Four problems were defined which had aspects which would be reasonably assigned to an interdisciplinary design team. The design problems are: (1) design of a thermal shield for a lunar telescope (thermal protection for a lunar telescope); (2) selenotextile shielding structure (a structure to protect a lunar habitat from intense solar radiation of tubes of woven polytetrafluoroethylene coated fiberglass fabric); (3) pneumatically assisted elbow joint design for the NASA Zero-prebreathe suit (will allow astronauts to make the transition from a high pressure internal environment to a lower pressure suit without spending time in an air lock); and (4) electrochemical system to power assist an astronaut's finger joints (assist in the movement of an astronaut's distal and proximal interphalangeal finger joints)

Davis, Jill B.

Dorrity, J. Lewis

English

NASA Technical Reports Server

GEORGIA INSTITUTE OF TECHNOLOGY
SCHOOL OF TEXTILE & FIBER ENGINEERING
FINAL REPORT
ON THE
NASA/USRA ADVANCED DESIGN PROGRAM ACTIVITY 1990/91
Principal Investigator: Dr. J. Lewis Dorrity
Graduate Teaching Assistant Ms. Jill B. Davis
(NASA-CR-189998) NASA/USRA ADVANCED DESIGN
PROGRAM ACTIVITY 1990/1991 Final Report
(Georgia Inst. of Tech.) 14 p CSCL 110
G3/24
N92-21343
Unclas
0073921
https://ntrs.nasa.gov/search.jsp?R=19920012100 2020-03-17T13:28:00+00:00Z
The NASA/USRA support of our design effort has been most helpful in enhancing the
teaching of our design courses. The monetary award has the obvious advantage of providing
needed Graduate Teaching Assistance support and also other funds for supplies, travel, etc. Our
TA has also gained valuable experience by participating in the summer internship program. The
interest shown by our Langley mentor, Dr. John Buckley, has been most helpful. One of the
most important benefits has been that the students have been exposed to interesting and
challenging problems which cause them to ponder constraints which they have not previously
considered. I believe that working on these space-related problems has been a valuable
experience which has greatly broadened their education.
Interdisciplinary Activity:
The School of Textile & Fiber Engineering continued to pursue design projects with the
Mechanical Engineering School giving the students an outstanding opportunity to interact with
students from another discipline. Four problems were defined which had aspects which would
be reasonably assigned to an interdisciplinary design team. The design problems are
summarized below:
Design of a Thermal Shield for a Lunar Telescope
The goal of this project was to design a shield to provide thermal protection for a lunar
telescope. This design was required to meet specific objectives, including the following:
1) retract during nighttime viewing
2) close during lunar day
3) reflect infrared radiation
4) minimize temperature fluctuations
5) cover entire telescope
6) last 30 years
In addition, the design was subject to a number of constraints related to lunar conditions and
shuttle cargo space; some of these include
1) 50 man hour assembly time
2) launch mass < 4000 kg
3) transport length <. 27 m
4) transport diameter < 7 m
5) serviceable within lunar temperature range
6) retain properties in vacuum
7) withstand severe solar radiation (p and uV).
The final design has been dubbed "The Rising Cylinder." The proposed structure will
consist of two concentric cylinders 9.75 m high and a 10 m high third cylinder which will
carry the cover. Figures 1 and 2 are schematics of the structure in the open and closed
positions, respectively. The top two cylinders will be lifted into place using a bootstrap reeving
system located in the support members of the cylinders. The cover will consist of two disk
halves which open and close using a rack and motor system.
The primary thermal protection system will be gold-coated fiberglass woven fabric
attached to the support frame. Specifications of this fabric are as follows
1) 5.5 tex continuous filament fiberglass yarn
2) 22 ends/ cm
3) 22 picks/ cm
4) plain weave
5) coated weight 194 g/ m2
Gold will be vacuum deposited onto a polyester film which will then be adhesively bonded
to both sides of the fiberglass substrate. The purpose of this double-sided coating is to prevent
"curling" due to the differential between thermal properties of the coating and substrate. Gold
was selected because of its reflectivity and because it does not oxidize.
This design has many advantages. The rigid structure will prevent folding and abrasion of
the fabric. The structure will completely enclose the telescope, and the lifting mechanism
technology already exists. There are, however, some disadvantages of this design. Opening and
closing of the cover will be clumsy, and supporting the open cover will be difficult.
When the shield is closed, the telescope will be vertically positioned. When the shield is
