Viewing requirements were identified early in the Space Station Freedom program for both direct viewing via windows and indirect viewing via cameras and closed-circuit television (CCTV). These requirements reside in NASA Program Definition and Requirements Document (PDRD), Section 3: Space Station Systems Requirements. Currently, analyses are addressing the feasibility of direct and indirect viewing. The goal of these analyses is to determine the optimum locations for the windows, cameras, and CCTV's in order to meet established requirements, to adequately support space station assembly, and to operate on-board equipment. PLAID, a three-dimensional computer graphics program developed at NASA JSC, was selected for use as the major tool in these analyses. PLAID provides the capability to simulate the assembly of the station as well as to examine operations as the station evolves. This program has been used successfully as a tool to analyze general viewing conditions for many Space Shuttle elements and can be used for virtually all Space Station components. Additionally, PLAID provides the ability to integrate an anthropometric scale-modeled human (representing a crew member) with interior and exterior architecture

Goldsberry, Betty S.

Lewis, James L., Jr.

Lippert, Buddy O.

Mckee, Sandra D.

Mount, Francis E.

English

NASA Technical Reports Server

USING COMPUTER GRAPHICS TO DESIGN
SPACE STATION FREEDOM VIEWING
Betty S. Goldsberry, Buddy O. Lippert, and Sandra D. McKee
Lockheed Engineering and Sciences Company
James L. Lewis, Jr. and Francis E. Mount
NASA Lyndon B. Johnson Space Center
"24191
INTRODUCTION
Viewing requirements were identified early in
the Space Station Freedom program for both
direct viewing via windows and indirect
viewing via cameras and closed-circuit
television (CCTV). These requirements reside
in NASA Program Definition and
Requirements Document (PDRD), Section 3:
Space Station Systems Requirements.
Currently, analyses are addressing the
feasibility of direct and indirect viewing. The
goal of these analyses is to determine the
optimum locations for the windows, cameras,
and CCTVs in order to meet established
requirements, to adequately support space
station assembly, and to operate on-board
equipment.
PLAID, a three-dimensional computer graphics
program developed at NASA JSC, was
selected for use as the major tool in these
analyses. PLAID provides the capability to
simulate the assembly of the station, as well as
to examine operations as the station evolves.
This program has been used successfully as a
tool to analyze general viewing conditions for
many Space Shuttle elements and can be used
for virtually all Space Station components.
Additionally, PLAID provides the ability to
integrate an anthropometric scale-modeled
human (representing a crewmember) with
interior and exterior architecture.
BA CKGRO UND
COMPUTER SIMULATION
The design of a computer simulation system,
such as PLAID, that includes human models is
f
a complex process. Total system performance
is dependent on the accuracy of the models
generated as well as the interactions between
humans, hardware, and software. Model
requirements can be based on workspace
geometry, figure anthropometry, strength/force
characteristics, and reach envelopes. If results
of simulation analyses are to be valuable,
development of the models must be based on a
valid representation of the environment. Also,
procedures must be employed that make
available alternative human/system designs.
Ultimately, quantitative predictions of events
and behaviors in response to realistic operating
conditions for various design alternatives must
be compared in order to select the optimum
design characteristics.
While there are many ways of quantitatively
predicting human behavior and performance,
computer simulation of the human operator in a
mission context represents a method that is
internally consistent and compatible with other
contemporary system engineering evaluative
techniques. Computer simulations usually
resolve many design and development
problems in an effective manner earlier than
experiments with human subjects. Even
though simulation does not eliminate the need
for empirical tests, properly exploited, it can
help to focus test time and energy on
appropriate issues and potential problems.
The analyst interested in evaluating human
performance can use computer simulation to
construct a graphic human model in much the
same way that an airplane or automobile
designer can model a vehicle. Then, the model
can be used to test various design concepts
relevant to human-system interactions and
integrations. Actually, a computer simulation
i:,lqem:  PAC E: Nor r LMeV
47
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system can be developed long before a
prototype or test facility can be made
operational.
PLAID MAN-MODELING SYSTEM
PLAID uses anthropometric data collected
from astronaut candidates in the JSC
Anthropometrics and Biomechanics Laboratory
to generate human models with realistic joint
limits and user-specified size characteristics. A
