NASA Administrator Jim Bridenstine floated this idea during the Next-generation Suborbital Researchers Conference back in March. They’re clearly moving forward with it.
Bridenstine has mentioned that NASA needed some sort of plan to certify the vehicles. It will be interesting to see what the space agency will require of Blue Origin’s New Shepard and Virgin Galactic SpaceShipTwo before conducting any astronaut training on the suborbital systems.
The vehicles can provide several minutes of continuous weightless as well as experience in rocket-powered acceleration and re-entry.
Astronauts train aboard aircraft flying parabolic arcs that provide about 25 seconds of microgravity at a time. NASA contracts for training with Zero Gravity Corporation, which uses a modified Boeing 727.