The Next 100 Years: Current research at WPI is helping shape the future of flight
Project: Growing Plants in Low Gravity
The Challenge: How do you feed people on long-term space flights, on space stations, or on planetary or lunar bases? “You can’t possibly bring enough food with you,” says Pam Weathers, professor of biology and biotechnology. Her mist-based irrigation system could meet the challenge of growing healthy, productive plants in space.
Funding Source: In 2002, WPI invested $37,000 to renovate Weathers’ lab. After pledging $500,000, NASA, unfortunately, changed its priorities and pulled out of the project.
The Science: Low-gravity conditions, like those in space flight, disrupt the movement of gases in liquids. On the Mir Space Station, for example, plant roots suffered from a lack of oxygen. This resulted in unhealthy plants that were unable to complete their life cycles: they couldn’t flower, develop fruits or vegetables, or produce viable seeds.
Through a series of prior experiments, Weathers and colleagues had designed and built a nutrient mist bioreactor. This inexpensive system sprays water and nutrients onto plant roots. The mist droplets measure just 7-10 microns in diameter—100 droplets would fit on the head of a pin.
Weathers and biology grad student Joseph Romagnano ’01 (M.S. ’04) planted pea seeds in clear plastic rain gutters, in a kitty litter-like substance, called Turface, which traps the water and nutrient mist for the roots to absorb. The source of gases—oxygen and carbon dioxide—was a perforated tube that ran along the bottom of the box. Mist was fed into one end.
Results: At the end of seven days, roots of germinated pea plants had grown in the Turface. After analyzing the roots and the oxygen, carbon dioxide and ethylene present around the roots, Weathers found that peas indeed grew better in the mist. Current 40-day experiments will determine how well the peas grow to maturity, hopefully producing viable seeds.
Roadblocks: NASA’s retraction of funding has all but halted Weathers’ research for now.
The Promise: Future generations may one day pick lettuce and peas in Martian greenhouses. When new funding comes through, Weathers will extend her work to include a number of other crops chosen by NASA for space farming purposes. The next step is to launch a rocket and grow dwarf peas, lettuce and wheat in space.
Project: Aerodynamics of Parachute Inflation
The Challenge: Invented more than 200 years ago, the seemingly simple parachute involves complex physics. Hamid Johari, professor of mechanical engineering, is improving modeling software to help the Army develop newer designs that will lessen the shock of inflation, slow down descent speeds, reduce unwanted oscillations, and enable precision in landings.
Funding Source: The Army Research Office (ARO) provided $186,000 from 1998 to 2001. A grant modification of $63,500 was made to carry the research through 2002, and Johari anticipates approval of another three-year grant that would begin soon.
The Science: To study the aerodynamics of canopy inflation, Johari needed to slow the action to make detailed, accurate measurements. His solution: place small-model parachutes in a 30-foot-long water tunnel.
Measurements are made using lasers, digital cameras and the Particle Image Velocimetry (PIV) technique. The resulting high fidelity data provides simultaneous measurements at many spatial points. Using PIV, Johari “seeds” the water tunnel, or flow field, with tiny, hollow glass spheres coated with silver. Every few milliseconds, as the seeded water flows past the parachute, Johari flashes laser light onto the field and takes a digital photo. The images look like a glass snow-globe, with the lit particles showing clear patterns around the parachute. “From the displacement of the particles you can figure out the flow dynamics,” Johari explains.
Results: Johari has found that, contrary to common wisdom, a parachute’s opening shock—the highest force on the canopy as it opens—occurs due to the rapidly changing flow features around the canopy, rather than the enlargement of the canopy volume. He has also discovered a new vortex-shedding frequency around the canopy—swirling pockets of air that roll off the canopy as it descends. These findings will guide new designs to reduce opening shock and to make a parachute’s descent more predictable.
Roadblocks: Johari’s small lab precludes testing larger model canopies in bigger water tunnels, to more closely mimic real-life situations.
The Promise: The humble parachute is expanding its role in delivering humanitarian aid in remote areas. As the Army develops its modeling tools, parachute design costs will drop significantly, resulting in safer, more accurate parachutes. Says Johari, “You’ll be able to pinpoint where you want the package to land, and you’ll be able to make the drops at any time of the day or night, in places with no roads or runways.”
Project: Spacecraft propulsion
The Challenge: Design smaller engines for ever-shrinking spacecraft. Nikos A. Gatsonis, associate professor of mechanical engineering and director of WPI’s Aerospace Program, is developing micro and nano on-board engines, or thrusters. These devices must allow for delicate maneuvers, such as those required when aligning constellations of satellites. The thrusters must be positioned so that their spent fuel (or plumes) won’t contaminate the spacecraft’s surfaces and instruments, or interfere with its communications.
Funding Sources: NASA’s Glenn Research Center, the Air Force Office of Scientific Research (for modeling electric micro-propulsion), the Johns Hopkins University Applied Physics Laboratory (JHUAPL), and the National Science Foundation (for outstanding issues related to modeling nano-sized flows) have together supplied in excess of $1.3 million for the project.
The Science: Gatsonis’ experiments study interactions of plumes with spacecraft. He develops computational models that help determine where to place the thrusters on the craft and he studies thruster fuel flow in order to improve performance.
