The Superconducting Super Collider: what went wrong? The Superconducting Super Collider was famously cancelled in 1993 after running enormously over budget.  According to the wikipedia page:

During the design and the first construction stage, a heated debate ensued about the high cost of the project. In 1987, Congress was told the project could be completed for $4.4 billion, and it gained the enthusiastic support of Speaker Jim Wright of nearby Fort Worth. By 1993, the cost projection exceeded 12 billion dollars. ...

What went wrong? Why was it so much over budget?
How can such a fate be avoided by future big physics projects in the US?  What did we learn?
 A: Several things went wrong. I was not part of the community until very late in the process, but my older colleagues report the following:


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*Project budget estimates are generally low-balled at some level.

*It was "designed" (perhaps "spec'ed out" would be better) on the assumption that a break-through in super-conducting magnet design could be scheduled and made to happen by throwing money at it. This did not work out as well as they had hoped, so more and more money was thrown at the problem because the magnets were critical infrastructure. Of course, the LHC has benefited from the results.

*The project budget was necessarily put into the hands of a few physicist-managers. All senior people who had run successful "large" projects in the past. But there is a difference between "large" and LARGE. The total SSC budget was roughly ten times what they had handled in the past, and the procedures and heuristics they used we're not really good enough. Money was mis-spent. DOE has implemented a more strenuous oversight processes since then: lots of "critical decisions" to be met before you get the big bucks.

*Even the parts of the project that weren't assuming a break-through suffered the usual budget creep.

*A certain amount of effort went into selling it as a potential job creator to the legislators representing several potential sites. Once they settled on one, the losers obviously lost interest.
References:


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*"Scientists Are Long Gone, But Bitter Memories Remain"  (in Science magazine, behind pay wall).  Like the title says; discusses the fate of the facility 10 years after cancellation.  No discussion of why it was cancelled.

A: There are two points of view. Because of cost overuns and fiscal issues, it was deemed too expensive to complete. The other side of the coin was that the administration didn't sufficiently value America's leadership in particle physics. 
A: The politics, not the cost overruns themselves, killed it:  If the cost killed it then it would have been a bureaucratic move.  What happened was that Congress publicly selected and sacrificed the SSC.
I was young, but the political story I recall has a few other elements: Congress wanted headlines about cutting spending (but did not want to really tackle controlling the budget).  The delegation from Texas was politically weak at this juncture (otherwise they could have defended the local SSC project).  All in all, many elected officials get more popular from cutting science spending than increasing science spending -- and the SSC was the largest undefended item. 
This year (2011) the House is loudly cutting spending on public TV and public radio and other nickel-and-dime things to generate headlines (but does not want to really tackle controlling the budget).  They spent the last few years mocking various science projects (e.g. mocking "volcano research" right before a big eruption...).
