SpaceX is busily preparing for its final uncrewed flight test with the Falcon 9 and Dragon capsule before it sends the first astronauts to the International Space Station (ISS). In many of SpaceX’s launches, the company does all it can to recover the Falcon 9 first stage for reuse, but it’s going to sacrifice the rocket this time, SpaceX CEO and consummate showman Elon Musk described it as being “destroyed in dragon fire.”
In recent days, SpaceX has delivered its latest Crew-capable Dragon spacecraft to Kennedy Space Center Launch Complex 39. The goal of the final test will be to demonstrate that the Dragon capsule’s SuperDraco engines will function as an in-flight abort system. The company has already shown the SuperDraco engines can wrench the Dragon spacecraft away from the Falcon 9 on the ground, but the in-flight abort will be the ultimate test of its capabilities. NASA doesn’t mandate this test as part of the Commercial Crew Program, but SpaceX has good reasons for doing it.
Most rockets with in-flight abort systems rely on solid rocket boosters to do the job. These motors (like the side boosters on the Space Shuttle and upcoming SLS) fire at maximum thrust until they expend their fuel and are then discarded. SpaceX has plans for propulsive landings with the Dragon capsule in the future, so it designed the SuperDraco engines to be liquid-fueled (hydrazine and nitrogen tetroxide). This decision cost SpaceX dearly when a Dragon capsule exploded last year during ground testing. An investigation found that a leaky valve supplying the engine had allowed nitrogen tetroxide to accumulate in the helium pressurization system. This caused the titanium check valve to fail, resulting in an explosion.
Destroyed in Dragon fire
— Elon Musk (@elonmusk) January 12, 2020
SpaceX is currently aiming for a January 18th launch. The Dragon spacecraft won’t reach orbit, though. This test is intended to show that the SuperDraco engines can successfully pull the Dragon away from the Falcon 9 during the most challenging part of the ascent, known as Max Q. This is the point at which velocity and air pressure combine to create the highest drag on the rocket’s windward-facing parts. If the SuperDraco engines can blast the Dragon clear at this moment, it can do so at any time during launch.
The Falcon 9 core for this launch carries the designation B1046 — it was the very first Block 5 variant of the Falcon 9 to fly. Musk says the company’s engineers attempted to design a way to save the booster, but there was just no way. It completed three flights in 2018, landing after each one, but this mission will be its last. SpaceX expects the booster to be badly damaged by the launch abort system. Despite losing B1046, this test should pave the way for SpaceX’s first crewed launch in the coming months.