Robber Barons in Space

Al Globus wrote:

>You should consider the possibility that, having done something once
>successfully, something may go wrong. That said, a solution proposed
>earlier of having many lasers and pointing systems, any one of which
>won't do any damage to a reflective surface, should work just fine.
>
>Somewhere I saw mention of an effect called 'blooming' which distorts
>the atmosphere in the neighborhood where the laser impacts the reaction
>mass. This was considered a serious problem but I don't understand it.
>
The air isn't perfectly transparent, so the laser thermally heats the
air; and then the air's refractive index changes (exactly the same
principle as you get with mirages) and so the light refracts and scatters.

It's probably actually worst near the lasers, because a tiny angle
distortion of the beam there means portions of your beam can miss the
vehicle entirely.

The issue can be improved by reducing the intensity of the laser; by
having a larger diameter primary lenses on the ground and by having
distributed lasers which are spaced apart so that the beams don't
intersect much.

You do get a similar effect at the vehicle end, however the air has less
time to heat because the vehicle is moving so blinking fast; so it is
'air cooled' whilst in the atmosphere; also whilst you're in the
atmosphere you're closer to the launch site so the distance is less and
accuracy is improved.

Heat exchanger vehicles are better off in this respect than lightcraft-
the heat exchanger may well be more than a meter across- it's just a
bigger target all around.

Still, that's the handwaving explanation, about why it isn't necessarily
a problem. But AFAIK it hasn't been fully analysed numerically; and it
interacts with the trajectory and laser siteing decisions.

> Anyone?
>
>On Wednesday, March 19, 2003, at 09:22 AM, Ed Minchau wrote:
>
>>--- In spacesettlers@yahoogroups.com, "ian.woollard"
>> wrote:
>>
>>
>>>Al Globus wrote:
>>>
>>>
>>>> Thus, the laser must track
>>>>the vehicle. This is certainly not impossible, but may present
>>>>
>>>>
>>very
>>
>>
>>>>tough practical challenges.
>>>>
>>>>
>>>>
>>>However it's almost certainly soluble. And any solution stays on
>>>
>>>
>>the
>>
>>
>>>ground, and is reusable.
>>>
>>>
>>>
>>Actually, consider it not only soluble but solved. Take a look at
>>the picture of the shuttle Columbia:
>>
>>&.src=gr&.dnm=from+Starfire+Optical+Range.jpg&.view=t&.done=http%
>>26.
>>
>>(or just go to the Photos section on the spacesettlers yahoogroup
>>website and click on the Columbia folder)
>>
>>The photo was not taken as part of an official experiment, just a
>>few guys on their time off who took a small unused telescope and
>>hooked it up to a computer.
>>
>>An image like this one has adequate resolution for pattern-
>>recognition software, and is a relatively easy computational task.
>>Hooking up a laser to the system is a simple copy of the process
>>which controls the telescope.
>>
>>ed
>>
>>
>>Your own Online Store Selling our Overstock.
>>~->
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>---------------------
>Space tourism could be our ticket to the stars. Save your pennies,
>suborbital flights for $100,000 may start in 2005! See
>http://www.spaceadventures.com/suborbital for details.
>
>Al Globus
>CSC at NASA Ames Research Center
>http://www.nas.nasa.gov/~globus/home.html
>
>Views expressed in this email are only my opinions and are not the
>position of any organization I'm familiar with.
>

--
-Ian

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