Ship Design Philosophy

Discuss the Traveller RPG and its many settings
phavoc
Cosmic Mongoose
Posts: 4255
Joined: Tue Nov 04, 2008 6:13 pm

Re: Ship Design Philosophy

Postby phavoc » Mon Jan 01, 2018 10:37 pm

AnotherDilbert wrote:
Mon Jan 01, 2018 2:47 pm
I can't see that MgT discuss this at all, but in earlier editions "inertial compensators" are a separate artificial gravity system (that has nothing to with inertia).
Tech level requirements for maneuver drives are imposed to cover the grav-plates integral to most ship decks which allow high-G maneuvers while the interior G-fields remain normal.
Artificial gravity G compensators create an artificial gravity field in direct opposition to the axis of acceleration, thus negating the acceleration
Agreed. Under MGT Trav (either version) the concepts of grav plates and intertial compensators are tied together. Evidently there is no upper limit and no risk. Crap just works, and works well.
Condottiere
Chief Mongoose
Posts: 6232
Joined: Mon Sep 23, 2013 8:23 pm

Re: Ship Design Philosophy

Postby Condottiere » Tue Jan 02, 2018 4:27 am

And here I thought that tumbling down the rabbit hole was magic.

Guess we're back to thousands of tiny tractor beams stabilizing anything not nailed down.
Sigtrygg
Greater Spotted Mongoose
Posts: 957
Joined: Sat Aug 12, 2006 9:23 am

Re: Ship Design Philosophy

Postby Sigtrygg » Tue Jan 02, 2018 11:10 am

Magic technologies in need of handwavium in the OTU:
gravitics - may be used to explain away the maneuver drive, null grav modules, grav plates, acceleration compensation, repulsors and tractors, possibly heat sinks and a basis for jump drive discovery.
I have yet to see an explanation of how gravitics in the OTU is meant to work other than it is way beyond out understanding of physics.

The jump drive itself - and the higher TL versions such as the heironymus unit, the hop, skip and leap drives etc.
At least the idea of other dimensions is scientifically plausible.

Strong and Weak force manipulation - used to make nuclear dampers, meson guns and screens, disintegrators.

This is again plausible we just have no idea how to do it.
Condottiere
Chief Mongoose
Posts: 6232
Joined: Mon Sep 23, 2013 8:23 pm

Re: Ship Design Philosophy

Postby Condottiere » Sat Jan 06, 2018 10:05 am

Lifters could be just infinitely falling into or rejecting gravity; or exasperatingly accepting it on an infinite slide.

Artificial gravity could be inducing that fall.

Inertial compensation does not seem explainable.
AnotherDilbert
Cosmic Mongoose
Posts: 2824
Joined: Wed Dec 23, 2015 2:49 pm
Location: Sweden

Re: Ship Design Philosophy

Postby AnotherDilbert » Sat Jan 06, 2018 10:18 am

Condottiere wrote: Inertial compensation does not seem explainable.
I do not see the problem.

If we can generate a gravity field that pulls everything towards the deck at 1 G, then we can generate a gravity field forward at 1 G negating the perception of a 1 G acceleration of the ship (cf Einstein's Monkey).

Inertia is not removed.
Condottiere
Chief Mongoose
Posts: 6232
Joined: Mon Sep 23, 2013 8:23 pm

Re: Ship Design Philosophy

Postby Condottiere » Sat Jan 06, 2018 7:11 pm

It's implied that inertia is compensated for by being removed or neutralized.

If the manoeuvre drive creates a field that neutralizes inertia, whether totally or partially, this won't likely work:

Image
AnotherDilbert
Cosmic Mongoose
Posts: 2824
Joined: Wed Dec 23, 2015 2:49 pm
Location: Sweden

Re: Ship Design Philosophy

Postby AnotherDilbert » Sat Jan 06, 2018 7:37 pm

Condottiere wrote: It's implied that inertia is compensated for by being removed or neutralized.
Where?

CT to TNE explicitly says otherwise.
CT wrote:Tech level requirements for maneuver drives are imposed to cover the grav-plates integral to most ship decks which allow high-G maneuvers while the interior G-fields remain normal.
TNE wrote:Artificial gravity G compensators create an artificial gravity field in direct opposition to the axis of acceleration, thus negating the acceleration
Sigtrygg
Greater Spotted Mongoose
Posts: 957
Joined: Sat Aug 12, 2006 9:23 am

Re: Ship Design Philosophy

Postby Sigtrygg » Sat Jan 06, 2018 10:42 pm

Just about every CT supplement and adventure that details ships has some version of this:
Acceleration compensators are also installed to negate the effects of high acceleration and lateral G forces while
maneuvering
.
So the acceleration compensators don't just compensate for the maneuver drive thrust, but also the g-forces inherent in turning.
Condottiere
Chief Mongoose
Posts: 6232
Joined: Mon Sep 23, 2013 8:23 pm

Re: Ship Design Philosophy

Postby Condottiere » Tue Jan 09, 2018 6:40 pm

Understanding how inertial compensation works, gives a direction as to how to design spaceships in Traveller.

