LabNews 08/05/2005 — PDF (650KB)
Several
Sandia
projects
have
been
instrumental
in
helping
NASA
with
its
Space
Shuttle
Discovery’s
return-to-flight
mission
(STS-114).
Discovery
has
been
in
orbit
on
its
two-week
mission
since
its
successful
launch
last
week
(July
26),
temporarily
ending
the
hiatus
on
space
shuttle
flights
caused
by
the
Columbia
disaster
in
2003.
Sandia’s projects range from creating an orbiter inspection sensor, to analyzing sensors placed on the orbiter’s wing leading edges, to providing peer review reports. Sandia also studied the vibrations caused during the rollout of the space vehicle and developed an ultrasonic nondestructive inspection method.
Sandia was instrumental in analyzing the cause of the accident that destroyed the Columbia during reentry on Feb. 1, 2003. A Labs-wide team effort helped confirm that the accident was caused by foam from the external tank that impacted the wing leading edge on takeoff (Lab News, Sept. 5, 2003).
Orbiter inspection sensor
Sandia provided the primary Thermal Protection System (TPS) inspection system to NASA for the mission of the space shuttle Discovery, successfully launched on July 26 after a long hiatus due to the 2003 Columbia disaster.
Bob Habbit and Bob Nellums (both 2624) led a collaborative effort of nearly 120 Sandians in creating the sensor. Many of the team members worked nights and weekends to meet NASA’s critical need to return to flight ASAP in support of the International Space Station.
Using 3-D imaging, the sensor inspected the orbiter for critical damage to alert astronauts if further investigations are needed to repair the damage. The crew used the orbiter’s robotic arm to scan the front edge of both wings for damage as little as a 0.02-inch crack.
The Sandia-patented 3-D technology uses a modulated laser illuminator coupled with a modulated receiver to image and spatially locate each point in the scene. The intensity data is used to detect damage and the geometric data to assess the damage criticality.
The sensor data was relayed back to the Mission Control Center at Johnson Space Center in Houston. A team of more than 20 Sandians working in the Mission Control Center processed and reviewed the data. The processed data were provided to the NASA Mission Management Team. The Mission Management Team used the Sandia data as well as other data to determine if it is safe for the Orbiter to re-enter.
Bob Habbit said he is proud to be part of the mission. “It’s exciting to be a contributor to the space program,” he says. “This is truly Sandia providing a service to the nation.”
Inspection hardware
NASA funded a Sandia team to develop an ultrasonic nondestructive inspection method (hardware, techniques, and standards) that led to a scientifically rigorous pre-flight shuttle certification process. The team investigated and proposed ways to improve nondestructive inspection methods for certifying the flightworthiness of orbiter wing leading edges (Lab News, March 19, 2004).
The
team,
led
by
Dennis
Roach
and
Phil
Walkington
(both
6252),
initially
evaluated
and
refined
their
inspection
methods
and
hardware
using
carbon-composite
samples
with
known
defects
created
by
the
Sandia
team.
Later,
as
part
of
the
selection
process,
a
NASA
engineer
hand-carried
orbiter
wing
samples
to
all
the
labs
involved
in
the
project
and
asked
that
each
lab
try
to
find
defects
known
only
to
NASA
scientists.
The team developed the revised inspection and certification protocols, and the ultrasonic scanning system was integrated into NASA’s Shuttle Orbiter Processing Facility at Kennedy Space Center to monitor the health of the shuttle after each orbiter flight.
Sandia produced an in-situ ultrasonic inspection method while NASA Langley developed the eddy current and thermographic techniques. These groups were the primary players on the NASA In-Situ NDI Team. The NASA In-Situ NDI Team consisted of members from all of the NASA facilities and was assembled to guide NASA as it moves to increased use of advanced nondestructive testing techniques to closely monitor the health of the space shuttle.
In 10 months the Sandia team developed and assembled customized hardware to produce an ultrasonic scanner system that can meet the shuttle wing inspection requirements. Optimum combinations of custom ultrasonic probes and data analysis were merged with the inspection procedures needed to properly survey the heat shield panels. System features were introduced to minimize the potential for human factors errors in identifying and locating the flaws. A validation process, including blind inspections monitored by NASA officials, demonstrated the ability of these inspection systems to meet the accuracy, sensitivity, and reliability requirements.
Team members are Phil, Dennis, Kirk Rackow, and Dick Perry (all 6252). The NASA project manager was Ajay Koshti at Johnson Space Center.
Sensor tests
David Crawford (9116) and Kenneth Gwinn (9126) analyzed tests conducted on sensors that were placed on the leading edge of the orbiter’s wings (Lab News, Feb. 4).
