designed from the spine out with those options in mind.

 

[Tenacious-Techhunter]

Streamlining and lifting body are things that should be applied separately. Lifting Body would grant an agility bonus at the cost of one less level of streamlining, as it trades drag reduction for lift. Streamlining and lift are very atmosphere dependent; drag and lift go down in reduced atmosphere, leading to higher speed and reduced agility respectively.

Ability to meaningfully glide is a completely different issue, at it involves enough lift to maintain glideslope at landing speeds, which are low. Not really practical for anything but a flying wing shape, which is inefficient at high speeds. Such a "gliding body" would have a very low maximum airspeed, due to trading lots of drag reduction for lift. It should also impose an aspect ratio (length to width ratio) on the deck plan design. But, practically speaking, this only matters if the maneuver drives can't produce any thrust for some reason; which means it would only matter if the drives or power went out during the landing, because otherwise, there would be no way to reduce orbit speed to attempt a landing.

Most of the things that make a design amphibious have nothing to do with the hull. The airlocks, cargo bay doors, and the turret seals have to be designed against sustained pressure. It should probably have fuel tanks that can shift the fuel weight for balance. Ships may be assumed to have both of these features already. Add some anchoring systems, and some low-speed aquatic maneuver drives. Other than that, the location of the airlocks among the decks and the deck plans have to be appropriate. But none of this has to do with the hull itself, really; it's just a bunch of equipment cost modifiers, optional equipment, and deck design issues. Any ship can probably be assumed to be able to land on water with a controlled vertical landing, but it will drift around the surface uncontrolled without an anchoring system and aquatic drives.

One thing that would require modifications to the hull is to have a hydrodynamic hull, so a ship can land in water at speed, without having to stop all horizontal motion and attempt an all but purely vertical landing. But this really only matters for landing at speed, or puttering about on bodies of water at low speed looking for somewhere to park. Trade two levels of streamlining to get it in return for one point of agility while landing in, taking off from, or operating on the water. For an additional level of streamlining, you can have a completely submersible hull, so the ship can operate as a submarine. Hydrodynamic hulls can probably be bought for no extra charge on new ships built on worlds with considerable water coverage.

 

[phavoc]

Spacecraft should rarely be optimized for in-atmo operations. They are meant to work and fight and play in the vacuum of space. Maneuvering in-atmo is a potential kiss of death for most space ships. But with anti-grav tech a space ship CAN maneuver and land in-atmo (or even on the water). That doesn't mean they SHOULD, however.

Any ship designed to operate in-atmo is going to be superior in maneuverabilty to one that is not. With the addition of anti-grav tech it would be a killing machine - fast, maneuverable and not dependent upon wings for lift. Starships, however, are designed to travel in deep space, thus their engines and maneuvering thrusters and such are going to be optimized for a vacuum environment. While some of their hull configurations may lend themselves to easier maneuvers in-atmo, that should never be their trademark.

A ship designed to do both well would be an expensive hybrid. You have no need for aerodynamics in space, a flying brick works well when equipped with anti-grav. You would only want some semblance of this to make it easier, and a bit faster, to maneuver in-atmo or during gas giant refueling. Other than that it's a waste of credits. And no spaceship that isn't aerodynamically designed to speed through an atmosphere will ever be able to keep up with something that is. Conversely, a ship that is highly aerodynamic will have to make some tradeoffs as well. Though neither aspect is reflected in the game like it would be in reality.

 

[wbnc]

Spacecraft should rarely be optimized for in-atmo operations. They are meant to work and fight and play in the vacuum of space. Maneuvering in-atmo is a potential kiss of death for most space ships. But with anti-grav tech a space ship CAN maneuver and land in-atmo (or even on the water). That doesn't mean they SHOULD, however.

Any ship designed to operate in-atmo is going to be superior in maneuverabilty to one that is not. With the addition of anti-grav tech it would be a killing machine - fast, maneuverable and not dependent upon wings for lift. Starships, however, are designed to travel in deep space, thus their engines and maneuvering thrusters and such are going to be optimized for a vacuum environment. While some of their hull configurations may lend themselves to easier maneuvers in-atmo, that should never be their trademark.

