A pair of SuperDraco engines firing at the same time is far quieter than I thought it would be. The dual firing is part of SpaceX pad abort testing for the rocket engines, ensuring both engines can simultaneously ignite and throttle if they need to carry the Crew Dragon to safety.
Top image: SuperDraco engine during qualification testing. Credit: SpaceX
The SuperDraco engines will be used for the Crew Dragon, the SpaceX contribution to NASA's commercial crew program to transport astronauts to the space station via space taxis instead of hitching a ride on the Russian Soyuz. Four pairs of the engines will be mounted to the sides of the capsule for a total of eight engines as part of the capsule's launch abort system. During the launch, the rockets will only fire if a critical failure aborts the launch after the main rocket fires, and the crew needs to be boosted safely away from the mess.
SuperDraco engine pair. Image credit: SpaceX
The SuperDraco engines produce 16,000 pounds of thrust, can throttle, and be started multiple times, giving astronauts a great deal of control for their launch abort system. For a bit of bonus trivia, the engines are manufactured using metal laser sintering: they're 3D printed.
The next major step for the engines is a flight test under NASA's supervision Cape Canaveral Air Force Station in Florida. The development flight is part of the Commercial Crew Integrated Capability (CCiCap) agreement between NASA and SpaceX.
Want something louder? Check out the hot fire tests for the repurposed RS-25 rocket engines.