Ok, I've got the solution. If this is designed as an extra voluntary tax, then it avoids all the problems of other groups attempting to glom onto the idea and turn the entire federal budget into a reactionary self-serving crap heap.
If you wish to spend $5.00 more in taxes for a chance at a future space flight or the ability to sell that opportunity after winning it on the open market, then you can.
Acronymically speaking, GMTA.