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Diving in SpaceDiving in Space
Mik G h dtMike Gernhardt
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 1
https://ntrs.nasa.gov/search.jsp?R=20090002616 2018-05-09T12:03:01+00:00Z
Biomedical and Technological Challenges of EVABiomedical and Technological Challenges of EVA
• Decompression (denitrogenation required to work in low pressure suit (4.3 psi))
• Thermoregulation (-120oC to + 120oC)g ( )
• Nutrition (200 kcal/hr requirement)
• Hydration (1 liter/EVA)y ( )
• Waste Management
• Radiation
• Micrometeoroids and Orbital Debris
• Suit Trauma
• Mobility/Dexterity: current pressurized suits reduce mobility and dexterity
Visibilit
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 2
• Visibility
Type II DCS – Percentage of All DCS vs. Diving MethodsType II DCS – Percentage of All DCS vs. Diving Methods
9 01 0 0
4 05 06 07 08 0
01 02 03 0
l l ic k s A
Comme rc
ia l
R ecreat io
n al
S cien tific
USN Sa fety
Cente
rUSN D
ive Tria
ls
B rook s
NASA
US• Character of Altitude DCS Different from Diving DCS
• Undersaturated Neurological Tissues
From DAN, 2005
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 3
• Undersaturated Neurological Tissues
• “Softer Bubbles” Metabolic Gases
Altitude DCS - Nitrogen Elimination during Oxygen PrebreatheAltitude DCS - Nitrogen Elimination during Oxygen Prebreathe
2500
V
V60-90
Cumulative NitrogenElimination(ml)
N 2 e l im in a t io n in 5 a n d 1 0 m in u t e h a lf -t im e c o m p a r t m e n ( ~ b r a in a n d s p in a l
c o r d )1 0
V0-30
V30-60
4
6
8
1 0
030 60 90 120 1500
Time (min)180
0
2
0 2 0 4 0 6 0 8 0
Time ( minutes)
- Over 50% of nitrogen eliminated in first 30 minutes- Brain, spinal cord Halftime ~ 5-10 minutes, muscle and skin halftimes
- 15-25 minutes at resting conditions
Time ( minutes)
- 15-25 minutes at resting conditions - Resting prebreathe reaches point of diminishing return for reducing pain
only DCS- Type II DCS incidence higher on “Zero Prebreathe”
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 4
Gerth, W.A., R.D. Vann, N.E. Leatherman, and M.D. Feezor. 1987. Effects of microgravity on tissue perfusion and theefficacy of astronaut denitrogenation for EVA. Aviat. Space Environ. Med. 58(9, Suppl.): A100-105
Shuttle Pre-breathe Ground StudiesShuttle Pre-breathe Ground Studies
Two Pre-breathe protocols approved
• 4 hour in-suit resting oxygen pre-
for flight operation
g yg pbreathe
• 12 hr 10.2 psi staged decompression procedure
• R value ( tissue ( )/tension (360)/suit
pressure)= 1.65
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 5
Flight Experience Shuttle 10.2 psi Staged Protocol – Zero DCS Flight Experience Shuttle 10.2 psi Staged Protocol – Zero DCS
120
Time at 10.2 psi prior to 60
80
100
120
Numbe r of EVAs
shuttle EVA
0
20
40
12-16 16-20 20-24 24-144Time (hours)Time (hours)
25
dex
12 hr*
Theoretical Tissue Bubble growth as a function of
10
15
20le
Gro
wth
Ind
0 m
in T
issu
e 12 hr
16 hr*
20 hr*
growth as a function of 10.2 exposure time
0
5
0 100 200 300 400EVA Time (min)
Bub
bl 480
24 hr*
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 6
EVA Time (min)
Defining and Controlling Risk in Operational Research Programs – Example of Prebreathe Reduction Program (PRP)Defining and Controlling Risk in Operational Research Programs – Example of Prebreathe Reduction Program (PRP)
ISS OvernightCampout
Enabling Counter Measure Research
( NASA TRL 3/4)Background
40
60
80
100
% D
CS
20/26 (77%)
11/26 (42%)
*Arm & leg work at 75% VO2 max with
seated subjects
p=0.03
0
20
Rest 0:10 Heavy Work*1:00 O2 Prebreathe
USAF prebreathe exercise
Shuttle Prebreathe Ground Trials (~ 25% DCS, ~ 5% symptoms that would
Limitations•Timeline, back to 40
60
80
CS
10/20
Legs (p=0.0008)Arms (NS)
USAF prebreathe exercise
symptoms that would terminate an EVA.) Acceptable Risk?- 4 hour prebreathe- 10.2 psi staged protocol
,back EVAs, •02 usage,ISS 02 concentration•crew isolation and
0
20
40
Ambulatory Non-Amb.