A ship designed to do both well would be an expensive hybrid. You have no need for aerodynamics in space, a flying brick works well when equipped with anti-grav. You would only want some semblance of this to make it easier, and a bit faster, to maneuver in-atmo or during gas giant refueling. Other than that it's a waste of credits. And no spaceship that isn't aerodynamically designed to speed through an atmosphere will ever be able to keep up with something that is. Conversely, a ship that is highly aerodynamic will have to make some trade-offs as well. Though neither aspect is reflected in the game like it would be in reality.

True, but certain types need to be able to effectively and safely maneuver in atmo to do their job. scouts, corvettes( especially ones assigned to troop transport/support) most small craft, gunship/boats, smaller cargo vessels. survey/science vessels, search and rescue,personal transports, a wide range....

mostly small adventure class ships. Nothing much bigger than 200-300 tons...anything over 1000 tons should stay the heck away from anything with gravity, and solid, cold cold ground to run into.

The extra engineering would be minimal to a society ( after all we managed to build the An-25, and Airbus Beluga ( see below) that can build spacecraft that routinely travel parsecs at a hop. the percentages of tonnage and cost would reflect the wasted space, and extra expense of design.

This aircraft is basically on the same scale as a small starship....and it flies perfectly well. with 1400 cubic meters..roughly 100 tons if i am not mistaken...of cargo space.
Crew: Two
Capacity: 1,410 m3 (50,000 cu ft)
Payload: 47 t (103,616 lb)
Length: 56.15 m (184 ft 3 in)
Wingspan: 44.84 m (147 ft 1 in)
Height: 17.24 m (56 ft 7 in)
Wing area: 258.80 m2 (2,786 sq ft)
Empty weight: 86 t (189,595 lb)
Max. takeoff weight: 155 t (341,713 lb)
Powerplant: 2 × General Electric CF6-80C2A8 turbofan, 232 - 276 kN (52,200-61,960 lb) each
Fuselage diameter: 3.95 m (13 ft 0 in)
7.1 m (23 ft 4 in) in cargo compartment
Performance

Maximum speed: Mach 0.82 (1,004.54 km/h)
Range: 2,779 km (1,501 nmi) with 40 ton payload
4,632 km (2,501 nmi) with 26 ton payload

 

[phavoc]

Right, craft like the Super-Guppy (and it's Boeing prop and jet equivalents) are roughly the size of small starships. And while they are capable of flying they aren't particularly maneuverable.

A ship of 10,000 ktons could conceivably land in-atmo without issue. But it would be a literal flying brick - incapable of doing much more than dropping straight down and going back up, perhaps with a bit of an angle.

Smaller ships, cargo lighters, shuttles, et. al. would be built to operate efficiently in-atmo as well as space, but things like wings are useless in a vacuum, and actually are a hindrance when you think about efficient docking and storage (not reflected in the game). Ships designed to interface with a planetary atmosphere (with lifting surfaces, wings, etc) typically won't go beyond low to geo-synchronous orbit to deliver their cargo. While they might be able to do so, they won't normally do so because you spent a lot of money to create that ship to work in-atmo so it's fiscally not smart to use it anywhere else.

 

[wbnc]

Right, craft like the Super-Guppy (and it's Boeing prop and jet equivalents) are roughly the size of small starships. And while they are capable of flying they aren't particularly maneuverable.

A ship of 10,000 ktons could conceivably land in-atmo without issue. But it would be a literal flying brick - incapable of doing much more than dropping straight down and going back up, perhaps with a bit of an angle.

Smaller ships, cargo lighters, shuttles, et. al. would be built to operate efficiently in-atmo as well as space, but things like wings are useless in a vacuum, and actually are a hindrance when you think about efficient docking and storage (not reflected in the game). Ships designed to interface with a planetary atmosphere (with lifting surfaces, wings, etc) typically won't go beyond low to geo-synchronous orbit to deliver their cargo. While they might be able to do so, they won't normally do so because you spent a lot of money to create that ship to work in-atmo so it's fiscally not smart to use it anywhere else.

I agree with you up to a point. There are cases where a ship benifits from the ability to maneuver and operate in Atmo-and in space. the technology of TL-10-1 makes the engineering relatively minor.

