Development of analysis guidelines for Exploration Life Support (ELS) technology tests was completed. The guidelines were developed based on analysis experiences gained from supporting Environmental Control and Life Support System (ECLSS) technology development in air revitalization systems and water recovery systems. Analyses are vital during all three phases of the ELS technology test: pre-test, during test and post test. Pre-test analyses of a test system help define hardware components, predict system and component performances, required test duration, sampling frequencies of operation parameters, etc. Analyses conducted during tests could verify the consistency of all the measurements and the performance of the test system. Post test analyses are an essential part of the test task. Results of post test analyses are an important factor in judging whether the technology development is a successful one. In addition, development of a rigorous model for a test system is an important objective of any new technology development. Test data analyses, especially post test data analyses, serve to verify the model. Test analyses have supported development of many ECLSS technologies. Some test analysis tasks in ECLSS technology development are listed in the Appendix. To have effective analysis support for ECLSS technology tests, analysis guidelines would be a useful tool. These test guidelines were developed based on experiences gained through previous analysis support of various ECLSS technology tests. A comment on analysis from an experienced NASA ECLSS manager (1) follows: "Bad analysis was one that bent the test to prove that the analysis was right to begin with. Good analysis was one that directed where the testing should go and also bridged the gap between the reality of the test facility and what was expected on orbit.

Jeng, Frank F.

NASA Technical Reports Server

 
Engineering and Science Contract Group 
2224 Bay Area Boulevard 
Houston, Texas  77058 
  
 
 
November 15, 2007 
ESCG-4470-07-TEAN-DOC-0173 
 
To: M. S. Anderson /NASA 
 
 
 
From: F. F. Jeng  /ESCG 
 
SUBJECT:  Test Analysis Guidelines 
 
Summary:  Development of analysis guidelines for Exploration Life Support (ELS) technology 
tests was completed.  The guidelines were developed based on analysis experiences gained 
from supporting Environmental Control and Life Support System (ECLSS) technology 
development in air revitalization systems and water recovery systems. 
 
1.0 Introduction 
Analyses are vital during all three phases of the ELS technology test: pre-test, during test and 
post test.  Pre-test analyses of a test system help define hardware components, predict 
system and component performances, required test duration, sampling frequencies of 
operation parameters, etc.  Analyses conducted during tests could verify the consistency of 
all the measurements and the performance of the test system.   Post test analyses are an 
essential part of the test task.  Results of post test analyses are an important factor in judging 
whether the technology development is a successful one.  In addition, development of a 
rigorous model for a test system is an important objective of any new technology 
development.  Test data analyses, especially post test data analyses, serve to verify the 
model.  Test analyses have supported development of many ECLSS technologies.  Some 
test analysis tasks in ECLSS technology development are listed in the Appendix.  To have 
effective analysis support for ECLSS technology tests, analysis guidelines would be a useful 
tool.  These test guidelines were developed based on experiences gained through previous 
analysis support of various ECLSS technology tests.   
 
A comment on analysis from an experienced NASA ECLSS manager (1) follows: ”Bad 
analysis was one that bent the test to prove that the analysis was right to begin with.  Good 
analysis was one that directed where the testing should go and also bridged the gap between 
the reality of the test facility and what was expected on orbit”.  This comment points out the 
importance of understanding the developed technology and development of its model. 
 
https://ntrs.nasa.gov/search.jsp?R=20080009582 2019-08-30T03:43:09+00:00Z
November 15, 2007 
ESCG-4470-07-TEAN-DOC-0173 
p. 2 
 
  
2.0 Pre-test Analysis 
There are several steps that are important to the Pre-test Analysis: 
 
Assist in developing goals and requirements for the test.  This should be done as early as 
possible in the test planning.  The analyst should consider what tests and measurements are 
needed to develop and validate technologies and their models.  The analyst should also 
consider what technology and operational data are needed for potential trade studies.  The 
selection of test environments and ersatz solutions is important at this stage. 
 
Understand the test system - Obtain and understand detailed schematic, process and 
instrument diagrams (P&ID) and control logic of the test system.  If essential components/ 
instruments are missing, ask the engineer/manager responsible for the test hardware to 
install the essential components / instruments.  
 
Collect maximum hardware information up front.  Collect detailed drawings of major 
components of the test.  Collect or prepare performance information or curves for all major 
components of the test system, such as blower, pump, compressor, heat exchanger, 
adsorption units, instrument, etc.  The following are examples of components and their 
essential information: 
 
 Blower, pump, compressor – performance curves for the fluid mover.   
 