% D
2/203/21
1/21
95% CI
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 7
p g p- 146 EVAs exposures with no reports of DCS
comfortDuke, NASA micro-gravity
simulation ( non ambulation)
Enabling ResearchEnabling Research
10 minutes 75% V02peak 88% lower
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 8
10 minutes 75% V02peak, 88% lower body, 12% upper body
Prebreathe Reduction ProgramPrebreathe Reduction Program
• Start by defining acceptable DCS risk for ISS mission and developing
Prebreathe ReductionLaboratory Studies-5 Year Operational developing
accept/reject limits for countermeasure trials
• Early development
-5 Year OperationalResearch Plan
Integrated DecompressionStress Predictive Model
Early development focused on delivering acceptable/effective counter measure
AcceptableDCS RiskDefinition
2 Hr.Prebreathe
Protocol
1.5 Hr.Insuit
Prebreathe
Relationship between
Micro-g sim. andexercise
Break inPrebreathe
Studies
SupportingStudies
• Later development focused on increased efficiency and improved scientific
Phase 1 √
Phase 2 √
Phase 3 √
Phase 4 √
Phase 5.1 **
Phase 5.2
Phase 5.3
Phase 5.4
Brooks Studies *
adynamia cross over study
JSC
Phase 6.1
Phase 6.XX
- Lactate measurements
- Oxygen Consumption *
- Cardiac Output
- Blood flow
- Nitrogen Elimination
scientific understanding of counter measure mechanisms
Phase A **
EVA exercise simulations
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 9
Accept: DCS Accept: DCS << 15% and Grade IV VGE 15% and Grade IV VGE << 20% , @ 95% 20% , @ 95% C.lC.lReject: DCS Reject: DCS >> 15% or Grade IV VGE 15% or Grade IV VGE >> 20% , @ 70% 20% , @ 70% C.lC.l
Multi-Center Study: NASA, Duke, DCIEM, Hermann UTMulti-Center Study: NASA, Duke, DCIEM, Hermann UT
2hr oxygen prebreathe
Exercise 10 mins @ 75% V02peakAnd/or light exercise (160-253 Kcal/hr)
Micro-gravity simulation( non-ambulation)
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 10
Simulated EVA exposure at4.3 psi 4 hrs Use of “Suit Simulator” for
EVA Exercise
Prebreathe TrialsPrebreathe Trials1010 DCSDCSPhase I
Phase II
Ph III
40 min40 min
LightLight
RestRest
RestRest
RestRest
1010minmin75%75%
VOVO2 peak2 peak
4 hr4 hr
EVAEVA
SimuSimu--
DCSDCS19%19%
0%0%
22%22%Phase III
Phase IV
ActivityActivityRestRest
RestRest95 min Light Activity95 min Light Activity
SimuSimu
lationlation
22%22%
14%14%
PRP Phase I-IV 2 hr oxygen prebreathe exercise protocols
60
70
80
DCS
DCSVGEn=47
n=9• High intensity exercise (75% peak oxygen
20
30
40
50
60DCSor
Grade IVVGE(%)
n=56
n=45
(75% peak oxygen consumption [VO2 peak])
• Low intensity activity (5.8 mL·kg-1·min-1 VO2)
0
10
I II III IVPhase
( g 2)
• Neither High or low intensity exercise was acceptable
C li Hi h ith DCS and Grade IV VGE observations (shown with 95%
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 11
• Coupling High with low intensity exercise was acceptable
DCS and Grade IV VGE observations (shown with 95% upper confidence limit bars dashed lines indicating accept levels for DCS and VGE incidences)
Exercise and Inert Gas KineticsExercise and Inert Gas Kinetics
P1N2 = P0 + (1 - exp – k1t ) * (Pa - P0),
k1 = [(1 / exp (-λ * mL*kg-1*min-1)) / 519 37]k1 = [(1 / exp (-λ mL kg-1 min-1)) / 519.37].