The shuttle routinely docked with the ISS and had no serious issues with that process. The engineers did their job right. If properly designed and laid out a ship that has a streamlined lifting body can negate those problems.

A lifting body also doe snot have to be shaped like an airliner, or cargo plane, or even a shuttle, blended hull and delta type air-frames work very a delta would be able to roll match it's docking collar to another ship, and slide right up next to it as well as a box or cylinder. It just requires the pilot to adjust his approach...

the extra expense of a spacecraft with wings comes into play when the matter of actual weight comes into play. the shuttle was retired because it's wings were dead weight on a booster. a ship with a Fusion reactor, and advanced drives ( even reaction drive) can lift fr more than a rocket that hasn't really changed since Vaun Braun built the Saturn five..It's still oxidizer+fuel+ spark...off ya go....

a some point in the next few thousand years that little process will be refined to a point where they don't have to worry about the extra "dead weight" or they can design a lifting body that uses aerodynamics, and body shape to generate lift, without massive dead weight hanging off it n space.


between materials technology, power systems, engineering know ow, and some imagination yu would not have to trade ability to operate in atmo, for operating in space . Unless that's how you want to see the next few thousand years of progress...

 

[phavoc]

Sure, any in-atmo vehicle that can escape the atmosphere is capable of docking with another object or being brought on-board. However the large wings and rudder necessary for atmospheric operations require it to consume a much larger space than say a ships boat/modular cutter with the same lifting capacity. For the shuttle it's not possible to make folding wings that would survive usage, and a folding or even retractable rudder would also suffer similar design fate.

The shuttle's wings were dead-weight on launch, but allowed it to land like an aircraft for descent. So they were a design trade-off that NASA accepted (had they stuck with the original British design it would have been essentially a Datsun pickup-truck style, no frills just the payload, ma'am). And even as a lifting body it was never terribly maneuverable because it was too heavy and had no in-atmo form of propulsion aside from, well, falling!

A grav-equipped ship would not require wings for lift - it has anti-grav for that. But anti-grav doesn't provide propulsion, just lift. So it still needs a propulsive method, which most likely is a starship-style engine (unless you want to put in a air-breather giving you potentially faster thrust). Speed is still going to require aerodynamics. At higher speeds you want a thinner wing to produce less drag. Flying a flat-faced brick at high mach speeds doesn't work very well, which is why anything that flies at speed is aerodynamically designed for it. You could reach sub-sonic speeds, but I don't think you could break the sound barrier and not generate so much yaw that your craft would be controllable - unless it was designed for it in the first place. We can't do much with that today except as theory because we DO require wings for lift, and without it we come tumbling back to the ground.

Assuming you build a pure lifting hull without, or with very stubby wings, well, you'd have something like a helo I suppose. The stubby wings that double as weapons stores do actually provide some aerodynamic benefit and lift to a helo, though the rotor remains the primary propulsive lifting device. If you replaced that with anti-grav you'd have a current example. However the wings really don't do much for it. So you'd need to scale up to the larger designs NASA is working on, with the entire body being shaped as a lifting body. And that could potentially work, but there are two drawbacks. The first is that the extra space you need to build your craft into a 'wing' is not efficient use of space like a spacecraft would be designed for. Also the lifting portion is set with a specific carried weight in mind. When you toss in anti-grav it helps out, but if you still want the extra lift you still need to factor in additional body space to achieve that lift... which gets you back to designing a useful in-atmo craft but not a good spacecraft.

In some ways if you want to get to the ground soonest you don't want wings, as too much stress and they'd rip off. Assault landers want to scream in as fast as possible, and anti-grav would give you maneuverability - lift is something you really don't want or need. If you are taking off, you have lift from anti-grav, and you may want to have more maneuverability at that point, but it may be asking too much, too.

This is turning into an interesting theoretical discussion! Too bad we don't have anyone from NASA's Langley or Ames centers that could run us a simulation. It might be as cool as the time the shuttle engineersprogrammed the simulator in Houston with some MiG-25's trying to intercept the shuttle over the Pacific as it de-orbited. Needless to say they failed every time (Mach-25 has a tendency to do that).

