Advanced Space Health Maintenance System: Technology
Enabling Extended Manned Space Exploration
Rice University
Austin Elam, Chris Gibson, Zeyad Metwalli, Roland Robb, Thomas Rooney
Faculty Advisor: Dr. Michael Liebschner
DEPARTMENT OF BIOENGINEERING, RICE UNIVERSITY, HOUSTON, TX
RASC-AL 2005 Forum
May 22-25, 2005
Cocoa Beach, FL
ABSTRACT
President Bush has recently announced an ambitious plan calling for the return to the Moon and a
manned mission to Mars. However, a wide variety of significant obstacles must be overcome to accomplish
these lofty goals, including the deleterious effects of microgravity on the human body. This project focused
on addressing a subset of these problems: the effect of a reduced gravity environment on the musculoskeletal and cardiovascular systems. The groundwork is proposed for a modular system of devices and
exercise equipment that will have the adaptability to maintain this facet of human health during extended
missions in any reduced-gravity environment. Each component of the system targets specific risks;
however, the use of this module based system allows for a multifaceted approach to addressing physical
health prevention, diagnosis, and, if necessary, treatment. Additional advantages of the proposed system
include lightweight, portable, and relatively cost-effective designs. This project proposes and discusses a set
of six devices, including previously developed countermeasure devices as well as several novel devices.
The working principle behind the proposed system is the application of acoustic vibration as a diagnostic,
treatment, and exercise tool. The feasibility of the project is demonstrated by the assessment of a developed
prototype of one of the new devices in addition to ongoing research for a second component. The successful
construction and initial round of testing on the limited budget of an undergraduate senior design team
suggest the ease with which this system may be adopted by NASA for implementation in upcoming
missions. The entire project is forecasted to be completed over the course of five years and at a cost of $20
million, well within the timetable and budget allotted for future missions beyond our solar system. The
adaptation of this project represents an important step towards the enablement of ongoing space exploration.
1. INTRODUCTION
President Bush ushered in a new era of
space exploration in 2004 when he proclaimed
that NASA would devote itself to establishing a
robotic and manned presence on the Moon,
Mars, and beyond in the decades to come.
Budget pressures and safety concerns make this
mission an arduous one, but success will
reconfirm the might of the U.S. space program
and immeasurably benefit humanity. As NASA
resumes shuttle flights and completes the
International Space Station (ISS), scientists are
busy developing the flight systems and support
for beyond-orbit missions.
One of the most important hurdles that
must be overcome before a long term human
presence can be sustained on the Moon and
Mars is the development of a health maintenance
system. The lack of gravity experienced during
the long transit to Mars, and markedly decreased
gravity on the surface of the Moon and Mars can
cause irreversible and life-threatening damage to
astronauts’ bodies over time.
NASA has
developed several exercise machines to help
astronauts maintain their health on the ISS, but
considerably more research and development is
needed in order to enable humans to embark on
extended missions.
Although there are many physical and
psychological effects of long-term space
missions, we have specifically explored a system
for diagnosing and counteracting the symptoms
of these effects on the cardiovascular and
musculo-skeletal systems. The lack of normal
loading induced by gravity results in the atrophy
of muscle, the loss of significant bone mass and
bone strength, and a reduction in the
effectiveness of the heart. Additional risks arise
from the expansion of the intervertebral discs
through swelling in a reduced gravity
environment, which can cause back injuries due
to artificially increased range of motion when
the astronauts are put to work.
The modular system we propose to
counteract the cardiovascular, muscular and
skeletal effects of reduced gravity consists of a
whole body compression system, a bone
maintenance stimulator, diagnostic devices,
exercise devices, and injury treatment devices.
When used together, the system will work
effectively, while costing only a fraction of other
critical systems. In addition, since the basic
technology behind each module is shared, the
development costs are drastically reduced.
Although some of the technologies we propose
have not been fully tested, all recommendations
are supported by research on Earth, and are
likely to be effective. Additionally, all systems
could be easily tested for efficacy aboard the
ISS, making the concept verifiable. To prove
the ease and speed with which the technology
could be developed, the team has produced a
preliminary prototype and conducted initial
testing on one of the components using a budget
of less than $1500.
By stabilizing the bodies of the
astronauts who will undertake the heroic missions
to live on the Moon and travel to Mars, we will
decrease the chances of a health-related mission
failure. The inexpensive yet important system
will serve to enable the President’s vision.
2. APPROACH
To establish a complete system that
maintains all facets of astronaut health is an
extensive NASA project with a tentative schedule
of over twenty years. As such, it is not possible
to address every concern outlined in the
Bioastronautics Critical Path Roadmap in an
essay of this scope. Instead, this project attempts
to isolate several interrelated risks that have been
identified by previous work and propose an
integrated
means of addressing them.
