The Quarterly Publication of the Numerical 

Aerospace Simulation Systems Division

NAS researchers are developing atomic

scale transistors to enable future

microelectronics. Page 10

IPG Infrastructure Nears Completion — 18

NREN Drives Global Deployment of Multicast Protocol — 7

CART3D: A New Generation of Grids — 4

CFD Supports Wind Turbine Research — 14
Vol. 1, No. 3 • Summer 2000

Executive Editors: Bill Feiereisen

John Ziebarth

Editor: Nicholas A. Veronico

Writers: Holly A. Amundson

Toshishige Yamada

Graphic Designer: Sue Kim

Illustrator: Gail Felchle

Photographer: Michael Boswell

Contact the Editor:

Nicholas A. Veronico

Gridpoints

M/S 258-6

Moffett Field, CA 

94035-1000

Tel. (650) 604-3046

Fax (650) 604-4377

nveronico@mail.arc.nasa.gov

Gridpoints is a quarterly publication of the NAS

Systems Division at NASA Ames Research

Center. The division’s staff includes government

employees and contractors from Cray Research

Inc., Advanced Management Technology Inc.,

Computer Sciences Corp., Eloret, Raytheon

Company, and SGI.

Gridpoints acknowledges that some words, model

names and designations mentioned herein are the

property of the trademark holder. Gridpoints uses

them for identification purposes only.

The staff of Gridpoints would like to thank the

following people for their assistance in preparing

this publication: Michael Aftosmis, Dick

Anderson, Bill Arasin, Michael Boswell, Samson

Cheung, Bob Ciotti, Jill Dunbar, Earl Duque,

Chris Gong, Bryan Green, Jennifer Goudey, T.R.

Govindan, Chris Henze, Tom Hinke, Vee Hirsch,

Amara de Keczer, Tony Keefe, Chris Kleiber, Bob

Kufeld, Dochan Kwak, Eric Langhirt, Tammy

Leal, Bonita McPherson, George Makatura,

Yvonne Malloy, Donovan Mathias, Meyya

Meyappan, Gina Morello, George Myers, Todd

Novak, Jeff Onufer, Marcia Redmond, Scott

Schreck, Ryan Spaulding, Roger Strawn, Valerie

Steele, Ron Sykora, Jim Taft, Leigh Ann Tanner,

Bill Thigpen, Richard Thompson, Ray Turney,

Judith Utley, Rob Van Der Wijngaart, Cliff

Williams, Michael Wilson, Mindy Wilson,

Toshishige Yamada, Jerry Yan, Maurice Yarrow

Visit us on the web at:

http://www.nas.nasa.gov/gridpoints

On The Cover:

Subscribe to Gridpoints

Subscriptions to Gridpoints are complementary.

Please e-mail your name, company name, title,

address, and zip code to:

gridpoints@nas.nasa.gov

Gate

Source Drain

Atomic: < 10 The Smallest Nanoelectronics: Atomic -9 m (top)

Devices with Precise Structures

Transistor miniaturization is reaching its limit. Atomic

scale transistors are being developed to enable future

microelectronics.

Toshishige Yamada

CFD Supports Wind

Turbine Research

NAS provides the National Renewable Energy

Laboratory with computational resources to help

improve next-generation wind turbine designs.

Holly A. Amundson

The Quarterly Publication of the Numerical

Aerospace Simulation Systems Division

4

18

7

NASA Research and

Education Network Drives

Global Deployment of

Multicast Protocol

Multicast will speed up the Internet by enabling a single data packet to be distributed

to multiple Internet users simultaneously.

Hugh LaMaster and Kenneth Freeman

10

Network B

Router Router

Network A

Router

Router

Rendezvous

Points

Network C

Router

Router

Rendezvous

Points

Rendezvous

Points

CART3D: A New Generation

of Grids

3-D grid software automatically generates

vehicle simulations from complex geometries.

Holly A. Amundson

14

NAS researcher Toshishige Yamada has conducted experiments with atomically precise structures using

a substrate atomic lattice, floating of atoms above the substrate, and chemical bonding of atoms to the

substrate. Yamada’s research will enable future atomic scale devices. See page 10 for the full story.

Infrastructure For NASA’s

Information Power Grid Nears

Completion

More than a dozen components of the IPG are being

readied for roll-out this September.

Nicholas A. Veronico

Features
NAS nanotechnology researcher Deepak Srivastava

chaired the conference “Carbon Nanotubes: Advances

in Cutting Edge Applications and Scalable Production,” in

Miami, Fla., April 10-11. The meeting emphasized advances in commercial applications and the prospects for scalable production of carbon nanotubes. Srivastava also gave an

invited talk on plasticity and hydrogen diffusion on carbon

and boron nitrate nanotubes, and Ames’ experimental nanotechnology researcher Allen Cassel spoke about nanotube

applications in nanoelectronic circuitry and combinatorial

chemical approaches for tuning the production of nanotubes on different substrates. On his return trip, Srivastava

also gave an invited talk, “Nanotechnology of Molecular

Materials, Electronics and Machines: Carbon Nanotubes,”

at the Quantum Theory Project (QTP) seminar, at his alma

mater, University of Florida, Gainesville, on April 12.

Chimera Grid Tools Version 1.3

Now Available

The Chimera Grid Tools (CGT) version 1.3, a package

of programs and scripts used to generate overset grid

www.nas.nasa.gov/gridpoints Gridpoints 1

Many years after winning the Nobel Prize for coinventing the transistor, Walter Brattain said,“The only regret I have about the transistor is

its use in rock and roll.” On page 10, NAS researcher

Toshishige Yamada details his patent-pending research into

atomic chain electronics – a new, nanotechnology-based

approach to device miniaturization that will revolutionize

the future of electronics. Reflecting on Brattain’s comments,

I wonder what Yamada will say about his invention 30

years from now?

Development of NASA’s prototype Information Power Grid (IPG) is progressing steadily. In April, the IPG’s first

important milestone to demonstrate data

transfer rates was achieved using data

mining software. To meet the milestone,

the IPG team retrieved data from four

remotely connected sites simultaneously.

The success of our data mining demonstration will allow the NAS team to

move forward in expanding the IPG’s

infrastructure, some of which will be demonstrated this

September. The IPG project is directly related to a part of

the NAS Division’s mission statement: “implementing and

integrating new high performance computing technologies

into useful production systems.” 

The NAS Facility is home to Lomax, a 512-processor SGI

Origin 2800, currently the world’s largest single-image system computer. Lomax supports the IPG and a variety of

NASA research efforts. NAS scientists are using the software program CART3D on Lomax to develop “virtual

flight” through computational fluid dynamics. CART3D

generates grids to calculate flow fields around an air or

space vehicle. Recently, NAS researchers studied four

Space Shuttle nose configurations, and the results will be

“flown” in Ames Research Center’s Vertical Motion Simulator this fall.

The NAS Systems Division supports numerous NASA

enterprises with high performance computing resources,

and conducts research that will have far reaching impacts

on the NASA mission, the scientific community, and eventually, on the public. For example, scientists from the

National Renewable Energy Laboratory are working to improve wind turbine designs

using wind tunnel testing and

NAS computational modeling

resources. Within the next 20

years, this clean source of power

could provide more than 10 percent of the world’s electricity. 

In addition, the NASA Research and Education Network

(NREN) is improving the

Internet with the global adoption of the Multicast Protocol.

Multicasting will allow a single

data packet to be replicated and

delivered to multiple users

simultaneously, rather than

each packet being delivered

serially. Through improved Internet speed, we will all benefit from multicasting’s applications. 

As always, I welcome your feedback.

Bill Feiereisen

wfeiereisen@mail.arc.nasa.gov

From The Division Chief

NAS Mission

To lead the country in the research and development of

high performance computing

for NASA Programs and

Missions by being the first to

develop, implement, and integrate new high performance

computing technologies into

useful production systems.

To provide NASA and its customers with the most powerful, reliable, and usable production high performance

computing systems in the

country.

NAS Researchers Lecture on

Carbon Nanotubes

News From NAS

gp
systems for complex viscous computational fluid dynamics

(CFD) problems, has been released. CGT’s new tools include: surface and volume grid generation programs; grid

manipulation, smoothing, and projection programs; a modular, general-purpose scripting system which can help build an

entire grid system and produce Overflow flow solver inputs;

and a graphical user interface known as Overgrid – used

for generating grid systems. This version will significantly

reduce CFD cycle times for a wide range of applications. 

Version 1.3 is the final release of the software that has been

funded by the DoD Common High Performance Computing Software Initiative CFD-4 project. Work is continuing

toward a fully automated grid generation process with the

incorporation of an AI-based surface and volume grid generation program, as well as the new, automated version of

the overset connectivity software, Pegasus 5. CGT’s authors

are William Chan (NASA Ames), Stuart Rogers (NAS),

Steve Nash (NAS), and Pieter Buning (NASA Langley).

News From NAS

INthe ongoing quest to solve challenges with creating

nanoscale molecular electronic devices, NAS researchers are working to design nanoscale DNA diodes,

transistors, and simple logic gates. The team is using a

unique approach that provides a mechanism for self-assembly in future molecular-scale electronics, based on state-ofthe-art nanotechnology and molecular electronics principles. The research, conducted by Jie Han in the NAS

Systems Division, is funded by a two year, $80,000 grant

from the Ames Director’s Discretionary Fund. 

Much of the recent progress in computer technology is

based on creating smaller and smaller transistors for logic

devices and integrated circuits. Rapid advances have been

made in fabricating and demonstrating individual electronic wires and devices. However, these new technologies still

face problems, including the requirement for devices to

self-assemble. 

Recent studies have shown that DNA has all the components needed to build an electronic device as well as the

self-assembly characteristics needed to form complex electronic circuits. Even more exciting to the research team,

DNA has the unique feature of self-replication. The work

will focus on theoretical and computational proofs-of-concept, and experimental demonstration will be considered

using nanotechnology and biology facilities at Ames. 

Han is collaborating with the nanotube biosensor experimental team at Ames and Nanogen, Inc., based in San Diego.

Ascientific code used to simulate protein folding sequences now performs 36 times faster than was previously

possible, thanks to code optimizations made by NAS

Systems Division researcher James Taft. The code, called

Ames Researchers Designing

DNA Electronic Devices

SGI Special: Lights, Camera, Action!

An SGI film crew producing a corporate documentary

on the company’s supercomputers and their uses employed the NAS Systems Division as a backdrop. Ames

Center Director Henry McDonald and NAS Division

Chief Bill Feiereisen were featured guests in the production. Feiereisen, above left in the visualization lab,

discussed science conducted on SGI machines at NAS.

Taping on June 13 lasted the entire day. 

(Michael Boswell photo)

2 Gridpoints

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Corrections: In the Spring 2000 issue on

page 10, the caption for Figure 3 should

have read: “This image shows the spontaneous attachment of a protein to the

modified messenger RNA that encodes it.

This allows an evolutionary approach to

the discovery of new functional proteins

in the laboratory. Researchers at Harvard

Medical School start by generating trillions of random proteins in a single tube.

Then, they select rare proteins exhibiting

a desired function. This process is a massively parallel analog computation of a

problem not currently solvable by serial digital computational

approaches. Current studies are directed

toward the discovery of functional proteins

in synthetically generated libraries of random-sequence proteins, rather than libraries isolated from biological systems. It

is presumed that the proteins first utilized

by early living organisms were recruited

from such random-sequence libraries, and

that this study will indicate what proportion of such proteins are functional.

(Credit: Glen Cho, Anthony D. Keefe,

Rihe Liu, David S. Wilson, and Jack W.

Szostak) Additionally, Ling-Jen Chiang’s

credit was omitted from the graphic on page 21. 

Protein-folding Code Hums

With NAS Optimization

gp
COSMOS, is a molecular dynamics model used in NASA’s

astrobiology research. 

Taft modified the code to utilize 343 processors on Lomax,

a parallel processor SGI Origin 2800 located at the NAS

Facility. With 512 CPUs, Lomax is currently the largest single-image system in the world. Using a shared-memory parallel programming approach, Taft and COSMOS developer

Andrew Pohorille, acting director of the NASA Computational Astrobiology Institute, have been rebuilding the code

to run 30,000-atom problems on RISC microprocessorbased systems. Historically, many important molecular

dynamics problems of this size have not scaled well on

“clustered” parallel systems. Lomax, with very fast shared

memory, is ideal for such computations. 

“The results of this work can benefit the molecular modeling industry in general because the newly developed numerical techniques are applicable to many popular industry

standard models used by pharmaceutical research companies in the U.S.,” says Taft. 

The two-month optimization effort focused on inserting

the Ames-developed shared memory Multilevel Protocol

(MLP) parallelization technique into the code. The MLP

technique allowed dramatic improvements on the code’s

two most time-consuming routines. The overall speedup

arises from scaling efficiencies in the MLP-based parallel

algorithm, coupled with greater reuse of encached data. 

Members of the Ames Integrated Product Team on

Devices and Nanotechnology – representing the

largest nanotechnology research efforts within the federal

government – received a group achievement award for

“excellence in research and outstanding contributions to the

emerging field of nanotechnology” at the 2000 NASA

Honor Awards ceremony on June 7. 

Project manager Meyya Meyyappan, credits the NAS

Systems Division as “the birthplace” of this work, originating with a small theory group doing computational nanotechnology at the NAS Facility. The team has expanded to

include experimental research in the laboratory. Experiments on growing nanotubes for applications such as cancer

diagnostics attract a steady stream of visitors from the hightech arena, including former House science and technology

committee chair Bob Walker, shown at right, who toured

the “nanotube garden” on June 6.

Among those receiving the group achievement award were

NAS researchers M.P. Anantrim, Bryan Biegel, T.R. Govindan, Jie Han, Cun-Zheng Ning, Deepak Srivastava, Alexei

Svizhenko, and Toshishige Yamada. 

www.nas.nasa.gov/gridpoints

Information & Technology Chairman

Stephen Horn Tours NAS Facility

Rep. Stephen Horn (R-CA, Long Beach), chairman of the

106th Congress’ Subcommittee on Government Management, Information, and Technology toured the NAS Facility

on April 24 before hosting a

hearing at Ames on “Emerging

Technologies: Where is the

Federal Government in the

High Tech Curve?”

Division Chief Bill Feiereisen

briefed the congressman on

NAS’s advances in high performance computing, nanotechnology, and the Information

Power Grid. Horn then toured

the Visualization Lab and was

given a Virtual Mechanosysthesis demonstration by

Chris Henze and Bryan Green

of the NAS data analysis group.

A carbon nanotube and a graphite T-junction were projected

on the Responsive Workbench

and Horn was able to interact with individual carbon

atoms. At the conclusion of his tour, Rep. Horn said, “This

amazing technology presents exciting possibilities for science and technology in the 21st century.” 

— Nicholas A. Veronico

Senior research scientist

Chris Henze (right) briefs

Rep. Stephen Horn on the

use of NAS’s Responsive

Workbench in the NAS Visualization Lab. 

(Nicholas A. Veronico)

Gridpoints 3

Former Pennsylvania Congressman Robert Walker, center,

and Ames Deputy Director of Information Systems Paul

Kutler, left, toured the Visualization Lab and were briefed

on the capabilities of the 512 processor SGI Origin 2800,

Lomax, by Bill Thigpen, NAS’s Engineering Branch chief.

Walker, former chair of the House Science Committee,

was on a fact finding mission at Ames on June 6. The trio

stand inside Lomax’s processor banks in the computer

room at NAS. — Nicholas A. Veronico

Fact Finding Tour of NAS And Ames

NAS’s Nanotechnology Team

Members Recognized

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4 Gridpoints

Researchers Donovan Mathias and Jeff Onufer of

NAS’s computational physics and simulation

group, tested four different nose designs for the

Space Shuttle on the 512-processor SGI Origin 2800,

Lomax, during the weekend of March 25-26. “The goal

of this project was not to find the best-suited nose design

for the orbiter, but to use computational fluid dynamics

to support virtual flight. We are developing a process to

bring virtual flight into the early design phase, so the vehicle can be ‘flown’ before a single piece of metal is cut,” says

Mathias who believes testing a design early in its development will save both time and money. 

For the team’s work on Lomax,

they employed a beta version of

the CART3D (Three-Dimensional

Cartesian Simulation System for

Complex Geometries) software

package to generate the grids

necessary for calculating flow

fields surrounding the orbiter.

Results from the Lomax tests will

be used in the Vertical Motion

Simulator (VMS, see sidebar,

NASA’s Full Motion Simulator,

page 6) at NASA Ames in midSeptember. The VMS will “virtually” fly the Space Shuttle, evaluating flight performance of the

new orbiter designs. 

During 21 hours of computations

on Lomax, the team tested four

configurations – three new redesigns (created by Dave Kinney

from the Systems Analysis Branch

at NASA Ames) plus the Shuttle’s

original nose configuration. “We

were able to study quite a number of the orbiter’s components during our weekend on

Lomax,” says Onufer. Each orbiter redesign took 60 simulations, requiring eight processors per simulation to study the

control surfaces, including the elevons (airfoils used to

control the movement of the shuttle), rudder, and speed

brakes. The team also examined flight conditions of the

vehicle: Mach number, angle of attack, and angle of sideslip. This research was funded by the Information Technology Program. 

Once the orbiter grids were generated, they were uploaded

to Lomax and used to calculate flow solutions using “Tiger,”

CART3D: A New

Generation of Grids

3-D grid software automatically generates vehicle

simulations from complex geometries.

