From the archives: NASA sends drone to the ozone layer

To mark our a hundred and fiftieth 12 months, we’re revisiting the Standard Science tales (each hits and misses) that helped outline scientific progress, understanding, and innovation—with an added trace of recent context. Discover the Notable pages and take a look at all our anniversary protection right here.

Thirty years in the past, the noxious clouds of chlorofluorocarbons that had been gathering in Earth’s stratosphere for half a century would chew a seasonal gap within the protecting ozone layer over Antarctica twice the diameter of Pluto. Whereas the Antarctic function was excessive, it underscored a catastrophe unfolding throughout Earth’s ambiance. With much less ozone within the stratosphere to protect wildlife from the solar’s ultraviolet rays, crops would undergo and pores and skin most cancers would soar. 

By the point Standard Science ran a function in July 1992 describing the pressing efforts of scientists throughout the globe to know the dynamics of ozone destruction, our outlook was dire. “Earth’s ozone protect appears to be failing,” wrote Standard Science Senior Editor Steven Ashley, “and researchers want to seek out out why—quick.” In response to Ashley NASA had pulled out all of the stops, constructing a robotic data-gathering drone to ply Earth’s polar vortex—the higher reaches of the ambiance over Antarctica. The craft, known as Perseus, used GPS and a programmed route to smell out ozone. 

 In 1987, each nation on Earth (a primary and solely) ratified a treaty to reverse the harm. The Montreal Protocol established pointers to quickly section out an inventory of 100 manufactured chemical compounds known as ozone depleting substances or ODS. Since Standard Science’s function ran in 1992, ODS emissions have been diminished by 98 %. And whereas the Antarctic ozone gap fluctuates in dimension and severity 12 months to 12 months, pushed by myriad elements together with seasonal temps and moisture, an enhancing pattern has been constant. Consultants forecast full restoration by 2070. Apart from representing a uncommon environmental success story, there’s a lesson in ozone: Wonderful issues are attainable—even on a planetary scale—when everybody will get on board.

Sadly, such unity has proved elusive for greenhouse gasses. Since 1992, world leaders have taken three swings at treaties to scale back the substances, the newest being the Paris Local weather Settlement. None have achieved unanimity, though the Paris Settlement is shut now that the US has rejoined.

“Ozone Drone” (Steven Ashley, July 1992)

The rupture of Earth’s ozone protect has change into a worldwide concern. However how can scientists achieve the high-altitude knowledge they should discover options? This unmanned energy glider could be the reply.

Eighty thousand ft above Antarctica’s huge frozen expanse, a lone plane will cruise the stratosphere on lengthy, tapered wings. The unmanned powered glider, known as Perseus, is predicted in 1994 to fly increased than any earlier prop airplane to seek out out what’s gone mistaken with Earth’s stratospheric ozone protect. It is going to be programmed to look the chilly, skinny air over Antarctica for ozone-killing chemical compounds and produce again essential air samples which have eluded atmospheric scientists for years.

The airplane’s 14.4-foot, variable-pitch propeller—so lengthy that it’s unable to spin till Perseus is aloft—would require the robotic craft to be hawed into the air from its base at Antarctica’s McMurdo Station by a winch-wound cable. As soon as airborne, its engine will likely be engaged and the cable indifferent.

Perseus will then spiral upward towards the middle of the ozone gap at about 40 knots, reaching a velocity of 200 knots at altitude. Though a technician will pilot the airplane remotely through line-of-sight radio controls when it’s close to the bottom, Perseus will largely pilot itself. Its on-board flight pc will carry preprogrammed navigation instructions based mostly on knowledge beamed from World Positioning Satellites.

In the end, it’s meant that sensors mounted within the craft’s nostril will reply if the high-flying probe enters a wispy, pinkish assemblage of tiny ice crystals, a suspected hotbed of ozone destruction researchers name a polar stratospheric cloud. The pc on-board will direct the craft’s air-sampling equipment to have interaction. When its sensors now not detect the ice, Perseus will reverse course and proceed to fly a zig-zag sample with a purpose to map the boundaries of the noxious cloud.

Whole flight period will likely be about six hours, with an hour for air sampling. Perseus can carry solely sufficient gas for the climb, so it’s going to glide silently, after the engine halts, to a touchdown at its base on the ice shelf.

