Patricia Loyselle

Glenn Research Center, Cleveland, Ohio

Kevin Prokopius

Analex Corporation, Brook Park, Ohio

Proton Exchange Membrane Fuel Cell

Engineering Model Powerplant

Test Report: Benchmark Tests in Three Spatial Orientations

NASA/TM—2011-216224

April 2011
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Patricia Loyselle

Glenn Research Center, Cleveland, Ohio

Kevin Prokopius

Analex Corporation, Brook Park, Ohio

Proton Exchange Membrane Fuel Cell

Engineering Model Powerplant

Test Report: Benchmark Tests in Three Spatial Orientations

NASA/TM—2011-216224

April 2011

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
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NASA/TM—2011-216224 1 

Proton Exchange Membrane Fuel Cell 

Engineering Model Powerplant

Test Report: Benchmark Tests in Three Spatial Orientations

Patricia Loyselle 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Kevin Prokopius 

Analex Corporation 

Brook Park, Ohio 44142 

Summary

Proton exchange membrane (PEM) fuel cell technology is the leading candidate to replace the aging 

alkaline fuel cell technology, currently used on the Shuttle, for future space missions. This test effort 

marks the final phase of a 5-yr development program that began under the Second Generation Reusable 

Launch Vehicle (RLV) Program, transitioned into the Next Generation Launch Technologies (NGLT) 

Program, and continued under Constellation Systems in the Exploration Technology Development 

Program. Initially, the engineering model (EM) powerplant was evaluated with respect to its performance 

as compared to acceptance tests carried out at the manufacturer. This was to determine the sensitivity of 

the powerplant performance to changes in test environment. In addition, a series of tests were performed 

with the powerplant in the original standard orientation. This report details the continuing EM benchmark 

test results in three spatial orientations as well as extended duration testing in the mission profile test. The 

results from these tests verify the applicability of PEM fuel cells for future NASA missions. The specifics 

of these different tests are described in the following sections. 

Proton Exchange Membrane (PEM) Fuel Cell Engineering Model (EM) 

Powerplant Description 

The Teledyne PEM Fuel Cell EM Powerplant consists of a water-cooled, hydrogen and oxygen PEM 

fuel cell stack along with supporting ancillaries and a separate control and data acquisition system 

(Fig. 1). 

The fuel cell stack comprises 117 individual cells divided into 3 subsections. Each subsection 

comprises 39 cells in a series configuration. The three subsections are connected in a parallel 

configuration. The fuel cell stack was designed to deliver between 2 and 12 kW of power within a voltage 

regulation range of 33 to 27 volts of direct current (VDC). The fuel cell product water is removed from 

the stack using recirculation pumps and gravity-independent water separators and is rejected outside of 

the powerplant. All powerplant ancillary components are powered external to the fuel cell powerplant. 

Waste heat is removed from the stack via an internal cooling loop. The powerplant cooling system, in 

turn, rejects the heat to a facility cooling system external to the powerplant. Additional powerplant design 

goals are outlined in Table I. 
NASA/TM—2011-216224 2 

TABLE I.—POWERPLANT DESIGN GOALS 

Engineering model design goals Verification method 

Produce 2 to 12 kW of electrical power within a voltage 

range of 33 to 27 VDC 

All tests 

Gravity and orientation independent operation Operation under three physical orientations 

Maintenance-free operation for 3000 hr All tests 

90 percent of the final change in voltage after a change in 

load shall occur within 0.2 s 

Performance load profile calibration series 

Shall be capable of automatic startup to 3 kW in less than 5 s 

if reactants are present, initial stack temperature is greater 

than 40 °F, and no inerts are present 

50 percent of capability test 

Shall be capable of shutdown in less than 1 min All tests 

Shall be capable of operating on propellant-grade (MIL PRF–

27201C) and higher purity hydrogen and propellant-grade 

(MIL PRF–25508F) and higher purity oxygen 

All tests 

Operating life shall be greater than 3000 hr All tests 

Shall be capable of operation for 9 min at 7 kW without 

cooling from a secondary coolant loop 

Loss of coolant test 

Shall be capable of a minimum 250 stop/start cycles All tests 
NASA/TM—2011-216224 3 

Test Summaries 

The stability, performance, life, gravity independence, and response time of the Teledyne EM 

Powerplant were evaluated using a series of tests under three physical orientations. These performance 

tests were conducted upon the Teledyne EM Powerplant to assess performance and stability over 

conditions anticipated to be encountered during operation under mission scenarios. Initial evaluation tests 

were conducted under the standard A orientation, as seen in Figure 1, to form a baseline performance 

metric. A brief description of each test type follows. Detailed information regarding operating parameters 

of each test is included in the appendix. 

Calibration Series Test 

The calibration series test is a reference test for the EM. The series is composed of a polarization test 

and an abbreviated version of the performance load profile test. This test was performed at specified 

intervals during the evaluation of the EM at Teledyne, NASA Glenn Research Center (NASA Glenn), and 

NASA Johnson Space Center. The calibration series test quantifies performance changes of the EM 

caused by shipping, orientation effects, and damage as a result of testing and age. Voltage transitions are 

recorded at a rate of 200 kHz during the transition from 51 to 357 A, and again at the transition from 

357 to 51 A. 

Performance Load Profile Test 

The performance load profile test is a benchmark test for the EM. This test evaluates the performance 

of the EM under different operational conditions, such as orientation and vibration. The performance load 

profile test was carried out at Teledyne and NASA Glenn. Voltage transitions were recorded at a rate of 

200 kHz during the transition from 51 to 357 A, and again at the transition from 357 to 51 A. 

