SpaceX test-fires the engines that could take humans to Mars

SpaceX has conducted its first firing test of its Raptor engine, the powerful propulsion system that the company aims to use to take humans to Mars. SpaceX boss Elon Musk tweeted pictures of the tests late last night, sharing one image that showed a steady stream of flame emanating from the engine, and another showing "Mach diamonds" — patterns formed in the exhaust plumes of supersonic craft.

Musk has been has been fairly vague on Raptor specifications so far, but tweeted a few extra details after last night's tests, confirming production goals and chamber pressure. Previously the SpaceX CEO has indicated that Raptor engines will deliver about 500,000 pounds of liftoff thrust — about as much as the Space Shuttle's main engines — and...