U.S. Rep. Mark Udall, D-Colo., makes a point during a hearing of the House Science & Technology Committee regarding NASA's FY 2007 budget request, Thursday, Feb., 16, 2006, in Washington. Photo Credit: (NASA/Bill Ingalls)

U.S. Senator Mark Udall (D-CO) speaks at a Green Propellant Infusion Mission press conference at the Reserve Officers Association, Tuesday, July 9, 2013 in Washington. The NASA GPIM program, led by Ball Aerospace in conjunction with Aerojet Rocketdyne, is demonstrating a high-performance "green" fuel in space. The propellant used on this mission offers nearly 50 percent better performance when compared to traditional hydrazine. Photo Credit: (NASA/Carla Cioffi)

U.S. Senator Mark Udall (D-CO) speaks at a Green Propellant Infusion Mission press conference at the Reserve Officers Association, Tuesday, July 9, 2013 in Washington. The NASA GPIM program, led by Ball Aerospace in conjunction with Aerojet Rocketdyne, is demonstrating a high-performance "green" fuel in space. The propellant used on this mission offers nearly 50 percent better performance when compared to traditional hydrazine. Photo Credit: (NASA/Carla Cioffi)

Sen. Mark Udall, D-CO, asks a question during a hearing in front of the Senate Subcommittee on Strategic Forces and Senate Committee on Commerce, Science, and Transportation on Wednesday, July 16, 2014, at the Hart Senate Office Building in Washington, DC. The Senate hearing focused on assured access to space.