With room for 11 small shoebox-sized CubeSats on the first test flight of NASA's behemoth Space Launch System, agency officials have turned to scientists, industry and students to fill the slots in time for launch in 2018.

NASA has selected three CubeSats developed by internal government teams for flight on the SLS demonstration launch, and officials announced last week two more top candidates that could be manifested on the mission.

The Space Launch System is scheduled to lift off from NASA's Kennedy Space Center in Florida in 2018, lofting an unmanned Orion capsule on a flight around the moon. Astronauts will strap inside the Orion spacecraft on the second SLS flight, which is set for 2021.

The Orion crew capsule's mission will last about three weeks before returning to Earth for a splashdown in the Pacific Ocean.

But the SLS upper stage, derived from an engine used on the Delta 4 rocket, will send a package of secondary payloads on long-distance journeys into deep space. The CubeSats will be mounted inside a ring-like adapter connecting the Orion capsule with the rocket, using flight-proven deployment pods to spring-eject the satellites into space.

Lunar Flashlight, BioSentinel and Near-Earth Asteroid Scout are three CubeSats already approved for launch on the first SLS test flight. NASA's division in charge of developing next-generation space exploration technologies is sponsoring the three CubeSat payloads, which are 30-pound, six-unit versions of the CubeSat form factor regularly launched into Earth orbit.

No CubeSat has flown into deep space before, and NASA officials see an opportunity to collect basic science data at a fraction of the cost of conventional space missions.