SpaceX plans to fly an Orbcomm 2 smallsat on its next ISS resupply mission, after pulling it from its first flight to the station because of NASA safety concerns. NASA is flying its small Phonesat experiment as a secondary payload on Orbital's Antares station-resupply rocket. Those precedents can lead to regular cubesat rides to orbit.

NASA already has programs to launch cubesats as secondary payloads on its scheduled missions, as does the Pentagon. In February, the civilian space agency picked 33 more small satellites to fly under its Educational Launch of Nanosatellites program, and this month issued another call for proposals for launches in 2013-16.

Added to the U.S. National Laboratory Facility on the ISS, there are a lot of free rides to space for small scientific payloads, and secondary payloads are another source of government funds for launch service providers. There is increasing commercial interest in small satellites—ATK recently expanded its line of smallsats downward in scale—so the launch market is likely to grow.

But Carroll warns that there are some risks. Of particular concern is the space-debris issue. Most current cubesats are short-lived, uncontrolled and right at the lower size limit of what can be tracked from the ground.

“The real solution to my mind is to launch on Dragon but attach to the Falcon second stage,” Carroll says. “After [main engine cutoff], the Dragon goes its separate way, and the Falcon is available for use” to place secondary payloads in safe orbits, using the stage's excess capacity.