Fifty Percent of Capability Test 

The 50 percent of capability test evaluates the response speed of the EM to loads after a rapid startup. 

The rapid startup procedure is used to start the EM. This procedure includes purging the unit of nitrogen 

and the introduction of reactants but does not include a warmup of the powerplant. The powerplant 

ancillaries and heaters use a power source external to the powerplant. Under normal startup conditions, 

the powerplant ancillaries are started and then the plant is prewarmed to 45 °C prior to applying a power 

load. During this test, the ancillaries are started but no prewarming takes place. To meet the requirements 

of this test, within 5 s of the start, the powerplant must be able to respond to a load approximately 

50 percent of the rated power. After completion of this test, the powerplant is shut down, and the normal 

startup procedure is used to bring the powerplant online for the remainder of the day’s testing. 

Mission Profile Test 

The mission profile test measures the performance of the EM powerplant over a power profile and 

duration representative of a typical Shuttle mission. The test is run uninterrupted for the entire 240 hr. 

Loss of Coolant Test 

The loss of coolant test evaluates the performance of the EM powerplant when the cooling system 

external to the powerplant is interrupted. 
NASA/TM—2011-216224 4 

Constant Load Test 

During the initial mission profile test, a slow degradation of the fuel cell stack voltage was observed. 

The constant load tests were performed to evaluate the fuel cell stack voltage changes over time. The tests 

also were performed using ultrapure hydrogen and oxygen gas to help explain the voltage degradation 

observed while performing the Mission Profile under the same load condition with the gas supply coming 

from the hydrogen and oxygen tube trailers. 

Orientation Effects 

Description 

A fuel cell powerplant designed for space applications must not rely upon gravitational effects to 

facilitate movement or removal of reactants or products. The EM was designed with this requirement in 

mind. To evaluate the effectiveness of the gravity-independent design, the EM was tested in three 

different physical orientations as part of the initial performance evaluation at NASA Glenn. Figures 2 

through 4 show the powerplant in the A, B, and C orientations, respectively. A series of tests were 

performed in each of these orientations. These tests include the calibration series, the performance load 

profile, the 50 percent capability test, and the mission profile test. 
NASA/TM—2011-216224 5 
NASA/TM—2011-216224 6 
NASA/TM—2011-216224 7 

Test Results 

Calibration Series 

The calibration series test was conducted upon the EM powerplant in each of the three orientations. 

After each orientation, the powerplant was returned to orientation A, and the calibration series was 

performed. This was performed to monitor any performance changes in the powerplant and to identify the 

cause of any variations such as age, operational conditions, or damage as a result of operation in one of 

the orientations. 

The stack voltage performance curves obtained during the calibration series for the three different 

orientations are shown in Figure 5. Only minor variations in the voltage performance were observed in 

the three physical orientations. The sawtooth pattern evident in the data was the result of intermittent 

venting of impurities built up in the powerplant system. The powerplant was designed to operate 

“deadheaded” the majority of time. As the reactants were consumed, the impurity concentration increased 

in the system. These impurities acted as a diluent to the reactants. As the impurity concentration in the 

system increased, the system performance reversibly degraded until the impurities were vented from the 

powerplant system. The powerplant impurity vent timing could be adjusted to reflect the purity of the 

incoming reactants. The lower the purity of the incoming reactant gases, the more frequently venting was 

required. One of the design goals of the powerplant was operation under propellant-grade reactants. This 

design goal enables the powerplant to share reactants from the propellant system rather than carrying 

reactants and tanks dedicated to the power subsystem. By eliminating the need for separate reactant tanks, 

this feature will result in significant mass savings. 

Figure 5 shows that the largest variation between the three orientations occurred within the first 

45 min of the test, that is, during the iV curve. After this period, the performance variation between 

orientations diminished greatly. 
NASA/TM—2011-216224 8 

To change the orientation of the powerplant, the powerplant was first taken through its shutdown 

sequence and allowed to cool prior to reorientation. During this time, small amounts of product water that 

had not been removed during the shutdown and purge sequence could condense within the fuel cell stack 

or the balance of plant components. Since the powerplant is predominantly a closed-loop system, until the 

water is separated out of the reactant stream, it could cause some temporary performance degradation. 

The reactant recirculation pumps act to recirculate unused reactants back into the fuel cell stack after 

the product water has been removed. The power required to operate the reactant recirculation pumps is 

dependent upon the overall density of the gas or liquid being pumped. A higher density fluid, resulting 

from more humid gases or small slugs of water will require more power for pump operation. In Figure 6, 

the hydrogen recirculation pump current is plotted with the voltage curves for the three orientations. The 

pump currents observed during the three orientations are substantially different during the first 45 min of 

the calibration series test, indicating varying levels of liquid product water or humidification between the 

tests. 

Other conditions that can have a significant effect upon powerplant performance are the temperature 

of the reactants entering the powerplant. The reactants used during the evaluation of the EM powerplant 

were stored outside. As the outside temperature varied, so too did the temperature of the stored reactants. 

As is evident from Figures 7 and 8, the incoming hydrogen and oxygen gas temperatures varied greatly 

during the first 45 min of the calibration series test. The combination of initial variations in inlet reactant 

temperatures with the higher humidity or presence of liquid product water accounts for the variation in 

powerplant performance observed during the first 45 min of the test. Figure 5 shows that after this initial 

period of adjustment, the performance curves in each of the three orientations overlapped. No significant 

effect was observed in the performance of the EM powerplant as a function of physical orientation. 
NASA/TM—2011-216224 9 
NASA/TM—2011-216224 10 

After each series of performance tests in each orientation, the powerplant was reoriented back into 

orientation A. The calibration series was then performed upon the powerplant in orientation A. The 

reason for this was two-fold. If any performance changes were observed in any of the orientations, the 

preceding and following orientation A calibration series test would act as a standard. If the powerplant 

operational performance changed in a specific orientation, the following orientation A calibration series 

test results would show if the change was truly a function of orientation or because of damage or 

performance changes to the powerplant over time. 

