WASHINGTON — Orbital Sciences Corp. is accusing a contractor of holding “hostage” hardware needed to launch a NASA-chartered cargo delivery to the international space station next April and is suing to recover the parts.

The lawsuit, filed Oct. 21 with the U.S. District Court for the Eastern District of Virginia, centers around a roughly $2 million contract Orbital Sciences awarded in 2013 to defendants Integrated Systems and Machinery of Smithtown, New York, and its owner, Kevin Huber. The contract called for Huber’s company to build new gimbals and cylinders for the hydraulic system used by the slow-moving, truck-like Transporter Erector vehicle that hauls Orbital’s Antares cargo rocket and Cygnus space freighter out of their Wallops Island, Virginia, hangar and raises them vertical at their Mid-Atlantic Regional Spaceport launch pad over a kilometer away.

Orbital’s third cargo run to the ISS — which at press time was still slated to launch Oct. 27 — can proceed without the withheld hardware. However, Orbital is obligated under an agreement with the Mid-Atlantic Regional Spaceport’s host state to upgrade the Transporter Erector before launching its fourth contracted cargo run, the debut of a bigger, heavier Cygnus cargo tug.

That mission is slated for April 1, according to an internal NASA launch manifest. Orbital says it will take about four months to install the new Transporter Erector components. The upgrades will enable the Transporter Erector’s hydraulic system to handle an Antares/Cygnus stack that will continue to grow heavier through its own long-planned incremental upgrades.

Orbital is “ready and willing to pay for the equipment and Data so Orbital may complete the upgrade of the [Transporter Erector] as necessary to accomplish future launches of the Antares, but Defendants are holding the vital and unique equipment hostage,” Orbital said in its complaint.

As evidence, Orbital appended to its complaint a July 14 email in which Huber told Keith Fava, Orbital’s principal integration and test engineer, that the hardware was mostly complete, but that he would not turn it over because of “unresolved contractual matters” between Orbital and Integrated Systems and Machinery. Huber also wrote that he would “be ready, on the spot, to do it if somehow the contractual issue resolves itself.”

Huber, under a separate lawsuit filed last December, is accused by his former employer Advanced Fluid Systems — the York, Pennsylvania, company that built the Transporter Erector’s hydraulic system under a 2009 contract with the Virginia Commercial Space Flight Authority — of stealing trade secrets in order to win the Orbital upgrade work for his new company.

Orbital said in its Oct. 21 complaint it had no knowledge of Huber’s alleged wrongdoing when it gave his company a contract in 2013.

Neither Orbital spokesman Barron Beneski nor Huber responded to emails requesting comment by press time Oct. 24. Orbital wants its Transporter Erector parts turned over immediately, and its contract with Integrated Systems and Machinery voided.

Meanwhile, Advanced Fluid Systems has dropped Orbital from the lawsuit it filed last year to recover company funds it used to complete the Transporter Erector and monetary damages related to the lost follow-on work. Orbital took ownership of the Transporter Erector and other ground support equipment in 2010 under a $42 million deal to provide the Virginia Commercial Space Flight Authority with cash to cover overruns incurred during construction of the Antares launch pad.

Court documents from May show Advanced Fluid Systems and Orbital settled out of court for terms undisclosed. However, the Pennsylvania company is still seeking damages from the other defendants, including Huber, Integrated Systems and Machinery and several other firms involved in the alleged contract poaching.