Metabolic and Subjective Results Review of the Integrated Suit Test Series

J.R. Norcross1, L.C. Stroud1, J. Klein1, L. Desantis2, M.L. Gernhardt3

1Wyle Integrated Science and Engineering, Houston, TX; 2Lockheed-Martin, Houston, TX; 3NASA, Johnson Space Center, TX

Introduction: Crewmembers will perform a variety of exploration and construction activities on the lunar surface. These activities will be performed while inside an extravehicular activity (EVA) spacesuit. In most cases, human performance is compromised while inside an EVA suit as compared to a crewmember’s unsuited performance baseline. Methods: Subjects completed different EVA type tasks, ranging from ambulation to geology and construction activities, in different lunar analog environments including overhead suspension, underwater and 1-g lunar-like terrain, in both suited and unsuited conditions. In the suited condition, the Mark III (MKIII) EVA technology demonstrator suit was used and suit pressure and suit weight were parameters tested. In the unsuited conditions, weight, mass, center of gravity (CG), terrain type and navigation were the parameters. To the extent possible, one parameter was varied while all others were held constant. Tests were not fully crossed, but rather one parameter was varied while all others were left in the most nominal setting. Oxygen consumption (VO2), modified Cooper-Harper (CH) ratings of operator compensation and ratings of perceived exertion (RPE) were measured for each trial. For each variable, a lower value correlates to more efficient task performance. Due to a low sample size, statistical significance was not attainable. Levels of practical significance were defined as a 3.5 ml·min-1·kg-1 for VO2, ≥ 2 for RPE and ≥ 1 for CH. Results: Varying suit weight had the greatest impact on human performance of all variables tested. For ambulation, increased suit weight led to significantly higher VO2, RPE and CH at speeds ≥ 5.0 km/h on a level treadmill and at grades ≥ 20% at slow walking speeds of 2.7 ± 0.6 km/h. For exploration tasks, suit weights of 186 and 247 kilogram-force (kgf) led to consistently lower VO2, RPE and CH measures when compared to suit weights of 63, 121 and 308 kgf, with the least favorable suit weight for all non-ambulation tasks at 63 kgf. Varying suit pressure caused no significant changes in performance for any tasks evaluated. Varying subject weight in the unsuited condition, so that the same weight to the ground was matched to the suited trials, showed similar results to the varied suit weight trials for ambulation. As weight increased, VO2, RPE and CH were all higher at the same speeds and grades, but increased at a lesser rate compared to the suited trials. Varying inertial mass showed no significant changes for any tasks evaluated. When varying CG, the directly aft, directly high and certain high and aft CG locations led to the worst performance. In 1-g conditions, subjects ambulating over unknown lunar like terrain saw an average increase of 56% in metabolic rate and 7% in total distance traveled. Conclusions: Initial findings indicate that suit weight, CG and the operational environment can have a large impact on human performance during EVA. Systematic, prospective testing series such as those performed to date will enable a better understanding of the crucial interactions of the human and the EVA suit system and their environment. However, work remains to be done to confirm these findings. These data have been collected using only unsuited subjects and one EVA suit prototype that is known to fit poorly on a large demographic of the astronaut population. Key findings need to be retested using an EVA suit prototype better suited to a larger anthropometric portion of the astronaut population, and elements tested only in the unsuited condition need to be evaluated with an EVA suit and appropriate analog environment.

https://ntrs.nasa.gov/search.jsp?R=20090007828 2018-08-25T16:28:11+00:00Z

Integrated Suit Test Review – EVA Physiology, Systems and Performance Project 1

EVA Physiology, Systems and Performance Project

HRP Investigators’ WorkshopFebruary 2-4, 2009League City, TX, USA

Review of Integrated Suit Tests

Integrated Suit Test Review – EVA Physiology, Systems and Performance Project 2

Integrated Suit Test Objectives

1. Identify the individual contributions of weight, pressure, and suit kinematics to the overall metabolic cost of the MKIII suit in its POGO configuration in Lunar gravity

2. To quantify the effects of varied weight, varied mass, varied pressure, and suit kinematic constraints on human performance in Lunar gravity

3. To develop predictive models of metabolic rate, subjective assessments, and suit kinematics based on measurable suit, task, and subject parameters

Integrated Suit Test Review – EVA Physiology, Systems and Performance Project 3

Methods

• EVA Walkback Test – Overhead suspension– Treadmill

• Integrated Suit Test 1 – Overhead suspension– Treadmill

• Integrated Suit Test 2– Overhead suspension– Treadmill– Exploration tasks

• HMP Walkback Test– Overground ambulation on lunar-like

terrain• NBL/NEEMO CG Test

– Underwater– Overground ambulation– Exploration tasks

Integrated Suit Test Review – EVA Physiology, Systems and Performance Project 4

Contributions of weight, pressure and other factors to metabolic cost of MKIII in POGO configuration in Lunar gravity

Baseline, 50% Baseline, 51% Baseline, 55%

Weight, 11% Weight, 31%Weight, 39%

Pressure, 15%

Pressure, 10%

Pressure, 5%

Other Factors, 24%

Other Factors, 8%

Other Factors, 0%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

10% 20% 30%

Treadmill Incline (% Grade)

