Satellites on a Budget - High Altitude Balloons
Written by Nancy Atkinson
Balloon photograph taken from 25km. Image credit: Paul Verhage. Click to enlarge.
Paul Verhage has some pictures that you'd swear were taken from space. And they were. But Verhage is not an astronaut, nor does he work for NASA or any company that has satellites orbiting Earth. He is a teacher in the Boise, Idaho school district. His hobby, however, is out of this world.
Verhage is one of about 200 people across the United States who launch and recover what have been called a "poor man's satellite." Amateur Radio High Altitude Ballooning (ARHAB) allows individuals to launch functioning satellites to "near space," at a fraction of the cost of traditional rocket launch vehicles.
Usually, the cost to launch anything into space on regular rockets is quite high, reaching thousands of dollars per pound. Additionally, the waiting period for payloads to be put on a manifest and then launched can be several years.
Verhage says that the total cost for building, launching and recovering these Near Spacecraft is less than $1,000. "Our launch vehicles and fuel are latex weather balloons and helium," he said.
Plus, once an individual or small group begins designing a Near Spacecraft, it could be ready for launch within six to twelve months.
Verhage has launched about 50 balloons since 1996. Payloads on his Near Spacecraft include mini-weather stations, Geiger counters and cameras.
Near space lies begins between 60,000 and 75,000 feet (~ 18 to 23 km) and continues to 62.5 miles (100km), where space begins.
"At these altitudes, air pressure is only 1% of that at ground level, and air temperatures are approximately -60 degrees F," he said. "These conditions are closer to the surface of Mars than to the surface of Earth."
Verhage also said that because of the low air pressure, the air is too thin to refract or scatter sunlight. Therefore, the sky is black rather than blue. So, what is seen at these altitudes is very close to what the shuttle astronauts see from orbit.
Verhage said his highest flight reached an altitude of 114,600 feet (35 km), and his lowest went only 8 feet (2.4 meters) off the ground.
The main parts of a Near Spacecraft are flight computers, an airframe, and a recovery system. All these components are reusable for multiple flights. "Think of building this Near Spacecraft as building your own reusable Space Shuttle," said Verhage.
The avionics operates experiments, collects data, and determines the status of the spacecraft, and Verhage makes his own flight computers. The airframe is usually the most inexpensive part of the spacecraft and can be made from materials such as Styrofoam and Ripstop Nylon, put together with hot glue.
The recovery system consists of a GPS, a radio receiver such as a ham radio, and a laptop with GPS software. Additionally, and probably most important is the Chase Crew. "It's like a road rally," says Verhage, "but no one in the Chase Crew knows quite for sure where they are going to end up!"
The process of launching a Near Spacecraft involves getting the capsule ready, filling the balloon with helium and releasing it. Ascent rates for the balloons vary for each flight but are typically between 1000 and 1200 feet per minute, with the flights taking 2-3 hours to reach apogee. A filled balloon is about 7 feet tall and 6 feet wide. They expand in size as the balloon ascends, and at maximum altitude can be over 20 feet wide.
The flight ends when the balloon bursts from the reduced atmospheric pressure. To ensure a good landing, a parachute is pre-deployed before launch. A Near Spacecraft will free fall, with speeds of over 6,000 feet per minute until about 50,000 feet in altitude, where the air is dense enough to slow the capsule.
The GPS receiver that Verhage uses signals its position every 60 seconds, so after the spacecraft lands, Verhage and his team usually know where the spacecraft is, but recovering it is mostly a matter of being able to get to where it lies. Verhage has lost only one capsule. The batteries died during the flight, so the GPS wasn't functioning. Another capsule was recovered 815 days after launch, found by the Air National Guard near a bombing range.
Some balloons are recovered only 10 miles from the launch site, while others have traveled over 150 miles away.
"Some of the recoveries are easy," said Verhage. "In one flight, one of my chase crew, Dan Miller, caught the balloon as it landed. But some recoveries in Idaho are tough. We've spent hours climbing a mountain in some cases."
Other experiments that Verhage has flown include a Visible Light Photometer, Medium Bandwidth Photometers, an Infrared Radiometer, a Glider Drop, Insect Survival, and Bacteria Exposure.
One of Verhage's most interesting experiments involved using a Geiger counter to measure cosmic radiation. On the ground, a Geiger counter detects about 4 cosmic rays a minute. At 62,000 the count goes to 800 counts per minute, but Verhage discovered that above that altitude the count does down. "I learned about primary cosmic rays from that discovery," he said.
Flying the experiments are a great experience, Verhage said, but launching a camera and getting pictures from Near Space provides an irreplaceable "wow" factor. "To have an image of the Earth showing its curvature is pretty amazing," Verhage said.
"For cameras," he continued, "the dumber they are the better. Too many of the newer cameras have a power save feature, so they shut off when they're not used in so many minutes. When they turn off at 50,000 feet, there's nothing I can do to turn them back on."
While digital cameras are easy to interface with the flight computer, Verhage said, they require some inventive wiring too keep the camera from shutting off. He said that so far, his best photos have come from film cameras.
Verhage is writing an e-book that details how to build, launch and recover a Near Spacecraft, and the first 8 chapters are available free, online. The e-book will have 15 chapters when finished, totaling about 800 pages in length.
Parallax, the company that manufactures a microcontroller is sponsoring the e-book's publication.
Verhage teaches electronics at the Dehryl A. Dennis Professional Technical Center in Boise. He writes a bimonthly column about his adventures with ARHAB for Nuts and Volts magazine, and also shares his enthusiasm for space exploration through the NASA/JPL Solar System Ambassador program.
Verhage said his hobby incorporates everything he is interested in: GPS, microcontrollers and space exploration, and he encourages anyone to experience the thrill of sending a spacecraft to Near Space.
Filed under: Earth Observation
February 8th, 2008 at 6:00 pm
The link on the page:
http://www.universetoday.com/2006/01/20/satellites-on-a-budget-high-altitude-balloons/
to the "first 8 chapters" is broken.
The correct link is now:
http://www.parallax.com/tabid/567/Default.aspx
-J
June 14th, 2008 at 2:06 am
Great pictures. Very interesting.