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Steady-State and Transient Simulations

Sierra Engineering generates computer models that accurately predict and validate engine components and fluid properties.

Typical transient analyses estimate overall engine response over mission environments and provide preliminary valve sequencing for engine startup and shutdown.

These predictions benefit rocket engine and high-energy laser programs by:
  • Reducing the amount of hot fire tests required to characterize the test article
  • Determining valve sequencing to optimize test results and minimize mission environments
  • Reducing the probability of catastrophic engine failure during start
  • Predicting potentially catastrophic events such as LOX geyser or water hammer
  • Predicting feed system stability
  • Designing control algorithms
Sierra utilizes the ROCket Engine Transient Simulation (ROCETS) program to perform system simulations.  This program is suppied and maintained by NASA MSFC.

Sierra Engineering has performed analysis on  a multitude of rocket engines configurations:
  • pressure-fed and pump-fed
  • employing staged combustion cycles as well as gas generator cycles
  • using different types of propellants including cryogens, such as liquid oxygen-hydrogen or liquid oxygen/RP-1, and earth storables

ROCETS has been used effectively to simulate all types of non-Rocket fluid systems as well. For example, ROCETS was used to simulate an NH3 and Ethylene Glycol cooling system along with developing the proportional, derivative, and integral gains for the control valves.

ROCETS is effectively used as the "heart" of all our system optimizations.  The program is able to generate steady-state solutions typically within one or two seconds.  Transient runs depend on the configuration, valve timing, and mission time, but typically require between several minutes to several hours of CPU time. 

A few of the latest changes to ROCETS include improved saturation property lookup tables, the ability to simulate fully lit, partially lit, and unlit mixed combustion propellants, and inerts mixed with propellants.