Mesh partitions flow over a Space Shuttle orbiter, with each color representing a set of

equations assigned to different CPUs. Sixteen CPUs were used for this calculation; thus

there are 16 divisions. Partitioning is done automatically on any number of processors.

(Aftosmis)
www.nas.nasa.gov/gridpoints Gridpoints 5

the flow solver module for CART3D. The Tiger code,

developed by John Melton of Ames’ Aeronautical Projects

and Programs Office, models the inviscid flow field

surrounding a vehicle such as the shuttle orbiter. 

Enabling Virtual Flight

Aiming to test the shuttle designs in the VMS, researchers

will merge their flow solutions calculated on Lomax with

VMS’s existing mathematical model, which uses a set of

equations to describe the vehicle’s performance. Merging

the flow data with the simulation model, a pilot can evaluate the performance of the shuttle orbiter redesigns with

high-fidelity simulations. “Ideally, we would like real astronauts to fly the simulation to provide the most useful feedback on the flight performance of the vehicle,” says Mathias. 

Currently, NAS research scientist Michael Aftosmis is working on a scalable flow solver to replace the Tiger code.

Aftosmis’ anticipated flow solver will drastically reduce the

time necessary to compute flow fields by distributing the

mesh generated onto different CPUs. Mesh decomposition

Grid Generation Using CART3D

NAS research scientist Michael Aftosmis, John Melton

from Ames’ aeronautical projects and programs office,

and Marsha Berger, co-director of the Courant Institute

at New York University, released CART3D in 1997,

after five years of development. CART3D is a preliminary

design analysis package created to solve the Euler Equations of Motion with Cartesian grids around complex

vehicles. Aftosmis’ work is funded by NASA’s High

Performance Computing and Communications

(HPCC) Program.

CART3D can import geometry from many different

sources, including most major computer-aided design

(CAD) packages, and computes a complete flow simulation around any complex vehicle. The software

takes the surface definition

of a vehicle and generates a

mesh, or set of grids, necessary to compute the air

flow around it using a flow

solver. “The way CART3D

sees geometry is unique –

parts of a whole can be

moved, and the entire configuration does not have to

be regenerated. The software uses a componentbased approach enabling

the automatic readjustment

of the grids, saving a ton of

time,” Aftosmis says. 

The efficiency of CART3D has increased since it was

first released. “A majority of a researcher’s time was

being consumed in converting CAD geometry into

something that could be used for mesh generation.

CART3D has reduced the execution time of this step,

and the ultimate goal is to put the whole thing in a box,

eliminating the human element,” says Aftosmis.

“CART3D is a very robust software package, and can be

quickly applied to almost any air or space vehicle,” adds

researcher Donovan Mathias. “Grids are essentially generated in a matter of minutes on just about any UNIX

or PC platform using CART3D.” 

The sequence of grids (A through D, below), surrounds

two advanced destroyer-type surface ships. These simulations were generated using CART3D’s flow solver module, which employs a multigrid technique to improve the

efficiency of the simulation. This method utilizes a

sequence of coarse meshes to reduce the calculation time

of the final solution of a detailed, highly refined mesh.

The amount of computational work performed is proportional to the complexity of the mesh – less complex

grids enable rapid computations using solution estimates.

This multigrid technique uses a hierarchical approach –

the coarse solution estimates, (figures A through C), are

used to “drive” the complete solution on the fine mesh

(Figure D). The grids are automatically produced and

distributed over Lomax's processors. In this example, the

finest mesh has 4.5 million grid points while the coarsest has only 4,500. (Aftosmis and Mathias)

A B

C D
6 Gridpoints

enhances the solver’s scalability on parallel

computers like Lomax by explicitly assigning different parts of the problem to the

machine’s processors. An application using

the new solver with the same number of

CPUs will work five to 30 times faster

than the “Tiger” code. “We are really

looking forward to putting this new

solver to work – it will be a great deal

faster than Tiger,” says Onufer. Aftosmis

plans to release the new code to a select

group of government users in mid-June

and apply it to high-speed applications:

“We want to stretch the limits of the new

solver by applying it to complex problems

in all three flight regimes; subsonic, transonic, and supersonic.” 

CART3D’s Future

More than 80 institutions, including the

U.S. government, industry, and academia

currently use CART3D. Mathias, Onufer,

and Aftosmis plan to continue their work

on improving flow calculations for flight

simulations in the future. “I think virtual

flight is a great application of simulation

software. The application stresses CART3D

because it requires a lot of throughput,

but is very doable with machines like

Lomax,” says Aftosmis.

—Holly A. Amundson

Above: The velocity component of the baseline shuttle orbiter as computed on

Lomax. The angle of side-slip is zero degrees, and angle of attack is 12 degrees.

Pink areas represent free stream air at MACH 0.9, while the darker colors correspond to a lower air-stream velocity. The blue area behind the shuttle represents

low velocities. (Onufer, Mathias)

Right: The pressure coefficient used to compute lift and drag is depicted on the baseline

shuttle orbiter. Red represents high pressure

areas, while the darker colors denote low

pressure. (Onufer, Mathias)

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S

pace Shuttle configurations calculated on the NAS

Facility’s Lomax high performance computer will

take flight in Ames Research Center’s Vertical

Motion Simulator in September. Each of the four newly

computed Space Shuttle designs will be flown in the simulator, which is capable of replicating vertical, lateral, and

longitudinal movements as well as roll, pitch, and yaw.

The Vertical Motion Simulator’s size and range of motion are key to producing high fidelity flight simulations.

Housed at the Vertical Motion Flight Simulation

Laboratory in a ten-story building, the simulator’s vertical platform is 70 feet wide and can be elevated nearly 75

feet. On top of the vertical platform sits the interchangeable simulator cab where pilots can explore a

craft’s flight envelope. 

The lab houses five different cabs that can be built up

into a wide variety of helicopter, single-seat

fighter jet, tilt rotor and transport

aircraft, and the Space Shuttle

Orbiter. Each cab can be

configured to the research

needs of various test projects

by changing the seats, flight

controls, and cockpit instrumentation. An image presentation system gives the pilot

a virtual out-the-window

view of the world. 

For further information on the Ames

Aviation Systems Division’s Vertical

Motion Flight Simulation Laboratory, visit:

http://www.simlabs.arc.nasa.gov/vms/vms.html.

NASA’s Full Motion Simulator

VMS/Neesham Wallace, Jennifer Goudey
www.nas.nasa.gov/gridpoints Gridpoints 7

S

ince 1998, the NASA Research and Education Network (NREN) – a component of the NAS Systems

Division, has been a leader in the global deployment

of new multicast routing and forwarding protocols used for

sending information across the Internet. Protocol Independent Multicast–Sparse Mode (PIM-SM), Multicast Source

Discovery Protocol (MSDP), and Multicast Border Gateway Protocol (MBGP) are now being adopted worldwide as

the standard protocols for multicast data transfer. Multicast will improve the Internet’s efficiency, and expand networking technology to

allow scientists and researchers to collaborate

while conducting experiments from remote

locations. In the future, commercialization of

multicast technology will benefit society as a

whole, enabling advances in aerospace research,

astrobiology, and other Earth sciences, as well

as telemedicine.

How Does Multicasting Work?

Within the Internet, packets (pieces of data) are

usually sent one at a time. This method, called

“unicasting,” is a simple mechanism for one-toone communication. However, for one-tomany communication, unicasting can create

extreme network congestion. With multicast,

packets are simultaneously transmitted to multiple sites at the same time. As a result, multicasting conserves bandwidth, reducing the

inherent bottlenecks created by one-to-many

transmissions. During multicast, only one copy

of the data is transmitted while network routers replicate

the packets when needed. As a result, on both the sending

and receiving side of the transmission, network bandwidth

is conserved.

Multicasting is similar to broadcasting radio signals; like a

radio signal, multicast packets originate from a single site.

Anyone with the correct equipment can receive the signal,

NASA Research and

Education Network Drives

Global Deployment of

Multicast Protocol

Multicast will speed up the Internet by enabling a single data

packet to be distributed to multiple Internet users simultaneously.

By Hugh LaMaster and Kenneth Freeman

Source

H-3

Router Router

Network A Network B

10 Mbps

Router

H-2

H-1

Router Router

Router

Figure 1. If the source computer is multicasting data at 10 Megabits per

second (Mbps), 10 Mbps will be transmitted between Network A and Network

B, reaching Host H-1 and Host H-2 simultaneously. Without multicast, 20

Mbps of data would be required to transmit data to Host H-1 and Host H-2,

doubling the transmitted data time. (LaMaster and Freeman)
8 Gridpoints

while radio signals pass by anyone who does not want to receive the signal, or does not have

the right equipment. Similarly,

multicast is “broadcast” to the

network but is only received by

those interested in the data. 

