What is believed to be the largest rocket ever built by university students roared from a launch platform in western Utah this past week, reaching an altitude of over three-quarters of a mile.
The "Unity IV" hybrid rocket blasted off about 2:20 p.m. Tuesday at the Utah Test and Training Range, an Air Force facility in the midst of Dugway Proving Ground in western Utah. The experimental rocket is 20 feet long and 17 inches in diameter and uses both solid fuel and a liquid oxidizer.
"It went up to 4,100 feet," said Paul Mueller, adjunct assistant professor at Utah State University's department of mechanical and aerospace engineering.
"We need to review the videos and the data to figure out how much thrust we had," Mueller added, but he thinks the rocket developed about 2,200 pounds of thrust.
While it reached a remarkable altitude, the rocket did not perform as well as expected, he added. "Our initial calculations said 10,000 feet and revised calculations said 7,000 feet," he said.
Also, a mechanical problem caused the parachute for the main rocket to become tangled, preventing the soft landing that the rocketeers hoped for. Instead, it came down hard, sticking upright in the ground.
Paul F. Eastman, professor in the mechanical engineering department at Brigham Young University, said about 60 students from the two universities participated in designing, building and flying the rocket. "This is an extracurricular project for most of these students," he said in a note to the Deseret Morning News.
The students "get a real-world engineering experience including coordinating efforts between projects at each university and meeting the safety requirements imposed by the Air Force to operate on the Utah Test and Training Range," Eastman added.
He expressed thanks for the help of the Air Force and Dugway Proving Ground, saying cost to a paying user of the range might have exceeded $100,000.
The range is an Air Force enclave in the midst of Dugway, located about 60 miles southeast of Wendover.
The military provided range supervision and use of tracking radar, long-range cameras, supervision and crews. The crews were there for fire, medical and recovery operations.
What made the rocket unusual is that it used solid fuel but liquid oxidizer, so it was a hybrid between solid and liquid-fuel rockets.
"A major advantage is safety and simplicity," said Mueller.
"It's much safer than a solid rocket motor, where all you need is an ignition source and it can ignite during transport or storage or whatever." Liquid-fuel rockets are more unwieldy.
When the rocket reached its peak, the nose cone separated and both parts parachuted to the ground. The main parachute became tangled, and the missile made a harder landing than expected, but the instrument package floated below its chute for about five minutes.
This was one of the most successful launches of the Unity IV program, which has been operating since the early 1990s. Its name derived from the four Utah universities originally involved. Since then, Weber State University left the program. The U. did not participate in the launch.
With improvements, a later generation of the hybrid rocket may reach 100,000 feet altitude, backers hope. Mueller said planners will try to reach that in "baby steps," improving the design as they go along.
"We believe . . . in terms of the length, diameter, weight thrust, this is the largest rocket that has been built and flown by university students," he added.
Boe Hadley, the Air Force's director of operations, said the launch went excellently, after about two hours of delay.
"Naturally, there were the initial problems of assembling the payload with the motor itself in the casing, but with a little fishing line and a little wire here and there, they put it together," he said.
"It was exciting to watch," Hadley added. "It had an excellent plume from the rocket motor."