Specifically, eight risk areas within the Health
and Human Countermeasures (HH&C) have been
selected, representing the three disciplines of
bone, cardiovascular, and muscle health. In
providing these risks with potential solutions, the
risks have been grouped into six critical points.
Each critical point is listed below along with a
brief summary of the tools we propose as
countermeasure.
Accelerated Bone Loss and Fracture Risk (Risk 1)
o The Spine and Trochanter External Vibration Effecter (STEVE), is a wearable device that
will hold the astronaut in compression while sending low-amplitude vibrations through the
body that will minimize bone loss and decrease fracture risk. The system can be adjusted
to work in any partial Earth-gravity (1 g) environment.
o The OsteoSonic bone density diagnostic tool, developed by Dr. Michael Liebschner of
Rice University, uses painless vibration to help measure the rate of bone loss to help
monitor the health of the astronauts.
Impaired Fracture Healing (Risk 2)
o A Vibration Fracture Healing Unit (VFHU) will splint fractured long bones, and use
vibration to help fractures heal effectively and more expeditiously. Solving this critical
problem will assist the astronaut body in fracture healing to prevent mission failure.
Injury to Joints and Intervertebral Structures (Risk 3)
o The Compression Application System (CAS) will hold the body in compression for
several hours each day, minimizing the expansion of the intervertebral disks and
mitigating joint injury by simulating the joint loading on Earth.
Renal Stone Formation (Risk 4)
o STEVE will decrease the net resorption of bone, which will result in a lowering of
calcium in the blood and therefore reduces the risk of renal stone formation in the
kidneys. Additionally, a low calcium diet should be instituted to help lower the demands
on the kidney.
Occurrence of Serious Cardiovascular Dysrhythmias (Risk 5) and Diminished Cardiac and
Vascular Function (Risk 6)
o A Combination Rowing and Cycle Device (CRCD) will take up minimal cargo space and
allow astronauts to exercise aerobically for extended periods of time while in transit to
Mars or on the surface of the Moon or Mars. By maintaining the overall health of the
cardiac system by exercising the system for at least an hour every day, the reduction of
functional capabilities can be mitigated.
Skeletal Muscle Atrophy Resulting in Reduced Strength and Endurance (Risk 13) and
Increased Susceptibility to Muscle Damage (Risk 14)
o
o
o
The CRCD will exercise the major muscles groups of the legs, back, stomach, arms, and
chest, helping to reduce atrophy.
A Proportional Resistive Exercise Device (PRED) will help maintain the strength of the
muscles.
A Foot Pressure Device (FPD), developed by our collaborator, Dr. Charles Layne of the
University of Houston, will increase neuromuscular activation, helping maintain the
overall health of the muscular system.
By selecting interrelated health risks, a
suite of devices and solutions is able to address
them collectively. This allows a multifaceted
approach to solving each problem while
conserving valuable resources and space on
extended manned missions. The interaction
between the various risks and aspects of the
countermeasure system are featured below.
When used on the ISS, the surface of the Moon
and Mars, and in transit to Mars, this system will
dramatically reduce the risks of cardiovascular,
muscular, and skeletal degeneration while
reducing costs and saving space and weight
when compared to current countermeasure
devices. Many of the parts of the vibrating
devices are interchangeable to reduce the
number of needed parts and facilitate repairs; all
devices are adaptable to work aboard a space
vehicle in microgravity or on the surface in a
low gravity environment.
More elaborate
descriptions of each of these components and the
potential for interaction are outlined in the next
section. Finally, the feasibility of the proposed
system is demonstrated in a description of the
complete development, prototyping and initial
testing phases STEVE, one of the key
components.
3. CONCEPT OVERVIEW
Maintaining astronaut health in space
can be categorized into two basic objectives: (1)
minimizing cardiovascular and muscular
degradation and (2) maintaining bone strength
and mass. These two principal objectives can be
accomplished through proper monitoring,
exercise, and injury prevention and treatment.
Figure 3.1: Human Health and Countermeasure – Risks and Solutions
An effective exercise regimen can be
implemented using three novel devices in our
proposed system that collectively provide a
cardiovascular workout and aid in maintaining
bone and muscle mass. Astronauts’ physical
health can be monitored using both traditional
monitoring techniques and a newer, more
revolutionary device we propose that utilizes
high frequency vibration. Traumatic injuries
experienced by astronauts in space due to the
changes in their body resulting from the
microgravity environment can also be remedied
by a fracture healing device that also employs
vibration. This suite of tools for maintaining
astronaut health should significantly improve the
effectiveness of the existing countermeasures
intended to accomplish the aforementioned basic
objectives.
due to reduced gravity are also in development
(see Section 3.2). The proposed device employs
a technique of low frequency, low magnitude
vibration that has been shown to maintain bone
mass in disuse both in animals and humans on
Earth. Presumably, disuse osteoporosis on Earth
is similar to the phenomenon experienced by
astronauts in space who are unable to load their
normally load-bearing bones.
