2006-01-2239 

Phase II Testing of Liquid Cooling Garments Using a Sweating 

Manikin, Controlled by a Human Physiological Model 

John Rugh, Charlie King 

National Renewable Energy Laboratory 

Heather Paul, Luis Trevino, Grant Bue 

NASA Johnson Space Center 

Copyright © 2006 SAE International

ABSTRACT 

An ADvanced Automotive Manikin (ADAM) developed at 

the National Renewable Energy Laboratory (NREL) is 

used to evaluate NASA’s liquid cooling garments (LCGs) 

used in advanced spacesuits. The manikin has 120 

separate heated/sweating zones and is controlled by a 

finite-element physiological model of the human thermoregulatory system. Previous testing showed the thermal 

sensation and comfort followed expected trends as the 

LCG inlet fluid temperature was changed. The Phase II 

test data demonstrates the repeatability of ADAM by 

retesting the baseline LCG. Skin and core temperature 

predictions using ADAM in an LCG/arctic suit 

combination are compared to NASA physiological data to 

validate the manikin/model. An additional Orlan LCG 

configuration is assessed using the manikin and 

compared to the baseline LCG. 

INTRODUCTION 

NASA currently uses LCGs under spacesuits to remove 

heat from the human body. Thermally conditioned liquid 

is circulated through small tubes distributed around the 

suit. The tubes are secured to the garment in close 

proximity to the skin. The LCG is expected to remain the 

major heat acquisition element for removing heat from 

the crewmember, and improvements to the LCG are 

needed to reduce its weight by one-half for planetary 

missions, and to improve its performance. Performance 

measurements are to be conducted using the best 

combination of physiological simulations and human 

tests. Simulations include computer models and manikin 

thermal tests, and human testing includes laboratory 

evaluations with the LCG as well as integrated space 

suit-with-human evaluations to determine final comfort 

and physiological conditions for candidate LCG designs. 

NREL’s ADAM is used to assess the thermal 

performance of LCGs. The manikin's 120 individually 

controlled surface elements typically have a surface area 

of 120 cm2

. Each segment is a stand-alone device with 

integrated heating, temperature sensing, sweat 

distribution, heat flux gauge, and a local controller to 

manage the closed loop operation of the zone. The 

sweating surface is constructed entirely of metal, which 

is optimized for thermal uniformity and response speed. 

The skin temperature of each zone is determined by an 

array of thermistors, typically four, on each zone [1]. 

A unique aspect of ADAM is that it is controlled by a 

numerical physiological model. As temperatures are 

controlled and manipulated in ADAM's environment, the 

resulting skin heat transfer rates are reported to a 

physiological computer model. The model computes skin 

and internal temperature distribution and surface sweat 

rates. This information is sent back to the manikin, which 

maintains the prescribed skin temperatures, surface 

sweat rates, and breathing rates. The ongoing loop 

provides a continuously adjusting measurement tool to 

assess human thermal comfort in a transient 

environment. The skin temperature data are also 

delivered to a thermal comfort model, which predicts 

human perceptions of comfort. 

Validation tests showed the manikin under model control 

has a human-like skin temperature distribution with some 

deviations noted in the hands and feet [2]. The predicted 

overall thermal sensations and comforts match steadystate human data well, although transient measurements 

show nonhuman-like trends. The testing discussed in 

this paper is limited to steady-state tests. 

During the Phase I testing of NASA LCGs, a series of 

quick tests were conducted using ADAM to assess a 

Shuttle LCG [3]. Using the NASA comfort curve (Figure 

1) to determine the inlet flow temperature as a function of 

metabolic rate, three points on the curve were run [4]. 

ADAM controlled by the physiological model converged 

quickly at a lower metabolic rate of 200 W. At the higher 

metabolic rates (M=275 W and 350 W), we were not 

able to attain a steady-state core temperature because 

of limited test time. We also ran two tests with the inlet 

temperature over and under the suggested inlet 

temperature. Overall ADAM’s sensation and comfort 

response to LCG inlet temperature followed the expected 

1

NREL/CP-540-40036. Posted with permission. 

Presented at the 2006 International Conference on 

Environmental Systems, July 2006, Norfolk, Virginia 
trends, although results of off-curve test points showed 

less variation than expected. 

