With a launch pad in Virginia covered in rocket debris, Orbital Sciences Corp. saw its stock price drop 16 percent Wednesday as investigators began to figure out why the company’s Antares rocket exploded catastrophically Tuesday night just seconds into a planned cargo run to the International Space Station.

The Dulles, Va.-based company said it did not know why the launch failed. The explosion didn’t hurt anyone at Wallops Island on Virginia’s Eastern Shore, but it sent the company scrambling to understand what happened and reassure investors that there’s no long-term problem.

“Orbital has experienced adversity in the past, some of which was more difficult than this,” Orbital chief executive David Thompson said in a conference call with investors. He also noted that the Wallops Island launch pad didn’t suffer significant damage during the explosion.

The company said it is looking to develop a new rocket engine to replace the controversial older Russian engines that it has been relying on.

The failure of the rocket could begin to raise questions about the Obama administration’s push toward a more commercially oriented space program. But on Wednesday, members of Congress were defending the program.

A rocket that was to resupply the International Space Station blew up Tuesday night a few seconds after lift-off from Wallops Island, Va. (NASA)

“Space flight is inherently risky,” Sen. Bill Nelson (D-Fla.), chairman of the Senate Commerce subcommittee on science and space, said in a statement. “As we push the frontiers of space, there will be setbacks. But our commercial space ventures will ultimately be successful.”

Orbital has a $1.9 billion contract with NASA to fly cargo to the space station. It’s a “commercial” contract, meaning NASA pays a fixed price for a set number of cargo deliveries. Another company, SpaceX, owned by entrepreneur Elon Musk, also has a commercial cargo contract. NASA stopped flying such low-orbit missions when it ended its shuttle program in 2011.

The Antares rocket was supposed to boost an unmanned Cygnus spacecraft to the space station with about 5,000 pounds of food, water and equipment aboard.

The rocket’s flight-termination system, which is designed to detect flight anomalies, was engaged shortly after launch, causing it to self-destruct. It is unclear whether that system was triggered by the rocket’s automated on-board systems or by mission control, Orbital Sciences spokesman Barron Beneski said Wednesday.

Despite the failure, astronauts aboard the space station are in no danger of running out of supplies.

A Russian resupply vehicle blasted off from Kazakhstan and successfully docked with the space station Wednesday, about 15 hours after the Antares disaster at Wallops Island.

“We will determine the root cause, and we will correct that, and we will come back and fly here at Wallops again — hopefully in the very near future,” Frank Culbertson, a former NASA astronaut who serves as executive vice president at Orbital Sciences, said at a news conference Tuesday night. “But we will do all the things that are necessary to make sure it is as safe as we can make it, and that we do solve the immediate problem of this particular mission.”

The unmanned 133-foot-tall Antares rocket that exploded over Wallops Island, Va., on Tuesday contained major components from three countries, including a Russian engine made in the 1970s. It was loaded with nearly 5,000 pounds of supplies bound for the International Space Station. NASA said it does not know what caused the accident.

Culbertson said the investigation will include evaluating the debris around the site. He asked residents in the area to contact local authorities if they find pieces of the rocket on their property, or if they locate scraps that might wash ashore.

“We have reams and reams of data that comes down from the rocket during launch, and we will be analyzing that carefully to see if we can determine exactly the sequence of events, what went wrong, and then what we can do to fix it,” Culbertson said. “We also have video evidence that we’ll be evaluating to help us with the investigation.”

That work began with an aerial survey of the launch pad area along the coast of Wallops Island; a team is searching for debris and evidence of hazardous materials, such as propellant or rocket motor fuel.

“The thing that’s important is that we don’t overreact to this failure — that we really understand what occurred, we let the Orbital team run the investigation, we understand what happened, we fix it,” Bill Gerstenmaier, NASA’s associate administrator of human exploration and operations, said at a Tuesday news conference.

Orbital Sciences has been criticized for its use of the refurbished Soviet-era Russian AJ-26 engines.

Musk, chief executive of SpaceX, called use of the rockets “the punchline to a joke.”

“It uses Russian rocket engines that were made in the ’60s,” Musk told Wired magazine in 2012. “I don’t mean their design is from the ’60s — I mean they start with engines that were literally made in the ’60s and, like, packed away in Siberia somewhere.”

In a tweet Tuesday night, Musk said he was “sorry” to hear about the launch failure. “I hope they recover soon,” he wrote.

Beneski said his company has successfully launched eight AJ-26 rockets — two on each of its four previous missions — without any problems.

In Wednesday’s call with investors, however, Thompson said the failure of the Antares launch could speed up the development of a new propulsion system to replace the Russian engines.

Orbital is developing a second-generation version of the Antares rocket engine for NASA and is on track to test that in two years’ time, he said.

Thompson said Orbital “may decide to accelerate this change if the AJ-26 is implicated in the failure.”

Marco Caceres, the director of space studies for the Teal Group, an aerospace industry analysis firm, predicted Wednesday that the launch failure would inevitably lead to “Monday morning quarterbacking” from “people within Congress and the space industry who continue to believe that NASA should continue to own, manage and operate its own launch vehicle instead of leasing launch services from private companies.”

But, Caceres said in an e-mail: “The reality is that catastrophic launch failures like the one we saw yesterday have little to do with whether it’s a private company managing things or NASA. NASA has had its share of horrendous failures — both in terms of launch vehicles and satellites. The idea that the government is inherently better suited for spaceflight is a myth.”

Christian Davenport, Ed O’Keefe and Dana Hedgpeth contributed to this report.