Now, there is growing talk of setting up something analogous to a "hit squad" at NASA that impartially agrees what projects should be ended, when, and under what rules.

I think this system sounds backwards. Here is how I would design it:

All missions have a defined life-time with a specific pre-termination date. When a mission reaches its pre-termination date, it automatically goes into pre-termination status. This starts another timer (90 days or so?). If this timer runs out and nothing is done, then the project is canceled automatically.

OK, so far it looks pretty bloody. But here’s where it gets better:

Instead of a committee to wield an ax (which you no longer need because the ax falls on its own), you have an advocacy committee. All projects in pre-termination status are in this committee’s domain. It is their job to:

1) Publicize the projects’ status and possible fate.
2) Evaluate projects on their list to determine costs to keep them running.
3) Evaluate projects on their list for future science return.
4) Evaluate projects on their list for popularity with the public.
5) Find funds to continue the best projects, change their status back to active, and reset their pre-termination date.

This committee should have a small pool of funds allocated by NASA for this committee to rescue projects from. However the committee should not be limited to using only those funds. They should also be able – for specific projects - to:

1) Go to congress for special appropriations,
2) Go to corporations for special donations,
3) Go to interested scientists to see if they can shake any grant money or university money loose,
3) Go to “angels” who might be persuaded to write a big check,
4) Ask the public for donations to save the project.
5) Any other (legal) sources of cash they can think of.