Help with calculating Delta v requirements for Hoffman Transfer

[superecnate]

I'm trying to calculate (by hand) how much delta v it would take for a ship to go from LEO (2,000 kilometers altitude) to a circular, polar 1500km orbit of Venus. I'm getting stuck calculating the delta v requirement for the hoffman transfer to Venus.

I'm using the delta v equation from this site (http://en.wikipedia.org/wiki/Hohmann_transfer_orbit), but when I use wolfram alpha(http://www.wolframalpha.com/input/?i=%28sqrt%281.327426776E20%2F%28108.21E6%29%29%29%28sqrt%28%282*%28149.60E6%29%29%2F%28257.81E6%29-1%29%29%2B%28sqrt%281.327426776E20%2F%28149.60E6%29%29%29%28sqrt%281-%282*%28108.26E6%29%29%2F%28257.81E6%29%29%29) to plug the values into the equation, I keep getting crazy numbers. (all my imputs are in km, btw)

Can someone help me?

Here are my inputs:

GM (Gravitational Parameter of Sol):1.327426776E20

R1 (Semi-major axis of Venus): 108.21E6km

R2 (Semi-major axis of Earth): 149.60E6km

(I've already tried the Vis-viva equation, and it gave me a similarly insane number. http://www.wolframalpha.com/input/?i=v%5E2%3D%281.327426776E20%29%28%282%2F149.60E6%29-%281%2F1.28905E8%29%29%2C+v%3E0)

[K^2]

Your units need to be consistent. If you are using the value for G = 6.67384x10^-11 N(m/kg)², then all your masses must be in kilograms, distances in meters, and velocities in meters per second.

Edit: In your case, G is absorbed into gravitational parameter, but it still sets units for the rest of the problem. Always check units. GM isn't just 1.327426776E20. It's 1.327426776E20 m³/s². So you can't use distances in km with that.

Edited September 15, 2013 by K^2