Re: Spelljamming speed, and invisibility

In <URL:news:local.spelljam> on Sat 04 Mar, Paul Westermeyer wrote:
> Just a few questions and thoughts for the list.
> 
> Can ships see each other while at spelljamming speed?  The canon 
> implies yes, we have numerous examples of ships following each other 
> at spelljamming speed in the novels and the rulebooks.  Spelljamming 
> speed is extremely fast ( ?????) and I would think seeing another 
> ship with the naked eye would be difficult, but I think possible.

Overdrive is 1au/day, which is roughly 100 million miles per day.
Roughly 4 million miles per hour. Unless ships are going on near
identical courses, so they have very little relative velocity,
they wont see each other.

Another way to look at it is to say that if it takes 1/20 of a
second for your eye to spot something, in that time a ship in
Overdrive will have done about 58 miles. Now, the only atmosphere
distorting your view is your ship's air envelope, and there is
generally not a lot of 'clutter' around that you need to pick the
ship out from, but...

There is a good chance that you could blink and miss a ship
flying at Overdrive speed past you. And, even if you did see it,
how good a look would you get?


These are Tech devices, but you could easily do these as spells
or magic items:

Approach Alarm: is activated by any ship approaching through
space to within 5k yard (10hex) radius. The ship may be any size,
and is detected even if invisible. Only non-living things are
detected, not creatures. Works by detecting ethereal and
gravitational disturbances, which for this relatively crude
sensor are masked by the life aura of living creatures. Requires
1gpwt of mithral for coils. Pseudo Arcane. Passive Sensor. Uses:
1ep/turn. Weight: 500gp.
Level: 4th.

Beacon: shows up on a Planetary Display. Works by emitting a
gravitational and ethereal signal. Requires 1gpwt of mithral for
coils. Pseudo Arcane. Uses: 1ep/turn. Weight: 100gp.
Level: 4th.

Planetary Display: produces a 2D visual image of all astronomic
objects Class B or larger within the current sphere, less than
Class B can be entered by hand. Also shows all objects with a
Beacon. This only works in systems with concentric orbits. The
display is on the equivalent of a Video Monitor, and a simple
control panel allows entry of extra details, which can be stored
on the equivalent of an integral Recorder, and will be shown the
next time return to this sphere. Works by detecting gross
ethereal and gravitational disturbances. Requires 5gpwt of
mithral for coils. Pseudo Arcane. Passive Sensor. Uses: 2ep/turn.
Weight: 1000gp.
Level: 5th.

Tactical Display: using 20'+ long antennae detects all objects in
space more than 8ft diameter, within 10k yard (20hex) radius, on
a 3D mental display, via an Interface Helmet. The image is
transmitted to the helmet via the equivalent of a Visual Comm
Mesh and a Coder. Works by detecting ethereal and gravitational
disturbances. Pseudo Arcane. Cost: x2. Uses: 6ep/turn. Weight:
1000gp+antennae.
Level: 5th.

Interface Helmet: receives 3D images to display via the
equivalent of a Mind Display, via the equivalent of a Visual Comm
Mesh and a Coder. These images typically come from a Tactical
Display or a Spelljammer Detector. Note that a Mind Display does
not give the full control capabilities of a Mind Interface. Long
use of this can be very tiring. Pseudo Arcane. Cost: x2. Uses:
6ep/turn. Weight: 100gp.
Level: 5th.

Spelljammer Detector: using 40'+ long antennae detects all
objects man-sized or greater in space, within 20k yard (40hex)
radius, on a 3D mental display, via an Interface Helmet. The
image is transmitted to the helmet via the equivalent of a Visual
Comm Mesh and a Coder. Works by detecting ethereal and
gravitational disturbances. Pseudo Arcane. Cost: x2. Uses:
6ep/turn. Weight: 1000gp+antennae.
Level: 6th.

Strategic Display: produces a 3D low-light visual image, up to
3"rad, of all astronomic objects Class A or larger within the
current sphere. Also shows the orbital path and colour, and the
current location. The display is the equivalent of a dim Holo Air
Display, and the sensor system is a more sophisticated version of
the Planetary Display. Works by detecting gross ethereal and
gravitational disturbances. Requires 5gpwt of mithral for coils.
Pseudo Arcane. Passive Sensor. Uses: 6ep/turn. Weight: 1000gp.
Level: 6th.


These all work by detecting ethereal and gravitational
disturbances, and more fancy versions, particularly planetary
mounted, could spot things at far greater distances.

If you want to follow another ship, slip something like a Beacon
on board, and use something like a Planetary Display or a
Strategic Display.

I'm sure various skrying spells would work as well, up to Find
The Path. The SJ equivalent of the Figurine of Wonderous Power:
Onyx Dog, which can track things through wildspace?


> This weans we should think of SJ speed more like Star Trek's 
> Warpspeed then Star Wars' hyperspace. 

So, what are you going to use as Long Range Sensors?


> This would also make coordinated fleet movement much easier and thus 
> more common.

If the Fleet wants to stay together, I'm reasonably sure this
could be managed.


> That in mind, I've been considering cloaking helms and ship 
> invisibilty spells.  There is a spell called 'Ship Invisibility', I 
> think it's 4th level, in an issue of _Dungeon_ magazine (an adventure 
> set in the Sea of Fallen Stars on Toril, dealing with pirate 
> treasure).  That spell's main limitation is that the ship still 
> displaces water, so a ship shaped hole appears in the water, 
> difficult to see from a distance, but it would be noticeable upclose. 
> My players (crew of the Oathtaker, detailed on Beyond the Moons) used 
> that spell alot (they ran through the _Dungeon_ adventure before 
> entering space.)
> 
> So, how is ship invisibility limited in space? I think gravity 
> fields.  The ships still drop each other to tactical speed when 
> within 10 hexes, so if you drop to tactical speed yet see no asteroid 
> or ship near which can explain it, then it might be you are being 
> stalked by a cloaked/invisible ship.

Might I suggest that a skilled Helmsman could _feel_ at least a
general direction for what caused the ship that they are Helming
to drop out of Overdrive?

Of course, if that ship is fast it wont stay there very long!


> This would explain an event in _The Maelstrom's Eye_ where the scro 
> use powdershot from jettisons to detect two cloaked IEN men-o-war and 
> manage to destroy one. This seems clever on the surface, but if you 
> have no idea where they are if they are near, in somewhere as vast as 
> space you would likely waste all your powder without ever detecting a 
> cloaked vessel.  But if the gravity field thing works, then the scro 
> knew the elves were near when they unexpectedly dropped to tactical 
> speed.  It says the elves had 'moved in for a closer look' just 
> before the attack.

Look at WWI and WWII submarine warfare, and how people handled
the problems of 'invisible' ships. Q ships that tempt an attack
are one answer. Hunter-killer packs.

An item that allows See Invisible line-of-sight is another
answer, or even some potions of See Invisible, to be drunk once
you are suspicious.

A pet Phase Spider on a dureum-washed chain (dureum also extends
on to the ethereal, preventing its escape), which sets off an
alarm when something invivible comes close?

On some worlds if you go Invisible, then you can see other people
and things that are invisible. How about keeping an invisible
Basilisk in a cage? [grin]


> Comments?

-- 
Dreamer
dreamer@??????.?????.??.uk
http://www.romsys.demon.co.uk/