THE United States asks NASA to do an extraordinary amount with very little money. Explore Mars, document climate change, stop doomsday asteroids, find life on Europa — all for less than one-half of 1 percent of the federal budget. But budget uncertainties on Capitol Hill, including delays in federal appropriations legislation and temporary government shutdowns, measurably harm the American space program. Even the threat of a shutdown can have a far-reaching impact on scientific projects, often in unexpected ways.

“I keep a standing Google News alert for ‘NASA Budget,’ ‘Federal Budget’ and ‘Government Shutdown,’ ” says Dante Lauretta, the principal investigator of NASA’s Osiris-REx mission, in which a spacecraft will fly to an asteroid, study it, grab a piece of it, and then fly back to Earth. Osiris-REx is set to launch next year, but the federal shutdown in 2013 caused a major schedule slip in the development of a key instrument on the spacecraft, costing taxpayers $1.7 million.

According to Eric Smith, the program director of the James Webb Space Telescope, NASA programs develop contingency plans for how hardware can be placed into a safe configuration should, for example, the order for a shutdown be given. It was a hard-learned lesson. “In 2013,” he said, “some of our science instruments, including ones from our foreign partners, were in a cryogenic vacuum when the shutdown order came. We were permitted to keep the hardware safe in a cold vacuum state, but could not continue testing.” As a result, the program was able to make up for it, but at a cost.

Such delays are not trivial events at NASA; everything there is tested, first in isolation and then in aggregate, each part having to prove itself to engineering specifications before being added to a larger rocket or spacecraft, where more tests are conducted to make sure everything works well together. NASA flourishes when it is given a clear goal and the long term support to make it happen. Erratic funding streams add an unstable element to a process where instability means the loss of irreplaceable hardware and the interruption of research.