NASA's Space Launch System (SLS) 70-metric-ton configuration, NASA's new heavy-lift rocket, designed to fly astronauts to the moon, asteroids and eventually to Mars, is seen launching to space in this undated artist's rendering released August 2, 2014. REUTERS/NASA/MSFC/Handout
An undated artist's concept shows the test vehicle for NASA's Low-Density Supersonic Decelerator (LDSD), a helium balloon carrying an experimental saucer-shaped NASA spacecraft designed to test landing technologies for future Mars missions. REUTERS/NASA/JPL-Caltech/Handout
The Bigelow Expandable Activity Module (BEAM) expandable space habitat technology is displayed during a media briefing in Las Vegas January 16, 2013. REUTERS/NASA/Bill Ingalls/Handout
People take pictures as the SLS five-segment Solid Rocket Motor, part of NASA's deep-space launcher project, undergoes a static test fire at the Orbital ATK facility in Promontory, Utah March 11, 2015. REUTERS/J
A prototype of a free-flying space robot equipped with a smartphone, known as Smart SPHERES (Synchronized Position Hold, Engage, Reorient Experimental Satellites), is pictured in this undated handout photo courtesy of NASA. REUTERS/NASA/Handout
The Sierra Nevada Corporation (SNC) Dream Chaser flight vehicle, a privately owned prototype space plane, is readied for 60 mph tow tests at NASA's Dryden Flight Research Center in Edwards, California, August 2, 2013. REUTERS/NASA/Ken Ulbrich/Handout
The Sunshield test unit to be used on NASA's James Webb Space Telescope is stacked and expanded at a cleanroom in the Northrop Grumman facility in Redondo Beach, California. The Sunshield separates the observatory into a warm sun-facing side and a cold side where the sunshine is blocked from interfering with the sensitive infrared instruments. REUTERS/NASA/Chris Gunn/Handout
Virgin Galactic's WhiteKnightTwo carrier aircraft mothership, which landed safely after splitting from SpaceShipTwo, is seen in a hangar at Mojave Air and Space Port in Mojave, California November 4, 2014. REUTERS/Lucy Nicholson
NASA astronauts Cady Coleman and Ricky Arnold step into the Orion crew module hatch during a series of spacesuit check tests conducted at the Space Vehicle Mockup Facility at the agency's Johnson Space Center in Houston, Texas on June 13, 2013.
NASA's new Earth-bound rover, GROVER, which stands for both Greenland Rover and Goddard Remotely Operated Vehicle for Exploration and Research, in Summit Camp, the highest spot in Greenland, is shown in this May 10, 2013 release.
The unmanned SpaceX Crew Dragon lifts off from launch pad 40 during a Pad Abort Test at the Cape Canaveral Air Force Station in Cape Canaveral, Florida May 6, 2015. REUTERS/Scott Audette
In this artist's concept, the Cassini spacecraft makes a close pass by Saturn's moon Enceladus to study plumes from geysers that erupt from giant fissures in the moon's southern polar region. REUTERS/NASA/
Chirold Epp (in blue shirt), Johnson Space Center Project Manager for ALHAT, speaks to members of the media while showing off the Morpheus prototype lander, part of the Lunar Catalyst program to develop lunar landers, in Cape Canaveral, Florida, August 1, 2012. REUTERS/NASA/Handout
NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft is pictured orbiting near the surface of the moon, in this artist's illustration released August 15, 2013. REUTERS/Dana Berry/NASA Ames/Handout
Technicians work on the heat shield of NASA's Orion space capsule at Kennedy Space Center, Florida, in this undated handout photo. Measuring 16.5 feet in diameter, the heat shield is made from a single seamless piece of Avcoat ablator. REUTERS/NASA/Handout
The X-51A Waverider, an unmanned aircraft that could reach speeds up to 3,600 mph, in flight. REUTERS/US Air Force
A SpaceX upgraded Falcon 9 rocket undergoes launch preparations at Vandenberg Air Force Base in California September 27, 2013. REUTERS/Gene Blevins
A 1.79 percent scale model of a future concept supersonic aircraft built by Boeing. REUTERS/Quentin Schwinn/NASA
Volker Maiwald (L), executive officer and habitat engineer and Hans van Ot Woud, a mapping researcher and the health and safety officer of Crew 125 EuroMoonMars B mission, return to the Mars Desert Research Station (MDRS) outside Hanksville in the Utah desert, March 3, 2013
Robonaut 2 is shown in the International Space Station's Destiny laboratory during a round of testing for the first humanoid robot in space, January 2, 2013
An artist's concept of NASA's Mars Science Laboratory spacecraft approaching Mars. The Curiosity rover is safely tucked inside the spacecraft's aeroshell. REUTERS/ NASA/JPL-Caltech/Handout
The Boeing X-37 Orbital Test Vehicle, an unmanned reusable spacecraft. REUTERS/NASA
Physicist Daniel Schildhammer wears the Aouda.X spacesuit simulator during a field test of Oesterreichisches Weltraum Forum (Austrian space forum) inside the Eisriesenhoehle (giant ice cave) at Dachstein mountain near the village of Obertraun April 28, 2012.
A computer-generated image of the Atrium aircraft, which will enable space tourists to experience weightlessness while carrying passengers briefly outside the earth's atmosphere. REUTERS/EADS Atrium/Marc Newson Ltd/NASA
Argentine aerospace engineer Pablo de Leon, a NASA team member, collects samples as he tests a space suit designed for possible use in Mars at Argentina's Marambio base in Antarctica, March 13, 2011.