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Trek Tech Pass me the quantum flux regulator, will you?

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Old November 6 2013, 05:37 PM   #16
Nob Akimoto
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Re: Density of star ships

I'm curious why a starship should be compared to a conventional naval vessel for density. Is there some reason it needs to have a density of less than water? If we're going to talk about common sense, the material descriptions we're given about starships is that they're designed to withstand weapon impacts that destroys relatively dense things like iron-nickel asteroids with ease. Even assuming that say torpedo technology evolved significantly between 2293 and 2370, an unshielded Enterprise-A was taking torpedo hits that would presumably destroyed much larger asteroids with relative ease. In which case the hull materials being less dense than a combination of nickel and iron doesn't make a lot of sense. Indeed the requirements for a starship constructed in space (contra the absurdity of ST09) are probably more toward better thermal properties and maybe radiation shielding over things like lightness. There's simply no need for a starship that uses mass reduction technology to worry all that much about using high density materials for its hull.

There's nothing in canon or even official sources that suggest a 190,000 ton Enterprise, and there's evidence to suggest ships are, in general, heavier than water. There's no real reason for the compromises that naval vessels have to deal with in terms of hull density on a starship.
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Old November 6 2013, 06:23 PM   #17
Crazy Eddie
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Re: Density of star ships

Nob Akimoto wrote: View Post
I'm curious why a starship should be compared to a conventional naval vessel for density. Is there some reason it needs to have a density of less than water?
Good point.

Personally, I prefer to compare starships to real-world spacecraft like the Soyuz or the Apollo CSM/LM. Been a long time since I did the work, but I figured out that the entire Apollo stack had a density of about 290kg/m^3, while the space shuttle was closer to 170 and Soyuz was around 210. Most newer spacecraft -- the Dragon, Cygnus, HTV and ATV cargo ships, for example -- have similar densities between about 150 and 250kg/m^3.

With a volume of 215,000m^3, that would give the Enterprise-A a mass of 32,250 to 52,500 tons.

If we're going to talk about common sense, the material descriptions we're given about starships is that they're designed to withstand weapon impacts that destroys relatively dense things like iron-nickel asteroids with ease. Even assuming that say torpedo technology evolved significantly between 2293 and 2370, an unshielded Enterprise-A was taking torpedo hits that would presumably destroyed much larger asteroids with relative ease. In which case the hull materials being less dense than a combination of nickel and iron doesn't make a lot of sense.
You're assuming that density is equivalent to physical resilience, which is not always (or even usually) the case. A starship with a 2-meter thick hull of deleted uranium isn't going to be more resistant to impact damage than a starship with 10 aluminum whipple shields 20cm apart. Add kevlar between the shields, you double its resistance; add trek-style forcefields between the shields, you make it virtually indestructible. Far more importantly, a 2-meter shell of depleted uranium is a lot harder to repair or replace or even service than a stack of thin wipple shields bolted to a frame; a photon torpedo may peel six of ten layers of your hull plating, but since it's just thin aluminum plate you can just unbolt the damaged sections and slap new ones in its place (whereas depleted uranium will crack/spall and possibly shatter as huge chunks of it are propelled into the inner hull at tremendous speeds).

Something to remember in space is that kinetic impacts are an action-reaction relationship. Putting more mass in front of a projectile simply creates more mass that can be thrown towards you when it hits. You want to DEFLECT the projectile, not stop it cold. Starships use deflector shields for this purpose, but their hull plating probably works in a similar way, in which case it is probably VERY low density and a lot more elastic than most of us would believe.

Indeed the requirements for a starship constructed in space (contra the absurdity of ST09) are probably more toward better thermal properties and maybe radiation shielding over things like lightness. There's simply no need for a starship that uses mass reduction technology to worry all that much about using high density materials for its hull.
Mass reduction costs energy. The less you have to reduce your mass to maneuver at impulse power, the more energy you have available for things like phasers, shields and sensors. As with real-world spacecraft: a heavier ship has a certain mass penalty as it burns through its fuel that much faster to get the same performance.

What's more, radiation shielding isn't accomplished (normally) with high density materials. Protection from radiation usually requires some material with a lot of hydrogen; LH2 and distilled water work exceptionally well, as does parafin or other forms of hydrocarbons. A ship with forcefield technology wouldn't have as much of a need.

There's nothing in canon or even official sources that suggest a 190,000 ton Enterprise, and there's evidence to suggest ships are, in general, heavier than water. There's no real reason for the compromises that naval vessels have to deal with in terms of hull density on a starship.
Naval vessels don't have to make much of a compromise, actually. They just have to displace more water than their own mass, which means there's a minimum size their hull components must be built to in order to achieve the needed displacement for their intended fittings.