 

[wbnc]

Oh yes, a very fun conversation it is I am having a great time


Wings: the one thing Jack Northrop hated more than anything when it came to aircraft...

first; the wings can be designed and constructed to fold at the point they join the hull. Or swept back into a smaller configuration: the tonnage dedicated would be a fraction of the ships total.this worked fairly well for high performance fighters in the past.

Using carbon fiber, or carbon nano-tubes, the structure could be hollowed out. Rather than using traditional wing spars. Or, greatly reduce the volume and weight of the spars. Allowing the wings to do double duty as fuel tanks, and lifting surfaces. This changes them from dead weight to functional components.( especially if the ship is jump capable, and needs multi-ton fuel loads.)


Scale of use:

I tend to agree that the cost/benefit is a bit thin...the number of ships that would benefit is limited, I never suggested otherwise. But under the right circumstances they would be useful, and effective.

Lets Look at the flying boat/float planes. Far more difficult to design, and operate than a conventional aircraft. However in the right situation they proved to be profitable enough for several companies to operate fleets of them. Servicing destinations where they had a distinct advantage.

if a colony or facility had no independent interface craft a ship that could safely operate in atmo with greater speed, and maneuverability would be useful. A scout ship would be able to handle rough/violent weather with greater safety..as would a search and rescue boat.

the addition of lifting surfaces greater streamlining and aerodynamic control would allow it to maneuver in bad weather, and close to the surface.if rules supported the reduction in fuel use for aerodynamic lifting bodies, those craft could greatly extend their operational limits without the need to set down refuel, or process local fuel sources.

 

[phavoc]

Okay, they woulda loved carbon nanotubes at the Skunkworks. And in theory with essentially diamond-tough materials you could do some wonderful crazy things.

But... you still have the same fundamental structural flaws at your join points. Having stronger materials means you can do a LOT more, or at least what we consider to be a lot more with our tech and limitations today. I'm sure you could a 14g yaw maneuver without the wings flying off. This is where we really need that NASA guy with the supercomputer and formulas...

I do concede that you could do all kinds of things to fold the wings and use less space. Bah! Eagle transporters for everyone! No more wings!!!

I'd still posit that even in the future materials will become damaged with overuse - granted its the future and we have all kinds of things... like weapons bleeding over from Star Wars into Traveller..... but more to the point metal fatigue is something that is inherently part of metal. So maybe while the ships last longer, they are still going to be subject to slow destruction with use... and the harder you use them the faster they fall apart.

Some of that has to be true to form the underlying economics of the Traveller universe. Otherwise those first jump-1 starships would still be out there flying. And great-great-great-great grandma's air raft would be handed down from generation to generation.

 

[Tenacious-Techhunter]

Spacecraft should rarely be optimized for in-atmo operations. They are meant to work and fight and play in the vacuum of space. Maneuvering in-atmo is a potential kiss of death for most space ships. But with anti-grav tech a space ship CAN maneuver and land in-atmo (or even on the water). That doesn't mean they SHOULD, however.

Any ship designed to operate in-atmo is going to be superior in maneuverabilty to one that is not. With the addition of anti-grav tech it would be a killing machine - fast, maneuverable and not dependent upon wings for lift. Starships, however, are designed to travel in deep space, thus their engines and maneuvering thrusters and such are going to be optimized for a vacuum environment. While some of their hull configurations may lend themselves to easier maneuvers in-atmo, that should never be their trademark.

A ship designed to do both well would be an expensive hybrid. You have no need for aerodynamics in space, a flying brick works well when equipped with anti-grav. You would only want some semblance of this to make it easier, and a bit faster, to maneuver in-atmo or during gas giant refueling. Other than that it's a waste of credits. And no spaceship that isn't aerodynamically designed to speed through an atmosphere will ever be able to keep up with something that is. Conversely, a ship that is highly aerodynamic will have to make some tradeoffs as well. Though neither aspect is reflected in the game like it would be in reality.

There are plenty of good reasons to want your starship to be streamlined. You could effectively be a puddlejumper, servicing several colonies on separate continents on the same planet. You pop in-system with your cargo, make the continental rounds, and go back out; the efficiency of those space-plane trips become important. It's even more important if your cargo is the only source of fusion fuels for that planet, and you do some fuel refining from the gas giant one system away.

