NASA is known worldwide for routinely putting people into Earth orbit. The agency is also revered as the only organization that has flung humans at escape velocity speeds to the Moon. However, NASA could also be known as an agency that's going nowhere fast.

Even NASA's new chief, Sean O'Keefe, is keen about the need for speed. The agency is stuck in slow gear, he gripes, scooting about in spacecraft today at velocities not much greater than when John Glenn first sped into Earth orbit over 40 years ago.

To help put some "momentum" into NASA, the agency is pushing forward on a nuclear propulsion and power initiative. Welcome news in contrast to the past. Over the years, NASA's advanced propulsion agenda has done little but advance in age.

To open up the solar system to vigorous robotic and future human exploration, new forms of space propulsion are being sought. Not only are faster trip times to select targets made possible. Advanced propulsion allows more exhaustive, long-term surveys of planets and their moons, as well as comets, asteroids, and other bodies.

NASA has kick-started an In-Space Transportation Investment Area effort. This new endeavor embraces a wish-list of high, medium, and low priority technologies, evolved from a space agency-wide look last year that focused on advanced missions over the next 10 to 15 years. Better yet, there is money now targeted to boost wish-list technologies into being.

NASA's Marshall Space Flight Center, Huntsville, Alabama, is leading the In-Space Transportation investment work -- spread out through the NASA research network --. They are spearheading the endeavor for the space agency's Office of Space Science in Washington, D.C.

"I think we've got a real chance here," said Les Johnson, the implementation manager for the advanced propulsion work. "We're trying to take the things people have talked about for years, but get sustained commitment to go make them happen," he told SPACE.com.

Making them happen, Johnson added, means maturing propulsion ideas to a technology readiness level just short of actual flight.

High-priority in-space propulsion technologies include:

• Aerocapture: Using a planet's atmosphere to slow a spacecraft. A vehicle built for aerocapture can slip into orbit in one pass through an atmosphere. No need for on-board propulsion. This saves mass and permits use of a smaller, less-expensive launcher. These technique gets a vehicle to a destination quickly, hastening start-up of science operations;
• Next Generation Electric Propulsion: Improve the performance of this technology, from ion engines to fission propulsion drives. High-throughput, lightweight, and more powerful ion engines, for example, enable a host of future space missions, including a Europa Lander, a Saturn Ring Observer, a Neptune Orbiter, and a Venus Surface Sample Return probe; and
• Solar Sails: Strong, lightweight composite materials fashioned into a large sail. Requiring no fuel, a solar sail relies on the steady push of photons from the Sun. A major challenge is how best to unfurl a thin sail in space, then control its direction. Sail propulsion is seen as the way to launch an interstellar precursor mission in the next decade.

Johnson said by combing the work of NASA centers with industry and academia, these high priority technologies and others -- particularly, nuclear electric propulsion -- will be moved up in technological readiness for flight in space.

"We want to get these technologies to the point that everything that can be done on the ground has been done…and they are ready to go fly," Johnson said. NASA calls this pre-flight status as Technological Readiness 6 or TR-6.

No single propulsion scheme fits all needs.

For instance, in some cases, rapid trip time is not as critical, contrasted to more payloads delivered to the target. "That's why we're investing in more than one technology…because there's no one answer for everything," he said.

Inside and outside NASA, a range of promising propulsion schemes being pursued.

One intriguing prospect is a propellantless propulsion concept tagged by some as a plasma sail. The scheme is the brainchild of Robert Winglee, a scientist at the University of Washington in Seattle.

His Mini-Magnetosphere Plasma Propulsion, or M2P2 for short, takes advantage of the natural environment of space. M2P2 technology creates a huge magnetic bubble around an interplanetary craft. In deploying the mini-magnetosphere, this plasma "balloon" interacts with high-speed ionized particles shed by the Sun that, in turn, push the vehicle through space.

"The technology seeks to do what space does -- deploy a magnetized sail to travel with the winds," Winglee said. Plasma sail technologies could cut conventional trip times to the outer planets in half. The NASA Institute for Advanced Concepts (NIAC) funded early work on Winglee's M2P2 notion.

A new test chamber at the university, Winglee said, has proven helpful in exploring the intricacies of creating a plasma balloon. "We're very happy with the results to date that we are seeing…very similar to computer simulations. That's a great relief, actually," he said.

If the flow of funding continues full-throttle, Winglee feels the plasma sail can be pushed to the NASA TR-6 level. Ultimately, the concept's enhanced thrust could be tested in some sort of geosynchronous orbit, he said.

Meanwhile, at NASA's Johnson Space Center (JSC) in Houston, Texas, lab work continues on the Variable Specific Impulse Magneto-plasma Rocket.