high-fidelity model of the Space Shuttle
Remote Manipulator System (RMS) is also
contained in the PLAID database. For many
years, the models have facilitated the
comparison of reach envelopes for humans and
remote manipulators in order to determine
which space operations are feasible for
astronaut extravehicular activities (EVA) and
which are more appropriately accomplished by
robotics applications. PLAID has also played
a major role in satellite retrieval execution,
equipment failure diagnosis, and vehicle
damage prediction.
PLAID is a three-dimensional-solids modeling
system which generates computer models that
can be examined from an infinite number of
viewpoints. This feature allows the system
user to position its viewpoint where the eyes of
the crewmember or lens of the camera would
be located. Then, subsequent analyses can
reveal what a crewmember can or cannot see.
The PLAID system has taken into
consideration that the visual environment of
space is different from a normal Earth
atmosphere and has incorporated appropriate
contrast ratios, shadowing, and light scattering
for the space environment.
SPACE STATION
PROCEDURE
Since viewing tasks vary in complexity,
relevant viewing requirements and proposed
window locations were identified. Using the
PLAID system, geometric models of Space
Station Freedom elements and configuration
models were created. These models reflected
up-to-date Space Station Freedom architectural
information for internal and external elements.
Also, proposed window and camera locations
were integrated with the models. Then,
computer graphics of various viewing
scenarios were generated which revealed
fields-of-view for selected locations of interest.
Finally, the graphics generated by the system
were analyzed relative to published design
requirements and specifications.
The simulation is influenced by more than a
three-dimensional layout of the environment.
In particular, task sequence and task time are
important ingredients. For example, if the
humans must monitor exterior facilities while
operating interior controls, their fields-of-view
will be decreased because their positions will
probably be farther from the window.
Shadowing can also reduce visibility.
The simulation helped analysts evaluate the
proposed window locations and identify
problem areas. Recommended window
placements were determined by the integration
of the view available from a particular position
with various other factors such as operations
requirements, anthropometric clearances,
traffic flow, and window accessibility.
DATA
Data in the form of PLAID graphics were
generated and maintained at the JSC/Man-
Systems Division. Figures 1 through 4,
illustrated on the following page, exemplify the
types of data used in the analyses. Figure 1
was generated to determine the viewing
clearance needed if an airlock were placed near
the window.
Figure 2 illustrates that the cupola will
accommodate two crewmembers. Note the
design requirement that the Crew Escape
Rescue Vehicle (CERV) be visible from the
cupola is met. Displays that share the
crewmembers' fields-of-view, are shown.
Figures 3 and 4 illustrate that viewing of the
external environment can be accomplished.
Analyses have determined that Earth viewing
or optic experiments could be obstructed by
truss work from some locations.
48
I
i
B _ k --
r _. .k
Figure 1. A 95th percentile male crewmember
looking out of the cone-shaped end portion of a module
(endcone) window.
J
Figure 2. Two 50th percentile males in a cupola.
Figure 3. A view of extravehicular activity (EVA).
Figure 4. An Orbiter window or external camera
view during approach or departure.
DOCUMENTA TION
Comprehensive documentation of the Space
Station Viewing Analyses results will be
organized in a series of volumes. Volume 1
covers viewing of the Space Station Freedom
assembly sequence as seen through the Orbiter
windows and CCTVs. Volume 2 uses the
Man-Systems candidate topologies to evaluate
possible window locations in the U. S.
Habitation module. Volume 3 evaluates the
candidate window locations as proposed by the
European Space Agency (ESA) for the
Columbus Module, as well as selected alternate
locations. Volume 4 addresses viewing
conditions of the National Space Development
Agency (NASDA) Japanese Experiment
Module (JEM). Volume 5 is dedicated to the
discussion of viewing from the nodes and the
two cupolas baselined on nodes three and four.
Volume 6 addresses indirect viewing and the
placement of cameras throughout the station.
Volume 7 pertains to the viewing conditions of
the U. S. Laboratory module. Volume 8 will
49
address Phase II Space Station Freedom
viewing impacts. The planned order of
preparationfor thesebasicvolumesis 3, 2, 4,
7, 5, 1, 6, and 8. The first four volumesin
this series have been released. Published
recommendationsfrom thecompletedvolumes
follow.
RECOMMENDA TIONS
U. S. Habitation Module
1. A requirement for windows in the crew
quarters should be established by the program.
2. Two viewing stations, currently proposed,
should be relocated to positions that will