The
project
focused
on
validating
forcing
functions
for
NASA’s
Impact
Penetration
Sensing
system
(IPSS)
Wing
Model.
The
model
was
developed
at
Boeing
to
predict
the
accelerometer
data
collected
during
ascent
and
micrometeoroid/orbiting
debris
(MMOD)
impacts
on
shuttle
wing
and
spar
leading-edge
materials.
The
sensors
developed
by
NASA
are
significant
to
the
return-to-flight
effort.
The
addition
of
the
sensors
to
the
leading
edge
was
in
response
to
one
of
the
prime
objectives
identified
by
the
Columbia
Accident
Investigation
Board.
David and Kenneth evaluated test data and were comparing it with structural models of the shuttle and assessing what the signal levels mean. Tasks included defining the forcing functions for foam, pieces of ice (from takeoff), ablator particles, and micrometeorites. Full-scale tests of foam, ice, ablator, metal particle, and MMOD impacts were performed at Southwest Research Institute in San Antonio, Texas. Tests on fiberglass and RCC (reinforced carbon composite) wing panels were conducted at the White Sands Test Facility.
Peer reviews
Members of Sandia’s Aerosciences and Compressible Fluid Mechanics Dept. 9115 contributed two peer reviews on NASA’s development of computational tools that are being used to support rapid damage assessments should anything occur during future flights.
Basil
Hassan,
manager
of
Dept.
9115,
serves
as
an
external
member
of
NASA’s
Engineering
and
Safety
Center’s
(NESC)
Flight
Sciences
“Super
Problem
Resolution
Team”
(SPRT).
NESC
was
formed
shortly
after
the
Columbia
accident
to
oversee
any
safety
issues
that
might
arise
in
any
of
NASA’s
flight
programs.
Basil
and
two
staff
members,
David
Kuntz
and
Jeffrey
Payne
(both
9115),
participated
in
several
peer
reviews
as
NASA
prepared
for
return-to-flight.
They
were
also
part
of
a
larger
group
of
Sandia
management
and
staff
who
were
active
in
the
post-accident
investigation.
Two recent reviews focused on Debris Transport Review and Boundary Layer Transition Review.
Debris Transport Review focused on NASA’s development of tools to model external tank foam or ice buildup that may come off during ascent and potentially hit the orbiter. While several efforts have been under way to minimize foam and ice release from the external tank, NASA wants to predict if the released debris will impact the orbiter in critical areas. NASA has used these tools to redesign parts of the external tank so that catastrophes like the Columbia accident will not re-occur.
Boundary Layer Transition Review focused on reentry. During the reentry trajectory the airflow around the orbiter will transition from laminar to turbulent flow. When the flow becomes turbulent, the heat transfer to the vehicle can increase two to four times above the laminar heating. While the thermal protection system (TPS) is designed to absorb the heating rates generated by turbulent flow, damage to the TPS could cause the flow to become turbulent at a higher altitude. The result of this damage could mean higher localized heating rates on the TPS, and ultimately higher than normal integrated heating on the orbiter during reentry.
“Sandia’s participation on these two reviews teams is a one part of a larger effort of the Labs supporting a variety of return-to-flight activities,” Basil says. “We expect additional requests to tap into many of Sandia’s unique capabilities.”
Basil, David, and Jeffrey also reviewed NASA’s rapid damage assessment tools to help the agency ensure that the codes were being applied appropriately and that the relevant assumptions in the codes were not being violated. In general, these tools make use of data from computer codes that model the fundamental physics, wind tunnel test data, and data from previous shuttle flights. Should it be found in orbit that damage occurred during the ascent stage, NASA engineers will use these tools to decide whether the orbiter can safely return or if some in-orbit repair is needed.
Shuttle rollout
To
help
understand
the
fatigue
caused
by
vibrations
during
the
rollout,
NASA
contacted
Sandia
to
assist
with
a
series
of
tests
(Lab
News,
April
1).
Sandia
helped
NASA
design
the
test
and
instrumentation
to
measure
the
dynamic
vibration
environment
of
the
rollout.
Sandia
also
provided
additional
support
to
NASA
by
computing
the
input
forces
that
the
crawler
applies
to
the
MLP,
which
are
being
used
by
Boeing
and
NASA
to
compute
the
fatigue
life
for
critical
shuttle
components.
Tom Carne (9124) assisted with a series of tests beginning in November 2003 to develop the data necessary to understand the environment and the response of the space shuttle vehicle during rollout.
