[Spaceships] Passage Tubes? Stats? Cost?

[vicky_molokh]

Greetings, all!

SS1:42 mentions using a Passage Tube to connect two spaceships, and gives dimensions. How much would one such tube be in terms of cost, mass and DR for various TLs (primarily interested in TL9)?

Thanks in advance!

[ericthered]

We're looking at around 100 cubic yards of space. Or perhaps 100 square yards of material. Pages 75 and 76 of ultra-tech may help us with costs to fill that space.

Our options are:
Envirobag
Modular Environmental Cage
Pressure Tent -- in three sizes.

Each of the five options would provide its own point of data. The simplest extrapolation is the cage, of which we require 10. We pay $100k and haul around 2 tons.

I bet the tents give better numbers. And ones that change with TL.

EDIT: if we go with the envirobag being fairly roomy (7 feet long and 3 feet in radius), we get much cheaper. $12k, and 225 lbs if extrapolating volume. 4400$ and 85 lbs if we extrapolate surface area.

[a humble lich]

In third edition, passage tubes cost $1000 took 40 cf of space, and weighed 1000 lb and had a DR of 12. Armored passage tubes cost $1000 more, weighed 2000 lb more and had DR 20.

Hope that helps.

[ericthered]

That's 67 units to make the full tube. so 67,000 $ and 33.5 tons.

These numbers are all over the place.

[a humble lich]

No, those number were for the full tube. They took 40 cf of space when folded up not in use.

[Rupert]

The tube in Spaceships is ~30 yards long, and ~2 yards in diameter. The relevant characteristic for cost, weight, etc. would be surface area, plus a bit extra for the fittings at each end. An open cylinder of this size has an area of about 2 x 3.1416 x 30 = 190 yards^2, or ~1700 ft^2.

Relevant comparisons would be Envirobags (but they have insulation that a tube won't need), Pressure Tents (but they have air tanks and locks, so I'll ignore them), and Rescue Bubbles.

A sleeping bag or Envirobag probably has a surface area of about 35 ft^2 (4 yards^2). A rescue bubble can be walked in, so is presumably 5' or more in diameter, and thus has a surface area of about 80 ft^2 (9 yards^2).

This gives us costs and weights per square yard of:

     Bag          Bubble
TL   Cost  Wt.    Cost  Wt.
 9   $40   0.75   $88.9 0.444
10   $20   0.5    $66.7 0.333
11   $10   0.375  $44.4 0.222
12    $5   0.25   $33.3 0.167

It would appear that the bubble is made of lighter, but rather more expensive materials, which seems fair for something of its nature. For a passage tube that's intended to be light, sealed, and reusable (which a bubble isn't really), I'd be inclined to use the higher of both price and weight, giving this table for the tube:

 
TL   Cost  Wt.
 9   $17K  140
10   $13K   95
11   $8.5K  70
12   $6.5K  45

I'd chuck a bit more on for the fittings at each end:

Passage Tube
TL   Cost  Wt.
 9   $20K  200
10   $15K  150
11   $10K  100
12   $7.5K  75

Compared to most spaceships, the cost is almost nothing, and the weight likewise. I've always included them as standard equipment that comes with an airlock. Thus a new, or well maintained ship will have one per lock. An old ship, not always kept up to spec, might well not have any, or have one much-patched and sometimes leaky one. If the PCs don't think to check before blasting off into the wild blue yonder, their trip could be more exciting than they anticipated.

EDIT: I forgot - DR1, like a rescue bubble. Actual armour would add quite a bit to weight, especially at lower TLs. Hmm. Using UT's armour rules, and assuming a person has a surface area of about 20 ft^2, a layer of standard thickness ballistic cloth (8 lbs, $1200 for a suit) would add 8 x 1700 / 20 = 680 pounds in weight, and $102K in price. We can probably halve the cost, because this doesn't have to be cut to fit a human body shape, but the weight wouldn't change. Making it thinner would lighten and cheapen the armour as usual. Any armour will add considerably to the storage volume, as it changes from a thin tube to a rather thicker and less flexible one.

I'm happy to assume a DR1 system as the standard, because no sensible DR will keep out debris hitting at the speeds you get from radically different orbits, etc., and a baggy outer skin of mylar+foil will do for micrometeors and the like, while DR1 is enough to survive normal bumps and scrapes.