Following a successful demonstration mission of its Crew Dragon spacecraft in March, SpaceX has been preparing that vehicle for a critical launch abort test this summer. During this upcoming test flight, after launching from Florida on a Falcon 9 booster, the Dragon will fire its powerful SuperDraco engines to show that the spacecraft can pull itself safely away from the rocket in case of a problem with the booster.
On Saturday, as part of preparations for this abort test, the company experienced some sort of anomaly. According to a company spokesperson: “Earlier today, SpaceX conducted a series of engine tests on a Crew Dragon test vehicle on our test stand at Landing Zone 1 in Cape Canaveral, Florida. The initial tests completed successfully but the final test resulted in an anomaly on the test stand. Ensuring that our systems meet rigorous safety standards and detecting anomalies like this prior to flight are the main reasons why we test. Our teams are investigating and working closely with our NASA partners.”
It is not immediately clear how significantly this incident will affect SpaceX as it works toward Dragon’s first crewed mission, which will carry astronauts Doug Hurley and Bob Behnken to the International Space Station. Previously, sources have said that flight could occur by about October under ideal conditions. If the problems were serious, Saturday’s accident may substantially delay this schedule—although in the past SpaceX has shown a propensity to rapidly diagnose failures and return to flight quickly, with just 4.5 months of downtime after a rocket failure in September, 2016.
SpaceX has been developing SuperDraco thrusters for the better part of a decade to enable human flights on board Dragon. There are four “pods” of two engines each situated around the Dragon capsule, and each SuperDraco engine has a thrust of 16,000 pounds. Testing of the SuperDracos began in early 2012, using various thrust cycles on a test stand at SpaceX’s rocket development facility in McGregor, Texas.
The engines burn hypergolic propellants—monomethylhydrazine, as a fuel, and nitrogen tetroxide as an oxidizer. These are fairly toxic compounds, but unlike other “cleaner” rocket fuels, they are more easily storable both on the ground and in space.
These escape systems are one of the most difficult aspects of spacecraft development, as they must function during the most dynamic moments of spaceflight. NASA will no doubt scrutinize this failure closely before it allows its astronauts to fly in Dragon. Escape systems have previously caused problems as part of NASA’s Commercial Crew program, which has provided funds to private companies for access to low-Earth orbit. In June, 2018, as Boeing prepared its Starliner spacecraft for a test of its emergency escape system, a propellant leak occurred near the end of an engine test firing, and seriously damaged the service module. Boeing had intended to complete the test of its abort system last summer, but has yet to reschedule the flight 10 months later, apparently due to complications from this accident.
Although such escape systems are rarely used, they are the last line of defense when an emergency occurs. In the event of a rocket failure, such as that which occurred last October with a Russian Soyuz vehicle during a crew launch to the International Space Station, they are truly the difference between life and death.