But a discussion paper published in 2006 by the Brookings Institution called for a much bigger commitment, with government prizes ranging from $15 million for an Earth-Moon solar sailcraft race to as much as $100 million a year for improvements in African agriculture. Mr. McCain’s own proposal for spurring development of alternative energy sources was foreshadowed by a bill introduced last year in Congress that would establish a prize for breakthroughs in the development of hydrogen power.