Project Orion, farming the solar system... and asteroid cities?

Imagine that you're an engineer who worked on America's nuclear weapons program. You'd like to look for a more constructive use for you work.
Why not turn the mind breaking energy of nuclear bombs to  making the kind of absurdly huge spaceships Galactic Empires favour a reality?

This kind of size. Although less pointy. Image courtesy of ComicVine

In the 1950's a bunch of the engineers, who worked on American nukes, developed project Orion. Orion was a plan for .... frankly, quite insanely huge.... spaceships. Spaceships propelled by, essentially, throwing nukes out the back one at a time and setting them off.

	"Satellite" Orion	"Midrange" Orion	"Super" Orion
Ship diameter	17–20 m	40 m	400 m
Ship mass	300 t	1000–2000 t	8,000,000 t
Number of bombs	540	1080	1080
Individual bomb mass	0.22 t	0.37–0.75 t	3000 t

Above: A table I've shamelessly cribbed from wikipedia, showing the sizes of three different classes of Orion space ship. Note the number of zeros - that's not a typo. You could carry a small town into space with one of these things.

And, as far as we can tell, it probably would have worked. Two things closed the project down: The nuclear test ban treaty, and one important piece of technology never happening - a fallout free nuke. Without that even starting these bad boys up in orbit would have increased cancers worldwide.
There're still people interested in the general idea today -  as I said, it's very possible it could have been made to work. The original engineers even built a miniature Orion that used high explosive instead of nukes:

For  bit more detail, here's the son of one of the engineers that worked on it:

What if it had worked? Well, one recent news story points in the possible direction that future might have taken: Vegetables have been grown on simulated Lunar and Martian soil. I did a bit of digging, and found a similar story about  plants grown on material from  C- class asteroids. Water is abundant in many parts of the solar system, so by the early 70's, humankind could have been expanding into a solar system where farming could happen..... could the kind of self sustaining space colonies envisioned by people like Gerard O'Neill have really happened?

Above: An artists impression of the inside of an O'Neill colony.

We'll never know for sure - our future seems to be heading in the direction of spacecraft miniaturisation- but it's now 2016.... I wonder where that alternative future would have gotten to by now.

Above: An artists impression of an Asteroid city, by JustV23

Elsewhere in the Universe:

Mercury's surface contains carbon

Asteroid arrives early

Dawn marks one year at Ceres.