To be honest, I find it kind of funny when the family say things like "he would have been so proud to do something he could never do in life". I, quite frankly, would not personally like to be shot into space in a capsule the size of a thermos.
And in other news...
Stephen Hawking went up in "G-Force One" - the aircraft used to reproduce the effect of weightlessness found in space. Two people helped him out of his wheelchair so he could float around for a while.
Aparently he hopes to one day do the real thing. So, Matt, I think that disolves your observation: "Missy Higgins singing her own songs is like Stephen Hawking being an astronaught".