When Orbital Sciences' test spacecraft fell from orbit last week, the company saw the fiery blaze as a cause for celebration — but it was also the cause of a UFO mystery, at least for a little while.

The spacecraft was a dummy payload, which was launched into orbit on April 21 aboard Orbital's newly developed Antares booster during its maiden flight. The satellite's primary purpose was to simulate the mass of the company's Cygnus cargo capsule, which will eventually be launched by the Antares to resupply the International Space Station.

Orbital never intended the Cygnus Mass Simulator to stay in space. Its orbit gradually decayed over the course of more than two weeks, and on the night of May 9-10 it finally made its descent through the atmosphere. As it fell, aerodynamic forces heated it up, and tore it apart. It broke into several dozen flaming fireballs, streaking together from horizon to horizon across the evening skies of Chile and Argentina.

Just by luck, the spectacle unfolded over a populated region. It was widely seen, and widely recorded. Within hours, a dozen videos of the sky show were posted on YouTube.

The videos thrilled the Antares team. "It was a spectacular ending to a great beginning,” said Barry Beneski, the company's publicity director. Operators in their flight dynamics lab, who had designed the mission, were more down to Earth: "Way cool!" was their first comment.

But for many of the eyewitnesses, the aerial blaze was a real mystery, since no advance word of the spacecraft's destruction had been issued. Was it a comet or a meteor shower? A blimp or fleet of Chinese lanterns? Theories raced around the Internet.

The leading theory, as might be expected, was that the object was a descending spaceship. The scattered dazzlers assembled themselves in the perceptions of many witnesses as outlining a large structure with mounted lights. It was widely seen as an awesome military secret, or even an interplanetary visitor.

It was an honest misperception.

Was the Pentagon in the dark?

It didn't help that the U.S. Strategic Command apparently misidentified the object in orbit. In advance of re-entry, the Pentagon's space catalog listed it as a tiny test satellite that should have burned up without a trace.

Orbital Sciences

This map of South America shows segments of the Cygnus Mass Simulator's final orbits, ending with re-entry over Argentina. The final track matches up well with UFO sightings on the night of May 9-10.

Within hours of the satellite's re-entry, Canadian amateur satellite tracker Ted Molczan matched up the UFO reports with the satellite catalog entry. "The time and location of the sighting correlates with the re-entry of 'object Bell,'" he reported on the SeeSat discussion board.

Molczan added that the Strategic Command had issued a "prediction" several hours after the actual re-entry, saying that the satellite would hit the atmosphere soon after midnight GMT on May 10. The trajectory had the minisatellite coming down over the area of South America where the UFO sightings were reported.

The problem was, the Bell minisatellite described by the Strategic Command and NORAD was only 4 inches (10 centimeters) wide, about the size of a tissue box. When Molczan rechecked the records, he determined that the minisatellite should have fallen from orbit just days after its launch. The Antares booster stage was destroyed during re-entry on May 1. That left only one other sizable object associated with the Antares launch: the 8,377-pound (3,800-kilogram) Cygnus Mass Simulator.

The Strategic Command's public affairs office has not yet confirmed the correct identity of the object that was seen falling out of orbit, despite repeated inquiries from NBC News.

Other secrets
Orbital Sciences, the spacecraft's owner, would have been legally responsible for any damage caused by falling debris. For that reason, the company took great pains to reduce the potential debris hazard.

Orbital Sciences

A schematic shows the latticework structure inside Orbital's Cygnus Mass Simulator.

The mass simulator payload was built using an open lattice structure, designed to tear apart quickly during re-entry. Each of the separate pieces was meant to burn up completely, providing observers with a view of fiery streaks flashing across the sky. And that's exactly what happened.

No advance warning was given, because no threat was expected. Orbital's Beneski said  the company merely planned to post a note on the project's Facebook page, at some point after re-entry. The inquiries from NBC News caught Orbital's officials by surprise — but they then responded fully and quickly.

UFO buffs shouldn't be disappointed. The event demonstrated that large satellite re-entries can really look like giant spaceships with mounted lights. Such reports fill the files that have been kept by UFO researchers over the past half-century — and many of those reports could well be unrecognized satellite re-entries as well.

