[ExI] SE and SPS development

[painlord2k at libero.it]

Il 20/03/2009 20.11, Keith Henson ha scritto:
> On Fri, Mar 20, 2009 at 11:39 AM, painlord2k at libero.it
> <painlord2k at libero.it>  wrote:
>
> snip
>
>> There is no need of a 4 GW laser cannon to put in orbit a SPS system.
>> You only need a Few launch of large missiles in LEO with the stuff needed to
>> build a Space Elevator.
>
> You are seriously misinformed.

Having translatyed in full the english SE page of the wikipedia in 
italian, maybe not.


>  You have to be at GEO to build an
> elevator.  Also we don't have the material for it and my never get it.

I never wrote that the SE must be positioned in LEO, only that the stuff 
needed can be put in LEO first.
I omitted to write that it can be then assembled there and moved to GEO 
with a tug. A simple, cheaper tug with a ion engine could move it in 
GEO. It is not a thing we need to do in a hurry.

In this way the cost to put the SE in GEO would be reduced a bit.
And the technology for a tug in space is worth pursuing.

> It takes 15kWh/kg.  100 t, 100,000kg x 15kWh/h is 1.5 GW.  So a moving
> cable space elevator would need a 1.5 GW motor to power it.

Who ever talked about a moving cable SE?

> The
> electrical in to potential energy gained is about 10% for climbers so
> you would need a laser with a 15 GW input for climbers.  Climbers make
> no sense because you can lift as much with half as much ablation
> propulsion lasers.

The difference is that, if you have a large industrial base working in 
GEO (that I suppose we all want) you need to run stuff up and down, not 
only up or not only down.
I could be wrong, but using flyweels we could have climbers extracting 
energy when going down and expending energy when going up. Given there 
is too much energy to be stored in a single full travel, climbers could 
exchange the cargo or the flywheels at a middle point and reuse the 
energy stored climbing  or recharging the energy spent braking.


> This is the one use that megawatt scale lasers have.  And that's
> marginal.  You really need them in the tens of MW.

Deorbiting trash could be a service in need, if all the crying I hear in 
the last years is to be believed.

You don't need a single 100 MW laser to do the job.
100 x 1 MW laser aimed a different points of the veicle can do the same 
as a single 100 MW laser.

http://nextbigfuture.com/2007/05/lasers-and-magnetic-launch-for-cheap.html
http://nextbigfuture.com/2009/01/laser-array-space-launch.html
http://www.jkare.com/VG_HX_4-29-SAS.pdf


All the technologues are worth pursuing, because thay are good for 
different uses.
A SE is good to move large cargo continuously, up ad down. Mainly 
unmanned cargo from/to GEO. When you have the first up, the cost to 
build others will reduce so much that near any large  corporation and 
government will want one and will be able to build it.

Laser lauch, missiles and so on are good for fast delivery of small 
cargo (and humans).

Ion engines, light sails and other systems are good for travel between 
planets and more.

ORION is good to put in space a very large object. Something too large 
to be put in orbit using the biggest SE available. But, I wonder, what 
is too large to be put in orbit that can not be buil there if we send 
the materials needed or produce them there?

ORION, IMHO, don't have economics sense, like the large clipper planes 
at the end of the WW2.

> I have a relative who was downwind of one of the underground shots
> that failed to stay contained.  Chances are fair they will die from
> the effects.

That the last U.S. underground test happened in 1992 and the last with 
failed containment was in the 1986 (1985–86 Charioteer 18 Nevada Test 
Site). I would suppose that the effects are not so bad, if they are 
alive 23 years after the exposition. I would add that, now, we have drug 
that, taken before, can reduce the damage of radiations, just in case.

Mirco