WALLOPS ISLAND, Virginia—Every time NASA launches a rocket, two safety officers have one weighty decision: They have to decide whether to push a self-destruct button if it appears the launch is going awry.

If they make the wrong call either way, bad things can happen. Destroy a rocket prematurely, and millions of dollars in equipment and research go up in flames unnecessarily. Allow a malfunctioning rocket to continue, and the lives of people near the launch site could be at risk.

Tuesday night, I saw what happens when they make the right call. A 139-foot-tall (43 meters) Antares rocket malfunctioned shortly after takeoff, and was destroyed in a massive explosion at the launch site after safety officers sent a kill signal. The glow from the accident was visible for miles up and down the coast, but because of the safeguards in place, no one was injured.

The flight safety officer and the range safety officer are tasked with deciding whether a rocket is operating properly and either disabling it for safety reasons or letting it proceed. There can be just seconds to decide, and there is no instant replay.

I was one of thousands of people who gathered Tuesday night near Wallops Island on Virginia's Eastern Shore to watch the unmanned Antares rocket launch. The spacecraft was loaded with scientific experiments and supplies for the International Space Station.

View Images NG Staff

For reasons still being investigated, the rocket started behaving erratically and exploded in a mountain of flame and smoke. This inferno burned across an otherwise picturesque post-sunset sky, accented high above the horizon to my right by a sliver of a crescent moon. (Read an early account of the accident.)

The explosion happened after safety officers, watching for any of ten specified problems, such as a gross deviation from the flight path, sent a signal from the flight termination system to disable the rocket, although damage from the malfunction may have already doomed it to collapse back to Earth. (Read about the ongoing investigation.)

Standing in the media viewing area, about two miles (three kilometers) from the launchpad, I was as close as anyone was allowed to be, with the exception of a few members of the launch crew.

Most of these crew members were in a hardened blockhouse near the launchpad, but two had a very special role that required them to stand out in the open.

In an age of increasingly sophisticated digital technology, the go or no-go decision is sometimes made with technology that is decidedly from the analog age.

In the early seconds of a launch, when the rocket is near the ground, there is too much interference from trees and nearby structures for radar and other monitoring systems to be accurate. So spotters watch the launch through wooden viewing frames fitted with guide wires. If the rocket crosses behind a wire, they know it's veering off track and they send up an alarm telling the safety officers to abort. Then they seek shelter.

I had come to write a benign travel story about being a space groupie at a place that is also famous for wild ponies and Chesapeake Bay oysters, so it took a few moments to realize the story had evolved. I was witnessing a disaster.

Even a successful launch produces an incredible amount of smoke and fire as the thrust pushes a 652,000-pound (296,000-kilogram) rocket out of the atmosphere. In this failed launch, fuel that was meant to burn off gradually instead exploded in a ferocious fireball.

Spirals of flame fanned out from the launchpad in all directions as the controlled burn gave way to chaos. The scene in my camera's viewfinder was utterly overwhelming.

As the overpressure pushed out from the launchpad, I could feel the explosion as well as see it. Elsewhere, the same shock wave knocked two spectators off the bed of their pickup truck and another off her dock. The blast broke windows and imploded doors in buildings close to the launch site.

We had been warned upon arrival that things can always go wrong, but at the time it had seemed like an abundance of caution, a flight attendant's speech to frequent fliers. Caution had already delayed the launch from Monday night, when a single sailboat in a restricted area caused a cancellation. On this night, there was a chance of another delay: Shifting winds meant that the crowds gathered on nearby Assateague Island had to move farther away from the flight path for safety.

It's easy to delay a rocket. A mechanical problem, weather that's just a bit off, or a 32-in-a-million chance that someone will be injured can all scrub a launch. Monday's caution had been met with disappointment and irritation since only about half of the crowd could return for the rescheduled launch.

But in the orange glow of Tuesday's catastrophe, the words we had been told to listen for finally registered. "Back to the bus. Back to the bus."

View Images Launched at 6:22 p.m. EDT, the spacecraft ascended straight up before an explosion blossomed from its tail—a "catastrophic anomaly," according to NASA. Photograph by Brad Scriber, National Geographic

So back we went. The VIPs and NASA employees watching nearby did so as well. Out the bus windows, we could see the slurry of fire that had spilled across the launch area and surrounding marsh. A parade of fire trucks rushed in the other direction to contain it.

We learned that no one had been hurt—not even the sky scanners with their picture-frame viewfinders. With no human toll, we were free to marvel at the spectacle.

At a briefing about the incident that evening at the visitor center, we heard from NASA's William Gerstenmaier, who pointed out that "launch is a really tough business. When we look at all these events that occur flawlessly and go well, we need to recognize how difficult and demanding this business really is."

Frank Culbertson, an executive with Orbital Sciences, the private company whose rocket was being launched, added, "It's a tough time to lose a launch vehicle like this and its payload. It's not as tragic as losing a life associated with it ... All we lost was hardware." It's valuable hardware and represents intense efforts and investment, but Orbital vowed to return and keep launching.

A stretch of success can make one forget how audacious and complicated it is to maintain the human footprint in space. A well-managed disaster can renew respect for the cautionary principles that can lead to those discouraging delays for spectators. It's a reminder that there's nothing routine or simple about spaceflight.

It is, after all, rocket science.