Drogue Failure Result of "Inconsistent Wiring Label Definitions"

A recent return mission carrying samples from the asteroid Bennu raised eyebrows at NASA when a drogue chute failed to deploy during the landing sequence.

During the return of the OSIRIS-REx mission, a drogue was supposed to deploy at 100,000 feet to stabilize and slow the capsule during a 5-minute descent down to 10,000 feet. Instead, the signal triggered a different reaction at 100,000', jettisoning the parachute prior to it even deploying. With its retention cord cut, the main parachute was forced to take the entire deceleration load on its own. Luckily, NASA says, the margins as designed were sufficient to protect the Bennu sample.

The culprit for the drogue mishap turns out to be inconsistent verbiage in the use of "main" between two different subsystems. "On the signal side, “main” meant the main parachute. In contrast, on the receiver side “main” was used as a reference to a pyrotechnic that fires to release the parachute canister cover and deploy the drogue. Engineers connected the two mains, causing the parachute deployment actions to occur out of order," said the NASA investigation.

From here, the system will be tested again in situ, using the same hardware that misfired on the OSIRIS mission. The sample remains safely nestled in "one of the glove boxes inside the Johnson Space Center", awaiting the curation team's attention. Once complete, the equipment can be turned over for testing.

FMI: www.nasa.gov