Zan replied to me:
> I have a question. Is there any real point to having external structure
> on a space freighter at all, ball shaped or otherwise? Cargo holds and
> the like seem like a pretty useless idea in space.
Hello Zan,
there are a couple of answers to that question:
- Space is a hostile environment. Radiation, heat, cold, pressure,
and all that stuff. The square-cube relationship means that big
hulls have a clear advantage. Especially on a long flight, when
time to unload in insignificant next to the travel time, that
matters.
- As far as GURPS 3E goes, the grapples for external carriage are
quite heavy. Together with the extra mass for containers, we're
talking about a 10% loss or thereabouts for big containers. 20'
or 40' boxes are worse.
- Depending on the TL, it might be viable to do a surface landing.
Unless the TL is really high, that requires a hull.
- FTL engines are technobabble. They are rated for mass, but does
that mean shape is irrelevant in the setting? Cf the lanthanum
grids in Traveller.
- From a roleplaying perspective, there are advantages to a large
ship, with ventilation shafts to hunt alien pests or pirate
boarding parties.
Summarized, there are good reasons for non-container ships, just
as there are good reasons for container ships.
> Why not just a long bar with propulsion systems at the back and particle
> shielding in front. On the bar attach containers in a ring. Possibly
> multiple layers of containers.
If you attach containers to other containers, those boxes have to
be stressed to take not just their own mass but also the attached
loads. That makes the containers more expensive.
> Stations could have cargo loading decks which bring containers up to the
> ship. Attach a container, rotate the ship. Attach another container,
> repeat.
Why dock at all? In zero-G, position the containers in a circle.
the ship arrives, drops one formation of containers, moves into
position in the new circle, and little tugs nudge them into dock.
> Assuming large enough containers, passengers could simply live in a
> completely sealed container with its own power systems, life support,
> gravity, etc, and be handled like all other cargo. If they insist on
> dinner with the captain, transport tubes could be connected to their
> container from the crew cabins.
Several thoughts on that:
- The maintenance and supervision requirements increase if you
have 100 little power plants instead of a few big ones. Same
for life support.
- Redundancy can be expressed as extra percentages or as extra
units. For 8 people, I'd probably want three 10-person life
support systems. For 8,000 people, a dozen 1,000-person life
support systems might be enough. The reserve percentage is
lower, but the number of spare systems is high enough for
comfort.
- Passengers might not just want their Captain's Dinner, but
also recreation, sports, and so on. Are those separate
containers, or little additions in each container?
- Are there requirements for lifeboats? Evacuating containers
may be difficult.
So far, I have five 30,000-ton ships:
TL10: Container ship, one 20,000-ton container. The ship is
marginally landing-capable, but only without load.
TL11: Container ship, ten 2,000-ton containers. The ship is
not really landing-capable, even if it has the thrust
to mass ratio for it.
TL12: Enclosed ship. The ship is again unable to land. This
is a special case, an ark with 4,000 crew.
TL14: Enclosed ship, landing-capable. The fastest one so far.
TL15: Enclosed ship, landing-capable. The most efficient one
so far, by quite a margin, and not just because of the
high TL.
One measure for the efficiency of a space transport would be
tons of load (plus one ton per person) times parsec per day
divided by the cost in $M.
TL Type LWt Cargo Occ Cost Speed Notes Efficiency
15 Bulk Transport 30,000 22,498 20 $575M 3 120
14 Megafreighter 2,000,000 1,249,900 1,000 $56B 4 89
14 Bulk Transport 30,000 15,590 100 $1.3B 5 60
11 Bulk Transport 30,000 20,470 100 $788M 2 [3] 52
15 Light Transport 100 61.9 6 $2M 1 34
13 Light Transport 100 62.1 4 $4.3M 2 31
14 Light Transport 200 151.6 4 $6M 1.2 31
11 Light Transport 100 51.6 4 $4.4M 1 13
12 Bulk Transport 30,000 12,050 4,000 $500M 0.4 [4,5] 13
11 Freighter 3,000 1,756 40 $86M 0.4 8.4
11 Blockade Runner 30 4.5 5 $2.4 2 [5] 7.9
16 Light Transport 100 51.2 8 $30M 3 [1] 5.9
10 Bulk Transport 30,000 20,399 10 $1.2B 0.2 [3] 3.4
14 Scout 20 3.9 1 $3.2M 2 3.1
15 Scout 10 2.4 1 $3.5M 3 2.9
13 Scout 15 2.9 1 $1.9M 1 2.1
16 Scout 15 2.9 1 $10M 4 [1] 1.6
12 Scout 12 1.9 1 $1.5M 0.5 0.97
15 Exporation Cr. 300,000 59,975 250 $275B 4 0.88
10 Light Transport 100 19.4 6 $11M 0.24 0.55
12 Light Transport 100 24.6 4 $64M 1.2 [2] 0.54
11 Scout 10 0.9 1 $1.5M 0.4 0.51
15 Cutter 5,000 199 10 $3.3B 5 [6] 0.32
15 Cruiser 4,000,000 159,975 250 $2878B 5 [6] 0.28
10 Scout 10 0.3 1 $2M 0.2 0.13
[1] Expensive because of a teleport projector.
[2] Expensive because of a cloaking device.
[3] Externally carried container(s).
[4] Ark ship, considerably more crew than necessary.
[5] Cheaply made, which "doubles" efficiency.
[6] Warship.
Regards,
Onno
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