stuck.. astronomy question: sending probe to venus?

A

asteroidvsmars

New member
want to send a probe to Venus (a =0.72 AU) from Earth the most economical way possible. What is the semi-major axis of the probe’s orbit and eccentricity? How long does the trip to Venus take? In which direction do you launch from Earth (towards the direction of Earth’s motion, or away from it and why).

So I got the semi-major axis to be 0.36 AU, but whenever I try to solve for e, I keep getting a number higher than 1, and we all know that eccentricity is measured between 0-1. Any help?
 
you want a hohmann transfer orbit.

that would be an orbit where the probe would initially have an aphelion of 1AU (fromt he Earth) and a perihelion of 0.72 AU. The semi-major axis, then, would actually be 1.72/2 or 0.86 AU (not the figure you came up with, although you might have just made a typo).

keplers third law will give you the period, but remember to divide by two when you are done, because you only need a half an orbit.

i would imagine you would want to launch away from the direction the earth is orbiting, given the "fuel efficency" part

i do not recall the formula for calculating eccentricity
 
you want a hohmann transfer orbit.

that would be an orbit where the probe would initially have an aphelion of 1AU (fromt he Earth) and a perihelion of 0.72 AU. The semi-major axis, then, would actually be 1.72/2 or 0.86 AU (not the figure you came up with, although you might have just made a typo).

keplers third law will give you the period, but remember to divide by two when you are done, because you only need a half an orbit.

i would imagine you would want to launch away from the direction the earth is orbiting, given the "fuel efficency" part

i do not recall the formula for calculating eccentricity
 
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