[GZG] A new vector movement system

I'm trying to design a new set of vector movement rules for Full Thrust that
increase the realism without too much extra hassle. First draft is online at

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eresting. Jovian Chronicals has something similar in their movement system,
which is a cross between cinematic and vector.

It takes only one drink to get me drunk. The trouble is, I can't remember if
it's the thirteenth or the fourteenth.
   George Burns

2008/12/10 Hugh Fisher <laranzu@ozemail.com.au>

> I'm trying to design a new set of vector movement rules
<http://members.ozemail.com.au/~laranzu/fullthrust/newvector.html<http:/
/members.ozemail.com.au/%7Elaranzu/fullthrust/newvector.html>
> >

Thanks, Hugh!

Not being an FB-vector player, and having difficulty getting players
together (my bad, not the game...), it'll take me a bit to get the noggin'
around your ruleset. Give us a few, and then I'd like to see your argument for
your vision over the other in FB 1.

In the FT: Remixed, why did decide to go with the round down, round up MU's
for cinematic course changes? I haven't seen that elsewhere.

The_Beast

Hugh Fisher wrote on 12/10/2008 05:11:51 AM:

> I'm trying to design a new set of vector movement rules

On Wed, Dec 10, 2008 at 4:11 AM, Hugh Fisher <laranzu@ozemail.com.au> wrote:
> I'm trying to design a new set of vector movement rules

I find no real flaws; although, I would be tempted to just use the

From a realism point of view, I'm dubious about the "Retro-thruster"
idea. It seems to be a refinement of the "Thruster Push" mechanic from FT2.5
vector, which I've never liked.

We house-rule "thruster-pushes" out of the existing FT vector system,
and only allow thrusters to pivot the ship. All changes to the overall
trajectory of the ship require the use of the main engines.
This house-rule reflects the fact that extremely large, powerful and
heavy engines would be required to achieve significant accelerations to
spaceships massing hundreds or thousands of tonnes with any reasonably
foreseeable technology. The standard FT vector rules have the ships'
manoeuvring thrusters deliver half the acceleration as the main engines, which
seems improbable.

The proposed rules at least restricts the thruster-push to operating
as "retro-rockets". This is good. However, it still implies a pretty
huge engine in the nose of the ship, capable of delivering half the thrust of
the main engine. A T6 frigate for example would have a T3
retro-engine for example. That sounds as if we should apply the
"blind-sector" rule (assuming we're playing it) to the nose of the
ship as well as the tail.

A second, half-size, retro-engine would be wasted mass for some
ships. A fast courier for example would probably be better off ditching it to
achieve better acceleration from its main engine. IMHO, it's a bit dubious to
just handwave it with no mass allowance
in the design system. By the way, given that the retro-engine thrust
is half main-engine thrust rounded down, how would you handle a T1
battle-station?

In the above remarks, I'm assuming that we're talking about spaceships
propelled by reaction engines. If you have in mind some exotic reactionless
drive (voodoo priests sacrificing chickens in the engine room for example),
all realism bets are off...

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am in general agreement with Robert. Seems to me that it's more parsimonious
to "flip the ship" using thrusters and use the main drive to change the
movement vector. Even naval architects working with naval construction budgets
have to save mass where possible, or else we could just take Doc Smith to the
logical limit and drive our planets around
the galaxy. ;-)
 The shiphandling requirements would be trivial, but would also give officers
something to grade junior officers on beyond spit and polish. Â Best, Ken

> --- On Thu, 12/11/08, Robert N Bryett <rbryett@gmail.com> wrote:

From: Robert N Bryett <rbryett@gmail.com>
Subject: Re: [GZG] A new vector movement system
To: gzg-l@vermouth.csua.berkeley.edu
Date: Thursday, December 11, 2008, 1:25 AM

From a realism point of view, I'm dubious about the
"Retro-thruster"
idea. It seems to be a refinement of the "Thruster Push" mechanic from FT2.5
vector, which I've never liked.

