Vector Rules (was: RE: Newbie Ship Question)

Status: RO

These are straight from Jon T which he posted to the list earlier this year.
Enjoy!

Mk
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From:   IN%"FTGZG-L@bolton.ac.uk" 18-MAR-1997 15:21:19.76
Subj: [OFFICIAL] Vector rules

> First off, we've done several sessions of testing on the "true vector"

OK, here it is for the people who missed it last time; to those of you who've
already seen it, apologies for using up the bandwidth! BTW, this is somewhat
rewritten from the last version, in an attempt to
make it clearer to understand - it REALLY is very easy once you've
grasped it, but without the aid of diagrams it is a bit long winded to explain
in words alone. The best way is to plot out an example, and it'll all slot
into place.

TRUE VECTOR MOVEMENT system for FULL THRUST; playtest notes only. Jon Tuffley,
March 1997.

BASIC PRINCIPLE: If a ship is travelling in one direction, and you "push" it
in another direction by using its drives, its resultant path is a new vector
given by adding the new push to its original movement. The faster a ship is
moving, the less it is able to change course with a given amount of thrust.

DRIVE UNITS: The main drives are only able to apply thrust along the axis of
the ship, so can only accelerate it in the direction the ship is currently
facing. To rotate the ship, or to apply a thrust "push" either to the side or
in reverse, small groups of "manoeuvre thrusters" are placed around the ship;
these are NOT represented by icons on the ship diagram, as they are assumed to
be powered from the main drive units. A ship's thrusters have HALF the
thrust output of the ship's main drives - so a ship with main drive
output 6, the thruster power would be 3. Loss of the main drives also reduces
the
capabilities of the thrusters, in proportion - so a ship with damaged
drives will have its thruster power halved also (round up fractions). A "burn"
with the main drives should be written in the movement orders as
MD (Main Drive), plus the amount of thrust to be used - thus MD4 would
be a burn of thrust 4 with the Main Drives, moving the ship 4" in whatever
direction it is currently facing.

NOTE: the thrust available from the Main Drives is separate from that
provided by the Thrusters - a ship may use all its Main Drive power for
an acceleration burn and still use its available thruster power for rotation
or pushes.

FACING (HEADING): A ship does NOT have to be moving in the direction the model
or ship
counter is facing, and indeed most of the time it will not be - it will
usually need to have its main drives (at the stern) facing in a different
direction in order to apply thrust to manoeuvre. Ships are therefore always
marked with a small "direction arrow" counter placed by the ship counter or
model; this marker always points along the actual COURSE - the direction
that the ship is moving -  irrespective of the orientation of the model
or ship counter. The actual facing of the ship model or counter at any given
time is called its HEADING - thus a ship that is currently facing
"backwards" (using its main drives to reduce its velocity) would have a COURSE
of 12, but a HEADING of 6.

REACTION DRIVE MOVEMENT: Movement under Reaction Drives is performed in two
steps: firstly, the ship is moved along the course it was on at the end of its
previous turn (ie: the direction indicated by the arrow on its course marker),
a distance equal to its velocity as noted at the end of the previous turn. THE
SHIP'S COURSE MARKER IS LEFT IN ITS STARTING POSITION at this stage, and is
NOT moved with the ship. This movement is always made exactly as per the end
of the last turn, regardless of whatever movement orders have been written for
the ship for this turn. Now, for the second stage of the movement, the ship
applies any facing changes and/or any thrust written in its orders for
this turn, and is moved a distance equal to any thrust applied. Now, lay a
ruler or tape measure between the ship's new position and its starting
position (as indicated by the course marker that was left at the starting
point),
and measure the distance - round this to the nearest full inch, and
record this as the new VELOCITY for the turn end. Finally, with the ruler or
tape still in position, move the course marker up to the ship again, this time
pointing exactly parallel to the ruler line - this now indicates the
ship's new course at the end of the turn.

SUMMARY OF REACTION DRIVE MOVEMENT: 1) Move ship according to final vector
from previous turn (direction as indicated by course marker, distance as
recorded velocity).
2) Apply facing changes and/or thrust for this turn - move ship
accordingly. 3) Measure distance from course marker to new ship position, note
this as new velocity. Move course marker up to ship to show new heading.

