SLI meaning in Academic & Science ?

The Space Launch Initiative (SLI) was a NASA and U.S. Department of Defense joint research and technology project to determine the requirements to meet all the nation's hypersonics, space launch and space technology needs. It was also known as the 2nd Generation Reusable Launch Vehicle (RLV) program. The program began with the award of reusable launch vehicle study contracts in 2000.

The primary goal of this research was to increase safety and reliability and to reduce overall costs associated with building, flying and maintaining the nation's next generation of space launch vehicles. NASA anticipated that these advances would revitalize the nation's space transportation capabilities, and dramatically improve NASA's ability to conduct science and exploration missions in space. This program was ended with the cancellation of the X-33 and X-34 in 2001 along with the conclusion of the X-43 program. In November 2002 it was evolved into the Orbital Space Plane Program and the Next Generation Launch Technology Program.

Around 2004 NASA changed its focus to Constellation Program, as part of the Vision for Space Exploration.