Hull Configuration

[rust]

Now other questions because dispersed and close seem to be the most problematic for definitions.

In my view "dispersed" would require that the ship consists of several -
at least two - substantial parts, not only that it has some appendages
with a comparatively minor volume.

For example, I would see a volume distribution of 90 : 10 not as "dis-
persed", while I would count a volume distribution of 40 : 30 : 30 as
"dispersed".

On the other hand, a "close" configuration should have as few and as
small appendages as possible, in my view not more than perhaps 10 %
of the volume outside of the geometrical hull shape.

Again, it would be difficult to define the "border" between the two confi-
gurations.

Take a wedge with wings and "outriggers" at the wing tips. If the wings
plus "outriggers" would contain less than 10 % of the total volume, the
ship might have a "close" configuration, if they contain more than 30 %
of the volume it would most probably be a "dispersed" configuration ...

 

[AndrewW]

Why are some of the ships shown listed as one configuration when they have nothing to do with the configurations listed?

I suspect the artists who created the deckplans were not aware of the
configuration problem.

The deckplans are done based on the artists drawing of the ship, so I wouldn't say it was the one doing the deckplans, though the one doing the drawings might not be aware.

 

[hdan]

I'd consider something like the Tie Fighter to be a Sphere with aerofins, and an X-Wing to be a Needle with aerofins.

 

[BP]

All this is really fascinating, but not a single one of you has answered the questions of this post. So, I'll ask again. This time, please try to answer.

You might re-read some of those early posts - people did answer several of your questions and did try. Nobody has any obligation to answer any of your questions - and a little gratitude to those who invest the effort would probably be in your best interest.

It is also the nature of a public forum for posts to stray from what the OP originally intended - no harm restating your questions (or even starting another topic).

What is the difference between wedge, needle, cone?

The basic shape is the difference. Specific examples - see here for cone, or think party hat or rocket nosecone; here for wedge, or think cheese wedge. A needle shape is narrow and long and pointed (i.e. - pine needle), or, basically, a cylinder or wedge that tapers towards a point. They have different geometric construction methods, dimensions and thus surface areas and volumes. (These probably, loosely, being the basis of the game mechanics defined for them - though the interpretations are, of course, debatable.)

Why are some of the ships shown listed as one configuration when they have nothing to do with the configurations listed?

Given your other questions - it might help if you were to state specific examples (ship and page number).

But, take a good look - the deckplans, even when they do match the illustrations, rarely even match the tonnage (i.e. - the modular cutter would have to be essentially squashed - not a cylinder for the deckplans to represent the proper tonnage). So even when the configuration matches the shape - they still don't match one of the other primary specs. Flat out - a good many of them are 'wrong'. This is a game and MGP is a publishing company - not an engineering firm - and most published Traveller deckplans fall victim to these same inaccuracies.

What is the criteria for stating a hull is one configuration as opposed to another?

Simple -

• Its origin and nature (Planetoid/Buffered Planetoid), or
  Its basic shape (Wedge/Cone/Cylinder/Sphere), or
  Its topology if it has no over-riding basic shape (Closed or Open, like with respect to air = Close/Dispersed).

 

[rinku]

NCC-1701: I would assume dispersed.

Pretty much. But you could make a case for close structure as MOST of it is in two big traditional hulled chunks that are connected by a pretty substantial neck. On the other hand, it's most of the engineering hardware stuck out on those booms...

Battlestar: Dispersed looks most likely made up of a wedge or three

No, I'd say close structure here. Everything is nicely compact.

Re the starfighters... they fall under small craft and you only have to decide between Streamlined, Standard and Distributed. All the ones mentioned would be Streamlined, in the context of their sources (TIEs should probably be Standard, but in Star Wars they seem to have no trouble operating in atmospheres). The Gunstar might be a candidate for Standard as well, but I can't remember if it ever went atmospheric.

Football: cone? double cone?

A Sphere for my money, unless elongated, in which case probably a cone.

catamaran: two cones or needles, but it would also be a dispersed, yes?

Depends on the bridge between them. If it's a substantial part of the ship, it could be a close structure.

My take is that if most of the ship (say 2/3) is in one compact body, it's probably a close structure, even with some parts on outriggers. Especially if the sticky-out bits are just weapon or sensor booms, or are control surfaces for atmospheric flight (for example, a capital ship shaped like an X-Wing would probably be classed as a needle). The ship out of Avatar is a good example of a definite distributed one, IMHO.

 

[Thkaal]

Thank you rinku and BP and again rust. Those answers actually made sense.

Gunstars did go atmospheric, they launched from planets and Alex's actually landed in a trailer park.

I used the fighters as an example of shapes. Regardless of actual size, I was using them as a means to help identify the shapes of the configurations.

I apologize my brusqueness, however you will notice that it worked.

 

[Rikki Tikki Traveller]

The Enterprise is indeed a Close Structure, which consists of two or more different hull forms together.

The Enterprise is a Disk (Flattened Sphere) and a Cylinder (lower deck area) with engines nacelles.

A Dispersed structure is more like something made with a framework structure, think of the current designs for interplanetary travel.

Airplanes are Needles with Aerofins (for the most part).
The American Stealth Fighter is a Wedge design.

Traveller artists almost NEVER got the shape of the hull correct, and Mongoose is no different.

The Scout/Courier is the exception to the rule.

 

[rinku]

One particular frustration is that Mongoose have drafted new deckplans (not a bad move in several cases. I love the old Scout, but putting in a proper airlock WAS a good move) but are using art based on the classic designs. The Lab Ship is a particular case in point, but the Corsair and Scout also have issues.

The best of the old deck plans was probably the merc cruiser. Not sure why the Mongoose one has made the modular cutters elliptical, though. The worst of the old ones was the Empress Marava Far Trader out of the original Traders and Gunboats, since it was patently too large for a 200 ton ship (Always wondered about that. Maybe the author forgot the tonnage and never checked? Anyone know the story?). The Mongoose resized version looks good.

 

[Silvereye]

Not sure why the Mongoose one has made the modular cutters elliptical, though.

Perhaps it's because they are ~7.5m wide x ~3m high. The eliptical design certainly seem better suited to the shape then round one in my mind.

 

[rinku]

Yeah, but that's a change Mongoose applied. Traditional Trav small craft have a circular cross-section, like submarines and airliners. I would have thought that this would still be the most sensible cross section for any pressurised compartment. The "waste" space in the floor (and maybe ceiling) would be where you'd put machinery, grav plates and storage.

 

[Silvereye]

As I said, the change in cross section is one I personally like. The circular cross section is certainly better at withstanding external pressure then a 'petrol can', especially with the addition of ribs. Submarines have to withstand a much greater external pressure on the outside of a hull (due weight of water) then a space vehicle would likely experience on the inside of the hull (higher pressure then the partial vacuum outside) - the space shuttle is not a spherical pressure vessel like Trieste. The advent of high TL materials will likely make this shape even less necessary.

As to extra deck space for being circular, 1 dton is ~ 1.5m x 1.5m x 3m. This leaves about 1/3 dton of deck space for equipment if the habitable bit is reduced to 2m high.

Draw a scale rectangle 1.5m x 7.5m, then draw a circle with a shared centre with the rectangle and radius of a corner of the rectangle.

The radius of this circle is ~4.04m meaning it has a cross section area of (4.04m x 4.04m x pi) 51.28 m²

The are of the rectangle is only (7.5m x3m) 22.5 m²

That is an awful lot of spare storage space! And you'd certainly not be able to squeeze the round ship into a 1 or 2 deck high hanger.

 

[rinku]

The old modular cutter had a circular cross section of approximately 6m diameter. This would make it a two-deck vehicle, allowing (as usual) about 2m clearance for the actual deck. In practice, most of the vehicle (30 tons) is a cylindrical module which could be configured in several deck configurations. The length of the cutter works out to about 24m. The outer hull curvature is not extreme in any way, and quite comparable to a contemporary cargo aircraft.

The new oval cross section as shown in the merc cruiser deckplans does not actually match up with the modular cutter deckplans, either. On the cutter plans, the craft is clearly 7.5m on the beam, while on the cruiser plan, the bays seem to be 6m wide and about 4.5m high. I also can't see that they have properly allowed for the spare modules, which have to have the same cross-section as the craft (on the original plans, the middle decks had a 6m x 6m bay extension adjacent to the 6m diameter cutter well to allow for this. (this *is* shown in the cross-section, but this seems to just be a reapeat from the original Braodsword plans - when you line up the decks shown it does not compute).

I *don't* have any problem with elliptical bodied small craft, by the way. In YTU, or as a variant, no problem. It just annoys me that this seems to have been a change for change's sake, which has then been inaccurately applied to the deckplans.

Interestingly, the cutter is approximately the same size and general design of the space shuttle orbiter (main body is 5.2 x 4 m and length is 37.24m. Both have most of their volume devoted to a multi-use bay).

 

[far-trader]

The Enterprise is indeed a Close Structure, which consists of two or more different hull forms together.

I'd have to disagree with this. My take and opinion is:

A Close Structure is a collection of two or more hull sections without significant projections or separation.

A Dispersed Structure is a collection of two or more hull sections characterized by significant projections or separation. It need not be an open framework connecting the sections but can be.

The Enterprise is clearly Dispersed. The nacelles are well distanced from the saucer, as is the lower cylinder.

The Galactica is clearly a Close Structure (except with the flight decks rolled out for launching and recovery of Vipers, maybe, it's still not much of a projection or separation though so probably still a Close Structure).

 

[rinku]

Submarines have to withstand a much greater external pressure on the outside of a hull (due weight of water) then a space vehicle would likely experience on the inside of the hull (higher pressure then the partial vacuum outside) - the space shuttle is not a spherical pressure vessel like Trieste. The advent of high TL materials will likely make this shape even less necessary.

The engineering problem for a spacecraft is not external, but internal pressure, though small craft have to deal with both! A sphere is the best container, but is normally less practical than a cylinder. Cylinders with rounded or tapered ends are used for storage of high pressure liquids and gasses for that very reason. Material of the wall is pretty much irrelavent - high tech materials (if cost effective for the purpose) would just give lighter weight containers for a given wall thickness.

Now, other design considerations definitely come into play with something as complex as a spaceship, especially when artificial gravity is involved, so I'm definitely NOT saying everything has to be a sphere or cylinder. But at any tech it does make sense to base the pressurised part of a ship on a circular cross-section. For the record, this is precisely the approach on the space shuttle - the forward (pressurised) compartment is basically a rounded cone attached to a cylinder. The external fuselage is a bit more angular, but it's designed for reentry and gliding, not keeping the chance of a pressure rupture to a minimum.

 

[Silvereye]

Currently the pressure issues with a spacecraft probabaly pale in comparisson to the re-entry stresses. I'm not an aerospace engineer and I've not found any detailed drawings fo the shutlles pressurised area. Those sketches I've seen do show it as some deformed, kind of round, cone though. It appears to be mounted in the external structure at four points to help minimise heat transfer during re-entry.

The external structure really has nothing to do with the pressurised space except for having enough space to contain it. It is there for doing other things (cargo bay, flight surfacessomewhere to hang engines). This was why I used the example of Trieste (though many other deep submersible vessels would also work). The external structure of Trieste was mainly just the ballast systems and somewhere to attach propulsion. The pressurised bit for the crew was the ball at the bottom of the hull.

As an aside I repeated the geometry for the original MGT cutter (3 squares wide - 4.5 metres) prior to it getting expanded. The circular cross section was much more able to represent the hull and displacement when it is this narrow. While the circular section is generally larger, it is a lot less then when it is 7.5 metres wide. It still was too big to fit in the mercenary cruiser though. I want to know how you can fit a spare module in the cutter wells let alone have the space to transfer them without resorting to bending dimensions fo space.

I hadn't noticed similarity of the size of the shuttle and cutter though. The TL7 antique shuttle in High guard is approximately 6m x 6m x 30m excluding the wings and the tubby bit at the back with the engines.

 

[BP]

... For the record, this is precisely the approach on the space shuttle - the forward (pressurised) compartment is basically a rounded cone attached to a cylinder. The external fuselage is a bit more angular, ...

Nope.

The internal spaces for the crew compartment largely follow the contour of the exterior (and definitely not a 'circular cross-section'). The internal framing members are directly attached - there is no separate 'pressure hull' (a space ship is not a submarine - the only real similarities are the self-contained atmosphere).

Source: my father worked for NASA from the early 70's to the early 80's and he had most of the interior of our 2-car garage pinned up with (actual production) scale blue-prints of the cabin!

Not counting on memory, I dug up my 1979 NASA Facts poster - it has a beautiful cutaway of the various components depicting internal framing and flight systems (wow, I've got Apollo/Skylab 'Zero In On Safety' stickers from 1972/1973 from JSC and a 'Go For Pad' sticker along with some mission stickers... too bad I cut notches in the side of that poster - gotta scan that sucker!).

 

[Lord High Munchkin]

At the weekend, I found my parents have an official NASA Super-8 reel of film of the moon landing (in it's original box). They were about to "skip" it.

It's weird what you find.

 

[BP]

At the weekend, I found my parents have an official NASA Super-8 reel of film of the moon landing (in it's original box). They were about to "skip" it.

It's weird what you find.

Really? :shock:

(Not familiar with "skip" it - sure hope that doesn't mean trash or hock?!)

Seriously, NASA might be interested in this (you'd be surprised at what they didn't consider important back in the day - there is a lot that has been 'lost' - even if it is just quality of original recordings) - I would be happy to pass info along to the Principal Investigator for the LAMP (Lyman-Alpha Mapping Project) portion of the LRO (mid last year NASA launched the Lunar Reconnaissance Orbiter).

 

[Lord High Munchkin]

Yes, "skipping" in this context means throwing it out in the rubbish.

They are of the generation that simply isn't interested in Space (or the "Interweb thinggie"), but once it was pointed out to them, even they realised it was valuable.

I think they will put it up for auction, most likely get a young someone to "e-bay" it for them (they have seen the ads on the TV).

 

[BP]

Wonder why they would have a film on a subject they are not interested in - at any rate, like I said NASA may be interested in it (last year they definitely were... inside info).