Such a flight can not come too quickly for scientists learning ozone depletion. Earth’s ozone protect appears to be failing and researchers want to seek out out why—quick. Final October, NASA’s Nimbus-7 satellite tv for pc measured the bottom Focus of ozone over Antarctica in 13 years. This big ozone gap has to this point been restricted to the Southern Hemisphere, however NASA plane not too long ago discovered an abundance of ozone-hole precursor chemical compounds excessive within the arctic air, elevating the specter of a northern ozone gap. Maybe much more alarming is the invention of thinning ozone ranges over the northern mid-latitudes, together with populated areas of Canada and New England, Britain, France, and Scandinavia. (This previous 12 months’s circumstances have been unusually heat, say scientists, so no northern ozone gap materialized.)

Since 1988, pilots in NASNs ER-2 reconnaissance plane—transformed U-2 spy planes—have climbed 13 miles above the distant and desolate polar areas to assemble air samples for scientists. These missions are something however routine. If one of many single-engine airplanes have been to come across hassle throughout these arduous eight-hour, 1,500-mile nights, the solo pilot would virtually certainly die.

Up to now, the returns have been definitely worth the dangers, nonetheless, for the high-flying collectors have offered scientists with the proof they wanted to implicate man-made chlorine compounds known as chlorofluorocarbons (CFCs) in ozone’s destruction and name for his or her ban. Nonetheless, researchers’ means to additional mannequin and predict modifications within the ozone layer are presently restricted by a dearth of essential air samples from the center of the opening, which lies at altitudes past any piloted airplane’s ceiling, says Jim Anderson, atmospheric chemist at Harvard College. Anderson, additionally mission scientist for NASA’s six-month-long Airborne Arctic Stratospheric Experiment-2, says that present atmospheric fashions (used to information the federal government’s environmental coverage selections) lack info on chemistry and motion at altitudes close to 15 miles, or 82,000 feet-a essential space within the formation and destruction of ozone. “Satellites are good for broad-brush maps of easy measurements,” Anderson says, “however to know the ozone-depletion mechanism you want both-satellites for the climatological view and direct measurements by air automobiles to know the mechanism.”

Large helium-filled analysis balloons have been used for many years to haul devices to excessive altitudes, however these unwieldy craft are topic to the vagaries of the climate, resulting in launch delays and occasional misplaced payloads. And the one accessible airplane that may fly excessive sufficient is Lockheed’s SR-71 Blackbird, however the black plane’s supersonic velocity would make sampling unattainable. Perseus, then, would appear to be poised to supply many solutions.

Massachusetts Institute of Expertise-trained aeronautical engineer John Langford, president of Aurora Flight Sciences Corp. in Manassas, Va., is working to craft Perseus to supply excessive altitude functionality, pilotless operation, and the flexibility to hold scientific devices aloft at comparatively low value. The nucleus of the Aurora employees are veterans of the MIT Daedalus Undertaking, which developed the light-weight, human-powered plane that was pedaled 69 miles between the Greek isles Crete and Santorin [“88- pound Pedal Plane,” Feb. ‘87]. The event of Perseus owes lots to its seemingly easy forerunner.

Daedalus’ high-efficiency wings, designed by Mark Drela, affiliate professor of aeronautics and astronautics at MIT, stored the flimsy-looking composite craft airborne regardless of being pushed solely by its human engine. Langford and Drela knew that its lengthy, skinny wing form would work within the skinny air and excessive altitudes related to ozone sampling. “It was apparent that a lot of the airfoil and buildings expertise could be relevant to excessive· flying plane,” Drela remembers.

The necessity for a low-cost, high-altitude, unmanned platform for in situ atmospheric analysis was established just a few years in the past by a panel of specialists from NASA, the Nationwide Oceanic and Atmospheric Administration, and the Nationwide Science Basis. Apart from ozone chemistry, the panel needed a automobile that would assist decide the position of clouds in international warming, examine a stratosphere/troposphere mixing phenomena for a brand new Division of Power examine on climatic change, discover the causes of extreme storms, and assess the influence of future supersonic airliner exhaust emissions [“The Next SST,” Feb. ‘91].