3.1 Exercise Regimen
Astronauts will be required to spend
several hours each day exercising for missions
longer than two weeks. Even with existing
countermeasures currently employed in space,
muscle and bone deteriorate at alarming rates.
Muscle atrophy in the back and the large leg
muscles can severely disable astronauts on
missions to the Moon or Mars should they need
these muscles for strenuous exertions.
Additionally, cardiovascular health degrades in
space, resulting in arrhythmias, reduced cardiac
efficiency, and an increased likelihood of heart
attacks or strokes.
3.1.1 Spine and Trochanter External Vibration
Effecter (STEVE)
The amount of bone loss experienced by
astronauts in space over a period of one month is
comparable to the amount lost by an
osteoporotic female over an entire year. The
resulting reduction in bone strength could prove
to be extremely dangerous should an astronaut
fracture a bone that would impair his/her ability
to function. It should be noted that this critical
concern for bone health applies to lunar and
Mars missions as well as extended stays on the
International
Space
Station.
Also,
countermeasures currently used in space have
been shown to have little or no effect on the
maintenance of bone mass in space. Additional
diagnostic tools to assess the loss of bone quality
Figure 3.2: STEVE
The device, shown in the figure above, applies
vibration to strategic load-bearing regions of the
body including the femoral trochanters and the
lumbar vertebrae. Studies (Rubin, C. et al) have
shown that a vibration frequency of 30 Hz
applied for as little as ten minutes each day can
effectively maintain bone loss in disuse. The
proposed device, known as the Spine and
Trochanter
External
Vibration
Effecter
(STEVE), uses three large vibration motors that
will be worn around the waist. Two of the
vibration units rest on the femoral trochanters,
while the rear vibration unit stimulates the lower
back. In addition to the vibration applied around
the waist, a compression application system
(CAS) holds the entire body in compression to
assist in transmitting vibration through the joints
of the body (see 7. Proof of Concept). In
addition, the CAS will assist in reducing the
swelling of cartilage, especially the swelling of
the intervertebral disc. The compression
provided by the CAS will hold the vertebrae
together and aid in vibration transmission
throughout most of the body. The compression
suit consists of elastic bands providing up to 400
N of force. These elastic bands are easily
adjustable, allowing an astronaut to adjust the
desired amount of compression. The elastic
bands can hook into an astronaut’s shoes,
allowing the same suit to be worn by any
crewmember. In addition to aiding in vibration
propagation, the CAS stimulates an astronaut’s
extensor muscles to resist the compression,
providing an additional beneficial muscular
workout. The entire device is readily stored and
has an attractive weight of approximately 10 kg.
STEVE’s modularity and light weight make it an
ideal device for missions to the Moon and Mars,
and it could also be used in the International
Space Station as a supplement to current
countermeasures.
shown in the figure below, the device applies
pressure in various locations on the bottom of
the foot using solenoid pressure cells that
simulate the pressure felt by a foot.
The pattern and frequency of the
pressure stimulation can be programmed to
simulate the pressure felt by the feet in a variety
of activities such as walking or running. The
FPD has also been observed to be comforting
when worn by the astronauts due to its
simulation of a “gravity” environment. Thus,
the FPD will not only aid in neuromuscular
activation but also in reducing the disorientation
experienced by astronauts because of
microgravity. This device can be used in both
lunar and Mars missions as well as during
extended stays on the International Space
Station and will only weigh approximately 2 kg.
Unfortunately, wearing the FPD while
exercising may be somewhat uncomfortable for
the astronauts. However, the device would be
easy to use and would be relatively simple to
repair with replaceable solenoid pressure
stimulators.
3.1.2 Foot Pressure Device (FPD)
In addition to the Spine and Trochanter
External Vibration Effecter, a foot pressure
device can also be worn by the astronauts while
they perform their workouts. The foot pressure
device (FPD), based on a concept device
designed and built by one of our collaborators,
Dr. Charles Layne of the University of Houston,
has been shown to increase neuromuscular
activation significantly when worn in space. As
3.1.3 Combination Rowing and Cycling Device
(CRCD)
The proposed exercise machine will aid
in
minimizing
muscle
atrophy
and
cardiovascular health decrements by providing a
rigorous workout for even the healthiest
individuals.