If we know that the jump drives don't require an exterior vent, nor aligned in the direction of the jump, we can basically stick them anywhere.
Condottiere
Chief Mongoose
Posts: 6232
Joined: Mon Sep 23, 2013 8:23 pm

Re: Ship Design Philosophy

Postby Condottiere » Wed Jan 10, 2018 12:44 am

Spaceships: Weapon Systems, Incoming Ordnance and Dogfighting Range

If you ascribe missiles and torpedoes as spacecraft, once they enter dogfighting range, anti missile (and torpedo) weapon systems should then be able to ramp up to six second rates of fire.

Missiles and torpedoes aren't really potentially faster than warships.
baithammer
Lesser Spotted Mongoose
Posts: 623
Joined: Wed May 31, 2017 2:21 am

Re: Ship Design Philosophy

Postby baithammer » Wed Jan 10, 2018 1:05 am

Depends on how complicated you want to make the math.
Ishmael
Lesser Spotted Mongoose
Posts: 458
Joined: Fri Feb 08, 2008 3:27 am

Re: Ship Design Philosophy

Postby Ishmael » Wed Jan 10, 2018 2:23 am

Condottiere wrote:
Wed Jan 10, 2018 12:44 am
Spaceships: Weapon Systems, Incoming Ordnance and Dogfighting Range
Missiles and torpedoes aren't really potentially faster than warships.
Only because Traveller has always ignored the square-cube law. Its the reason a Boeing 747 can't manoeuvre like a Zlin Acrobat.
( I really mean 'accelerate' as fast... not top speed )
AnotherDilbert
Cosmic Mongoose
Posts: 2824
Joined: Wed Dec 23, 2015 2:49 pm
Location: Sweden

Re: Ship Design Philosophy

Postby AnotherDilbert » Wed Jan 10, 2018 2:06 pm

Ishmael wrote: Only because Traveller has always ignored the square-cube law. Its the reason a Boeing 747 can't manoeuvre like a Zlin Acrobat.
( I really mean 'accelerate' as fast... not top speed )
There is no reason for a small craft to have higher acceleration than a large craft.
There is reason to believe that a small craft might rotate quicker (smaller dimensions, so lower moment of inertia for the same mass), hence change direction of acceleration.
baithammer
Lesser Spotted Mongoose
Posts: 623
Joined: Wed May 31, 2017 2:21 am

Re: Ship Design Philosophy

Postby baithammer » Wed Jan 10, 2018 7:21 pm

It is mainly the fall off of thrust performance at higher mass and distance required to cover equivalent rotation.
Condottiere
Chief Mongoose
Posts: 6232
Joined: Mon Sep 23, 2013 8:23 pm

Re: Ship Design Philosophy

Postby Condottiere » Wed Jan 10, 2018 10:56 pm

You can always turn tail and accelerate in the other direction.
Ishmael
Lesser Spotted Mongoose
Posts: 458
Joined: Fri Feb 08, 2008 3:27 am

Re: Ship Design Philosophy

Postby Ishmael » Thu Jan 11, 2018 11:57 am

AnotherDilbert wrote:
Wed Jan 10, 2018 2:06 pm
Ishmael wrote: Only because Traveller has always ignored the square-cube law. Its the reason a Boeing 747 can't manoeuvre like a Zlin Acrobat.
( I really mean 'accelerate' as fast... not top speed )
There is no reason for a small craft to have higher acceleration than a large craft.
There is reason to believe that a small craft might rotate quicker (smaller dimensions, so lower moment of inertia for the same mass), hence change direction of acceleration.
Structural considerations, actually.
Consider doubling the size of a ship in each dimension... twice as long, tall, and thick,
mass increases eight-fold ( assuming ship density remains constant )
load bearing area of the structure increases only four-fold. The larger ship can only handle half the force, half the acceleration, of the smaller ship unless the larger ship increases the volume of its load bearing structure by nearly 3 times ( * 2.828 ) to make up the difference.
You'd also be providing 8 times the thrust through 4 times the area ( you'd have to increase the man. drive by nearly 3 times to keep the same level of thrust per unit area )

The square-cube law should also determine the number of hardpoints available to a ship as ship volume increases (assuming hardpoints scale with surface area).

https://en.wikipedia.org/wiki/Square%E2%80%93cube_law

Naturally, larger ships will have greater moments of inertia and thus should have lower agility. There will also be less force available to change heading due to structural issues noted above.
AnotherDilbert
Cosmic Mongoose
Posts: 2824
Joined: Wed Dec 23, 2015 2:49 pm
Location: Sweden

Re: Ship Design Philosophy

Postby AnotherDilbert » Thu Jan 11, 2018 1:04 pm

Ishmael wrote: Consider doubling the size of a ship in each dimension... twice as long, tall, and thick,
mass increases eight-fold ( assuming ship density remains constant )
load bearing area of the structure increases only four-fold.
Agreed, obviously.

