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Month Index: January, 1996

From:     lewis pulsipher <lewis_pulsipher@?????.????????.?????.????.mil>
Date:     Wed, 17 Jan 96 12:40:43 EST
Subject:  Re: [none]
I'm going to post several large items in the next week or so and I thought I'd
explain where I'm coming from, in order to save some comments.

1.  I greatly appreciate all the work that Richard Pugh, Ville Lavonius, and
others have contributed to the Spelljammer net books.

2.  In a "previous life" I had several of my boardgame designs published (only
Brittania is still in print), and I was contributing editor to Dragon, White
Dwarf, and Space Gamer. Since TSR has abandoned Spelljammer, I really don't care
what the rules say, I just want a game that works well.  When I can work within
the rules, OK.

3.  Not surprisingly, I still play first edition AD&D, but I adopt what I like,
such as Spelljammer, from the second edition.  I make up my own world rather
than use TSR's campaign settings.  Spelljammer is an adjunct to the main
campaign, not a substitute for it.

4.  In another of my early lives I earned a Ph.D. in military and diplomatic
history, and not surprisingly I like some internal consistency in my fantasy
games, something that will allow the "willing suspension of disbelief".  The
notion of conquering an entire *civilized* world with the crews of a few dozen
(or hundred) tiny ships is ridiculous, for example.  And I've yet to see the
phlogiston simply because an entire sphere, and all its worlds, provides more
than enough variety.

5.  Because (as we've seen in the few months I've been here) a back-and-forth
discussion about rules or styles of play can descend into acrimony, I don't
engage in discussions.  Any comments you offer will be taken into account in
further drafts, but please don't expect a direct reply.  Thanks.

6.  Please don't post any draft from here anywhere else until I've finished the
item to my satisfaction.

Lew Pulsipher

       Spell-jamming Limitations Near Large Heavenly Bodies
                         Lewis Pulsipher

Years ago, before Spelljammer, when several heroes attacked the tower of the
Anarch north of Seaward, we captured a flying galley.  You can imagine the
characters' (and players') lust for such a priceless artifact.  (The other guy
got it and gave it to the Temple of Oghma to pay past debts!)

The question I have always wondered about is, when a character gets a
spelljamming ship today, why doesn't he use it to become a really big wheel on
"Earth", rather than wander out into Wildspace?  Wildspace is both unknown and
very dangerous--beholders and illithids!--as well as being very far from home.
A character could have any of dozens of motivations that would cause him to
prefer to stay at home--big fish in a small pond, loyalty to country, loyalty to
local religion, etc.  But even someone who grows up in Wildspace might think
about using his marvelous flying fortress to carve out a barony or become a
famous adventurer on a "groundling" world.  The Spelljammer rules ignore this
problem.  They assume that anyone with a spelljammer will go (or stay) "out
there" and jam.  That doesn't make sense to me, especially remembering my lust
for that flying galley.

It's easy to see that water navies, and in fact any terrestrial force without a
lot of flying capability, is helpless against spelljammers.  Imagine a jammer
dropping "bombs" (or just rocks) without fear of significant retaliation.
Imagine a Neogi Deathspider raiding groundling towns for slaves--they could
extort tribute just by the threat of bombing.   Even if the defenders have a
dozen fireballers, if they can't get close to the `jammer, they can't do a
thing. Choice of height ("the high ground") combined with great speed AND
carrying capacity is nearly unbeatable.  (Yes, there are problems--a great many
"gunslinger" adventurers will try to steal/take any spelljamming ship based on a
groundling world; but all things considered, I'd rather be the guy with the big

I've devised a rule addition that severely limits the maneuverability of
spaceships near large bodies, which goes a long way to removing the
capability/incentive to use a `jammer near a planet.  If the `jammer is
virtually unmaneuverable below a given height, and that height is too high for
effective attacks, then many `jammer-owners will indeed prefer to go "out
there", and the rest will have a much less effective weapon against groundlings.

                           The Barrier

When a jammer approaches too close to a heavenly body, it loses all
maneuverability except to go straight up or down (in relation to that body) and
change facing.  This distance varies with the tonnage of the ship, its ship's
rating, and the size of the body.

Jammers that can land in water and sail, can move in water like any
water-vessel--but sailing, not jamming.  Practically speaking, this is limited
to "groundling" vessels.

Movement upward and downward below The Barrier is fairly slow.  Maximum speed of
descent is 1,000 feet per ship's rating point.  (This translates to about 12
miles an hour.)  Climbing rate is 250 feet per ship's rating point.

