News Column

Local 'sci-fi' projects advance in NASA competition

August 13, 2014

By Tom Beal, The Arizona Daily Star, Tucson



Aug. 13--Astronomer Christopher Walker has three slips of paper from fortune cookies taped to his door. One reads: "A great pleasure in life is doing what others say you can't."

Walker proposes to make a 10-meter (33-foot) telescope from a balloon tucked inside a larger carrier balloon and floated into near space from Antarctica. He hopes the fortune is prophetic.

So far, so good. In 2012, NASA gave him $200,000 to flesh out his proposal.

On Thursday, it awarded him up to $500,000 to develop and fly a prototype. He estimates a fully developed 10-Meter Sub-Orbital Large Balloon Reflector would cost about $8 million.

His is one of five projects remaining from the original 450 entries in the 2012 round of what are colloquially called the "sci-fi" awards, through which NASA encourages novel, risky ideas.

Walker said the ideas "can't be too crazy, but they also can't be too sane."

Tom Prettyman, senior scientist with Tucson-based Planetary Science Institute, also advanced to the second round of the sci-fi awards, known officially as the NASA Innovative Advanced Concepts Program.

Prettyman proposes to build a muon detector for a future space mission that would allow scientists to perform an outer-space "CT scan" of asteroids, comets, or the subsurface of planets.

Muons are fundamental particles that are plentiful on Earth and can penetrate "through a kilometer of rock," Prettyman said.

They were used by physicists and archaeologists in the '70s to search the great pyramids of Egypt for hidden chambers and more recently to detect rising magma in volcanoes.

Prettyman thinks he can find enough muons in space and create a space-borne detector that would be valuable in a future space mission.

"It's exciting," said Prettyman, who said he met Walker at a symposium where some of the initial proposals were presented.

"There were just a gaggle of different ideas from all over the place -- architects wanting to build space colonies and somebody proposing an induced coma for travel to Mars."

Walker said the scientific payoff would be huge for his plan to place a large telescope and a terahertz detector above most of Earth's atmosphere to look, at first, for water vapor in the cosmos.

Terahertz astronomy explores the millimeter and submillimeter wavelengths of light between infrared and microwaves.

He would be looking specifically at 557 gigahertz for the signature of water vapor -- something that is impossible if peering through atmosphere, even in the dry air of Antarctica.

NASA developed the technology that allows him to fill 700 pounds of thin-film polyethylene with 17 million cubic feet of helium to act as a carrier balloon.

Walker has been floating high-tech gadgets from such balloons for the past 20 years.

What's new is Walker's concept of a balloon within a balloon.

His interior balloon, 20 meters in diameter, would have an aluminized, spherical portion 10 meters wide that would act as the telescope mirror.

It would sit inside the top of the carrier balloon, which would act as a protective radome, and also keep the mirror steady.

A 1-meter correcting mirror, needed in case the balloon does not inflate evenly, would focus light onto his detector.

It would be launched from the South Pole, climb to an altitude of 120,000 feet and float there, pushed by a dependable arctic vortex that would allow it to inscribe a circular pattern, returning to its starting position every 14 days.

After 100 days of gathering data, the telescope and supporting gantry would detach and float back to Earth on parachutes.

The carrier balloon expands crazily in the thin atmosphere to 100 meters in diameter, making its polyethylene skin 97 to 98 percent transparent -- good enough for the kind of astronomy Walker conducts.

It's also easy to correct the image at those wavelengths. "Our wavelengths are so long, our corrections are trivial," Walker said.

In an optical telescope, an adaptive mirror needs to make 1,000 corrections a second.

At Walker's wavelengths, "We're talking millimeters in an hour. You could do this with ropes and pulleys."

Steward Observatory director Buell Jannuzi calls Walker one of the founders of terahertz astronomy. He has built receivers for most of his 40-year career, including ones for the South Pole and the Heinrich Hertz Submillimeter Telescope on Mount Graham.

The balloon flights Walker usually does are of 14-day duration. "We call that a long-duration balloon," he said. This project would rely on a super-pressurized helium balloon that NASA has developed -- leading to an "ultra-long duration" balloon flight of 100 days or even more.

The goal in this second round is to build a half-sized prototype for a 12-hour flight from Fort Sumner, N.M.

Walker notes that the location is only 30 minutes from Roswell, N.M. -- home to an array of alien visitation theories.

Where better to test out a sci-fi proposal?

Contact reporter Tom Beal at tbeal@tucson.com or 573-4158.

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(c)2014 The Arizona Daily Star (Tucson, Ariz.)

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Source: Arizona Daily Star (Tucson)


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