opened, the telescope may move away from the vertical position by a maximum of 15 degrees.
See figure 2. The proposed shield is designed to have a lifetime of 30 years with a two year
maintenance schedule.
Selenotextile Shielding Structure
The objective of this study was to design a structure to protect a lunar habitat from
intense solar radiation. Included in the design is equipment for construction of the structure.
The proposed protective structure is designed to withstand the extreme conditions of the lunar
environment and to provide a 2 m maintenance space around the habitat. The construction
equipment is designed to operate on less then 13 Hp. Packaged, the structure and construction
equipment will fit into a space shuttle cargo bay.
The shielding structure will be 26 m in length, 12 m in width, and 9.5 m in height. The
structure will be comprised of 26 tubes, rectangular in cross-section (1.5 m x 1.0 m), leaned
like horseshoes at a 45 degree angle against a bank of regolith. See figure 3.
The individual tubes will be made of woven polytetrafluoroethylene (PTFE) coated
fiberglass fabric. Fabric specifications are as follows:
1) plain weave
2) 22 ends/ cm
3) 25 picks/ cm
4) coated weight 240 g/ m2
Fabric sections (from which the tubes will be made) will be heat sealed together to form
airtight seams, and thus prevent escape of regolith from the filled tubes. Each tube will have a
top opening supported by a fiberglass hoop. Individual tubes will also be connected with an
airtight joint to form the final structure.
The textile structure will be held in shape prior to and during filling by an interior
cavity filled with compressed gas. Regolith will be supplied to the structure via the fiberglass
hoops and a conveyor system. The primary conveyor system will be supported by a series of
telescopic legs and will be fed regolith by a second conveyor resting on the support mound. These
conveyors are shown in figure 4.
Pneumatically Assisted Elbow Joint Design
for the NASA Zero-Prebreathe Suit
In the near future it is expected that NASA will establish a lunar colony. In order to
assemble and operate this lunar base it will be necessary for astronauts to spend a significant
amount of time working outside the base. The existing procedure for adjustment from cabin
pressure to suit pressure takes 13 hours and 30 minutes. The proposed suit design will allow
astronauts to make the transition from a high pressure internal environment to a lower
pressure suit without spending time in an air lock. This suit, the Zero-Prebreathe Suit (ZPS),
is pressurized to 57 kPa, while the current shuttle suit is pressurized to 29 kPa, and the
shuttle's atmosphere is pressurized to 101 kPa.
The current ZPS design uses a toroidal joint to provide flexibility and has a bending
resistance of 3.0 Nm. When used with a micrometeoroid shield, the resistance to bending
increases to 5.4 Nm. This resistance, in conjunction with deconditioning caused by prolonged
exposure to low gravity or weightless conditions, accelerates the onset of fatigue and can
artificially limit the amount of work that an astronaut can do. The proposed design will
counteract the resistant forces to regain some lost work time and to help optimize the
astronaut's performance.
The assist mechanism to overcome the resistance of the elbow joint utilizes an inflatable
structure that deforms asymmetrically to match the path that the elbow travels through. A
rendering of the proposed solution to the problem of overcoming the resistance of the ZPS suit is
shown in figure 5. Figure 6 shows sectional views of the design. The components of the assist
mechanism are denoted in figure 6. The expansion pattern is shown in figure 7. The outer edge is
exposed to a very high deformation, with approximately a 120% change in length. The inner
edge expansion is relatively smaller, with a total elongation of approximately 70%. Note that
the total angular rotation is 130°, as specified by NASA requirements. The upper sealing joint
must be able to accommodate 15° of angular rotation. The proposed design meets this
requirement by being compatible with the existing joint. Note that a 0.635 cm. ring thickness
has been included in the sealing joint design to accommodate any later adaptation of the design.
Similarly, the lower sealing joint must accommodate 180° of rotation.
The total cross sectional area of the structure is approximately 7.9 cm2. The area is
approximate because the segmented form has an area that varies slightly between the large and
small diameters. The torque exerted by the structure is constant at 5.4 N, because the ends of
the structure occur at the large diameter.
The assist mechanism is made from a plain woven polyester fabric cut with a saw-tooth
pattern. In order to make the chamber deform as shown in figure 7, filling yarns of varying