12

14

16

18

20

22

24

26

0 50 100 150 200 250 300 350 400 450 500

Metabolic Rate (W)

LCG Inlet Temperature (oC)

NASA Comfort Curve

NASA on-curve points

NASA off-curve points (M=275 W)

Figure 1. NASA comfort curve 

Based on the promising results of Phase I testing, a 

Phase II test program was initiated. Longer runs were 

conducted to enable reaching steady state. Additionally, 

an Orlan LCG was added to the test articles. NREL’s 

manikin environmental chamber was upgraded for 

Phase II to improve temperature and humidity control. 

PHASE II TEST OBJECTIVES 

1. Repeat the baseline Shuttle LCG tests from the 

Phase I tests to demonstrate repeatability (M=200 

W). 

2. Repeat the baseline Shuttle LCG tests from the 

Phase I tests to attain steady state (M=275 W and 

350 W). 

3. Test the Shuttle LCG with an arctic suit to minimize 

losses to the environment and better simulate the 

internal spacesuit environment. 

4. Gather data to validate the thermal manikin and 

model. Compare these data to physiological data 

generated from previous NASA testing. 

5. Test the Orlan LCG for performance comparison. 

PHASE II LCG TEST ARTICLES 

SHUTTLE LCG 

The Shuttle LCG is a conformal undergarment that 

covers the body from the neck to the wrists and ankles 

(Figure 2). Water flows through the LCG flexible tubing 

to remove excess metabolic heat from the crew member, 

and oxygen is vented from the helmet down to the hands 

and feet for further cooling. The flexible tubing consists 

of 48 separate tubes in contact with the body, with a total 

length of approximately 300 feet of one-eighth-inch outer 

diameter flexible tubes of ethylene vinyl acetate woven 

into the garment, to carry cooled water and promote heat 

removal. Additionally, oxygen entering at the helmet is 

ventilated over portions of the garment via four ducts that 

pull the vent stream to the extremities. After acquiring 

heat, the water and air are directed away from the 

garment. 

 

Figure 2. ADAM in the Shuttle LCG 

ARCTIC SUIT 

The arctic suit is a two-piece, down-filled outdoor 

garment manufactured by Marmot (Figure 3). The shell 

is nylon with Gore-Tex while the inner lining is nylon. 

The pants are a bib style and come up to ADAM’s 

abdomen. The arctic suit was placed over the Shuttle 

LCG to minimize losses to the environment and better 

simulate the internal space suit environment. 

Figure 3. ADAM dressed in the Shuttle LCG and arctic 

suit 

ORLAN LCG 

The Orlan LCG is the Russian-designed cooling garment 

that provides energy removal for the crew member 

during suited operations in order to maintain nominal 

energy storage (Figure 4). Similar to the Shuttle LCG, it 

is a conformal undergarment that covers the body from 

the neck to the wrists and ankles, however the flexible 

tubing extends only to the knee. The Orlan LCG 

includes a cap designed to be worn over the 

Communications Carrier Assembly that provides cooling 

for the head. Water flows through the flexible tubing to 

remove excess metabolic heat from the crew member. 

The Orlan LCG consists of 5 mm outer diameter PVC 

tubing woven through Knitted Capron elastic fabric with 

two connections: inlet and outlet, for the supplied cooling 

2
water. The total tubing length is about 65 m, and the 

mass with water is less than 3 kg. 

 

Figure 4. ADAM in the Orlan LCG 

ENVIRONMENT TEST CHAMBER 

Several improvements have been made to the 

environmental chamber since the Phase I testing. 

Measuring approximately 2.5 m by 2.5 m, the room has a 

dedicated heating, ventilation, and air-conditioning 

(HVAC) system installed to provide humidity, 

temperature control, and air recirculation. The control 

system maintains temperatures between 15°C and 38°C. 

Temperature input to the controller is obtained from a 

thermocouple suspended in the center of the room. The 

humidity can be controlled between approximately 20% 

and 100% depending on the room temperature set 

points. A portable dehumidifier is available when high 

humidity in the building makes achieving the lower 

humidity levels difficult. Humidity input to the controller is 

obtained from a capacitance style humidity sensor 

suspended in the center of the room. The HVAC system 

has a 250 cfm blower that circulates air within the room. 

Air is exhausted into the room along two sides of the 

ceiling directed down along the walls. The air return is at 

1 foot above the floor in one corner of the room. Typical 

airflow velocity in the middle of the room where the 

manikin is positioned is approximately 0.1m/sec. 

In practice, relative humidity can be controlled to ± 1%, 

and temperature surveys have shown less then 0.4°C 

variation from floor to ceiling in the center of the room. 

The air temperature is measured with type K 

thermocouples located at head, waist, and foot level. 

