Polymath A (mostly) technical weblog for Archivale.com

August 6, 2010

The Helium Question

Filed under: Aeronautics,Engineering,Lighter than Air,Materials — piolenc @ 11:21 pm

[This piece first appeared in the Fall/Winter 2006 issue of Aerostation magazine]

LTA: 2006 and the Helium Question

The year 2006 was much the same as any other recent year, at least as far as lighter-than-air flight is concerned. Hopes were raised, then dashed. Projects were mooted, then cancelled. Brave talk was uttered, then swallowed.

If Ought Six is remembered for anything, perhaps it will be that the first visible cracks appeared in the ever-rickety edifice of helium supply. For the first time that I can recall, some users of helium were told that they could not have any at any price, due to the fact that one of the world’s few helium extraction plants was undergoing refurbishment. Presumably extraction has since resumed—there are no panic-stricken “Brother, can you spare some gas?” posts on the LTA-related lists—but this little hiccup is a harbinger of things to come.

Those of you who have followed my rants over the years may want to skip the rest of this piece, but some points deserve to be reviewed. As commodities go, helium is extremely unusual—perhaps unique. It is a by-product of the extraction of another commodity—natural gas—whose unit value is much lower, but whose aggregate value is orders of magnitude greater. This means that the usual assumptions about supply and demand do not apply.

To make it clear why this is so, imagine a commodity—say, a precious metal—that exists in a concentration of a fraction of a percent in a matrix that has no market value. If the market value of the metal justifies it, somebody will extract the tiny metal moiety from the huge mass of matrix, refine and market the metal and dispose of the now completely valueless matrix. The key fact is that, in this hypothetical but typical case, the extraction is driven solely by the market for the metal. If the market value of the metal drops below the cost of bringing it to market, extraction ceases and the metal remains in the ground, in its matrix, waiting for changing conditions to again make it profitable to exploit it.
Contrast this with what will happen if there is a significant increase in demand for helium. Helium, as we know, exists as a tiny fraction of natural gas; some deposits contain more helium than others, and gas from some of those favored deposits passes through a helium-extraction plant on its way to market. The helium in natural gas that is produced without extracting the helium is gone forever, wasted.

Now suppose that there is an increase in demand for helium. Once stored helium stock is exhausted, the only way to meet the greater helium demand is to increase the production of natural gas. This may be done, up to the point that storage capacity for natural gas awaiting delivery to consumers is completely used up. At that point, helium production is capped at a rate proportional to the current demand for natural gas, irrespective of demand for helium. Nobody is going to flare off natural gas to accommodate helium users!

Now the operation of a free market, when production of a commodity is fixed and demand for it increasing, is to raise prices until demand drops to match the supply. This gives a bidding advantage to users who are well-funded and use relatively small quantities of helium. LTA doesn’t match that description, and never will. But there’s worse.

Another effect of a free market is that rising prices of a commodity encourage capital to move into production of that commodity, leading to increased capacity, which in turn tends to put the brakes on price increases. Can we expect this to happen with helium? One can imagine that, with helium prices skyrocketing, producers of natural gas from fields less favored by Nature than those now being exploited might install helium extraction plants at their fields, thus intercepting streams of helium now going up the stack. And then again, maybe not. Helium extraction is capital-intensive—essentially, it requires that all gases except helium be liquefied, leaving only helium in gaseous form. Depending on the projected exhaustion of the field, the helium concentration in the gas and their estimate of the persistence of increased demand, the field’s exploiters may or may not feel that they can expect an adequate return on their investment in new helium plant. Even assuming that the answer is always affirmative, there is a definite physical limit to this capacity increase, which is imposed by the rate of production of natural gas. What is more, each increment of production will be smaller than the last and cost more per unit of capacity, as poorer fields are added to the helium production stream.

The best scenario that we can expect, then, in the event of a true rebirth of helium-based LTA, is a steady rise in price, possibly restrained (but not cancelled) by capacity increases. It is a safe bet, however, that any major increase in helium demand will run up against a hard capacity limit, whether imposed by the reluctance of field exploiters to install expensive helium extraction or by the finite and tiny concentration of helium present in the natural gas stream.
When such an absolute limit is reached, modern governments show a deep reluctance to let market forces operate. Instead, rationing and price controls are imposed and favored users are given priority for supply. In the USA, at least, there is no doubt of LTA’s position in the hierarchy of government favor: near bottom, perhaps just one step above party balloons, perhaps even one step below (what would a political campaign be without balloons, eh?).

In the long run, the Earth’s supply of helium will be exhausted when we run out of natural gas, regardless of the level of demand for helium. Helium is the end product of a long chain of radioactive decay, and for practical purposes “they ain’t makin’ any more of it.”

Of course, I’ve been oversimplifying, by assuming that a revival of large-scale helium LTA would occur in the first place. In fact, no prudent investor would invest in commercial helium-lift LTA without considering the prospects for gas supply, and with the certainty of price increases and the uncertainty of future supply at any price, he will put his money elsewhere.

The plain fact is that helium is already too expensive. Its 6% gross lift penalty compared to hydrogen comes directly out of useful lift, imposing a net penalty around 20% depending on payload ratio. Its cost constrains airship operations by limiting operating altitude or fullness (hence lift) to avoid valving gas and by forcing operators to operate at very low purity to delay “shooting” gas as long as possible. Both constraints further reduce the economic viability of an already marginal transport medium.

If large-scale LTA is to survive, there will have to be a transition to hydrogen as the lifting gas. The only question that is open is: when? If LTA is ever to be used for transport of goods or people, that revival will have to be based on hydrogen lift. And it must be soon.