More about UFOs:

• FBI comes clean on top UFO X-File
• UFO linked to Russian missile test
• Cosmic Log archive on UFOs

NBC News space analyst James Oberg spent 22 years at NASA's Johnson Space Center as a Mission Control operator and an orbital designer.

Steve Helber / AP

The Antares rocket is illuminated by lights on Tuesday night, waiting for launch from a Virginia spaceport.

Orbital Sciences Corp. postponed the maiden launch of its Antares rocket on Wednesday when an umbilical data cable was disconnected prematurely from the launch vehicle's second stage.

The launch abort came at about 4:48 p.m. ET, just minutes before the Antares was due to lift off from the Mid-Atlantic Regional Spaceport on Wallops Island, Va. Orbital said the 5 p.m. ET liftoff would be rescheduled for Friday at the earliest.

"We are still examining all of the data, but it appears that the issue is fairly straightforward," Frank Culbertson, Orbital’s executive vice president and mission director for the Antares test flight, said in a company statement. "With this being the first launch of the new system from a new launch facility we have taken prudent steps to ensure a safe and successful outcome. Today, our scrub procedures were exercised and worked as planned.  We are looking forward to a successful launch on Friday."

Imagery posted to the independent NASASpaceFlight.com website showed a tower on the launch pad twisting in a motion that could have dislodged the data cord from its connector.

Orbital is giving the Antares rocket its first in-flight test in preparation for trips to the International Space Station later this year. This time around, the rocket is carrying merely a dummy payload, along with some secondary satellites that are to be deployed in orbit. But if the practice run is successful, Orbital could start providing a second line of made-in-the-USA commercial vehicles for resupplying the space station.

The Virginia-based company is following in the footsteps of California-based SpaceX, which began cargo runs to the space station last year.

Orbital and SpaceX have received hundreds of millions of dollars from NASA to develop their transports, as part of the space agency's strategy to replace the space shuttle fleet. The shuttles were retired in 2011 to make way for a new generation of spaceships capable of going beyond Earth orbit. NASA wants private companies to take over the role of getting cargo — and eventually astronauts as well — to low Earth orbit.

Orbital won NASA's contract for the Antares rocket and the Cygnus cargo capsule in 2008.

A simulated Cygnus payload is to be lofted into orbit during a 10-minute ascent, and is expected to remain in orbit for several weeks before plunging to its fiery doom in Earth's atmosphere. Four tiny satellites are to be deployed from the simulator, including three smartphone-equipped PhoneSats for NASA (Alexander, Graham, and Bell) and the commercial Dove-1 remote-sensing nanosatellite. The main point of the mission, however, is to check whether Antares is ready to send cargo to the space station.

"This is a big event for the Eastern Shore, for Wallops and for everybody in the surrounding area, but also, I think, for the country," Frank Culbertson, executive vice president and general manager of Orbital's Advanced Program Group, said during Tuesday's pre-launch briefing.

He cautioned journalists not to expect a perfect test flight. "That first word is 'test,' so if things don't go exactly as planned, we will learn what we need to learn and press on," he said.

If the test is successful, another Antares is due to send a real Cygnus capsule to the space station as early as this June. And if that demonstration flight succeeds, Orbital could proceed with a series of eight resupply flights to the station under the terms of a $1.9 billion contract with NASA. SpaceX is already two flights into its own 12-mission, $1.6 billion resupply contract.

Phil McAlister, NASA's director of commercial spaceflight development, said Orbital would play an important role in providing "assured cargo access" to the space station. The idea is that if SpaceX's Falcon 9 rocket and Dragon capsule are grounded for technical reasons, Orbital's Antares and Cygnus would serve as a backup — and vice versa. That wasn't the case during the space shuttle program, when NASA's only Plan B was to rely on other countries' spaceships.

"We are in such a better situation today, and [it's] about to be even better with the debut of this new capability," McAlister said.