Figure 9 shows the orientation A calibration series test conducted after each of the orientation test 

series. As was observed in the three orientations, the first 45 min shows some variations between the three 

tests. After the initial 45 min, the performance curves of the three orientation A’s overlapped for the 

remainder of the test. 

In the tests in the three orientations, the reactant recirculation pump operating current exhibited 

variability during that initial timeline. The variation in the oxygen recirculation pump current can be 

observed in Figure 10. The pump current in the A-after-B test was higher than that observed for the other 

two tests. This is likely due to liquid water being recirculated and moved out of the powerplant. After the 

initial 45 min, the excess water is removed, and the pump current dovetails and matches the pump 

currents observed during the other tests. At the same time, the performance (voltage) in the A-after-B test 

converges with the other two tests. Again, the performance differences observed were not due to damage 

as a result of operation in other orientations or age-related performance changes, but rather temporary, 

reversible differences in the starting conditions of the powerplant. 
NASA/TM—2011-216224 11 

Performance Load Profile Test 

The performance load profile test is used as a standard test of powerplant performance over an 

uninterrupted 8-hr period. During the test, power levels and durations are varied. In addition, the transient 

response to a change in load was also evaluated during the transition from 51 to 357 A, and again at the 

transition from 357 to 51 A. The performance load profile results for all three orientations are shown in 

Figure 11. The performance voltage curves overlap for all three orientations, with very little variation 

between the three curves. 

Transient Response of the Powerplant to Changes in Load 

During the course of the performance load profile tests, the response of the powerplant to changes in 

load was monitored at two points during the test: (1) from an applied load of 51 to 357 A (see Fig. 12) 

and (2) from 357 to 51 A (see Fig. 13). The transient response of the powerplant was evaluated in all three 

orientations. A high-speed data acquisition system operating at 200 kHz monitored the applied load 

current and the stack voltage during these transitions. 

During the transition from 51 to 357 A, the powerplant performed the same in all three of the physical 

orientations. No change in performance was observed as a function of physical orientation (see Fig. 12). 

In the transition from 51 to 357 A, the electronic load initially overshot the requested current, but 

stabilized quickly. The fuel cell stack voltage followed the load current but also overshot and followed a 

ringing pattern until it stabilized in less than 2 ms. The cause of the fuel cell stack voltage overshoot and 

ringing pattern is unknown. It could be due to pressure swings within the fuel cell stack caused by 

changes in reactant consumption, changes in flow rates or due to some type of electrical interference in 

the signal, although this was not observed in the current signal. Currently the cause is unknown, but the 
NASA/TM—2011-216224 12 
NASA/TM—2011-216224 13 

phenomenon lasted less than 2 ms. The stack voltage continued to decrease after the ringing pattern 

subsided. The reactant flow rates did not change when the power load was changed from 51 to 357 A. 

However, the reactant consumption rate did change. Therefore, the stoichiometry of the reactant delivery 

to the fuel cell stack changed. At 51 A, the calculated hydrogen and oxygen stoichiometry was 14.8 and 

28.5, respectively. At 357 A, the calculated hydrogen and oxygen stoichiometry was 3 and 5, 

respectively. At the higher power load (higher current), the reactant flow rate through the fuel cell stack 

was reduced relative to the lower power load (lower current). Product water was removed from the stack 

via reactant flow rates higher than required by the power demand. Therefore, when the power demand 

increased and the reactant flow rates did not, product water was not removed from the stack as well. The 

slight reduction in stack voltage over a few milliseconds was likely the result of a change in the product 

water remaining in the stack; a slight increase in resident product water will result in a slight decrease in 

the stack voltage. 

As can be seen in Figure 12, after approximately 8 ms, the stack voltage reached 27.4 V. The final 

voltage observed after this transition was 29.1 V. Therefore, the powerplant reached greater than 

90 percent of the final voltage within 8 ms. The powerplant met the design requirement that the 

90 percent of the final change in voltage after a change in load should occur within 2 s. 

During the transition from 357 to 51 A, the powerplant again responded and stabilized rapidly 

(see Fig. 13). Again no difference in the transient response of the powerplant was observed for the three 

physical orientations. During the transition to a lower power draw (51 A), the stack voltage continued to 

increase slightly before stabilizing and as discussed before, the reactant stoichiometry again changed, this 

time going to a higher level. As a result, more product water was being removed from the stack, which 

resulted in a slightly higher stack voltage. 

As can be seen in Figure 13, after approximately 8 ms, the stack voltage was 32.6 V. The final 

voltage observed after this transition was 33.7 V. Therefore, the powerplant reached greater than 

90 percent of the final voltage within 8 ms. Again, the powerplant met the design requirement that 

90 percent of the final change in voltage after a change in load should occur within 2 s. 
NASA/TM—2011-216224 14 

Fifty Percent of Capability Test 

The 50 percent of capability test demonstrated the ability of the powerplant to deliver 50 percent of 

rated capacity within 5 s after the start of the powerplant. Under normal startup conditions, the powerplant is 

preheated to a set temperature prior to the imposition of a power load. During rapid startup, the inerts (i.e., 

nitrogen) were purged from the powerplant system prior to start; however, no prewarming of the fuel cell 

stack or powerplant occurred. When the powerplant was started under this method, the ancillary system, i.e., 

the reactant recirculation pumps and water separators were started and the reactant supply solenoid valves 

were opened. The powerplant system was designed to bring the ancillary system online and to be ready to 

provide power within 5 s of start. As can be seen in Figure 14, a load equivalent to 50 percent of its 

capability was applied to the powerplant 5 s after start. The average power and average voltage plotted 

represent the levels seen during normal operation at the same power level. Upon application of the load, the 

powerplant voltage and power quickly rose to levels seen during normal startup and operation. 