It is not inherently true that a streamlined ship will always be faster or more maneuverable in atmosphere than an unstreamlined ship. The unstreamlined ship could simply take the "musclecar" approach; so long as it has enough thrust to overcome the drag, it can go faster; at the same speed, if it has thrust to spare, it can out-maneuver the other ship. Drop that same equipment in a more streamlined hull, however, and it will do both better.

I'm not convinced that Traveller spaceships that are streamlined are significantly more expensive than ones that aren't. Remember, we're talking about circumstances in which thrust and fuel are trivial, and so weight can be added to improve strength. The design constraints are considerably lower. Plus, composites are probably everywhere, and those can have some pretty exotic shapes.

 

[Tenacious-Techhunter]

the extra expense of a spacecraft with wings comes into play when the matter of actual weight comes into play. the shuttle was retired because it's wings were dead weight on a booster. a ship with a Fusion reactor, and advanced drives ( even reaction drive) can lift fr more than a rocket that hasn't really changed since Vaun Braun built the Saturn five..It's still oxidizer+fuel+ spark...off ya go....

Less the weight and more the drag. Weight too, but the drag is more significant.

 

[Tenacious-Techhunter]

So you'd need to scale up to the larger designs NASA is working on, with the entire body being shaped as a lifting body. And that could potentially work, but there are two drawbacks. The first is that the extra space you need to build your craft into a 'wing' is not efficient use of space like a spacecraft would be designed for. Also the lifting portion is set with a specific carried weight in mind. When you toss in anti-grav it helps out, but if you still want the extra lift you still need to factor in additional body space to achieve that lift... which gets you back to designing a useful in-atmo craft but not a good spacecraft.

Traveller has never had this level of detail in its ship design, much to our mutual chagrin. I would personally prefer to see the partial cubes around the surface of the craft arranged into half-dTon patches, which is where I would draw the compromise. Regardless, with weight not being significantly limited in any way, materials choice explodes, mostly negating these structure issues, and leaving it as spare fuel space.

This is turning into an interesting theoretical discussion! Too bad we don't have anyone from NASA's Langley or Ames centers that could run us a simulation.

Kerbal Space Program. Find a mod that gives you unlimited fuel, and thrust as required.

 

[Tenacious-Techhunter]

Scale of use:

I tend to agree that the cost/benefit is a bit thin...the number of ships that would benefit is limited, I never suggested otherwise. But under the right circumstances they would be useful, and effective.

I agree with this, on the whole. If it were me, I would keep streamlining levels, ditch lifting bodies, ditch hydrodynamic hulls, and keep submersible hulls. Lifting bodies and hydrodynamic hulls are just unnecessary complexity with insufficient modeling to back them up; the game works fine without them; but streamlining and submersible hulls have a direct relationship with top-speed and submersible ability, key gameplay features.

Lets Look at the flying boat/float planes. Far more difficult to design, and operate than a conventional aircraft. However in the right situation they proved to be profitable enough for several companies to operate fleets of them. Servicing destinations where they had a distinct advantage.

This is an excellent metaphor.

the addition of lifting surfaces greater streamlining and aerodynamic control would allow it to maneuver in bad weather, and close to the surface.if rules supported the reduction in fuel use for aerodynamic lifting bodies, those craft could greatly extend their operational limits without the need to set down refuel, or process local fuel sources.

Honestly, any sort of "maneuvering thruster" is just as good as a lifting or control surface; lifting and control surfaces just have the advantage that they don't require fuel or power.

 

[Tenacious-Techhunter]

But... you still have the same fundamental structural flaws at your join points. Having stronger materials means you can do a LOT more, or at least what we consider to be a lot more with our tech and limitations today. I'm sure you could a 14g yaw maneuver without the wings flying off. This is where we really need that NASA guy with the supercomputer and formulas...

Current fighter aircraft are purely pilot-limited in terms of maneuvers. There are projects to remotely pilot drones from AIWACS or other "control craft", because it's impossible for human pilots to take the G-loads. We have exceeded the realm where performance limits are structural or design issues. Once we have "inertial dampeners", they may creep up again... but they also might not. So I wouldn't make these assumptions about structural load, just because we have exceeded the point where they have a basis in fact.

