Destruction of the 46-acre Aerojet Rocketdyne plant in Canoga Park started this week, with work expected to last up to a year. The demolition will make way for a 4,000-unit residential development with a budget of $3 billion. It will be owned by United Technologies Corp., the Hartford, Conn.-based defense contractor and former parent company of Aerojet Rocketdyne. The project will also feature retail, hotel and 1.2 million square feet of office space. It will have more than 10,000 parking places, according to the website of Boston Global Investors, the company hired by United Technologies to design the project. The 61-year-old aerospace plant produced rocket engines for NASA’s Gemini, Mercury and Apollo programs, as well as the Space Shuttle.