Northrop Grumman, the military contractor, said that it planned to complete its $7.8 billion takeover of TRW Inc. on Dec. 11 and did not expect the government to require the sale of any businesses. Completion of the deal depends on Northrop's obtaining a consent decree with the Department of Justice intended to ensure fair and open competition in the space electronics business, the two companies said yesterday in a joint statement. Based on a draft of the agreement, Northrop officials say they believe that they have Defense Department clearance for the deal and that they will agree on terms of a final decree with the Justice Department in time to allow shareholder votes on the deal on Dec. 11. Northrop announced its plan to buy TRW, which is based in Cleveland, in July. In addition to paying $7.8 billion in stock, it would also assume about $4 billion in TRW debt. The transaction has been under scrutiny by the Defense and Justice Departments amid concerns from competitors, particularly Lockheed Martin, that a combined Northrop-TRW would control the manufacture of space and satellite components.