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(Wolfgang Hohmann, 1925). A spaceship must first get free of Earth (it still orbits the Sun

together with Earth, at 30 km/s, at a distance of 1 AU), then it adds speed so that its aphelion

(in its orbit around the Sun) just grazes the orbit of Mars, A = 1.524 AU (ignoring ellipticity).

(a) Draw the orbits of Earth and Mars, together with the Hohmann Transfer Orbit.

(b) What are the minimum and maximum separation from the Sun? What is the semi-major

axis of this orbit?

(c) Using the Newtonian derivation of Kepler's 3rd law once again, determine the orbital

period, and hence the time taken to reach Mars from Earth. Express your answer in

months.