BobfromSydney wrote:Two points:
SNIP
What really amazes me is Grayson. Their prewar workforce participation rate would have been around 15% of total population (25% are male, minus those who are too young or too old to work). Even accounting for the effect of women in homemaking, child raising (and education?) and possibly agriculture (working the family farm?) this is still a very small percentage when you consider the problems imposed by planetary conditions.
Even if you assume that one orbital farm would support 10,000 people, assuming 2/3rds of the food came from orbit and a population of 3 billion, that would require 200,000 orbital farms. I imagine something like that would show up in the night sky (or even daytime sky?) as a BELT.
Now there was even some mention of cattle in orbital farms. I imagine that those cattle would only be available to the extremely rich. This is because of the inefficiencies of raising cattle compared to the equivalent crop yield you could achieve using the same amount of 'land'.
source:
http://www.farmlandlp.com/2012/01/one-a ... -a-person/
Now assuming that year-round growing season and 24-hour sunlight both increase agricultural productivity twofold, this means that the space farm needs about 2500 acres of surface area (growing area) which is pressurised and sunlit (or lit with UV lamps internally such as a hydroponic system).
Plugging this back into the figures above this means that a population segment of 15,000 people (which may have around 2,250 working males - don't forget the low life expectancy) needs to support not only the regular planet-side economy but also a space farm of 2,500 acres growing surface AND the space transport to bring purified raw inputs up (water, air, fertilisers etc.) and food produce down.
Now you can scale the size of the orbital farms up and down if you wish, but the amount of surface area required still varies linearly with population.
Maybe this is doable, but now that I've run through the numbers this does stretch my suspension of disbelief. It certainly would not be possible at all without counter-grav technology.
But if the Graysons were able to keep this house of cards up before the Alliance then I imagine they could certainly build a modern space fleet in a couple of decades once they weren't working with both hands tied behind their backs. Don't forget a good number of their SD hulls were sold to them at scrap prices by the Highridge government.
First, your labor force numbers are low. If you've been reading the short fiction and reading between the lines of the novels, you should have realized that the number of women officially in the work force even before the Manties came along was significantly lower than the number actually in the work force.
Second, I never said the orbital farms fed the entire planetary population. I said that they were more efficient in terms of production, that operating costs were far lower than for planetary farms (because there was no need to continually fight soil contamination), and that food from them was much safer (because there was no need to continually fight soil contamination). The majority of food production, by a very large margin, continued to be produced on the planetary surface. And, BTW, most of the cattle on the orbital farms were for dairy products, not meat. Orbital farm produced milk was indeed much more expensive than planetary produced milk, but it was also heavily subsidized in most steadings for the consumption of children.
Third, they had counter-grav technology by the time they started thinking about orbital farms as a food source for anything other than their space-based industrial and population habitats. Their CG wasn't as efficient as the tech later available to them courtesy of Manticore, but it certainly existed, or else they would have required grav-spin habitats aboard their warships, which they did not.
Fourth, the orbital farms were a relatively recent development, a desperate way to increase arable land (and so allow for a larger population) before Skydomes came along and made it possible to build planetary farms --- which suddenly became more efficient in terms of both production and operating expense than the orbital farms had been.
Once Grayson acquired access to modern Manty technology, especially in terms of industrial infrastructure, productivity per manhour went through the roof . . . literally. With additional women added to the open workforce, out of the sort of "gray" workforce in which they had labored without recognition, and productivity per manhour making a shift probably comparable to that seen on Earth between about 1880 and the year 2000 for the entire planetary population, rather than just the first world, the degree to which Grayson's economy expanded becomes, I think, quite understandable.
Of course, I'm only the guy who built the place, so I could be wrong, I suppose . . .