The proposed exercise device
consists of a combination rowing and cycling
machine that provides a cardiovascular workout
combined with resistance training exercise
movements targeted at major muscle groups.
The primary mode of resistance will be provided
by mounting a fan blade in place of the wheel.
Additionally, a generator will be affixed to the
device to harness a fraction of the user’s energy.
Although this energy is an insufficient amount
of power to run major systems, it can be used to
power the CRCD self-sufficiently.
The
generator can be used to power headphones or
other diversions for the user. As pictured in the
figure below, the device has the basic layout of a
rowing machine.
However, the fan wheel may be rotated
by applying work through an additional cyclelike mechanism on the device. The astronaut
Figure 3.3: Foot Pressure Device
Figure 3.4: Sample Cycling/Rowing Device
can either be seated “above” the wheel to work
out the legs by doing a cycling workout or
“level” with the wheel to do a rowing workout
that will exercise the legs, arms and back.
Composed mostly of titanium, the device would
weigh approximately 25 kg and take up a
minimal amount of space compared to
countermeasures currently employed on the
International Space Station. It should be noted
that this exercise device will mainly be used on
missions to the Moon and Mars due to cargo
space limitations. However, the same design
can also be implemented on the space station.
The image shown is a commercial rowing and
cycling machine. A similar design will be used
but adapted so that either the rowing action or
pedaling would spin the fan. Unfortunately, the
device is limited in that it can only be used for
three different exercises that mainly target the
legs. Certain components of the CRCD could
also be relatively difficult and time consuming
to repair.
3.1.4 Proportional Resistive Exercise Device
(PRED)
To maintain muscle strength and
volume, a resistive exercise device is needed.
NASA has developed resistive muscle
countermeasure systems such as the Advanced
Resistive Exercise Device (ARED) and the
Interim Resistive Exercise Device (IRED).
However, the ARED is probably too large to be
used on long distance missions out of orbit. The
IRED is a better candidate in this aspect, but
there are problems associated with the
mechanism for resistance, notably its inefficient
repair requirements. The proposed solution is
the development of an IRED-sized unit
incorporating
visco-elastic
resistance
proportional to the pulling speed. The PRED is
small and uses canisters filled with a viscous
polymer that is infiltrated with ferrous metal
fibers and an integrated adjustment tool that
allows astronauts to perform a variety of
exercises such as squats, dead lifts, and bench
press.
The composite polymer changes
viscosity, and therefore resistance, when
permanent magnets are brought in close
proximity. Only small canisters are needed to
achieve a significant effect. This unit will be
most useful on long-term missions on the Moon
or missions to Mars. It also circumvents some
inherent problems with using pneumatic force in
that a failure could result in damage the shuttle
or injury to the astronauts.
Figure 3.5: Proportional Resistive
Exercise Device
3.2 Monitoring Physical Health of Astronauts
The physical health of astronauts can be
monitored using widely used techniques such as
electrocardiograms
and
ultrasounds.
Electrocardiograms can be used to monitor the
astronauts’ cardiovascular health and the effects
of the proposed cardiovascular workouts. An
ultrasound device can be used to assess bone
density of astronauts through measurements of
speed of sound and broad band attenuation in
bone. We propose the use of a novel diagnostic
device, dubbed the OsteoSonic, designed and
developed by Dr. Michael Liebschner of Rice
University, which can be used to assess bone
integrity of astronauts at various anatomic sites.
This device will allow astronauts to track the
effect of microgravity on their bone mass while
determining the efficacy of the proposed bone
countermeasure device.
3.2.1 The OsteoSonic
The use of acoustic vibration as a
diagnostic tool for measuring the progression of
bone fracture healing was developed in the early
1990s. The OsteoSonic consists of a low
frequency vibration generator, an accelerometer,
and a force gauge. The device applies different
frequencies of vibration and then measures the
resulting response by the bone. The resulting
amplitude and frequency of the vibration emitted
from a bone from an applied vibration is
dependent on the properties of the vibrated bone.
Osteoporotic bone tends to produce a different
response than normal bone from the same
location. Also, current research foresees that
this technology will be able to differentiate
between age-related osteoporosis and disuse
osteoporosis on bone fragility, something
conventional bone density scanners are not
designed for.
The OsteoSonic collects data from a
wide range of frequencies and develops response
functions based on the frequency vs. amplitude
map for a specific application site.
This
information can then be processed by a
computer to determine the efficiency of bone to
carry load (stress-backbone) and therefore the
fracture risk of the astronaut. This device will
allow astronauts to monitor changes in their
bone quality with prolonged exposure to
microgravity.
