Steve Jackson Games - Site Navigation
Home General Info Follow Us Search Illuminator Store Forums What's New Other Games Ogre GURPS Munchkin Our Games: Home

Go Back   Steve Jackson Games Forums > Roleplaying > GURPS

Reply
 
Thread Tools Display Modes
Old 09-02-2017, 01:29 PM   #1
vicky_molokh
GURPS FAQ Keeper
 
vicky_molokh's Avatar
 
Join Date: Mar 2006
Location: Kyv, Ukraine
Default [Spaceships] Passage Tubes? Stats? Cost?

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!
__________________
Vicky 'Molokh', GURPS FAQ and uFAQ Keeper
Also, GURPS Discord is a nice place for (faster) Q&A and overall GURPS dicussion.
vicky_molokh is offline   Reply With Quote
Old 09-02-2017, 02:01 PM   #2
ericthered
Hero of Democracy
 
ericthered's Avatar
 
Join Date: Mar 2012
Location: far from the ocean
Default Re: [Spaceships] Passage Tubes? Stats? Cost?

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.
__________________
Worlds Beyond Earth -- my blog

Last edited by ericthered; 09-02-2017 at 02:24 PM.
ericthered is offline   Reply With Quote
Old 09-02-2017, 02:21 PM   #3
a humble lich
 
Join Date: Jun 2017
Default Re: [Spaceships] Passage Tubes? Stats? Cost?

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.
a humble lich is offline   Reply With Quote
Old 09-02-2017, 02:27 PM   #4
ericthered
Hero of Democracy
 
ericthered's Avatar
 
Join Date: Mar 2012
Location: far from the ocean
Default Re: [Spaceships] Passage Tubes? Stats? Cost?

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

These numbers are all over the place.
__________________
Worlds Beyond Earth -- my blog
ericthered is offline   Reply With Quote
Old 09-02-2017, 03:19 PM   #5
a humble lich
 
Join Date: Jun 2017
Default Re: [Spaceships] Passage Tubes? Stats? Cost?

No, those number were for the full tube. They took 40 cf of space when folded up not in use.
a humble lich is offline   Reply With Quote
Old 09-05-2017, 12:26 PM   #6
Rupert
 
Rupert's Avatar
 
Join Date: Aug 2004
Location: Wellington, NZ
Default Re: [Spaceships] Passage Tubes? Stats? Cost?

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:
Code:
     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:

Code:
 
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:
Code:
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.
__________________
Rupert Boleyn

"A pessimist is an optimist with a sense of history."

Last edited by Rupert; 09-05-2017 at 12:42 PM.
Rupert is offline   Reply With Quote
Old 09-05-2017, 12:58 PM   #7
Anthony
 
Join Date: Feb 2005
Location: Berkeley, CA
Default Re: [Spaceships] Passage Tubes? Stats? Cost?

Weight actually scales in part with volume, that is probably not very interesting on the scale of a passage tube.

In general, the force trying to split apart a circular tube is (tube radius) * (pressure within tube) * (distance over which you are measuring) -- i.e. if the tube is at 0.2 bar (about right for pure oxygen) and a 1m radius, the force trying to split the tube walls is 20,000N/m. If the tube walls have a strength of 200MPa, they need to be 0.1mm thick, and the total wall volume is 6.3e-4m^3/m; assigning a convenient density of 1600kg/m^3, that's about 1 kg/m, or 27 kg (about 60 lb) for the entire tube. This can be adjusted somewhat based on materials and desired safety margin.

Note that it can't be collapsed unless the air is drained from it. Based on my experience with collapsing tubes, it's probably around 5% volume when collapsed.
__________________
My GURPS site and Blog.
Anthony is online now   Reply With Quote
Old 09-07-2017, 11:59 AM   #8
Varyon
 
Join Date: Jun 2013
Default Re: [Spaceships] Passage Tubes? Stats? Cost?

Armor cost and weight wouldn't be too difficult to work out, using the armor design articles from Pyramid. You're looking at 1700 sf of fabric. There could be a discount for not needing any basic tailoring, but I think it would probably be too small to worry about. At TL 9 you're probably using magnetic liquid armor (high-end reflex armor), for 1088 lb and $217,600 per point of all-around dDR (dDR is doubled against piercing and cutting attacks). At TL 10, you'd use bioplas, for 765 lb and $459,000 per point of all-around dDR (dDR is tripled against piercing and burning attacks). At TL 11, you'd actually still be using bioplas, but at half the price. At TL 12, you'd switch to energy cloth, for 238 lb and $119,000 per point of dDR.

There may be a limit to how thick such an armored tube can get before it's unable to be properly retracted, which will result in some sort of maximum DR for each of the above materials, but I'm not certain.
__________________
GURPS Overhaul
Varyon is offline   Reply With Quote
Old 09-08-2017, 04:33 PM   #9
fredtheobviouspseudonym
 
Join Date: May 2007
Default Re: [Spaceships] Passage Tubes? Stats? Cost?

Quote:
Originally Posted by Varyon View Post
There may be a limit to how thick such an armored tube can get before it's unable to be properly retracted, which will result in some sort of maximum DR for each of the above materials, but I'm not certain.
For paranoid space/starship owners you could have nested tubes -- like a hose inside a tire -- each one of which folds separately. Would take up a lot of space as the outer tube would have to fold into a toroidal storage volume around the inner tube's storage area (itself around the hatch).

But it would make the likelihood of puncture (requiring two simultaneous punctures of armored and presumably-self-sealing tubes) very unlikely.

Oh, yeah -- and wear a form-fitting spacesuit with pull-on flexible helmet when you're in the twin tubes.
fredtheobviouspseudonym is offline   Reply With Quote
Reply

Tags
docking, passage tube, spaceships

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Fnords are Off
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 12:40 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2017, vBulletin Solutions, Inc.