Solar-powered space flight
3e. Power required to reach earth orbit
ignoring atmospheric drag: Corresponding figures for various other bodies in
the solar system
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3.11 The Earth is
the largest of the inner planets and therefore the most challenging in terms of
the required 
to reach orbit. Even
though Mars is circa 1.524 times as far away from the sun as the Earth, its smaller
size and therefore lower surface gravity and orbital velocity more than
compensate for the smaller amount of solar power available per unit area in its
vicinity, see Figure 5. The same also appears to be true for all but the
largest moons of Jupiter and Saturn even though they are considerably further
away from the sun.
Figure 5. Values of 
(for different
propellant to lifted mass ratios), assuming vehicle travels horizontally and
with propellant ejected at optimal speeds (subject to an upper limit of 10,000
ms-1) and optimal angles, for the Earth, Moon and Mars
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