Orbital Sciences is still hoping for a March 2011 debut of the company's medium-lift Taurus 2 rocket, but challenges with facility construction and delays in ground testing could push the first launch later into next year, a senior manager said.

An artist's concept of the Taurus 2 rocket in flight. Credit: Orbital Sciences

Speaking to Spaceflight Now last week, Orbital senior vice president Frank Culbertson said first stage engine testing at Stennis Space Center in Mississippi is now projected to start in April or May.

The first batch of AJ26 engines is slated to arrive at Stennis no earlier than March, nearly a year later than expected in schedules announced in late 2008.

The Taurus 2 rocket first stage will use a pair of kerosene-fueled AJ26 main engines provided by Aerojet Corp. The AJ26 is derived from the NK-33 engine developed by the former Soviet Union for the ill-fated N-1 moon rocket of the 1960s and 1970s.

Aerojet imported the NK-33 engines from Russia in the 1990s. The Sacramento-based company has 37 NK-33 engines in inventory, plus a few more units of the NK-43 high-altitude engine, according to Julie Van Kleeck, Aerojet's vice president for space programs.

Orbital is building the Taurus 2 to launch the company's Cygnus cargo freighter to the International Space Station. The March 2011 launch will be a test flight of the Cygnus to the complex, and the first of eight operational logistics mission will follow late next year.

Aerojet is dusting off the NK-33 engines and converting them to the AJ26 configuration by adding U.S. electronics, qualifying the engines for U.S. propellants, and putting in equipment to permit the engines to gimbal for steering.

The NK-33 engines have been in storage for nearly 40 years, so Russia conducted hotfire tests in October to verify the units still worked. The engines consume liquid oxygen and refined kerosene propellants.

"These are tests that take the engines beyond our profile requirements and are making sure that we're within the limits of the engine itself," Culbertson said.

One test went as planned, but a second burn ended prematurely after problems with the liquid oxygen system.

"We stressed the engine pretty hard, and we discovered some limits we want to re-evaluate in [another] test," Culbertson said.

According to Culbertson, the ground test was cut short because of a problem in a liquid oxygen turbopump. Other reports have said the anomaly was in the test stand. Aerojet sponsored the tests in Russia.

Aerojet officials would not comment on the test failure becaues it is still being investigated, but Van Kleeck did say there were issues in ground systems.

Another round of Russian NK-33 tests could occur in February, "assuming the stand is in the appropriate condition," Van Kleeck said.

Aerojet has 37 NK-33 engines at its Sacramento headquarters. Credit: Aerojet

Van Kleeck said Aerojet is confident the once-forgotten engines are ready to power the Taurus 2 rocket.

"The engine is pretty robust and will definitely be able to run almost any duty cycle we can throw at it," Van Kleeck said in an interview Tuesday.

The February tests in Russia will mimic the loads the engine will see during a normal Taurus 2 launch, according to Van Kleeck.

When asked for the Taurus 2 and Cygnus spacecraft's most significant schedule-drivers, Culbertson cited avionics and the construction of ground systems.

"We're dealing with challenges in the avionics area, challenges in the launch site and test facility preparation, all of which is not unexpected, but we still have to keep our eye on it very closely," Culbertson said.

The Stennis E-1 test stand is currently expected to be finished in March, according to Culbertson. Stennis also hosts engine ground tests for the space shuttle and Delta 4 rocket.

All of Taurus's AJ26 engines will undergo acceptance testing at Stennis as they are shipped from Aerojet's headquarters to the launch site at Wallops Island, Va.

The Russian test site will conduct long-duration verification testing of the engine.

"They're set up so that we can do long-duration tests," Van Kleeck said. "We don't currently have an operating U.S. stand that allows us to do that. The tests we'll be doing down at Stennis are validation tests, so they're much shorter duration."

The delays in first stage engine testing are one of the primary difficulties now impacting the tight launch schedule for the Taurus 2.

"We're currently scheduled for a March 31, 2011, launch date," Culbertson said. "That's still our baseline. We have some schedule challenges we're dealing with, and if things go really, really well, we'll be able to make that date. If some of the threats become reality, then we'll probably have to adjust, but it's too early to tell that yet."

In December, the solid-fueled Castor 30 second stage for the Taurus 2 completed its first two-and-a-half minute test firing at the Air Force's Arnold Engineering Development Center in Tennessee.

"That test also went very well, met or exceeded all expectations," Culbertson said.

The Castor 30 second stage motor is to be replaced with a new high-energy liquid-fueled stage on Orbital's third cargo delivery mission to the space station.

The enhanced second stage and an upgraded Cygnus logistics module will fly on the final six flights of Orbital's eight-mission contract with NASA. The new upper stage is required for Orbital to meet its commitments to NASA, Culbertson said.

Orbital is currently in competitive sourcing for the new upper stage.

Van Kleeck said Aerojet is "interested" and "there are ongoing discussions" regarding the new Taurus 2 second stage. Aerojet currently provides the hypergolic AJ10-118K second stage engine for the workhorse Delta 2 rocket fleet.

The Delta 2 is due to be phased out at the end of 2011, about the same time Orbital would begin incorporating a new second stage for the Taurus 2 launch vehicle.

Aerojet and Orbital would not give details of their plans for a liquid-fueled upper stage.

"We have the basics of it, and we know the performance that we need, but the specifics of the stage itself...we'll make a decision on that early this year," Culbertson said.

Ground facilities at Wallops are being constructed simultaneously with Taurus 2 rocket and Cygnus spacecraft prep work.

An artist's concept of the Cygnus spacecraft approaching the International Space Station. Credit: Orbital Sciences

Builders are driving piles for the rocket's Horizontal Integration Facility at pad 0A along Virginia's Eastern shore. The pad's transporter and erector system is also being manufactured.

The launch pad should be ready to begin interface testing with the first Taurus 2 rocket this fall. Culbertson said the Taurus 2 pathfinder vehicle should arrive at Wallops by June from its manufacturers, Yuzhnoye and Yuzhmash in Ukraine.

The Cygnus spacecraft systems critical design review was kicked off earlier this month.

European engineers at Thales Alenia Space have already started constructing Cygnus pressurized cargo modules, which are based on the Multi-Purpose Logistics Modules that deliver equipment to the station on space shuttle missions.

Manufacturing of Cygnus service modules will begin this spring at Orbital's headquarters in Dulles, Va., Culbertson said.