linear densities should be used to weave the fabric. Fine filling yarn should be inserted for
flexibility (and chamber elongation) along the outer side of the fabric pattern, and coarser
filling yarn is used to weave stiffer fabric along the inner axis of the fabric pattern. When the
fabric is folded and assembled, the fine yarns meet at the saw-tooth seam, where greater
elongation takes place. The chamber should be assembled to achieve the necessary response of
the chamber upon inflation.
Fabric specifications are as follows:
1) plain weave
2) 14 ends/ cm
3) approximately 14 picks/ cm
4) nominal yarn diameter 0.013 cm
The finished, cut fabric should be impregnated with urethane before assembly of the structure.
This joint is designed to be incorporated with the NASA ZPS and to have a lifetime equal
to that of the ZPS.
Electromechanical System to Power Assist
an Astronaut's Finger Joints
The proposed design is an electromechanical system to power assist the movement of an
astronaut's distal and proximal interphalangeal finger joints. Figure 8 shows these joints and
their desired range of motion. The objectives of this project were to:
1) reduce astronaut fatigue
2) provide greater ease of movement
The design was subject to a number of constraints, including the following:
1) allow 90° range of motion at proximal interphalangeal joint
2) allow 45° range of motion at distal interphalangeal joint
3) compensate for 75% of suit's bending resistance
4) integrate with current suit
5) weigh <. 5 Ibs/ arm
6) must not generate excessive heat
7) require little or no maintenance
8) have lifetime comparable to that of suit
9) must not hinder hand operation in event of failure
The approach taken is called the "Stacked Triangle" method; it includes design and
selection of a force sensing system, electromechanical actuator, glove finger bending
mechanism, actuator controls, and materials for the bending mechanism and motor mount
construction. Figure 9 is an artist's rendering of the design. The force sensing system will
consist of a poly(vinylidine fluoride) (PVDF) piezoelectric pressure sensing grid which will
relay electrical voltage to an amplifier per unit of force. The proposed electromechanical
actuator is an advanced linear electric motor with a rare earth magnetic core. The linear motor
will move the finger apparatus by displacing a kevlar cable. This cable will force the aluminum
structure to actuate due to off-center force derived moments about the distal and proximal
interphalangeal joints, the automatic controls for the system will consist of sensor, amplifier,
and motor transfer functions. The feedback loop will consist of an adjustable feedback gain. The
entire system will be incorporated into the spacesuit between two Teflon coated textile layers.
All components will be integrated into the suit with appropriate textile materials.
The electromechanical system will overcome the suit's bending resistance and provide
force to achieve a range of motion of 45 degrees for the distal interphalangeal joint and 90
degrees for the proximal interphalangeal joint. Required operations will be power assisted as
necessary. The system is designed to have a lifetime comparable to that of the spacesuit.
Challenges to Textile Engineering Students
The design projects briefly described above provided a unique challenge because of the
harsh lunar environment which is hostile to most textile fibers. The extremely important
requirement to minimize weight for space flight gave the students a new perspective on design
constraints.
Challenges to our Curriculum:
Our present curriculum requires our seniors to take two quarters of engineering design
in order to fulfill the ABET requirement for a capstone design course. The School has chosen to
divide the courses into "wet-processing" and "dry-processing". This does constrain us to
keeping the projects to a 10-week time period. If we were to carryover projects from one
quarter to another, the students would not see the complete design cycle and the educational
value would be diminished. We must ask ourselves how we may provide the best design
experience and still provide NASA with a reasonable return on their investment.
CLOSED
SBC1IOK A-A
INA
NOTTS: GOID PLATED riHEBGLASS REMOVED
HGURE1
OPEN-
OPTION 1
I
OPTIONS
NOTE: GOID PLATED FTHEBGLASS REMOVED
HGURE2
SIDE
VIEW
26m
1.5m 9m
FRONT
1.5rn
1m
I
1.5m
CROSS-SECTION
W
 FUNNEL _
HOUES
WITH FIBER
dlASSRODS
0 0 0 0 0 0 0 0
TOP
VIEW
FIGURES STRUCTURE SCHEMATIC
LLJ
O
o
FIGURES RENDERING OF ELBOW
Control
FIGURE 6 CROSS-SECTIONAL VIEW
FIGURE 7 DEFORMATION PATTERN
Joint 1
Distal Interphalangeal Joint
/JoinJ t 2
Proximal Interpnalangeal Joint
B
FIGURE 8 RANGE OF MOTION DESIRED IN ELECTROMECHANICAL SYSTEM
FIGURE 9 ARTISTS RENDERING OF ELECTROMECHANICAL SYSTEM


NASA/USRA advanced design program activity 1990/1991

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