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Engineering Newsletter

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.
But serious, it is not that easy to explain this easy in an other way than
Steve and I did earlier.

So let me ask you a question:

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

If it takes energy, would that not mean that walking up the stairs would
give energy?

And if it gives energy, why use people elevators or lifts?

I'm not trying to make fun out of you, but I'm trying to point you at the
errors in your theory. Since you probably are better at looking in yourself
than I am, my hopes are that with these questions you solve the difficulties
yourself. problems.



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

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.

>Figure out how much fuel it would take to run the reactors & engines enough
>to accelerate the ship (but not its fuel) up to speed.

I've started a calculation, but as far as I can see it now, this method is
not much more efficient than the take-it-all-with-us method.

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

>> 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?


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".

>> 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.

>> Probably all the way in between. But that is not important
>> here, because a reflection means transfer of momentum, 
>> and with it energy. Since the plasma will be accelerated 
>> a lot, it will retrieve a lot of energy.
>Do you mean absorb a lot of energy?  That is a problem with a drop mirrow or
>plasma mirror idea.  But as long as you can do it and get thrust to
>decelerate the ship (the big problem in al this), it might work well enough
>to get us somewhere.  (Assuming the whole thing doesn't melt the ship!)

No, I meant retrieving energy in the form of kinetic energy: The plasma is
accelerated much as the photons are reflected on it.

>On the contrary.  I'm trying to take a very complicated system and make it
>simpler.  Notice I don't have the massive microwave to electric power
>converters of Kevin's origional drive system.  Nor do I have the ultra exotic
>A.I. controled active structure of Forwards drop reflector sail.  Forwards
>design would have had to steer itself, while steering the reflected beam back
>to the main ship, while tracking the main ship over interstellar distences.
> This is not easy, and it is REALLY pushing the envelope of probable 2050

Are you sure that you know how the Dragon-fly or retro-reflection method
works? Because I don't see why a plasma mirror is easier than a solid mirror.

>On the other hand my plasma mirror idea would all take place in the area of
>the ship, and be directly controlable by the ship.  Assuming it wasn't mass
>or energy prohibative, it would clearly be the prefered system.  (Assuming it
>would work of course.)

Indeed, if it wasn't for the mass or energy it would certainly have a pre.
But I'm quite certain that especially the mass would be the problem.