The Antares commercial launcher and its pressurized Cygnus cargo carrier may reach the International Space Station before the end of the year, but only if problems with its launch pad on Wallops Island, Va., can be cleared and it does not run into conflicts with delayed Russian vehicles.

Orbital Sciences Corp., one of two companies under contract to resupply the ISS with vehicles developed under NASA's Commercial Orbital Transportation Services (COTS) seed-money effort, hopes to meet its final COTS milestone with a Cygnus berthing at the station in the fall. That could clear the way for a first delivery under Orbital's $1.9 billion, eight-flight Commercial Resupply Services (CRS) contract by year-end, according to CEO David Thompson.

After “eight to nine months” of delays while propellant-handling facilities in the greenfield pad were redesigned, Orbital engineers hope to roll the first Antares launcher from its integration facility to the pad and erect it early in April for fit checks and other work, Thompson says.

It will be returned in the horizontal orientation to the integration building, where the launcher will await a hold-down hot-fire test after the pad is fully tested and certificated by NASA, which runs the Wallops Flight Facility. That static test should come in May, Thompson said Feb. 21, in reporting company earnings for 2011.

The first test flight of the liquid-fueled rocket—with an instrumented Cygnus mass simulator on top—could come late in June or early in July, followed by the COTS demonstration flight late in August or early in September to deliver the first Cygnus to the ISS for grappling and berthing with the station's robotic arm.

“I want to stress that this sequence of events assumes that all major activities proceed smoothly without major technical problems, which, if they were to occur, would likely delay subsequent milestones from these targeted dates,” Thompson says.

A testing problem with the next Russian Soyuz capsule scheduled to take crew members to the ISS also could hamper Orbital's plans, as could more delays with its COTS competitor, Space Exploration Technologies (SpaceX). Workers accidentally overpressurized the Soyuz, forcing managers to order it scrapped, while the SpaceX COTS demo is slipping toward May (AW&ST Feb. 6, p. 16).

That may complicate the ISS traffic schedule late in the year, when Orbital wants to fly its first CRS mission. The replacement Soyuz capsule, which also must be pressure-tested before launch, will not be ready to carry its three-person U.S. and Russian crew to the orbital outpost until May 15. That six-week slip from the original launch date could cascade through the rest of the year.

The next Soyuz to return station crewmembers to Earth is now scheduled to land on April 28, instead of March 16, and the one after that will not come down until July, instead of May 16 as originally planned. The SpaceX Dragon is currently targeted to berth at the station on May 3, and so far there are no more SpaceX missions to the station scheduled this year.

But the two Orbital flights must work around Russian Progress dockings at the station now scheduled for Aug. 2, Nov. 3 and Dec. 28; Soyuz undockings on Sept. 17 and Nov. 12; and Soyuz dockings on Oct. 17 and Dec. 7. All of those activities require extra crew time, and there will only be three crewmembers on the station for three periods totaling about eight weeks during the rest of 2012.

“The best thing we can do is to be ready to go at the earliest date that's consistent with a safe and reliable mission,” Thompson says. “Hopefully, the window will open sometime in late August or September for the COTS demonstration launch.”

The Cygnus vehicle for that flight is complete and in thermal vacuum-testing at the company's Dulles, Va., satellite factory. It should be delivered to Wallops Island in June, Thompson says. The first Antares rocket reached the “98% complete point” at the end of December, he says, and should support the new launch schedule.

But while the ground equipment for handling the launcher's kerosene fuel is in good shape, the pumps and other gear needed to handle liquid oxygen and liquid nitrogen for the vehicle required redesign and repair, and will not be tested and certificated until the end of April. Orbital sent a 20-member team to Wallops to help oversee pad completion when it started to slip, according to a company spokesman, and the state of Virginia shifted responsibility for building the state-owned facility to its transportation department from its commerce department to capture the former's experience supervising large infrastructure projects.

Orbital has four flight-ready AJ26 engines at Wallops—enough for the first two launches—and more in the pipeline from Aerojet, its supplier.

“Assuming the first three [tests] go well, then I think the fourth one is a little bit anticlimactic because we will have fully demonstrated on multiple occasions most aspects of the cargo delivery system and at least on one occasion all aspects of it,” Thompson says. “So our focus right now is on those things we can control centered on those first couple of big milestones coming up mostly in the second quarter.”