When President George W. Bush unveiled his plan for a new moon shot two years ago, a lot of people worried that it was long on rhetoric and short on cash--ultimately forcing NASA to raid its science budget to pay for it. On close examination, though, the trajectory seemed reasonable. The money freed up by phasing out the space shuttle and the International Space Station was not an implausible amount to build a postshuttle spacecraft (known as the Crew Exploration Vehicle, or CEV) and send it moonward by 2020. A "go as you can pay" strategy would extend the deadlines if money got tight, rather than pickpocketing other programs. A modest dollop of extra funds would help cover the transitional costs. NASA administrator Michael Griffin said at a press conference last September: "In our forward planning, we do not take one thin dime out of the science program in order to execute this architecture."

Now it looks like the skeptics were right. The NASA budget announced in February mows down a scarily long list of science missions, from a Europa orbiter to a space-based gravitational-wave observatory. Research grants to individual scientists, traditionally kept safe from high-level budget machinations, have taken a 15 percent hit, retroactive to last fall; hundreds have already received "termination letters" canceling their projects. Griffin went before Congress in February as the bearer of bad news: "Fulfilling our commitments on the International Space Station and bringing the Crew Exploration Vehicle online in a timely manner, not later than 2014 and possibly much sooner, is a higher priority than these science missions during this period."

The countdown to the crisis actually began a year ago, when the Bush administration lopped off the dollop of bridging funds it had promised. Then came Hurricane Katrina, which damaged shuttle facilities in Mississippi and Louisiana, and an acrossthe- board federal budget cut, largely to raise money for the Iraq War. Worst of all, a new analysis of the shuttle and space station found them at least $2 billion in the hole. Griffin went cap in hand to the administration but was told to make up the difference from the agency's own wherewithal.

Compared with the plan of two years ago, science gives up a total of $6.4 billion (in 2005 dollars) over the five years from 2007 through 2011--a 20 percent cut. Planetary exploration is the worsthit area--40 percent. Human spaceflight gains $5.2 billion, but its situation is hardly to be envied either. The shuttle fleet will make 16 rather than 28 trips to the space station before retiring in 2010, and from then until the CEV debuts, the country will have no capability to launch astronauts into orbit at all.

Griffin has described the shift of money as a "speed bump," a temporary measure to get human spaceflight back on course. Veteran observ- ers express sympathy for his dilemma. "It's a knotty problem," says John M. Logsdon, director of the Space Policy Institute at George Washington University. "There's no clear answer."

Nevertheless, many complain that he has been heavy-handed. Multiyear projects require some consistency in their funding. By making such an abrupt budget change, NASA will mothball or abandon half-built (in some cases, fully built) hardware, lose expertise developed at great effort, and leave gaps in data coverage, notably of the earth's climate. NASA has had budget crunches before, but seldom have they been so wasteful.

"It's the sudden change in slope: thats why this is more difficult than it was in previous years," says Lennard Fisk, chair of the National Research Council's Space Studies Board and himself a former NASA official. The unprecedented targeting of research grants strikes scientists as particularly gratuitous: for a small savings, only about $80 million, NASA is causing a huge disruption.

The Space Studies Board is investigating how to hold on to the grants and smaller missions by delaying or downgrading the bigger fry. Several flagship missions, such as the James Webb Space Telescope, have run over budget and need housecleaning anyway. Wesley Huntress, director of the Geophysical Laboratory of the Carnegie Institution of Washington and another past NASA official, says scientists need to take responsibility for making the necessary trade-offs, rather than leaving it up to NASA headquarters and Capitol Hill.

Some hope the crisis may finally force some out-of-the-capsule thinking. Should NASA jettison the shuttle and station right away? Should it do the opposite and stretch out the station's construction to reduce its annual cost? Should NASA be split into separate science and astronautics agencies? If it were, would that really be good for science? Unless some helpful reform can be salvaged from the situation, what seemed like such a grand vision two years ago may fail in the execution.