“The important thing level was that the automobile be accessible within the 1993-’94 timeframe,” remembers Jennifer Baer-Riedhart, mission supervisor of the ensuing Small Excessive-Altitude Science Plane program at NASA’s Ames-Dryden Flight Analysis Facility in Edwards, Calif. Aurora, already nicely on its approach to growing such a craft, was awarded a $2.25 million, two-year NASA contract to ship two Perseus planes.

To maintain prices down, Langford notes that the technique has been to switch off-the-shelf elements and present designs, quite than growing customized expertise.

The result’s a light-weight 1,320 pound), “unmanned model of a sailplane,” Langford says, with a 59- foot wingspan and low-drag aerodynamic design. The wings, propeller, tail surfaces, and tail increase are molded from resin-impregnated Kevlar aramid fabric, Nomex honeycomb cores, and graphite fabric.

“Perseus’ composite construction is like that of a sport glider pushed to extremes,” says Siegfried Zerweckh, who has labored as chief of Aurora’s aerostructures group. “The truth that the airplane is unmanned and that its buildings don’t need to carry out endlessly like these of a business plane [that is, without an inspection following each flight] implies that we will push the supplies to the restrict.

“We use sandwich development for stiffness in virtually each half, together with the wings, tail surfaces, and tailboom,” Zerweckh continues. The three-piece, 30-foot wings, for instance, have solely 4 ribs supporting them within the span-wise route, 80 the structural sandwich panels should be largely self-supporting. A 19.7-foot· lengthy wing panel, as an example, weighs in at 170 kilos. The result’s a comparatively gentle construction.

An on-board flight management/navigation pc, a fly-by-wire digital management system, and an uncommon closed-cycle propulsion system full a lot of the airplane’s bulk. NASA thought Perseus’s propulsion system was essential sufficient to the success of the mission to fund it in a separate, half-million-dollar effort.

In line with Aurora’s penchant for classical monikers, the propulsion system for Perseus was dubbed Arion. It’s an uncommon closed-cyc1e system that features a liquid-cooled, 65-horsepower rotary Norton, a two-speed discount gearbox with provisions for clutching and locking the propeller, a stiff carbon-fiber drive shaft, the big, variable-pitch propeller, storage tanks for gasoline and liquid oxygen, and a big condenser to chill the exhaust.

A lot of that is the work of Martin Waide, former chief engineer for Aurora, who has been an engineer for Group Lotus in Britain and numerous American producers of navy remotely piloted automobiles.

A closed-cycle combustion engine system, which was chosen for Perseus as a result of it was most cost-effective and quickest to develop, derives from work achieved for torpedoes and submarines. As an alternative of compressing exterior air in a heavy, costly turbocharger to take care of energy, the engine exhaust is fed again into the consumption together with gas and oxygen. Senior propulsion engineer Stephen Hendrickson experiences that your complete engine complement was floor examined in Could—efficiently.

Burning the fuel-air combination produces exhaust temperatures of practically 2,000° Fahrenheit, which ordinarily could be dumped overboard. However as a result of Perseus’s exhaust will likely be recycled, giant radiators above the wing should carry off its warmth. The Aurora staff is growing giant stainless-steel and aluminum fin-and-tube-type warmth exchangers that can work at low atmospheric stress, the place warmth switch is gradual.

This previous November, the prototype Perseus A reached nowhere close to its excessive altitude objectives in its maiden flights over the El Mirage dry lake mattress in California’s Mojave Desert, restricted because it was to a 3,000-foot security ceiling. However the three quick take a look at flights offered knowledge that can pave the best way for high-flying missions two years therefore, when Perseus A will likely be airlifted in items to McMurdo Station. There, a floor crew of seven will rapidly assemble and put together the plane for launch.

Harvard’s Anderson designed the light-weight, nose-mounted instrument package deal that Perseus will carry. His 110-pound air sampling/evaluation system employs an optical ultraviolet-absorption method to measure ozone focus and a extra subtle photon-scattering equipment that measures the degrees of ozone-destroying precursor compounds in elements per trillion. In March, NASA balloon specialists accomplished a collection of inauspicious take a look at flights throughout which the miniaturized sensor package deal and its’ electronics survived -80°C temperatures after they have been lofted from the western coast of Greenland.

