The next generation - unmanned space vehicles, includes related article

Airman, March, 2003 by Carte A. Seydel

Unmanned space launches aren't a new concept. Since Explorer 1, the first U.S. satellite to orbit Earth, was launched into space in 1958, there has been a long list of successful missions.

The future of space vehicles lies in the thrust of a program that combines economy and efficiency into a revolutionary capability-the evolved expendable launch vehicle.

Expendable means that every time one is launched, it's not reused, and it doesn't return intact. Although that may seem like an expensive disposable rocket, this spacelift modernization program, begun in 1995, has produced an affordable, more reliable space transporter.

The vehicles have become so affordable, in fact, that they cost 25 to 50 percent less than former systems. That's an estimated savings of $6 billion in launch costs in the next 18 years.

"We're making sure we can continue to meet national security needs at minimum cost to the taxpayer," said Lt. Col. Tony Taliancich, director of the evolved expendable launch vehicle consolidated task force at Cape Canaveral Air Force Station, Fla.

The idea was to use a standard booster core with a flexible payload "attachment" that meets changing mission requirements. Two companies won the government contract to create the modernized high-tech version. Under the guidance of Air Force Space Command and the Space and Missile Systems Center, Los Angeles Air Force Base, Calif., Boeing and Lockheed Martin designed rockets that can be configured to handle almost any payload.

Atlas V

The original Atlas program started as the first intercontinental ballistic missile in the late 1950s. As the "space race" escalated with the Soviet Union, the program evolved as a space launch vehicle.

The first evolved expendable launch vehicle sent into orbit was the Atlas V, built by Lockheed Martin. With the inaugural launch in August 2002, it was the beginning of a $500 million contract to launch seven vehicles.

"We've applied the best practices from Atlas' ancestors and the Titan program to create the next generation of launch vehicle," said Adrian Laffitte, director of the Atlas program at Lockheed Martin.

The most recent Atlas rocket, at 192 feet high, is made up of a standard booster that makes up about one third of its length and, depending on the load, can be configured in one of four ways to accommodate payloads up to 19,000 pounds to geosynchronous transfer orbit-or an orbit that remains above a specific location on Earth. It's put together in a vertical integration facility that's 292 feet high, with a 270-foot vertical accordion fabric door. At liftoff it weighs from 734,850 to 1,191,250 pounds depending on its configuration.

"We evolved by making continuous improvements, and with 85 percent of the onboard systems proven before launch we've had confidence in the program," Laffitte said. "Everyone sees the excitement of those few seconds of liftoff, but behind that there are thousands and thousands of man-hours put into getting there."

Approximately eight hours before a launch, the rocket is moved to the launch pad on a mobile launch platform used to stack, transport and launch the Atlas V. This eliminates the need for the mobile service tower used by Atlas II and III rockets to support vehicle servicing and launch operation activities.

Once the vehicle arrives at its Complex 41 launch pad on the cape, it sits surrounded by towers that protect it from lightning strikes.

"What's amazing about this business is that there are thousands of components that need to work together exactly the way they were designed," Laffitte said. "Because if one of them doesn't work, it could be a very bad day for all of us."

Liquid oxygen and kerosene fuel the rocket as the RD-180 booster engine is started. There's an internal ignition that "sparks" the chemical reaction.

"It's similar to the ignitor on your gas grill," he said. "It gives you a spark to get the engines going, and the fuel gives it the thrust."

And it takes a lot of fuel to generate that thrust.

"When we launch an Atlas V. we're consuming about a swimming pool of fuel every second for about three minutes and 10 seconds," Laffitte said. That's 1.9 million gallons of fuel.

After liftoff, at nearly 100 percent of rated thrust, the engine throttles back momentarily. At about five minutes into the flight the booster engine drops off and the payload fairing--a protective shell--jettisons.

Then the cryogenic upper stage, called the Centaur, using liquid hydrogen and liquid oxygen at temperatures 250 degrees below zero, takes over igniting for about a minute and a half. Then the rocket coasts into orbit for 15 minutes until an explosive charge loosens the bolts that attach the satellite to the Centaur.

"Knowing when to coast is rocket science," Laffitte said. "Preprogramming of the onboard computer system contains the orbital parameters, the wind variation to adjust the trajectory and the timing to ensure the satellite ends up in the right orbit."

Delta IV

Just a few miles away, Boeing works on another expendable launch vehicle--the Delta IV. Awarded 22 launches for $1.7 billion, the first one blasted off in November 2002.