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Long post - RE: [OFFICIAL] Freighters/Merchants question

From: "B Lin" <lin@r...>
Date: Thu, 18 Nov 2004 12:47:48 -0700
Subject: Long post - RE: [OFFICIAL] Freighters/Merchants question

Actually, no. you don't need to disassemble and reassemble the modules
at every stop.

If you know which containers need to off-loaded and in what order, you
simply place the earliest containers to the outer edge, and later
containers towards the inside.	Like properly loading a delivery van,
you don't unpack and repack a van at every stop.  You may have to
re-arrange at some point as you pick-up spheres that are slated for
later delivery, but a 4-layer stack of spheres provides direct access to
29 spheres/modules out of 30 (4x4 (16), 3x3(9-1),2x2 (4) and 1x1 (1)),
the remaining 1 module in the center can be used for life support or as
the single "structural" sphere to hold the whole mass together. Larger
masses (a 5-layer pyramid has 55 units, a 6 layer pyramid has 91) will
have more inaccessable modules, but if you are shipping 91 at a time,
chances are that a large portion are being dropped at a single location,
in which case, entire layers are dropped off at once.

The advantages are that you aren't limited by the structure of the ship
- if a "standard design" ship has docking ports for 30 modules, you are
limited to shipping a maximum of 30 modules, if you want to ship 32,
then you need two ships.  If you are only shipping 10 modules, then you
are paying to move supporting structure for 20 modules.

If you argue that you can just "strap on" a couple more modules, you
then essentially have the sphere module ship, so why limit yourself in
the first place?

All the designs I have seen for modular freight ships have either
relatively small connection points (the small ends of containers
attached to a central core) or have large attachment points, but then
strap on containers to containers to achieve a reasonable number of
modules carried.  If you can PSB either design then the same reasoning
justifies the sphere design which has multiple small connection points
and straps containers to containers.

A pyramid design ensures that each component is connected to at least 2
other components and as many as 8.  If a single structure fails, unless
it is an outer component, there are at least two other components taking
up the slack.  Modern containers are rated to 24 metric tons of carrying
capacity, but must withstand being stacked up to 6 deep, meaning they
have to be designed to support over 150 metric tons (cargo + container
weight).  Obviously people don't worry much about a single container
failing and causing 150 tons to drop through the bottom of the ship. 
The structure of a future sphere will be designed to handle
"appropriate" amounts of stress, and like current containers, the owners
will be responsible for their structural integrity and liable for losses
due to the failure of their container.

The design of such freighters is to just move freight and that such
"commercial" freighters are not military ships, they will not be
designed to pull 10's of G's of acceleration, they are designed to move
the largest amount of cargo for the cheapest cost.  Military transport
ships may be built to a different design driven by a different set of
requirements (faster speeds, higher acceration, greater structural

For transport to ground side, you seem to be making the assumption that
a cargo module would be small enough to fit on a shuttle.  I was
imagining larger masses - each module massing 1000-5000 tons (full)
each.  I don't think it would be efficient to try to land 5000 tons of
cargo in a glider (for comparison a fully loaded 747 weighs 330 tons) . 
Each sphere could be packed with smaller "glider-friendly" modules of
10-100 tons inside.  If there is any sort of queue to get containers
down to the surface, then it doesn't matter as much that it takes time
to fully unload a sphere as the limiting step will be the availablility
of gliders. 

Modern container ships are only efficient at ports with the appropriate
facilties, and even then are limited by the number of cranes that can
reach the ship - I think large container ships can be serviced by 3-4
cranes, but it still takes days to unload a large container ship because
there are thousands of containers (I think the largest container ships
now carry about 6000 TEU's (twenty-foot equivalent units) each).  Future
modular containers will only be as useful as the environment they are
used in allows - for instance if your cargo is going to Backwater Planet
with just a small space station and no regular cargo surface shuttle,
then your glider designed module costs you extra money to transport with
no gain in use.  If your goal is to transport goods cheaply between
systems, then the additional cost of transporting modular structure
around that isn't utilized increases your transport costs.