The wall, ceiling, and floor temperature are also 

measured. The thermocouples were calibrated using a 

Hart model 7103 Micro-Bath calibrator. 

In order to provide repeatable cooling for the LCG, a 

Neslab water chiller was installed. This unit can provide 

up to 2500 W of heat removal, and maintain ± 0.1°C 

temperature stability. Chilled water flows through the 

LCG and is measured by a Dwyer Model TF1053 flow 

sensor. Temperature into and out of the LCG is 

monitored by thermocouples in the fluid stream as close 

to the LCG as possible. A series of valves is used to 

throttle the output of the chiller pump to a flow of 1.81 

l/min through the suit. 

A data acquisition system—composed of a laptop 

computer and National Instruments hardware—collects 

room temperature, humidity, chilled water flow rate, and 

water inlet/outlet temperatures. 

TEST PROCEDURE 

First ADAM was dressed in polypropylene underwear 

with a long-sleeve top and bottom. This is the base layer 

typically used by NASA, and it also facilitated dressing 

ADAM in the LCG. When the LCGs were put on ADAM, 

a less than perfect fit was noted in some areas. A single 

Velcro strap around the chest was used to provide a 

snug fit between the Shuttle LCG to ADAM; two straps in 

the chest area were necessary on the Orlan LCG. 

Excess material in the crotch area of the Orlan LCG was 

bundled using cable ties. A sling under the arms 

supported ADAM in a standing position. Care was taken 

to not restrict flow in the tubing in the underarm/shoulder 

area. 

We performed two types of LCG tests with ADAM; model 

control and constant temperature control. 

MODEL CONTROL 

In model control, the physiological model controls the 

manikin, so it responds in a human-like manner. At the 

start of a run, the manikin is initialized with a constant 

temperature of 32oC and a sweat rate of 25.44 ml/hr/m2

. 

The chiller is set to the desired inlet temperature and 

flow is initiated to the LCG. The model is started using 

the heat loss from the previous run as the boundary 

condition. After 30 minutes, the manikin is linked to the 

model. The manikin receives the skin temperature and 

sweat flow-rate set points from the model, and sends 

real-time heat loss from each segment to the model. 

The test is determined to reach steady state when the 

core temperature stabilizes. 

The room temperature was set at 27oC, which yielded a 

spatially averaged air temperature of 26.6oC at ADAM. 

The room humidity was maintained at 25%. The room 

was typically conditioned overnight. 

TEMPERATURE CONTROL 

Constant temperature runs were performed to eliminate 

variability associated with model control and quantify 

differences in LCG performance. The manikin was set 

at a constant skin temperature of 35oC. Sweat flow rates 

of 0 and 200 ml/hr/m2

 were run. After ADAM’s heat loss 

attained steady state with no flow, flow to the LCG was 

initiated. The run was terminated when the heat loss 

with LCG flow reached steady state. 

3
For these runs, the room temperature was set at 23oC, 

which yielded an average air temperature of 22.4oC 

around ADAM. The room humidity was set at 50%. 

RESULTS 

REPEATABILITY TESTS 

To assess repeatability, we performed tests in the same 

environmental and control conditions as the 2005 test 

program. The manikin environmental chamber was set 

at 27oC, and the relative humidity was 25%. ADAM was 

dressed in the Shuttle LCG as shown in Figure 2. The 

physiological model was run with a metabolic rate of 200 

W while the inlet fluid temperature (Tinlet) to the LCG was 

22.4oC, and the flow was 1.81 l/min. After the Orlan LCG 

testing, ADAM was again dressed in the Shuttle LCG to 

obtain the additional data point on 5/8/06. Table 1 shows 

the core temperature was within 0.04oC on the test runs. 

The average skin temperature shows a larger variation of 

0.4oC with the outliner appearing to be the 3/14/06 data 

point. The primary reason for this difference is that the 

back skin temperature is 1.6oC warmer. This caused the 

back thermal sensation to be hot on 3/14/06 while it is 

neutral on 5/8/06. While the overall sensation in Table 1 

combines all parts of the body, the high weighting of the 

back sensation causes a greater impact on the overall 

sensation and overall comfort. 

Table 1. Shuttle LCG with M=200 W, Tinlet=22.4oC 

Core Temperature 

(

o

C)

Average Skin 

Temperature (oC)

Overall Thermal 

Sensation (+/-4)

Overall Thermal 

Comfort (+/-4)

2/15/05 36.71 32.56 0.35 1.63

3/14/06 36.75 32.97 0.79 0.98

5/8/06 36.75 32.68 0.39 1.45

Both sensation and comfort are evaluated on a scale of 

–4 to +4. For sensation, positive values indicate that one 

is feeling hot, and negative values indicate that one is 

feeling cold. For comfort, the scale rising from negative 

to positive indicates being very uncomfortable (-4) to very 

comfortable (+4). Table 2 defines the intermediate 

values. 

