NASA has selected two software innovations that save
significant money and time over more traditional methods as
co-winners of its 2002 Software of the Year Award. Each team
of developers will receive an award of $50,100 in cash from
the NASA Administrator. Both software design tools have been
adopted by other government agencies, private industry and
academia.

The DSMC Analysis Code (DAC) software package, developed at
NASA’s Johnson Space Center in Houston, models the flow of
low-density gases over flight surfaces. DSMC stands for
Direct Simulation Monte-Carlo and is a simulation method. The
software provides insight into the interaction of spacecraft
and rarified environments, such as those encountered during a
spacecraft entry into an atmosphere at high altitudes.

DAC was used to provide information to help optimize and
verify maneuvers of spacecraft that orbited Mars after they
were slowed by repeatedly skimming through that planet’s
atmosphere instead of relying on thrusters for deceleration.
The technique enabled the spacecraft to be lighter, which
reduced launch costs.

Another application is analysis of plume impingement, the
effects of firing of thrusters by one spacecraft on another
spacecraft nearby. An early use of the software was analyzing
the effect of space shuttle thruster firings as the vehicle
approached the Russian space station Mir during the Shuttle-
Mir program. This has since led to significant changes in
docking procedures and venting operations aboard the new
International Space Station.

DAC is in use at most NASA centers and within the U.S.
military, and is beginning to be employed by the aerospace
industry for advanced applications involving high-altitude
vehicles. In addition, the unique flow-solvers adapted to DAC
allow the software’s use in applications in which the object
within the flow field is very small, such as MEMS (micro-
electromechanical systems) and nanotechnology devices.

The DAC team is led by by Gerald J. LeBeau, and includes
Forrest E. Lumpkin, Katie A. Jacikas, and Phil C. Stuart, of
Johnson; and Richard G. Wilmoth and Christopher E. Glass, of
NASA’s Langley Research Center in Hampton, Va.

The NASA Software of the Year co-winner — Cart3D — is an
aerodynamic simulation tool on which work began in 1992 at
NASA’s Ames Research Center, located in California’s Silicon
Valley. This software package provides designers and
engineers with an automated, highly accurate computer-
simulation suite that streamlines the conceptual and
preliminary analysis of both new and existing aerospace
vehicles.

Cart3D provides a revolutionary approach to computational
fluid dynamics — the computer simulation of how fluids and
gases flow around an object. Before the advent of this
software, the basic computational tool — the grid layout
used in analyzing designs of airplanes and spacecraft — had
to be hand-generated and required months or even years to
produce for complex models. Cart3D automates grid generation
to a remarkable degree, enabling even the most complex
geometries to be modeled 100 times faster than before.

Simulations generated by Cart3D help identify and fix
problems in military transport aircraft and helicopters.
Cart3D’s novel approaches allow simulation of complex
geometries in fields other than aerospace ranging from
astrophysics to computer science to electromagnetics. The
software is in wide use by universities and corporations, as
well as most NASA centers and other government agencies, for
a plethora of applications.

Cart3D was developed jointly by Michael Aftosmis and John
Melton of Ames, and Professor Marsha Berger of the Courant
Institute, New York University.

Each year the NASA Chief Engineer sponsors the NASA Software
of the Year competition — an international competition for
the largest award for software excellence — with technical
support from the agency’s Inventions and Contributions Board.

More information about the winners may be found at:
http://icb.nasa.gov/swoy2002/