Evolution of Global 

IP Multicast

With the explosive growth of the

Internet, networks are struggling

to keep up with the increasing

demand of millions of new users.

In fact, the World Wide Web is

often referred to as the “World

Wide Wait.” To reduce the amount of repetitive data transmissions, global IP (Internet Protocol) multicast technology

allows a single packet stream to be distributed across the

Internet simultaneously to any number of recipients. Multicast is often the only way to simultaneously distribute realtime data to numerous recipients efficiently. It also allows a

data stream to be replicated at intermediate routers so that

any link only receives a single copy, regardless of how many

downstream recipients have requested the information.

Ames Research Center has been a focal point of IP multicast deployment since the early days of MBone, the multicast backbone. Global IP multicast routing, originally

done via the distance vector multicast routing protocol

(DVMRP), was the basis for the MBone. One of the first

successes in using multicast was NASA’s Space Bridge to

Russia in 1996, where multiple remote sites were fed information simultaneously.

More recently, NREN has deployed a number of new networking protocols. Collaborating with the Ames Gateway

Facility (Ames Research Center’s data, video, and telecommunications relay point), Cisco Systems, and Sprint’s research network (Sprint-ICM), the first Multicast Internet

eXchange (MIX) was created; the first multi-network

deployment of the Multicast Border Gateway Protocol

(MBGP – a routing protocol that replaces DVMRP for

inter-domain routing) was achieved; and the first multidomain global deployment of the Protocol Independent

Multicast (PIM – a forwarding protocol) was accomplished.

In July 1998, NREN began deploying the Multicast Border

Gateway Protocol (MBGP). Initial sites included NREN,

Sprint-ICM, and a transit-AS (Autonomous System). By

fall 1998, connections to the Department of Energy’s Energy Sciences Network (ESNET), the Defense Research and

Engineering Network (DREN), as well as Internet service

providers Verio, Exodus, and AboveNet, had been added.

During this time, NREN began “peering” with vBNS

(National Science Foundation and MCI’s very highspeed

Backbone Network Service) in Chicago. When Internet2’s

Abilene Research Network joined, all of the federal government’s Next Generation Internet networks had

adopted MBGP.

Multicast Source Discovery Protocol Deployment

Throughout the Mbone and early MBGP deployment,

dense-mode protocols were used that can sometimes flood

unnecessary data across wide area network (WAN) links.

Using dense-mode, there was no way that very high bandwidth sources exceeding 10 Megabits per second (Mbps)

could be supported across typical WAN links.

Beginning in the fall of 1998, NREN initiated testing of a

new protocol, Multicast Source Discovery Protocol

(MSDP), allowing the use of sparse-mode protocols globally. Sparse-mode enables multicast to be used without specific bandwidth limitations, and supports very high bandwidth data streams.

In spring 1999, driven by the requirement to support the

Virtual Collaborative Clinic – an Internet-based telemedicine demonstration – NREN coordinated the deployment

of MSDP and PIM-SM with the Internet2/Abilene network, the Corporation for Education Network Initiatives

in California’s CalREN-2 network, as well as Stanford

University and the University of California at Santa Cruz.

The deployment of PIM-SM and MSDP enabled data

NREN

PIM-SM

AboveNet

AT&T

Axient

Exodus

Frontier Global Center

Level3

Lightning / Gigabell

Qwest

Teleglobe

Verio

AboveNet

Digex

Frontier Globalcenter

IDT

Qwest

Verio

vBNS

ANL

Merit

NCSA

NORDUnet

SURFnet

TransPac

ESnet

DREN

Sprint - ICM

Ames MIX

MAE-West

Mbone

UUnet

NISN

FIX - West

Abilene

Ames NGIX - West

Jet Propulsion Lab

Chicago Glenn

Goddard

Langley

Marshall

(Future Multicast Site)

Figure 2. As of June 2000, NREN’s

multicast architecture has been

adopted by numerous networks

across the nation. Marshall Space

Flight Center has been designated

as a future multicast site.
www.nas.nasa.gov/gridpoints Gridpoints 9

transfer rates of at least 24 Mbps to all sites (50 Mbps to

some sites).

During summer 1999, the deployment of MSDP and

PIM-SM continued throughout Internet2’s customer

networks, and among commercial Internet service

providers. NREN provided the catalyst for this deployment by using PIM-SM and MSDP at the Ames MIX,

as well as its peerings at Chicago. By January 2000, the

conversion from dense-mode to MSDP/ PIM-SM was

almost complete throughout the United States (see

Figure 2, opposite).

Multicast Routing Protocols

Global multicast routing requires routers to replicate

multicast packets and forward copies to each interface

where a downstream receiver has requested a copy. This

process is known as multicast forwarding, and it

requires the creation of a multicast forwarding tree for

each multicast group.

In addition to the creation of a forwarding tree, a routing protocol is required. In the usual configuration, the

AS (Autonomous Systems) Interior Gateway Protocol

(IGP) is the source of unicast routes that can also be used for

multicast. A common IGP is OSPF (Open Shortest Path

First). Among autonomous systems, an Exterior Gateway

Protocol (EGP) is used to exchange routes. Today, the universal EGP is Border Gateway Protocol-4 (BGP-4). Multicast Border Gateway Protocol (MBGP) is an extension to

BGP-4 that allows for an exchange of additional routes

specifically for multicast. This is required because the data

paths for unicast and multicast can differ.

In order for multiple autonomous systems to know about

each other’s multicast sources, a helper protocol is required.

Today, this protocol is Multicast Source Discovery Protocol (MSDP). MSDP floods information about multicast

sources among all the Rendezvous Points (RPs) in multiple domains, allowing receivers in one autonomous system

to receive data from a different autonomous system (see

Figure 3).

Protocol Independent Multicast-Sparse Mode

Sparse protocols use the explicit join of a multicast group

by a host to trigger the creation of the multicast forwarding

tree. Initially, the first-hop router joins the shared-tree from

the rendezvous point. For high-bandwidth sources, it will

then switch to a shortest-path tree from the first-hop router

back to the source. PIM-SM does this through the use of

Rendezvous Points that coordinate the creation of the multicast distribution trees throughout the PIM-SM domain

(usually an AS). Within a defined network area, the RP creates a shared tree for every multicast group, and it coordinates the creation of a shortest path tree from a source to all

recipients for high-bandwidth sources.

The Future of Multicast

MSDP has always been regarded as an interim protocol for

several reasons. It incorporates a feature for backwardscompatibility with the old Mbone, and it floods source

information. This flooding, while vastly superior to the

dense-mode data flooding it has replaced, still will not scale

to an Internet with very large numbers of active sources.

For some time now, development of global shared-tree

protocols has been undertaken. Today this has to be considered a difficult and as yet unsolved problem.

In addition, with the commercialization of the Internet, a

new constituency of commercial multicast Internet broadcasters is appearing. These broadcasters would like to

support broadcast-only functionality, rather than the

many-to-many multicast model. They also would like a

single broadcaster to be able to deliver very large numbers

of channels, which would create a multicast address allocation problem. A segment of the multicast address space has

been allocated for this so-called source-specific multicast,

which will allow both of these problems to be solved while

maintaining most of the multicast address space for manyto-many communication. Source-specific multicast will

require a simple modification of PIM-SM behavior to

accommodate the different functionality. MSDP will not be

required for source-specific multicast because the sources

will typically be announced via the Web.

Today, IP Multicast is undergoing rapid development and

deployment in the commercial world, and will be a key

technology in providing efficient sharing of real-time data

among large numbers of systems. 

Network B

Router Router

Network A

Router

Router

Rendezvous

Points

Network C

Router

Router

Rendezvous

Points

Rendezvous

Points

Figure 3. With inter-domain multicast routing, all routers with

external MBGP connectivity have parallel MSDP connectivity. All

routers with external MBGP and MSDP connectivity have meshed

internal MBGP and MSDP connectivity. In addition, the RP must be

part of the MSDP mesh. Each network represents an Autonomous

System (AS). Moreover, the red arrows depict links with MBGP and

MSDP connectivity.

gp
10 Gridpoints

S

ince its invention in 1948, the transistor has revolutionized everyday life – transistor radios and TVs

appeared in the early 1960s, personal computers came

into widespread use in the mid-1980s, and cellular phones,

laptops, and palm-sized organizers dominated the 1990s.

The electronics revolution is based upon transistor miniaturization; smaller transistors are faster, and denser circuitry

has more functionality. Transistors in current generation

chips are 0.18 μm (micron) or 180 nanometers in size, and

the electronics industry has completed development of

0.13 μm transistors that will enter production within the

next few years. Industry researchers are now working to reduce transistor size to 0.1 μm – a thousandth of the width

of a human hair. However, studies indicate that the miniaturization of silicon transistors will soon reach its limit.

