Subj: Traveller Digest 280
Date:	95-05-09 19:24:43 EDT
From:	traveller@mpgn.com
To:	traveller@mpgn.com

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			    TRAVELLER Digest 280

Topics covered in this issue include:

  1) Re: R: Sensors in space combat
	by Neil Taylor <neil@owl.uk.gdscorp.com>
  2) RE: Realistic Thrusters
	by Neil Taylor <neil@owl.uk.gdscorp.com>
  3) Re: TRAVELLER digest 279
	by pbertigl@io.com (Paolo Bertiglia)
  4) Re: Saturn V
	by Mark Clark <markc@brahms.udel.edu>
  5) FYI- Possible NASA Planet H
	by "KMCCARTHY" <KMCCARTHY@QMGATE.OSC.HQ.NASA.GOV>
  6) UK RESIDENTS UNITE!
	by A.S.Lilly@bnr.co.uk (Andy Lilly)
  7) Re: Broken Thrusters
	by CyHiggin@aol.com
  8) Re: Electronic Warfare
	by CyHiggin@aol.com
  9) Atmosphere resistance.
	by adou01@cs.auckland.ac.nz (Andrew Richard  Doull)

----------------------------------------------------------------------

Date: Tue, 09 May 1995 08:38:33 EDT
From: Neil Taylor <neil@owl.uk.gdscorp.com>
To: traveller@MPGN.COM
Subject: Re: R: Sensors in space combat
Message-ID: <00990170.BBA3B602.26@arc.uk.gdscorp.com>

merrick@Rt66.com (Merrick Burkhardt) writes:

>PS-I have some sensor rules I've hashed together if you'd like to see them
(if 
>you haven't already).  Let me know and I'll send them to you (don't wanna 
>repost them here and waste peoples' time.

Sounds like now's a good time to thrash out some ideas & rules for sensors.
I'd 
especially like to see a goo d distinction between the ease and *results* of 
passive vs. active detection.


--------------------------------------------------+
-- Neil Taylor              neil@uk.gdscorp.com --|
-- Graphic Data Systems Ltd,                    --| 
-- Wellington House, East Rd, Cambridge CB1 1BH --|
--------------------------------------------------+

------------------------------

Date: Tue, 09 May 1995 09:04:07 EDT
From: Neil Taylor <neil@owl.uk.gdscorp.com>
To: traveller@MPGN.COM
Subject: RE: Realistic Thrusters
Message-ID: <00990174.4DFE1CE2.26@arc.uk.gdscorp.com>

Maximillian Callahan <callahan@cts.com> writes:

>Have you tried to build a TL7 rocket that can hit orbit, please do because
>thoes of us that have, have failed.
>And in an attempt to get a respones from the nice people at GDW, I would
>think that GDW would at least get this portion of the rules right, as in
>the wilds Chemical Thrusters are what a lot of worlds would be using at
>they try to reclaim the stars.

Nah! If there's one thing GDW *don't* do, it's reality checks!  Look at the
bulk 
and weight of "ground cars" and their fuel consumption - you might pretend
its a 
limousine, but try building a "European compact" (or whatever it is USAns
call 
them) "cars" to me...

Try building a helicopter and comparing it to a real Sikorsky (cf recent
posts)

Look at the heat exhaust of a small grav car or grav bike.

To me, a Golden Rule of hard-SF has to be to check the low-tech elements
against 
real-world equivalents.  You look ****** silly when you get those bits wrong!
--------------------------------------------------+
-- Neil Taylor              neil@uk.gdscorp.com --|
-- Graphic Data Systems Ltd,                    --| 
-- Wellington House, East Rd, Cambridge CB1 1BH --|
--------------------------------------------------+

------------------------------

Date: Tue, 9 May 1995 05:16:14 -0500
From: pbertigl@io.com (Paolo Bertiglia)
To: traveller@MPGN.COM
Cc: macrocosm@wri.com
Subject: Re: TRAVELLER digest 279
Message-ID: <199505091016.FAA04479@pentagon.io.com>

