The money saved by retiring the shuttles was supposed to have been channeled into a renewed mission to the moon. Funding for that was cut in 2010, however, leaving U.S. manned spaceflight (beyond the International Space Station's orbit) in limbo.
Could the private sector pick up the slack? What would its motivation be? Even if an extraordinary wealth of minerals were found within reach of terrestrial vessels, it would have to be excavated and transported back to Earth. Given the colossal expense of manned spaceflight and the relative ease of earthly mining, the prospects for moneymaking missions of this sort are scant.
True, private space tourism is expected to expand. Note, though, that it's expected to involve short excursions, only dozens of miles above Earth's surface - a tiny fraction of the distance to the moon, let alone to Mars and other planets. Once again, given the costs, there would be little incentive for larger private ventures. It's up to government to expand Kennedy's quest for discovery.
One of the vital roles of the shuttle program was servicing the Hubble Space Telescope, replacing worn-out or outdated components. Throughout its decades of service, the Hubble has offered an extraordinarily valuable window into the depths of space, helping astronomers understand the history and fate of the cosmos to an unprecedented degree. No one would doubt its importance.
Like any instrument, however, the Hubble has a limited lifetime. Eventually, it will no longer produce the crystal-clear images of galaxies and other objects that have brought it acclaim.
The scientific community has high hopes for its planned successor, the James Webb Space Telescope. Unfortunately, though, a House committee voted last week to ax $1.6 billion from NASA's budget, effectively killing prospects for further development of the Webb Telescope. Unless that funding is restored, astronomy will suffer a devastating blow.
U.S. leadership in particle physics has fared no better. The Tevatron, the most powerful particle smasher in the country, is scheduled to be shut down in September. The Large Hadron Collider, a higher-energy machine near Geneva, Switzerland, has been up and running for more than a year, and it's besting the Tevatron. American scientists looking to do high-energy particle physics experiments will soon have to go abroad.
Sadly, the United States could have been the home of a world-champion particle smasher. But, in what has become a familiar story, financial issues got in the way.
In 1993, Congress voted to cut funding for the Superconducting Super Collider, which would have been the largest, most powerful device of its kind. At the time, almost one-third of the collider's planned 54-mile tunnel had already been dug near Waxahachie, Texas. Today, America has sent many particle-physics researchers to Europe, but much disappointment remains about the missed domestic opportunities.
While the United States still leads the way in many areas of research, such as medicine and communications technology, it has increasingly ceded its place as the driver of the largest scientific ventures. Sadly, Kennedy's dream has given way to reflexive slashing of science funding whenever budgets are tight.
Major scientific missions, which typically take decades of planning, require dedicated funding sources that can weather economic downturns. If the United States is ever to be restored to a leading role in science, the federal government must establish long-term scientific priorities with guaranteed funding to match.
Paul Halpern is a professor of physics at the University of the Sciences in Philadelphia and the author of "Collider: The Search for the World's Smallest Particles." He can be reached at firstname.lastname@example.org.