Model Predictions vs Actual
20
25
30
35
0
5
10
15
20%DCS
I II III IV V 1 V 3 V 4I II III IV V-1 V-3 V-4
PRP Trials
Hosmer-Lemshow Goodness of fit statistic = 2.188 with 5 degrees of freedom, p = 0.82 ( significance > .05)
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 12
Exercise Prebreathe Protocol: Experience to DateExercise Prebreathe Protocol: Experience to Date
• Overview- The exercise prebreathe protocol has been used successfully on 34 EVAs from the International Space Station (ISS)- no DCS
• Five Shuttle assembly flights and two increment EVAs• Starting in July 2001• Starting in July 2001
• These assembly missions would have been difficult or impossible to execute as base-lined, without the protocol
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 13
A United States Airlock: Doorway to SpaceA United States Airlock: Doorway to Space
U.S. “Quest” Airlock
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 14
The Challenge of Moving Past ApolloThe Challenge of Moving Past Apollo
A ll k bl h hi t• Apollo was a remarkable human achievement
• Fewer than 20 EVAs, maximum of three per mission
• Constellation Program up to 2000 EVAs over• Constellation Program, up to 2000 EVAs over the 10 year Lunar program
• Limited mobility, dexterity, center of gravity and other features of the suit required significant crew compensation to accomplishsignificant crew compensation to accomplish the objectives. It would not be feasible to perform the constellation EVAs using Apollo vintage designs
• The vision is to develop an EVA system that isThe vision is to develop an EVA system that is low overhead and results in close to (or better than) one g shirt sleeve performance i.e. “ A suit that is a pleasure to work in, one that you would want to go out and explore in on your day off”day off
• Lunar EVA will be very different from earth orbit EVA – a significant change in design and operational philosophies will be required to optimize suited human performance in lunar
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 15
opt e su ted u a pe o a ce u agravity
Challenges for EVA on the MoonChallenges for EVA on the Moon• Dealing with risk and consequences of a significant Solar Particle Event g q g
(SPE) • Long duration missions with three 8hr EVAs per person per week
– Apollo suits were used no more than 3 times– Individual crewmembers might perform up to 76 EVAs in a 6-month missionIndividual crewmembers might perform up to 76 EVAs in a 6 month mission– Suit-induced trauma currently occurs with even minimal EVA time
• With Apollo style un-pressurized rover (UPR), exploration range is limited by EVA sortie time and 10 km walkback constraint
– Science community input that optimal scientific return within this range could be– Science community input that optimal scientific return within this range could be accomplished within ~ 30 days of EVA
– Two UPRs could extend exploration range up to 15-20 km (crew-day limited)• Apollo highlighted the importance of dust control for future long duration
missions• Increased Decompression Sickness (DCS) risk and prebreathe requirements
associated with 8 psi 32% O2 cabin pressure versus Apollo with 5 psi 100% O2
• The high frequency EVA associated with the projected lunar architectures g q y p jwill require significant increases in EVA work efficiency (EVA prep time/EVA time)
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 16
“The Wall of EVA”“The Wall of EVA”“The Wall”
250
ISS Construction (projected)
“The Wall”
200
150
A H
ours
100EVA
GeminiApollo/Skylab
Pre-ChallengerShuttle Shuttle
50Apollo/Skylab
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 17
0
1966
1968
1970
1972
1974
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1984
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1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
Year
“The Mountain of EVA”“The Mountain of EVA”
5000“The Mountain”
3500
4000
4500 Available Lunar EVA Hours (LAT-2 Option 2) – based on Three 8 hour EVAs per week using Unpressurized Rovers
2500
3000
3500
A H
ours
g pNeed to extend range well
beyond 10 km
1500
2000EV
A
Gemini “The Wall”
500
1000ISS Construction (projected)
Gemini
Apollo/Skylab Pre-ChallengerShuttle
Shuttle
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 18
0
1966
1968
1970
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2002
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2020
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Year