I'd still posit that even in the future materials will become damaged with overuse - granted its the future and we have all kinds of things... like weapons bleeding over from Star Wars into Traveller..... but more to the point metal fatigue is something that is inherently part of metal. So maybe while the ships last longer, they are still going to be subject to slow destruction with use... and the harder you use them the faster they fall apart.

True in the broadest sense, but not necessarily in the specifics. Metal fatigue is a good example, but not necessarily the right benchmark. The right benchmark is purely fictional, so it can really go in whatever direction the GM would want; picking the right default benchmark is what we need to do for the sake of the rulebook. I would argue more in favor of composite construction and ceramic armor.

Some of that has to be true to form the underlying economics of the Traveller universe. Otherwise those first jump-1 starships would still be out there flying. And great-great-great-great grandma's air raft would be handed down from generation to generation.

We're still sailing tall ships from the age of sail. Granted, they've been mostly rebuilt, but I think the point is still valid. Certain ships will always, when treated with the proper love by their parenting culture, continue flying, if only as living museums. Is there anything in the fiction that says this doesn't happen?

 

[wbnc]

All Praise the immortal Eagle one!!!! May she ever descend in plumes of compressed gas!

Metal fatigue, and load strain is a real problem for any design. Ay design that has a load bearing structure is going to be a beast to keep running. Even My grandads 1965 Chevy pickup. You do not want to see what a compressor ring can do when a stress fracture happens...

The need for regular checks to find stress problems would be a major concern I admit. The use of wing/other aerodynamic forms would require a bit more attention to the health of the hull/structure.

It should be for most vehicles but most vehicles if something breaks you call a tow truck..In a starship your a few trillion miles from the nearest cell tower. In any aircraft you are suddenly reminded how bad nature, Newton, and Murphy hate clever people.

A bit of wit from a mechanical engineer."If it has two moving parts one will break or jam. If it has three moving parts..four of them will break or jam..." basically you have to expect things to break, including things you didn't thin COULD break...I take his work for it..his greatest achievement was to build a thingy that held a door shut...a couple hundred miles up..(damn wish I still had him on Messenger).


As for economics the issue is sometime worse than any engineering problems. How do you make this thing pay for it's own gas and parts. That's the major factor in my belief that these sorts of hulls would be special purpose, and not used on the majority of ships going atmo. ( I was factoring that in after you first mentioned it)

the trick is to model those costs in the rules to make it possible to see if it is worth it to the individual owner to build a super streamlined or lifting body vessel.How much of the ships tonnage is lost/used. how much the extra design work affects the total cost. how much the extra upkeep costs.

 

[phavoc]

There are plenty of good reasons to want your starship to be streamlined. You could effectively be a puddlejumper, servicing several colonies on separate continents on the same planet. You pop in-system with your cargo, make the continental rounds, and go back out; the efficiency of those space-plane trips become important. It's even more important if your cargo is the only source of fusion fuels for that planet, and you do some fuel refining from the gas giant one system away.

It is not inherently true that a streamlined ship will always be faster or more maneuverable in atmosphere than an unstreamlined ship. The unstreamlined ship could simply take the "musclecar" approach; so long as it has enough thrust to overcome the drag, it can go faster; at the same speed, if it has thrust to spare, it can out-maneuver the other ship. Drop that same equipment in a more streamlined hull, however, and it will do both better.

Most ships seem to be of the 'standard', semi-streamlined versions. There are a few that are streamlined (from the books that is), but the majority aren't. Which I think makes a lot of sense.

I think a semi-streamlined ship should have a relatively easy go of high sub-sonic speeds. But beyond that aerodynamics should be fighting against them. You still have all the drawbacks to control if your vehicle isn't designed for smooth in-atmo operations. A flying brick (literally) is FAR harder to control than pretty much any other form - maybe a convex design would be a worse idea. Regardless of your thrust capability you still run into the idea that the faster you travel the more power is required to simply maintain your speed. Then you get into things like actually trying to control your movements. It simply makes no sense to do something along those lines.

