Rice: Balloons also have a scientific purpose
Posted May 21, 2015
Raleigh, N.C. — Ballooning dates as far back as the 3rd Century B.C.
Lightweight bamboo frames covered by rice paper were lifted by candles in China, which generated both heat and light and were used as military signals.
It would be several hundred years until balloons carried humans into the air. The first tethered balloon flight with humans happened in October 1783. The Montgolfier brothers used their observations of rising ash in paper fires at their family paper business to create a hot air-filled paper and silk envelope large enough to lift a circular platform holding two men. The first free flight of their balloon took place Nov. 21, 1783 in Paris, France.
Today’s balloons do much more than those on display at this weekend’s WRAL Freedom Balloon Fest.
Balloons are a great platform for science. They provide low-cost access to near space - above 99.5 percent of the Earth’s atmosphere. Balloon-borne telescopes date back to the late 1950s and have conducted studies across the electromagnetic spectrum, including visible light and x-rays as well as examining the magnetic field surrounding the planet. Balloons also enable testing and calibration of new instruments before they are introduced into far more expensive and far less accessible space systems.
The largest research balloons can lift a payload up to 8,000 pounds and remain at an altitude of 26 miles above the ground for up to two weeks. The newest Ultra Long Duration Balloons (ULDB) and Super Pressure Balloons (SPB) use 22 acres of material inside pumpkin shaped, football stadium sized designs to achieve flights of more than three months. These balloons float along with the moving air in the upper atmosphere and can circumnavigate the globe. Data is gathered by satellites in low Earth orbit and returned to researchers on the ground.
The Wallops Flight Facility in Virginia manages NASA’s scientific balloon program, which consists of 10-15 flights each year from launch sites worldwide. The next launch is scheduled for June when the Low-Density Supersonic Decelerator (LDSD) will be tested from an altitude of about 120,000 feet. LDSD is a technology being developed to inexpensively decelerate high speed spacecraft during atmospheric entry. This technology is critical to future robotic missions to Mars and the long term goal to put humans on the red planet, which require even more massive payloads than even the one-ton Curiosity rover, which landed on Mars in August 2012. LDSD is a lightweight system inspired by the Hawaiian Puffer Fish to increase its size without adding mass and inflation.
Amateurs have gotten into ballooning as well. NC Near Space Research has launched 39 chloroprene balloons, similar to weather balloons, since 2010. Each balloon carried cameras, tracking systems and something extra like a lego minifigure. Images captured from the balloons clearly show the Earth’s curvature and the thin atmosphere enveloping it.
Amateur Radio High Altitude Ballooning groups hold the seventh highest altitude at 142,022 feet. Most recently, the team lifted a small Styrofoam glider to put the claim “flies over 150 feet” to the test. The glider was dropped from nearly 60,000 feet and began descending at 125 miles per hour. Wings provided little lift in the thin atmosphere at that altitude. By 10,000 feet, the little plane settled out at about 20 mph as the column of air above was sufficient to pack down the air and let the wings do their job.
Weather balloons are released twice a day from locations around the world every day. About 100 of these sites are in the United States and have been managed by the National Weather Service since the 1930s. WRAL meteorologists fine tune their forecasts, especially during winter weather, based on information from balloons released in Greensboro at 6 a.m. and 6 p.m.
Data gathered by these balloons provide input to computer-based weather prediction models, climate research, air pollution models and real time information that is invaluable to aviation, fire and marine forecasts. This ground-truth data is also used to validate satellite data. As the father of modern rocket science, Wernher von Braun once said: “One good test is worth a thousand expert opinions.”
Weather balloons are inflated with hydrogen to about five feet in diameter and a radiosonde - an expendable instrument package with battery powered pressure, temperature and relative humidity sensors - is attached. The balloon travels about 1,000 feet per second as it continuously rises and sending measurements to the ground. GPS tracking of the package reveals wind direction and speed through the layers of the atmosphere. About 2 hours later, the balloon has expanded to up to five times in size in the lower pressure of the atmosphere and bursts. The radiosonde returns gently to Earth on a small orange parachute.
If you find a radiosonde, they aren't dangerous. Do your part to make the best use of your tax dollars. Follow the instructions printed on the side and return it to National Weather Service where they can be reconditioned and reused. Less than 20% radiosondes of the more than 75,000 released each year make their way back to the NWS.
While the balloons hovering over Wake County this weekend are made from brightly colored materials like nylon or polyester, balloons used in scientific programs are constructed in drab grays and silvers from polyethylene film just 0.8 millimeter thick, or about as thick as kitchen plastic wrap. Weather balloons are made of latex or neoprene, a synthetic rubber in similarly boring colors, usually an off-white or tan color.