Moving the shuttle from the Vehicle Assembly Building at Kennedy Space Center in Florida to the launch normally takes five to six hours at 0.9 mph. As the equipment ages, emphasis is being given to understanding how the rollout may fatigue the orbiter.
The
analyses
showed
that
modifying
the
speed
of
the
crawler
would
reduce
the
fatigue
stresses
of
the
critical
shuttle
components.
Merely
reducing
the
speed
from
0.9
mph
to
0.8
mph
would
significantly
reduce
the
vibrations
in
the
shuttle
by
shifting
the
engagement
frequency
of
the
crawler
treads.
The
shuttle’s
vibration
response
can
be
much
reduced
when
the
driving
frequencies
are
shifted
away
from
its
own
resonant
natural
frequencies.
--
Michael
Padilla
John
German
also
contributed
to
this
story.
Two
Sandia
technologies,
both
based
on
microChemLab,
are
expected
to
soon
be
checking
for
toxins
and
harmful
bacteria
in
the
nation’s
water
supplies.
The microChemLab, officially called µChemLab, is a hand-held “chemistry laboratory.” The liquid prototype was designed and built at Sandia/California, while the µChemLab that takes measurements in the gas phase was developed at Sandia/New Mexico.
The µChemLab, electronics, and sample collector weigh about 25 pounds and fit into a box the size of a small suitcase. The only external parts of the two sensor technologies are water collectors. The units are completely portable.
“Our
goal
is
to
place
these
sensors
within
utility
water
systems
and
use
them
to
quickly
determine
if
the
water
contains
harmful
bacteria
and
toxins,”
says
Wayne
Einfeld
(6245),
who
heads
the
Sensor
Development
Focus
Area
within
Sandia’s
Water
Initiative
(www.sandia.gov/water).
“This
on-site
monitoring
approach
would
replace
current
utility
monitoring
systems
that
require
water
samples
to
be
sent
to
laboratories
for
analysis,
which
sometimes
takes
days
for
results.”
The
United
States
has
more
than
300,000
public
supply
water
wells,
55,000
utilities,
120,000
transient
systems
at
rest
stops
or
campgrounds,
and
tens
of
millions
of
hydrants.
Up
until
now,
real-time,
remote
water
quality
monitoring
for
toxins
has
been
very
limited.
The
liquid
µChemLab
is
currently
being
tested
at
the
Contra
Costa
(Calif.)
Water
Utility,
says
Jay
West
(8324),
California
principal
investigator.
Specifically,
the
team
is
testing
to
determine
the
steps
necessary
to
identify
toxins
in
drinking
water,
as
well
as
expanding
its
capabilities
as
an
autonomous
monitor.
The
device
is
presently
collecting
and
analyzing
a
water
sample
every
30
minutes
and
reporting
results
via
a
real-time
data
link
to
researchers
at
Sandia.
CRADA
partners
have
long
experience
Sandia’s cooperative research and development agreement (CRADA) partners in the California endeavor are CH2M Hill, a leading US engineering firm, and Tenix, an Australian engineering services company. CH2M Hill is a global engineering and construction management firm with particular expertise in sewer and wastewater treatment design. Tenix is an engineering services and technology company with more than 30 years’ experience in water supply, sewerage and drainage infrastrucure, and defense.
The California µChemLab identifies proteins by separating samples into distinct bands in seconds to minutes. Separations occur in channels as narrow as a human hair coiled onto a glass chip about the size of a nickel.
Curt Mowry (1764), principal investigator for the New Mexico project, says his team is seeking to develop a device that detects trihalomethanes, undesirable byproducts of the chlorination process used to control the bacterial content of water. Trihalomethanes, which form naturally when surface water is treated with chlorine, are highly carcinogenic and can have adverse liver and kidney effects. The New Mexico project is funded through Laboratory Directed Research and Development (LDRD) resources allocated through Sandia’s Water Initiative.
“The EPA has regulations for water utilities to monitor for trihalomethanes on a regular schedule,” Curt says. “Currently they have to collect samples and send them to labs for analysis. They get numbers back a few days later. This is a scary thing for us as consumers. The way it’s done now, chemists might have measured high levels and there is chance someone has already consumed the water before the results return. Using the µChemLab will provide a way to bring the labs to the site and get results in a more timely manner.”
The
µChemLab
system
is
expected
to
help
water
utilities
control
the
formation
of
trihalomethanes
by
functioning
as
a
component
of
a
process
control
loop.
New
Mexico’s
portable
unit
analyzes
a
sample
of
water
by
bubbling
air
through
it
and
collecting
trihalomethanes
from
that
air.
The
collector
is
heated,
sending
the
trihalomethanes
through
a
separation
channel
and
then
over
a
surface
acoustic
wave
(SAW)
detector.
