1999 Weightless Wildcats
Photos Courtesy of NASA
See more photos (courtesy of the Weightless Wildcats) below.
Wildcats enjoy the reduced-gravity ride (March 16) - (l-r) Eric,
Patrick, Ron, and Jim.
Variability of Precision Deployed Structures (VIPERS)
Docking Excitation for System Identification (DESI)
Patrick and Andrew and the VIPERS experiment in reduced gravity,
March 15, 1999.
The VIPERS experiment - Patrick (March 15) and Patrick and Eric
(March 16).
Jim and Ron and the DESI experiment in reduced gravity, March
16, 1999.
Patrick and Andrew head for the plane; Ron issued his flight suit;
Jim and Ron report to the ground crew (March 15, 1999).
Photos Courtesy of Weightless Wildcats
Wildcats before boarding; the ground crew waits and watches for
the plane's return; after the flight (March 15, 1999).
Abstract
Two teams of Engineering students from the University
of Kentucky were chosen to participate in the March 1999 NASA
Reduced Gravity Student Flight Opportunities Program. Drs. Suzanne
Weaver Smith and John A. Main of Mechanical Engineering advise
the teams. One experiment will study precision deployment of spacecraft
structures (VIPERS). The other experiment will study the use of
vibrations caused by spacecraft docking for verification of computer
models of the docking force and spacecraft components (DESI).
The results of these projects could, in the future, contribute
to projects like the International Space Station.
While at the Johnson Space Center in Houston March
7-20, 1999, four UK students conducted these 2-day tests while
aboard a NASA KC-135 jet. This is the same plane used to train
astronauts and for filming the movie, Apollo 13." The four-engine
KC-135 can achieve a near weightless environment by following
a series of parabolic flight trajectories. As the plane flies
over the top of each parabolic arc (up to 40 times in a single
flight), it provides approximately 25 seconds of zero-gravity.
The UK students chosen to fly with the VIPERS project
were Patrick Hobbs, Andrew Clem, and Eric Hawkes (back-up). Susan
Moore, Beth Craft, and Bobby Jones helped design the experiment
and served as ground crew. The students chosen to fly with the
DESI project were Jim Jackson, Ron Couch, and Eric Hawkes (back-up).
Courtney Byers, Justin Kearns, and Chris Barker helped with the
design and as the ground crew.
The teams are indebted to the sponsors and advisors
for the 1999 projects, including the following: The Kentucky Space
Grant Consortium; The University of Kentucky; Peter Warren, Foster-Miller,
Inc., Boston, MA; Mark S. Lake, NASA Langley Research Center,
Hampton, VA; Hyoung-Man Kim, The Boeing Company, Houston, TX;
James Dagan, NASA JSC, Houston, TX; PCB Piezotronics, Depew, NY;
HAMA Laboratories, Palo Alto, CA; IOtech, Inc., Cleveland, OH;
The UK Department of Mechanical Engineering; George Nelson, UK
Graduate Student; Knight-Ridder Productions, Lexington, KY; and
the Popular Science Magazine Web Site (www.popsci.com).
For more information on the VIPERS or DESI projects,
contact Dr. Suzanne Weaver Smith at (606)257-4584, by e-mail at
ssmith@engr.uky.edu, or by mail at 467 Anderson Hall, Lexington
KY 40506-0046, or contact John Main at (606)257-7137, or by e-mail
at johnmain@engr.uky.edu.
Variability of Precision Deployed Structures (VIPERS)
Mechanical deployable systems have two major benefits - compactness
and durability. Two questions regarding the variability of deployment
in a microgravity environment and variability of the structures'
dynamic response during deployment also arise.
Our experiment, Variability of Precision Deployed Structures (VIPERS),
addresses these questions. The experiment consisted of repeatedly
deploying a precision multi-jointed structure and measuring the
final deployed position of a target point with a 5-micrometer-resolution
displacement sensor. The multi-jointed structure consists of high-precision
hinge joints provided by NASA Langley Research Center, Hampton,
VA, joining aluminum struts. The mechanism for deployment comes
from a strain-energy hinge joint design provided by Foster-Miller,
Inc. of Boston, MA. When released, this spring joint unfolds rapidly
providing the energy needed for the structure to deploy and then
locks to keep the structure secure in its deployed position.
Flight data was recorded to digital tape for post-flight
analysis to reveal the accuracy of the position of the target
in 0-g. This was compared to results from ground tests to give
insight on the accuracy of 1-g data compared to 0-g data. The
deploying structure was also recorded using a video camera and
included accelerometers to measure the dynamic time history of
the structural response caused by the spring action from the strain-energy
joint. Final results included the following: 1) statistical analysis
of the variability of the structure deployed position in 0-g,
2) examination of the validity of 1-g tests for prediction of
0-g results, and 3) documentation of issues for conducting precision
testing in the KC-135 environment.
Docking Excitation for System Identification (DESI)
With the recent launch of the first component of the
International Space Station, much current research is focussed
on verification of the analytical models and approaches used to
predict the dynamic behavior of such spacecraft, including approaches
to provide unmeasured docking forces and to identify component
model parameters. Our experiment, Docking Excitation for System
Identification (DESI), compares analytically predicted docking
forces with experimental docking forces measured in a microgravity
environment. In addition, the experiment will also provide data
to verify parameter identification approaches for flexible joints,
which may be linear or nonlinear in nature.
This experiment modeled the docking event using a phenomena
model consisting of a "space shuttle" mass, a "space
station" mass incorporating a linear/nonlinear joint and
a docking mechanism. Once the docking process was initiated the
"shuttle" impacted the "station" and the vibration
response was recorded onto a digital tape recorder via accelerometers.
A load cell at the docking point recorded the docking load time
history. Approach velocity measurements were also recorded using
a linear encoder provided by Lexmark, Intl. Data from ground and
microgravity tests was analyzed and compared.
Team members at the airport leaving for Houston (l-r front, Andrew,
Eric, Susan; back, Jim, Patrick, and Ron).
