Use Cosmic energy
The earth is a dynamo, space is a sea of energy radiating. It's possible to build devices that are basically an antenna to receive this energy and some diodes and electronics to direct it. Most of these things are patented and kept from the public under national security concerns. This goes back to the work of tesla, and before that things like the pyramids and megalithic structures found everywhere around the world and under every ocean. Turns out there was a worldwide grid built to machine precision where structures across great distances would create resonant points. The earth itself provides power it has a core of spinning iron and a magnetic feild bubble that's constantly bombarded with stuff...so put some electrodes on it, and get rid of oil and the current electrical grid, that they knew we never needed in the first place. Convert the oil rigs into space cannons since the tech exists already and is cheaper than a rocket. Then convert all military hardware and spending to peaceful space exploration to get the resources we need from space.