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Re: Engineering Newsletter

to:  rddesign@wolfenet.com
To: KellySt@aol.com

>>> Heat load on the asimov:
>> Kelly
>> This is way outside of my knowledge but couldn't this heat 
>> be expelled like exhaust and added to the thrust? Heat is 
>> just hot particles, isn't it?

No such luck.  Heat is eiather the thermal vibration of the molecules in an
object, or infared radiation (life in a radiative heater).  Can't think of
how we'ld pump all the heat out of the ship fast enough to keep it cool.

ReplyTo  : Kelly
ReplyFrom: Timothy
Subject  : Drawings

>> About the drawing: where did you plan the shielding. And 
>> does it ride along with the hab ring, thus at 1 g?
>> I had in mind that we made a shielding tube in which the
>> hab-sections rotated. So then the shielding would not 
>> move and would not create an extra outward stress-factor. 

I was thinking of having the shielding in a fixed U shaped shielding trough
that runs around the inside of the outer hull (the open end of the U points
inward).  If the shielding is made of steel instead of lead, the hab
centrafuge tracks can run around on the top edges of the U.  (of course the
steel would be at least 3 feet thick!)

>> (Tip: jpeg images would be about 4 times smaller, so would
>>  mean a less bytes with almost the same image quality)

Now if Rick would get a JPEG viewer.  ;)

>Far larger than that.  A multi generation ship would be technically far
>harder then a fast relatavistic ship.  To have half a chance it would need
>be compleatly self contained and self sufficent.  With enough fuel and
>resources for decades to centuries.  Say a couple times the size of
>and with a population of hundreds of thousands of people.  All that assuming
>a big jump in technology to support it all with a crew that small.

>> Indeed the ship itself would probably bigger than a rel. ship but, I don't
>> think that energy will be a problem. The amounts of energy needed for a
>> ship are far more. ---- 4.4E14 Watts per person per year. The rel. ship
>> engine would use 1000 times more per second. 

Of course instead of a 5 year (ship time) trip, your talking about centuries
to thousands of years, and a crew 10-1000 times larger, and a proportianatly
larger ship, etc...  You might make an energy savings, but it wouldn't be as
dramatic as you might expect.

>> So now the only problem is to build that large ship. Material
>> from astroids ---  Making a self sufficient system should
>>  not be that hard with enough energy available.

Building things takes skills, tools, and materials, as well as power.  Of
course we didn't give the ship tremendous power reserves.

ReplyFrom: Timothy
ReplyTo  : Kevin and Kelly

>>> _BUT_
>>> the conversion would take place on the antenna itself.  
>>> diodes wired directly onto the metal mesh would do the
>>>  power converting and the mesh  (of special radiator fins 
>>> if need be) could radiate the heat.  we have thousands and 
>>> thousands of square meters of antenna, it would serve as 
>>> an exceptional radiator.  ----
>I'll buy this part.  With the hundreds to thousands of square kilometers of
>mesh you've been taling about you have a lot of radiator space.  Asuming you
>can radiate the energy away fast enough to keep everything down to operating
>temperature.  If you want supper conductors this could be dicy.  They like
>cold temps and radiators like it very hot.

>> I don't buy that part: Take 1 square kilometre or 1E6 square metres, that
>> means 1E18/1E6=1E12 Watt per square metre. Take 10% of that and you get
>> Watts of lost energy per square metre. That sure would melt anything away.
>> Even with thousands of square kilometres it is still too much.

Good point.

Subject  : Photon energy
ReplyTo  : Kelly
ReplyFrom: Timothy

>>no, I am talking about the momentum of the photons as opposed to the 
>>momentum of the ions the "Asimov" will eject as exhaust.  Those will be 
>>Hydrogen ions or maybe Xenon moving at .9996 or (.99996, depending on how 
>>much energy you can invest) C  at these speeds, a small mass flow is 
>>sufficient to slow us down (or speed us up depending on which phase of 
>>the mission we are in) at a constant 1 G.
>>> This was clear to me, but rethinking this made me 
>>> realize that your method can't work. Because adding 
>>> momentum to the Asimov will only make it move
>>> faster. Transforming it to reverse momentum would 
>>> surely break one of the basic physic laws.
>No Tim.  The momentum of the microwave is simply added load on the antena
>support structure (which is an extreamly unlikely structure) assuming it can
>take the load the power (electric) them feeds the engines which use it to
>produce forward or backward thrust.  No violation of conservation of
>momentum.  As long as the engine is powerful enough (and antenna strong
>enough) to overcome the thrust load of the photon sail effect of the big
>antenna.  Every thing is fine.

>> >> No, that's not what I meant. I think that the energy that is gained by
>> >> receiving the photons is not enough to overcome the velocity gain that
>> >> get by receiving these photons. So a powerful engine doesn't work
>> >> there isn't enough fuel.

This can't be right.  If it was no solar electric drive could ever work.
 Besides it sounds like you have a conservation of energy contradiction here.

Subject: Solar array
ReplyTo  : Kelly
ReplyFrom: Timothy

>Are you talking about a 5 kilometer disk a million kilometers from the suns
>surface?  Does this not strike you as a servicing problem?

In fact I was talking about a 50 kilometre disc...

>Solar Power Density out here by earth is 1.35 KW/m^2 not the 5E8 Watt/m^2,
>but the equipment will be a lot more likely to keep working.

>> I agree completely, but having it so near Earth means a much bigger array.
>> 5E8/1.35E3=3.7E5 times bigger to be exact. That is about 1.5 times the
>> surface of the Earth!!! That seems to be an even bigger problem :)

Ok, eiather system is infeasable.