Try not to use Evaluate. It isn't needed.
So the input to your plotting function is:
{(r[t]*Cos[o[t]] /. TotalThrust), (r[t]*Sin[o[t]] /. TotalThrust)}
Evaluate this and look at the result. It's a list of lists. That is
r[t]*Cos[o[t]] /. TotalThrust
produces a list. Lists are those curly brackets. To get rid of them use
r[t]*Cos[o[t]] /. TotalThrust[[1]]
as shown in the article linked in the previous post.
ParametricPlot[{(r[t]*Cos[o[t]] /. TotalThrust[[1]]), (r[t]*Sin[o[t]] /. TotalThrust[[1]])}, {t, 0, 10}]