% M

etab

olic

Cos

t

Baseline, 34%Baseline, 55%

Baseline, 37%

Weight, -37% Weight, -40% Weight, -46%

Pressure, 9%

Pressure, 2%

Pressure, -1%

Other Factors, 93%Other Factors, 83%

Other Factors, 110%

-50%

-25%

0%

25%

50%

75%

100%

125%

150%Busy Board Rock Transfer Shoveling

% M

etab

olic

Cos

t

Ambulation

Exploration Tasks

Integrated Suit Test Review – EVA Physiology, Systems and Performance Project 5

Varied Weight

0

5

10

15

20

25

30

35

40

45

50

0 50 100 150 200 250 300 350 400 450

1g Equivalent Suit Weight (kg)

VO2 (

ml

-1·m

in-1

)

< 4.0

5.1 - 6.0

4.0 - 5.0

6.1 - 7.0

7.1 - 8.0

Speed (km·h-1)

0

1

2

3

4

5

6

7

0 50 100 150 200 250 300 3501-g Equivalent Suit Weight (kg)

Tota

l O2 -

l/ta

sk (B

usy

Boar

d &

Roc

k Tr

ansf

er)

0

20

40

60

80

100

120

140

VO2 -

ml/k

g ro

ck (S

hove

ling)Rock

Transfer

Busy Board

Shoveling

• Increased suit weight improves performance of exploration tasks

• Heavier suit weights have a greater effect on ambulation metabolic rate at speeds > 4.0 km/h and at grades ≥ 20%

0

5

10

15

20

25

30

35

40

45

0 50 100 150 200 250 300 350

1-g Equivalent Suit Weight

VO2 (

ml

-1·m

in-1

)

Level10% Grade15% Grade20% Grade30% Grade

Integrated Suit Test Review – EVA Physiology, Systems and Performance Project 6

Varied Pressure

0

1

2

3

4

5

6

7

8

0 5 10 15 20 25 30 35Suit Pressure (kPa)

Tota

l O2 -

l/ta

sk (B

usy

Boa

rd, R

ock

Tran

sfer

)

0

10

20

30

40

50

60

70

80

VO2 -

ml/k

g ro

ck (S

hove

ling)Shoveling

Busy Board

RockTransfer

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40 45 50

Pressure (kPa)

VO2 (

ml

-1·m

in-1

)

10% Grade

20% Grade

30% Grade

0

5

10

15

20

25

30

35

0 10 20 30 40 50Pressure (kPa)

VO2 (

ml

-1·m

in-1

)

< 4.0

5.1-6.04.0-5.0

6.1-7.0

7.1-8.0

Speed (km·h-1) • Pressurizing the suit does cause

an increase in metabolic rate when compared to an unpressurized suit

• Pressure differences from 1.0 to 6.5 psi made little impact on human performance for tasks tested

Integrated Suit Test Review – EVA Physiology, Systems and Performance Project 7

Terrain and Navigation• ↑ VO2 by 56% on average

(range 41-67%)• ↑ Distance by 7% (up to 21%)

Summary (n=3) HMP JSC ΔVO2

Avg VO2(mL·kg-1·min-1)

26.9 6.4

17.1 4.9

9.8 3.8

0

5

10

15

20

25

30

35

40

45

50

0 20 40 60 80 100 120

Time

VO2 (

ml/m

in/k

g)

JSCHMPDelta VO2

10.18 9.8410.30

9.79 9.57 9.81 9.91 9.89 9.89

0.690.42

1.24

0.520.27

2.06

0.35 0.37 0.48

0.00

2.00

4.00

6.00

8.00

10.00

12.00

1 2 3 1 2 3 1 2 3

Route and Subject

Stra

ight

Lin

e D

ista

nce

(km

)

Radial 17Radial 00 Radial 23

Integrated Suit Test Review – EVA Physiology, Systems and Performance Project 8

Predictive Models for Metabolic Rate• Inputs include subject anthropometry, suit parameters and EVA concepts• Optimize operational concepts for EVA suit

or• Optimize EVA suit for operational conceptsSubject Inputs EVA Ops Con EVA Percentages or EVA Time (hours)Body Mass (kg) 82 EVA Time (hrs/day) 6 SS Rest SS RestHeight (cm) 186 Total # EVA's 12 Suited Rest Suited RestLeg Length (cm) 105 # EVA Crew 2 Intrasite (1.5-3 kmh) 25% Intrasite (1.5-3 kmh) 0.83333333

Site to Site (4-5 kmh) Site to Site (4-5 kmh)Suit Inputs km/h Walkback (>6.5 kmh) Walkback (>6.5 kmh)Suit Type MKIII Level Average Speed 5.8 Pick Your Speed Pick Your SpeedSuit Weight (kgf) 121 10% Incline Speed 5.8 10% Incline 25% 10% Incline 1Suit Pressure (kPa) 29.6 20% Incline Speed 5.8 20% Incline 25% 20% Incline 0.33333333

30% Incline Speed 5.8 30% Incline 30% Incline 0.33333333 -10% Decline Speed 5.8 Decline Walking (-10%) Decline Walking (-10%) 1.2

Shoveling 25% Shoveling 0.66666667

Construction Tasks Construction Tasks 0.67

Percentages Hours Rock Transfer Rock Transfer 0.67

Average Metabolic Rate (ml/min/kg) 17.0 16.9 Total 100% Total 5.70666667

Total Oxygen per Person per EVA (L) 501.4 475.0

Total Oxygen Per Mission 12033.3 11399.8