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Old 02-21-2019, 01:15 PM   #31
tshiggins
 
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Default Re: Spacecraft as homes [Spaceships]

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Originally Posted by Agemegos View Post
And also splendid radiation shielding for the biowell (ion-storm shelter).
I thought something similar. I mean, if you need a radiation storm shelter, and you need a water supply and you need a way to scrub CO2, why not combine them in one large tank?

Have a transparent shelter suspended in the center of the tank with lights that produce some UV. Have a lock in the shelter provide access to the tank with SCUBA gear. Put in some water toys, and give the crew something to do in the algae tank while waiting for the all-clear.

Tropical fish may qualify as a bit of an indulgence, though....
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Old 02-21-2019, 06:46 PM   #32
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Default Re: Spacecraft as homes [Spaceships]

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Originally Posted by Rupert View Post
Assuming that the 'TL7 Steel' of Spaceships is RHA and DR70/inch (dDR7), I get three armour systems covering 5,250 square feet. That's enough to coat a sphere a little over 40 feet in diameter, with a volume of 35,770 cubic feet. At 1,000 short tons weight that's a density of ~56 lbs/ft^3, or about 0.9 that of water.

However, such a sphere would only have a size modifier of SM+7 (+5 for length 11-15 yards, +2 for being a sphere).

A SM+10 sphere needs to be 31-50 yards in diameter, and thus have a volume of ~421,000 ft^3 to ~1,767,000 ft^3, and a density of 4.75 lbs/ft^3 to 1.13 lbs/ft^3 (0.076 to 0.018 that of water). That's a bit more that the density of liquid hydrogen to rather less.

So actually, if spaceships are as big and low-density as their SM to tonnage ratio suggests, they are being given a lot more dDR (about ten times in this example) than they should be. If they have the right dDR, they are being made easier to see and hit than they should be.

Feel free to check my maths. I'd be happy to be wrong one way or the other.
Ships in GURPS spaceships are treated as effectively just cylinders with a density based on a shipping ton (20lbs a cubic foot).

At work on my only break I'm gonna get given how cray-cray it is so I'll show the math when I get home in about 3hr or so hours.
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Old 02-21-2019, 06:47 PM   #33
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Default Re: Spacecraft as homes [Spaceships]

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Originally Posted by tshiggins View Post

Tropical fish may qualify as a bit of an indulgence, though....
Depends. Aren't they the first choice for an urbanite's aquarium?
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Old 02-22-2019, 02:48 AM   #34
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Default Re: Spacecraft as homes [Spaceships]

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Tropical fish may qualify as a bit of an indulgence, though....
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Old 02-22-2019, 06:05 AM   #35
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Default Re: Spacecraft as homes [Spaceships]

Reading The_Ryujin's post led me to check my maths:

Quote:
Originally Posted by Rupert View Post
Assuming that the 'TL7 Steel' of Spaceships is RHA and DR70/inch (dDR7), I get three armour systems covering 5,250 square feet. That's enough to coat a sphere a little over 40 feet in diameter, with a volume of 35,770 cubic feet. At 1,000 short tons weight that's a density of ~56 lbs/ft^3, or about 0.9 that of water.

However, such a sphere would only have a size modifier of SM+7 (+5 for length 11-15 yards, +2 for being a sphere).
Well, I made a maths error here. I accidentally calculated everything as if a SM+10 spaceship was 1,000 tons when it should weigh 10,000 tons.

Thus that sphere covered with dDR10 steel (~1.4" thick, weighing ~57 pounds per ft^2 covered) has a surface area of 52,500 ft^2. It therefore has a diameter of about 130 feet, and a volume of ~1,131,130 ft^3. This gives a density of about 18 lb/ft^3, or 0.28 times that of water (and four times that of liquid hydrogen).

This sphere is has a diameter that fall in the SM+8 range, and has +2 SM for being a sphere and is thus SM+10.
Quote:
A SM+10 sphere needs to be 31-50 yards in diameter, and thus have a volume of ~421,000 ft^3 to ~1,767,000 ft^3, and a density of 4.75 lbs/ft^3 to 1.13 lbs/ft^3 (0.076 to 0.018 that of water). That's a bit more that the density of liquid hydrogen to rather less.
The error was repeated here, giving densities 1/10th what they should be (47.5 to 11.3 lb/ft^3 or 0.76 to 0.18 that of water). These range from over twice liquid hydrogen to eleven times the density of liquid hydrogen.

Quote:
Feel free to check my maths. I'd be happy to be wrong one way or the other.
Turns out that I was. Spaceships are roughly the density of the traditional general cargo 'ton' (20 lbs/ft^3 or 100 ft^3 per ton).

A spaceship with the density of liquid hydrogen would need three times the armour mass to get the same level of protection, and should be considered +1 SM bigger than its mass suggests for any purposes where outright size matters (e.g. getting shot at).
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Old 02-22-2019, 10:53 AM   #36
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Default Re: Spacecraft as homes [Spaceships]

Welp, a little latter then I planned but here it is >.>


Ok, as I said in my last post the ships in Spaceships were originally figured as simple cylinders (probably to let David use some of his work from Transhuman Space to help ease his workload).