provide unobstructed views.
3. Modular interior layout and wardroom area
window placement should be integrated such
that recreational viewing (i.e., viewing of the
Earth limb) is optimized. Selected port rack
locations are well suited for wardroom area
windows.
4. Windows should be placed in the portion
of the quadrant where the eyes are most likely
to be, while maintaining compliance with the
local vertical.
U. S. Laboratory_ Module
1. Evaluate scientific celestial viewing from
the zenith (-Z) oriented windows in the module
to insure minimal interference of Space Station
elements.
2. A proposed floor window is suitable for
Earth viewing.
3. Optimum high-oblique viewing in the -Y
direction for scientific uses can be achieved
from a starboard window. Exact placement of
the window below the module centerline
should be determined based upon intended use
of the window.
ESA Columbus Module (CM)
1. Design of the module should provide
ample space for movement, interactions,
interfaces, and other human factors
considerations.
2. Orient a minimum of two windows in the
CM in the +X and -X directions.
3. Rotate the aft endcone at least 45 degrees
from 12 o'clock position to meet Space Station
Program 30000 requirements and support
recreational viewing.
4. Rotate the window location in the forward
endcone of the CM 45 degrees clockwise.
5. Consider the need for celestial viewing
from the CM in the overall station
configuration.
6. Establish commonality of window design
characteristics in all modules.
7. Supplement the view through the hatch
viewport by providing interior video which
could also be used to remotely monitor
activities within the modules.
NASDA Japanese Experiment Module
1. Supplement direct viewing of Mobile
Servicing Center (MSC) operations by using
the CCTV for indirect viewing.
2. Supplement direct viewing of the
Experiment Logistics Module (ELM) transfer
and berthing/deberthing operation by using the
CCTV for indirect viewing and for supporting
direct viewing from the hatch viewport beneath
the JEM berthing ring during the berthing
process.
3. Retain proposed windows in the aft
bulkhead.
4, Retain baseline with no windows in the
forward bulkhead, since no meaningful view
could be achieved.
5. Retain floor window for Earth observation.
6. For purposes of celestial viewing, use the
viewport between the JEM and ELM during
absence of the ELM. Further information is
5O
neededconcerning(a) durationof theELM's
absenceand (b) external covering of the
viewpointduringELM's absence.
CONCLUSION
VIEWING ANALYSIS
PLAID allows for an in-depth analysis of the
impact of direct and indirect viewing on
architectural design and human performance
issues. Specifically, window and video
location selections have been facilitated by the
use of this computer simulation system. This
system permits the integration of selected
window/camera locations with the internal
architecture, the validation of crew activity
sequences, and the determination of necessary
body movements required to accomplish
viewing tasks. Through findings in these
analyses, analysts have been able to write a
Change Request (CR) affecting high level
Space Station Program documents. Requests
address placement issues in the modules.
Future volumes will address indirect viewing,
cupola viewing, node windows, and Space
Station assembly.
PLAID SYSTEM
Development of a more interactive, real-time
system which uses natural language will
enhance capabilities of the system. Expansion
of the human-modeling capability will include
a population range from the 95th percentile to
the 5th percentile female. Currently, work in
this area is being conducted for JSC and other
users at the University of Pennsylvania under
the direction of Norman Badler, PhD.
Also, the capability of generating video
animation sequences is being added to PLAID.
This feature will allow for simulation of a
complete task sequence rather than a
"snapshot" approach. Animation will provide
for a more comprehensive evaluation of
crewmember activities, as well as reveal the
relationship between a series of contiguous
activities. By following the action flow, the
system user can isolate spatial interferences,
procedural inconsistencies, and crewmember
interactions.
Finally, a dynamic program extension is
planned that will allow system users to more
accurately evaluate factors such as force and
path trajectory. In addition, an efficient ray
trace algorithm would enhance lighting study
capabilities.
A CKNOWLEDGEMENTS
These viewing analyses could not have been
accomplished without the NASA Graphics
Analysis Facility, Facility Manager Linda Orr,
and Lockheed technical support.
REFERENCES
. Mount, Frances E. and McKee,
Sandra. Space Station Freedom
Viewing Analysis: Volumes 2, 3, 4,
and 7, JSC No. 32089, NASA
Johnson Space Center, 1989.
. Mount, Frances E. and Lewis, James
L. Space Station Viewing Require-
ments (1986). 1986 SAE Aerospace
Technology Conference and
Exposition.
51


Using computer graphics to design Space Station Freedom viewing

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