Better known as the VASIMR, this technology could result in shorter trip times to the planets than now available, made possible by varying the rocket's specific impulse. It can be operated in a mode that maximizes propellant efficiency or a mode that maximizes thrust, reported Andrew Petro at an aerospace gathering this past January.

Petro, a JSC spacecraft engineer, and astronaut Franklin Chang-Diaz are part of a team of advanced space propulsion experts engaged in shaping a proposed test of the rocket on the International Space Station (ISS).

The ISS experiment would show the prototype engine's ability to help negate electrical charging on the outpost and also counter drag forces that act on the orbiting facility.

"This experiment will provide an opportunity to demonstrate the performance of the rocket in space and measure the induced environment," Petro reported.

One advanced space transportation technology is tether-based propulsion.

A NASA team, including the University of Illinois at Urbana-Champaign, Tennessee Technological University in Cookeville, and Tethers Unlimited of Lynnwood, Washington are developing the Momentum Exchange, Electrodynamic Reboost (MXER) tether. This spinning, tether-based satellite in low Earth orbit would snare slower-moving objects and toss them at increased speed toward higher orbits.

This idea is akin to two ice skaters that "crack the whip" - launching one another at high speed across the ice.

By briefly linking a slow-moving object with a faster one the slower object's speed may be dramatically increased as some of its counterpart's momentum is transferred between the two.

MXER follow-on work could pave the way for chucking payloads beyond low-Earth orbit, perhaps paving the way for a human return to the Moon or flinging cargo and crew outward toward the distant dunes of Mars.

The arena of laser propulsion continues to bloom, said Leik Myrabo, CEO of Lightcraft Technologies, Inc., headquartered in Bennington, Vermont. He predicts a revolution in low-cost access to space, and actively promotes the use of beamed energy propulsion to accelerate vehicles called Lightcraft into orbit for a fraction of the cost it currently takes to get any object into space.

Recent experiments, Myrabo said, have centered what heat-thwarting materials can be applied to the ceramic engine of a Lightcraft. Engine coatings must take the ferocious high temperature environment that laser propulsion produce, permitting a Lightcraft to "glow, and still go," he said.

The first national workshop on laser propulsion is slated for this November in Huntsville, Alabama, Myrabo said, organized to transform the embryonic work on laser propulsion technology into real space transportation systems of the future, he said.

If you want an uplifting view of laser propulsion ask Tom Meyer of the Boulder Center for Science and Policy in Colorado. He has led a study team on the feasibility of building a laser elevator, reporting their findings recently in the Journal of Spacecraft and Rockets, a publication of the American Institute of Aeronautics and Astronautics (AIAA).

"The laser elevator works much like a lift in a garage, raised by a piston. But in this case, the piston is replaced by an intense beam of light that recycles between a spacecraft-mounted mirror and a mirror fixed to the laser source," Meyer said.

This laser elevator requires technology that is not too distant from the current state-of-the-art, Meyer said. Once developed, such propulsion hardware could rapidly deploy a lightsail to scrutinize a threatening asteroid or comet. Also studied was using the recirculating beam system to launch a probe to Pluto, reaching that far-away world in about 6.5 years, he said.

Leave no stone unturned is seemingly a propulsion ploy of NASA's Glenn Research Center in Cleveland, Ohio. This center is home for the Breakthrough Propulsion Physics Project.

All manner of "exotic" research is ongoing. That includes delving into transient inertia effects, quantum vacuum energy, zero-point electromagnetic energy and Casimir forces, or exploring anomalous superconductor gravity effects and superluminal quantum tunneling.

In short, any near-term success in any of these areas might foster the space drives of tomorrow.

"We're basically on a steady course, albeit running at the slow pace typical of such small projects. Our work is presently operating at a funding level of about a half-million dollars per year," said NASA's Marc Millis who manages the effort.

Millis said that a significant step for the project took place in January of this year. A Breakthrough Propulsion Physics Research Consortium has been established via a cooperative agreement with the Ohio Aerospace Institute.

"This research consortium will reach out to geographically dispersed researchers to find, support, and coordinate the best research to make credible progress toward the visionary goals we have, and to disseminate the results for the benefit of all," Millis said.

While there is no shortage of interesting advanced propulsion designs, many proposals could remain in the realm of visionary speculation. What is needed is commitment and doses of research dollars and lab time to bring them into being.

"NASA has to do things differently in the future," explains NASA chief, Sean O'Keefe. "One of the major obstacles of deep space travel is finding fast and efficient ways to get around…to get to anywhere."

"Conventional rockets and fuel simply aren't practical as we reach further out into the cosmos," O'Keefe notes. "If we're going to pioneer the future as only NASA can, we're going to need new ways to get us there," he concludes.