This much is actually stated in first Spaceships book:

Quote:
Originally Posted by GURPS Spaceships, pg. 9
An average for a typical unstreamlined cylindrical spacecraft, or for many complex shapes like saucer-boom-and-pod designs



As for the density he used, that much he has stated in several forum posts. This one isn't the best quote but I had trouble finding a better one for some reason. Note that in my originally post I mistakenly called it a shipping ton.


Ok, now that we know the that the ships are treated as cylinders, the length for a given sized ship and how to figure their volume as well as their weight we can figure the radius of their ends caps there therefore their surface area.

Let's use the SM +5 hull for this example which has a mass of 30 tons (which means each system weighs 3,000lbs) and a length of 45ft. Now to figure it's volume we take the fact that 20lbs per cubic feet equals 100 cubic feet per ton which means it has 3,000 cubic feet of internal volume.

To find the radius of the end caps we just have to divide it's volume of 3,000ft^3 by it's length of 45ft and then divide the quotient by Pi and then find the square root of that quotient which is ~4.6.

So now with the height and radius we can figure the ships surface area or (2 × Pi × 4.6 × 45) + (2 × Pi × 4.6^2) which give us a area of ~1,434ft^2.

Ok, now as you suggested it's a pretty good guess that TL7 Armor, Steel is RHA with a DR of 70 and weight multiplier of 0.56 and one system of Armor, Steel gives DR 10 on a SM +5 ship. IF we divide the ships surface area by 3 we get ~478ft^3 per ship section. Multiply that by 10 × 0.56 and we find that enough steel to give one section of the ship DR 10 weights ~2,676lbs which is right in the neighborhood of the needed 3,000lbs per system (in fact you get even closer if you round the radius of the ship up to 5ft even).

In this case a spherical ship with the same volume would have roughly 3 times the DR for the same mass! Of course there are downsides to spherical hulls such as cost do to the increase waste in making anything circular but that might not be a problem at high TL's do to how advance 3D constriction techniques are likely to be by TL10 or definitely 11.

Of course you can use to figure how DR would be effected by making the hull any shape you want with a little extra math though this is of course far more complexity then this system was built in mind with.

Of course this being me we're talking about, I did a blog post were I pretty much tear apart the Starships system and let you play with it's gooey, gooey innards to your hearts content heh.
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Old 02-22-2019, 12:49 PM   #37
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Default Re: Spacecraft as homes [Spaceships]

Of course, such a spacecraft could not realistically have 1.5 metric tons of liquid hydrogen per component, as the volume of the liquid hydrogen would be around 20 cubic meters (over 700 cubic feet).
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Old 02-22-2019, 01:14 PM   #38
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Default Re: Spacecraft as homes [Spaceships]

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Originally Posted by The_Ryujin View Post


Ok, now as you suggested it's a pretty good guess that TL7 Armor, Steel is RHA with a DR of 70 and weight multiplier of 0.56 and one system of Armor, Steel gives DR 10 on a SM +5 ship. ]
Sorry if you cleared this up somewhere else but I couldn't follow your process. The thing is that "normal" in Spaceships is 1 system of Armor per segment or 3 per ship. To get by with just 1 system ypu'd have to be using a smaller systems rule.

Again sorry if I just ddin't read you right but I really ciouldn't follow what you were doing.
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Old 02-22-2019, 02:06 PM   #39
Rupert
 
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Default Re: Spacecraft as homes [Spaceships]

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Originally Posted by Fred Brackin View Post
Sorry if you cleared this up somewhere else but I couldn't follow your process. The thing is that "normal" in Spaceships is 1 system of Armor per segment or 3 per ship. To get by with just 1 system ypu'd have to be using a smaller systems rule.
That's why they divide the area by three - to account for an armour system only covering 1/3rd of the ship.
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Old 02-22-2019, 02:19 PM   #40
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Default Re: Spacecraft as homes [Spaceships]

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Swimming Pool [10]: Though this uses up ten cabin equivalents of capacity, this is only a small body of water, about the same volume as one single cabin. It also provides filtration and cleaning facilities, as well as one or two cabin's worth of space for changing or storage.

In ships without artificial gravity, this takes the form of a zero-g water chamber, and includes tethered breathing apparatus and a kind of airlock.

With artificial gravity, the room is equipped with pumps, shutters, and ventilation systems designed to avoid having several tons of water sloshing around in case of gravity failure or rapid acceleration.

Either way, it's a decadent indulgence.
I like this one. Makes me think of schlock mercenary's longest lasting ship. The strip likes to end with a punchline, and the tendency of the ship to flood itself is a recurring source of humor. As is the fact that the current owners don't actually like swimming, but they got the ship second hand, along with its quirks.

A ship for truly aquatic creatures would need a lot of water.
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