Space ships start with completely different design assumptions. You start with mission capabilities, and then you go through a catalog to see what systems can provide those capabilities. Choose your payload, then choose a bus type (e.g. the physical body of the spacecraft) and then put it all together. The selection of the bus usually has a lot to do with what kind of propulsion system you have available, and a lighter bus gives you more propulsion options than a heavier one.

A lighter starship, by the same token, can get away with using a smaller impulse engine and a more efficient warp drive. Reducing the mass further might actually improve its combat maneuverability, and could also improve its thermal characteristics if the lighter materials absorb less heat.
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Old November 6 2013, 07:17 PM   #18
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Re: Density of star ships

The show spoke of "Duranium" being used for the hull, or as part of the hull. If duranium refers to depleted uranium (with their science completely depleted) that would make the outer shell of the ship responsible for a health percentage of the ship's mass. Combine that with the warp coils, the impulse engines, and things like the M/AM reactor and the majority of the ship might not be unusually "dense."


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Old November 6 2013, 09:30 PM   #19
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Re: Density of star ships

T'Girl wrote: View Post
The show spoke of "Duranium" being used for the hull, or as part of the hull. If duranium refers to depleted uranium (with their science completely depleted) that would make the outer shell of the ship responsible for a health percentage of the ship's mass. Combine that with the warp coils, the impulse engines, and things like the M/AM reactor and the majority of the ship might not be unusually "dense."


I figure duranium is actually the trade name for an alloy that uses a combination of rare metals (titanium, nickel, platinum etc) that are only plentiful in asteroids. Nickel-platinum alloys, for example, have shape-memory properties that allow them to deform hugely under mechanical stress only to return to their original shape when heated beyond a threshhold point; if Starfleet is using something like this in their hull plating, then "polarizing" it with an electric field might be a sneaky way of forcing those hull materials to constantly return to their original shape when subjected to mechanical stress. Better yet, an open-cell metal foam of nickel-platinum alloy would give you a material 90% lighter than solid metal while retaining almost all of its strength in the same volume, plus the benefit of being better able to deflect projectiles in hyper-velocity collisions (rather than shatter/spall into the compartment).

Even better, an alloy of nickel-titanium-palladium would have a mindblowing strength-to-weight ratio in addition to being able to trap some hydrogen in the matrix (palladium hydride) which would make it an ideal radiation shielding material. The same material in an open-cell foam could be fashioned into hull plates several feet thick that are still no heavier than ordinary sheetmetal.

Besides, we know that Starfleet uses a lot of tritanium in their construction too, which I can only assume is an allotrope of titanium (probably a glass).
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Old November 6 2013, 09:59 PM   #20
CorporalCaptain
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Re: Density of star ships

Nob Akimoto wrote: View Post
I'm curious why a starship should be compared to a conventional naval vessel for density. Is there some reason it needs to have a density of less than water? If we're going to talk about common sense, the material descriptions we're given about starships is that they're designed to withstand weapon impacts that destroys relatively dense things like iron-nickel asteroids with ease. Even assuming that say torpedo technology evolved significantly between 2293 and 2370, an unshielded Enterprise-A was taking torpedo hits that would presumably destroyed much larger asteroids with relative ease. In which case the hull materials being less dense than a combination of nickel and iron doesn't make a lot of sense. Indeed the requirements for a starship constructed in space (contra the absurdity of ST09) are probably more toward better thermal properties and maybe radiation shielding over things like lightness. There's simply no need for a starship that uses mass reduction technology to worry all that much about using high density materials for its hull.

There's nothing in canon or even official sources that suggest a 190,000 ton Enterprise, and there's evidence to suggest ships are, in general, heavier than water. There's no real reason for the compromises that naval vessels have to deal with in terms of hull density on a starship.
My only purpose in bringing up CVN-65 was simply to point out that the 300,000 metric ton figure given for the starship in the OP seems (IMO) implausibly too light (as is the 190,000 metric ton figure that FJ gave), because it's too close to the mass of a real world naval vessel of similar size.

The almost-million-ton figure given in Mudd's Women, that I'd forgotten about, sounds better, at the very least because it's larger than 190,000 metric tons.
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Old November 7 2013, 12:58 AM   #21
Masao
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Re: Density of star ships

Nob Akimoto wrote: View Post
There's nothing in canon or even official sources that suggest a 190,000 ton Enterprise
According to this page ( http://www.st-v-sw.net/STSWvolumetri...mozTocId859859 ) at a SW vs ST website (which agrees with Nob that Enterprise displaces a million tons), the 190,000 ton figure appeared in TOS writers guide, from where it was included in The Making of Star Trek and FJ's Technical Manual.

Anyway, I'm comfortable with having starships constructed like naval vessels and having similar densities. I've used that assumption in all my work. After all, lighter and less-dense ships should be easier to build and operate, and advanced materials should be lighter yet stronger than what we have now. But if any of you want to believe that Enterprise was 5 times as heavy, that's OK too.
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