WASHINGTON — NASA Marshall Space Flight Center, Huntsville, Ala., said June 21 that the Space Launch System’s (SLS) cryogenic core stage recently passed its first major technical review, clearing prime contractor Boeing Space Exploration to begin the heavy-lift rocket’s design phase.

The combined Systems Requirements Review and System Definition Review held the week of June 18 at Marshall validated that Boeing and NASA developed sound system requirements for the shuttle-derived launcher’s cryogenic stage and supporting hardware.

“Now that we have completed this review, we go from requirements to real blueprints,” Tony Lavoie, manager of the SLS Stages Element at Marshall, said in a statement. “We are on the right track to deliver the core stages for the SLS program.”

The SLS core stage, an 8.4-meter-diameter structure that will stand more than 60 meters tall, will store liquid hydrogen and liquid oxygen to feed its four Pratt & Whitney Rocketdyne RS-25 engines. NASA intends to use RS-25s left over from the space shuttle program for the first few SLS flights. NASA has 16 RS-25 space shuttle main engines in inventory to use for SLS, the agency said.

SLS is slated to make its debut in 2017 on a test flight launching an unmanned Orion Multi-Purpose Crew Vehicle on a trajectory around the Moon. The rocket’s first crewed flight is scheduled for 2021.

Brian Berger is editor in chief of SpaceNews.com and the SpaceNews magazine. He joined SpaceNews.com in 1998, spending his first decade with the publication covering NASA. His reporting on the 2003 Space Shuttle Columbia accident was...