Space stability is a fundamental U.S. national security interest. Unfortunately, that stability may be eroding. Potential enemies understand the high degree to which space systems enhance U.S. conventional warfighting capabilities, and a growing number of them are acquiring the ability to degrade or destroy those systems. However, the risk is not the same for all space systems in all types of crises or at all levels of war. Some systems are more vulnerable than others, and different types of attacks offer different cost-benefit payoffs to attackers. Therefore, each space system has a different threshold at which efforts to deter attacks on it could fail. The United States can raise the thresholds of deterrence failure in crises and at some levels of limited war by implementing a coordinated national space deterrence strategy designed to operate on both sides of a potential adversary's cost-benefit decision calculus simultaneously. This strategy should begin with a national space policy that declares that the United States will punish space aggressors in ways, times, and places of its choosing. The United States should also take steps to reduce the benefits an enemy might expect to gain in attacking U.S. space systems. Future research will determine the most effective and affordable mix of strategies, policies, and systems for strengthening space deterrence.