Defense giant Lockheed Martin continued its trend of acquiring small companies with focused capabilities. This week, the contractor bought a Massachusetts-based energy start-up named Sun Catalytix for an undisclosed sum and also wrapped up its $61 million purchase of Astrotech Space Operations, a satellite launch preparation company. Both businesses are wholly-owned subsidiaries of Lockheed.

The company’s purchase of Sun Catalytix is its latest move into the energy market. Last year, Lockheed said it was partnering with a Chinese company to build a plant off the coast of southern China to convert the ocean’s thermal energy to electricity.

Sun Catalytix was founded in 2009 by Daniel Nocera, a former Massachusetts Institute of Technology chemistry professor, who now runs a research laboratory at Harvard. It received a $4 million contract from the Energy Department in 2010 and a $9.5 million round of funding from Indian company Tata Ltd. and Polaris Ventures the same year.

The start-up gained attention for developing technology that used inexpensive materials to split water molecules and generate renewable energy, known as the “artificial leaf.” Here’s a video of Nocera explaining how it works:

In recent years, the company turned its attention to energy storage, and has since created a low-cost flow battery, which is a type of rechargeable battery.

The start-up’s work on the flow battery was what made it attractive to Lockheed Martin, said Joe Stout, a company spokesman. Lockheed plans to use the technology in its microgrid, which is a small-scale network that can manage energy usage on facilities such as a military or nuclear base, Stout said.

Sun Catalytix will retain its Cambridge office and a majority of its employees have transferred to Lockheed Martin. The company has been renamed Lockheed Martin Advanced Energy Storage.