A broadly held idea reported not too long ago by Anderson and two colleagues spells out why monitoring these precursor compounds is so important.

It’s identified that unimpeded ultraviolet (UV) radiation may cause pores and skin most cancers, cataracts, disabled immune programs, in addition to disruptions of pure ecosystems and agriculture.

In winter when the solar leaves the poles, the stratospheric air quickly turns into so chilly that nitric acid trihydrate (NAT) within the air freezes. These tiny nitric acid crystals seed the formation of water-ice particles, which collect into wispy, pinkish clouds (the very clouds that Perseus’ detectors will likely be skilled on).

As quickly because the ice-nitric acid particles type, quick reactions involving hydrochloric acid and chlorine nitrate happen on the ice floor, which acts as a catalyst (see The Chlorine Connection). The previous is adsorbed onto the sides of the crystals, whereas collisions of the ice particles with the latter liberates molecular chlorine (C12). “No one anticipated that the ice surfaces would act as catalysts for the discharge of molecular chlorine,” Anderson says.

Whereas the polar air lots cool, they sink. As surrounding air flows in to take the chilly air’s place, the Coriolis Pressure—brought on by the spinning Earth—steers the in-rushing air into continent-size rotating jets. These polar vortices act as semi-impermeable partitions, isolating the air inside them. Regardless of the polar subsidence, the free molecular chlorine stays excessive up.

With the return of the spring daylight, just about all chlorine molecules break up into free chlorine radicals—chlorine atoms hungry to recombine. This chlorine feeds a collection of catalytic reactions that collectively destroy ozone.

“Free chlorine monoxide chews up ozone like Pac-Man,” Anderson notes. “On the concentrations we’ve observed-more than one half per billion by quantity, we estimate that 1 % of the ozone is misplaced every day.”

Later within the season, planetary-scale air waves pummel the polar vortices, breaking them up and replenishing the polar ozone. It’s thought that the arctic ozone gap has but to type as a result of the northern vortices are unstable resulting from close by mountain ranges.

A lot of scientists are conscious that sampling the stratosphere is important to discovering an answer to our ozone depletion issues. A number of different high-flying planes are deliberate. Already developed, however as but unused, is the enormous Condor pilotless plane, which was developed by the Boeing Co. of Seattle in a secret Protection Division mission. The 20,000-pound Condor is powered by 8 pair of liquid-cooled, 175-hp Teledyne Continental engines with two-stage turbocharging and intercooling driving three-bladed, 16-foot-long props. Although the reportedly $20 million craft accomplished eight take a look at flights in 1989, the federal government lacks the funds to function it. In a kind of flights, Boeing’s Condor set the world altitude document for propeller-driven plane at 67,028 ft. In one other, the categorised drone stayed aloft for 2 and a half days, flying an estimated 20,000 miles.

Different plane builders are taking the manned route. A German group from the Deutsche Forschungsanstalt fiir Luft and Rahrfahrt (DLR) in Oberpfaffenhafen has proposed improvement of a two-seat airplane known as Strato·2C that’s to be able to reaching 85,000 ft or flying for 10,000 miles. The composite plane is to be powered by twin 402-hp Teledyne Continental engines with turbochargers.

Aurora’s engineers are planning a number of spinoff variations of the Perseus “jeep” (as NASA phrases the following bigger dimension automobile). Fitted with an environment friendly turbocharged engine, Perseus B might cruise for a number of days at considerably decrease heights than the A mannequin to circle above hurricanes, as an example. With a 188-foot wingspan and twin pusher-prop energy vegetation, Theseus—a “van”-size craft —might fly a 440-pound payload at round 100,000 ft for a few month. Farther down the highway, the solar-powered Odysseus “truck” might cruise the stratosphere for so long as a 12 months with a 110·pound payload on board.

By working to increase flight period and elevation, these propeller-driven stratospheric cruisers might nicely come to behave practically as “poor man’s satellites.”

From the archives: NASA dispatches drone to help rescue the ozone layer
The duvet of the July 1992 particular challenge of Standard Science, specializing in the intersection of setting and expertise.

Some textual content has been edited to match up to date requirements and elegance.

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