Mr. Musk dug into his companies’ budgets, preferring to cut too much rather than too little and to deal with the fallout later. Under Donald Trump, he is set to apply those tactics to the U.S. government.

Over the last 16 years, Musk's business deals with the government total nearly $20 billion, according to federal contracting data.

Elon Musk has slept on Tesla's factory floor and instructed SpaceX employees to walk out of meetings where they aren't adding value.