 Conduct a relatively detailed hydraulics analysis (pressure drop) of the test system 
 before the test.  Always allow enough margin for pressure drop (say >15%) for 
 unpredicted conditions.  Make sure the system can take the pressure of the fluid driver 
 when the fluid flow is accidentally blocked.  Have the pressure relief set at this 
 deadhead pressure. 
 
 Temperature measurement – make sure thermocouples are the correct types for the 
 expected temperature range. 
 
 Heat exchanger – prepare heat transfer performance curves which can be used to 
 check the performance of the heat exchanger.  
 
 Heater – allow for heat loss to ambient in sizing. 
 
 Thermal fluid – check vapor pressure and whether it is hazardous to humans if it is 
 used in an open system. 
 
 Set points of relief valves – use American Society of Mechanical Engineers (ASME) 
 guidelines. 
 
 Vacuum level – conduct detailed pressure drop calculations for ducts operated at sub-
 ambient pressure. 
 
 Measure surface temperature of the hardware if an energy balance is essential – heat 
 dissipation rate from the hardware has significant impacts on energy balance in crew 
 systems. 
November 15, 2007 
ESCG-4470-07-TEAN-DOC-0173 
p. 3 
 
  
 
 Dew point measurement – dew point measurements often are erroneous.  One 
 technique to check dew point measurements is performing a moisture mass balance 
 analysis of the subsystem.  
 
 Separation of liquid/vapor – allow enough residence time or use dynamic mechanism    
 for separating vapor and liquid. 
 
Assist test engineers in defining test parameters and their values, number of test points, and 
test duration.  Operating parameter values include those in nominal operation and in 
contingency.  Number of test points depends on available resources: budget, time, personnel.  
For a complex test task, a test design based on a statistical analysis should be considered.  
Test duration can be decided based on pre-test simulation results and initial function tests of 
the test system. 
 
Collect desirable data measurements from parties involved in the test to make a complete 
data measurement list.  Different parties may want different parameters for analyzing their 
unique functions.  This is especially true for test projects involving multiple centers or 
institutions. 
 
Specify data collection – test duration, number of data channels, data format and number of 
digits, measurement frequency, and available storage capacity.   
 
Define desirable real-time data (pseudo) calculations with the required formula.  “Pseudo” 
measurements are gathered from many channels or a combination (delta P from two 
pressures, etc).  Other examples include Relative Humidity (RH) to dewpoint to ppH2O, heat 
load based on flow and two temperatures, etc. 
 
Record test interfaces and facility parameters (vacuum quality, ambient air humidity levels, 
heat load from electronics not included in the test, surface temperature, actual sensor 
locations, etc).   
 
Record parameters of test system environment (temperature, pressure, humidity). 
 
Have a real time data dump, plotting software and computer at the test site.  This can be very 
helpful for a quick check of the performance of components or the system. 
 
Set up methods, macros, etc to process data files very quickly – set up macros to process 
data so a quick check of the performance of critical components or a quick review of the 
performance of the whole system can be done. 
 
Develop a model (perhaps a simpler model in the beginning of the test) before the test and 
make sure it fits the test system.  Refine the model as more test data are collected during the 
test program.  Development of a rigorous model is always an advantage for technology 
development. 
 
Predict test results using a developed model.  Model predictions can be used for: 
• Selecting components and instruments for the test 
November 15, 2007 
ESCG-4470-07-TEAN-DOC-0173 
p. 4 
 
  
• Providing essential information for a test plan: such as test duration, test parameter 
values, number of test points 
 
When conducting the energy balance of an air loop, don’t overlook energy dissipation effects 
from a fan and energy effects from pressure drop. 
 
Review operating conditions of vendor-supplied components.  Different operating conditions 
will produce different operation results. 
 
Don’t take things for granted.  For example, without an adequate fan circulation system the 
cabin air properties won’t be uniform. 
 
A system with simpler designs always is more dependable. 
 
Allow appropriate margin for hidden or unpredicted conditions in all component sizing 
analysis; this applies to sizing of blower, pump, heat exchanger, heater, and reactors.  Allow 
more design margin for components with more uncertainty, such as reactors.  
 
