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# Vector Rules (was: RE: Newbie Ship Question)

From: Gravity is falling in a good way today <KOCHTE@s...>
Date: Thu, 02 Oct 1997 22:26:43 -0500 (EST)
Subject: Vector Rules (was: RE: Newbie Ship Question)
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Status: RO

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

Mk
........................................................................
..
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"
>>system for FT itself that we posted to this list some time ago (I
think
>>they are still out there on some of the web pages)
>>
>Can you please post this again or refer me to it.
>

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.

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
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
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

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).
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