Elon Musk achieves technological synergy across energy and aerospace through his three companies: SpaceX, Tesla, and SolarCity.

In June 2002, Elon Musk invested $100 million to establish Space Exploration Technologies Corp. (SpaceX). His goals were to reduce space launch costs through reusable rocket technology and advance plans for Mars colonization. The company initially operated from a warehouse in El Segundo, California, naming its first rocket Falcon 1. Between 2006 and 2008, Falcon 1 suffered three consecutive launch failures, pushing SpaceX to the brink of insolvency. A breakthrough came on September 28, 2008, when the fourth Falcon 1 launch successfully reached orbit, marking the world's first privately developed liquid-fueled rocket to achieve orbital flight. That December, SpaceX secured a landmark $1.6 billion NASA contract to resupply the International Space Station. On December 8, 2010, a Falcon 9 rocket carrying the Dragon spacecraft completed its inaugural flight and safe return, achieving the first private orbital spacecraft recovery. A major milestone followed on December 21, 2015, when a Falcon 9 booster executed humanity's first successful soft landing and recovery of an orbital-class rocket on land.

Musk invested $6.3 million in Tesla Motors (now Tesla, Inc.) in 2004, becoming its Chairman. Tesla's first electric vehicle, the Roadster, entered mass production in 2008. However, crippling R&D cost overruns combined with the global financial crisis brought Tesla to the edge of bankruptcy. Musk personally invested his last $40 million to sustain operations. The company stabilized after its June 2010 Nasdaq IPO, raising $184 million and becoming the first U.S. carmaker to go public since 1956. Tesla delivered its premium Model S sedan in 2012, achieving cumulative sales exceeding 160,000 units by 2015. The Model X SUV followed in 2015.

Musk co-founded photovoltaic company SolarCity with his cousin Lyndon Rive in 2006. The company specialized in solar energy system design, installation, and financing, primarily through leasing arrangements. Its offerings formed an integrated energy ecosystem with Tesla's electric vehicles and Powerwall battery storage, creating a "generation-storage-consumption" loop. When hedge funds shorted SolarCity and raised financial risk concerns in August 2015, Musk invested $5 million to bolster the stock price. By 2015, SolarCity had become the largest residential solar provider in the United States.

From 2002 to 2015, SpaceX secured over $8 billion in U.S. government funding, including $7.2 billion in NASA contracts and $960 million in Air Force grants. Crucially, NASA provided core technical support spanning rocket design and materials analysis. SpaceX's innovations dramatically reduced launch costs; by 2012, a single Falcon 9 launch cost $57 million – less than half the $137 million price of Europe's Ariane rocket, representing approximately one-tenth of the industry's historical average cost.