Table 2. Thermal sensation and comfort scales 

An investigation was conducted into why the back 

temperature was higher for the 3/14/06 test. The back 

temperature was compared to the chest temperature for 

all the runs. In the Shuttle LCG tests in March, the back 

temperature was warmer than the chest in all cases. In 

the 2005 and the 5/8/06 tests, the back was cooler than 

the chest. We noted gaps between the Shuttle LCG and 

ADAM’s upper-back region despite the strap used to 

bring the LCG in contact with ADAM as was done in 

2005. Although adjustments were made to the suit fit, it 

appears we did not have good contact in the upper-back 

region on 3/14/06. 

We also looked at test-to-test variation with ADAM 

dressed in the Orlan LCG. We ran the same room, 

fluid, and control conditions as above without changing 

the suit fit. The resulting core temperature was the same 

for both runs, and the average skin temperature was only 

different by 0.13oC (Table 3). The overall sensation was 

within 0.05, and the overall comfort was within 0.07. It 

appears there is good repeatability test-to-test with the 

hands and feet showing the largest deviations. We used 

core temperature to determine steady state. In the 

future, we need to monitor all skin temperatures because 

hand/foot temperatures appear to be changing when the 

core temperature is constant. 

Table 3. Orlan LCG with M=200 W, Tinlet=22.4oC 

Core Temperature 

(

o

C)

Average Skin 

Temperature (oC)

Overall Thermal 

Sensation (+/-4)

Overall Thermal 

Comfort (+/-4)

5/1/2006 36.64 32.74 0.41 1.18

5/2/2006 36.64 32.87 0.48 1.13

MODEL CONTROL 

In the 2005 test program, the limited test time prevented 

us from attaining steady-state conditions for the M=275 

W (Tinlet = 17.5, 21.3, and 24.3oC) and the M=350 W 

(Tinlet=19.4C) test points. With adequate time, we ran all 

five test points in Figure 1 to steady state with the Shuttle 

LCG (Figure 2) and the Orlan LCG (Figure 4). The arctic 

suit was not used for this series of tests; therefore, the 

exterior of both LCGs were exposed to the same room 

conditions. While the environment around the LCG for 

these tests is different than inside a spacesuit, the 

consistent room conditions allow for thermal 

performance comparison. There was no airflow supplied 

Numerical to the ventilation ducts in the Shuttle LCG. 

Value

Sensation 

Scale Comfort Scale

4 very hot very comfortable

3 hot

2 warm

1 slightly warm just comfortable

0 neutral

-1 slightly cool just uncomfortable

-2 cool

-3 cold

-4 very cold very uncomfortable

A flow rate of 1.81 l/min was used in all tests. It took 3-4 

hours to reach steady state for M=275 W and 7 hours for 

M=350 W. At the higher metabolic rates and inlet 

temperatures, the core temperature initially overshoots 

due to a lag in sweat evaporative cooling, which 

subsequently causes excessive sweating. This sweat 

(dionized water) flows into the segments, evaporates, 

and causes a resulting undershoot in core temperature. 

The Orlan LCG is equipped with a head covering fed by 

four tubes, which come up the center of the back. We 

did not use the head covering during this test program 

because the Shuttle LCG did not have a head covering. 

4
The authors recognize cooling the head would have a 

significant impact on thermal sensation, but it was 

beyond the scope of this test program. Localized cooling 

of the head also causes problems with the model. Since 

the core temperature is currently defined as the volume 

average of the brain, the model is too sensitive to 

localized head cooling. 

Figure 5 shows the core temperature for the Orlan LCG 

was an average of 0.06oC lower than the Shuttle LCG for 

all tests. Since the sweat rate is a function of core 

temperature in the model, the Orlan LCG also has lower 

sweat rates. The heat transfer to the LCG fluid in Figure 

6 was on average 15 W greater with the Orlan suit 

indicating the improved heat transfer compared to the 

Shuttle LCG. 

