Space Launch Initiative

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. 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 and the conclusion of the X-43 programs. NASA changed its focus to Constellation Program.

The Space Launch Initiative Propulsion Office, managed by NASA’s Marshall Space Flight Center in Huntsville, Ala., sought to advance technologies and explore new avenues of space propulsion to develop safer, more reliable and affordable propulsion solutions. Four main engine candidates for a second generation reusable launch vehicle emerged, including two hydrogen-fueled (COBRA, RS-83, TR-106) and two kerosene-fueled (RS-84, TR-107) staged combustion engines.

Space launch

Space launch is the earliest part of a flight that reaches space. Space launch involves liftoff, when a rocket or other space launch vehicle leaves the ground, floating ship or midair aircraft at the start of a flight. Liftoff is of two main types: rocket launch (the current conventional method), and non-rocket spacelaunch (where other forms of propulsion are employed, including airbreathing jet engines or other kinds).

Issues with reaching space

Definition of space

Space has no physical edge to it as the atmospheric pressure gradually reduces with altitude; instead, the edge of space is defined by convention, often the Kármán line of 100 km. Other definitions have been created as well, in the US for example space has been defined as 50 miles.

Energy

Therefore, by definition for spaceflight to occur, sufficient altitude is necessary. This implies a minimum gravitational potential energy needs to be overcome: for the Kármán line this is approximately 1 MJ/kg. W=mgh, m=1 kg, g=9.82 m/s², h=10⁵m. W=1*9.82*10⁵≈10⁶J/kg=1MJ/kg