Gatsonis recently participated in the Active Plasma Experiment (APEX) North Star mission led by JHUAPL. The team flew a sounding rocket equipped with diagnostic instruments through artificially induced, high-speed plasma plumes similar to those produced by on-board electric propulsion thrusters.
The next generation of propulsion systems will be made at the nanoscale. Gatsonis is developing models that examine liquid and gaseous flows in nanotubes—structures about the size of a virus.
Results: The Glenn Research Center used Gatsonis’ research to design an improved electric micropropulsion device. The device, called a pulsed plasma thruster (PPT), measures just one square inch and uses solid Teflon for fuel.
Roadblocks: Traditional methods break down when analyzing propellant flows in ever-smaller propulsion devices. Ionized gases and electromagnetic fields in the devices also complicate matters. The lack of nano-sized sensors hampers exploring the structure of flow-fields in such diminutive domains.
The Promise: Future spacecraft may be apple-sized, with on-board propulsion and other fluidic systems measuring as big as a red cell, or even a virus. They will be capable of independent analysis and decision making. “The more we work in this area, the more we imitate biological systems. We will eventually build spacecraft that can think for themselves and incorporate fluidic systems at the nanoscale” says Gatsonis.
The Outer Limits of Satellites
Project: University Nanosat Competition
The Challenge: Design a satellite the size of a basketball.
Fred Looft, professor and department head of electrical and computer engineering, oversees an undergraduate team that’s participating in a competition sponsored in part by the Air Force Office of Scientific Research (AFOSR).
Funding Sources: AFOSR has provided $100,000 over 2 years.
The Science: Student groups pool knowledge to build the nanosats. One team tackles the exterior structure: the metal, frame, solar cells, and other “packaging” that must survive the trauma of the launch and the harsh conditions of space. Another team designs, implements and tests all power-related systems, like circuitry and batteries. The communication group works on radio frequency transmission and reception, including the receiver, transmitter, cabling, antenna and networks.
Results: The competition will be judged in the spring of 2005.
Roadblocks: Several competitors are universities with full staffs and an established infrastructure. “It’s tough to catch up with folks who already have programs in place,” says Looft, “but we are doing a great job and expect to do very well in the competition.”
The Promise: In a distant galaxy, swarms of intelligent microsatellites converge on an asteroid belt. One of the many survivors spots an asteroid with characteristics it “knows” are needed for research. It calls to several of its baseball-sized buddies to fly over and take pictures from various angles, and together they beam their images back to Earth.
The Smallest Airplanes
Project: Micro Air Vehicles or Biologically Inspired Flight
The Challenge: Micro Aerial Vehicles (MAVs) equipped with cameras and sensing equipment would be useful in unmanned planetary explorations, investigating disasters on Earth, and for battlefield reconnaissance. But how to build viable aircraft as small as a sparrow or a bee? “As you build smaller, you need aircraft that either move awfully fast, or with flapping wings,” says David Olinger, associate professor of mechanical engineering.
Funding Source: The NASA Space Grant Consortium provides $10,000 a year for the undergraduate side of Olinger’s MAV work. Olinger will apply for additional funding from DARPA (the federal Defense Advanced Research Projects Agency) to support graduate research.
The Science: In what he refers to as “biologically inspired flight,” Olinger and grad students Sagar Sathaye and Ian DeBarros are studying pheasant and seagull wings to determine the best model for their next generation of planes. They won’t have flapping wings, but may feature other bird-like attributes. Olinger is focusing on a triangular notch in the middle rear of birds’ outstretched wings. Biologists say the notches provide more lift, less drag.
“We’re asking why that’s true and whether we should notch our MAV wings,” Olinger says. The scientists place prototype wings, with and without the bird-inspired notch, of lightweight plastic in a state-of-the-art, closed-end wind tunnel. Air pressure is measured along every inch of the wing’s curved top.
Results: Olinger’s undergraduate students have entered their pheasant-sized propeller-driven, electric-powered MAVs into an annual competition at the University of Florida for the past three years. Prizes are awarded for the smallest aircraft that can fly specific distances and can relay certain images visible only from the air back to the students. In 2001, their first year in the contest, Olinger’s students placed fourth.
Roadblocks: Olinger needs to gather more data that will tell him whether to build MAVs with notches, or with another borrowed-from-bird feature. As the MAVs become smaller, new instruments will be needed to measure forces and pressures on the wings.
The Promise: An unmanned spacecraft lands on a distant planet. Within minutes, hundreds of aircraft the size of hummingbirds disperse across the planet’s dark landscape, wings buzzing, cameras recording images, sensing equipment measuring chemical compounds, flashing data back to Earth. On a battlefield, a soldier lifts a bird-sized plane from her knapsack and sends it to the frontline, where it relays live images back to her. In the midst of a flood, rescuers launch their MAVs to find out where help is most desperately needed. Olinger predicts that the next generation of MAV, the sparrow-sized models, will be built within a year or two. “They will get smaller quickly,” he says. “Two years later, they’ll be half that size.”
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Last modified: Aug 31, 2004, 17:07 EDT