DISTRIBUTION A Approved for public release, distribution is unlimited 1 AIAA-2005-3935 Joint Propulsion Conference, Tucson, Arizona 2005 Modeling of Radiation Heat Transfer in Liquid Rocket Engines M.H. Naraghi * Department of Mechanical Engineering, Manhattan College, Riverdale, NY 10471 S. Dunn † and D. Coats ‡ SEA Inc., 1802 North Carson Street, Suite 200 Carson City, NV 89701 This paper presents a radiation heat transfer model for liquid rocket engines. The radiation model is conjugated to an existing conductive and convective model for liquid rocket engines (TDK-RTE). The new TDK-RTE model is used to analyze the effects of radiative heat transfer on thermal characteristics of two regeneratively cooled rocket engines. One of the engines is the Space Shuttle Main Engine (SSME), which uses liquid hydrogen and liquid oxygen as propellant and liquid hydrogen as coolant. The other engine has RP1 (a hydrocarbon fuel) and liquid oxygen as propellant and liquid oxygen as coolant. It is shown that the gas radiation has some effect on the wall temperature for the SSME and a small effect on its coolant flow characteristics. For the RP1-LO 2 engine, however, the gas radiation significantly changes the wall temperature and coolant flow characteristics. It is also shown that in order to maintain reasonable wall temperatures and cryogenic coolant flow temperature and pressure, the design of cooling channels is significantly influenced by radiation. I. Introduction Thermal analysis is an essential and integral part of the design of rocket engines. The need for thermal analysis is especially important for reusable engines, where an effective and efficient cooling system is crucial in extending the engine life. The rapid and accurate estimation of propulsion system thermodynamic heat loads and thermal protection system effectiveness is required if new vehicle propulsion concepts are to be evaluated in a timely and cost effective manner. In high-pressure engines hot-gas temperatures are extremely high (approximately 7000°R). It is therefore essential to be able to estimate the wall temperature and ensure that the material can withstand high temperatures. Furthermore, an accurate thermal model enables an engine designer to modify the cooling channel configuration for optimum cooling at regions of high thermal loads. It should be noted that the under-cooling of an engine could result in catastrophic failure, while over-cooling would result in loss of engine performance. This loss of performance may be the result of higher coolant compressor requirements, or due to decreased * Professor, mohammad.naraghi@manhattan.edu , Senior Member AIAA. † Vice President, stu@seainc.com , Member AIAA. ‡ President, doug@seainc.com . Associate Fellow AIAA.