The following information has been posted here before. Old timers can skip
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Rob Dean
Date: Tue, 4 Sep 90 16:36:47 EDT
From: "Robert S. Dean" [email removed]
Subject: (1529) Thoughts on Vehicle Design
I've been at the drawing boards again. After thinking about it, there seemed
to be a few useful(?) reminders to those who want to do a bunch of designs.
SO:
How to Design a Traveller Vehicle Quickly (Rob's Rules)
(without using a computer)
Rule#1: If it doesn't matter, don't worry about it. The most critical example
of this is power consumption for electronics on most vehicles. Unless a
vehicle is extremely small, the total of these values is almost always negli-
ble. Thus, you can size your power plant at the beginning of the process
based on an estimate of power required for weapons, environmental controls
(only if grav plates are being used), and grav/thruster use. There are a
couple of rules of thumb to remember. "Full environment" (basic env, basic
and extended life support, grav plates and inertial compensation) uses
1MW/displacement ton. If your vehicle is heavily armored, the three most
massive components are likely to be the hull, the grav drive, and the power
plant. You can fuss with these numbers to get a good estimate of grav per-
formance.
Rule#2: Decide what is critical first, and set your hull size accordingly. For
example, I wanted a TL12 small vehicle carrying a Plasma-B gun. Energy on
that is 13.5 MW, dictating a power plant of at least 6kl. Usually I build
vehicles around 1)the weapon 2) The accomodations (i.e., if you need roomy
seats for 16 people, this will drive the rest of the design) or 3) The speed.
Rule#3: Decide what factor is being optimized, and ignore the rest--this
usually means that in working on a combat vehicle I set the armor and weapon
and let the speed come out to be whatever it will be, or in building an inex-
pensive vehicle I don't add any "chrome", or in building a fast vehicle I
avoid as many massive add-ons as possible.
Rule#4: Having one vehicle makes a variant very easy--something like the 4
Tiger class vehicles I posted a while ago took 40 minutes to do the first, and
maybe 10 minutes apiece for the others, even including the time to write
everything down again, because 95% of each one was copied from the previous
one.
Rule#5: Unless it really doesn't work, finish every design: Real governments
have put some dreadful designs in the field, based usually on a false concept
of the conditions the vehicle would face, and there is no good reason that
things should be any better in the future. So unless the hull is too small to
stuff everything into, or you've put so much armor on that it can't possibly
fly, finish it. (And assign it to that country/world you don't like...)
Rule#6: Governments don't care what it costs. I have the dubious pleasure of
working for the U.S. Army as a civilian engineer, and this is certainly true.
So when I'm doing military vehicles, I pile in the sensors and other chrome.
How much is 5% extra capability worth in combat???
SOME NOTES ON THE DEAN DESIGN COLLECTION
Since quite a few of my designs have accumulated by this time, I thought I had
better assemble a few comments on the unofficial changes I have made to var-
ious elements of the design systems to allow people to reinterpret them to
taste.
These notes include interpretations, changes, presumed errata corrections and
miscellaneous comments, and are keyed to the design system flowchart.
Basic Hull Design:
I generally ignore the ambiguous maximum armor rule from the narrative, for
two reasons- it makes no sense as there is really no limit to how thick a
piece of steel can be, and increasing price and weight cause their own penal-
ties.
On many vehicles I ignore the turret rules if I can fit all my components into
the base volume. If the hull weight/cost tables were linear instead of dis-
continuous, there would be no difference between the cost and weight (the
important factors) of a hull 10 +40% turret and a hull 14. Power requirements
to move the turret are almost always neglible in the overall design, unless
you have a very large turret on a small vehicle with a tiny power
supply--which has never come up in a "realistic" design.
Power Supply:
The incredible fuel consumption for fission plants given in the book has been
discussed at some length on the list in the past. Let it suffice to say that
I usually use the .003 kl/year rule that I suggested, and anyone who disagrees
may apply an appropriate fudge factor to the endurance of any of my fission
designs. Fuel cells are the best high tech power system for anything up to
about 2 or 3 megawatts. If you need more, go fusion--small fusion plants are
useless except as technological curiosities. I generally have no problem with
installing more energy consuming devices than the power plant can run at one
time, so long as important limits are noted (e.g. no maneuver drive and energy
weapons at the same time) and all important systems can be powered at the same
time (maneuver and life support at a minimum). There has been discussion in
Traveller's Digest and on the list regarding fractional use of power plants.