Intermittent Recompression - BackgroundIntermittent Recompression - Background
C t l f l f• Current plans for lunar surface exploration include Small Pressurized Rovers (SPRs) that are quickly ingressed and q y gegressed with minimal loss of consumables
• This capability enables crew members to perform multiple short extravehicular activities (EVAs) at different locations in a
9Recompression(EVAs) at different locations in a
single day versus a single 8-hr EVA
5
6
7
8
psia
)
Cabin Pressure
p
• Previous modeling work and empirical human and animal data indicate that the intermittent recompressions may reduce
2
3
4
5
Pres
sure
(p
EVA EVASuit
Pressure
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 19
recompressions may reduce decompression stress
0
1
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Time (hours)
Tissue Bubble Dynamics Model (TBDM)- Provides Significant Prediction and Fit of Diving and Altitude DCS DataTissue Bubble Dynamics Model (TBDM)- Provides Significant Prediction and Fit of Diving and Altitude DCS Data
• Decompression stress index based on tissue bubble growth dynamics (Gernhardt, 1991)
• Diving: n=6437 laboratory (430 DCS cases)– Logistic Regression Analysis: p <0.01
H L h G d f Fit 0 77– Hosmer-Lemeshow Goodness of Fit = 0.77 • Altitude: n=345 (57 DCS, 143 VGE)
– Logistic Regression Analysis (DCS): p <0.01 – Logistic Regression Analysis (VGE): p <0.01 – Hosmer-Lemeshow Goodness of Fit (DCS): p = 0.35Hosmer Lemeshow Goodness of Fit (DCS): p 0.35– Hosmer-Lemeshow Goodness of Fit (VGE): p = 0.55
r = Bubble Radius (cm)t = Time (sec)t = Time (sec) a = Gas Solubility ((mL gas)/(mL tissue))D = Diffusion Coefficient (cm2/sec)h(r,t) = Bubble Film Thickness (cm)Pa = Initial Ambient Pressure (dyne/cm2)v = Ascent/Descent Rate (dyne/cm2⋅cm3)g = Surface Tension (dyne/cm)M = Tissue Modulus of Deformability (dyne/cm2⋅cm3)
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 20
M Tissue Modulus of Deformability (dyne/cm cm )PTotal = Total Inert Gas Tissue Tension (dyne/cm2)Pmetabolic = Total Metabolic Gas Tissue Tension
Gernhardt M.L. Development and Evaluation of a Decompression Stress Index Based on Tissue Bubble Dynamics. Ph.D dissertation, University of Pennsylvania, UMI #9211935, 1991.
Intermittent Recompression - BackgroundIntermittent Recompression - Background
• Intermittent recompression during saturation decompression was previously proposed as a method for decreasing decompression stress and time (Gernhardt,1988)
– Gas bubbles respond to changes in hydrostatic pressure on a time scale much faster than the tissues
• Intermittent recompression (IR) has been shown to decrease decompression stress in humans and animals (Pilmanis et al. 2002, Møllerløkken et al. 2007)
6437 laboratory dives (430 DCS cases)
Gernhardt, M.L. Mathematical modeling of tissue bubble dynamics during decompression. Advances in Underwater Technology, Ocean Science and Offshore E i i V l 14 S b ibl T h l S i t f U d t T h l 1988
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 21
Engineering, Volume 14: Submersible Technology. Society for Underwater Technology, 1988.Pilmanis A.A., Webb J.T., Kannan N., Balldin U. The effect of repeated altitude exposures on the incidence of decompression sickness. Aviat Space Environ Med; 73: 525-531, 2002.Møllerløkken A, Gutvik C, Berge VJ, Jørgensen A, Løset A, Brubakk AO. Recompression during decompression and effects on bubble formation in the pig. Aviat Space Environ Med; 78:557-560, 2007.
DiscussionDiscussion
A
BB
20
8101214161820
Gro
wth
Inde
x59% DCS
02468
0 100 200 300 400Time (min)
Bub
ble
6% DCS
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 22
Pilmanis A.A., Webb J.T., Kannan N., Balldin U. The effect of repeated altitude exposures on the incidence of decompression sickness. Aviat Space Environ Med; 73: 525-531, 2002.
DCS Incidence TBDM PredictionsTime (min)
Intermittent Recompression - 3 x 2hr EVA at 4.3 psiIntermittent Recompression - 3 x 2hr EVA at 4.3 psi40
35
40
25
30
dex
(BG
I)
0 5hr between 2hr EVAs
6hr Continuous EVA
20
Gro
wth
Ind 0.5hr between 2hr EVAs
1hr between 2hr EVAs2hr between 2hr EVAs
10
15
Bub
ble
G
3hr between 2hr EVAs
0
5
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 23
00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Time (hours)
Floating Through the Terminator in the Sea Space ContinuumFloating Through the Terminator in the Sea Space Continuum
Diving in Space | National Aeronautics and Space Administration | Mike Gernhardt 24
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