NASA awarded a total of $30.7 million in follow-on grant money to 39 small businesses in the second phase of a Small Business Innovation Research (SBIR) competition that began in 2011, the space agency announced April 25.

The awards just announced are worth up to $750,000 over two years, according to a NASA press release. The 39 companies that received Phase 2 awards were culled from a field of 44 competitors that received six months’ worth of study money in the program’s first phase.

Phase 2 awards for this round of SBIR are spread across four research and development categories: aeronautics research, exploration systems, science and space operations. Funded projects include iodine-powered thrusters for in-space propulsion, heat pipes for small nuclear fission reactors and a harsh-environment gas sensor array for making atmospheric measurements on Venus.

California had the largest number of SBIR winners this time around: 13 companies from that state were funded. Massachusetts came in second with six funded companies.

SBIR is a three-phase competitive program aimed at jump-starting technology proposals from U.S. small businesses. Only the first two phases may be paid for with a portion of the SBIR funds that all federal agencies with research and development budgets must set aside every year. Phase 3 is aimed at getting technology developed in the prior phases into the hands of a commercial or government customer.