WASHINGTON — Orbital Sciences Corp.’s business case for its Taurus 2 rocket, scheduled to debut this year, assumes two or three launches per year for the next decade, with liftoffs occurring from a future West Coast spaceport in addition to the company’s new launch pad at NASA’s Wallops Flight Facility, which is owned by the Virginia Commercial Spaceflight Authority, on Virginia’s eastern shore.

Mark Pieczynski, Orbital vice president of space launch business development, says the Dulles, Va.-based company has spent the past several months eyeing two launch sites on the West Coast that would allow the company to deliver medium-class payloads to high-inclination and sun-synchronous orbits: Vandenberg Air Force Base, Calif., and Kodiak Island, Alaska. The company expects to decide on a site before the end of the year, he said.

High-inclination, or near-polar, orbits are typically used for Earth observation because they provide global coverage. Vandenberg and Kodiak are geographically suited for launches to such orbits.

“Vandenberg is a well-known commodity to us; we understand it well,” Pieczynski said in a May 18 interview, noting that the company currently launches Pegasus, Taurus XL and Minotaur rockets from that site.

Orbital is less familiar with Kodiak Island, he said, though the company does use the launch site for Minotaur missions.

“We’ve been focusing a lot of attention over the last several months to understand what the capabilities are out of Kodiak,” he said, adding that the launch site “brings some uniqueness” in terms of launch preparation and logistics. “Where do you get all your commodities from, how do you get your launch vehicle up there, can you launch 12 months out of the year?” he said.

Orbital already is under contract to NASA for 10 missions to deliver 20 metric tons of pressurized cargo from Wallops to the international space station through 2015. If Taurus 2 and Orbital’s Cygnus cargo vehicle perform as planned, he said, the company expects a follow-on contract to provide roughly two launches to the orbiting outpost each year through at least 2020.

Pieczynski said NASA would be a prime customer for West Coast launches; the agency currently lofts a number of science payloads to high-inclination orbits each year from Vanenberg. Orbital plans in August to offer Taurus 2 for inclusion in NASA’s stable of rockets eligible to launch the agency’s science missions.

“There are also foreign dual-use payloads that are commercial launch and the preference on some of those are to launch on a U.S. rocket on U.S. soil simply because of the dual-use nature of the payload,” he said. “So we see a need to establish that West Coast launch site,” he said.

Pieczynski said Orbital expects the West Coast launch site to be operational within two years of site selection, with plans to draw on lessons learned from development of the Wallops launch facility. “The design work [at Wallops] is done and paid for,” he said.

Pieczynski said Orbital also sees a market for launching medium-class national security payloads from the West Coast. He said Orbital plans to offer Taurus 2 for inclusion in the U.S. Air Force’s stable of approved rockets this year.

“Quite frankly, historically, there have been many medium-class missions launched by the Air Force,” he said, including almost all GPS satellites flying today. “And there’s typically a [National Reconnaissance Office] mission every other year of a medium-class.”

He said the Air Force is expected to release a draft request for proposals soon, with plans to have all proposals in by the end of the calendar year.

Orbital’s Taurus 2 business scenario assumes two additional variants will be developed in the coming years. The basic vehicle can carry 5,100 kilograms of payload to a 52-degree orbit at a 200-kilometer altitude, or 3,200 kilograms to a 90-degree, 600-kilometer orbit.

The Taurus 2e, which is planned to be operational in 2013, will be equipped with a larger version of the Castor 30 second-stage engine, made by Alliant TechSystems and will be capable of lofting 6,000 kilograms to a 52-degree orbit at 200 kilometers or 4,200 kilograms to a 90-degree, 600 kilometer orbit. By 2014, the company expects to debut the Taurus 2h, which will be a third stage for even more payload carrying capability.

Orbital spokesman Barron Beneski said despite plans to expand Taurus 2’s opportunities, the company is taking a conservative approach to the medium-class launch market.

“If we’re able to book a couple more commercial launches in addition to the government market we forecast, and if the government market comes in as forecasted, there’s likely to be some upside,” Beneski said in a May 18 interview. “But we’re not counting on upside. We have a very conservative outlook for this program, to make sure the business case works with a modest and reasonable expectation for the launch rate.”

The company has no immediate plans to upgrade Taurus 2 for geostationary launches of lightweight communications satellites.

“Instead of trying to solve world hunger in a real short period of time, we’re going to use what has been Orbital’s philosophy over the 25 plus years of existence, and that is methodical development minimizing risk addition to the launch vehicle,” Pieczynski said. “But there will come a point in time when we look at the ability to deliver to [geostationary orbit], and it may be a completely different upper-stage.”