NASA is following a similar approach for the development of U.S.-made spaceships for crew transport. Three companies — SpaceX, the Boeing Co. and Sierra Nevada Corp. — are splitting more than a billion dollars of NASA's money during the current phase of work. NASA expects commercial crew transports to start flying to the space station by 2017. 

Correction for 6:55 p.m. ET April 17: I've cleaned up a couple of errors, including the date when Orbital won NASA's nod in the Commercial Orbital Transportation Services program (2008, not 2007) and the SpaceX contract amount under NASA's Commercial Resupply Services program ($1.6 billion, not $1.6 million).

More about the Antares rocket:

• Five things you didn't know about Antares
• Watch as Antares rises into orbit

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NASA

Orbital Sciences Corp. lights up the engines on its Antares rocket for a hot-fire test at the Mid-Atlantic Regional Spaceport in Virginia on Friday.

By Tariq Malik
Space.com

Orbital Sciences Corp. has successfully tested the engines for a new private rocket designed to send cargo to the International Space Station.

The Virginia-based company test-fired the first-stage engines of its new Antares rocket for 30 seconds Friday night at the Mid-Atlantic Regional Spaceport on Wallops Island, Va. NASA's Wallops Flight Facility, also based on the island, supported the so-called static fire engine test, which involved having the Antares rocket fire its engines without leaving the launch pad.

"This pad test is an important reminder of how strong and diverse the commercial space industry is in our nation," Phil McAlister, director of commercial spaceflight development at NASA Headquarters in Washington, said in a statement released after the test. "A little more than one year after the retirement of the space shuttle, we had a U.S company resupplying the space station, and another is now taking the next critical steps to launch from America’s newest gateway to low-Earth orbit."

Orbital Sciences is one of two private spaceflight companies with billion-dollar NASA contracts to provide unmanned cargo delivery missions to the International Space Station. Under its $1.9 billion contract, Orbital Sciences will make at least eight delivery flights to the space station using its Antares rocket and robotic Cygnus spacecraft. The first Antares rocket test flight is expected later this year. [Antares Rocket and Cygnus Explained (Infographic)]

California-based SpaceX is the other company with a NASA contract for unmanned space station deliveries. SpaceX has a $1.6 billion contract to fly at least 12 missions to the space station using its Dragon space capsules and Falcon 9 rocket. The company launched both a test flight and a bona fide delivery mission to the space station in 2012. The second delivery flight under the contract is slated to launch on March 1.

With NASA's retirement of the space shuttle fleet in 2011, the space agency is relying on new private rockets and spacecraft to ferry cargo — and eventually astronauts — to and from low-Earth orbit. NASA is currently dependent on Russia, Europe and Japan for cargo deliveries to the space station. Russia's Soyuz spacecraft are the only vehicles currently available to ferry astronauts to and from the station.  

Friday's engine test marked Orbital's second attempt to check the Antares rocket's dual AJ26 rocket engines, which are designed to provide 680,000 pounds of thrust. A first attempt on Feb. 13 was aborted before engine ignition due to a "low pressurization" detection during a nitrogen purge in the rocket's aft engine compartment, Orbital officials said.

The test took place at Pad-0A at the Mid-Atlantic Regional Spaceport, which is located on the eastern shore of Virginia. It set the stage for a full-up flight test of the Antares rocket, and then a demonstration flight as part of Orbital's contract under NASA's Commercial Orbital Transportation Services program, also known as COTS.

"Following the successful completion of the COTS demonstration mission to the station, Orbital will begin regular cargo resupply flights to the orbiting laboratory through NASA's Commercial Resupply Services contract," NASA Wallops officials said.

This report was updated by NBC News Digital. You can follow Space.com managing editor Tariq Malik on Twitter @tariqjmalik. Follow Space.com on Twitter @Spacedotcom. We're also on Facebook and Google+. 

• Pushing Freight To Space Station - Antares Rocket Animation
• Special Report: The Private Space Taxi Race
• SpaceX Dragon Capsule's 1st Station Cargo Flight to Station (Photos)

© 2013 Space.com. All rights reserved. More from Space.com.