RENO, NEVADA -- The economic ups and downs of reusable rocketry largely depends on beat-the-heat protection systems. Without a robust, temperature-thwarting, and easily maintainable outer skin, rockets of the future may never offer routine, low-cost access to space.

For today's space shuttle fleet, seven different materials are used per orbiter. These materials were chosen for their weight efficiency and constancy at high temperatures. Each space plane is outfitted from nose to tail with a matrix of specially made black and white tiles, quilted composite fabric and Nomex blankets, along with other materials specific to select areas of the craft.

Collectively, this high-tech hide is labeled the thermal protection system, or TPS in NASA speak.

But after a shuttle orbiter brakes from orbital speed, makes its fiery plunge to Earth, then rolls to a stop…things really slow down.

Getting the vehicle ready for re-launch is a long and costly process. About 30,000 hours of work is needed between flights - and that's on the TPS alone. The TPS is reusable for 100 missions, but only after loads of hands-on, tender-loving care.

A new Adaptable, Robust, Metallic, Operable, Reusable TPS -- tagged ARMOR for short -- has been designed, analyzed and fabricated. It promises to help achieve a NASA goal of cheaper rides for people and payloads into space and back.

At the American Institute of Aeronautics and Astronautics (AIAA) 40^th Aerospace Sciences Meeting held here January 14-17, ARMOR was touted as a cutting-edge advance in metallic thermal protection systems.

"For future vehicles to become economically viable, and have fast turnaround times, we need TPS that requires a lot less maintenance," said Max Blosser, a senior research engineer at NASA's Langley Research Center in Hampton, Virginia.

Blosser said a present drawback to space shuttle TPS is that it can't fly through Florida's liquid sunshine. "Rain would destroy the TPS tiles. We're trying to come up with a TPS that's more durable, increases the flight envelope of the vehicle…so you don't have as much time that you can't fly," he told SPACE.com.

The Bush Administration is placing importance on developing a new generation of safer, more reliable and less expensive launch vehicles for both government and commercial needs.

To this end, work is underway at NASA's Marshall Space Flight Center on the Space Launch Initiative (SLI). A 2^nd generation reusable launch vehicle (RLV) -- the space shuttle being a 1^st generation RLV -- is a hoped for entry to lower the cost of tossing payloads into low-Earth orbit to less than $1,000 per pound. Today's "going price" via the shuttle is roughly $10,000 a pound.

The SLI is a focused investment of nearly $5 billion spread out over a five-year period. Research on the 2^nd generation RLV includes studies of metallic TPS, Blosser said.

"ARMOR TPS is designed to meet the high flight rates and quick turn-around times required for an economically viable RLV," said John Dorsey, a senior research engineer, also at NASA Langley. "It is anticipated there will be many parallels between aviation industry operations and maintenance and future reusable launch vehicle industry practices," he said.

"The current ARMOR concept is basically taking lessons learned from previous work since the 1980s, including the more recent X-33 effort," Blosser said. That sub-scale single-stage-to-orbit space plane was to help Lockheed Martin build the VentureStar - a commercial Earth-to-orbit winged vehicle. NASA scrapped the X-33 effort last year.

Several ARMOR TPS panels have been fabricated. The outer surface is a foil-gage, Inconel 617 metallic honeycomb sandwich panel. This outer panel is structurally connected to an inner box beam by a thin Inconel 718 metal support bracket at each corner of the panel. The ARMOR TPS design provides three different sealing features so panel-to-panel placement on a vehicle inhibits hot gases during reentry from eking between panels.

Attachment of the metallic TPS is almost a snap.

Each panel is attached to the underlying structure by means of mechanical fasteners. The ARMOR TPS is built to accommodate aerodynamic pressures, as well as thermal conditions found in the cold of space and throughout the heat of reentry. Furthermore, rainwater and moisture is managed by a thin gage metal foil that closes out the bottom of the TPS panel to make a watertight container for internal insulation.

"Metallic TPS can be designed to prevent water from reaching the internal insulation, thereby eliminating the need for time-consuming re-waterproofing procedures required for current ceramic TPS," Blosser reported at the AIAA gathering. "The relatively large, mechanically attached metallic TPS panels can be designed to be readily removed for inspection or repair," he said.

Blosser said that next generation reusable launch vehicles -- replete with integral fuel tanks -- will result in bigger, lower density vehicles with much larger surface areas than a space shuttle orbiter. This larger surface area must not only be protected from aerodynamic heating, but also may be exposed to damage from low-speed impacts during ground operations, launch and landing. Also, speedy on-orbit impacts from micrometeoroids and space debris, and rain erosion during ascent and entry, demand new types of TPS materials.

"Micrometeoroid and on-orbit debris damage…I think that's going to a much bigger driver as we really face up to it in the future," Blosser said. "By changing the thickness of ARMOR's honeycomb face sheets, you can achieve whatever level of micrometeoroid protection you want. But that does come at the cost of additional weight," he added.

Blosser said he considers ARMOR panels a "step in the right direction".

"Just to tweak the system we have on the shuttle, personally, I don't think that's ever going to get us there. We have to look at some other alternatives," Blosser said.

Getting test time on a vehicle, Blosser noted, to try out samples of ARMOR under actual flight conditions, has proven difficult. Two small panels of the TPS material were to fly on the X-37 spacecraft. That plan was derailed when NASA shut down the experimental project. "The X-37 is kind of in limbo, if not dead," he said.

Lastly, funding for new TPS work remains minimal. "It would be good to see a more comprehensive, long-term plan to get us there. To get new TPS technology onto the vehicles is going to take a more intentional, step-by-step approach," Blosser said.