Initial rapid startup or 50 percent of capability tests were performed in orientation A. The EM was 

then reoriented into the orientation B and then the orientation C. Figure 14 provides the stack voltage and 

applied current observed for the tests performed in all three orientations. 

There were variations in stack voltages observed between the three orientations. This correlates to a 

similar variation in the hydrogen recirculation pump currents required (see Fig. 15). As described 

previously, as the density of the gas or fluid increases, more power is required to maintain recirculation. 

The powerplant in orientation B exhibited the worst performance; this corresponded to orientation B 

having the highest pump currents during the test. These higher pump currents are likely due to increased 

humidification or liquid water within the powerplant that required higher pump currents to recirculate. 

The presence of liquid water or high levels of humidification within the reactant streams act to dilute the 

reactant concentration within the fuel cell, resulting in a depressed fuel cell stack voltage. 
NASA/TM—2011-216224 15 

Mission Profile Test 

The mission profile test was a 10-day mission simulation used to address stability and performance 

during extended periods of operation as would be required during a typical Shuttle mission. There were two, 

10-day mission profile tests completed during the course of initial performance evaluation testing. The first 

test was performed in orientation A, and the second test was performed in orientation C the following 

month. The first mission profile test shut down 15.5 hr short of completion because the oxygen pump 

current was less than 1 A. This is one of the built-in shutdown parameters for the EM powerplant. It 

indicates that some part of the powerplant supporting ancillary subsystem is not operating correctly. In the 

case of ancillary failure, the powerplant goes into shutdown mode to prevent potential damage to the fuel 

cell stack. In this case, the shutdown message indicated that the oxygen recirculation pump had stopped 

operating. The Teledyne EM powerplant computer was rebooted to clear the error code and the powerplant 

was restarted without incident. The mission profile test was continued, backtracking 4 hr previously into the 

test to ensure overlap. 

Overall, EM performance was comparable for both tests, shown by the stack voltages plotted in 

Figure 16. The mission profile test was not able to be conducted in orientation B because of a necessary 

repair to the oxygen recirculation pump. The mission profile test could not be conducted after the repair as 

the powerplant was delivered to the Johnson Space Center for additional environmental tests. One 

significant finding to note is the degradation of the stack voltage during the constant-power-level portions of 

the test. Upon examination, none of the system parameters of temperature or pressure mirrored this change. 

As a result, some other factor is affecting the long-term performance of the powerplant. Two possible causes 

include a buildup of impurities in the powerplant system over time due to insufficient purge time or 

frequency, or a slow buildup of water within the powerplant system due to incomplete removal of the water 

during powerplant operation. Figure 17 shows this voltage degradation is completely reversible upon system 

purge. After the powerplant unexpectedly shut down in the latter portion of the mission profile test, the 

system automatically went into a system purge. When the powerplant was restarted, and the power profile 

backed up 6 hr to ensure overlap, it was seen that a significant voltage recovery occurred that cannot be 

accounted for by variations in the powerplant system operational parameters. 
NASA/TM—2011-216224 16 
NASA/TM—2011-216224 17 

During the tests in both orientations, water was observed percolating through the fuel cell stack. This 

was indicated by subtle drops and recoveries in the cell voltages, which started at the front of the stack 

and percolated through to the end of the stack. These cell voltage variations were not captured by the data 

acquisition system because of the collection interval, which was every 2 min. However, the percolation of 

water can be observed in the response of the hydrogen and oxygen recirculation pump currents 

(see Figs. 18 and 19). The large variation in pump currents indicates variable density fluids being moved 

through the powerplant, that is, water entrained within the reactant streams. 
NASA/TM—2011-216224 18 

Reactant Supply Gas Effects 

A portion of the EM tests were performed at NASA Glenn Research Center with hydrogen and oxygen 

gas that varied in concentration or overall purity. The purpose of these tests was to see how the varying 

reactant gas concentrations affect overall stack performance as well as performance of balance of plant 

components over time. The majority of the tests were run with gas supplied from tube trailers with purity 

levels of 99.997 percent for hydrogen and 99.5 percent for oxygen. (Propellant-grade hydrogen and oxygen 

purity levels are 99.995 and 99.6 percent, respectively.) There were a select number of tests performed with 

ultrahigh purity (UHP) gas for both reactants. UHP gas concentrations were 99.999 percent for hydrogen 

and 99.995 percent for oxygen. 

The calibration series test was conducted using the UHP reactants. Figure 20 shows a significant 

difference in the powerplant’s performance when operating with propellant-grade reactants. The overall 

fuel cell stack voltage was higher for the higher purity reactants; this is expected as fuel cell performance 

is a function of reactant concentration. The impurities found in propellant-grade reactants act as a diluent, 

thus lowering the hydrogen and oxygen concentration. Another significant difference to note is the lack of 

the sawtooth pattern exhibited by the test run using UHP reactants. As discussed before, this pattern is a 

result of intermittent burping of the powerplant to release built up impurities. The interval period for 

burping the powerplant remained the same for the higher purity reactant test. Since a much lower 

concentration of impurities built up during that time, no significant change in voltage was observed when 

the system was burped.