But the skin of the hull (the armour) would only increase by four, offsetting the increased internal structure. By TNE, that modelled this (accurately or not), the big ship need less mass fraction for armour and structure.

Note that even "unarmoured" Traveller ships require significant hull thickness.

Ishmael wrote: You'd also be providing 8 times the thrust through 4 times the area ( you'd have to increase the man. drive by nearly 3 times to keep the same level of thrust per unit area )
Again by TNE, this is not a significant problem, at least until the megaton range, since M-drives need very little surface area per thrust.

Ishmael wrote: The square-cube law should also determine the number of hardpoints available to a ship as ship volume increases (assuming hardpoints scale with surface area).
Agreed, and TNE did this by tracking surface area, not "hardpoints". But I have the impression that the level of detail in FFS wasn't universally appreciated.

One hardpoint per 100 Dt is a simple approximation, just as an M-drive of 1% of the ships volume produce 1 G acceleration, regardless of ship's current mass. Both are probably somewhat inaccurate, but simple to use.
Condottiere
Chief Mongoose
Posts: 6232
Joined: Mon Sep 23, 2013 8:23 pm

Re: Ship Design Philosophy

Postby Condottiere » Fri Jan 12, 2018 1:44 am

You could install paper thin fins to increase surface area.

I'm kinda comfortable with the hundred tonne hardpoint formula, since it should be supported by some form of superstructure.
Ishmael
Lesser Spotted Mongoose
Posts: 458
Joined: Fri Feb 08, 2008 3:27 am

Re: Ship Design Philosophy

Postby Ishmael » Fri Jan 12, 2018 5:12 am

AnotherDilbert wrote:
Thu Jan 11, 2018 1:04 pm
Agreed, obviously.

But the skin of the hull (the armour) would only increase by four, offsetting the increased internal structure. By TNE, that modelled this (accurately or not), the big ship need less mass fraction for armour and structure.

Note that even "unarmoured" Traveller ships require significant hull thickness.
The extra armor thickness is used as decks and bulkheads, given the scaled up distances between decks and bulkheads in the larger version. I can no longer check how FF&S1 did things, but if it was as you say, then it is wrong, and it would imply that as ship mass approaches infinity, then the mass ratio for load bearing structure approaches zero.
FF&S2 seems to be proper as far as it goes; I have no idea how it works with real-world structural strength of materials though.
Of, course, that is irrelevant to MongTrav rules, eh?
AnotherDilbert wrote: Again by TNE, this is not a significant problem, at least until the megaton range, since M-drives need very little surface area per thrust.
I don't know about FF&S1 anymore, but FF&S2 requires .005m^2 per tonne of thrust, so you're probably right, as it means a type 'S' scout only needs 10m^2 for its thrusters by FFS2. But even then, doubling the scale of the type 'S' would mean 8 times the thruster area for the same performance even when the available area increase only 4-fold. This would eventually rob area needed for turrets, bays, sensors, etc.
[/quote]
AnotherDilbert wrote:Agreed, and TNE did this by tracking surface area, not "hardpoints". But I have the impression that the level of detail in FFS wasn't universally appreciated.

One hardpoint per 100 Dt is a simple approximation, just as an M-drive of 1% of the ships volume produce 1 G acceleration, regardless of ship's current mass. Both are probably somewhat inaccurate, but simple to use.
I fully agree that keeping track of square meters of hull is cumbersome, and that tracking hardpoints is easier.
But area scales with volume^(2/3) and thus the number of hardpoints a ship may have should too, otherwise huge ships become vastly overgunned when compared to smaller ships, at rates that would allow a type 'S' to have a dozen turrets, if applied equally.
Personally, I use a 100dt cube as a baseline where it has ~600m^2 area. I say each 'hardpoint' uses 100m^2 for convenience. This gives a type 'S' 6 hardpoints. However, I also use hardpoints to mount thrusters, sensors and radiators ( 2 for thrusters, 2 for radiators, one for sensor and one for a turret, et al. ... I have not bothered to work out details ). This gives hardpoints = vol^(2/3) * .285
I know I am deviating from canon and rules, but I prefer my TU to be a little less space-opera-y.
baithammer
Lesser Spotted Mongoose
Posts: 623
Joined: Wed May 31, 2017 2:21 am

Re: Ship Design Philosophy

Postby baithammer » Fri Jan 12, 2018 7:09 am

If your mounting thruster, ect to hardpoints you will end up having to deal with area taken by fuel and the like and then comes the shape of the hull which just makes a mess of things.

Who is online

Users browsing this forum: No registered users and 7 guests