NASA needs to harness the promise of nuclear technology if it hopes to do meaningful work in the solar system, the agency’s top space-science official said Tuesday. Edward Weiler, NASA’s associate administrator for space science, told lawmakers that the space program’s ambitious plan — called Project Prometheus — will enable the agency to do more than has ever been possible. “If we’re going to have a future in the outer solar system, nuclear power is a must,” Weiler told a subcommittee of the Senate Commerce Committee.