There was a more significant difference between the propellant-grade and high purity reactants early 

in the test. Figure 21 shows this variation is likely due to the difference in oxygen inlet temperature 

observed during the two tests. The reactants are stored outside and are subject to significant variations in 

temperature from day to day. These two tests were performed on different days. 
NASA/TM—2011-216224 19 

As a result of the voltage degradation observed over time during the mission profile test, an additional 

test using propellant-grade reactants and high purity reactants was conducted using a constant current 

power profile. This was performed to differentiate between two potential causes for the voltage 

degradation observed, that is, a buildup of impurities that were not entirely purged from the powerplant 

system during the intermittent burps and the buildup of water in the system over time. As can be seen in 

Figure 22, during the duration of the test, using an identical power load, the test utilizing high purity 

reactants showed significantly more degradation than the test utilizing propellant-grade reactants. 
NASA/TM—2011-216224 20 

The noisier voltage response for the propellant-grade reactants is again the result of the intermittent 

burping of the system and the concomitant voltage recovery. As a result of this test, it is obvious that the 

buildup of impurities is not the cause of the reversible degradation. Rather, it is likely because of the slow 

buildup of product water in the system that has not been entirely removed from the powerplant. Typically, 

the higher the oxygen concentration, the higher quantities of water produced. 

Overall Performance Effects 

Loss of Coolant Test 

The loss of coolant test was intended to measure the response of the powerplant in the event of the 

external thermal loop shutting down. The test is a variation of the performance load profile test. 

Approximately 6 hr into the performance load profile test, at a power load of 226 A (7 kW), the external 

coolant loop is turned off for 9 min. After 9 min, the external coolant loop is turned back on and the 

performance load profile is continued at 192 A. Success is measured by the ability of the EM powerplant 

to maintain temperatures below 70 °C during the interval while the facility (external) coolant loop is shut 

off. The EM powerplant temperatures exceeded the upper temperature limit of 70 °C, 7 min and 37 s into 

the 9-min interval (see Figs. 23 and 24). The EM powerplant did not have sufficient thermal mass to 

absorb the waste heat produced by the fuel cell stack during the 9 min at 7 kW. 

Powerplant Performance 

The EM powerplant was extensively tested at NASA Glenn over a variety of conditions, including 

orientation, varying power profiles, and varying incoming reactant conditions. Nine months of total 

performance testing was conducted at NASA Glenn prior to delivery to NASA Johnson Space Center for 

environmental testing. Overall, the powerplant performed very well. 
NASA/TM—2011-216224 21 

TABLE II.—OPERATIONAL CHARACTERISTICS OF THE ENGINEERING MODEL 

FOR THE FIRST AND LAST CALIBRATION SERIES TESTS 

Operational characteristics Calibration series test 

8/26/05 

Calibration series test 

5/25/06 

Hydrogen in (TP1), °C 43.0 to 54.9 38.3 to 55.6 

Hydrogen out (TP2), °C 40.9 to 57.8 40.6 to 56.8 

Oxygen in (TP3), °C 52.7 to 61.5 44.4 to 62.0 

Oxygen out (TP4), °C 43.7 to 66.2 42.8 to 65.5 

Coolant in (TP5), °C 44.7 to 61.1 45.1 to 60.4 

Coolant out (TP6), °C 42.9 to 63.4 42.3 to 62.4 

Hydrogen temperature into powerplant, °F 66.6 to 77.9 66.3 to 72.5 

Oxygen temperature into powerplant, °F 67.0 to 72.8 66.4 to 70.5 

Stack voltage, V 26.8 to 40.2 27.1 to 40.6 

Average cell voltage, V 0.688 to 1.030 0.697 to 1.041 

Cell differential, V 0.011 to 0.043 0.009 to 0.031 

Table II compares data between the first and last test run with Figure 25 providing the stack voltage 

trends for each calibration series test. The EM stack achieved about 1114 hr of operation, and overall the 

stack performed well with no observed dropoff in performance being noted. This was an approximate run 

time because the system operational hours had, at one point, reset during operation. 

During the 9-mo test period, persistent problems occurred with regards to the operation of the reactant 

recirculation pumps and the water separator units. These problems manifested themselves almost 

exclusively during startup of the powerplant, often necessitating manual intervention to transition the 

ancillaries to operational status. However, almost without exception, once the ancillaries were operational, 

they performed well without problems. The root of the problems was found to be a function of quality 

control as well as motor controller function. As an example, significant issues were encountered during 

startup of the oxygen recirculation pumps. These problems escalated as testing continued. Eventually, the 

recirculation pump became nonoperational. It was disassembled, and after discussions with the 

manufacturer, it was found that the internal “wetted” surfaces had been manufactured with materials 

incompatible with oxygen use. As the material degraded, the performance of the recirculation pump was 

compromised. 
NASA/TM—2011-216224 22 

Conclusion 

The performance of the fuel cell stack and the ancillary components was insensitive to changes in the 

orientation of the powerplant. Gravitational effects did not affect the performance of the fuel cell 

powerplant. 

System ancillaries, specifically the gas circulation pumps and gas and water separators, experienced 

the most variability in performance and required the most maintenance to sustain operations. The 

hydrogen water separator had to be manually rotated numerous times, and the oxygen pump with 

controller went through several replacements. In general, the problems encountered with the ancillary 

components were mainly one of quality control, being issues of incompatible materials, bad controllers, 

and manufacturing tolerances. Once the powerplant system was fully operational for each test run, the 

stack performed exceptionally well with little variation in the cell-to-cell voltages. This was indicative of 

a good powerplant design in that the performance of each cell within the 117-cell stack (39 cells per 

substack) performed nearly the same. Each cell was provided adequate reactants, and the product water 

removed efficiently. 

