Alan Stern, the former head of NASA science, has published two opinion pieces today:
New York Times (check out the reader's comments): http://www.nytimes.com/2008/11/24/opinion/24stern.html?_r=1&ref=opinion
Space Review: http://www.thespacereview.com/article/1258/1
Space Politics has a summary and some interesting comments by readers:
The Space Review piece calls for a new NASA mission and/or focus to reconnect the agency to today's needs. Stern diagnoses the problem, throws out some high level directions, but doesn't make a strong case for any particular mission.
The New York Times piece calls for NASA to prevent its big, technologically challenging missions from consuming its budget.
My take: NASA is an agency defined by a technological province applied to three distinct missions: keep Americans in space through a manned program, carry out innovative science missions, and design and operate several operational programs related to Earth observation. The unifying theme to NASA, in my opinion, is developing innovative technical solutions, and not a particular service. Therefore, NASA's mission at any particular point in time is defined by those projects that push technical innovation. (I'm ignoring the fairly small portion of the portfolio where NASA applies well understood technical solutions to specific -- and usually smaller -- missions.) For NASA to kill one of the large missions is to kill a portion of is current purpose.
NASA does not need to operate this way. It could have the focus on delivering specific benefits in the most cost effective way with manageable risks. The recently approved lunar GRAIL mission is a great example of this approach. Incrementalism does have its drawbacks: it results in publically less exciting projects (few members of the public will be engaged by GRAIL even though the science is excellent), and it is harder to engage Congress in approving large budgets.
Personally, I believe that this is not an either or proposition. A NASA that cannot fly missions because its budget is eaten by a few missions is not successful. On the other hand, a NASA that never takes the bold steps (and risks) is not the space agency I want.
My prescription for NASA's science program would have several parts:
(1) Emphasize Earth observation. We know our planet's climate is changing. We know that human use of the biota is causing fundamental changes. The public gets it. A space agency with this as a central theme (instead of one goal within its science directorate) would be seen a very relevant.
(2) Define an operational science program whose goal is to apply well proven technology to scientific questions. This is the meat and potatoes of the program for scientific exploration of the Earth and space.
(3) Have a portion of the budget for big missions that employ new science. Recognize from the start that these missions carry with them the risk of cost overruns and technical problems. Do not approve them until significant work has been done to define the solution and develop the technology (in NASA speak, carry them through Phase B study before approval). Make this a level of effort program -- fund this at a constant level and when cost overruns occur, let the schedule slip. Do not rob other programs try to hold the missions in this program on schedule.