>Date: 07 May 1995 22:03:41 GMT
>From: Rob_Prior@nynet.nybe.north-york.on.ca (Rob Prior)
>To: traveller@MPGN.COM
>Subject: High Science, Low Tech
>Message-ID: <3229187639.131433288@nynet.nybe.north-york.on.ca>
>
>If you want to see what a properly designed low-tech device looks like,
check
>out some of the "sustainable technology" designs used at the UNICEF Village
>(in Kenya).  These devices make use of local material and can be made by
>virtually anyone, but are optimized in terms of 'science'.  The tin can
>stove, for example, is designed for maximum cooking from minimum fuel.  The
>science behind these devices is several tech levels above the technology
>needed to make them.
>
>Of course, this is an issue that Traveller avoids entirely (the difference
>between knowing something and being able to use the knowledge).  For
example,
>the germ theory of disease is tech 4 (by discovery), yet once you know about
>it even tech 0 can use it.  So which tech level is it really, 4 or 0?  

A lot of good books (and rpg settings) are build around this concept: 
Low tech level and high teory level (at least in some fiels).
Lot of steampunk fall in this typology (lefting out ether), Ancient 
technology use without a proper theory is another.

But maybe it isn't a theory level: Egyptians know about steam power and 
Sumers about electricity but their societies didn't need those technologies.

Maybe that the life in Egypt and in Sumeria would be a lot better if they 
made industrial application of those knowledge but that would made a
social revolution (as it happened in England some time later) and the 
powers that drive those cultures didn't need it.

Maybe in our future someone will wonder why, as we have the technology,
our culture don't have used the cold fusion that is 'so simple'...

So when we talk about tech level we speak about the theory and the technology
actually used by that society, not the overall knowledge of the society.

Of course when we have a society that start with an high tech level and for 
some reason things go worse we have some interesting situations.
(It has ever happened in our history? Medieval tech level was lower than 
Romans?)

I think that the teach level is at least a bidimensional variabile (maybe
more)
and that trying to describe it all with a single value lead to 
unrecoverable troubles.

Ex:     Field/level     1       2       3       4       5       ...

        Medicine                X

        Informations    X
        treatment

        Transports                                      X

        .........        

ecc.

Paolo.

-----------------------------------------|    ____
Paolo Bertiglia, Scout, Database Adminis-|   ////\\     Communism and
trator, rpg and comics and SF collector, |  //_  _\\   capitalism are
wannabe writer, designer, hairier,       | {( 0  0 ) two faces of the
father, smarter, ecc. ecc. ecc. ...;),   |    ~ ^ /    same coin that
from Italy of course.                    | --/ <>/\---   someone else
-----------------------------------------|     ~ \ \  \      has won.


------------------------------

Date: Tue, 9 May 1995 08:12:51 -0400 (EDT)
From: Mark Clark <markc@brahms.udel.edu>
To: traveller@MPGN.COM
Subject: Re: Saturn V
Message-ID: <Pine.SOL.3.91.950509080423.10148A@brahms.udel.edu>

One thing we haven't discussed is that the Shuttle and the Apollo 
launchers are fundamentally different mechanisms.  While the Saturn 
system could deliver large loads to orbit, it was unable to bring back 
much more than crew and some moon rocks.  The Shuttle, on the other hand, 
is able to return from orbit with rather large objects, making it 
possible to retrieve and repair items from orbit.

This is not to say that the Shuttle is the only way to go - the Soviet 
(now Russian/CIS) program is proof of that.  However, the Shuttle is a 
highly flexible system that offers benifits that Apollo does not.  