The EM design goals that were met have been summarized in Table III. System ancillaries were 

temperamental and would at times not start as designed. The ancillaries generally did not allow a clean 

startup to occur on each testing day. Once the system was operational though, the EM was generally seen 

to complete each test. This resulted in the maintenance-free operation for 3000 hr goal not being met. The 

loss of coolant test was intended to measure the response of the powerplant in the event of the external 

thermal loop shutting down. The EM powerplant did not have sufficient thermal mass to absorb the waste 

heat produced by the fuel cell stack during the 9 min at 7 kW; hence, the loss of a secondary coolant loop 

goal was not satisfied. 
NASA/TM—2011-216224 23 

TABLE III.—DESIGN GOALS OF THE TELEDYNE ENGINEERING MODEL POWERPLANT 

Engineering model design goals Verification status 

Produce 2 to 12 kW of electrical power within a voltage range of 

33 to 27 VDC 

Met at Glenn Research Center 

Gravity and orientation independent operation Met at Glenn Research Center 

Maintenance-free operation for 3000 hr Did not meet at Glenn Research Center 

90 percent of the final change in voltage shall occur within 0.2 s Met at Glenn Research Center 

Shall be capable of automatic startup to 3 kW in less than 5 s if 

reactants are present, initial stack temperature is greater than 

40 °F, and no inerts are present 

Met at Glenn Research Center 

Shall be capable of shutdown in less than 1 min Met at Glenn Research Center 

Shall be capable of operating on propellant-grade (MIL PRF–

27201C) and higher purity hydrogen and propellant-grade 

(MIL PRF–25508F) and higher purity oxygen 

Met at Glenn Research Center 

Operating life shall be greater than 3000 hr Not yet met 

Shall be capable of operation for 9 min at 7 kW without cooling 

from a secondary coolant loop 

Did not meet at Glenn Research Center 

Shall be capable of a minimum 250 stop/start cycles Not yet met 

Follow-On Research 

Follow-on efforts will utilize passive system components in place of the active circulation pumps and 

gas and water separators. An upgraded breadboard stack with thinner membranes and lighter bipolar 

plates will also be utilized in the overall passive fuel cell system. Both stack and system performance will 

be closely monitored throughout each individual test. Specifically, the upgraded breadboard stack’s 

performance will be observed to see if any changes in performance occur over time, and the passive 

components will be monitored throughout to document how they respond to changes in load and under 

steady-state conditions. Direct performance comparisons to the active components will then be able to be 

made.

NASA/TM—2011-216224 25 

Appendix A.—Calibration Series Test 

The calibration series test was a reference test of the engineering model (EM). The series was 

composed of a polarization test and an abbreviated version of the performance load profile test. This test 

was performed at specified intervals during the evaluation of the EM at Teledyne, NASA Glenn, and 

NASA Johnson Space Center. The calibration series test was used to quantify performance changes of the 

EM as a function of shipping, orientation effects, and damage as a result of testing and age. The stack 

voltage in the table was the average of the last four readings taken July 20, 2005, during the calibration 

series acceptance test at Teledyne. 

TABLE IV.—ENGINEERING MODEL CALIBRATION SERIES TEST CONDITIONS 

Element 

no. 

Increment 

time, 

s 

Current, 

A 

Teledyne data 

recording interval, 

s 

NASA Glenn data 

recording interval, 

s 

Stack voltage, 

V 

Total time, 

s 

Current 

density, 

mA/cm2

1 300 0 5 5 40.34 300 0 

2 300 22.65 5 5 35.04 600 25 

3 300 45.3 5 5 34.13 900 50 

4 300 67.95 5 5 33.47 1200 75 

5 300 90.6 5 5 32.93 1500 100 

6 300 135.9 5 5 32.06 1800 150 

7 300 181.2 5 5 31.47 2100 200 

8 300 271.8 5 5 30.23 2400 300 

9 300 362.4 5 5 29.27 2700 400 

10 300 453 5 5 28.31 3000 500 

11 300 362.4 5 5 29.22 3300 400 

12 300 271.8 5 5 30.22 3600 300 

13 300 181.2 5 5 31.31 3900 200 

14 300 135.9 5 5 32.07 4200 150 

15 300 90.6 5 5 32.93 4500 100 

16 300 67.95 5 5 33.46 4800 75 

17 300 45.3 5 5 34.14 5100 50 

18 300 22.65 5 5 35.17 5400 25 

19 300 0 5 5 40.74 5700 0 

20 20 0 5 5 40.74 5720 0 

21 120 174 5 5 31.17 5840 192

22 1200 135 5 5 31.83 7040 149

23a 55 51 5 5 33.91 7095 57 a

23b 5 51 5 1 -------- 7100 57 a

24a 5 357 5 1 -------- 7105 394

24b 55 357 5 5 28.72 7160 394 

25 60 51 5 5 33.96 7220 57

26 60 192 5 5 30.86 7280 212

27 180 468 5 5 27.91 7460 516

28 1200 192 5 5 30.87 8660 212

29a 55 357 5 5 28.80 8715 394 a

29b 5 357 5 1 -------- 8720 394 a

30a 5 51 5 1 -------- 8725 57

30b 55 51 5 5 34.06 8780 57 

31 30 0 5 5 40.33 8810 0 

32 60 192 5 5 30.88 8870 212

33 40 51 5 5 33.92 8910 57

34 60 192 5 5 30.84 8970 212

35 40 468 5 5 27.40 9010 516
NASA/TM—2011-216224 26 

TABLE IV.—Concluded. 

