Hercules Aerospace Co. announced Friday that it is part of a joint venture to build a new type of rocket that would be launched from an airplane to put small satellites into orbit.

The rocket was described as the first all-new unmanned launching craft to be produced in this country in two decades.Managers of the project confirmed earlier reports that the Defense Department wanted to test the innovative rockets for use in deploying lightweight satellites for reconnaissance, communications and other military missions. They said the rockets would also be available for non-military launchings by government and private industry.