I have no real (non-software) engineering background, and I could probably design, within current technology, shelters and mechanisms sufficient to keep people

I have no real (non-software) engineering background, and I could probably design, within current technology, shelters and mechanisms sufficient to keep people alive on Mars indefinitely. The problem is, there is no way you could possibly get my contraptions to Mars. They'd be huge and extremely heavy. The easier it is to get stuff to Mars, the bigger and heavier it can be, and the easier it is to keep people alive.