We house-rule "thruster-pushes" out of the existing FT vector system,

and only allow thrusters to pivot the ship. All changes to the overall
trajectory of the ship require the use of the main engines.
This house-rule reflects the fact that extremely large, powerful and
heavy engines would be required to achieve significant accelerations to
spaceships massing hundreds or thousands of tonnes with any reasonably
foreseeable technology. The standard FT vector rules have the ships'
manoeuvring thrusters deliver half the acceleration as the main engines, which
seems improbable.

The proposed rules at least restricts the thruster-push to operating
as "retro-rockets". This is good. However, it still implies a pretty

huge engine in the nose of the ship, capable of delivering half the thrust of
the main engine. A T6 frigate for example would have a T3
retro-engine for example. That sounds as if we should apply the
"blind-sector" rule (assuming we're playing it) to the nose of
the ship as well as the tail.

A second, half-size, retro-engine would be wasted mass for some
ships. A fast courier for example would probably be better off ditching it to
achieve better acceleration from its main engine. IMHO, it's a bit dubious to
just handwave it with no mass allowance
in the design system. By the way, given that the retro-engine thrust
is half main-engine thrust rounded down, how would you handle a T1
battle-station?

In the above remarks, I'm assuming that we're talking about spaceships
propelled by reaction engines. If you have in mind some exotic reactionless
drive (voodoo priests sacrificing chickens in the engine room for example),
all realism bets are off...

Best regards, Robert Bryett

> On 10/12/2008, at 22:11 , Hugh Fisher wrote:

> I'm trying to design a new set of vector movement rules for Full

> On Thu, Dec 11, 2008 at 7:28 AM, Ken Hall <khall39@yahoo.com> wrote:

Retro-thrusters that would work with some tweaking:

Main thrust is produced by reaction drives with a balanced ring of thrusters
with some freedom of movement, at the extreme rear of the vessel. One of the
mobility restrictions is the nozzles can be pointed no further than 120
degrees from dead astern, to prevent thrust efflux from impinging on the hull.
The angular limit was a compromise between safety, providing the maximum
feasible
retro-thrust, and ship handling characteristics.  A long, spindly ship
could rotate the nozzles even further, but would be hard to pivot and harder
to protect against incoming weapons fire. Even at the small forward angle of
30 degrees ahead of the beam, the main engines, running at full, would be able
to apply a reverse thrust that is 50% ( cosine 60 degrees) of the forward
thrust. Other purposes of the thruster mobility are rebalancing the thrust
ring following damage,

As I said in an earlier posting, your engineering imagination and PSB mileage
may vary, and be just as legitimate as mine. However for *me*:

Pivoting engines are a possibility, but bear in mind that we're probably
talking about some kind of atomic rocket here, so we'd be swinging around some
kind of nuclear reactor, plus whatever support equipment (superconducting
magnets, cooling systems etc.) is required to control the exhaust. It's not
just the hull you'd have to worry about either. Any external structure like
heat radiators would be vulnerable too.

Thrust reversers, or ducts to direct the thrust of a central engine,
imply the ability to "bend" enormously hot, high-velocity streams of
plasma or other exhaust. Thrust-reversers would need the power
partially to *reverse* the impulse of an interplanetary warship's freaking
*main engine*!

I'm not saying these things are PSB-impossible, but the machinery
would *not* be made of chocolate or massless fairy-dust. There would
be serious trade-offs in mass and complexity to achieve the retro-
thrust.

On Thu, Dec 11, 2008 at 7:30 PM, Robert N Bryett <rbryett@gmail.com> wrote:

> Pivoting engines are a possibility, but bear in mind that we're

Did someone say Atomic Rocket? This is a good moment to plug Winchell Chung's
site:

http://www.projectrho.com/rocket/index.html

Which is a fantastic resource for these kinds of questions. Note that since
we're using PSB "grav" drives, redirecting the thrust could be easy or hard
depending on the brand of PSB(tm) you use.

