Re: starship-design: Laser or maser?

[T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)]

Kelly wrote:

>>>>300 and 385 kilometer diameters don't seem like a headache...
>>>
>>>A 300-400 kilometer laser array?  Again it would be a bit hard to fit on
>>>our moon.  Harder to sycronize since the frequencies are shorter.  Also the
>>>sail has now gone from a wire mesh to a reflective sheet.
>>
>>Hard to fit on the moon? I don't understand, its diameter is 3476 kilometers.
>>The frequency is indeed increased by a factor 3, however having a solid
>>floor helps a lot.
>
>If you have to find a position for the array that has constant direct line
>of sight at all times.  Your limited to a small polar region.  The farther
>the target star is from true north or south the narrower the polar region.
>Also the platforms must be in direct line of sight so they can adjust for
>one anothers movement (yes platforms mounted on the Moon will more around a
>bit).

No, that polar region is not small, it is rather big.
If a star deviates 45 degrees from the rotation axis of the moon/planet, it
can be seen downto the 45th longitude. (There is a small band in wich the
Sun and other planets will move along (on Earth that is between +23 and -23
degrees).)

>>I wonder are semiconductor lasers more efficient and cheaper than ordinary
>>lasers. What will be the costs compared to masers which cannot be made in
>>semiconductors?
>
>Can't remember.  I thought free electron lasers had the highest efficency?
>
>>Also on the receiving side, what are the pros and cons?
>>On the receiver-end we not only need a mirror, but also an absorber. Are
>>photocells better than skottky diodes?
>
>Why an absorber?

During the deceleration phase, energy is used to accelerate repulsion mass.
(I know, you proposed some ingenious reflecting system, so that the
EM-radiation directly accelerates the repulsion mass, but somehow that seems
to ingenious.)

>>Has anyone an idea where to get this kind of information?
>>
>>What are the disadvantages of a reflective sheet compared to a wire mesh? Is
>>it only the weight?
>
>Increased drag and more limits in materials I think?

Yes maybe, however the drag may be far less than the increased efficiency or
better focusing with a smaller array.

We (also others than me and Kelly) should try to find some more pros and
cons about laser and maser.

Timothy