Additionally, it will allow
astronauts to assess their exercise regimen,
allowing them to make changes based on the
rate of bone loss. If the efficiency of bone to
carry load is decreasing at an unacceptable rate,
the astronauts will need to feasibly extend the
periods for which they apply vibration to their
bodies using STEVE. As pictured in the figure
below, the device is small and handheld,
weighing less than 1 kg, making it ideal for
lunar and Mars missions as well as use on the
International Space Station. Because most of the
OsteoSonic’s components are complex circuits
and electrical devices, its repair would be rather
difficult in space. Thus, it is recommended that
the astronauts would take up replacement parts
for these components should they fail.
Figure 3.6: The OsteoSonic
The current development status of the
OsteoSonic device includes the fabrication of
two functioning prototypes that are actively used
in a research setting on cadaveric tissue and live
human subjects. The device has won the 2004
“Create the Future” award sponsored by NASA
Tech Briefs and Emhart Corporation.
3.3 Healing Injuries
3.3.1 Vibration Fracture Healing Unit (VFHU)
One of the critical health risks facing
astronauts on extended missions on the
International Space Station (ISS), or on missions
to the Moon or Mars, is the treatment of bone
fracture. Generally, the risk of bone fracture on
a routine mission is considered low, but, due to
the increased risk of fracture with decreasing
bone mass during long-term missions in
microgravity, the risk of fracture is a problem
that must be considered for long-term missions.
It is also expected that astronauts will perform
hard labor during EVAs and at planetary
installations. Ideally, the development of
effective countermeasures for loss of bone mass
will reduce this risk. However, on the rough,
rocky surfaces on Mars, there will always be a
baseline risk of fracture as a function of the
foreign and dangerous terrain the astronauts may
encounter. Importantly, many studies over the
last fifteen years have discovered a mechanism
that will aid in the treatment of bone fractures.
Once the scientific community accepted
the merit of using mechanical forces such as
vibration for assessing the mechanical properties
of healing bones, the other uses of vibration in
this area were explored. In 1994, a Chinese
research group discovered that mechanical
forces imparted through vibration improved the
rate and quality of fracture healing. This study
tested the effects of 5 different vibration
frequencies on the fracture healing of the radius
of 76 rabbits. Fractures were shown to heal
faster and become stronger when exposed to
vibration, with frequencies of 20 and 50 Hz
exhibiting the most dramatic increases. Since
this report, many studies have been conducted
evaluating the beneficial effects of vibration on
bone maintenance and remodeling.
is a small housing made from composite
material that contains a DC motor with a
mounted eccentric flywheel for generating
vibration. The voltage supplied to the motor
controls the frequency of the vibration. The
recommended frequency is 30 Hz because this
has been found to be the most therapeutic in
other aspects of human bone maintenance. Once
the motor is in place to impart local vibration
stimulation to the site of fracture, the cuff is
inflated to ensure a tight, comfortable fit that
will increase the transmittance of vibration from
the unit into the subject.
The proposed device is lightweight and
easy to use.
There are considerable
complications associated with the treatment of
bone fractures in microgravity. Although the
concept has been shown to work on Earth, the
lack of gravity and reduced loads on the bone
could make fracture healing a very slow and
inefficient process. However, the VFHU serves
the dual purpose of immobilizing the injury and
applying a therapeutic mechanical stimulation.
This device is inexpensive to construct and
develop, and can be tested in a few years.
Problems to overcome include the
vibration propagation in soft tissue, basically
from the skin to the bone, and the application of
this device on anatomic sites other than
extremities. We believe that the first hurdle can
easily be overcome as soft tissue acts as a
damper; therefore, adjusting the frequency and
amplitude will allow control of the vibration
energy transmitted to the anatomic site of interest.
Further studies will be necessary related to
expanding the usage for other anatomic sites.
4. PROJECT COST AND TIMELINE
Figure 3.7: Vibration Fracture Healing
Device
We have developed a conceptual
fracture healing device for use on long-term
missions on the ISS, for the journey to the Moon
or Mars.
The conceptually simple device
consists of an inflatable bladder encased in a
cloth cuff. The deflated cuff is wrapped around
the site of fracture and cinched tight. Around
the cuff is an adjustable band with a sliding
vibration unit attached to it. The vibration unit
The suite of tools and applications
developed by our team and presented in this
proposal are inexpensive to develop, easy to test,
and fit seamlessly into the timeline established
by NASA for its future missions.
First, the construction of basic, testable
prototypes of each of these devices will take
only a matter of months. The materials needed
to create each of the proposed devices are
common and inexpensive stock items.
Production of device parts and assembly is
.
Table 4.1: Advanced Space Health Maintenance Specifications
Device
Volume
Mass (kg)
Estimated Cost
(1,000’s cm3)
(in $1000’s)
450
55
30
30
400
30
995
feasible by only a few individuals. Research and
testing of device efficacy will take a few years,
as human subjects studies and animal tests are
involved. However, the methods by which these
devices function are simple and well understood.
Efficacy of all devices can be shown
through testing on the ISS, meaning the
complete system could be ready for
implementation within a matter of years.
Importantly, the research and development costs
of the entire proposed suite of tools will only be
a fraction of the cost of many projects currently
undertaken by NASA. With a relatively small
investment, NASA can take a major step
towards solving several critical health problems
that astronauts will face on long-term missions.
If the current health concerns are not addressed,
long-term human space flight will likely be
impossible regardless of the care with which the
missions are planned. Table 4.1 contains a
summary of the key features of proposed
devices.
Secondly, research and development of
these devices can be completed in 5 years. This
falls well within the proposed NASA timeline
that plans a return to the Moon by 2015 and a
manned mission to Mars by 2030.
Cardiovascular and musculo-skeletal health
problems encountered by astronauts in
microgravity must be addressed before these
missions can be undertaken. The suite of
devices we have proposed is an inexpensive,
highly feasible and effective way to meet the
goal of maintaining astronaut health. Figure 4.1
portrays the total cost of developing the space
health maintenance system each year.
25
10
3
3
25
4
70
3,500
4,500
1,500
4,700
4,050
1,800
20,050
All
All
All
All
All
All
Estimated Cost by Year
6000
5000
Cost (in $1000's)
CRCD
STEVE
FPD
VFHU
PRED
OsteoSonic
TOTAL
Mission
4000
3000
2000
1000
0
1
2
3
4
5
Year
Figure 4.1: Yearly Costs
Table 4.2 shows the proposed 5 year
timeline of the devices. Phase I involves the
development and construction of a fully
functioning device for testing purposes. Next,
animal testing, bed rest studies, and KC-135
testing characterize Phase II. Phase III
encompasses final testing on Earth and flight
testing aboard the shuttle or ISS. Implementation
of the device in phase IV includes the cost of
constructing and installing the finalized device.
Figure 4.2 depicts the costs of each phase for
each device.
Construction of FPD and OsteoSonic
prototypes and preliminary testing has already
been conducted for these devices. Further flight
testing is recommended before a final device can
be implemented. Testing of the OsteoSonic has
already begun at the NEEMO 6 underwater
facility. Phase III testing aboard the ISS will
demonstrate its efficacy, and a final device can
be implemented in Phase IV.
rest studies, KC-135 testing, and additional
necessary studies. Phase III will be installation
and flight testing aboard the ISS.
The initial prototype construction of
STEVE will be inherently more expensive due
to electronics and composite materials used in
the device. Phase II and III will involve bed rest
studies on Earth and trials in orbit on the ISS to
verify the efficacy of the vibration mechanism.
Costs for developing a VFHU prototype
will be moderate. Most of the expense for the
device can be attributed to animal testing during
Phase II and Phase III, both on Earth and on the
ISS, respectively. These tests aim to show the
efficacy of vibration for fracture healing in any
environment.
The development and testing of the
PRED will be similar to the cost and schedule of
the CRCD. Design and construction of the
magnetic isolation and visco-elastic ferrous
polymer raise the initial cost of device
construction.
Estimated Cost by Device
Phase 4
Cost (in $1000's)
5000
Phase 3
4000
Phase 2
Phase 1
3000
2000
1000
D
VF
H
U
PR
ED
O
st
eo
So
ni
c
FP
CR
CD
ST
EV
E
0
Figure 4.2: Device and Phase Costs
The CRCD will have a short
construction and prototyping phase because of
its similarity to existing rowing machines and
the cycle ergometer already in use. The bulk of
the cost for CRCD development will derive from
testing during Phase II, which will consist of bed
Table 4.2: Project Timeline
CRCDSTEVE-Spine
FPD
VFHU – Fracture Treatment
PRED - exercise
OsteoSonic-Diagnostic
I. Development
Year 1
I
I
III
Year 2
II
Year 3
Year 4
Year 5
IV
IV
III
III
IV
IV
III
II
III
IV
I
II
I
II
II. Animal/Human Testing
5. IMPLEMENTATION
5.1 Tool Suite Implementation
Upon completion of the final designs
and testing for all of the modular components,
long-term missions must be properly equipped
with the correct combination of devices. The
team proposes that each mission should be
provided with one STEVE unit and one FPD
unit for every two astronauts. This distribution
allows cargo weight and storage space to be
minimized while still allowing several astronauts
to use the devices for extended periods. Each
spacecraft or manned outpost should be
equipped with one CRCD, one PRED, one
II
III
III. Flight Testing
IV
IV. Implementation
OsteoSonic, and two VFHU's at a minimum, and
perhaps more in the case of a manned outpost.
