Because most nations who fund space exploration do so in order to accrue national benefits - whether technological, military, or simply in national prestige - the development of international cooperation has long been balanced against concerns for such national benefits. It should be observed that many international space projects, such as Spacelab and Ariane, have proved particularly successful because each nation involved has contributed in its own areas of specialization. Such alliances have yielded large amounts of knowledge that could then be shared satisfactorily - as could the prestige involved as well.
The costliness of manned space activities has fueled the ongoing dispute over the desirability of involving astronauts and cosmonauts in operations that can also be conducted automatically by means of remote control. Many tasks of space exploration are in fact best performed by unmanned systems, but the most complex and unpredictable operations often exceed the capacity of computers and telemetric systems and instead require the presence of flexible, perceptive, imaginative humans. Experience on Earth has demonstrated that the most valuable discoveries in exploration and research are often those which were completely unexpected and hence those which unmanned systems might overlook.
Long-range planning for space exploration is bedeviled with the down-to-Earth problems of political and budgetary support. Despite the general desire for consistent levels of space funding, nations customarily do not plan budgets for decades in advance. National interest in space activities also waxes and wanes, with dramatic variations based on opportunities that arise for achieving relatively short-term goals. Major space projects in the United States, at least, have tended to take place in sprints, with long pauses in between. Realistically speaking, they will probably continue to do so.
The high cost of space exploration has led to major efforts to economize, and this in turn has created the conflict between reusable and expendable spacecraft systems, primarily in the area of launch vehicles. The issue is complicated by the fact that the largest costs of space operations usually are not for the hardware but instead for mission checkout, preparation, and management, and these costs may actually be increased if the space vehicle being prepared has already been used several times. In addition, reusable space systems must sacrifice a significant portion of their performance in order to include recovery aids, such as wings or parachutes. Thus, "throwaway" systems may actually be cheaper to operate, pending the development of advanced space vehicles that can be recycled economically.
The promise of space industrialization remains thus far unrealized, because of the continuing high cost of space operations and because ground industrial technologies also continue to advance. The high start-up costs for the space industry, combined with the excessively long lead times between investment and payoff, have been major factors in discouraging the development of such projects by private corporations. Clearly, however, a number of high-value, low-volume products could be manufactured in space at an advantage, and the commercial sale of some products has begun.
Few space-exploration issues are more emotional or have more diplomatic and ideological connotations than the conflict over space militarization versus treaty restrictions. Space is already a transit region for military missiles, and it has served as a vantage point for military reconnaissance since soon after Sputnik. Several limited antisatellite (ASAT) systems have also been developed, and the Soviet Union has an orbital "killer" satellite. Nevertheless, efforts to develop space-based weapons systems such as the U.S. Strategic Defense Initiative program are considered by many to be excessive and inflammatory. Technical issues are poorly defined in this dispute, which is grounded mainly in political doctrines.