The following technologies can be used to generate moisture for Air Revitalization System 
(ARS) tests: bubbling air in a water bath, directly heating water with a hot medium, passing 
an air stream through a water-flooded packed bed, dripping a water stream on a hot plot, etc.  
All have pros and cons.  The challenges associated with these technologies include dew 
point measurement, transferring the generated humidity to the test system without 
condensing part of generated moisture somewhere along the path, and response time of 
steam generation. 
 
Make sure low point draining of condensate is built into all air ducts. 
 
There are commercially available software packages which display schematics and essential 
real time data on the schematic; this can be very helpful in monitoring a large test system.  
 
3.0 Analysis during Test 
Conduct leak checks of the test system – check to see whether there is leakage out from 
pressurized components or leakage in from external to sub-ambient pressure test systems. 
 
Make sure the required conditions specified by component/instrument vendors are met to 
ensure reliable operations/measurements.  For example, is there adequate vacuum for 
desorption or for sampling?  Is there adequate cooling for the chilled mirror dew point meter?  
Is there enough air flow rate?  Is the minimum straight duct length requirement between a 
flow meter and its nearest fitting met? 
 
Check instrumentation precision and accuracy (location may play a role) 
 
Humidity is difficult to measure accurately – check instrument accuracies and perform a mass 
balance calculation as a validation check.  
 
Resolve problems or figure out why results do not meet expectations. 
 
November 15, 2007 
ESCG-4470-07-TEAN-DOC-0173 
p. 5 
 
  
Make sure all measurements, such as temperature, pressure, concentration, are reasonable 
and satisfy common sense.  Perform mass or energy balance calculations of the test system; 
it is one way to check measurement consistency.  When most of the test data are in doubt, a 
duplicate test of the current test point should be considered as a method of validation. 
 
Instrumentation or other problems can mean that results aren’t perfect.  Sometimes people 
believe the data when they shouldn’t and other times people brush it off as instrumentation 
error when it is actually correct.  Be suspicious of data, but try to figure out why it might be 
true (mechanisms not included in the model, etc.). 
 
As knowledge is gained during the test, close the loop and go back to the model and make 
updates based on what has been learned, and ask for follow-on testing to explore new areas 
of need (off nominal, focus on a different process mechanism).  New test points might be 
added at the end of current test series rather than waiting for a new test.  The capability to 
quickly process a test data file, such as a spreadsheet model, is desirable so that the 
performance of the test system can be quickly analyzed and decisions regarding whether or 
not to add additional test points at the end of this series can be made.  
 
Look for measures of consistency real time – ensure consistency and be ready to 
troubleshoot during test (bad sensor? leak?)  Otherwise bad data will make the test sequence 
not useful. 
 
When troubleshooting a pressure swing adsorption system, be suspicious regarding the 
pressure level in desorption beds; it may not be low enough because of external air leaking 
in.  Be suspicious whether the adsorption bed is saturated with moisture. 
 
Be suspicious of leaks at various connections when the test system is operated at sub-
ambient pressure. 
 
Tracking humidity in the air loop is challenging.  Because the air temperature in the chamber 
may not be uniform, some moisture might condense.  Make sure the air duct temperature or 
chamber wall temperature is always above the dew point, for example by heat tracing.  A 
humidity mass balance (dew point measurement, steam/water balance) always is a 
challenging issue. 
 
For water processing equipment, constituent mass balances should be performed.  Ion 
balances (electroneutrality calculations) should also be performed for aqueous streams.  
These balances can help identify measurement problems and unexpected or unmeasured 
losses due to volatility or precipitation. 
 
Review the performance of the test system setup.  Is there modification/change of test 
hardware necessary to obtain better performance or better measurements, based on the test 
data? 
 
4.0 Post Test Analysis  
The purpose of post test analysis is to use the collected test data for validating and improving 
the developed model.  Post test analysis also builds confidence in the model for use in 
November 15, 2007 
ESCG-4470-07-TEAN-DOC-0173 
p. 6 
 
  
evaluating flight conditions that can not be tested, or for predicting conditions that have not 
been tested. 
 
In many test cases, the test data does not meet expectations and sometimes deviates 
significantly from the predicted results.  The post test analysis goals include problem 
resolution, analysis of the test data, and/or figuring out why results aren’t as expected. 
 
Every deviation from model predictions has its cause.  Finding out the causes and solutions, 
whether they are measuring errors or model deficiencies, is very challenging.   
 
Data mining generates huge data files, and takes a lot of effort to analyze the data.  Since 
test costs are significant, it is good idea to collect as much information as possible for later 
use.  Good pre-test arrangement of the data collection helps.   
 
