United Technologies Corp. says it has agreed to sell its Rocketdyne unit to GenCorp Inc. for $550 million.

The Hartford-based industrial conglomerate made the announcement Monday morning, saying the transaction is expected to close in the first half of 2013.

Rocketdyne, a manufacturer of rocket engines and liquid-propulsion systems, has been part of UTC's Pratt & Whitney division for seven years.

UTC had previously said it planned to sell Rocketdyne and other businesses to raise $3 billion to finance its purchase of aerospace parts maker Goodrich Corp.