Original Date: 04/26/1999
Revision Date: 01/18/2007
Best Practice : Plume Induced Environments
Plume induced environments are the heated areas on the launch vehicle’s base regions caused by propulsive engine plumes. The ability to locate and characterize these hot spots is critical to ensuring a safe and successful mission. To monitor these areas, Marshall Space Flight Center (MSFC) employs an integrated methodology that utilizes improved and integrated engineering codes; 3-D computational fluid dynamics; and modernized short duration convective and ground radiation test data. The previous method was a non-integrated system based on engineering and empirical techniques derived from 1960s and 1970s launch vehicles. The change in physical design of today’s launch vehicles dictated the need for a new system which could accurately predict and monitor thermal hot spots.
Two primary heating phenomena are associated with plumes: (1) radiation heating where hot plume gases radiate at all altitudes, and (2) convection heating where hot plume gases are re-circulated around the base of the launch vehicle. Analysis of the heating environment will involve 20 to 200 vehicle body point measurements that are influenced by variables including engine gimbal angle, trajectory changes, and angle of attack. Figure 2-2 illustrates a typical body point distribution of the X-33 Reusable Launch Vehicle (RLV) for plume heating calculations.
Since the 1960s, engineering codes have been a major area of development. Noted improvements include user input and output simplified by graphical user interfaces; artificial intelligence analogs added to mesh density selection and interpret result validity; integration of output data so that it automatically transforms into input for subsequent code; and acceptance of computational fluid dynamic plumes as input for radiation codes. Today’s engineering codes involve band model gaseous radiation; nozzle and high altitude plume flowfields; reverse Monte Carlo radiation; the chemical equilibrium code; and the viscous shear layer of the plume.
The improvement of engineering codes and the use of faster, more powerful computers greatly aid plume environmental engineers in their work. As a result, MSFC reduced analysis time from weeks to hours, and significantly decreased testing costs from $6 million in the 1970s to $750,000 today.
Figure 2-2. Typical X-33 Body Point Distribution
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