On Thu, Dec 11, 2008 at 5:30 PM, Robert N Bryett <rbryett@gmail.com> wrote:
> As I said in an earlier posting, your engineering imagination and PSB

I apologize for implying that my technobabble was good. My intent was to
lament that technobabble comes easily to me, by the paragraph, or

Ack! No need to apologise, and perhaps *I* should apologise instead for being
preemptively defensive. My "your PSB is as legitimate as mine" remark was just
trying to avoid giving the impression that I wanted to denigrate anyone else's
imagination or PSB, before explaining my personal take on things.

Best regards, Robert Bryett

> On 13/12/2008, at 04:47 , Richard Bell wrote:

Oh yes indeed. Mr.Chung's site is pretty much essential reading for
the mundane-SF enthusiast. His section on reactionless drives is a
good summary of the violence "grav" propulsion does to conservation of
momentum and relativity;)

Best regards, Robert Bryett

> On 12/12/2008, at 23:31 , Robert Mayberry wrote:

> Did someone say Atomic Rocket? This is a good moment to plug Winchell

On Fri, Dec 12, 2008 at 4:17 PM, Robert N Bryett <rbryett@gmail.com> wrote:
> Oh yes indeed. Mr. Chung's site is pretty much essential reading for

Read it too much, though, and you start to wonder why the hell we get
into _any_ kinds of "realism" discussions on this list.

For instance, folks will wax knowingly on the proper TO&E for a squad based on
a plasma gun as the support weapon. Yet, a quick peak at this site shows that
plasma guns are no more feasible than steam guns...

> Robert Bryett wrote:

A good point, and one made by other people as well. I'm going to drop the
thrusters from the next version.

> The proposed rules at least restricts the thruster-push to operating

A lot of ships, both in GZG and elsewhere, have two engines on either side of
the hull. So I was thinking one fusion class powerplant and fuel supply, very
large
(and weapon-obscuring) thrusters out the back, smaller
ones to the front.

> A second, half-size, retro-engine would be wasted mass for some

They can't. Anything thrust-1 is assumed to be either
civilian or incredibly clumsy (eg Death Star), so can only use the main drive
for any significant move.

Thanks for responding.

cheers,

> Robert Bryett wrote:

Yeah, thrust *reversers* seem a bit unlikely for any kind of reaction drive.

What do you think of gimbals and/or some magnetic fields
to bend the exhaust through a narrower range of angles up to 30 degree? That
would get rid of the requirement to be aligned exactly with the direction of
thrust. A good thing in game terms, being less fiddly, and to me a useful
thing if I really were designing a spaceship.

cheers,

> Robert Mayberry wrote:

A fantastic resource indeed... as long as you can shake off the "Oh gawd
everything I thought I knew or imagined about spaceships is totally wrong"
feeling afterwards :-)

cheers,

Magnetic fields will work to bend a plasma, just fine. The electrons all go
the other way, but they carry little of the momentum. Similar, less forceful,
devices are already in use in labs throughout the world, as magnetic
deflection of charged particles is at the heart of a mass spectrometer. The
numbers are probably daunting for multiple
g's of thrust, but any first-year student of engineering or physics
should be capable of grinding out a first order solution. The fiddly
refinement is needed to account for the effects of the plasma stream
having a non-zero thickness and producing its own magnetic field.  The
mountings of the magnets will be the structural elements that transfer the
thrust to the ship, so they will be quite heavy. The only restriction on the
propellant is that it be isotopically pure, as each nuclear mass will bend at
a different radius.

Designing pivots for the atomic rocket engine as a unit, while thrusting, is
comparable to the problem of designing bearings for
heavy cranes-- they both have heavy loads that can change their thrust
line. Also, as some problems get solved, the rockets themselves shrink. The
ultimate is when we can simultaneously inject plutonium and hydrogen into the
reaction chamber and run the reactor at prompt criticality (an ongoing nuclear
explosion that limited by the available fissile nuclei).

On Sat, Dec 13, 2008 at 2:50 AM, Hugh Fisher <laranzu@ozemail.com.au> wrote:
> Robert Bryett wrote: