NASA is another step closer to defining the next-generation reusable space transportation system and successor to the Space Shuttle.

The Space Launch Initiative (SLI), a NASA-wide effort
defining the future of human space flight, has completed its
first milestone review — resulting in a narrower field of
potential candidates for the nation’s second-generation
reusable space transportation system.

“To use the resources afforded by space, it’s critical to
increase reliability and safety while at the same time
reducing the cost of space transportation,” said Art
Stephenson, director of NASA’s Marshall Space Flight Center,
Huntsville, Ala., which manages the SLI for the Office of
Aerospace Technology. “The Space Launch Initiative is doing
the groundwork to accomplish these goals and create a second-
generation launch system.”

“We’re not just designing a launch vehicle,” added Dennis
Smith, also of Marshall, program manager of the Space Launch
Initiative. “We’re designing the complete system.”

The recent review, called the Initial Architecture Technology
Review, analyzed and evaluated competing second-generation
reusable space transportation architectures and technologies
against NASA and commercial mission requirements, as well as
safety and cost goals.

Architecture refers to the complete transportation system
design — that is, the vehicles and their components that fly
into space, as well as the ground operations needed for
launch. The transportation system design includes an Earth-
to-orbit reusable launch vehicle (the Space Shuttle is the
first-generation reusable launch vehicle); on-orbit transfer
vehicles and upper stages to put satellites into orbits;
mission planning; ground and flight operations; and support
infrastructure, both on orbit and on the ground.

Three contractor architecture teams — The Boeing Company of
Seal Beach, Calif.; Lockheed Martin Corp. of Denver; and a
team including Orbital Sciences Corp. of Dulles, Va., and
Northrop Grumman of El Segundo, Calif. — presented dozens of
potential architectures for review. Following the review,
each retained a handful of possible candidates for the
nation’s next-generation reusable space launch system.

The review allows the Space Launch Initiative to target
investments and support what the program manager called the
“up-front, homework part of the program” — furthering
technologies to aid in the development of a second-generation
reusable launch vehicle. Another review will be held in
November to further narrow potential space transportation
architectures to two or three choices.

“We’re going to seek the final and best ideas from industry,
academia and government,” said Smith. With the final
selection of an architecture, full-scale development of a
reusable launch vehicle could begin around the middle of this

Since propulsion systems require a long lead-time to design,
develop, test and evaluate, it isn’t surprising that
propulsion analysis was a chief driver through the recently
completed review activity.

“We spent a lot of time analyzing propulsion technologies,”
said Smith. “Among the outcomes is a focus on kerosene-fueled
main engines.” This focus is based on studies, conducted by
the architecture contractors, that examine performance of
competing technologies in safety, reliability, cost and
operability. Studies indicated that kerosene main engines
have excellent potential to meet government and commercial
needs. The second-generation vehicle will have a two-stage-
to-orbit propulsion system based on engines fueled by all
kerosene, all hydrogen or a combination of kerosene and

Dependable, long-life engines, along with crew escape and
survival systems, and long-life, lightweight integrated
airframes are among the Space Launch Initiative’s highest
priorities. Each greatly impacts the program’s bottom line of
increased safety, reliability and cost effectiveness.

All NASA’s field centers and the Air Force Research
Laboratory are actively participating in the Space Launch
Initiative. Additional information on NASA’s Space Launch
Initiative, including a list of the selected contractors, is
available on the Internet at: