Measuring human performance in a microgravity environment will aid in identifying the design requirements, human capabilities, safety, and productivity of future astronauts. The preliminary understanding of the microgravity effects on human performance can be achieved through evaluations conducted onboard NASA's KC-135 aircraft. These evaluations can be performed in relation to hardware performance, human-hardware interface, and hardware integration. Measuring human performance in the KC-135 simulated environment will contribute to the efforts of optimizing the human-machine interfaces for future and existing space vehicles. However, there are limitations, such as limited number of qualified subjects, unexpected hardware problems, and miscellaneous plane movements which must be taken into consideration. Examples for these evaluations, the results, and their implications are discussed in the paper

Morris, Randy B.

Whitmore, Mihriban

English

NASA Technical Reports Server

N94- I1 537
MEASURING HUMAN PERFORMANCE ON NASA'S
MICROGRAVITY AIRCRAFT
Randy B. Morris and Mihriban Whitmore
Lockheed Engineering and Sciences Co.
2400 NASA Rd. 1, C95
Houston, TX 77058
Abstract
Measuring human performance in a microgravity environment will aid in
identifying the design requirements, human capabilities, safety, and productivity
of future astronauts. The preliminary understanding of the microgravity effects
on human performance can be achieved through evaluations conducted
onboard NASA's KC-135 aircraft. These evaluations can be performed in
relation to hardware performance, human - hardware interface, and hardware
integration. Measuring human performance in the KC-135 simulated
environment will contribute to the efforts of optimizing the human - machine
interfaces for future and existing space vehicles. However, there are limitations,
such as limited number of qualified subjects, unexpected hardware problems
and miscellaneous plane movements which must be taken into consideration.
Examples for these evaluations, the results, and their implications are
discussed in the paper.
INTRODUCTION
In order to design environments and
develop countermeasures as well
as support systems that protect and
enhance human capabilities, safety,
health, and the productivity of future
astronauts, we need a thorough
understanding of the microgravity
environment. By gaining this
understanding, the probability of
achieving greater mission
successes is enhanced. One way of
gaining this preliminary microgravity
information is through the use of
NASA's KC-135 aircraft, which
simulates this environment. The
KC-135 aircraft is ideally suited for
short duration tasks. These tasks
can evolve gross and fine motor
activities and validating technology
concepts. Some of the concerns
with the various users are their
anthropometric, physical, and
physiological capabilities. A human
factors goal is to provide designs/
interfaces for living and working in a
microgravity environment and flight
hardware in order to achieve
optimal human performance, while
providing safe human - machine
interfaces. 1
APPROACH
In order to achieve the best human -
machine interface, human
performance can be measured on
the ground, KC-135, and the shuttle.
These evaluations (KC-135) have
been performed in relation to
hardware performance, human -
hardware interfaces, and hardware
integration. One type of evaluation
is to evaluate the hardware's
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performance in microgravity
conditions. These evaluations look
at the equipments functionality and
maintainability. Two examples of
this type of evaluation are the video
tape recorder (VTR) and Macintosh
Powerbook 170 evaluations. This
type of an evaluation is increasing in
importance as the recent trend is to
use commercially off the shelf
products. While these products
work quite well in the presence of
gravity, in its absence, unforeseen
problems can arise. Therefore, it is
advantageous to test an off the shelf
product for the microgravity
environment and make
modifications, if necessary, instead
of designing a completely new
product for microgravity use. Some
examples of these problems include
a trackball that had too much play in
the ball (ball mechanism floated),
and unexpected loss of camcorder
battery power.
The VTR evaluation looked at the
machine's servo circuits
characteristics by way of the
Horizontal Sync Jitter and Signal-to-
Noise Ratio tests, as well as the
man/machine interface
characteristics such as tape ejection
and insertion, activating play, search
(in both directions), fast forward and
reverse (see Figure 1). All of the
VTR's mechanical and operatibnal
tests were successful with no
difficulties encountered. The only
recommendation was to add a finger
restraint to allow the operator to
stabilize their hand for button
activation. 2 While the Powerbook
evaluation looked at the text/
graphics readability, display angle
adjustability, select button activation
pressure and location, keyboard
location and the keys' pressure,
restraint requirement, and size,
shape, and location of the trackball.
In general, the Powerbook computer
worked well on the KC-135. 3
Human hardware -interface
involves the location, type, size, and
ease of use of displays and controls.
Figure 1 - Subject Evaluating VTR
An example of this type of
evaluation is the Cursor Control
Device Evaluation (see Figure 2).
The objective of this experiment was
to aid in determining the best cursor
control device design for use in
microgravity. An optical mouse,
trackball, mouse pen, and thumb
ball a_resome of the cursor control
devices that were tested. The
experiment consisted of performing
a text editing task which required
pointing, dragging and clicking.
Dragging time, pointing time and
percentage of correct responses
have been analyzed as
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performance measures. Results of
these evaluations showed
mechanical deficiencies and
performance differences among the
devices. The ones which exhibited
the best performance were selected
for evaluations onboard the
Shuttle. 4
Figure 2 - Subject Evaluating Cursor
Control Device
The third type of evaluation is the
integration of the hardware into the
overall system (e.g. is the proposed
location for the equipment a feasible
location). The workstation
evaluations fall into this category
(see Figure 3). The objective of this
study was to evaluate the physical
