In TML Nightly V47#2, [email removed] writes:
>This got me thinking about what a large volume of refuelling vessels
>would do to a planetary environment. Has anyone done any investigation
>of the amount of Hydrogen fuel taken from a high tech high population
>starport class A world in one year? Is this a significant effect on
>the planetary ecology? How about over a 10 or 50 or 100 year period?
>When would this become a problem and force all refuelling to happen
>offworld at gas giants etc?
Let's run some simple calculations here.
Assume a million (1e6) ships per year, and that each takes a million
tons of LH2. This is likely to exceed the traffic at *any* planet by a
good margin.
So we have 1e6 x 1e6 = 1e12 tons of hydrogen leaving annually. Water is
H2O. By weight it's 1/9th hydrogen, 8/9ths oxygen. So that means we need
9e12 tons of water to supply that hydrogen. 9e12 tons is 9e18 grams. One
gram of water occupies one cubic centimeter. So that's 9e18 cm^3 or 9e12
m^3 or 9e3 km^3. (a cube a mere 20 km on a side)
We'll asssume that this is an average (size 7) planet, with an average
hydro %age (70%). Much like earth. So the surface area of the planet is
4pi r^2 km. That's 6e8 km^2. Times 70% is 4e8 km^2.
Divide the volume of water by the surface area of the oceans, and you
get 2e-5 km or 2e-2 m or 2 cm.
So with that *huge* outflow, we've managed to lower the oceans by a
whole 2 centimeters.
(somebody please check my calculations. I'm surprised we got that much
of a drop!)