WALLOPS ISLAND, Va. — A huge solar flare unleashed by the sun caused a 24-hour postponement for Wednesday's planned launch of a private cargo ship to the International Space Station, due to worries over space weather radiation.

The first major solar flare of 2014 erupted from a massive sunspot seven times the size of Earth on Tuesday after a series of midlevel sun storms in recent days. The event occurred as the commercial spaceflight company Orbital Sciences Corp. was preparing to launch a landmark cargo delivery flight to the space station with its Antares rocket and robotic Cygnus spacecraft.

"We are concerned about mission failure," Orbital's Chief Technical Officer Antonio Elias told reporters in a teleconference today. The company had to evaluate the extent of Tuesday's flare and the potential for solar radiation to interfere with critical systems such as gyroscopes and avionics on the Antares rocket, he added. [Biggest Solar Flares of 2014 (Photos)]

Elias said Orbital's Cygnus spacecraft is designed to withstand space weather events like Tuesday's flare during its weeks-long mission at the space station, so the vehicle isn't as vulnerable to the same radiation concerns as the rocket.

Late Wednesday afternoon, Orbital officials confirmed that they will attempt to launch the Cygnus on Thursday, with the liftoff window opening at 1:07 p.m. ET.

Space weather delay

Orbital Sciences has been monitoring space weather since Sunday, when the company began tracking an uptick in solar activity. But it was Tuesday's huge solar flare, which registered as an X1.2-class sun storm — the strongest class of solar flares the sun experiences — that led to Wednesday's delay. It occurred just hours after an intense M7.2-class solar flare earlier in the day.



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The Antares rocket was awaiting launch from a pad here at NASA's Wallops Flight Facility when the decision to delay was made. It is the latest postponement for the mission, which was initially delayed from a mid-December liftoff when astronauts on the station had to perform emergency cooling system repairs, and later pushed back a day due to the subfreezing temperatures affecting the United States this week. [Photos of Orbital's Antares Rocket at the Launch Pad]

"Sometimes, you just don't get off the ground when you want to," Orbital Sciences executive vice president Frank Culbertson told reporters during Wednesday's teleconference. "This isn't a failure in the system, it is a delay. But all we're really delaying is the success that's going to come when we execute this mission."

The solar flare posed no threat to the six spacefliers living on the International Space Station. The crew did not have to take any measures to shelter themselves from the solar flare's space radiation, NASA spokesman Rob Navias told Space.com in an email.

Giant sunspot spouts solar flare

By coincidence, the Jan. 7 solar flare occurred at 1:32 p.m. ET — exactly 24 hours before the appointed time for Wednesday's launch attempt— from an active sunspot region known as AR1944. The sunspot is facing Earth from the middle of the sun, as viewed from Earth, and NASA has called it "one of the largest sunspots seen in the last 10 years."

The sun is currently in an active phase of its 11-year solar weather cycle. The current cycle, known as Solar Cycle 24, began in 2008.



Orbital Sciences' Cygnus spacecraft had a 95 percent chance of acceptable weather for launch on Wednesday. That weather forecast deteriorates as the week progresses, with cloudy conditions dropping it to 75 percent chance of favorable weather on Thursday, and a 30 percent chance of good launch conditions on Friday. Rain is expected on Saturday, Culbertson said.

Orbital has a $1.9 billion contract with NASA to launch 40,000 pounds of supplies to the International Space Station by 2016 using its Antares rockets and disposable Cygnus spacecraft. The first Antares and Cygnus test flights launched in 2013, and the upcoming launch would mark the first official cargo delivery for Orbital.

For this delivery flight, called Orb-1, the Cygnus spacecraft is carrying 2,780 pounds (1,260 kilograms) of gear for the International Space Station. That haul includes a space ant colony, 33 small CubeSat satellites and 23 other experiments designed students from across the country.

The Dulles, Va.-based Orbital Sciences is one of two companies with a NASA contract to deliver supplies to the space station. The other company is SpaceX of Hawthorne, Calif., which has launched two of 12 planned delivery missions for NASA under a $1.6 billion agreement. The third mission in SpaceX's schedule is expected to launch from Cape Canaveral Air Force Station in Florida on Feb. 22.

Visit Space.com for complete coverage of Orbital Sciences' Cygnus cargo launch to the International Space Station. Space.com partner Spaceflight Now is also offering updates via its Cygnus Mission Status Center.

Email Tariq Malik at tmalik@space.com or follow him @tariqjmalik and Google+. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.