For further progress in microelectronics, scientists have

turned to nanotechnology to advance the science. Rather

than continuing to miniaturize transistors to a point where

they become unreliable, nanotechnology offers the new

approach of building devices on the atomic scale (see Transistors: Electronic Workhorses, opposite). One vision for the

next generation of miniature electrical devices is atomic

chain electronics, where devices are composed of atoms

aligned on top of a substrate surface in a regular pattern.

The Atomic Chain Electronics Project (ACEP), part of the

semiconductor device modeling and nanotechnology group

integrated product team within the NAS Systems Division,

has been developing the theory for understanding atomic

chain devices. In this type of research, collaboration with

The Smallest

Nanoelectronics:

Atomic Devices

with Precise

Structures

Transistor miniaturization is

reaching its limit. Atomic scale

transistors are being developed to

enable future microelectronics.

By Toshishige Yamada

Larger Than 1 Micrometer

0.01 to 0.1 Micrometer

Gate

Gate

Source Drain

Source Drain

1a

1b

1c Smaller Than 0.001 Micrometer (1 Nanometer)

Figure 1: The evolution of transistor miniaturization has

taken electronic devices from the macroscopic scale (1a),

greater than 1 μm (micron). An electron particle (green)

sees a jelly area (blue) formed by 10,000 dopant atoms,

which is averaged out to be the same in devices, resulting in

the same switch-on voltage. In transistors miniaturized to

the mesoscopic scale (1b), 0.1 to 0.01 μm, an electron wave

(green) can tell precisely where the dopant atoms are located, and this leads to different switch-on voltages. To solve

this problem, researchers at the NAS Facility have patented

an atomic device concept using atomic chains (1c) rather

than further the miniaturization of conventional transistors.
www.nas.nasa.gov/gridpoints Gridpoints 11

the experimentalists is also essential for success. ACEP members are collaborating with Dongmin Chen of the Nanophysics Group at Boston’s Rowland Institute, who characterizes electronic properties of atomic structures using a

Scanning Tunneling Microscope (STM). ACEP

researchers are also collaborating with Richard

A. Kiehl at the University of Minnesota’s electrical engineering department, who studies the

autoformation of atomic structures. Autoformation may lead to a breakthrough for

mass production of atomic-scale devices.

Doping and Gain in Transistors

A critical element in transistor functioning is the use of

dopants – impurities added to silicon to manipulate and

control its electronic properties. Typically, there are several

Millions of tiny transistors are at the heart of

today’s electronics world. The main function of

a transistor is to amplify a small input signal

into a large output signal as shown in the diagram (a).

The most common transistor used in today’s electronics is

a field-effect transistor (FET). To understand the operation of an FET, the popular analogy is that of a flexible

hose system with weight on it. When the weight is small,

water flow is not hindered, as shown at right. As the

weight is increased, the hose becomes pinched, resulting

in less water flow. In this analogy, the weight corresponds

to the input signal and the water passing

through the hose is the output.

In a field-effect transistor, the input is a voltage applied to the gate electrode, and the

output is a current flowing between the

source and the drain. When the gate voltage

is low, electrons flow freely from the source

to the drain. When the gate voltage is high,

electrons are repelled under the gate and

fewer electrons flow. This is known as the

field effect. 

In the analogy of water flow through a hose

(b), the constriction caused by the weight

depends on the material of the hose. For

example, if the hose is a steel pipe, then the

weight (input) has little effect on flow (output). In the same way, if the substrate of an FET is a

metal, the gate voltage has little effect on current flow.

Therefore, we need a material corresponding to a flexible

hose – a semiconductor. 

What FET property corresponds to the flexibility of the

hose? That is doping, or the intentional inclusion of

impurity atoms in the semiconductor substrate. By

manipulating doping, a semiconductor can be changed

from something almost an insulator (softest) to something almost a metal (hardest).

Figure 2: Rendering (2a) represents an atomically precise structure using the substrate

atomic lattice (blue atoms as a template for

atomic chain electronics (red atoms). Two confinement schemes for topmost atoms on the

substrate are (2b), where atoms are floating,

and (2c), where the atoms are firmly bonded to

the substrate. Green dots represent hydrogen

atoms, and they work as an electronically insulating layer with an atomic thickness.

2c Chemical Bonding

Precise Atomic Structure

2b Floating

2a

Out

Gate

In

More Current

More

Water

Less

Water

Weight

Less Current

(b) Hose vs FET

(a) Amplification

Input

Output

Out

CChhaannnneell SSoouurrccee DDrraaiinn

SSuubbssttrraattee

TTrraannssiissiittoorr

Transistors: Electronic Workhorses
12 Gridpoints

thousand dopant atoms in a transistor and these appear as a

dopant “jelly” as in Figure 1(a) – on page 10. When using

large numbers of dopant atoms in the construction of an

electronic device, the precise location of these atoms in the

transistor is not very important to the functioning of the

transistor. However, when the transistor size is reduced to

less than 0.1 μm as in Figure 1(b), the number of dopant

atoms is small – less than 100. At 0.1 μm or less, each dopant’s position affects how electrical current flows through

the transistor. Present-day manufacturing technology cannot precisely control the location of so few dopant atoms,

and this causes small variations in how the transistor functions. This is fatal when millions or billions of transistors

are integrated on a computer chip,

because these slight variations can

cascade from one device to the

next and eventually lead to malfunction. The solution to this

variation problem devised by

ACEP calls for all device structures to be built using atomic

chains laid out in a regular, precise

pattern by anchoring atoms to a

substrate as in Figure 1(c).

A second critical element in transistor function is that the output of

the device should be a magnification of its input – this is called

gain. To create atomic chain transistors that produce gain, ACEP

researchers have found that the

phenomenon known as field effect

(see Transistors: Electronic Workhorses, page 11) can be adopted as

an operating principle. To build a field-effect transistor at

the atomic scale (similar in construction to those of larger

scales), scientists need to devise chains with both semiconductor and metal properties. First, the ACEP team tackled

a simple problem theoretically: If researchers can arrange

silicon atoms along a line floating in air, is this chain semiconducting? The answer is surprising: although bulk or thin

film silicon is semiconducting, the silicon chains are always

metallic. Fortunately, ACEP’s research shows that a magnesium chain is semiconducting, even though ironically, bulk

magnesium is metallic. 

Substrate Determines Chain Properties

Of course, atoms cannot be floated in air, but must be

placed on top of a substrate. Surface atoms of the substrate

attract atoms in the chain and hold them at fixed positions.

The substrate has atomic scale corrugations on the surface

and these may be used to create a precise pattern as shown

in Figure 2(a) – on page 11. However, ACEP members

have found that this force is too weak to secure atoms reliably, see Figure 2(b). ACEP scientists concluded that a

chemical bonding scheme to secure atoms to the substrate

as in Figure 2(c) was the reliable approach to follow. Research soon showed that the chain properties were strongly

influenced by the substrate material and surface orientation

Germanium

topmost atom

Hydrogen atom

First Layer Silicon atom

Second Layer Silicon atom

Electron 'cloud'

π-chain

σ-chain

Figure 3. Semiconducting

Germanium chains electronically

isolated from a silicon substrate.

A

A

4c

4a 4b

Figure 4: Atom manipulation and electronic characterization

of small atomic structures are accomplished using a Scanning

Tunneling Microscope (STM) tip (green). Researchers can

push or pick up an atom (red) on the substrate (blue) using

an STM tip as in (a). A created small atomic structure (red)

can be electronically characterized by measuring current for

applied voltage either in (b) a vertical geometry, or (c) a

horizontal geometry. The latter needs a dual-tip STM and is

technically quite challenging.
www.nas.nasa.gov/gridpoints Gridpoints 13

when chemical bonding is relied upon. In fact,

the same atomic chain can be either metallic

or semiconducting depending on the configuration of the substrate. For example, silicon

chains with two chemical bonds to the substrate atoms are semiconducting – otherwise

silicon chains are metallic. Aluminum chains

with one chemical bond are semiconducting –

otherwise, aluminum chains are metallic. A further concern

was that electrons travelling along an atomic chain may

detour into the substrate through chemical bonds and possibly exit via a neighboring chain – resulting in the shortcircuit of two atomic chains. This short circuit is fatal for

electronic applications and must be avoided. ACEP scientists have clarified the conditions for which the substrate

surface acts as an insulator in the chemical bonding

scheme. According to this, silicon and germanium crystals

offer good insulating substrates.

Putting It All Together

The ACEP team has achieved the first step towards the

development of atomic chain electronic devices. On top of

a silicon substrate, germanium atoms can be attached with

two chemical bonds as shown in Figure 3 – on page 12.

This structure is a semiconducting chain on an insulating

substrate. Nearby chemical bonds on the substrate are saturated with hydrogen atoms so that they are electronically

inactive. This has resulted in the development of an essential component for an FET on the atomic scale.

