Re: Engineering Newsletter

[KellySt@aol.com]

Subj:  Engineering Newsletter
Date:  Sun, Dec 3, 1995 4:24 PM EST
From:  T.L.G.vanderLinden@student.utwente.nl
X-From: T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)
To: KellySt@aol.com, hous0042@maroon.tc.umn.edu, stevev@efn.org,
rddesign@wolfenet.com, RUSSESS@cellpro.cellpro.com,
jim@bogie2.bio.purdue.edu, zkulpa@zmit1.ippt.gov.pl

ReplyFrom : Timothy
ReplyTo   : Kelly
Subject   : Humans and stairs

>Hold your arm out to you side.  Tell me it takes no effort (energy) to hold
>it there.

>> Even if I could convince you that it took no energy to keep
>> it there, you would probably say that the only possibility
>> was that my feet got colder.

Don't bother.  I refused to get into an argument over levitating arms.

>> Does it TAKE energy to walk down the stairs or does it GIVE energy?

Actually both take energy since your accelerating and decelerating masses of
your body.  Though obviously going down you don't need to bost yourself up a
gravity/potential energy well.

===========================================================================

ReplyFrom : Timothy
ReplyTo   : Kelly
Subject   : Prelaunching

>No, Kevins starship design is propelled by a photon (maser) beam.  My
>origional Explorer design is propelled by fusion powered mass drivers.  I
>call it an externally feed system since the fuel is thrown out ahead of the
>ship by a launcher in Sol.  (See my Explorer  starship design page on the
LIT
>site.)  Thats probably the central thing confusing you.  Unless your
>confusing the Explorer ship with the plasma mirror design I came up with
more
>recently.

>> Ah, now I see. But you agreed that both prelaunching and
taking-all-with-us
>> takes the same amount of energy/fuel. But after understanding it, I think
>> that that prelaunching is more economic with energy.

Energy total yes.  Energy on the ship, no.  Since the ship power requierments
are the show stoper of the system..

>> Furthermore, prelaunching only works for acceleration, not for
decelleration.

Agreed, but then you can say the same thing about photon sailers.

>> It would be best if we could find a solution without using the
interstellar
>> particles, but at the same time we should keep in mind 
>> that we have to protect us against it. This may sound a 
>> bit contradictory but a general solution would be best. 
>
>How about working out a high and low range based on the most and least mass
>expected out there? 

>> >That would be fine with me, but I have a feeling that using the ISM to
break
>> >will not work. But OK, does anyone have the number of particles per cubic
metre?

I listed some assumptions on my Explorer Web page in LIT.  I think bottom
assumption was a hydrogen atom every cubic centameter or 4.

===========================================================================

ReplyTo   : Kelly
ReplyFrom : Timothy
Subject   : Plasma mirror

>Don't understand you question.  I was assuming it would depend on the mass,
>but I didn't know how much mass that would be.

>> I guess, I was having difficulties with the expression "I don't have a
handle".

Sorry for the slang.  English to englist translation.  I don't know what the
answer is.

>> Ions are particles too.  They may have small masses, 
>> but if you have enough of them you could build a
>> complete dragon-fly sail.
>
>I don't know which system would be lighter, but of course we couldn't build
>the dragon-fly system, so thats kind of a mute point.

>> >>We can't build a dragon-fly system? I don't agree with that. Just make a
big
>> >>(heavy) mirror and detach just before the Asimov is going to decelerate
and
>> >>the mirror is going to accelerate.

Sorry that won't work.  As the outer mirror moves away from the ship it has
to continuosly reshape itself to refocus on the smaller catcher mirror/sail
on the ship.  Also without the anchor on the ship it will tend to flutter and
shift off course due to slight variations in beam, ISM, mirror reflectvity,
seperation torque, etc..  This of course ignores the fact the sail isn't
rigid, and will tend to crumple once its free of the ship.   

Forward realized this, thats why he had an army of autonomus robots go with
the outer sail to keep it working.

Kelly