This gives a spelljammer great mobility on a planet as a whole--remember that
speed above The Barrier is still 17 mph per ship's rating point--but little
ability to conduct raids or affect battles.

The helmsman can feel the approach of the Barrier.  To him, it feels like a
giant hand is closing in on the ship (hope the helmsman isn't claustrophobic!),
and when the barrier is reached, the hand will only let the ship move up or

                     Calculating the Barrier

To calculate The Barrier, take the lower value of one percent of the diameter of
the body in feet or 5,000.  (For simplicity, round miles to 5,000 feet each.)
This means that 5,000 will be used for any body with a diameter of more than 100

Multiply this number by the tonnage of the ship, divide by the ship's rating,
and multiply by a number derived from the ship's maneuverability rating, as

     A- .2
     B- .4
     C- .6
     D- .8
     E- 1
     F- 1.2
     G- 1.4

The result, in feet, is where The Barrier exists for that ship.  Below that
height, the ship can only move up or down and change facing.  Above that height
it can maneuver normally.  A jammer CAN be pulled around by grounded ropes, like
a blimp with a great deal of inertia, and it can be towed by something large
enough to pull it around--see below.  But it can't move sideways on its own,
when at or below The Barrier.  No crew is required below The Barrier, unless the
ship is turned (changed in facing).  Turning requires full crew, and turning
speed is one hexside per round, regardless of ship's rating or maneuverability
rating. [To make this even tougher on the `jammer, allow no turning at all.]


For example, on a normal planet, a galleon (40 tons) at SR2 and maneuverability
E hits the barrier at 5,000 times 40 divided by 2 times 1 or 100,000 feet.  A
dragonfly (10 tons) with SR 4 and maneuverability of C, let's say, is 5,000
times 10 divided by 4 times .6 or 7,500 feet.  (Note that's 2,500 yards, or five
hexes in space-combat terms--a long way, especially considering that gravity and
air interfere with weapons ballistics.)  If the object in question is an
asteroid 5 miles in diameter, one percent is 250 feet.  So the galleon hits The
Barrier at 250 x 40 / 2 x 1 or 5,000 feet.  And better vessels can get much

A Neogi Deathspider (100) with SR 3 and maneuverability of E going to a planet
would be 5,000 times 100 divided by 3 times 1 or about 133,000 feet.  So if a
Neogi is going to raid, it has to come down near a place, then send out raiders,
rather than float over the place, unless it gets lucky.

                     Inaccuracy of "Landfall"

Why lucky?  There's no foregone conclusion that you can drop down accurately on
a place.  In fact, there's every likelihood that you'll miss, if you're very
high.  To calculate how far off from your landing target you'll be, roll
percentage dice.  Add the "add-on" value in the following table (you may have a
negative percentage, which amounts to zero).  Divide by the "divisor" in the
following table, then multiply by the height in feet.  This is the number of
feet of the miss, roll D12 for direction.

Example: it's a clear day, middle of the day.  Divisor is 5, addon is -10.
Height is 5,000.  The d100 roll is 43.  With addon that's 33, converted to .33,
times 5,000 is just over 1,600 feet of miss.


A spelljammer affected by The Barrier can be moved by non-jamming forces.  The
wind can move the vessel, or creatures on land can tow it, or a sailing ship can
tow it.  (Flying creatures cannot two a `jammer, except when you have a very
large flyer and a very small `jammer.)

A steady wind can slowly move a `jammer (drift, really), if the helmsman allows
it.  Speed of movement is one foot per minute per mile-per-hour of steady wind
speed.  If the vessel is a groundling ship with lots of sail area, such as a
galleon, then the speed is five feet per rather than one.

For example, if the wind is 10 mph, the jammer can drift 10 feet per minute (600
per hour), but a galleon could drift 50 feet per minute.

"Sailing" in any direction except directly away from the wind is impossible.
(You can sail across wind in water-sailing because the water provides heavy
resistance to sideways movement; air does not.)

A jammer can be pulled by ropes or chains attached to organized creatures on the
ground.  A minimum of 10 men (or equivalent) per ton of vessel is needed to move
the jammer at all.  (This number enables the tow-ers to overcome the inertia of
the ship.)  Speed is number of men times five, divided by 10 times tonnage, feet
per minute.

So an 18 ton ship requires 180 men or equivalent to move at all.  And that
number could move the ship five feet per minute.

A horse or oxen is equivalent to 10 men.  As a rough approximation, for bipedal
monsters such as giants and ogres, square the height (in feet) of the monster
and compare with a value of 35 for a man.  For example, a 20 foot monster =400,
the equivalent of nearly 13 men.

A sailing ship can tow a jammer at one tenth its normal sailing speed, and only
directly away from (with) the wind.  (The ship cannot sail across wind because
it moves so slowly that water resistance isn't sufficient.)  The sailing ship or
combination of ships must be at least as large as the `jammer.


Recognize that hitting something with a dropped object is very difficult, not
easy.  (Read your WWI and WWII air histories.)  The same must be said for firing
a ballista or catapult from a spelljammer at targets on the ground far away.
The `jammer provides a good firing platform, but on the other hand, air
resistance interferes with the weapon's range as compared with Wildspace.

Translate 1 Spelljammer hex range of a weapon to 100 yards.  Double the maximum
range for firing downwards (but add no more than half the actual height of the
`jammer).   For example, a medium catapult with range 3 in space can fire 300
yards, plus half the height of the `jammer up to an additional 300 yards.
(This is measured from the ground-zero point of the `jammer, so that no figuring
of hypotenuses and such is necessary.)

Accuracy is reduced immensely (because of air)--subtract 10 from the die roll
(or add 10 to the THACO) to start with.  If the target is in the "extra" range
beyond the 100 yards/hex range, subtract 5 more.  And if the height of the
`jammer is greater than the 100 yards/hex in-atmosphere range of the weapon,
subtract another 1 per 500 feet above that height.

For example, a light ballista has a 500 yard range (not counting addition for
height).  If the `jammer is 5,000 feet high, which is 3,500 feet higher than
that range, subtract seven from the attack die roll.

If you think the purpose is to make it very difficult to hit anything from a
height--yes!  That's not only "realistic" ("to hit" chances are ridiculously
high in Spelljammer), it fills the purpose of reducing the value of `jammers in

  Accuracy modifier table.   Divisor is listed above subtractor.

Weather:,               Clear,          Hazy,           Cloudy/Fog
Full daylight,          5               4               2
                        -10             -5              +5

Weak light,             4               3               2
                        -5              0               +10

Moonlight/Target well lit,3             2               1
                        +10             +20             +20

Dark,                   2               1               1
                        +20             +30             +40

(Fingers crossed that this table comes out properly...)

d100% minus subtractor / divisor times height = miss distance.  D12 for

Defect of this system: I'd prefer a system that didn't require any tables: it's
always best to have rules that are easy to remember.


Previous Message: Re: Chtorran sphere - Ouch!!
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Month Index: January, 1996

SubjectFromDate (UTC)
[none]    WH GREENSLADE    09 Dec 1994 16:45:43
[none]    zz David Reilly    05 Jun 1995 00:43:12
Re: [none]    Gary Dickey    06 Jun 1995 06:17:08
Re: [none]    Thomas O. Magann Jr.    29 Aug 1995 18:14:18
[none]    lewis pulsipher    17 Jan 1996 17:40:43
Re: [none]    Ken Lipka    18 Jan 1996 12:59:25
[none]    THANOZ@???.com    22 Feb 1996 00:35:01
Re: [none]    Thomas O. Magann Jr.    22 Feb 1996 01:58:46
[none]    Jamie McGarty    31 May 1996 20:40:39
Re: [none]    Thomas O. Magann Jr.    31 May 1996 21:05:55
[none]    Deviant    11 Jun 1996 06:32:17
Re: [none]    John Fincke    01 Jul 1996 18:17:41
[none]    KENT@?????.???????.???.edu    07 Aug 1996 19:10:52
[none]    KENT@?????.???????.???.edu    07 Aug 1996 19:11:30
[none]    KENT@?????.???????.???.edu    07 Aug 1996 19:12:09
[none]    George Hernandez    16 Aug 1996 15:22:02
Re: [none]    Timothy S. Hill    16 Aug 1996 22:31:48
[none]    James West    22 Aug 1996 04:41:55
[none]    GOMEZ SOLARES VICTORMANUEL    13 Sep 1996 01:45:11
Re: [none]    Hatcher    16 Sep 1996 18:07:22
[none]    Beckman, Jim    05 Oct 1996 12:01:28
Re: [none]    Alberto Zanini    06 Oct 1996 11:26:39

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