These structures could be experimentally fabricated and

characterized using an atom manipulation technology with

a Scanning Tunneling Microscope (STM) as in Figure 4 –

on page 12, or some other related techniques. Quite recently, the field effect in the molecular/atomic scale has been

demonstrated in carbon nanotube FET experiments in

Figure 5 by Cees Dekker’s group at Delft, and Phaedon

Avouris’ group at IBM. This supports the ACEP’s predictions for atomic devices, and the basis for atomic chain

electronics is now being established.

Acknowledgements

The author acknowledges fruitful discussions with and/or

continuous support for this project by Meyya Meyyappan,

T. R. Govindan, C. W. Bauschlicher, Jr., H. Partridge, and

B. A. Biegel. Careful reading by H. Yamada is gratefully

acknowledged.

Toshishige Yamada is a Senior Research Scientist with

Computer Sciences Corp. at NASA

Ames Research Center. He obtained a

Ph.D. in electrical engineering from

Arizona State University. He held

positions at NEC Microelectronics

Research Labs., Japan, and Stanford

University. NASA filed a patent

application on his atomic chain electronics innovation, and the work was

presented at an invited talk in the

196th Electrochemical Society Meeting last fall.

Visit these sites for additional sources of

information about nanotechnology:

Integrated Product Team on Devices, Nanotechnology

www.ipt.arc.nasa.gov

The Integrated Product Team on Devices and Nanotechnology’s home page offers a gallery of nanotechnology

experiments, NASA Ames’ nanotechnology capabilities,

and a list of projects and publications. 

National Nanotechnology Initiative Home Page

www.nano.gov

Read the full text National Nanotechnology Initiative:

Leading to the Next Industrial Revolution, supplement to

President Clinton’s FY 2001 budget.

Interagency Working Group on Nanoscience,

Engineering and Technology

www.whitehouse.gov/WH/EOP/OSTP/NSTC/html/

iwgn/IWGN.Research.Directions/toc.html

This document lays the foundation for the future of

nanotechnology research and development, and how

research efforts should be coordinated within the 

scientific community.

_

+

Nanotube

I

D

VG

_

+ VD

Source Drain

Gate (silicon)

SiO2 SiO2

Figure 5

gp

Figure 5: Carbon nanotube field effect transistors

(FETs) experimentally built by Delft and IBM, with

function similar to that predicted for an atomic

chain FET in Fig. 1(c), have demonstrated the

transistor action in the molecular/atomic dimension successfully. 
14 Gridpoints

Wind-generated electricity is the fastest growing,

most cost-competitive renewable energy resource

in the world. According to Wind Force 10, an

international report by the European Wind Energy Association, by the year 2020, wind-generated electrical power

will provide 10 percent of the

world’s electricity, reducing

carbon dioxide emissions by

more than 10 billion tons a

year. Unlike fossil fuels,

renewable energy does not exhaust the Earth’s supply of

non-renewable mineral resources such as coal and natural gas. A team of researchers

from the Department of

Energy’s National Renewable

Energy Laboratory (NREL),

NASA Ames Research Center,

and the University of California at Davis have launched a

research program using both

experimental and computational approaches to improve

our understanding of wind

energy systems. Researchers

from Ames’ Army/NASA

Rotorcraft Division are using

the high-performance computers at the NAS Facility to support the project.

The experimental part of this

program, known as the

Unsteady Aerodynamics

Experiment (UAE), tested NREL’s wind turbine in the

NASA Ames 80- by 120-foot wind tunnel from mid-April

to early May. Computational fluid dynamics (CFD) predictions for the same wind conditions gathered during the

wind tunnel experiment were computed on the CRAY

C90 operated within the NAS

Division and managed by the

Consolidated Supercomputing

Management Office (CoSMO).

These computations require large

amounts of data storage available

through NAS’s SGI Origin-based

storage system, NAStore.

Computational Modeling

NREL’s wind turbine experiment

is the first in the United States to

employ high-resolution NavierStokes calculations to investigate

the aerodynamics of a wind turbine. Using CFD predictions,

NREL and its collaborators plan

to develop blade stall delay models for creating better turbine designs applicable to both the wind

power and rotorcraft industries.

“Some problems encountered

when designing an efficient wind

turbine are related to those experienced with rotorcraft. Both

wind turbines and rotorcraft

have rotating blades with similar

stall behavior,” explains Bob

Kufeld, NASA project lead for

CFD Supports Wind

Turbine Research

Before any testing took place in the wind tunnel at

NASA Ames, experiments were conducted at NREL’s

field labs in Boulder, Colo. Researchers installed

smoke generators in the tip of the wind turbine rotor

to experimentally visualize the airflow and turbulence surrounding the blade. (NREL)

NAS provides the National Renewable Energy

Laboratory with computational resources to help

improve next-generation wind turbine designs.
www.nas.nasa.gov/gridpoints Gridpoints 15

the UAE’s wind tunnel experiments. Stall occurs when the

rotor lift no longer increases with the angle of attack.

Using results obtained from the well-known CFD code

OVERFLOW, along with wind tunnel data, researchers

can gain a better understanding of the rotor aerodynamics. 

To improve wind turbine design, rotor design codes used

by industry need a high degree of accuracy at low computational cost. “To date, there hasn’t been a thorough set of

experimental data to verify the accuracy of the computer

codes because wind turbines operate in the inherently turbulent wind of the Earth’s atmosphere. Current engineering models used are not very effective at higher wind speeds

because our present theories do not accurately predict

blade stall,” explains Earl Duque, computational lead for

the UAE in the Army/NASA Rotorcraft Division. Results

from the UAE were obtained in the precisely controlled

wind tunnel environment, and will provide industry with a

valuable database to validate its computer models and

CFD codes. This new data will enable designers to develop

more reliable and cost-effective wind turbines.

Duque’s extensive background in rotorcraft computations

is beneficial for this project. “My experience working with

others on rotorcraft computations in the past has made

this project easier in the areas of visualization and grids.”

With the help of MIT researcher David Kenwright, formerly of NAS’s data analysis group, Duque modeled vortex

patterns over a rotorcraft blade, using Kenwright’s flow

visualization techniques. This work helped him visualize

what is happening with the wind turbine blades. Working

with NAS senior scientist Rupak Biswas, Duque also

investigated grid adaptations, which enables accurate

prediction of blade stall. Duque’s earlier studies allowed

him to understand how to build the grid systems for the

NREL experiment.

Reducing the Cost of Energy

Charged by the Department of Energy to reduce the cost

of electrical power produced from renewable sources, NREL

began its wind experiment in 1989. The UAE research

wind turbine has been field-tested in various configurations

since the beginning of the project. “The current phase of

the experiment (phase six) is the most realistic wind turbine blade – it’s a two-blade rotor system, which is more

modern and cost-effective than the three-blade configuration of earlier experiments. Two blades require less building materials but generate the same amount of power,”

says Kufeld.

When NREL began its studies, wind energy cost more

than 20 cents per kilowatt-hour – which includes the system’s initial capital investment, operation, and maintenance costs. Today, the price has dropped substantially to

about four cents per kilowatt-hour. NREL’s goal is to

reduce this cost further, to two and a half cents per 

kilowatt-hour.

Comparisons: Actual vs. Computational

The wind tunnel test turbine is equipped with cameras, surface pressure taps, and strain gauges to gather data for validating numerical prediction models of aerodynamic blade

responses. Testing in a controlled wind tunnel environment

provides data that is free of interference from atmospheric

turbulence, which substantially complicates turbine blade

aerodynamic response. This data is ideal for validating computational blade stall models and CFD codes. 

Continued on page 16

Representing the air surrounding the wind turbine blade, these

visualizations of numerically simulated flow fields are based on

wind tunnel test conditions of NREL’s phase-six wind turbine.

The visualizations were constructed using Fieldview Software, by

Intelligent Light Inc., on a desktop computer. The red bands

represent streamlines flowing over the blade at a single instant

in time. Before the blade begins to stall (above), the air

streams smoothly over the blade’s surface. When the blade

begins to stall, the airflow becomes unsteady, limiting power

output (below). (courtesy Earl Duque)

Stalled and Non-Stalled Turbine Blades 

(stream lines)
Continued from page 15

Working closely with NREL, Duque brought

NAS computational resources to the project in

1997. “Computations extend the boundaries

of what we can test,” says Duque. “In the field

or the wind tunnel, there are only so many

things you can measure. With CFD you can

see what’s happening to the airflow around the

blade that cannot be seen in field experiments.”

Only a few selected points on the rotor have

sensors to collect data in an experiment. If the

data from those points match well to computer calculations, every point of the flow field

can be re-created using CFD. 

Jasim Ahmad and Roger Strawn in the Army/

NASA Rotorcraft Division have improved the

algorithm that Duque used to run CFD calculations of the wind turbine in phase two of the

experiment. Phase two computations took 150

CPU hours to complete. Now, phase six calculations can be done in 40 CPU hours on

CoSMO’s CRAY C90. 

Duque will use the experimental data collected

from the wind tunnel test and compare it to

the predictions he creates using OVERFLOW

(version 1.8), a Reynolds-averaged thin-layer

Navier-Stokes (RaNS) code. He plans to use

OVERFLOW-D for the next set of wind turbine computations. The first version of OVERFLOW, developed by Pieter Buning, currently

at NASA Langley Research Center, was later

modified by Ahmad for unsteady and steady

rotor applications. OVERFLOW predicts the

power output and the flow field around a turbine. Strawn is consulting with NAS researchers Rupak Biswas, Rob Van der Wijngaart, and

Maurice Yarrow on a parallel version of

OVERFLOW-D for rotorcraft. 

In the future, OVERFLOW-D may be used

by the Information Power Grid (IPG) community (see the IPG story on page 18) for

other fluid flow problems requiring highly

refined grids, resulting in massive amounts of

computational data such as helicopter and tiltrotor configurations.

“OVERFLOW really tests the IPG system –

there is too much data to process on any single

machine at NAS, but it can potentially be

done on the IPG once it is fully operational,”

says Strawn. The team anticipates running

OVERFLOW on an SGI Origin 2000 for the

phase six calculations in winter 2001. 

The graphic above represents the velocity contours of an S809 airfoil

under pre-stall conditions. This airfoil is the same one used on NREL's

Unsteady Aerodynamics Experiment wind turbine. Due to its design, the

S809 airfoil was calculated to begin stalling at approximately 10-degrees

angle of attack and to hold lift over a large range of angles. This lift

characteristic helps maximize and control the power output of the turbine. Below, the airfoil is positioned at a 14-degree angle of attack, a

post-stall condition. Wind turbines use stall to control power output of a

system. Unit of measurement is Mach number. (Earl Duque) 

Wind Turbine Airfoil

(pre- and post-stall conditions)

16 Gridpoints
www.nas.nasa.gov/gridpoints Gridpoints 17

NREL, NASA Ames, and UC Davis have made measurable progress in the area of wind power production by providing the industry with detailed experimental data and

valid computational methods. From gathering detailed

pressure data on wind turbine blades to predicting the

same pressure on CoSMO’s CRAY C90, every accomplishment brings the Department of Energy closer to its goal –

more affordable, clean, and sustainable electricity. 

— Holly A. Amundson

Acknowledgments

Funding for the UAE wind turbine is provided by NREL’s

Chief of Applied Research, Mike Robinson, through the

Army/NASA CFD Code Project. C.P. Van Dam and 

students at the University of California at Davis provide

support for the computational component of NREL’s

UAE project.

Editor’s Note: As Gridpoints went to press, Earl Duque

accepted a new challenge at the College of Engineering and

Technology, Northern Arizona University in Flagstaff as an

associate professor of mechanical engineering. Duque is continuing his research in wind turbine technology and applied

computational fluid dynamics.

A three-week test of the National Renewable

Energy Laboratory’s wind turbine was undertaken in the world’s largest wind tunnel at NASA

Ames Research Center. Researchers use aerodynamic and structural dynamic data collected

during tests in the 80- by 120-foot tunnel, and

numerical simulations run on the CRAY C90

computer at the NAS Facility to improve the

understanding of wind turbines. This knowledge

helps engineers design and operate more costeffective wind turbines. (NASA)

For the past six years,

wind energy capacity

has increased at an

annual rate of 40 percent. The Wind Force 10

report, prepared by the

European Wind Energy

Association (EWEA),

predicts a 10 percent

increase in the world’s

wind energy production

by 2020. Ten percent, or

1.2 million megawatts,

are equivalent to

Europe’s electricity consumption for an entire

year. EWEA believes

wind energy expansion

will create 1.7 million

new jobs.

gp
18 Gridpoints

During the 1970s, researchers were constructing a

network of computers to share information in an

effort to expand science. The resulting computer

network of the ’70s became the Internet of the 1980s and

’90s. Today, researchers led by the NAS Systems Division

are expanding the Internet model to build NASA’s Information Power Grid (IPG) – a distributed system linking

remotely located computer networks, storage devices, and

instruments into a single computational grid. 

NASA has selected Ames as the Center of Excellence for

Information Technology and the NAS Systems Division as

the focal point for high performance computing as well as

the development of NASA’s prototype IPG. In September,

NASA researchers will demonstrate the IPG’s capability and

its ability to access geographically distributed systems.

NASA’s IPG team will deliver a “persistent testbed” for scientists to test their applications, and to provide the framework for systems software development. To meet the

September 30 milestone, the team is developing more than

a dozen tools to expand the grid’s infrastructure.

IPG’s Network Connectivity

The first measurable step in the grid’s development was

taken last April when NAS researchers demonstrated the

IPG network’s connectivity and its ability to access distributed archival data. The April milestone sought a data transfer rate between 10 and 50 megabits per second while

retrieving files from two remote sites. Using NREN (the

NASA Research and Education Network) for the connection, the tests delivered a connectivity rate of 58 megabits

per second with data transfers from four separate locations.

“While the April demonstration is by no means high speed,

network connectivity lays the foundation for the next step –

a high-speed interconnect test,” says Leigh Ann Tanner,

manager, advanced systems development. 

‘Launch Pad’ is Gateway to the Grid

The most visible piece of the grid’s infrastructure is the

web-based user interface, or portal, called the NASA IPG

“Launch Pad.” This interface is being developed in collaboration with researchers at San Diego Supercomputer Center,

the National Computational Science Alliance (NCSA),

Argonne National Laboratory, and the University of

Indiana. The Launch Pad will allow researchers to create

and submit a job, track its progress, and determine which

machine is processing the work. This simple and easy-to-use

web interface will allow a user to specify the resources

required to run an experiment, such as the amount of

memory required and the number of computer processors,

and then “launch” the job to the grid.

“Scientists often perform the same basic task repeatedly,”

says George Myers, NAS scientific consultant and portal

development group lead. “Being able to upload previously

created job templates will only require changes to a line or

two of code, or the addition of new file specifications, without completely rebuilding job submission information each

time. We are working to make the job template modular so

that researchers can customize their view of the portal.” 

The portal group is finalizing the look and feel of the NASA

Launch Pad, which will use a grid portal development kit

adapted from NCSA’s Jason Novotny and Vaughn Welch’s

Infrastructure For NASA’s

Information Power Grid

Nears Completion

More than a dozen components of the IPG are

being readied for roll-out by September 30.
www.nas.nasa.gov/gridpoints Gridpoints 19

interface to the grid. Dennis Gannon of the University of

Indiana has also been advising the portal development group.

User Support, Middleware Under Development

To answer grid users’ questions and troubleshoot problems,

NASA is developing a new grid support model that will

provide 24 hour, seven day per week assistance to users,

regardless of an end-user’s location. The support model

team is tasked with developing procedures for problem

reporting and tracking, routing questions to the proper

support group and how the situation will be remedied.

Varying levels of support exist at the three participating

NASA centers, ranging from phone or e-mail support only

to the NAS Systems Division’s “24 x 7” assistance. For more

extensive support, the NAS scientific consultants are available Monday through Friday from 7 a.m. to 5:30 p.m. (PST).

Answers requiring other specific knowledge areas may reside

with support staff located at other participating NASA

research centers – currently Glenn and Langley. To address

the intricacies of user assistance, the IPG team is developing one mechanism to standardize all of the support functions that will be in place by September 30.

NASA’s prototype IPG will use the Globus middleware

toolkit – developed by Ian Foster of Argonne National

Laboratory and Carl Kesselman of the University of Southern California’s Information Sciences Institute, to enable

different types of applications and interfaces to communicate with the grid. Judith Utley, a NASA IPG team member, coordinates upgrades and new releases of Globus to

each of the grid sites, and resolves software bugs. Utley also

manages the deployment of the Grid

Information Service (GIS) that

allows researchers to poll the GIS to

determine what jobs are running, as

well as types of systems and processors are available. “Globus deployment and grid information services

require close coordination between

all NASA IPG centers,” says Utley.

“Our weekly teleconferences provide

the avenue to complete this phase of

the project.” Utley collaborates on

GIS deployment with Glenn

Research Center’s Kim Johnson and

Allen Holtz as well as Langley

Research Center’s Mike Perry and

Greg Cates.

Keeping the Grid Secure

“Security for both the user and the

grid is of the utmost importance,”

says NAS systems engineer Yvonne

Malloy, who is implementing the

IPG’s certificate infrastructure using

Netscape CMS (Certificate

Management System) to address this issue. To obtain

authorization to run jobs on the IPG, a user will request a

certificate through the online grid registration authority.