Continuing to use the modern example for specialized environment,
container trucks are not the same as a standard haul tractor-trailer
trucks.  Container trucks have added equipment to lift, attach and
otherwise manipulate a container which can contain up to 24 metric tons
of goods, which is additional equipment and weight that is not necessary
if you are delivering goods to the local delivery store.  Most
containers are delivered to warehouses or manufacturing facilities,
where the large quantity of goods inside are unloaded, repackaged and
then delivered by more conventional means.

Massive modular cargo movements will tend to be between major ports,
with the facilities to manipulate large quantities of modules in and out
of the system.	It may take hours or days to unload a modular ship, but
that is not time wasted, as the freighter can re-fuel, grant shore-leave
or perform maintenance on the ship while modules are being shuffled

Larger freight companies may even maintain a fleet of extra engine
modules at major ports, allowing defective or low-fuel modules to be
switched out or extra modules added to a ship to increase its size
and/or speed.  Re-fueling might be as simple a plugging a new fuel
module on while pulling the empty off the other side. Or in a more
drastic maneuver the command and maneuver modules will be popped off
with their current crew and a new ship (command and maneuver modules)and
crew popped on and sent on their way. 

In addition, like modern large container ships, the large or super-large
modular ships will only ply major trade routes, where their efficiency
(full loads, massive quantities) can be realized.  You would be unlikely
to find any type of modular freighter plying the small trade routes on a
regular basis, partly because of lower demand, and the lack of
infrastructure to support a modular system.


-----Original Message-----
From: Scott Siebold []
Sent: Thursday, November 18, 2004 2:14 AM
Subject: Re: [OFFICIAL] Freighters/Merchants question

> Actually the sphere is the best shape for surface
> area to volume considerations.  If a cargo module
> will never have to sit on the ground, then there is
> no physical reason at all that they all shouldn't be
> spheres.  The only advantage blocky containers might
> have is that if the final packaging is a crate,
> which is blocky, then they would fit more
> efficiently in a blocky container.
So the spheres will have to be unloaded and reloaded
in space. Also each time a ship arrives it will have
to be disassembled and reassembled before it can
depart. Most of the spheres will not be accessible
in space if repairs are needed.

> The most efficient packing of spheres is hexagonal
> closest packing (basically a pyramid of oranges,
> although the mathematical proof of this apparently
> takes 300 pages) so a cargo ship may actually be a
> command module, a bunch of spheres in a pyramid-like
> shape, then an engine/fuel module at the base.  Each
> cargo module does double duty as both storage and
> structure.

So what you are saying is that your spheres will not
only have to be strong enough to support themselves
but also be strong enough to be used as a ships
structure. If one of the spheres structurally fails
then engine goes one way the crew compartment goes
another and the spheres go every way. With no repair
in transit let's hope that the manufacturer of the
shipping spheres did not cut corners to save money.

Let's try a short story:

The container ship Edward James which has space for
up to 32 containers (four rows of eight containers
formed around a central hub) is receiving a warning
signal from container 2-3 (second row third container)
of a leak (each canister has sensors to monitor it's
status and power is supplied to the canister to be
used as needed). One of the crew goes out and while
checking the container (all containers can be
finds meteorite damage which he is able to patch
(in any case damage to the container will not put the
ship at risk).

As soon as the ship gets to it's destination four
canisters are detached while three are picked up.
Some of the canisters on ship are moved to rebalance
the load and in few hours the ship is on it's way.

Two of the canisters are loaded one each on a laulan
(launcher and lander) for delivery to planet while
the other two are stored for transshipment. The
laulan are powered gliders on the way down while more
powerful engines are mounted to get them back into
Orbit. After the laulan lands the canisters are taken
off the laulan and loaded on a ground transport to be
taken to their final destination where the canisters
will be opened and unloaded.


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