(Georgia Institute of Technology, 1999-12-09)
Sorensen, Kirk
While in the conceptual design phase of launch vehicles, aerodynamic data is
often obtained through the use of a simple analytic program called APAS
(Aerodynamic Preliminary Analysis System). While suffering from an archaic
and temperamental interface, APAS yields results swiftly for simple geometries at
a variety of angles of attack and Mach numbers. The results from APAS are
compared to those obtained through the analysis of the same vehicle shape using a
sophisticated CFD program called GASP (General Aerodynamic Simulation
Program). The comparison is made on the forebody for the Stargazer Bantam
launch vehicle, which is based on a Hankey-wedge design. Significant
differences are noted and techniques to improve the accuracy of APAS output
data are suggested
(Georgia Institute of Technology, 1999-08-01)
Tooley, Jeffrey
The ideal NASA space transportation system of the future consists of a fleet of low cost
vehicles that can provide a wide variety of payload options while leveraging future
commercial launch markets. The Bimese concept, a NASA Langley design for a reusable
Earth-to-orbit space transportation system, tries to fill this future by attempting to,
"provide the broadest range of payload and mission capabilities with the minimum
number of architectural developments (Talay)." Creating a vehicle that meets this
requirement can minimize development costs because the same vehicle design (and hence
the same development cost) can be used to support various missions. Such a
transportation system can also result in a more efficient operational and manufacturing
scenario by creating a learning curve effect on these processes. A vehicle that can
perform various missions also has the advantage of early initial operating capability
because it can be phased in over time with early missions consisting of the simplest
configurations. These characteristics of the Bimese space transportation system make it a
candidate for a future NASA supported launch vehicle. The intent of this paper is to
analyze the performance and economics of the Bimese space transportation system in
terms of trying to fulfill NASA’s ideal future
(Georgia Institute of Technology, 1998-10-01)
Scott, Jeffrey
This paper presents a method of transforming aerodynamic datasets generated in
Aerodynamic Preliminary Analysis System (APAS) into parametric equations which may
subsequently be used in a multidisciplinary design optimization (MDO) environment for
analyzing aerospace vehicles.
APAS is an analysis code which allows the user to create a simple geometric
model of a vehicle and then calculate the aerodynamic force coefficients of lift, drag, and
pitching moment over a wide range of flight conditions. As such, APAS is a very useful
tool for conceptual vehicle designs since it allows the force coefficients for a given
design to be calculated relatively quickly and easily.
However, APAS suffers from an outdated user interface and, because it is tedious
to generate a new dataset during each design iteration, it is quite difficult to integrate into
an MDO framework. Hence the desire for a method of transforming the APAS output
into a more usable form.
The approach taken and described in this paper involves the use of regression
analysis techniques to accomplish the data transformation with three goals in mind. The
first goal was to develop a parametric model for calculating the aerodynamic coefficients
for a single unique geometry. The second goal was to extend this model to capture the
effects of changes in vehicle geometry. The third goal was to write a Fortran program
that would be capable of automatically carry out the regression analysis on a given APAS
data set and produce the desired parametric equations. This paper presents the results and
gives the model developed for analyzing a sample vehicle with a fixed geometry as well
as the results of a sample vehicle with a variable geometry. The Fortran computer code is
also given.