Additionally, in the event of breakdowns or
malfunctions, missions should be equipped with
redundant vibration units for STEVE, extra
VFHU vibration units, and replacement
components for OsteoSonic repairs. Including
these easily replaceable component parts
requires minimal additional storage space and
also streamlines repairs significantly, saving
valuable astronaut time.
5.2 Astronaut Health Maintenance Regimen
During a long-term mission, each
astronaut will need to follow an individually
tailored health maintenance regimen that
incorporates the devices included in this tool
suite and any additional devices that may be
developed in the future. Specifically, it is
recommended that astronauts exercise daily
using the CRCD and PRED machines for up to
one hour each to properly maintain
cardiovascular and muscular health.
Also,
STEVE should be worn a minimum of fifteen
minutes per day, and the FPD should be worn at
some length daily. Conceivably, STEVE and/or
the FPD can be worn while exercising with the
CRCD and the PRED to enhance their training
benefits, although further testing is needed to
verify their effectiveness and comfort. Finally,
health maintenance examinations will need to be
performed regularly using the OsteoSonic and
other diagnostic devices, with each astronaut’s
training regimen being adjusted accordingly.
Disciplined use of the exercise devices provided
by this tool suite will greatly facilitate the
successful maintenance of the physical well
being of each astronaut during long-term
missions.
6. CRITICAL ANALYSIS
For the project to be technically
successful, several potential difficulties must be
overcome. Currently, a substantial amount of
effort goes into isolating vibration caused by the
exercise equipment from the rest of the
spacecraft. Developing the appropriate vibration
isolation system for the PRED and CRCD could
potentially double the amount of weight
required. Other technology developed by NASA
[NASA Tech Briefs article] can be incorporated
in our system to address this issue.
Additionally, while the devices are built to
include a suite of exercises, some redundancy
may be necessary as repairs may be impractical.
The VFHU offers therapeutic benefit for long
bone fractures; if a fracture is sustained in the
pelvis or vertebra, there is less that can be done
to treat it. Finally, the OsteoSonic can be useful
in assessing fracture risks and assigning mission
responsibilities accordingly, but it is important
to recognize that it is a diagnostic tool. These
issues do not ruin the prospects of a successful
project, but they must be acknowledged in the
design phase to enable this success.
7. PROOF OF CONCEPT
A key feature of the proposed project is
the feasibility of the claims, specifically the ease
with which they may be incorporated into an
eventual manned mission. Accordingly, the
theoretical work of the project was
supplemented heavily over the last year by the
design and construction of a physical device.
The development of this prototype is useful
because it demonstrates the ease of
implementation of the preceding proposals.
Over the course of two semesters, a student
design team was able to construct, on a
shoestring budget, two separate prototypes of
STEVE, a key component of the Advanced
Space Health Maintenance System. The second
generation prototype is described below.
7.1 Development of STEVE
Specifically, the team built a device
intended to reduce the rate of bone loss in
microgravity. The prototype underwent a series
of revisions throughout the year as it was
fashioned to meet the original design criteria.
Lightweight, modular, cost effective, and
convenient, readily accessible materials were
used to construct the device. The device uses
instrument grade brushless motors with eccentric
flywheels to apply vibration to the trochanters
and lumbar vertebra. These motors are encased
in custom-made housing fabricated from a
carbon fiber–KEVLAR® composite weave.
The carbon fiber is lightweight and structurally
Figure 7.1: Vibration Application System
strong while the KEVLAR® ensures that the
risk of puncture damage is negligible.
The
motor units are mounted on an adjustable belt
worn around the waist to ensure that they are
positioned correctly.
In addition to the application of
vibration, STEVE is designed to hold the
body in axial compression. While this does
not replace the compressive force of gravity
completely, it is intended to load the body in
an analogous way. The primary purpose for
this action is to help ensure the effective
propagation of vibration through the body.
While vibration is easily transferred through
the bones, it is necessary to make sure it
passes through joints as well. The team
decided that the best way to do this is to
ensure that the joints are held together by
applying a continuous compressive force.
Thera-Band® elastic tubing runs from
the central belt towards the shoulders and feet of
the person to apply this force. At the shoulders,
the tubing is permanently attached to a carbon
fiber shoulder harness that was fashioned to fit
one of our team members. The Thera-Band®
runs through knee sleeves to remain parallel to
the legs and clips into the shoes of the astronaut.
