In a major milestone for NASA, Orbital Sciences Corp. is readying a two-stage Antares rocket for launch Wednesday from the coast of Virginia to boost an unmanned Cygnus cargo ship on a maiden flight to the International Space Station.
The so-called demonstration mission is a high-stakes test run for Orbital to prove the company's new rocket and cargo ship can execute a normal autonomous rendezvous with the space station and, if necessary, safely carry out an abort if something ever goes wrong.
"This is the first time we've ever actually launched a dedicated spacecraft carrying cargo for human consumption in space," said Frank Culbertson, a former space shuttle commander and Orbital vice president. "So this is a big deal for us.
"Antares is the largest rocket we've ever developed, and this will be the first payload that we've ever launched that will rendezvous directly and autonomously with another vehicle of this size. It's been a long road to get to this point."
With forecasters predicting a 75 percent chance of good weather, Orbital plans to launch its second Antares rocket from the Mid-Atlantic Regional Spaceport at NASA's Wallops Island Flight Facility at 10:50 a.m. EDT (GMT-4) Wednesday.
Using recycled engines originally built for Russia's moon program and now provided by Aerojet Rocketdyne, the Antares first stage was expected to fire nearly four minutes, boosting the vehicle out of the dense lower atmosphere.
The rocket's second stage, powered by an Alliant Techsystems solid-fuel motor, then will take over, igniting at an altitude of 116 miles and firing for two-and-a-half minutes to put the spacecraft into an orbit with a high point, or apogee, of about 186 miles and a low point, or perigee, of around 151 miles.
After its solar panels deploy and engineers complete their initial checkout, Cygnus will begin a series of carefully planned rocket firings to catch up with the International Space Station early Sunday.
Along the way, NASA and Orbital flight controllers will test communications links, verify command and control procedures, check out the spacecraft's GPS navigation system and carry out a series of test maneuvers before clearing the ship for final approach to the station.
Assuming no major problems develop, the spacecraft will pull up to within about 30 feet of the lab complex around 7:15 a.m. Sunday.
After flight controllers complete a final round of checks, Italian astronaut Luca Parmitano, operating the station's robot arm, will lock onto a grapple fixture and the spacecraft will be pulled in for berthing at the Earth-facing port of the forward Harmony module.
For the demonstration flight, the Cygnus will be carrying about 1,600 pounds of food, clothing and other non-critical supplies and equipment. Culbertson would not say whether any "surprises" for the station's crew might be on board, quipping "if I told you what they were, they wouldn't be surprises."
With a successful demonstration flight, NASA will complete the primary objectives of its Commercial Orbital Transportation Services -- COTS -- program, which funded development of two commercial cargo carriers to take over U.S. space station logistics in the wake of the space shuttle's retirement.
Space Exploration Technologies, or SpaceX, holds a $1.6 billion contract with NASA to provide 12 cargo flights to the station for delivery of more than 44,000 pounds of equipment and supplies. A separate $396 million contract covered initial test and demonstration flights.
Orbital Sciences holds a contract valued at $1.9 billion for eight resupply flights to deliver 20 tons of cargo. Another $288 million ultimately was budgeted for development, the Antares test flight and this week's demonstration mission.
SpaceX successfully launched its Falcon 9 rocket with a dummy payload in 2010. The company then launched two test flights, sending company-built Dragon cargo ships to the station, and two operational resupply missions, the most recent flight in March.
Orbital launched the new Antares rocket, carrying a dummy payload, on a successful maiden flight last April. With this week's demonstration mission, the company expects to be ready to begin operational resupply missions later this year.
"We'll be attached to the station for approximately 30 days, and then 47 days after deorbit, we expect to launch ORB-1, as we call it, our first contract mission," Culbertson said. "So we are deep in preparation for that one already and going through the testing required."
Having Orbital and SpaceX on board with operational cargo vehicle will allow NASA to "get into a cadence," said space station Program Manager Mike Suffredini.
"It's time for us really to start having flights on a regular basis and expect that the next one will be there," he said. "So I'm looking at this next year, 2014, to be the year where we really settle in, where we have regular Orbital flights and regular SpaceX flights, and we actually see them within a few weeks of when we expect to have them there."
That's important, he said, for NASA's long-range plan "to reduce the amount of up mass we have for logistics, which we can do if we have a consistent supply chain, and really fill these vehicles up with research. That's the big transition we have to make in the next year now that we have Orbital flying as well."
Alan Lindenmoyer, director of NASA's commercial crew and cargo program, said this week's mission marks the end of one era for NASA and the beginning of another.
"Seven years ago, we started the program with a vision that we would be able to go to a catalogue or the internet and order up some argo delivery services to the International Space Station, similar to what you can do today with global overnight package delivery," said NASA COTS director
"Well, it's not exactly overnight yet, but last year we came very close to seeing that vision become a reality with our first COTS partner, SpaceX, completing a demonstration flight to the station and then providing followup missions, operational flights."
With a successful demonstration flight by Orbital, NASA will have a "second commercial partner ready to provide those services," he said. "So it's been a tremendous success. That vision is becoming reality."