Garbage-In Garbage-Out (GIGO): The Use and Abuse of Combustion Modeling
and Recent U.S. Spacelaunch Environmental Impacts
PattiMichelle Sheaffer
The Aerospace Corp. (ret.), The Aerospace Corp. (ret.), The Aerospace Corp. (ret.), The Aerospace Corp. (ret.), The Aerospace Corp. (ret.), The Aerospace Corp. (ret.), The Aerospace Corp. (ret.), The Aerospace Corp. (ret.), The Aerospace Corp. (ret.)
Corresponding Author:pattimichelle000@gmail.com
Author ProfileAbstract
Although adequately detailed kerosene chemical-combustion Arrhenius
reaction-rate suites were not readily available for combustion modeling
until ca. the 1990’s (e.g., Marinov [1998]), it was already known
from mass-spectrometer measurements during the early Apollo era that
fuel-rich liquid oxygen + kerosene (RP-1) gas generators yield large
quantities (e.g., several percent of total fuel flows) of complex
hydrocarbons such as benzene, butadiene, toluene, anthracene,
fluoranthene, etc. (Thompson [1966]), which are formed concomitantly
with soot (Pugmire [2001]). By the 1960’s, virtually every
fuel-oxidizer combination for liquid-fueled rocket engines had been
tested, and the impact of gas phase combustion-efficiency governing the
rocket-nozzle efficiency factor had been empirically well-determined
(Clark [1972]). Up until relatively recently, spacelaunch and
orbital-transfer engines were increasingly designed for high efficiency,
to maximize orbital parameters while minimizing fuels and structural
masses: Preburners and high-energy atomization have been used to
pre-gasify fuels to increase (gas-phase) combustion efficiency,
decreasing the yield of complex/aromatic hydrocarbons (which limit
rocket-nozzle efficiency and overall engine efficiency) in
hydrocarbon-fueled engine exhausts, thereby maximizing system launch and
orbital-maneuver capability (Clark; Sutton; Sutton/Yang). The rocket
combustion community has been aware that the choice of Arrhenius
reaction-rate suite is critical to computer engine-model outputs.
Specific combustion suites are required to estimate the yield of
high-molecular-weight/reactive/toxic hydrocarbons in the rocket engine
combustion chamber, nonetheless such GIGO errors can be seen in recent
documents. Low-efficiency launch vehicles (SpaceX, Hanwha) therefore
also need larger fuels loads to achieve the same launched/transferred
mass, further increasing the yield of complex hydrocarbons and radicals
deposited by low-efficiency rocket engines along launch trajectories and
into the stratospheric ozone layer, the mesosphere, and above. With
increasing launch rates from low-efficiency systems, these persistent
(Ross/Sheaffer [2014]; Sheaffer [2016]), reactive chemical
species must have a growing impact on critical, poorly-understood
upper-atmosphere chemistry systems.