Re: Spelljamming speed, and invisibility

This is such an interesting topic, I thought I'd reply to it twice. My last 
reply (which I forgot to sign -oops!) was all about spotting a ship. I'll 
cover your other issues here.

>From: Paul Westermeyer <westermeyer@????????.net>
>Reply-To: Spelljammer Setting Discussion <SPELLJAMMER-L@??????.???????.com>
>To: SPELLJAMMER-L@??????.???????.com
>Subject: [SPELLJAMMER] Spelljamming speed, and invisibility
>Date: Sat, 4 Mar 2006 09:42:11 -0500
>
>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.
>
>This weans we should think of SJ speed more like Star Trek's Warpspeed then 
>Star Wars' hyperspace.

I don't think of SJ speed is like Star Trek warpspeed or Star Wars 
hyperspace. The analogy is not really useful because Star Trek uses special 
sensors to track faster than light ships and Star Wars has ships follow 
other ships in a straight line (and hope for the best). Both of those sci-fi 
settings have ships that exceed the speed of light (making normal vision 
impossible).

I don't know if light has a speed in D&D, but if it does spelljammer speed 
is less than the speed of light, so ships would not experience any Einstein 
related light problems. It all comes down to a spot roll (which as I 
agonised over in my last post is not an easy calculation).

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

Fleets that want to co-ordinate movement would probably all start off at the 
same time on the same heading. They would probably all have orders that told 
captains, navigators and helmsmen when to drop out of spelljammer speed. 
Each individual ship would need to maintain a 12,500 yard separation from 
other ships in the fleet (to avoid making each other drop to tactical 
speed).

Tacticians would probably have several formations that they would use 
depending on circumstances. Here are two I can think of:

1) Single file - all ships follow each other in a straight line. Anything 
that causes the lead ship to drop to tactical speed makes the entire 
formation slow down, as they catch up get within 12,500 yards of the ship in 
front.

The advantage of this formation is that random objects that are encountered 
between the start and end points of a voyage will not split up the ships. 
The full fleet will be able to deal with any random encounters and then move 
on.

The disadvantage is that ships that are running away from a fleet using this 
formation, can use it against them. One large object thrown overboard will 
stop every pursuer in one go.

2) Line abreast - All ships fly side by side. In two dimensions (used for 
the hex maps in the SJ boxed set) they would be 12,500 yards apart. (If you 
wanted more accuracy (with three dimensions) they could fly in a three 
dimensional hexagonal array, but that would be much harder to run in game 
terms, so I'd stick with line abreast). As none of the ships are behind each 
other nothing that causes one of them to slow to tactical speed will effect 
any other ship in formation.

The advantage of this type of formation is that all ships can get within 
range of enemy ships as quickly as possible (or space installations) without 
getting in each other's way.

The disadvantage is that any one ship could easily be knocked out of 
formation. With lots of ships in the formation, a ship could accidentally 
get left behind. A single ship left behind would be more vulnerable to 
attack.

My guess is that large fleets of ships would use a combination of formations 
depending on the immediate situation and the proximity of their intended 
target. Single file would probably be used for a lot of the time with fleets 
switching to something like line abreast when preparing a short hop into a 
combat.

Formations that are part way between the two extremes (double file, arrow 
and diamond) would provide some of the benifits of each type.

Double file would halve the risk of something stopping the entire fleet, but 
would still give lookouts a chance to realise half the fleet had stopped.

Arrow would be useful if an attacker turned to the left or right as half the 
ships would be able to chase without getting in each others way.

Diamond formation would be good for an all round attack and defense 
capability. (In some ways it would be similar to roman tortouse formations.)

>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.
>
>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.
>
>Comments?
<snip>
>Paul Westermeyer,  westermeyer@????????.net


If your invisibility spell works anything like the normal one (on a grander 
scale) then don't forget that invisibility does not make light invisible. 
Hostile ships would be able to see a light source on the deck moving at 
spelljammer speed and should be able to make some form of attack in that 
direction. (This should be similar to blindfighting with respect to miss 
chances.) If your crew runs without lights and they do not have low-light 
vision or darkvision then they should recieve penalties on actions that 
involve sight.

The normal invisibility spell ends if a character attacks. A ship is not an 
unattended object. So a ship invisibility spell should end if ships weapons 
are fired at another ship or if the ships mage/cleric uses a damage causing 
spell on another ship. This means that ships that know an invisible ship is 
in the area can take potshots at it, in the knowledge that it will have to 
give its position away to defend itself.

Things droped by an invisible character become visible, so things thrown or 
dropped overboard of a ship should too. I'm not sure if they would become 
visible before or after they leave the air envelope, but I'd guess that they 
become visible as soon as they lose contact with the ship. So I'd probably 
rule that a person that fell overboard would give away the general direction 
of the ship until they were picked up (and vanished again) or got to the end 
of the air envelope and fell into the void. You are very right in working 
out that hostile ships could take advantage of this. If they did fire clouds 
of bright objects or bright powder into the air envelopes of invisible 
ships, I can imagine that the shape of the revealed air envelope would look 
very similar to an american football. Someone should be able to target the 
centre, but would have a chance to miss.

The fact that invisilibity does not cause silence is not a problem in the 
vacuum of wildspace, but it might be in a planetary atmosphere. If you fired 
grape shot at a crew and wounded some they might cry out.

Stepping in a puddle gives away the position of an invisible character, and 
I would say that flying into certain substances would do the same for an 
invisible ship. This is similar to the problem with dust fired at a ship. 
However, in this case it would be natural hazards that would give the ship 
away. A sphere with clouds of dust or ice would cause the ship to be 
temporarily revealed until the dropped out of the air envelope. An invisible 
ship would have to try to avoid things like this if it was being chased.

David Shepheard