[AR] Re: 500,000 tons

  • From: Neil Jaschinski <neil.jaschinski@xxxxxx>
  • To: arocket@xxxxxxxxxxxxx
  • Date: Tue, 08 Apr 2014 10:40:00 +0200

Hello,

I was not able to follow the hole discussion. So maybe some points from
my side are already discussed.

1. In the main article the effective power output of a space based solar
power plant was 10 times higher compared to a ground based. If I take
the solar constant with 1,361 kW/m²
(http://en.wikipedia.org/wiki/Solar_constant) and compare this with a
map of sun radiation
(http://www.nrel.gov/gis/images/map_pv_national_hi-res.jpg) for e.g.
USA, than I don't get ten times more.

2. If a ground based solar plant is not as good as a space based, it
still can be better if you build it bigger. It is not as big as you
would think
(http://www.inhabitat.com/wp-content/uploads/sahara-solar-map2.jpg).
since it is ground based, normal technology can be used and normal
transportation can be used. You don't need energy transmitter and
receiver. If you make the power output of the power plant as some kind
of similar to oil, than you can use the same infrastructure to transport
it on the ground. We don't need to change our hole energy system. If you
use a space based power plant, than we have to change everything to
electricity. This has to be taken into account if you want to calculate
the overall cost.

3. If you still want to build a space based power plant, why not
building the parts on the moon and launch them from there? Moon has no
atmosphere and you can use magnetic rail guns to bring it into orbit.

4. Also this laser driven engine would work better based on the moon
because no atmosphere would disturb. The laser should only used in that
way, that if the laser don't hit the target, that the laser will not hit
the earth. From the image of the main article, it looks like that when
the laser don't hit the target, it will just hit something on the
ground. I think this is not a good solution ;-)

5. What is the success rate of launching 500,000t into orbit? Actual
system are close to 100%. But if you are using mass production, you may
change the success rate to a lower value.

6. What is the life time of a space based power plant compared to a
ground based? How much would the yearly service cost? Solar thermal
power plants are more low technology style compared to space based. So
you can use normal equipment and trained people to do the job. For space
based power plants, it is totally different. You need a huge amount of
astronauts with better training etc.

7. What happens if a space based power plant get out of control? I mean
it has to be placed in position constantly over the hole life time. A
ground based power plant just stays there where it was build.

I think ground based solar power plants can work better. We do it in
Germany already. Some days of the year, we can run completely on solar
power and we don't have covered all the roofs and parking places or
roads yet. The main problem is to safe energy for the days without
enough sunlight. but this problem still sounds easier to solve than
putting 500,000t into into orbit ;-)

So, I would scale down the question to some thousand tones for
interplanetary space ships to colonies other planets.

Greetings

Neil

Am 08.04.2014 09:55, schrieb Keith Henson:
> On Mon, Apr 7, 2014 at 11:28 PM, David Weinshenker <daze39@xxxxxxxxxxxxx> 
> wrote:
> 
> snip
>>
>> What I think is loony is the assumption of starting at such a large
>> scale... it takes time to accelerate the industrial capacity to -build-
>> 500,000 tons/year of new "stuff"... what is the current "M-dot" of the
>> present US (or global) heavy manufacturing capacity? What are historical
>> examples of ramp rates? (e.g., the US industrial activity of World War 2?)
> 
> That's an *excellent* question.
> 
> The second stage has to fit within the Skylon cargo bay.  It holds
> about 10 tons of hydrogen, which takes up most of the space.  Second
> stages reach GEO at a rate of 72 per day.  That requires manufacturing
> them at a rate of three per hour, a rate that takes several
> Panamax-class container ships to deliver about 25,000 of them from
> manufacturing plants to the launch site every year.
> 
> This shipping requirement is simply the consequence of building 100 GW
> of power sats with a mass around 500,000 tons per year, and not using
> dedicated transport tugs from LEO to GEO.  Do the numbers make any
> sense?  That is, do we have any experience manufacturing aerospace
> objects at this rate?  Do we have any related industrial experience?
> The answer is "maybe" on both questions.
> 
> A B-17 is about the same mass (29,600 kg vs. 30,000 kg) with
> equivalent empty and full mass as the proposed second stage.
> 
> "At the peak of production, Boeing was rolling out as many as 363
> B-17s a month, averaging between 14 and 16 Forts a day, the most
> incredible production rate for large aircraft in aviation
> history."[al1]
> 
> A B-17 is far more complicated than the second stage should be.
> Boeing produced B-17s in the 1940s at 20% of the second stage
> production rate.
> 
> Typical production lines operate at 10-30 units per hour.  Run one
> shift, five days a week, the production rate would be 12.6 per hour,
> about one every 5 minutes.  The empty mass would be around 10 tons.
> The payload (except for fresh food) would probably be preloaded at the
> factory, requiring only fueling.  Fueling through the Skylon would
> simplify flight operations, though it does present leak hazards.
> 
> I don't know the m-dot of current industry, but it's big.  The US has
> lost more than half of it's automobile market, but for decades it
> produced 10-15 million cars a year.  Most of them were a couple of
> tons, making the car production alone 20-30 times the proposed initial
> power satellite construction rate.  I worked for a while at the EMD
> plant.  A few years before I was there they cranked out over a
> thousand locomotives in a year. At 160 metric tons each, that one
> factory produced 160,000 tons of product, and it may have been higher.
> 
>> It seems like overly ambitious expectations - and the attendant tendencies
>> to burn money too fast in the wrong places (and to view realistic outcomes
>> as project-invalidating "failures") tend to be a pretty strong risk factor
>> for "hard-starting" what could have been feasible industrial undertakings!
> 
> If you have specific idea of how to apply this to the power satellite
> project, I would be very interested.
> 
>> Also, does a power satellite need to be at geosync?
> 
> They do.  Anything else is just a nightmare of complications.  Close
> in, unless you are using sunsync, the earth eclipses them too much of
> the time.
> 
>> Seems like a given
>> transmitter could deliver better power density at the surface from a
>> lower orbital altitude... and it's probably going to want active beam
>> aiming in any case (which is one of those things that -can- be "done
>> without moving parts, in Software" anymore - i.e., with things like
>> phased-array techniques)... so why not just have a constellation
>> of the things spinning overhead at low altitude, each scanning its
>> beam angle to maintain targeting as it passes over each antenna farm
>> (and then switching to illuminate the next one as it came in range).
> 
> This means that one of them being out of service give the utilities a
> problem of huge blocks of power going in and out of service.  Plus you
> can't turn it on till you have a bunch of them.  It's just too
> complicated.  At least it is for me.  Royce Jones promotes this
> variation.
> 
>> My thought would be actual geosync would be undesirable (due to conflict
>> with exactly-positioned communications craft);
> 
> The communication satellites would be bolted on to power satellite
> that would supply power and station keeping.  The comm sat guys like
> the idea.
> 
>>  it might be better to use
>> an orbit that's high enough to avoid the ISS and the air, and low enough
>> not to get too much Van Allen exposure...
> 
> Thanks for the comments.
> 
> Keith
> 
>> -dave w
>>
> 
>

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