WASHINGTON -- Here is the blunt truth. The days of only round-cornered spacecraft punching through Earth's atmosphere may be numbered.
New thermal protection materials could lead to radically different types of future vehicles. The needle-nose spaceships of vintage science fiction films may yet turn into reality.
In a September 28 test shot of a U.S. Air Force
Minuteman 3 missile from Vandenberg Air Force Base in California, Ultra-High Temperature Ceramics (UHTCs) flew at blistering speed, then plunked down in a lagoon at the Kwajalein missile range in the Pacific Ocean.
Think of it as "SHARPshooting."
The materials were part of the Slender Hypervelocity Aero-thermodynamic Research Probes (SHARP) program, a joint effort among NASA,
Sandia National Laboratories and the U.S. Air Force.
The recovered materials have bolstered the promise of sharp-body technology for Earth-returning space vehicles, as well as planetary probes.
Heat-loaded history
In the premier days of space research, a long, pointed cone made from heat-hardened metal was a shape scientists knew would dive most easily back through the atmosphere -- less friction, less heat.
But those early tests revealed that every known material would melt in the intense blast furnace of Earth reentry as it ran into ever-denser air at high speeds.
Pioneering space engineers came up with the blunt-body design.
This was an aerodynamic solution that created a region of compressed air in front of the vehicle as it traveled faster than the speed of sound. This region absorbs much of the heat associated with a spacecraft's reentry into Earth's atmosphere, keeping a vehicle's edges from overheating.
Blunt bodies outfitted with special materials became a way to carry friction heat around the vehicle and leave it behind in a very hot wake.
For decades, engineers have fabricated spacecraft with blunt leading edges. The Mercury, Gemini and Apollo capsules, as well as the space shuttle, all have adopted this approach to "beating the heat" of reentry.
Flying wind tunnel
The Minuteman 3 test shot a few weeks ago toted a trio of reentry vehicles -- basically aerodynamic nosecones.
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The SHARP vehicle coating's ability to withstand the heat of reentry was put to the test. |
One of those three reentry vehicles -- tagged the SHARP B2 -- was equipped with small-in-length "strakes," or sharp leading edges. Each of the strakes consisted of heat-thwarting ceramic material segments.
The booster roared to an altitude of about 400 nautical miles (741 kilometers), then released its payload of reentry vehicles. The strake-equipped reentry vehicle carried sensors to see how the ceramic thermal materials reacted during the 23-minute suborbital flight and as they confronted extremely high temperatures that skyrocketed to upwards of 5,000 degrees Fahrenheit (2,760 degrees Celsius).
In essence, the Minuteman serves as a flying wind tunnel, allowing materials to be exposed to speeds in excess of Mach 20 -- or 20 times the speed of sound.
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A key step
"Everything went as planned," said Joan Salute, project manager for the mission at NASA’s Ames Research Center, near San Francisco, California. The test data gleaned is expected to spark "a whole revolution and a new way to do things," she said.
Reached by SPACE.com at the Kwajalein missile range, Jeff Bull, an Ames materials engineer working on the project, said that the SHARP B2 vehicle has been successfully recovered.
"The vehicle is intact and in good shape from the strake locations forward," Bull said. A malfunction in a parachute, however, caused the vehicle to impact in lagoon waters at a much higher than expected speed, he said.
"We think the recovery and reported good flight-data collection will allow us to meet all experimental objectives. SHARP B2 should prove to be a key step in enabling future sharp body aerospace vehicles," Bull told SPACE.com.
Buck Rogers approach
The SHARP program has been underway since the early 1990s. It is one of the experiments under the Pathfinder Program, managed by NASA’s Marshall Space Flight Center.
Salute said that extensive ground testing, as well as an earlier Minuteman test shot in 1997, of ultrahigh temperature ceramic material are helping mold future space transportation ideas.
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With tougher ceramics, needle-nosed spacecraft like this NASA L1 concept, could reenter at higher speeds and ultimately less wear. |
"Tests have shown us that the materials can withstand over 5,000 degrees Fahrenheit (2,760 degrees Celsius). That’s well above what the space shuttle sees at 2,800 to 3,000 degrees Fahrenheit (1,535 to 1,650 degrees Celsius). So by having these materials, it enables a whole new vehicle design," Salute said.
SHARP work will allow vehicles that "look more like the Buck Rogers approach" to space travel, said Daniel Rasky, the project’s principal investigator in NASA’s Office of Aerospace Technology.
Sling shot between worlds
NASA’s Rasky said that by using the new materials, losing contact with incoming and outgoing spacecraft traveling at high speeds would be a thing of the past.
SHARP-body technology, Rasky said, reduces the ionization layer that builds up around vehicles, like the space shuttle during reentry, which cuts off communications with ground control.
Studies are already underway to look at SHARP technology for space vehicles boosted skyward at high speeds by magnetic levitation, as well as for future generations of air-breathing rockets, Rasky said. More near-term is the use of ultrahigh temperature ceramic materials for a crew rescue vehicle, he said.
Rasky said that SHARP research is also spurring a look at "aero-gravity assist" -- a way to dip deep into the atmosphere and gravity well of a planet -- enabling a vehicle to efficiently slingshot between worlds.
It’s the future...get the point?
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