THRUSTER ROTATION: In order to use its main drives to change course, a ship
under Reaction Drive must be ROTATED so that its drives point in the direction
that the thrust is to be applied. Rotation can also be used when no thrust is
required, to change the heading of the ship in order to bring weapons to
bear. Rotation is accomplished by the ship's THRUSTERS - each point of
thruster power used for rotation will turn the ship through 30 degrees (one
heading point) - so a ship on heading 12 that applies three points of
thruster power to starboard rotation will turn through 90 degrees to face
heading 3. Thruster rotation orders should be noted as RP (for Rotate Port) or
RS
(Rotate Starboard), plus the amount of thrust applied - so RS3 would be
a starboard rotation of 3 points as in the example above.

THRUSTER PUSHES: A thruster "push" is firing a combination of manoeuvre
thrusters to alter
the course and/or velocity of the ship, WITHOUT affecting its actual
heading (ie: the ship ends the turn with its model pointing the same way it
started, although its course may have changed). Pushes may be made to PORT,
STARBOARD or REVERSE (using the forward "retro" thrusters to slow the ship
down without having to spin it round and use the main drive). As with
rotation, the number of manoeuvre points that can be applied in one turn is
equal to the thruster power of the ship. PUSH orders should be written as PP
(Push to Port), PS (Push to Starboard) or PR (Push in Reverse), again
followed by the number of thrust points applied - so PR3 would be using
3 thruster points from the retros to push the ship 3" "backwards" relative to
its current heading. Pushes may only be applied directly to port, starboard or
rearward relative to the ship's heading at that moment. No push movement can
change the HEADING of a ship.

COMBINING MANOEUVRES: If desired, a ship may combine several different uses of
its manoeuvring thrusters in a single game turn, provided the TOTAL of
thruster points expended does not exceed the total available. It is quite
acceptable for a
ship with (say) 3 thruster points available to make a 2-point rotation
before applying a main drive burn, then a further 1-point rotation
afterwards (probably to bring weaponry to bear on its desired target);
alternatively it could, for example, make the 2-point rotation and then
use the remaining 1 thruster point for a 1" thruster push to port, starboard
or aft as desired.

ORDER SEQUENCE: The actual sequence in which thruster and main drive burns are
applied in a single turn will make a difference to the final course and
velocity of the ship, so it is necessary to rule on what order things are done
in. Each effect is applied to the ship strictly IN THE ORDER THEY ARE WRITTEN
DOWN BY THE PLAYER. If the player writes RP2, MD6 then the ship will first be
moved according to its starting vector (as always), then rotated 2 points to
port (RP2) and moved 6" along its new heading (MD6). If, on the other hand,
the order is written MD6, RP2 (thus applying the main drive burn BEFORE
rotating the ship to its new heading) then the result will be VERY
different in terms of the ship's final vector and position - plot each
one out and you'll see what we mean!

MOVEMENT EXAMPLE: A ship has a Main Drive thrust of 6 and a Thruster rating
(for manoeuvring) of 3. It is currently moving in the same direction that it
is facing, so its course and heading are the same (12). Its current velocity
(as at the end of the previous turn) is 10". The ship's movement orders for
this turn are RS3, MD6; it is to rotate 3 points to starboard (using all the
available power from its thrusters) and then perform a maximum-power
main drive burn of 6.
The first step is to move the ship on its existing course and velocity -
so it is moved straight forward (course 12) by 10"; Now the ship is rotated
three points (90 degrees) to starboard, and the main drive thrust is
applied - the ship turns to heading 3 and is moved 6". Finally, the
distance between starting and final positions is measured - it will be
11.6", which we will round up to 12", which is recorded as the new velocity;
the course marker is moved up to the new position of the ship, parallel to the
line between starting and final positions, indicating the ship's new course.
The ship ends the turn on heading 3, but moving on the new course indicated by
its marker at a new velocity of 12" per turn.

NOTE that this system will mean that ships may be moving on COURSES that are
not exactly one of the twelve FT course directions, though for simplicity we
say that the ship's HEADING (its facing) must always be one of the 12 standard
points.

ROTATION OF STATIONARY SHIPS: Any ship that does not move at all in a turn
(ie: its velocity is zero at both start and end of turn) may be rotated on its
axis to point in ANY desired direction, provided orders have been written to
this effect. This rotation may exceed the normal course change limitations,
and on the NEXT turn the ship may begin to accelerate in its new direction if
desired. Example: a ship with a velocity of 0 at the start of the turn could
have its orders written as S6 (or P6, which has exactly the same result in
this
case) - it will spin through 180 degrees, but remain at velocity 0.

[Special note: we are currently undecided as to whether to restrict ship
rotation (while moving) to the thruster power as above, or whether to allow
even a moving ship to freely rotate to any course as described for stationary
ships; the latter is probably more realistic, but does it give the player too
much freedom? Responses eagerly awaited when you've tested it both ways!]

Jon (GZG).