Re: Practical space travel and unlimited growth

Additional analysis and targets


Assuming we tap the inner solar system - Ceres orbits 2.8 AU from the
sun, that's 420 million km radius.

Earth is 1.0 AU - 150 million km from the sun.

So, the distance ranges to the most distant point in the inner solar
system - from 570 million km to 270 million km.

Now, at a constant gee force - to transport 285 million km in 20 days
- half the larger distance in half the 40 day trip time - requires

d = 1/2 a t^2

where d= 2.85e+11 meters
t= 1.728e+6 seconds

so

a = 2*d / t^2 = 2* 2.85e+11 / (1.728e+6)^2
=0.1908 m/s/s

19.4 milligees.

v = a * t = 0.1908 * 1.728e+6 = 329,702.4 m/sec


With an exhaust speed of 1,000 km/sec - 1,000,000 m/sec - 100,000
seconds Isp - requires a propellant fraction of about 28.1% for each
stage of the mission.

So, to speed up and slow down requires 48.3% across this 570 million
km distance in 40 days - equalling the performance in time of the
large shipping vessels that ply the Earth's oceans today- throughout
the inner solar system.

Smaller distances, in the same time periods require less energy and
performance.

With a payload of 350,000 tons, this requires approximately 169,000
tons of propellant energized by 84.5e+18 joules of energy to attain
the exhaust speed needed.

This is an average power level of 24.4 trillion watts.

Which requires 7 sq km of solar collector at 3 million km above the
sun to generate.

Allowing a cost of $7 per ton payload as the energy cost of transport
- that's 34.4 trillion joules per dollar. Another $3 per ton for
all other costs.

That's equivalent to 5,654 barrels of oil per dollar.

The 7 sq km of sun orbiting solar collector generates $0.71 per
second, $2,553 per hour, and $22.38 million per year. Using typical
discount rates and longevity terms, we obtain $50 million to $100
million CAPEX per sq km of solar collector to achieve these cost
figures. This is $50 to $100 per sq meter.

Allowing $2 per ton for the CAPEX of the ship, and allowing 6 trips
per year - that's 360,000 tons x 6 x 2 = $4.32 million per year.
This is about $90 million per vehicle using typical longevity and
discount rates. Allowing 5% structure to payload fraction - the
empty vehicle is 18,000 tons - $5 per kilogram - $5,000 per metric
ton. This is low by today's standards when compared to other
aerospace costs - high compared to construction costs of large
shipping vessels.

$1 per ton for the operator costs - this assumes 20 persons per
vehicle - and with $2.16 million per year - $108,000 per year average.

Profits appear at ROI or discount rate for invested capital.
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