On Friday Scaled Composites issued an accident investigation update about last July’s propulsion system test accident that killed three company employees and injured three others. The statement does not indicate a cause of the accident, and notes that a Cal OSHA investigation that wrapped up in January did not determine a cause. The statement does note that Scaled is making a number of changes, including:
- Conducting increased compatibility testing between N2O and any materials that contact it in the tank and eliminate incompatible materials in the flow path;
- Revising cleaning procedures to further minimize the risk of contaminants in the system;
- Replacing the composite liner in the N2O tank with a metal tank liner;
- Diluting N2O vapor in the tank with Nitrogen or another inert gas to decrease its volatility and/or act as a pressurant;
- Designing additional safety systems for the N2O tank to minimize the danger due to tank overpressure; for example, a burst disk feature; and
- Increasing the amount of testing during the development program to demonstrate that these design changes, and any improvements to system components, prevent the sequence of events
that led to the accident.
The statement does appear to indicate that Scaled is continuing with a nitrous hybrid propulsion system for SS2.