To get beyond a low-Earth orbit -- which is the beginning of space flight -- future cosmic explorers will require a more efficient means of rocket propulsion. And to get there, the team at NASA's Marshall Space Flight Center will have to "think outside the box."

Artist's drawing of Pulse Detonation Propulsion System. Photo: NASA

"Space is becoming a much more important place to be for a wide variety of reasons," said Bob Sackheim, Marshall's associate director for space propulsion. "Anything that goes farther than a low-Earth orbit has to have more efficient rocket propulsion."

Sackheim, who joined the Marshall team in September 1999, oversees all advanced space propulsion activities at Marshall. He provides technical leadership for all of Marshall's propulsion flight projects including Space Shuttle, Space Station, Pathfinder and Trailblazer projects and other various spacecraft projects. His technical leadership is focused on the exploration of space -- existing flight programs and new, innovative propulsion system development at Marshall.

Sackheim's vision for future space propulsion embraces balance between both near- and long-term space transportation programs. This includes Earth-to-orbit and in-space propulsion technologies.

The technology being developed for the X-vehicles is important, he said, because each of the X programs is testing a different phase of the technology required to send spacecraft and eventually humans beyond the low-Earth orbit. The X-programs are looking at what it will take to lower the cost of space flight.

Reducing that cost is important to NASA and the burgeoning space business industry. The United States is not yet in a strong position in that business arena, Sackheim said. "I want to do whatever I can to help American industry get where it needs to be as a leader in space transportation and space propulsion."

"We are poised at a threshold where space has the potential for a major business explosion. Telecommunications alone is expected to generate $32 billion in revenues, worldwide, by the year 2008. The launch vehicle business worldwide is $8 billion a year -- probably on the way to $20 billion a year. We only get $2-3 billion of that now. We need to recover market share by providing safe, extremely reliable and low-cost American launch services.

"I have been a champion of low-cost access to space for a lot of years," Sackheim said. "Everyone in the business of space transportation agrees we need low-cost access to space, and we have great difficulties in achieving concensus to chart the 'right' course to achieve this major goal."

The Integrated Space Transportation Program is a good start, he said, and he wants to be sure NASA achieves a balanced program of benefit to America and to NASA.

Space transportation is more important than just reaching low-Earth orbit. Everything that goes into space, goes to a low-Earth orbit and then on to a higher operational orbit.

Artist's concept of the X-37 in the Earth's atmosphere. Photo: NASA

"Marshall needs a balanced program that deals with both Earth-to-orbit and in-space propulsion," Sackheim said. "When you launch something off the ground, you are mostly carrying propellant. It takes a lot of propellant to get the ultimate payload to the higher orbit."

To do the Integrated Space Transportation Program process in a fair and balanced way NASA has to make sure all of the options get considered so that we come up with the best solutions, he said. That involves a lot of "out-of-the-box" thinking by the entire Marshall team. "I look forward to a partnership with all the Marshall directorates, other NASA Centers such as Stennis, Glenn, Ames and Langley; industry; federal institutions such as the Air Force, the Army and the Department of Energy; and academia.

"We need a dedicated activity in research and developing new technology, and we need to have that technology in place so that we can get to the operational orbits faster, better, cheaper -- and most importantly, smarter," Sackheim said.

"Technology needs to be developed off-line, and in-house. We have a lot of new young people who can do that -- Fastrac was a good example and learning opportunity for these people. We need to develop the program to achieve a technology readiness level of four to six, and then have industry take it from there. We must include propulsion-related technologies in our development plans and roadmaps. We have to recognize important technologies such as nuclear and thermal propulsion. Achieving higher technology readiness levels is important in reducing the risks. I think Marshall should develop some of these enabling technologies and make them available for industry."

Programs such as Pathfinder -- X-34 and X-37 -- are the testbeds to develop technology in the real operating environments, he said. Testing under simulated conditions is always difficult and expensive; however, the Pathfinder programs are "well conceived to solve these complex problems," Sackheim said.

In terms of Earth to orbit, Sackheim explained the only way to get a thrust to weight that is greater than one -- the thrust needed to launch a vehicle out of Earth's atmosphere -- is to use a thermal rocket. There are only two kinds of thermal rockets available today. "Nuclear is perceived as a long way off environmentally for Earth-to-orbit; therefore, vehicles must be powered by chemical combustion sources for a long time to come.

"Rocket-based combined cycle is more efficient, if we can solve the very difficult and stressing technology issues," Sackheim said. "A combined cycle propulsion system gulping air and then switching to rockets offers great potential performance benefits.

"I am looking forward to the research and development that will make that happen."