------------------------------

Date: 9 May 1995 08:39:42 -0500
From: "KMCCARTHY" <KMCCARTHY@QMGATE.OSC.HQ.NASA.GOV>
To: "New TML Broadcast" <traveller@MPGN.COM>, macrocosm@wri.com
Subject: FYI- Possible NASA Planet H
Message-ID: <n1412113366.70113@QMGATE.OSC.HQ.NASA.GOV>

                       Subject:                               Time:8:37 AM
  OFFICE MEMO          FYI: Possible NASA Planet Hunter       Date:5/9/95

FYI,

[Extract of a longer article]
SPACE NEWS, MAY 8-14, 1995

AMES TEAM STUMPS FOR PLANET HUNTER, p 26
  NASA's as-yet-undefined strategy for locating planets around other stars
could breathe life into a $100 million orbiting telescope that scientists at
Ames Research Center want to fund.  the telescope, called FRESIP for the
Frequency of Earth-Sized Inner Planets, would be launched into a quasi-stable
orbit about 1.5 million kilometers from the Earth.  FRESIP was dealt a
setback
in February when NASA officials rejected it in the latest competition for the
agency's series of low-cost Discovery Missions.  FRESIP advocates say the
advantage of their telescope is that it would home in on the habitable zone
around stars where Earth-like planets may exist.


------------------------------

Date: Tue, 09 May 1995 15:21:02 +0100
From: A.S.Lilly@bnr.co.uk (Andy Lilly)
To: xboat@MPGN.COM
Cc: traveller@MPGN.COM
Subject: UK RESIDENTS UNITE!
Message-ID: <199505091525.LAA25334@Mithril.MPGN.COM>

I am interested in determining which members of traveller and xboat reside
in the UK, given the far cheaper costs of postage (for swapping stuff, etc.)
here rather than with the US. Also, given sufficient support, we might be
able to organise some form of event over here, or keep each other in touch
with organised UK events. I do not wish to set myself up as social
secretary, but I would be willing to accumulate a paper list of UK residents
(I can't keep it on computer because of the Data Protection Act!) which
people can then use as they see fit.

I see a lot of .uk names on the list now and rather than contacting each
directly it would save time if they would contact me. Also I know there are
some people on compuserve, etc. who are in the UK but I cannot identify them
by their e-mail address.

Therefore, would any UK residents wishing to make themselves known, please
e-mail me directly with details of your name, postal address, telephone
number, Traveller interests, any particular desires (want to swap X,
desperately seeking Y, want to meet other players, want a PBEM, have
knowledge of a good RPG retailers), etc. and I'll see if anything
interesting comes out of it (no promises!)

If anyone has any particular requirements (not allowing their name to be
divulged to other list members or anything) then please feel free to say.

Andy


------------------------------

Date: Tue, 9 May 1995 11:52:51 -0400
From: CyHiggin@aol.com
To: traveller@MPGN.COM
Cc: callahan@crash.cts.com
Subject: Re: Broken Thrusters
Message-ID: <950509115249_112340310@aol.com>

From: Maximillian Callahan <callahan@cts.com>

>>If you are thinking about the low tech thrusters I think
>>that they are good enough. If you consider the Shuttle it
>>need large fueltanks just to get it into orbit. Low tech
>>fuels are not efficent if you consider the weight and 
>>volume, but they are all we have at the moment.

>>Tommy Grav

>WRONG!! The shuttle is only 66.7% fuel tank and it can hit orbit
>Under FFS it would have to be 1000% fuel tank to hit orbit. The FFS
>thruster rules are broken. Feel free to prove me wrong though, post a
>Tech 7 design that can hit orbit (with annotations) under The realistic
>thrusters rules from a size 8 world under 1g and I'll eat this post.
>		callahan@crash.cts.com

I've been watching this discussion for a few issues, thinking about
jumping in, but have been too lazy.  However, I have nothing better
to do today, since the flood of May 8 is lapping over our front steps
and I'm not going anywhere.  

The thrusters ARE broken.  The fuel consumption is somewhat 
*better* than the real-world, but the thrust-to-weight ratio is
pathetically low.  As an illustration, they give a TL5 liquid fuel
rocket 6 tonnes-thrust per ton of motor; in the Real World (tm), the 
V-2 rocket motor (a TL5 LF rocket) developed 20-30 tonnes-thrust
per ton of motor.

GDW also requires absurdly high Delta-V numbers to reach orbit:
they claim Earth requires 0.64 G-hours, which equals 22.5 km/sec 
delta-V.  In the Real World(tm), we require less than 10 km/sec (0.3
G-hours) to reach low Earth orbit.

