WASHINGTON — Dulles-based satellite and rocket maker Orbital ATK says its stockholders have overwhelmingly approved the company’s acquisition by Falls Church-based Northrop Grumman.

The $9.2 billion merger, announced in September, includes $7.8 billion in cash and the assumption of $1.4 billion in Orbital ATK debt.

The merger is now expected to close in the first half of 2018, and will create a company with nearly 80,000 employees worldwide.

“The acquisition creates substantial value for our stockholders and enhances our capability to accelerate product development and technology,” said Orbital ATK chief executive David Thompson.

“The transaction also enables our employees to benefit from new opportunities and career paths as part of a larger and more diverse aerospace and defense company.”

Orbital ATK itself is the result of the 2015 merger of Orbital Sciences Corp. and the aerospace and defense groups of Alliant Techsystems Inc.