“The collector and the separation phase can be purchased off the shelf, but the SAW detector is at the heart of the microChemLab,” Curt says. “The goal by the end of summer is to replace the commercial separation column with a Sandia microfabricated column made using MEMS fabrication technology to reduce the power needed and increase performance.”
Commercial collectors are about four to five inches in diameter. Microfabricated collectors will be half a square inch. They are in development and need further tuning for trihalomethanes.
The Sandia/New Mexico microChemLab uses similar concepts to the California one — collect, separate, and detect. The main difference is at the “front end” of the device, where different capabilities are needed to be able to extract gases such as trihalomethanes from the water.
“Both systems will speed the analytical process and give the utility operator better information in a shorter time period,” Wayne says. “In addition to routine water quality monitoring, both are expected to be part of early warning systems that can alert utility operators to intentional contamination events that might occur at vulnerable locations downstream from treatment plans.”
And finally, he says, “In both of these projects Sandia has successfully leveraged MEMS-based core technologies nurtured by various DOE programs into the water security applications area.” -- Chris Burroughs
By Nancy Garcia
Among
the
hardest
and
most
challenging
problems
facing
the
national
labs
are
the
issues
of
energy
security
and
environmental
quality.
Ground
transportation
consumes
the
largest
share
of
oil
in
the
US,
and
to
meet
the
demand,
oil
imports
have
reached
the
highest
levels
in
history.
To help reduce this dependence on foreign oil, promising new combustion strategies for efficient, clean engines are being explored at the Combustion Research Facility (CRF) in Center 8300 through a $6 million engine-combustion research program. The work is funded 90 percent by DOE’s Office of
FreedomCAR and Vehicle Technologies (OFCVT) and 10 percent by private industry.
“Our research is providing the science base needed by industry to develop higher efficiency, emission-compliant engines,” says Dennis Siebers, who manages Engine Combustion Dept. 8362. “There’s a significant potential for improving the fuel efficiency of engines while simultaneously reducing their pollutant emissions.” Moreover, he added, “Such improvements in fuel efficiency will contribute to a direct reduction in greenhouse gas [CO2] emissions.”
To achieve these goals, the engine research at the CRF is focusing on new combustion strategies that will allow high-efficiency, clean engines. Also included is research on fuels for these engines from both traditional and alternative sources. The new combustion strategies fall into a class being referred to as low-temperature combustion (LTC). In simple terms, LTC is combustion under conditions that are fuel-lean enough (or sufficiently dilute with recirculated exhaust gas) to avoid soot formation and the high combustion temperatures that lead to significant nitrogen oxide (NOx) formation.
Unique capabilities, new strategies
Sandia has been conducting engine-combustion research in collaboration with industry for more than 25 years. The research has led to a suite of advanced optical-diagnostic tools for analyzing the combustion in an operating engine, and to the advancement of predictive computer models. This research has impacted industry’s design and development process, contributing significantly to the efficiency and emissions improvements of engines that are currently in production. As Dennis summarizes, “We bring capabilities that are unique in the world for helping industry develop new combustion strategies for high-efficiency engines.”
Patrick Flynn, former vice president of research at the country’s largest diesel engine manufacturer, Cummins, Inc., comments: “I feel that these tools provided by the CRF will play an ever-increasing role in engine design evolution.” The application of these tools and the expertise of CRF researchers, three of whom have been elected fellows of the Society of Automotive Engineers, are central to the new research efforts on LTC.
The low-temperature combustion research at the CRF is being conducted as part of a broader DOE program. Because of its established reputation, Sandia was recently tasked by DOE OFCVT to create and lead a memorandum of understanding (MOU) surrounding the overall research efforts. The MOU involves five national labs (Sandia, Lawrence Livermore, Los Alamos, Oak Ridge, and Argonne) and 10 engine manufacturers (Cummins, General Motors, Ford, DaimlerChrysler, Caterpillar, Detroit Diesel, International Truck, Mack/Volvo, John Deere, and General Electric). The research is conducted in collaboration with several universities (Stanford, MIT, University of California at Berkeley, University of Wisconsin, University of Michigan, Pennsylvania State University, University of Illinois, and Wayne State University).
50 percent better mpg by 2012?
The
DOE
low-temperature
combustion
program
covered
by
the
MOU
targets
a
50
percent
improvement
in
fuel
efficiency
in
the
light-duty
sector
(automobiles,
SUVs,
and
pickups)
by
2012
and
a
30
percent
improvement
in
heavy-duty
trucks
by
2013.