Finally, GDW's formulas for calculating G-hours are broken.  Here's
the Real World formulas that apply to the Real World space program:


    Mass Ratio MR = Wl / Wef
                    Wl = Loaded Weight 
                    Wef = (Loaded Weight - Reaction Mass Weight)

    also:      MR = e ^ (dV/Ve)

    Exhaust Velocity Ve = 36,000 / FC
                    FC = Fuel consumption in tonnes/hour 
                            (yes, the number from FF&S)
                    Ve is in m/sec

    G-hours = ln(MR)/FC

    Delta-V = ln(MR)*Ve
              Delta-V is in m/sec

    Hohmann Transfer Orbit:
        dVh = Ve1 * sqrt( R2/(R1+R2) ) + Ve2 * sqrt( R1/(R1+R2) )
            dVh = total delta-V (m/sec) of Hohmann transfer orbit
            Ve1 = Escape velocity (m/sec) of start body
            Ve2 = Escape velocity (m/sec) of end body
            R1  = Radius of start body's orbit
            R2  = Radius of end body's orbit

     Orbital Velocity
        Vo = sqrt( R * G)
                Vo = orbital velocity (m/sec)
                R  = Radius of orbit (m)
                G = G (gravity) at altitude of orbit (m/sec^2)

      Escape Velocity
        Vee = sqrt (2*R*G)

      Delta V to achieve Orbit is, ideally, a Hohmann Transfer Orbit from
ground (which has the rotational velocity of the planet's surface as its
"orbital velocity") to Orbit, plus some extra for getting above the
atmosphere,
say +1-2 km/sec.

    Because of the ridiculous numbers for thrust-to-weight ratios in FF&S,
I arbitrarily changed them to be more in line with the Real World(tm); see 
below:

Chapter 9: Sublight (Maneuver) Drives

Page 70

(change): In the Self-Contained Thrusters table, use the following values for
thrust-to-volume/weight ratio instead:

TL	Type		Th
----------------------------
5	LF Rocket	20
6	LF Rocket	40
7	HF Rocket	40
8	AZHRAE (Rocket) 40

Final note: George Herbert's corrected tables for MegaT's Hard Times low-tech
rockets are also fairly accurate (in spite of he and Steve's quibbling over a
few
Isp's here and there), if you want a more detailed treatment of different
types
of sub-TL9 rockets.

                                                               -- Cynthia 

Brief Glossary:
       Isp  = Specific Impulse - time that 1 pound of rocket fuel can produce
                                            1 pound of thrust. Unit: seconds.
       delta-V = change in velocity required to do something. 
                     Unit: m/sec, km/sec, mph, furlongs/fortnight, pick your
favorite...
                       
       G-hours = same as delta-V, different units: Gravities * hours. Since
                       this is an acceleration * a time, it resolves to --
Velocity.

        Mass Ratio (Mr or MR) = Ratio of mass of fully fueled ship to 
                       mass of ship after all reaction fuel has been burned.

        Exhaust Velocity = what it says; how fast the hot stuff is spewing
out
                       the back end.  Has a direct relationship to how fast
the ship
                       can go....

         Hohmann Transfer Orbit = the absolute *minimum* delta-V to get from
                       point A to point B.  Used by people with limited fuel
supplies
                       who have a long way to go and no great hurry to get
there.

         Orbital Velocity = how fast you have to go around the planet to keep
from
                       falling down.  Those of you who have taken Dynamics in
college
                       had to go thru the agony of actually deriving this
equation from
                       those for rotational velocity and angular momentum,
and may
                       understand WHY you don't fall down if you go fast
enough.  I
                       know I did at one time.  Fortunately that part of my
life is a fast-
                       fading memory....

          Escape Velocity = like Orbital velocity, only faster; fast enough
to go
                       into a parabolic orbit around the body in question.
 Unlike
                       ellipses, parabolas are open-ended.... you don't have
to come
                       back.         