36.3

36.4

36.5

36.6

36.7

36.8

36.9

37

37.1

37.2

M=200 W,

T=22.3C

M=275 W,

T=21.3C

M=350 W,

T=19.4C

M=275 W,

T=24.3C

M=275 W,

T=17.5C

Tcore (oC)

Shuttle LCG

Orlan LCG

On NASA Comfort Curve Points Off NASA Comfort Curve Points

Figure 5. Core temperature for Shuttle and Orlan LCGs 

0

50

100

150

200

250

300

M=200 W,

T=22.3C

M=275 W,

T=21.3C

M=350 W,

T=19.4C

M=275 W,

T=24.3C

M=275 W,

T=17.5C

Heat Transfer to Liquid (W)

Shuttle LCG

Orlan LCG

On NASA Comfort Curve Points Off NASA Comfort Curve Points

Figure 6. Liquid heat transfer for Shuttle and Orlan LCGs 

The skin temperature results in Figure 7 are not as 

consistent. Since the Shuttle LCG did not have good 

contact in the upper back area, the average skin 

temperature for both garments was calculated without 

including the back. While the Orlan LCG resulted in a 

lower average skin temperature in two cases, a higher 

average skin temperature resulted during the lowest fluid 

inlet temperature cases. This is because the Orlan LCG 

does not have cooling tubes in the calf region. The 

Shuttle LCG has tubes and subsequently lower calf 

temperatures. This also lowers the foot temperatures 

due to cooler blood flow and results in a lower overall 

average skin temperature. The dashed lower curves in 

Figure 8 present the average skin temperature without 

the back for three inlet temperature cases at M=275 W 

(same data as Figure 7). At Tinlet=17.5oC, the Orlan LCG 

has a higher average skin temperature. Taking the 

calves and feet out of the average (solid lines), the Orlan 

LCG has significantly lower skin temperatures for the 

M=275 W cases as well as the M=350 W and M=200 W 

cases. 

32.0

32.5

33.0

33.5

34.0

34.5

M=200 W,

T=22.3C

M=275 W,

T=21.3C

M=350 W,

T=19.4C

M=275 W,

T=24.3C

M=275 W,

T=17.5C

Average Tskin without back (oC)

Shuttle LCG

Orlan LCG

On NASA Comfort Curve Points Off NASA Comfort Curve Points

Figure 7. Average skin temperature without the back for 

Shuttle and Orlan LCGs 

Tskin, 2006 NASA LCG, off-curve test points

32.5

33.0

33.5

34.0

34.5

M=275 W, T=17.5C M=275 W, T=21.3C M=275 W, T=24.3C

Average Tskin (oC)

Shuttle LCG

Orlan LCG

S i 3 Average without back, calf, and feet

Average without back

Shuttle LCG

Shuttle LCG

Orlan LCG

Orlan LCG

Figure 8. Skin temperatures for M=275 W cases 

In the Tinlet=17.5oC case, the calf temperature in the 

Orlan LCG was actually warmer than the Tinlet=24.3 case. 

This is due to the higher sweating in the Tinlet=24.3oC 

case cooling the calf due to the evaporation. In the 

Tinlet=17.5oC case, the basal sweat rate didn’t 

significantly cool the calf and resulted in a higher skin 

temperature. 

The overall thermal sensation is plotted in Figure 9. As 

the fluid inlet temperature is increased, the thermal 

sensations become increasing warm as expected, 

although the slope is not very steep. The Orlan LCG 

resulted in cooler (less warm) thermal sensation. In all 

three cases, the Orlan LCG calf and foot local thermal 

sensations were warmer than the Shuttle LCG, but the 

5
sensation correlations weights more influential parts of 

the body higher. 

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

M=275 W, T=17.5C M=275 W, T=21.3C M=275 W, T=24.3C

Overall Sensation

Shuttle LCG

Orlan LCG

slightly warm

slightly cool

Figure 9. Overall thermal sensation for M=275 W cases 

We used an unweighted average of the local comforts to 

calculate the overall thermal comfort (Figure 10). At 

warmer inlet temperatures, the Orlan LCG had better 

comfort. At 17.5oC inlet temperature, the Orlan LCG had 

reduced comfort. This was due to local discomfort at the 

calf and foot of the Orlan LCG. The local sensation is 

warmer due to the skin temperature difference between 

the calf and rest of the body, and this causes local 

discomfort. 

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

M=275 W, T=17.5C M=275 W, T=21.3C M=275 W, T=24.3C

Overall Comfort

Shuttle LCG

Orlan LCG

just comfortable

just uncomfortable

Figure 10. Overall thermal sensation for M=275 W cases 

The Orlan LCG has better thermal performance than the 

Shuttle LCG using the following parameters: core 

temperature, heat transfer to the liquid, and average skin 

temperature (without back, calves, and feet). These tests 

were performed with the less than optimum Shuttle LCG 

contact in the upper back region of ADAM. Based on 

the multiple tests at M=200 W, the Shuttle LCG thermal 

sensation and comfort results would be better than 

presented in Figures 9 and 10, but the magnitude is 

unknown at this time. 

