NASA researchers recently demonstrated successful real-time fault detection
and isolation of a virtual main propulsion system at NASA’s Glenn Research
Center, Cleveland. The goal of this research was to mature and demonstrate
key Integrated Vehicle Health Management (IVHM) technologies–one of several
technologies that are involved in NASA’s Space Launch Initiative (SLI), an
Agencywide effort to significantly increase crew safety while reducing
payload launch costs.

Using a detailed simulation of a vehicle propulsion system to produce
synthesized sensor readings, the team of researchers demonstrated that
advanced diagnostic algorithms, running on actual flight class computers,
can, in real time, successfully diagnose the presence and cause of faults.

This demonstration was conducted as part of the NASA Propulsion IVHM
Technology Experiment, or PITEX. It was a joint effort including Glenn, Ames
Research Center, Moffett Field, Calif. and Kennedy Space Center, Fla. The
experiment supports work for the SLI IVHM project contracted to Northrop
Grumman of El Segundo, Calif.

Glenn researchers developed a detailed simulation of a main propulsion feed
system, which they ran under both nominal and fault conditions in order to
generate time histories of propulsion system parameters. Noise was
superimposed on the simulation output to provide realistic sensor signals.
Typical propulsion system failures such as valves sticking open or closed,
regulator problems, and sensor and microswitch failures were injected at
various points in a simulated mission.

The simulated data were fed, in real time, to IVHM software running on a
computer that is a commercial grade version of actual flight hardware. The
computer hardware was designed and assembled by Kennedy Space Center.

“In all cases, the PITEX diagnostic software detected and isolated the
injected fault correctly,” said Claudia Meyer, research and technology lead
at Glenn.

In addition, resource utilization tests were performed to measure the
real-time performance of the diagnostic software on the flightlike hardware.
Data revealed that resources were largely underutilized, indicating that the
diagnostic system could be expanded to cover additional components.

The PITEX diagnostic solution features monitor software, which processes the
raw sensor data and an Ames-developed, model-based diagnostic software –
Livingstone – that detects and isolates anomalies. Livingstone uses a
qualitative model of the system to predict the expected state; system-level
reasoning is performed to resolve differences between the observed and
expected states.

“These efforts are the culmination of many years of research,” said Harry
Cikanek, manager of the Space Transportation Project Office at Glenn. “PITEX
application of these advances represents an essential step on the path to
meet Program goals for safety and cost.”

In continuing work, the PITEX diagnostic solution is being migrated to
Northrop Grumman’s IVHM Virtual Test Bed (IVTB). In the IVTB, a broad range
of vehicle subsystem health managers, in addition to propulsion, will be
considered, and the benefits of coordinating the subsystem health managers
through area and system-level health managers will be demonstrated.

The Space Launch Initiative is NASA’s technology research and development
program aimed at dramatically increasing safety and reliability and reducing
the cost of a 2nd generation reusable launch vehicle. All NASA’s field
centers and the Air Force Research Laboratory are actively participating in
the Space Launch Initiative and are vital to its success. NASA’s Marshall
Space Flight Center in Huntsville, Ala., leads the Space Launch Initiative
for NASA’s Office of Aerospace Technology.

Further information on the Space Launch Initiative can be found at the
following web sites: