If U.S. airlines had the same failure rate as the now-retired space shuttles, there’d be 272 fatal crashes a day.
As the investigation begins into the unmanned Orbital Sciences Corp. rocket that blew up seconds after liftoff this week, the history of space travel suggests such failures are neither rare nor unexpected.
“You have so much energy required to get out of the earth’s gravity field, you’re always essentially sitting on a bomb,” John Hansman, a professor of aeronautics and astronautics at the Massachusetts Institute of Technology, said in an interview. “You’re basically trying to have the bomb go off in a controlled way.”
Not only are rockets packed with explosive fuel, they are also complex machines made up of thousands of moving parts that can fail spectacularly over even a modest hiccup. It takes years to understand how systems may fail and where vulnerabilities lie, making it even more difficult to reduce risks as private companies get into the business of providing “space taxis” shuttling travelers and supplies into orbit.
Companies such as Virgin Galactic will have to address such risks before selling tickets to space travelers, Paul Ceruzzi, chairman of the Smithsonian’s National Air and Space Museum’s space history division, said in an interview.
“They have to address the safety issue very carefully,” Ceruzzi said.
The $200 million Antares rocket and spacecraft exploded in an orange plume over the Wallops Flight Facility on Virginia’s eastern shore on Oct. 28.
After an unspecified failure occurred seconds into the launch, Orbital’s engineers intentionally destroyed the craft, Frank Culbertson, an executive vice president for the Dulles, Virginia-based company, said at a news conference the night of the accident.
The rocket’s first stage is powered by a mix of kerosene and liquid oxygen. Its engines are the AJ-26, a refurbished version of Russian-made NK-33 models. The company has had issues with the engines and is speeding plans to move to a newer type, Orbital Chief Executive Officer Dave Thompson said Oct. 29 on a conference call with analysts.
Orbital, which has a $1.9 billion contract with NASA to supply the International Space Station, has a record of success that is “one of the best in the world,” Thompson said.
Out of 284 launches in more than 30 years, the company has succeeded 95 percent of the time, he said. The record improved to 96 percent in its 106 launches in the last 10 years, he said.
The overall unmanned rocket success rate is about the same, Ceruzzi said.
By comparison, U.S. airlines reported one fatal crash in the past five years, a success rate of 99.999998 percent.
Centennial, Colorado-based United Launch Alliance’s Atlas V rocket, which hoisted a global-positioning satellite into space on Oct. 29, hasn’t had a launch failure in 50 flights since 2002, according to the company’s website.
While the Russian Soyuz rocket lifting two Galileo positioning satellites Aug. 22 for the European Space Agency didn’t fail as spectacularly as the Antares explosion, it put them into the wrong orbit where they may not be functional, according to the agency’s website.
Such mishaps are the price for space exploration and commerce, Ceruzzi said.
“Unless somebody invents warp drive or something else, the physics are just there,” he said. “To go from zero to 17,500 miles an hour in a very limited amount of time, iron clad rules of physics come into play and you can’t get around them.”
That speed, equal to 28,000 kilometers an hour, is needed to get an object into space. The amount of energy released to reach that speed causes bone-jarring vibrations, and extremely precise navigation and timing are required to ensure the rocket ends up on the correct path, he said.
The space shuttle, designed to carry large payloads into space and then glide back to earth so it could be reused, suffered two failures in its history from 1981 to 2011. Both were triggered by the violence of launch.
In 1986, one of shuttle Challenger’s two booster rockets developed a leak of hot gas that caused it to break apart and explode.
Columbia was destroyed in 2003 as it burned up while reentering earth’s atmosphere. Days earlier during its liftoff, a piece of foam had struck the shuttle’s heat shield with such force that it allowed hot gases to enter the orbiter’s left wing. The two accidents killed 14 crew members.
Engineers at NASA initially thought they had designed the shuttle to have a risk of failure of one in a thousand or better. Only after the accidents and a more thorough review of potential failures did the space agency’s engineers understand how risky it had actually been.
A NASA study concluded the chance of a failure on the shuttle’s first launch was one in 12, or 8.3 percent. Some of the other early launches were deemed even riskier, about 10 percent, according to the study.
“It is not uncommon for a final system design to present significantly more risk than its original designers expected due to what are known as ‘unknown unknowns,' “ NASA’s Aerospace Safety Advisory Panel wrote in a report on Jan. 15. The group makes safety recommendations to the U.S. space agency.
At the end of the shuttle’s life, risks had been reduced to about one in 90 per flight. At that rate, 272 U.S. airliners would crash out of the average 24,000 flights a day.
By comparison, there has been one fatal accident on a U.S. passenger carrier since 2009 out of more than 50 million flights, according to the U.S. National Transportation Safety Board.