Webb Space Telescope Problems: Excessive Voltage, Wrong Solvent & Loose Nuts

Artist’s impression of James Webb Space Telescope. (Credit: NASA)

NASA established the Independent Review Board (IRB) in April to evaluate the space agency’s $8 billion James Webb Space Telescope (JWST). The report, released last month, revealed a number of eye opening details about problems that NASA and the prime contractor, Northrop Grumman Aerospace Systems (NGAS), have been experiencing in building the telescope and managing the program. Below are some key excerpts.

Independent Review Board Report
NASA James Webb Space Telescope

Full Report

Selected Excerpts

There have been several JWST Project problems due to human-induced errors that had substantial cost and schedule impact. In one case, an improper solvent was used to clean propulsion system valves that had been stored. The error was a failure to check with the valve vendor to ensure the solvent to be used was recommended and would not damage the valves. The valves had to be removed from the spacecraft, repaired or replaced, and reinstalled.

Another human-induced error was improper test wiring that caused excess voltage to be applied to transducers. The error resulted from an improper interpretation of a process step. The error should have been detected by the inspector, who did not inspect, but relied on the technician’s word that he had done the wiring correctly.

To address a risk that fasteners for sunshield membrane covers might snag the membrane, the fastening lock nuts were tightened only to be flush with their bolts. Unfortunately, this compromised the locking mechanism, and after the test, loose hardware was found in the lower area of the spacecraft.

The Webb IRB recommends that NGAS review processes/procedures to be sure they are current, accurate and implementable. The Webb IRB has noted two examples of human induced errors resulting from incomplete procedures (e.g., requiring that the solvent selected for cleaning valves be recommended by the vendor) or processes that could be misinterpreted (e.g., the improper wiring that caused excess voltage to be applied to transducers). Both examples resulted in substantial schedule and cost increases.

The Webb IRB recommends that individuals at the working level be trained to understand that, on JWST, seemingly small errors produce large consequences.

The Webb IRB recommends that individuals scheduled to perform tasks on the observatory be properly trained, capable, and certified to perform those tasks and properly supervised. Those not properly certified must not be allowed to perform tasks that could result in damage to the system. This is an especially critical discipline to maintain, particularly on second or third shift activities and when schedule pressure exists (which will likely always be the case on JWST Integration & Test (I&T) and when supervision may be thin.

The Webb IRB has noted lapses in individual accountability that have substantially increased schedule and cost and, potentially, increased risk. The Webb IRB recommends that discipline be continually instilled in the workforce such that people feel accountable and own what NGAS is relying on them to do. A signature sign-off must mean something. With this ownership mindset, people must believe they are empowered to call a halt to the execution of a process if it doesn’t look right or they don’t completely understand what they are being called upon to do.

The Webb IRB recommends that NGAS management maintain a failure-proof safety net to ensure mission success. This safety net encompasses testing, independent analysis, and inspection to ensure that the system design meets all of its requirements and any workmanship errors are detected and corrected.

The propulsion valve issue mentioned before and most recently the sunshield fasteners that came loose during acoustic testing of the Spacecraft Element are two examples of problems that were discovered later in the development phase than they should have been, with subsequent large impacts on cost and schedule for the remedial actions required. These experiences raise the possibility of other such issues remaining in the design at this stage. To attack this, the Webb IRB recommends [Goddard Space Flight Center (GSFC)] and NGAS conduct an audit to identify potential embedded problems still remaining in the observatory.