launch into (something)
To begin doing something, often excitedly. Don't ask Grandpa about the weather unless you want him to launch into a full analysis of the Farmers' Almanac.
launch into something
to start in doing something. Now, don't launch into lecturing me about manners again! Tim's mother launched into a sermon about how to behave at the dinner table.
launch into
v. To start saying or doing something enthusiastically; plunge into something: The professor launched into the topic after a brief introduction.