Element 

no. 

Increment 

time, 

s 

Current, 

A 

Teledyne data 

recording interval, 

s 

NASA Glenn data 

recording interval, 

s 

Stack voltage, 

V 

Total time, 

s 

Current 

density, 

mA/cm2

36 60 192 5 5 31.03 9070 212

37 40 104 5 5 32.60 9110 115

38 60 192 5 5 30.88 9170 212

39 40 431 5 5 27.76 9210 476

40 60 192 5 5 31.00 9270 212

41 40 164 5 5 31.42 9310 180

42 60 192 5 5 31.03 9370 212

43 40 357 5 5 28.73 9410 394

44 60 192 5 5 31.06 9470 212

45 40 226 5 5 30.49 9510 249

46 60 192 5 5 31.00 9570 212

47 40 288 5 5 29.56 9610 318

48 150 192 5 5 30.92 9760 212

49 60 0 5 5 40.37 9820 0 a

Voltage transients occurred at the element numbers marked, and at these locations data was recorded at 200 kHz using the 

DataMax software. 
NASA/TM—2011-216224 27 

Appendix B.—Performance Load Profile Test Description 

The performance load profile test was a benchmark test of the engineering model (EM). This test was 

used to evaluate the performance of the EM under different operational conditions, such as orientation 

and vibration. The performance load profile test was carried out at Teledyne and NASA Glenn. The stack 

voltage in the table was the average voltage during each step as observed July 19, 2005, during the 

performance load profile acceptance test at Teledyne. 

TABLE V.—ENGINEERING MODEL PERFORMANCE LOAD PROFILE TEST CONDITIONS 

Element 

no. 

Increment 

time, 

s 

Current, 

A 

Teledyne data 

recording 

interval, 

s 

NASA Glenn 

data recording 

interval, 

s 

Stack 

voltage, 

V 

Total time, 

s 

Current 

density, 

mA/cm2

1 30 0 5 5 39.93 30 0 

2 120 174 5 5 31.97 150 192

3 3600 135 5 5 32.11 3750 149

4a 3295 51 5 5 33.70 7045 57 a

4b 5 51 5 1 -------- 7050 57 a

5a 5 357 5 1 -------- 7055 394

5b 895 357 5 5 29.04 7950 394

6 3600 51 5 5 33.75 11550 57

7 960 192 5 5 30.77 12510 212

8 180 468 5 5 27.63 12690 516

9 6120 192 5 5 30.82 18810 212

10a 895 357 5 5 28.80 19705 394 a

10b 5 357 5 1 -------- 19710 394 a

11a 5 51 5 1 -------- 19715 57

11b 1675 51 5 5 33.75 21390 57 

12 30 0 5 5 40.32 21420 0 

13 860 192 5 5 30.75 22280 212

14 40 51 5 5 33.89 22320 57

15 860 192 5 5 30.74 23180 212

16 40 468 5 5 27.13 23220 516

17 860 192 5 5 30.82 24080 212

18 40 104 5 5 32.48 24120 115

19 860 192 5 5 30.77 24980 212

20 40 431 5 5 27.57 25020 476

21 860 192 5 5 30.80 25880 212

22 40 164 5 5 31.21 25920 180

23 860 192 5 5 30.78 26780 212

24 40 357 5 5 28.48 26820 394

25 860 192 5 5 30.79 27680 212

26 40 226 5 5 30.20 27720 249

27 860 192 5 5 30.77 28580 212

28 40 288 5 5 29.38 28620 318

29 150 192 5 5 30.82 28770 212

30 60 0 5 5 40.40 28830 0 a

Voltage transients occurred at the element numbers marked, and at these locations data was recorded at 200 kHz using the 

DataMax software. 

NASA/TM—2011-216224 29 

Appendix C.—Fifty Percent of Capability Test 

The 50 percent of capability test was an evaluation of the speed of the response of the engineering 

model (EM) to loads after rapid startup. The EM was started using the rapid start procedure, which 

included purging the unit of nitrogen but did not include a warmup of the fuel cell or powerplant. After 

completion of this test, the powerplant was shut down and restarted using the normal startup procedure 

for the remainder of the day’s testing. The stack voltage in the table was the average voltage during each 

step as observed July 19, 2005, during the performance load profile acceptance test at Teledyne. 

TABLE VI.—ENGINEERING MODEL 50 PERCENT OF CAPABILITY TEST CONDITIONS 

Element 

no. 

Increment 

time, 

s 

Current, 

A 

Teledyne data 

recording interval, 

s 

NASA Glenn 

data recording 

interval, 

s 

Stack 

voltage, 

V 

Total time, 

s 

Current 

density, 

mA/cm2

1 5 0 1 1 39.93 5 0 

2 120 164 1 1 31.21 125 181

3 5 0 1 1 130 0 

NASA/TM—2011-216224 31 

Appendix D.—Mission Profile Test 

The mission profile test is used to measure the performance of the engineering model (EM) 

powerplant over a power profile and duration representative of future missions. The test is run 

uninterrupted for the entire 240 hr. 

TABLE VII.—ENGINEERING MODEL MISSION PROFILE TEST 

Element 

no. 