dimensions and layout of the
workstation components. The
workstation components consisted
of the keyboard desk, translational
hand controller, rotational hand
controller, monitors, control panels
and mobility aids while using
different foot restraint systems. The
entire evaluation was video taped
for post flight computer simulation
modeling. The results from the KC-
135 flight showed that the
workstation keyboard desk height
and restraint systems concepts, as
well as the location of the hand
controllers would be critical for
accommodating the required range
of users (147.32 cm to 193.04 cm) in
the microgravity neutral body
position .s,6
The microgravity testing is an
important part of hardware
development as a tool to increase
human performance because it
allows the investigators to see the
effects of weightlessness on the
human - machine interface. It also
gives you a Chance to make some
design refinements if any are
necessary before it actually goes
into space. This allows the
investigators to save time and some
potential problems.
Pre-flight Preparations
There are several preflight activities
which must be completed no later
than six weeks prior to the flight.
One of these are the preparation of
your hardware to ensure that it
meets the qualifications for the KC-
135. The equipment must be able to
fit in the aircraft and be able to
withstand the appropriate flight
loads in the takeoff and landing
configuration. Subject selection is
another very key issue since there is
a limited number of qualified
subjects. The other two important
issues are the selection of the
performance measures that you
want to measure and the design of
your test protocol.
Figure 3 - Subject Evaluating Workstation
Baseline data was collected on the
ground prior to the flight. This gives
you performance measures in a
normal ground (one g) environment
to compare to the participants
microgravity (zero g) performance
measures. This baseline data
collection also serves as a dry run to
your actual experiment by
familiarizing the participants with the
hardware and what exactly they will
be doing during this evaluation, as
well as allowing you a chance to
modify the test protocol if necessary.
Flight
NASA's KC-135 aircraft simulates a
shirt sleeve space flight
environment. It flies in a parabolic
flight pattern that produces a
microgravity period ranging
between 20 and 27 seconds with an
average of 23 seconds. The
microgravity period is preceded by a
two-g pull up and two-g pull out.
The duration of these flights is
approximately two hours with the
total microgravity time being
between fifteen and eighteen
minutes.
During the KC-135 flights the human
performance measures can either
be objective or subjective. As a
minimum, subjective data is
collected during all of the
evdluations. If the nature of the
experiment allows, objective data is
also collected. The subjective data
is collected through questionnaires
and audio comments that the
519
participants have made during the
evaluations. While some examples
of the objective measures are task
completion time and percent error,
frequency of use, anthropometric/
physiological measurements.
These are collected through video
recording or software.
Post Flight
After the flights, the participants are
given a follow-up briefing and (if
necessary) more data will be
collected for analysis and
comparison to the flight and
baseline data that was collected
previously.
RESULTS
The advantages of performing
experiments onboard the KC-135
are that they are cost effective and, if
applicable, design refinements can
improve the interface and thereby
improve human performance. A
good example of this was during the
cursor control device evaluations
onboard the KC-135, where there
was a mechanical deficiency with
the trackball. This deficiency was
that the ball floated due to too much
"play" in the ball mechanism. Once
it was modified, it worked as
expected in the microgravity
environment.
KC-135 evaluations allow us to see
the effects of weightlessness on
human performance while
performing tasks and gives
assistance in identifying the crew's
needs and concerns. This was
shown during the workstation
evaluations, when the crew desired
additional hand holds so that they
would avoid accidently grabing onto
any protruding controls.
However, there are some limitations
to performing experiments onboard
the KC-135. Some examples of
these are that there are a limited
number of qualified subjects, short
set up times for the experiments, can
encounter unexpected hardware
problems and extraneous plane
movements such as air turbulence.
In addition, it is not suitable to test
the effects of extended microgravity
exposure.
CONCLUSIONS
Experiments conducted onboard the
KC-135 enable us to achieve real
time experience in a microgravity
environment while creating
challenges in selecting human
performance measures and they
can best serve the function as being
a precursor for shuttle experiments.
Microgravity (KC-135) evaluations
were very useful to determine the
effects of "weightlessness" on
human performance, to identify crew
needs, and to refine overall designs.
Measuring human performance in
simulated microgravity
environments, such as the KC-135,
will contribute to the efforts of
optimizing the human - machine
interfaces for future and existing
space vehicles. It will also ensure
safe and productive work
environments for the crewmembers.
REFERENCES
• NASA Space Life Sciences
1991, Space Human Factors
Discioline Science Plan 1991.
Washington D.C., 1991
= Morris, R.B., Wilmington, R.P.
and Whitmore, M., M.Lc,z.o._._J_
Evaluation of Video TaD_
520
1o
J_.gg.B;[_, JSC No.: 36046,
LESC No.: 30197, Houston, TX:
Johnson Space Center, 1992.
Morris, R.B. and Whitmore, M.
(1992). Microaravity Evaluation
of Macintosh Powerbook 170.
JSC No.: 25815, LESC No.:
30222, Houston, TX: Johnson
Space Center, 1992.
Detailed Test Ob!ective Space
Station Cursor Control Device
Evaluation II and Advanced
_i_,_, Final Report,
Houston, TX: Johnson Space
Center, 1991.
5. Whitmore, M., Wilmington, R.P.
and Morris, R.B., Command and
Control Workstation
Anthrooometric Evaluations for
SoaceStation Freedom: Phase
J,JSC No." 36029, LESC No."
30119, Houston, TX: Johnson
Space Center, 1992.
6. Whitmore, M. and Morris, R.B.,
Command and Control
Workstation Anthrooometdc
Evaluations for Space Station
Freedom: Phase I1, Houston,
TX: Johnson Space Center,
1992.
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