The bands can be attached to the belt and
adjusted by the user to vary the compressive
load. The ideal compressive magnitude must
still be verified; however, the wide range of
possible prototype bands allows the user to
select the desired magnitude of compressive
force--even values exceeding the normal
compressive force experienced as a result of
gravity on Earth.
A critical feature of the device is the
user adjustability that it provides. As noted
above, the user can freely position the vibration
units anywhere on the belt to ensure that they are
pressed against the relevant physiological sites.
Metal clips at the bottom of the leg bands allow
the suit to work with any astronaut’s normal
shoes. Finally, the canvas bands that attach the
Thera-Band® to the belt allow for a wide range
of compressive forces over a range of user
heights that encompasses the 5% Asian female
to 95% American male. This versatility within
the prototype is essential because it allows every
Figure 7.2: STEVE showing Compression
Application System
astronaut to use the same model, thereby
reducing the cost and, more importantly, the
weight and volume requirements.
7.2 Claims
The construction of the prototype was
intended to demonstrate the feasibility of one
aspect of this overall concept and was not done
in order to build the specific device to be used in
space. .Several positive aspects of the design and
construction process can be addressed regarding
this development process. By extending the
conclusions to the other components outlined by
the Advanced Space Health Maintenance
System, the feasibility of the project becomes
readily apparent.
7.2.1 Project Budget
It must be stressed that the prototype
was built easily within the budget of a senior
design group. The team spent just over $1200
on materials for the design, construction and
testing of two prototypes during both semesters
combined. This is well within the budget of a
NASA mission, especially considering that it
costs far more to launch a just one pound of
supplies into orbit. This cost also reflects
inefficiency as the result of a student design
team. Taking into consideration higher NASA
standards as well as the higher efficiency of the
project engineers, an estimate for the
development cost of a NASA-grade STEVE is
approximately $4.5 million. This covers the cost
of higher quality materials as well as the salary
of the engineers and scientists over a several
year project.
7.2.2 Simplicity of Construction
Theoretically, the device can be fully
developed, constructed, and tested well before
any extended manned mission is scheduled to
begin. The five man team spent approximately
510 work-hours on activities directly related to
the construction of both prototypes. Within a
few weeks a NASA team could revamp and
complete a third prototype with tolerances to
their own specifications. Almost immediately
afterward, testing can begin to fully determine
the effectiveness of the device in accomplishing
the stated goal of reducing bone density loss in
microgravity.
7.2.3 Efficacy of Design
The effectiveness was initially tested
using a uniaxial accelerometer to measure
vibration propagation caused by wearing the
prototype. Vibration was measured at six
anatomical sites with the subject in both the
standing and supine positions. An initial set of
data appears successful as shown in Figure 7.3,
but more comprehensive testing would need to
be performed during Phase II testing to establish
statistically significant results. Preliminary
results obtained from our study suggest that the
vibration applied around the hip area does
propagate through the body and that the
compression system has a significant effect on
propagation.
Figure 7.3: Vibration Propagation Results
Ultimately, the design is only successful
if it reduces the rate bone loss. It is essential to
establish this fact before undertaking a longterm mission, unfortunately, the only way to
completely test the device is to issue it to
astronauts on the ISS. Naturally, this is beyond
the means of a student design team, so
alternative testing procedures had to be created.
Through collaboration with Dr. Layne at the
University of Houston, the team tested the effect
of the device on EMG signals. While this is not
directly related to the bone loss, the presence of
a physiological response was deemed to be a
step in the right direction. There is uncertainty
related to the mechanism by which vibration
stimulates bone maintenance; it is possible that
micro-contractions act as an intermediary.
Although the team found no significant
muscle activity generated by 30 Hz vibrations,
preliminary research indicates that there is a
response at 150 Hz, the applied vibration
stimulus of the first semester prototype.
Partially as a result of this research, the team
proposes that a future prototype might oscillate
between these ranges to achieve the optimal
therapeutic effect.
8. CONCLUSION
We have proposed a unique health
maintenance system that will be simple and
inexpensive to implement as compared to other
NASA projects. Most importantly, this system
will enable the long-term exploration of the
Moon and Mars. The system is versatile and can
be used aboard the transit vessels or on the
surface of a planet. Each component has been
designed so that it is easily adjustable for use in
any gravity environment.
Although
the
system
is
not
comprehensive, it represents an attractive early
solution to some of the most difficult obstacles
faced when considering habitation of the Moon
or visiting Mars. Some of the technologies have
not been proven in space, but we have proposed
a simple system for the short-term testing of the
devices on Earth and onboard the ISS to prove
their efficacy.
By combining existing
knowledge
of
space
physiology,
and
revolutionary clinical practices in use on Earth,
we hope to enable the exploration of any part of
our solar system without endangering the
physical health of the astronaut.
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