I consider this to be reasonable, and recent designs list endurance at typical
power settings as well as at maximum power. Fuel usage is considered to be
proportional to energy output, an assumption which should possibly be modified
for small vehicles whose lower energy levels are below the "economy of scale"
factors. Batteries should probably have their control point requirements
ignored, and should also probably be rated in terms of hours at the expected
output requirement. Thus, if you have 1-MW/hr of batteries, you could figure
a ground vehicles speed either on the basis of 1MW of output with a 1 hour
endurance, or 0.5MW output with a two hour endurance, or some other reasonable
combination. My feeling is that there would probably be a design limit to
the speed with which the batteries could be discharged. Starship power re-
quirements can usually be estimated at the start of a design by figuring the
desired life support (all goodies works out to 1MW per disp ton), the maneuver
drive requirment, and any weapons and shields you want to be able to use at
the same time as the maneuver drive.
Locomotion:
My recent designs have been listed with two sets of statistics for maneuver
drives, one being the straight Maneuver=3 or whatever, and the second being
(Thrusters=3250t) or the like. Those numbers are calculated on the basis of
one thruster or anti-grav maneuver unit = 650t thrust, which corresponds to
equal energy consumption for anti-grav units. In this rationalization
thrusters require more energy to do whatever double talk allows them to oper-
ate beyond gravity wells at full efficiency. Although I haven't done it, my
extrapolation would permit thruster units to be placed in any size craft, so
long as the unit is at least 0.4 "units" large. (5.4kl minimum). For most
player-class craft, these rules result in approximately the same amount of
total acceleration capability. I have a disagreement with the rules over the
agility question, which I have discussed at great length before. In essence,
I have always played that ships may have multiple devices which use the "same"
power (but not at the same time), so that maneuver power can be fed to the
weapons as long as you are willing to accept a reduced or zero acceleration as
a result. Between that habit, and some calculations about vectors, angles and
so forth of space combat, I am firmly convinced that the most important factor
in a ship's ability to avoid being hit in space combat is dependent on the
gross effects of its maneuver drive, and that agility should therefore be
equal to drive rating, provided that you are not "double dipping" the drive
power for weapons. I have always believed that this was the intent of High
Guard, and I think it works well with the thruster tons suggestion above for
acceleration, since it has the desired effect of making heavily armored ships
slow and non-agile. More comments on this under weapons.
In the thrust based suspensions for smaller vehicles, it should be noted that
the minimum thrust for standard grav is one ton, the minimum for low power
heavy grav is 0.4 tons, and the minimum for low power light grav is 0.1 tons.
Except at the very lowest thrusts and power levels, a tradeoff analysis will
always favor standard grav. Example tanks in 101 Vehicles using LP-HGrav
could have their overall costs reduced by 50% by using std grav, even includ-
ing the need for additional fusion plant and higher thrust to maintain per-
formance.
In contact based suspension, the minimums for volume of wheels and tracks as
revised by the errata (1.5 and 2% respectively) are fairly generous. Striker
heavily penalized high ground pressure vehicles (reasonably), and although
the complexity is probably not merited in MegaTraveller, I have always aimed
to keep my ground pressures around the 5-6 dividing line between high and
low off road performance in deference to reality. The rules are also unclear
as to whether P/W should be figured using total power or power after all other
devices are powered. Because of the method of calculating transmission size,
I have assumed the former, which means that the "power requirments" of the
wheels and tracks can pretty much be ignored. If there is any doubt, the
power plant must supply at least enough to power the suspension, but I'd
figure that into the P/W. Thus, it's only effect is to put a lower boundary
on a vehicles power plant size, which is unlikely to be a problem unless you
are trying to use batteries or some such.
Communications:
In almost all cases, except for very small vehicles and low tech level de-
vices, the only important factor for communicators in the final design is
price. I usually don't get too worked up over having .03MW of power used for
electronics in a craft with 2MW of power, so I frequently ignore them when
adding up power requirements. I also usually like to have a back-up communica-
tor on board all spacecraft. Just a matter of taste. The credits saved by
leaving out the backup are usually negligible in a starship design.
Sensors and Electronics:
As with communicators, most of the time price is the only important factor.
Lower tech large EMS arrays may end up using enough power to worry about, and
military vehicles sensors may be important. Don't forget that active and
passive EMS include all the smaller single purpose electromagnetic sensors.