Increment 

time, 

s 

Current, 

A 

Teledyne data 

recording interval, 

s 

NASA Glenn data 

recording interval, 

s 

Total time Current 

density, 

mA/cm2

Comments 

1a 

5 hr 

55 min 200 300 150 

5 hr 

55 min 221 Restart 

1b 5 min 200 300 5 6 hr 221 Restart 

2a 5 min 128 300 5 

6 hr 

5 min 142 Prelaunch 

2b 

5 hr 

50 min 128 300 150 

11 hr 

55 min 142 Prelaunch 

2c 5 min 128 300 5 12 hr 142 Prelaunch 

3a 5 min 237 300 5 

12 hr 

5 min 262 Launch 

3b 50 min 237 300 150 

12 hr 

55 min 262 Launch 

3c 5 min 237 300 5 13 hr 262 Launch 

4a 5 min 200 300 5 

13 hr 

5 min 221 Mission 

4b 

191 hr 

50 min 200 300 150 

204 hr 55 

min 221 Mission 

4c 5 min 200 300 5 205 hr 221 Mission 

5a 5 min 128 300 5 

205 hr 

5 min 142 

Landing and 

calibration 

5b 

17 hr 

50 min 128 300 150 

222 hr 55 

min 142 

Landing and 

calibration 

5c 5 min 128 300 5 223 hr 142 

Landing and 

calibration 

6 0.5 61 300 5 223.5 67 Calibration 

7 0.5 400 300 5 224 442 Calibration 

8 0.5 237 300 5 224.5 262 Calibration 

9 0.5 164 300 5 225 180 Calibration 

10a 5 min 128 300 5 

225 hr 

5 min 142 

Landing and 

calibration 

10b 

3 hr 

50 min 128 300 150 

228 hr 55 

min 142 

Landing and 

calibration 

10c 5 min 128 300 5 229 hr 142 

Landing and 

calibration 

11a 5 min 0 300 5 

229 hr 

5 min 0 Cooldown 

11b 

10 hr 

55 min 0 300 150 240 hr 0 Cooldown 

NASA/TM—2011-216224 33 

Appendix E.—Loss of Coolant Test 

The loss of coolant test is used to evaluate the performance of the engineering model (EM) 

powerplant when the cooling system external to the powerplant is interrupted. During this test, the facility 

cooling system is interrupted at the beginning of element no. 14 and then restarted at the beginning of 

element no. 15. 

TABLE VIII.—ENGINEERING MODEL LOSS OF COOLANT TEST 

Element 

no. 

Increment 

time, 

s 

Current, 

 A 

Teledyne data 

recording interval, 

s 

NASA Glenn data 

recording interval, 

s 

Stack 

voltage, 

V 

Total 

time, 

s 

1 30 0 5 5 30 0 

2 120 174 5 5 150 192 

3 3600 135 5 5 3750 149 

4 3300 51 5 5 7050 56 

5 900 357 5 5 7950 394 

6 3600 51 5 5 11550 56 

7 960 192 5 5 12510 212 

8 180 468 5 5 12690 517 

9 6120 192 5 5 18810 212 

10 900 357 5 5 19710 394 

11 1680 51 5 5 21390 56 

12 30 0 5 5 21420 0 

13 860 192 5 5 22280 212 

14 540 226 5 5 22820 249 

15 5980 192 5 5 28800 212 

NASA/TM—2011-216224 35 

Appendix F.—Constant Load Test 

The constant load tests were performed in order to see if improvements would be made in 

performance with the engineering model (EM) stack warmed up prior to changing its orientation as well 

as immediately following the change to its new orientation. The tests also were performed using ultrapure 

hydrogen and oxygen gas to help explain the voltage degradation observed while performing the mission 

profile under the same load condition with the gas supply coming from the hydrogen and oxygen tube 

trailers. Each test’s profile is provided in Table IX. 

TABLE IX.—CONSTANT LOAD PROFILE TEST WITH VARYING REACTANT GAS CONCENTRATIONS 

Element 

no. 

Increment 

time, 

s 

Current, 

A 

Teledyne data 

recording interval, s 

NASA Glenn data 

recording interval, 

s 

Total time, 

s 

Current 

density, 

mA/cm2

1 Varied for 

individual runs 

200 5 5 Varied for 

individual runs 

221 
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01-04-2011 

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4. TITLE AND SUBTITLE

Proton Exchange Membrane Fuel Cell Engineering Model Powerplant 

Test Report: Benchmark Tests in Three Spatial Orientations

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Loyselle, Patricia; Prokopius, Kevin 

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WBS 038957.04.06.03.03 

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John H. Glenn Research Center at Lewis Field 

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14. ABSTRACT

Proton exchange membrane (PEM) fuel cell technology is the leading candidate to replace the aging alkaline fuel cell technology, currently 

used on the Shuttle, for future space missions. This test effort marks the final phase of a 5-yr development program that began under the 

Second Generation Reusable Launch Vehicle (RLV) Program, transitioned into the Next Generation Launch Technologies (NGLT) 

Program, and continued under Constellation Systems in the Exploration Technology Development Program. Initially, the engineering model 

(EM) powerplant was evaluated with respect to its performance as compared to acceptance tests carried out at the manufacturer. This was to 

determine the sensitivity of the powerplant performance to changes in test environment. In addition, a series of tests were performed with 

the powerplant in the original standard orientation. This report details the continuing EM benchmark test results in three spatial orientations 

as well as extended duration testing in the mission profile test. The results from these tests verify the applicability of PEM fuel cells for 

future NASA missions. The specifics of these different tests are described in the following sections.

15. SUBJECT TERMS

Fuel cell power plants; Electric power supplies; Energy sources; Spacecraft power supplies; Electric power; Energy storage; Fuel cells 

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