ARCTIC SUIT 

The Shuttle LCG was tested underneath the arctic suit 

(Figure 3) to reduce the impact of the room conditions 

and enable comparison to NASA data where subjects 

were tested with the arctic suit /Shuttle LCG combination. 

The room conditions were set to 27oC and 25% relative 

humidity to be consistent with the Shuttle and Orlan LCG 

tests. Since the room was at 26.6oC and the fluid inlet 

temperature was 22.3oC, the arctic suit should have 

reduced the heat gain from the room air or at least had 

negligible impact. This did not happen. We ran five 

model control cases: one at M=200 W, three at M=300 

W, and one at M=350 W. At the higher metabolic rates, 

the initial transient caused excessive sweat that soaked 

the arctic suit. This liquid remained in the arctic suit and 

caused the heat transfer to the liquid to be approximately 

30% higher than with no arctic suit. The excessive liquid 

surrounding ADAM caused four segments to fail. It was 

decided not to test the Orlan LCG under the arctic suit 

because of the increased heat transfer to the liquid and 

to reduce the chances of additional damage to ADAM. 

We were able to gather meaningful data from the arctic 

suit tests despite the problems encountered. In the 

M=200 W case, ADAM did not over-sweat initially and 

had: 

• Reasonably dry skin 

• About the same fluid side heat transfer as the LCG 

only test 

• Core and skin temperatures slightly warmer due to 

insulation of the segments not covered by the tubes. 

These skin temperature data were compared to 

physiological data measured by NASA [5]. In that test 

program, human subjects were dressed in the base 

layers, Shuttle LCG, and arctic suit. Skin temperatures 

were measured over various parts of the body, and the 

heart rate was recorded. The subjects exercised on a 

treadmill. A wide range of inlet temperatures and 

metabolic rates were tested. Two of the subjects had 

metabolic rates and inlet fluid temperatures close to our 

test conditions (M=200 W and 22.4oC) that enabled 

comparison. At this metabolic rate, the test report 

indicates the arm push bars were not used while the 

subject walked on the treadmill. 

Figure 11 shows the arm and torso temperatures 

predicted by ADAM are similar to the NASA subjects. A 

single point on the forearm defines the right arm location 

while the torso is an average of the chest and back. The 

right leg is an average of the calf and thigh. The leg 

temperatures predicted by ADAM were approximately 

4oC warmer than the NASA subjects. This may be due 

to the pumping action of the clothing during the leg 

motion of the subjects on the treadmill, which cooled the 

leg. Variations in temperature measurement location 

also add uncertainty. 

6
26

27

28

29

30

31

32

33

34

35

Right Arm Right Leg Torso

Skin Temperature (oC)

NASA Subject 1

NASA Subject 2

ADAM

Figure 11. Comparison to NASA subject data 

A limitation of this comparison is that the room conditions 

of the NASA test were not known. It is assumed the 

arctic suit isolated the subjects from the room 

environment and reduced its impact. 

CONSTANT TEMPERATURE TESTS 

In order to eliminate variables associated with the model, 

we also conducted tests at a constant skin temperature 

of 35oC with and without sweat. The liquid side heat 

gain is calculated by 

Qliquid = c

.

m p (Toutlet – Tinlet) (1) 

The heat loss from ADAM is calculated by summing the 

heat loss from all 120 segments. 

QADAM = ∑ Q

=

120

1n

n” An (2) 

By calculating the heat loss from ADAM without LCG 

flow and with LCG flow, the difference is the heat loss 

due to the flow as measured by ADAM. 

ΔQADAM = QADAM, LCG flow – QADAM, no LCG flow (3) 

The columns on the right side of Figure 12 show the 

increase in heat loss measured by ADAM due to the 

evaporation of the sweat. The ΔQADAM parameter was 

calculated for the no sweat case and sweat case. The 

difference between these two cases shows that sweat 

increased the heat loss by 46 W when flow was supplied 

to the LCG. There was a similar 34 W increase in Qliquid

due to the presence of sweat. This increase in heat 

transfer is due to increased thermal conductivity of the 

liquid between the Tskin / tubing in the LCG and 

condensation of the sweat vapor on the tubes. 