With
complete
market
penetration,
these
efficiency
improvements
would
reduce
US
oil
use
by
4
million
barrels
per
day
or
oil
imports
by
one-third
from
their
present
levels.
The
improvements
would
also
translate
directly
to
a
9
percent
reduction
in
the
total
US
greenhouse
gas
emissions.
Even
greater
reductions
in
oil
use
are
possible
through
further
improvements
in
engine
efficiency
and
through
the
use
of
these
high-efficiency
engines
in
hybrid-electric
vehicles.
“Two factors have made the low-temperature combustion techniques practical to consider now: the advent of onboard computers and electronic fuel injection,” Dennis says. “These allow for real-time control of potentially unstable combustion conditions that can arise with the advanced strategies. It’s possible that cycle-by-cycle, or even cylinder-by-cylinder control will be necessary to implement low-temperature combustion,” he says. “This dictates the need for a fairly comprehensive understanding of the in-cylinder processes.” As a national laboratory tackling tough technical problems, Sandia is playing a vital role.
Reducing emissions a challenge
In addition to reducing fuel consumption, the new LTC engine concepts are being driven by the need to reduce pollutant emissions. Stringent new emission regulations call for a factor of 10 reduction in soot and NOx by 2010. “Those regulations are really challenging,” notes John Dec (8362), who is working on clean combustion concepts for high efficiency engines in one of Sandia’s eight engine labs, adding that meeting the current emission regulations on high-efficiency diesel engines “took 20 years and a lot of work.”
Fairly good aftertreatment options exist for controlling soot from high efficiency diesel engines, but NOx aftertreatment for diesel exhaust is difficult. This is because the exhaust contains excess oxygen, which makes conventional automotive catalytic converters ineffective. Special “lean-NOx” catalysts have been demonstrated, but they have reliability problems and are expensive, sometimes costing as much as the engine itself.
“You’d like to take care of the NOx problem at its source,” John said, “and that means lowering the combustion temperature.”
To accomplish this, John’s research centers on a concept that combines some of the advantages of gasoline engines (which have premixed fuel and air with no soot emissions) and diesel engines (which have high efficiencies due to their high compression ratio and lack of throttling losses). The concept, homogeneous charge compression ignition (HCCI), has been known for some time but the operating range was very limited, and the technical challenges could not be overcome without modern computerized controls.
John’s research is conducted in both a conventional, “all-metal” engine used for performance and emissions measurements, and a second engine with quartz windows to allow laser diagnostics to be used to probe the combustion chamber, illuminating various aspects of the in-cylinder processes.
Although much work is still required to perfect the concept, it is efficient and has low emissions. “Market penetration,” John says, “could take several years, but the potential fuel savings are tremendous.”
An approach that has the potential for more rapid market penetration is being explored by Paul Miles (8362). Paul is studying modifications to standard diesel combustion that result in low-temperature combustion in automotive-size diesel engines, greatly reducing NOx and particulate emissions.
Paul is investigating fuel spray and fuel-air mixing to understand in-cylinder geometries that enhance the combustion completeness, and to provide data for the development of computational tools for engine design by colleagues at Los Alamos National Laboratory and the University of Wisconsin. “The fuel injection, mixing, and combustion processes in engines are so complicated, and the physical processes are so convoluted,” Paul says, “you’re not going to design and optimize advanced combustion systems for these engines other than by computer.”
Fuels a focus too
Another part of the research effort is on fuels, especially fuels that enable the full potential of low-temperature combustion. One aspect to be sorted out is what the most appropriate fuel might be. Since gasoline and diesel engines have been around some 100 years, those fuels are now highly optimized for current engine designs, but there is no reason to expect they are ideal for low-temperature combustion.
Another aspect is how to accommodate the changing nature of the feedstocks for fuels. In the future, bio-derived fuels and fuels from heavier crude oils, oil sands, and potentially shale oil will play an increasing role.
Fuels are a specialty in the engine lab of Chuck Mueller (8362), who is studying fuel effects on low-temperature combustion strategies. Chuck began studying oxygenates in 1997 as a prospective way to reduce soot, and more recently to see if they can enable low-temperature combustion technologies. Experiments in his lab have already shown a drop of two orders of magnitude in pollutant emissions with no loss of fuel economy. “It’s really pretty revolutionary,” he says. “You’d think all the breakthroughs would have been made by now, but this is a rich field.”
“There are still many hurdles to overcome in order to make combustion efficient, clean and practical,” he says, “and emissions restrictions typically involve trade-offs between cost and performance. The concepts themselves may be relatively simple,” Chuck adds, “but implementing them will be challenging.” -- Nancy Garcia
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