Weapons:
The meson gun is the king of starship weapons. Nothing else available at
Imperial tech levels will kill a ship with one shot. Armor is irrelevant
to meson guns, and screen are really only effective against the smaller
ones. Thus, no battleship needs to be bigger than necessary to carry and
serve the meson gun. Since agility is one of the better defenses, and my
version of agility calculations places a premium on light armor, I'm finding
that there may be some limited utility in large particle accelerators to
damage and inhibit the construction of unamored meson gun carriers.
Lighter armor also gives fighter and SDBs something to do, though they had
better have large computers to be effective at TL15.
While the rules are clear about turrets taking up 13.5kl regardless of the
number of weapons installed, the TD example starship construction from
issue #14 incorrectly shows triple laser turrets taking up 40.5kl. I also
usually figure that the turret weight about the same regardless of the
number of weapons, which is probably not what is intended. On most ships
the difference is not significant. Any of my ships without specified missile
magazines need to load missiles in cargo space.
I have used turret mounted direct fire mortars in some designs of TL8 and 9
military vehicles. These are not permitted by the rules, but exist in the
real world, so I extrapolated.
Cluster bomblets, tactical missiles, and rocket launcher artillery should be
put back into the game from Striker for use in military adventures.
Mass driver gun calculations should give rate of fire in rounds per second,
not round per minute. (Error in Striker translation). Without making this
change, MD guns are probably not cost effective.
Point Defense rules need to be put back in from Striker.
Screens:
All meson screen power consumptions should be divided by ten according to
Trav Digest#14. (e.g. UCP1=.015, UCP2=.03) I have left specifics of
obscuration devices off of recent military vehicle designs. Their power,
weight and cost are negligible, and if needed I would specify a reasonable
number before combat (say 3 or 4 dozen maximum). I don't like the little
sandcasters because I don't think the particles would stay airborne long
enough to do much. No rules for any of these gadgets are provided, either.
Bridge:
I usually go ahead and put in basic env, basic ls, ext ls, grav plates and
inertial compensators for the entire volume of a starship. I haven't found
that it drives power requirments up too horribly for merchant ships.
To maintain consistency, I do calculate the control point requirements for the
hull, despite my difficulty with increased armor requiring more control.
For a military starship, there can be no excuse for not putting in the biggest
computer available at your tech level.
Based on the Starship Operator's Manual descriptions, I almost always use
holographic linked panels when available, because I figure the using character
would want them. I try not to install more add-ons than I have crew members
to use them. 101 Vehicles has an implied rule change allowing you to use
linked panels without a computer, which I have never taken advantage of.
Accommodations:
Rule 3, reduced vehicle gunners, still looks bad after the errata: (C+S)/W,
since S is usually substantially larger than C, and I'd think that your
computer would have more to do with it. What I use is X=C/(W/S) and some
common sense.
Rule 4, supplanted vehicle commander says X=(T-S)/C, which has the effect of
making it impossible to get rid of the vehicle commander if the total cost
of the vehicle apart from the sensors is greater than 100,000C/TL. The best
value of C/TL is 8 at Comp 9, TL15, and Cr800,000 doesn't buy much of a
TL15 grav tank. I think that X=(T/S)/C, plus some common sense works better.
In very light vehicles, I usually calculate the weight of seats at 0.1t rather
than 0.02t to allow for the weight of the passenger. This is almost always
ignorable on large vehicles.
Starship command crews look awfully bloated to me, especially in cases where I
am carrying a 130 man marine company on a small vessel. I usually reduce them
with the same formula as the bridge crew, which satisfies my prejudices. If
the total was less than 10, there was no reduction.
Fuel:
If necessary, ships could jump as soon as the fuel processor had done enough
fuel for the jump, rather than waiting for the full load to be processed.
Fuel scoops and purifiers are almost always economically justified.
Design Evaluation:
For all of my vehicles unless otherwise noted, the prices *do not* include
a bulk discount. Cost of small craft is included unless otherwise noted, or
a generic description (e.g. 1*4ton vehicle) is the only mention.
In grav vehicle speeds, I usually give them in terms of the "vacuum" speed,
so they should be multiplied by .9 for standard atmosphere, to taste. I have
also interpolated values on occasion. If you tried to use the rules as
written, many airframe configuration craft could go faster in thin atmosphere
than in a vacuum, which doesn't look right. Purists might wish to recalculate
lift requirements for grav vehicles based on local gravity. I don't usually
bother.