Once a user has been authenticated and authorized, a certificate is issued and users can download it onto their web

browser. Each job is “signed” with the certificate. Malloy is

currently incorporating the certificate system into the

Globus structure, and is planning to take user security to

the next level using the ‘MyProxy’ software system also

developed by Welch and Novotny. 

“MyProxy is a way for users to limit the exposure of their

private key password,” says Malloy. “The private key is

decrypted long enough to generate proxies and then it is reencrypted. These proxies are valid for short amounts of

time, but are treated like the user’s actual certificate.”

MyProxy is expected to be installed by the end of August. 

Managing the Results

After running a job on the IPG, results may be stored in a

location capable of handling tremendous volumes of data.

For data management, NAS engineers are using a mass storage system for NASA’s IPG. Known as the Data Migration

Facility (DMF), it consists of two SGI Origin-based systems, a large fiber channel RAID (Redundant Array of

Inexpensive Disks) array capable of storing 1.3 terabytes of

data, and four attached tape drives. The tape drives will

migrate stored files from the RAID array to removable tape

cartridges. “Off-loading a file’s data blocks from the RAID

array to tape will give us virtually unlimited storage capacity,” says Bill Arasin, a systems analyst in the high speed

processor group. “There will be a brief delay when users

NASA’s Information Power Grid links high performance computers at Ames, Glenn, and

Langley Research Centers. Infrastructure enabling researchers to test applications and

develop grid related systems software will be completed by September 30.
20 Gridpoints

retrieve their files, but this offers the ability to store as much data as we have tape.”

The DMF is a redundant system that

maintains a copy of each file on two separate disks in the event of a disk failure. To

add further redundancy, both systems will

be configured to run Failsafe DMF which

enables either system to take over all the

services of the other if a system outage

occurs. “Failsafe DMF provides a seamless

shift between servers with no interruption

of service detectable by users,” says Arasin.

Proving the Grid’s Reliability

To ensure that IPG users will have a reliable computing environment, NASA

engineers have been testing the grid’s performance. Validation encompasses four

areas: Each piece of the grid’s infrastructure is repeatedly tested to ensure that it

works and will perform adequately; that it

will interface with other systems and software; that it will perform uninterrupted

while handling a large number of jobs; and

that it remains stable as more computations are added into the system. “Our tests

are designed to model the tasks that will

most frequently be done by users on a day-to-day basis in

the grid environment,” says Ray Turney, IPG test engineer.

“All building blocks of the grid’s infrastructure are interdependent upon the others,” Turney continues. “For example,

when new software versions are introduced, the system

environment may change.” Nightly tests run simulated jobs

through the systems at Glenn, Langley, and the local

machines at Ames. Turney is currently testing the Globus

environment and the Metacomputing Directory Service. 

Condor: Adding Flexibility to the IPG 

In addition to high performance computing, where job

speed is measured in floating point operations per second,

researchers can also use high throughput computing resources where large numbers of processors work for long

periods of time – measured in weeks or even months.

“We’re not only linking supercomputers,” says Eric Langhirt, NAS Condor systems specialist, “but workstations that

are idle will now become a resource for the grid.” Condor,

developed by Miron Livny and a team of researchers at the

University of Wisconsin, is a distributed batch processing

system that scavenges compute cycles from idle workstations

on a network and runs jobs while the local user is away.

The software system works by monitoring the CPU load

and keyboard activity of a pool of workstations to determine whether a terminal is idle and available to run jobs.

The system matches a job’s requirements for resources with

workstations that have available computing cycles. Once a

match is made, the job is sent to the workstation for processing. Condor continually monitors the workstation’s

CPU load and its keyboard; movement of the mouse or a

keystroke will restore control of the computer to the local

user. Condor then moves the job to the next idle workstation in the pool and continues processing.

Using the Condor system, the NAS Facility’s more than

400 workstations will provide nearly 2 million CPU hours

each year – equal in power to one of the NASA’s 256-

processor high performance computers. When all three

NASA grid centers are linked, this number is expected to

nearly double.

Looking Ahead

Additional infrastructure components slated for completion

this fall include a distributed debugging and performance

analysis system, a wide area network connection capable of

transmitting at least 100 megabits per second, a computer

hours allocation and accounting system, and the integration

of the CORBA programming language to the IPG. 

Each completed and integrated piece of the grid’s infrastructure brings the IPG team closer to meeting its September goal of “demonstrating seamless operations within a

heterogeneous distributed computing environment.”

— Nicholas A. Veronico 

From left to right: Ames Center Director Henry McDonald, NAS Division Chief Bill

Feiereisen, NASA Administrator Daniel Goldin, and NAS senior scientist Jim Taft

discuss high performance computing and system scalability in the NAS Facility’s

computer room. Lomax, the 512-processor SGI Origin 2800, shown in the background, is a node on the IPG and was a key component in demonstrating the

grid’s connectivity and ability to access distributed archival data.

(Nicholas A. Veronico)

gp
September 11-15 – Albuquerque, New Mexico

The Linux Supercluster Users Conference is aimed at sharing information on scientific computing techniques. The

objective of this meeting is to help computational scientists

and engineers develop applications to achieve maximum

performance and scalability on Linux Supercluster systems.

Hosted by the National Computational Science Alliance

(NCSA), the Advanced Computing Technology Center at

IBM Research, and the High Performance Computing

Education and Research Center. For additional information, visit:

http://clumber.tc.cornell.edu/actc/Supercluster/index.html

September 19-20 – Mountain View, California

NASA’s Information Power Grid project will host a workshop to demonstrate and review the IPG’s growth, examine

current issues, and plan future directions. Workshop proceeding and selected papers will be published in a special

issue of “Scientific Programming.” Contact Marcia

Redmond at (650) 604-4373 or visit the workshop’s

website at: http://www.ipg.nasa.gov/ workshop.html

September 18-20 – Davis, California

The Fifth Symposium on Overset Grids and Solution

Technology will be held at UC Davis. This international

symposium provides a joint forum where mathematicians,

scientists, and engineers from academia, industry, and federal laboratories can exchange research ideas, new algorithmic and software developments, and applications pertinent

to the state-of-the-art and state-of-the-practice of Overset/

Chimera Grid and Solution Technology. More information

about the symposium can be found at:

http://ntserver.itd.ucdavis.edu/Chimera2000/

September 28 – Mountain View, California

SGI will roll out its new Origin and Onyx 3000 modular

computing systems at its Mountain View headquarters

from 2 p.m. to 7 p.m. Bill Feiereisen, NAS Systems

Division chief, is a featured guest speaker. For directions,

registration, and additional information, call (800) 318-

6432, or visit: http://www.sgi.com/events/thinkahead 

October 9-13 – San Jose, California

The Microprocessor Forum 2000 provides designers and

users of high-performance microprocessors with insights

into new processor designs – for applications ranging from

PCs and workstations to information appliances and the

Internet. For additional information, visit the conference’s

website at: http://www.MDRonline.com/MPF/conf.html

October 30-November 1 – Orlando, Florida

Storage Networking World Conference and Expo features

panel discussions and case studies on the future of Storage

Networking and topics such as storage outsourcing, managing storage and server assets, Storage Area Network

interoperability, the role of storage systems within the

Internet infrastructure and integrating diverse environments, along with a separate track covering in-depth technical issues and deployment examples associated with storage networks. More information is available at:

http://www.storagenetworkingworld.com

November 3-5 – Bethesda, Maryland

Eighth Foresight Conference on Molecular Nanotechnology. This conference is a meeting of scientists and technologists working in fields leading toward molecular nanotechnology: thorough three-dimensional structural

control of materials and devices at the molecular level. An

introductory tutorial on foundations of nanotechnology

will be held November 2. For more information, phone

(650) 917-1122, or fax (650) 917-1123. The conference’s

web address is:

http://www.foresight.org/Conferences/MNT8/index.html

November 4-10 – Dallas, Texas

SC2000, the conference of high performance networking

and computing, will meet at the Dallas Convention Center

for a series of technical programs, demonstrations, educational outreach, and visualizations of computational data.

SC2000 is sponsored by the Institute of Electrical and

Electronics Engineers Computer Society and the Association for Computing Machinery’s Special Interest Group on

Computer Architecture. Be sure to visit the NASA booth.

Further details can be obtained at: http://www.sc2000.org

www.nas.nasa.gov/gridpoints Gridpoints 21

Calendar of

Events

Multi-wall nanotube compression (buckling), simulation and visualization by Deepak Srivastava

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Network B

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CART3D: A New Generation of Grids

3-D grid software automatically generates vehicle simulations from complex geometries. See page 4.

NREN Drives Global Deployment of

Multicast Protocol

Multicast will speed up the Internet by enabling a single

data packet to be distributed to mulitple users simultaneously. See page 7.