[ExI] Engineering

[Keith Henson]

On Mon, Dec 17, 2012 at 4:00 AM,  Adrian Tymes <atymes at gmail.com> wrote:

> On Sun, Dec 16, 2012 at 7:14 AM, Keith Henson <hkeithhenson at gmail.com> wrote:
>> On Sun, Dec 16, 2012 at 4:00 AM,  Adrian Tymes <atymes at gmail.com>> wrote:
>>> I meant, test the specific beam tracking & focusing mechanism
>>> the large sat would use.  Comm sats don't try to focus their
>>> output on one particular point.
>>
>> Some do control where the beam power comes down.  Ever seen one where
>> the microwave feeder out in front of a parabolic reflector is a mirror
>> image of the US?  They switch the power around to get higher bandwidth
>> to particular spots on the ground.  Big spots to be sure because of
>> the relatively small optics.
>
> Right, but do *you* have the specific blueprints that they used?

> Could you bend metal to put that particular thing together?

Why put the burden on me?  Do you know how to refine and shape the
aluminum in your soda can?  Phase array radar antennas exist in the
size of football fields.

> Just because it's been done - even if it's been done many times -
> does not, by itself, mean that all further ventures will be able to
> do it.  Yes, this is wasteful duplication of effort from certain
> perspectives, but that is how engineering projects proceed.

The problem with power satellites is *not* collecting power in space
or beaming it to the ground.

The problem is the uneconomically high cost to lift the parts to GEO.
It's about a hundred times too expensive for power satellites to make
economic sense.  That's the urgent problem.

And for fundamental physics reasons you can't start small.

Keith

PS.  One of the reasons the power density is so low is that the
original investigators were not sure of non linear interaction of
microwaves with the ionosphere.  The set the power limit low to be
sure problems would not arise.  Full size and full power testing is
the only way to be completely sure this will work.  To do that, you
have to build a power satellite.  And given the cost to lift parts to
space, it's cheaper to set up the parts pipeline for hundreds of them
than it is to build just one.