Acting NASA Administrator Robert Lightfoot gestures while testifying during a House Subcommittee on Commerce, Justice, Science, and Related Agencies hearing to review the Fiscal Year 2018 budget request for the National Aeronautics and Space Administration, Thursday, June 8, 2017 at the Rayburn House Office Building in Washington. Photo Credit: (NASA/Aubrey Gemignani)

Acting NASA Administrator Robert Lightfoot testifies during a House Subcommittee on Commerce, Justice, Science, and Related Agencies hearing to review the Fiscal Year 2018 budget request for the National Aeronautics and Space Administration, Thursday, June 8, 2017 at the Rayburn House Office Building in Washington. Photo Credit: (NASA/Aubrey Gemignani)

Acting NASA Administrator Robert Lightfoot testifies during a House Subcommittee on Commerce, Justice, Science, and Related Agencies hearing to review the Fiscal Year 2018 budget request for the National Aeronautics and Space Administration, Thursday, June 8, 2017 at the Rayburn House Office Building in Washington. Photo Credit: (NASA/Aubrey Gemignani)

U.S. Representative José Serrano, D-New York, asks a question after acting NASA Administrator Robert Lightfoot testified during a House Subcommittee on Commerce, Justice, Science, and Related Agencies hearing to review the Fiscal Year 2018 budget request for the National Aeronautics and Space Administration, Thursday, June 8, 2017 at the Rayburn House Office Building in Washington. Photo Credit: (NASA/Aubrey Gemignani)

Acting NASA Administrator Robert Lightfoot testifies during a House Subcommittee on Commerce, Justice, Science, and Related Agencies hearing to review the Fiscal Year 2018 budget request for the National Aeronautics and Space Administration, Thursday, June 8, 2017 at the Rayburn House Office Building in Washington. Photo Credit: (NASA/Aubrey Gemignani)

Acting NASA Administrator Robert Lightfoot testifies during a House Subcommittee on Commerce, Justice, Science, and Related Agencies hearing to review the Fiscal Year 2018 budget request for the National Aeronautics and Space Administration, Thursday, June 8, 2017 at the Rayburn House Office Building in Washington. Photo Credit: (NASA/Aubrey Gemignani)

Acting NASA Administrator Robert Lightfoot testifies during a House Subcommittee on Commerce, Justice, Science, and Related Agencies hearing to review the Fiscal Year 2018 budget request for the National Aeronautics and Space Administration, Thursday, June 8, 2017 at the Rayburn House Office Building in Washington. Photo Credit: (NASA/Aubrey Gemignani)

Acting NASA Administrator Robert Lightfoot testifies during a House Subcommittee on Commerce, Justice, Science, and Related Agencies hearing to review the Fiscal Year 2018 budget request for the National Aeronautics and Space Administration, Thursday, June 8, 2017 at the Rayburn House Office Building in Washington. Photo Credit: (NASA/Aubrey Gemignani)

U.S. Representative John Culberson, R-Texas, chairs a hearing to review the Fiscal Year 2018 budget request for the National Aeronautics and Space Administration, Thursday, June 8, 2017 at the Rayburn House Office Building in Washington. Acting NASA Administrator Robert Lightfoot provided testimony at the hearing. Photo Credit: (NASA/Aubrey Gemignani)

Acting NASA Administrator Robert Lightfoot testifies during a House Subcommittee on Commerce, Justice, Science, and Related Agencies hearing to review the Fiscal Year 2018 budget request for the National Aeronautics and Space Administration, Thursday, June 8, 2017 at the Rayburn House Office Building in Washington. Photo Credit: (NASA/Aubrey Gemignani)