0

50

100

150

200

250

300

350

400

Qliquid Delta Q ADAM Q ADAM, No LCG Flow Q ADAM, LCG Flow

Heat Transfer (W)

No Sweat

Sweat

Liquid Side 

Measurement

ADAM 

Measurement

46

34

60.8

142.2

Qliquid ΔQADAM QADAM, no LCG flow QADAM, LCG flow

Figure 12. Shuttle LCG and ADAM heat transfer for no 

sweat and sweat conditions 

One concern is the difference between Qliquid and 

ΔQADAM. For the no sweat case, the ΔQADAM = 60.8 W 

while the Qliquid = 142.2 W. The following reasons are 

considered: 

• Condensation on the tubes increase Qliquid (not likely, 

test at low humidity showed negligible change in heat 

transfer) 

• Qliquid larger due to heat transfer from the room [not 

likely since the typical average LCG fluid 

temperature (23.1oC) is greater than the air 

temperature (22.5oC)] 

• Uncertainty in Qliquid calculation (estimated to be +/- 

18 W) 

• Uncertainty in QADAM calculation (possible, but core 

temperatures and skin temperatures look okay) 

• Heat transfer from ADAM’s interior to the liquid 

(possible, there is internal heating in ADAM and we 

measured a 71 W difference between the power 

supplying ADAM and the measured heat loss from 

the segments). 

This issue is not resolved at this time, but comparisons 

between the Shuttle and Orlan LCGs continue. The 

Shuttle LCG tests were conducted with good contact in 

the upper back region. Figure 13 shows a comparison of 

the Shuttle and Orlan LCGs with no sweat. The Orlan 

LCG had a higher heat loss with no flow suggesting a 

lower baseline thermal resistance of the Orlan suit. This 

makes sense since the Shuttle LCG has two layers of 

material and is expected to have higher thermal 

resistance. The fluid side heat transfer is 4 W higher for 

the Orlan LCG suggesting better heat transfer, although 

the magnitude is not significant. This slightly better 

performance is consistent with the model control tests. 

7
0

50

100

150

200

250

Qliquid Delta Q ADAM Q ADAM, No LCG Flow Q ADAM, LCG Flow

Heat Transfer (W)

NASA LCG

Orlan LCG

Liquid Side 

Measurement

ADAM 

Measurement

Qliquid ΔQADAM QADAM, no LCG flow QADAM, LCG flow

Figure 13. Comparison of NASA and Orlan LCGs with 

no sweat 

CONCLUSION 

ADAM was successfully used to assess the thermal 

performance of a Shuttle and Orlan LCG. Using a 

manikin controlled by a physiological mode enabled us to 

assess differences in local skin temperatures, thermal 

sensations, and thermal comforts. 

Repeating a test that was run in 2005 demonstrated the 

importance of verifying a good fit of the LCG on ADAM 

prior to testing. Some of the Shuttle LCG model control 

tests were run with a less than perfect fit, which made 

comparison to the Orlan LCG challenging. Variation in 

test-to-test results was low. Differences were attributed 

to not attaining steady-state skin temperatures in all 

regions. 

Constant skin temperature tests showed that sweat 

impacts the performance of LCGs through increased 

thermal conductivity due to moisture between the skin 

and tubes, and the condensation on the tubes. A 

comparison of skin temperatures from a model control 

run with NASA subject data showed reasonably good 

correlation. ADAM may have overestimated the leg 

temperature because he was not walking like the 

subjects in Reference 5. 

Comparing results with the same manikin and room 

conditions, the Orlan LCG had slightly better heat 

transfer, which resulted in lower core and skin 

temperatures. The less than perfect fit on the upper 

back of the Shuttle LCG prevented a good comparison of 

thermal sensation and comfort. 

RECOMMENDATIONS 

The physiological model should be improved to better 

simulate hand/foot temperatures. The impact of the 

definition of core temperature needs to be further 

investigated. If the core temperature were less sensitive 

to the brain temperature, additional testing could be 

performed to assess the impact of the head portion of 

the Orlan LCG. Using an average temperature instead 

of an individual segment temperature to provide input to 

the thermal comfort model correlations would reduce the 

impact a single segment has on thermal sensation and 

comfort. 

Further tests can be conducted under a spacesuit 

although venting would be required to avoid the moisture 

retention problem identified in the arctic suit testing. 

ADAM can help design the next generation NASA LCG 

by assessing the thermal performance of potential 

configurations and even assisting in a physiological 

based LCG design. 

