Some current and former U.S. generals like to tell a story about a young soldier who was asked whether he needed space technology to be an effective fighter. No, the soldier says, all I need is my rifle, my ammunition and this little black box that tells me where I am.

Hand-held navigation devices based on the Global Positioning System are so nearly ubiquitous that troops easily take them for granted. These devices depend on a network of satellites run by the Air Force and used by the military and civilians alike. And they are just one example of how much U.S. military strength hinges on the Pentagon’s roughly $20 billion space program. From navigation and communications, to predicting the weather and gathering intelligence, satellites are a critical part of the American arsenal.

That dependence also explains the alarm in January when the Chinese military used a medium-range missile to launch an experimental anti-satellite weapon, or ASAT. The weapon reduced a vintage Chinese weather satellite to more than a thousand pieces of debris, creating a field of space junk that now threatens other spacecraft, including the International Space Station.

The destruction of the Feng Yun 1C satellite also added thrust to a debate here and abroad about a possible new arms race in space, especially in the area of ASATs.

Some critics of administration defense policies saw China’s test as an inevitable response to an increasingly unilateral and aggressive U.S. stance in space. Those critics point to small-scale U.S. tests of hardware on the ground and in space that other countries might construe as ASAT prototypes, as well as the Bush team’s refusal to participate in international talks about limiting space weapons.

Other foreign and military policy experts saw the Chinese test differently. To them, the destruction of the weather satellite justified the administration’s hard line on space, particularly on any proposed space weapons treaty. Opponents of such negotiations say the kind of agreement sought by China and Russia would be impossible to verify. And they dismiss the treaty talk as disingenuous, especially in the aftermath of China’s recent action.

Disagreements about space weapons have gone on since the Soviet Union launched the first satellite 50 years ago this October, and similar arguments will probably rage 50 years from now, in space policy conferences at Moon Base W. For U.S. policy makers on planet Earth now, the Chinese test raises issues that go beyond this long-running debate, especially when it comes to addressing the vulnerability of U.S. satellites.

Even if a future administration were inclined to sign a new space treaty, enforcement would be difficult because some technologies that could be used to directly attack a satellite in orbit would be indistinguishable from other weapons. These include the standard rocket used in the recent Chinese test — and the modified air-launched missile the U.S. military used in a similar experiment 22 years ago. (China is not alone in having explored such weapons.)

Some seemingly peaceful technologies, such as automated systems for rendezvousing with and possibly repairing satellites, could just as easily be used for space missions that are far from benign. After all, a little shove can go a long way toward crippling a satellite in zero gravity. In addition, potential adversaries theoretically can exploit some vulnerabilities without using destructive weapons that can be launched into or based in space. These measures include terrestrial tools for jamming or interfering with communications and optics and cyber-attacks aimed at the ground-based systems used to monitor and control spacecraft.

Given all that, military planners would be irresponsible not to look for ways to cover their orbital assets. But many countermeasures involve strictly defensive capabilities that would be perfectly acceptable to people on either side of the space weapons debate.

Those defenses include hardening satellites against electronic effects and interference, increasing the maneuverability of spacecraft to avoid possible attacks and ensuring the availability of new, relatively cheap rockets to quickly launch replacements for disabled satellites. Deploying smaller, harder-to-track satellites would also make U.S. spacecraft more difficult to target. Supplementing surveillance satellites with more manned and unmanned aircraft for intelligence gathering would also help, as would increasing the use of land lines and aircraft to relay some critical communications.

The vulnerability of satellites is not limited to the military. The Global Positioning System that guides many U.S. bombs, missiles and troops also guides innumerable civilian vehicles from place to place. Similarly, the U.S. military is one of the biggest customers of civilian communications satellites. Those links make drawing the line between civilian and military targets difficult. And that makes a strategy for defending U.S. spacecraft a down-to-Earth issue for most Americans, not just the Pentagon.

Mark Stencel is deputy publisher and a technology columnist for Governing magazine, published by Congressional Quarterly Inc.