Prepping for drone exploration of Mars
WASHINGTON, D.C. — The earliest missions to Mars gathered data while flying by or orbiting the Red Planet. Then came missions with landers and rovers. One day, expeditions — whether carrying a human crew or not — may scout the planet using some sort of aerial drone. And 12-year old James Fagan, who attends the Riverside Virtual School in Riverside, Calif., is getting ready for that. He’s already built a simple wind tunnel to test vehicles being designed to fly on Mars.
No one is sure what such a drone might look like. It might be some small, aircraft-like probe with wings and a propeller. Or it might be some helicopter-like device propelled by several rotors. Whatever the design, engineers will need to test any of these under realistic conditions before they ship them off to the Red Planet. In particular, researchers need to show they will be able to stay aloft in Mars’ cold, thin atmosphere. The best way to test that would be using a wind tunnel.
Such a facility is typically large and expensive. But the one that James built isn’t. His fits on a home workbench. The young engineer showed off his design here, last month, at the eighth annual Broadcom MASTERS competition. This event brings together 30 U.S. middle-school students, each year, to tackle team challenges. (MASTERS stands for Math, Applied Science, Technology and Engineering for Rising Stars.) The program was created by Society for Science & the Public, which publishes Science News for Students and this blog. Broadcom Foundation, headquartered in Irvine, Calif., sponsors the event.
Unlike most science competitions, only about one-fifth of a finalist’s overall score is based on the qualifying research that he or she had entered at a science fair the previous year. The rest of the contestants’ scores come from the creativity they showed and how well they worked as part of a team.
Thar she blows
Engineers and designers often use wind tunnels to analyze the flow of air around scale models of vehicles. This lets them measure how streamlined those objects are. That, in turn, can help people estimate how well a plane or missile might fly. It also can help gauge what sort of gas mileage a car or helicopter might get.
James wants to become an aerospace engineer. And he’s always been interested in Mars. Two years ago, he made it to the Broadcom MASTERS finals. His project that year tried to figure out what type of wing design might provide the greatest lift in Martian air. James was one of two 2016 contestants to win “Rising Stars” awards. This year, James built a wind tunnel that could help test and verify such wing designs.
Most wind tunnels have a flow-through design. They draw air in one end of the tunnel and send it out the other. But to simulate Mars, James’ wind tunnel needed to be different. Air pressure at the surface of the Red Planet is only about 1 percent as high as at sea level on Earth. Also, the air contains different gases. On Earth, more than 99 percent of the air is made up of nitrogen and oxygen. On Mars, about 96 percent of the air is carbon dioxide, or CO2. (That gas makes up only 0.04 percent of the air on Earth.)
To make sure he could maintain Mars-like conditions inside his wind tunnel, James built a closed system. He can seal its big set of pipes off from Earth’s atmosphere. Whenever he runs a test, he uses pumps to suck all of the air from his tunnel. Then, he adds back a small bit of CO2 until the pressure inside his tunnel matches the conditions on Mars. A small fan pulls the CO2 through the test section of his wind tunnel. This is where he tests small-scale models of wings and such.
“It’s a fascinating prospect that I’m able to simulate the Martian atmosphere in my tunnel,” says James.
He crafted his tunnel using PVC (polyvinyl chloride) pipes and fittings that he bought at a home improvement store. Most of the parts are about 7.6 centimeters (3 inches) in diameter. The pipes’ walls are about 0.5 centimeter (0.2 inch) thick. That’s a good thing: If the walls were thinner, James notes, the greater pressure of Earth’s atmosphere outside of them might crush the pipes.
James encountered a few surprises. For instance, the fan driving air through the tunnel spun at 23,000 revolutions per minute (rpm) during trials that used Earth-like conditions. But when James ran tests that simulated Mars inside the tunnel, the fan spun a whopping 39 percent faster. That’s likely due to the lower air pressure during those tests, he now suspects.
For a full-sized Martian drone, these test results could be good news, James says. For instance, a drone might be able to fly on Mars with a much smaller battery than would be needed on Earth. Or, the drone’s scouting missions might cover a broader area without needed extra fuel.
aerial Of or taking place in the air.
aerospace A research field devoted to the study of Earth’s atmosphere and the space beyond or to aircraft that travel in the atmosphere and space.
air pressure The force exerted by the weight of air molecules.
annual Adjective for something that happens every year.
atmosphere The envelope of gases surrounding Earth or another planet.
battery A device that can convert chemical energy into electrical energy.
Broadcom MASTERS Created in 2011 by the Society for Science & the Public, Broadcom MASTERS (Math, Applied Science, Technology and Engineering Rising Stars) is the premier middle school science and engineering fair competition. Broadcom MASTERS International gives select middle school students from around the world a unique opportunity to attend the Intel International Science & Engineering Fair.
carbon The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.
carbon dioxide (or CO2) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas). Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.
diameter The length of a straight line that runs through the center of a circle or spherical object, starting at the edge on one side and ending at the edge on the far side.
drone A remote-controlled, pilotless aircraft or missile.
engineer A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.
expedition A journey (usually relatively long or over a great distance) that a group of people take for some defined purpose, such as to map a region’s plant life or to study the local microclimate.
gauge A device to measure the size or volume of something. For instance, tide gauges track the ever-changing height of coastal water levels throughout the day. Or any system or event that can be used to estimate the size or magnitude of something else. (v. to gauge) The act of measuring or estimating the size of something.
lander A special, small vehicle designed to ferry humans or scientific equipment between a spacecraft and the celestial body they will explore.
lift An upward force on an object. It may occur when an object (such as a balloon) is filled with a gas that weighs less than air; it can also result when a low-pressure area occurs above an object (such as an airplane wing).
Mars The fourth planet from the sun, just one planet out from Earth. Like Earth, it has seasons and moisture. But its diameter is only about half as big as Earth’s.
model A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes. Or an individual that is meant to display how something would work in or look on others.
nitrogen A colorless, odorless and nonreactive gaseous element that forms about 78 percent of Earth's atmosphere. Its scientific symbol is N. Nitrogen is released in the form of nitrogen oxides as fossil fuels burn.
oxygen A gas that makes up about 21 percent of Earth's atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).
polyvinyl chloride (PVC) This is a plastic formed by using heat to turn a liquid resin into a solid. The plastic can be soft and flexible or rigid and hard. The raw ingredients consist primarily of chlorine and carbon.
pressure Force applied uniformly over a surface, measured as force per unit of area.
Red Planet A nickname for Mars.
sea level The overall level of the ocean over the entire globe when all tides and other short-term changes are averaged out.
simulate To deceive in some way by imitating the form or function of something. A simulated dietary fat, for instance, may deceive the mouth that it has tasted a real fat because it has the same feel on the tongue — without having any calories. A simulated sense of touch may fool the brain into thinking a finger has touched something even though a hand may no longer exists and has been replaced by a synthetic limb. (in computing) To try and imitate the conditions, functions or appearance of something. Computer programs that do this are referred to as simulations.
verify (n. verification) To demonstrate or confirm in some way that a particular claim or suspicion is true.
wind tunnel A facility used to study the effects of air moving past solid objects, which often are scale models of real-size items such as airplanes and rockets. The objects typically are covered with sensors that measure aerodynamic forces like lift and drag. Also, sometimes engineers inject tiny streams of smoke into the wind tunnel so that airflow past the object is made visible.