ACKNOWLEDGMENTS 

The authors gratefully acknowledge the support of the 

U.S. Department of Energy (DOE) in developing, 

fabricating, and testing the thermal manikin and 

physiological model. DOE’s Office of FreedomCAR and 

Vehicle Technologies (OFCVT) supported this work. The 

authors appreciate the support of Lee Slezak, DOE 

Program Manager; Terry Penney, NREL’s OFCVT 

Technology Manager; and Barbara Goodman, Director of 

the NREL Center for Transportation Technologies and 

Systems. 

REFERENCES 

1. Rugh, J.; Farrington R.; Bharathan, D.; Vlahinos, A.; 

Burke, R.; Huizenga, C.; and Zhang, H. (2004) 

Predicting Human Thermal Comfort in a Transient 

Nonuniform Thermal Environment, European Journal 

of Applied Physiology, (Vol. 92, Number 6) pp. 721-

727. 

2. Rugh, J.; and Bharathan, D. (2005) “Predicting 

Human Thermal Comfort in Automobiles,” 

Proceedings of the 7th Vehicle Thermal 

Management Systems Conference, Paper # 2005-

01-2008, May 10-12, 2005, Toronto, Canada, 

Society of Automotive Engineers. 

3. Farrington, R.; Rugh, J.; Bharathan, D.; Paul, H.; 

Bue, G.; and Trevino, L. (2005) “Using a Sweating 

Manikin, Controlled by a Human Physiological 

Model, to Evaluate Liquid Cooling Garments,” 

Proceedings of the 35th International Conference on 

Environmental Systems, Paper # 2005-01-2971, July 

11-14, 2005, Rome, Italy, Society of Automotive 

Engineers. 

4. Dunaway, B. (1988) Automatic Liquid and Ventilation 

Cooling Garment Control Algorithm Final Test 

Report, NASA Document SSS87-221 (CTSD-SS176). 

5. Smith, G., and Pantermuehl, J. (1992) Segmented 

Liquid Cooled Garment Final Test Report, NASA 

Document JSC-25720 (CTSD-ADV-032). 

CONTACT 

Grant Bue, M.S.M.E., leads the Extravehicular Activity 

(EVA) worksite thermal analysis for the International 

Space Station at the NASA Johnson Space Center. He 

was involved in the design and testing of liquid cooling 

8
systems for the Shuttle Launch/Entry Suit. He is coauthor of the computer program ASDA: Advanced Suit 

Design Analyzer. He can be reached at 

grant.c.bue@nasa.gov. 

Charles King is an engineer at NREL. He ran the tests 

and is responsible for maintaining ADAM and the 

manikin environmental chamber. He can be reached at 

charles_king@nrel.gov. 

Heather Paul is a part of the Advanced EVA Team at the 

NASA Johnson Space Center. She is the Ventilation 

Subsystem manager for the development of the next 

generation Portable Life Support Systems that will be 

used with the Lunar and Martian spacesuits. She also 

works with the Thermal Subsystem on evaluating cooling 

garment concepts. She can be reached at 

heather.l.paul@nasa.gov. 

John Rugh, M.S.M.E., leads the Vehicle Ancillary Loads 

Reduction task at NREL. The objective of the project is 

to reduce fuel used for vehicle ancillary loads by 

reducing thermal loads, improving delivery efficiency, 

and increasing equipment efficiency including using 

engine waste heat to provide cabin cooling. He can be 

reached at john_rugh@nrel.gov. 

Luis Trevino is a part of the Advanced EVA Team at the 

NASA Johnson Space Center. He is the Thermal 

Subsystem manager for the development of the next 

generation Portable Life Support Systems that will be 

used with the Lunar and Martian spacesuits. He can be 

reached at luis.trevino-1@nasa.gov. 

DEFINITIONS, ACRONYMS, ABBREVIATIONS 

An ADAM segment area 

ADAM ADvanced Automotive Manikin 

cp Specific heat of LCG fluid 

DOE U.S. Department of Energy 

EVA Extravehicular Activity 

HVAC Heating, ventilation, and air-conditioning 

LCG Liquid cooling garment 

M Metabolic rate 

.

m LCG liquid mass flow 

NREL National Renewable Energy Laboratory 

OFCVT Office of FreedomCAR and Vehicle 

Technologies 

Qn” ADAM segment heat transfer 

QADAM Sum of the heat transfer from ADAM’s 

120 segments 

ΔQADAM Difference in QADAM without LCG flow 

and with LCG flow 

Qliquid LCG liquid heat gain 

Tinlet LCG inlet fluid temperature 

Toutlet LCG outlet fluid temperature 

9