Assuming you had our 'brick' style flat nose ship and a standard hulled ship. The standard hulled ship would be able to do everything better at higher speeds just because it's not also fighting the atmosphere. And let's talk a dense, sea-level atmosphere for the example. The important point to that is the actual speed we are talking about. If they are both doing 300kph then I would say they'd be equivalent and thrust is greater than wind resistance. Now bump that up to say 2,000kph. At that speed the wind resistance is far greater, and the amount of energy required is higher as well. You start hitting diminishing returns at some point.

I'm not convinced that Traveller spaceships that are streamlined are significantly more expensive than ones that aren't. Remember, we're talking about circumstances in which thrust and fuel are trivial, and so weight can be added to improve strength. The design constraints are considerably lower. Plus, composites are probably everywhere, and those can have some pretty exotic shapes.

The system implies a 10% cost increase. Not terribly high, but if you think about it making a non-streamlined ship is pretty easy - right angles can be slapped together. A sleeker hull is often a design choice based upon often unrelated circumstances. I read an interesting paper on the creation of the Shuttle and why they chose the version the did. One of the underlying factors was that the guys doing it were aeronautical engineers and had unconscious bias towards aircraft styles. So they built what they were trained to do... it just so happened to meet all the other required criteria as well. Sometimes it's the little things that count the most and we totally don't think about them.

 

[Tenacious-Techhunter]

Metal fatigue, and load strain is a real problem for any design...

You missed my point. Metal isn't necessarily the go-to for Starship hulls, particularly in a highly fictionalized Sci-Fi setting. This argument is better made after the argument of "What is a starship made of?", which we haven't had. If it's composites and ceramics, it's not going to fatigue in the same ways, at the same rates, or have the same fixes.

 

[Tenacious-Techhunter]

I think a semi-streamlined ship should have a relatively easy go of high sub-sonic speeds. But beyond that aerodynamics should be fighting against them.

Drag. Drag is fighting against them.

You still have all the drawbacks to control if your vehicle isn't designed for smooth in-atmo operations. A flying brick (literally) is FAR harder to control than pretty much any other form - maybe a convex design would be a worse idea.

Control issues are easily resolved through computerized control systems; not an issue so long as you have Thrust to spare for control. See flying wings. Additionally, designers design and pilots fly their ships for their intended purpose.

Regardless of your thrust capability you still run into the idea that the faster you travel the more power is required to simply maintain your speed.

While you are not technically wrong, you are failing to grasp the concept. Drag is opposed by Thrust. Drag is a function of Speed. So while Power may be Thrust times Speed, Power is a red herring here. If your Thrust exceeds your Drag, you go faster.

Assuming you had our 'brick' style flat nose ship and a standard hulled ship. The standard hulled ship would be able to do everything better at higher speeds just because it's not also fighting the atmosphere.

You mean fighting the Drag with Thrust, and fighting the control issues with Thrust.

If they are both doing 300kph then I would say they'd be equivalent and thrust is greater than wind resistance. Now bump that up to say 2,000kph. At that speed the wind resistance is far greater, and the amount of energy required is higher as well. You start hitting diminishing returns at some point.

The point at which you reach diminishing returns is when the Drag is equal to the Thrust. Control issues if you do not have Thrust to spare for correction.

To this point, you have been muddying the issues by misconstruing your intuitive understanding of natural phenomenon for things that have not already been accounted for; they have.

I'm not convinced that Traveller spaceships that are streamlined are significantly more expensive than ones that aren't. Remember, we're talking about circumstances in which thrust and fuel are trivial, and so weight can be added to improve strength. The design constraints are considerably lower. Plus, composites are probably everywhere, and those can have some pretty exotic shapes.

The system implies a 10% cost increase. Not terribly high, but if you think about it making a non-streamlined ship is pretty easy - right angles can be slapped together.

No. Right Angles are not the right choice. Triangles everywhere; that's how you get your space frames. Easily very geodesic. Which can get you your very smooth domes, and can get you wing-shapes; not that you really want them, but you can have them if you're into that sort of thing. At that point, you apply a smooth skin, and put in a light-weight filler to back up the gap between the frame joints. Then you apply armor.

Because of the cross-sectional area issue, streamlining should not be a flat 10%; it should be dependent on hull volume in the broadest cases, and area for things like cylinders.