Work done propelling objects into orbit. I am currently working on a few problems but as of now I am stuck and unsure what to do. My confusion isn't in the mathematical computations but in the question itself. My question that I am working on is comparing the work done by propelling a single object into orbit of all 8 planets. Obviously I can look up the orbiting altitude for earth but other planets start to confuse me. I decided to use Newton's law of Universal Gravitation to find the variable d (distance between the planet and the object) but I always get a huge unreasonable number. Is there another way I can estimate the work done by launching one object into orbit around the planets? As of now I would find a function for the change in work and integrate from the planets radius to the distance I got from Newton's law of Universal Gravitation. Please help me someone.
Okay so for clarification here is one of my answers that I arrived to. This is for Venus. 
$$F(x)=\frac C {x^2}$$  where C is the Constant of proportionality.
then when using the weight of the module being launched 380552.711 and the radius of Venus 6,051,000 m I get 
$$380552.711=\frac C {6051000^2}$$
and $$C= 13,933,785,672,733,311,000$$
now we have the 
$$\Delta W= \frac{13,933,785,672,733,311,000}{x^2}\Delta x$$
Now is the time that I would solve for the distance between the satellite and the planet. I solve for d from Newton's law of Universal Gravitation (which I suspect is the wrong thing to do and I get the distance to be $1.89218 \times 10^7$.
I use the radius of Venus as the lower bound of integration and the distance I just solved for plus the radius of venus for my upper bound. Once I solve for work by integrating the change in work function I got I get the work done to be $1.711\times 10^{13}$ joules. 

At the burnout $(t=0)$, the free flight is decided by the initial conditions $\mathbf r_0=\mathbf r (0)$ and $\mathbf v_0=\mathbf v (0)$.
The point is that the orbit is elliptic (right-hand inequality) and the satellite does not hit the surface of the planet (left-hand inequality) if $$\sqrt {\frac {GM}{r_0}} \le
 v_0 < \sqrt {\frac {2GM}{r_0}} \quad \quad (r_0>R)$$ A special altitude does not exist because the condition contains both $r_0$ and $v_0 \,$.
Moreover note that the condition contains only the initial speed (not the initial velocity).
