Rocket science is hard. This isn't some comic book where science is easy.

Rockets are fine for crude fireworks, or anything that needs a quick, short push, but not as a controlled source of power. We don't have the right fuels, or the guidance systems. It might take a hundred years to invent everything. We just don't have that time!

Should we instead create a giant gun to fire things at Mars? Or should we use captured Martian technology? Or do something else?