Software for Designing Model Rockets for Base-Heating Tests

Marshall Space Flight Center, Alabama

The Impulse Combustion Excel (ICE) computer program was developed to facilitate and accelerate the design and analysis of subscale rocket engines for use in base-heating tests. Such tests are performed on the ground to obtain data for estimating the heating effects of hot exhaust plumes on the aft regions of full-scale rockets during ascent. The computer program is so named because typically, a base-heating test involves impulse combustion — short-duration (of the order of 100 ms long) hot firing using flight propellants. Heretofore, the design of the subscale engines and base-heating tests has been a difficult, time-consuming, iterative process. ICE can be expected to reduce the testing times and costs and to yield improved designs. ICE can be used to design models to be tested in both wind tunnels and vacuum tanks.

ICE is a spreadsheet code that provides all of the parametric data used in the geometric design, heating analysis, and system analysis for many propulsion systems. The power of ICE lies in the capability to change only one or all input variables to adjust a design. ICE can also be used as an educational tool for learning the effects of various parameters on an entire design.

ICE eliminates a week or more of manual calculations for each model configuration. The program incorporates engineering relations that have been used previously but, until now, have been found in several reports and documents and never gathered into one consistent form or location. In addition, ICE incorporates an expanded set of features including (1) a procedure for determining the loss of energy resulting from internal transfer of heat to cold metal surfaces, (2) a methodology for sizing a combustion chamber and associated ports of one or more engine(s), (3) a valve-selection sheet, and a (4) historical design data base.

The spreadsheet contains the following pages: (1) input, (2) Venturi sizing, (3) charge-tube and buffer-gas-tube lengths, (4) system start time, (5) injector design, (6) combustor design, (7) combustor/nozzle heating, (8) surface heating, (9) valve pressure drop, and (10) historical design data. When the input page is filled out, ICE automatically generates the specifications necessary for computer-aided design (CAD) of a model. The CAD numerical model can be translated into an image of a solid model for electronic display and visual inspection; alternatively or in addition, a material model can be grown from the numerical model by use of stereolithography.

This work was done by Carl D. Engel of Qualis Corp. for Marshall Space Flight Center. For additional information, please contact the company at (256) 533-9282.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to