When you learn something in the test, close the loop and update the model based on what 
you’ve learned. It is often beneficial to request for follow-on testing to explore things not 
previously investigated, such as off nominal or focus on a different process mechanism. 
 
A perfect match between test data and model predictions is almost impossible.  Due to 
schedule and budget considerations, model improvement should stop at a certain point 
where its prediction is within a tolerable limit from test results.  The tolerable limit might be 
decided between the model developer and hardware developer or the user.  In general, the 
fidelity of a technology model is driven by its intended use and by the importance of different 
phenomena that can be described by the model.  The primary goal of any model is to obtain 
a fundamental understanding of the process. 
 
Use help from experts.  Many times excellent models might have already been developed by 
outside sources.  Using existing and verified models in developing new models can 
significantly save analysis resources. 
 
5.0 General Notes 
Reference existing test plans, documents, test correlation efforts, etc. where available.   
 
Two reports, a quick look test report and/or a detailed formal report, might be issued during or 
after the test.  A quick look test report summarizing test results with preliminary conclusions 
could be issued during the test or shortly after the test; it can give management useful 
information to make early decisions.  A formal test report is a document covering test data, 
analysis results, learned lessons, conclusions and suggestions and is typically used as formal 
reference document. 
 
Good archiving and reporting are required when there are long gaps between tests or 
development cycles. 
 
 
 
 
 
Thermal and Environmental Analysis Section 
November 15, 2007 
ESCG-4470-07-TEAN-DOC-0173 
p. 7 
 
  
References: 
 
1. An email message sent from John Lewis/JSC on 10/24/07. 
 
 
Appendix: Examples of Analysis Supports to ELS Tests 
 
Development of 2nd generation Human Metabolic System (HMS) – Analysis work involved all 
three phases.  HMS pre-test analysis included analysis of a human metabolic output model at 
various metabolic activity levels, trade study of various methods of oxygen removal 
technologies, fundamental analyses of sensible heat and latent heat addition, as well as 
mass and heat balance calculations.  Analyses conducted during test and post test included 
test data analysis and hardware modification analyses. 
 
Development of a two-stage mechanical compressor and development of an integrated 
Carbon Dioxide Removal Assembly (CDRA) and CO2 recovery system model – A team 
consisting of JSC, MSFC, Southwest Research Institute (SwRI) and Hamilton Sundstrand 
(HS) personnel were involved in the development of CO2 recovery technology and a two-
stage mechanical CO2 compressor.  Pre-test analyses included development of a rigorous 
CDRA model (by Lockheed Martin) and a rigorous compressor model (by SwRI).  Pre-test 
simulations of the test system were performed using the models.  Analysis support was 
performed in supporting numerous integrated CDRA and CO2 recovery tests.  Post test 
analyses verified the CDRA CO2 removal model, CO2 recovery model and the mechanical 
CO2 compressor model. 
 
CO2 And Moisture Removal Amine Swing-bed (CAMRAS) facility setup support – Analyses 
were provided in calculating cooling/heating requirements to maintain the Air Revitalization 
Technology Evaluation Facility (ARTEF) at a desirable temperature range.  Analyses also 
provided sensible and latent loads to ARTEF in simulating four/six crew metabolic loads in 
ARTEF at various metabolic activity levels.  Analyses were performed in pre-test support. 
 
90-day Lunar-Mars Life Support Test Project (LMLSTP) – Analysis was performed to 
support testing of closed-loop ECLSS technologies for an integrated crew cabin, plant 
growth chamber, airlock, and solid waste incineration unit.  An integrated ECLSS 
system model was developed and verified with the test data.  The integrated model 
simulated and predicted the performance of an integrated air revitalization system, 
water recovery system, plant growth chamber, human waste incineration system, and 
crew in the 90-day closed ECLSS system test.  Analyses provided included pre-test 
modeling, test data analysis during test and post test analysis.   
November 15, 2007 
ESCG-4470-07-TEAN-DOC-0173 
p. 8 
 
  
ELECTRONIC DISTRIBUTION: 
 
M. S. Anderson /NASA 
M. K. Ewert /NASA 
B. C.  Conger /ESCG 
J.  L.  Cox /ESCG 
K. E.  Lange /ESCG 
F. F.  Jeng /ESCG 
Task Order File Original + Copy 
 


Test Analysis Guidelines

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server