I was going through NIFT's Full Thrust Weapons & Defences Archive and came
upon the entries for Gravitic Shepherd Buoy & Battle Debris. With a debris
field supported by a Gravitic Shepherd Buoy, to my mind, being a much more
reliable area denial weapon than the mines first presented in FT rules book, I
came up with an idea for a space construct to be
encountered during a campaign game - a means of protecting civilian
ships at anchor around a world, and a mothballed reserve fleet from
hit-&-run raids - A Debris Reef Harbour.
A Debris Reef Harbour will usually be encountered in systems that border
potentially hostile intersellar nations...
Systems that are home to a nation's reserve fleet...
And systems that enjoy extensive asteroid mining operations.
To set up a debris reef harbour in a play area, you will need an unopened soda
can (or small jar or water glass or tin can or cylindrical object) with a base
that is the game scale equivalent of at least 4MU in circumference...
some adhesive tape and some string that is a MINIMUM of 16MU in length.
Attach the length of string to the side of the can with tape near its base and
place the can on the play area where the center of the harbour should be, with
the side with attached string facing where you want the harbour entrance to
be.
Gently pull the string taut, and place a marker where the string ends.
Now, without dragging the can from its central position or allowing it rotate
with the motion, move the end of the taut string 2MU either clockwise or
counterclockwise [your choice] and place another marker.
Repeat again & again, until you've laid markers in a circle around the can,
with the string being wrapped around the base of the can. Continue until the
string has been wrapped around the base of the can AT LEAST TWICE.
When you remove the can from the play area, and you did everything correctly,
you will find a spiral line of markers running in a shrinking circle. This is
the template for where you are to set up gravitic shepherd bouys that support
the debris reef.
In game terms, the debris reef is set up by gathering, into a
quick-release net, the game scale equivalent of at least 40 ship mass of
derelict starship parts and/or asteroid mining waste, with a
time-activated gravitic shepherd bouy in the center. The net is towed
to the proper location in space, decelerated to 0mu velocity, and the contents
released. When the debris has drifted out to 2mu, the bouy activates and locks
the debris in position.
The completed reef will be a 6-8mu wide debris asteroid belt, with a 2mu
wide open channel running the circumference of it. The channel allows for the
passage of shipping into the harbour without damage from debris strikes. The
body of the reef is intended as a defence against salvo missles fired from
outside the harbour entrance. A salvo missle group trying to penetrate a
debris field rolls a number of dice equal to the
DENSITY of the field [4-5=1 hit, 6=2hits+reroll] with each hit
destroying a missle for every FULL 6mu of range. So, an ER salvo firing
through a density 6 field has a cat's chance in Hell of doing damage to
anything on the other side! And trying to fire the salvo through the channel
to the harbour within will fail because the transverse length of the channel
exceeds 48 mu, if using the minimum harbour radius of 16 mu. (At last, a
practical use for the concept of PI)
But in order to make sure that density of the WHOLE reef is uniform, the
density of the debris field groups will have to TAPER, so that attacks don't
just occur at the harbour entrance, where there is only one line of debris
fields, instead of the opposite side, where there are two.
When setting the density of the debris fields, start at the channel entrance
with a density of 2. For the first 3rd of the way down the
reef, begin to increase the density to 6-8. The second 3rd of the way
should hold at 6-8. The final 3rd should taper back to density 2 at the
end of the channel.
However, MT missles escorted by fighter groups flying through the harbour
channel still pose a real threat to shipping in the harbour. That's where
another system I found at NIFT's FTWeapDefArchive is needed
- the Area Defence System - found in INTERCEPTION. Mounted on STL
barges, spaced 6 mu apart, all along the inside wall of the inner half of the
reef, they produce overlaping arcs of fire, forcing hostile fighters to run a
gantlet of defence fire the length of the harbour channel. And with a harbour
channel that is at least 48 mu in length, even a fast fighter group starting
its turn at the mouth of the harbour channel, and using its second movement,
will still be in the channel at the end of the turn, vulnerable to overlapping
defence fire.
The Debris Reef Harbour isn't a perfect defence against attacks to
anchored shipping. Long-range beam & pulse torpedo fire can still
penetrate the reef. The channel is a shallow curve that doesn't take
into account the 12-sided facings involved in writing movement orders,
so movement through the channel can only safely be negotiated at a very
slow speed [1-2mu per turn], so there needs to be a defending force
outside the harbour if a large fleet attacks. And though a density 8 debris
field is a deadly hazard to small ships, a battleship or dreadnought can plow
through at low speed without even taking a threshold check.
Even though a debris reef harbour is vulnerable to attacks by big ships with
big guns & pulse torps, it does provide a excellent defence against
hit-&-run raids mounted by fighters and fast small craft firig salvo
missles. And even though it takes a ship in excess of 48 turns just to enter
the harbour, civilian shipping would generally feel more comfortable protected
by the reef than anchor naked against the fathomless void.
On its own, a debris reef harbour has little effect on a potential battle
ground other than as a large hazard to movement, but since a debris reef will
usually only be encountered in systems that have major trading ports and naval
bases that support the reserve fleet, their presence will indicate that the
battle is not just another random naval engagement, but a major operation that
will determine the fate of a strategic objective.
I invite your comments.
> A Debris Reef Harbour will usually be encountered in systems that
Not sure if your intending that it has to be 'all of the above', but I would,
as it seems to me that it would take a heck of a lot of transport, as in
prohibitive, to move that much material any appreciable distance. Remember, in
reality, you're talking about a sphere, though the spirals are in two
dimensions.
In fact, if the mining process wasn't geared to launching trailings to be
concentrated in the staging area, even the vast distances that actually occur
in asteriod fields as we know them would probably be prohibitive.
Sorry, I'm always a little suspicious of an idea that sounds like something
for nothing... ;->=
However, the mechanism sounds fascinating; I'll have to find an appropriate
pop can to give it a try!
The_Beast
Remember that in space, distance is nothing if you have the time. If you're
willing to wait years, then shoving a gigantic mass at relatively slow speeds
will get it there with a minimum of energy at either end,
since there is very little if any loss of velocity while traveling - so
while a commercial tug may be limited to pulling a few megatons across
the system in a a couple of hours/days, it may be able to shove a
gigaton on a slow trajectory across system that takes months or years to
arrive.
Just look at all the space probes - the vast percentage of the energy
used for space probes is to get them out of Earth's gravity, but once in
space, they can gain velocity using gravity slings. They are then unpowered
for the rest of their flight to Saturn, Jupiter etc. At the far end, a small
deceleration burst (30 minutes or so) puts them into the proper orbit. It
takes years (sometimes almost a decade) but they get there eventually.
After all, a prime sci-fi ideal is that you shove entire asteroids to
where you want to process them. So instead of going out to the asteroid
field and building a refinery, you shove (small - 5-10 km) asteroids
towards the spot in the system where you want the eventual harbor, capture
them and then process them. If the processing plant is the center of the
location of where you want the debris, then transportation after refining is
essentially nil. You could schedule asteroids to arrive "just in time" for the
refinery, although your "pipeline" might be years long depending on how cheap
you were and how far the asteroids were from the site.
Economy of bulk is very important, as it is today - shipping in giant
containers thousands of miles across the ocean is cheaper than transporting
the same bulk over the same distance in separate trucks.
It takes longer with ships, but is much cheaper per ton/mile. You just
need to be able to afford the time it takes.
--Binhan
[quoted original message omitted]
> Remember that in space, distance is nothing if you have the time.
Getting them to stop, unless in orbit or impacting a body, can be another
matter altogether.
However, even a gigaton of pulverized rock would make a fairly small 'shell',
and I'm assuming we're talking fairly large pieces.
The_Beast
If you are already assuming that a gravitic bouy can hold together a large
mass of small objects, then the debris already bundled up. Then accelerating
or decelerating the mass is just a matter of a tug latching on to the bouy and
applying force. It doesn't have to be much if you're not in a hurry, you can
take weeks or months to decelerate the mass if necessary.
But I was thinking more along the raw material lines - whole entire
asteroids, with either power plants or tugs attached to the surface. If fusion
power is cheap, then weeks or months of low but continual thrust will provide
all the velocity you need.
If you can afford the wait, then you can send the asteroids at a lower
velocity to cut down on the energy to get them moving and to stop them at the
other end. In effect, as long as you have energy, you can do it as cheaply and
slowly as you want.
I would think the debris harbor would be a major construct that
governments would be willing to invest years or decades developing - for
instance if there major military shipyards or "foundries" for critical
military materials, then these facilities, as a by-product of their main
activity would slowly build up such debris fields or inadvertantly build them
up and police them to keep the shipping lanes clear.
As to the effort and cost, the precendent would be the Great Wall of
China - no sane person would expect such a structure to be built as the
sheer cost and bulk of the project is mind-boggling, but with millions
of workers and hundreds of years, such a structure was completed. Whether or
not it fulfilled it's protective purpose is a different point.
--Binhan
[quoted original message omitted]
> I would think the debris harbor would be a major construct that
Er, I thought my point WAS that it would be a major effort, even attempted
on the cheap, long term. ;->=
However, I'll admit you won't need each transport 'unit' in place for the
complete trip. I'm an old fan of BattleFleet Mars, remember.
> Whether or not it fulfilled it's protective purpose is a different
My impression is the that the Great Wall did a damn fine job. Perfect? No.
The_Beast
Well, your first post regarding the transport cost did have the word
"prohibitive" in it...:)
[QUOTE]
Not sure if your intending that it has to be 'all of the above', but I would,
as it seems to me that it would take a heck of a lot of transport, as in
prohibitive, to move that much material any appreciable distance. Remember, in
reality, you're talking about a sphere, though the spirals are in two
dimensions.
[QUOTE]
My argument was that it's not prohibitive, as long as you have the time. And
that the distance factor was moot since your only real energy cost is starting
the stuff moving and stopping it at the end, not how far it travels.
Now if you needed this up in a year or something, then the transport cost
probably would be prohibitive.
--Binhan
[quoted original message omitted]
> Well, your first post regarding the transport cost did have the word
And, as the material is assumed scattered over a large area, then you have
transport logistics for the transport 'units', getting the
pusher/catapult/low output thrusters to the various points of origin. I
still see even the long term program, while less energy intensive, still
"prohibitive".
Also, one bit of equipment used for a hundred years can come on the books
equivalent in cost to a hundred pieces of equipment used for one year, and
then free for other uses for the next ninety-nine.
I did include that the asteroid mining process could have ejection of 'dross'
as part of the shell aggregation program as a necessary condition, but even
that adds cost to that process. Yes, the amount of material in the belt is
amazing, but it's 'no cost' is an illusion.
Explosives, such as the mines these replace, tend to be cheaper just be cause
you get bang for your buck, and that includes being smaller and easy to
transport, relatively.
Why do I feel like we're discussing the meaning of 'is'? ;->=
How about we leave the reef as nothing useful for instant cheap
screens/armor, the way a mine field might. I was merely arguing it
should be a rare option.
The_Beast