         Oh crap, it's raining again!
     

------------------------------

Date: Tue, 9 May 1995 11:52:52 -0400
From: CyHiggin@aol.com
To: traveller@MPGN.COM
Subject: Re: Electronic Warfare
Message-ID: <950509115252_112340338@aol.com>

Roger "StarWolf" Myhre:

>>Also considering the technological improvements used in the Traveller 
>>universe in other areas sensor technology seems pretty pathetic.

>As a former sensor operator from the Norwegian Navy, I'll agree 
>partially. Firstly having too complex sensor rules just bogs the 
>gameplay down. Most people just doesn't have the faintest idea what 
>electronic warfare is about. Most people have this feed in by series 
>as Airwolf, Knight Rider, Star Trek which are so far from the thruth 
>you can get. But no ine objects, why, because it would destroy the 
>story.

As a former U.S.Navy petty officer, and wife of a former U.S.Navy
submariner, I have to agree.  For those of you who want to get a feel
for what real electronic warfare is liked, read Tom Clancy's novels such
as "Hunt for Red October" and "Red Storm Rising".  Even there, 
military folk say he errs on the side of having all the equipment work 
properly far too often -- other than that, he is quite accurate.  

For games that capture the feel of electronic warfare, Harpoon II in 
both the board and computer incarnations is quite good.  As for TNE,
if you use the TNE combat/sensor rules (not the other games, BL & BR),
and have a referee who knows what real electronic warfare is llike,
you can get close.

Note: a while back someone was saying something about the inaccuracies
in Tom Clancy's submarine novels.  I am given to understand, by 
submariners that I know, that his novels are very, very accurate, and
that the inaccuracies are of a deliberate nature -- that is, he couldn't
use the correct instances in his novels because they are CLASSIFIED.
He has a reputation for annoying security officers by doing things like
that -- learning classified information from his military friends, going out
and finding a non-classified source of the same information (like his
infamous
pictures of the Soviet Brightstar installation in "Cardinal of the Kremlin"),
and publishing only what he can point to as being available from non-
classified sources, thus staying legal, even though he originally found
out about things thru classified channels.  Thus the deliberate errors in
the submarine stuff.

                                                     -- Cynthia
 

------------------------------

Date: Wed, 10 May 1995 09:05:12 +1200
From: adou01@cs.auckland.ac.nz (Andrew Richard  Doull)
To: traveller@MPGN.COM
Subject: Atmosphere resistance.
Message-ID: <199505092105.JAA15664@cs26.cs.auckland.ac.nz>

I am in the middile of designing a weapons design sequence for
electromagnetic
catapults.  Basically, these are spinally mounted weapons which have been
optimised for power efficiency and de-optimised for volume and length, and
operate like mass-drivers.  In particular, they favour very large designs,
such as could be used to launch a ship from the surface of a planet or make
an in-system transfer.  Military applications include planetary bombardment.
 
I have run into a problem.  "Footfall" by Larry Niven and Jerry Pournelle
describes the use of hyperkinetic weapons, basically chunks of rock which
cause damage purely as a result of the energy they gain during their drop
from
orbit.  I thought this would be good to include for electro-magnetic
catapults
and it turns out this additional energy causes a lot of damage (Obviously).
It can be determined from start distance, object mass and surface G of the
planet.  In fact, it overwhelms most other forms of damage, especially when
you start converting MW to kilotons of nuclear explosive damage (At 5 x 10^6
MW to a tonne of explosive, unless I am mistaken), which rather begets the
question why put a convetional warhead in such a missile? (Direct to GDW).
But I digress.
 
Basically, I do not know how much energy is reduced by atmosphere resistance.
I suspect a simple answer would be a subtraction from either velocity or
final
energy which would cause small objects to burn up and large ones not to lose
much damage as friction generates a shockwave which causes additional damage.
But I do not have any idea as to the scale of such reduction or whether this
is in fact correct.
Any ideas.
 
A.D.Venturer (aka Andrew Doull).

------------------------------

End of TRAVELLER Digest 280
***************************


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