The time to prepare the transition is now, while there are people still living who have handled hydrogen in an LTA context, and who can instruct others. Hydrogen is more dangerous than helium, but there is no alternative. There are obstacles to be overcome in using it, and the sooner we start overcoming them the sooner we will have viable commercial LTA. The principal obstacles are:

• Lack of trained personnel.  Solution: train some.

• Lack of insurance cover.  Solution: insurance companies will ensure anything for which they have reliable actuarial statistics. Only experience can produce those statistics. Until they are available, operators will have to self-insure. It has been done before, and it can be done again.

• Government regulations and statutes.  Solution: a stroke of a pen.

Hindenburg Syndrome.  Solution: education and exposure.

Priced out of the market, or forced out. Those are the only possible fates of LTA if we persist in considering only helium as a lifting gas. It is, in the current jargon, unsustainable.


February 13, 2010

Book Review: Leichter als Luft

Filed under: Aeronautics,Engineering,Lighter than Air,Propulsion,Structures — piolenc @ 5:37 pm

Leichter als Luft

Transport- und Traegersysteme
Ballone, Luftschiffe, Plattformen

by Juergen K. Bock and Berthold Knauer

reviewed for Aerostation by F. Marc de Piolenc

Hildburghausen: Verlag Frankenschwelle KG, 2003; ISBN 3-86180-139-6, price: 39.80 Euros. 21.5 x 24 cm, 504 pages, single color, many line illustrations and halftone photographs, technical term index, symbol table, figure credits, catalog of LTA transport and lifting systems.

Summary of Contents

1. General fundamentals of lighter-than-air transport and lifting systems
2. Physical fundamentals
3. Design of airships and balloons
4. Reference information for construction
5. LTA structural mechanics
6. Flight guidance
7. Ground installations
8. Economic indicators
9. Prospects


A. Time chart
B. Selective type tables of operating lighter than air flight systems
C. Development concepts of recent decades
D. Systems under development or under test
E. Author index
F. Table of abbreviations
G. Symbol table
H. Illustration credits
I. List of technical terms
J. Brief [author] biographies

In LTA, which has seen only two book-length general works appear since Burgess’ Airship Design (1927), comparisons are inevitable despite a language barrier. It is therefore quite pleasing to note that the authors of this book have consciously set themselves a task that complements the work embodied in Khoury and Gillett’s Airship Technology1. While Khoury’s work is a review of the current state of the art, the present book provides

“…a scientific, technical and economic basis for a methodical, consistent procedure in developing new lighter than air flight systems as well as a catalog and appraisal of prior solutions and achievements.”

as stated in the preface by Dr.-Ing Joachim Szodruch of the DGLR. This is amplified in the authors’ Foreword:

“The observations contained herein are future-oriented and encompass without euphoria the current state of science and technology.”

This is in contrast to Khoury and Gillett’s introduction to Airship Technology, which reads in part:

“This book is intended as a technical guide to those interested in designing, building and flying the airship of today.”

The body of the book is completely consistent with its stated purpose, looking always toward the future and emphasizing how things should be done rather than how they have been done. Where examples of actual hardware and operations are needed, they are drawn from the most recent available, and meticulously documented.

Considering the authors’ long association with the LTA Technical Branch of the DGLR, it is not surprising to find that much of the material, and many of the collaborating authors listed in the Foreword, are drawn from the many Airship Colloquia held by that Branch over the years. Yet the style is seamless; there is nothing to suggest to this admittedly non-native reader where one contribution ends and another begins; style is consistent from paragraph to paragraph, and across chapter boundaries. What is more, the authors seem to have made a conscious effort to make the text accessible to non-Germans by keeping sentence structure simple and straightforward. The three-column-inch sentences, gravid with nested subordinate clauses, so beloved of the Frankfurter Allgemeine Zeitung, for example, are not to be found here, much to this reviewer’s relief.

It is compulsory to say something about the thoroughness of the book’s coverage. It is, however, difficult to formulate a “completeness” criterion for LTA, which is now more than ever an open-ended field, in which-as the authors correctly point out-the possible types are still far from exhausted, despite the antiquity of aerostatic flight. It is to the book’s credit that its presentation, too, is open-ended; that is, the authors have avoided presenting the usual narrow typology of LTA craft and their almost equally narrow applications. Instead, and in keeping with modern practice, they take a systems approach to LTA, situating it within the field of aeronautics and providing the tools that the reader needs to translate his own requirements into appropriate technology.

The only omission that might be considered significant concerns tethered aerostats: the authors appear to have neglected both tethered-body dynamics and cable dynamics in their technical and mathematical treatments. Tethered balloons as a type are mentioned, but that seems to be all the coverage that they get. Admittedly, long-tether applications have poor prospects because of potential operational and safety problems, but short-tether dynamics have caused problems in some applications that are relevant, including balloon logging, so coverage of that end of the scale would have been welcome. Tethers also play a role in some existing and proposed stratospheric balloon systems, including the exotic NASA Trajectory Control System or TCS.

This, however, is the only flaw in an otherwise comprehensive LTA design/analysis toolkit.

One especially notable and praiseworthy inclusion is subchapter 1.4 regarding regulation and certification. This topic, though a concomitant of any aeronautical project, is one that most techically oriented authors would prefer to avoid or to give only summary treatment, but Bock and Knauer dive into it fearlessly, setting forth in considerable detail, and with the help of flowcharts, German, Dutch, British and American certification categories and procedures, with reference to the governing documents. Not surprisingly, there is more detail about the German process, with which both authors have considerable experience. They also review the history and evolution of the European Joint Airworthiness Regulations (JAR), which are keyed to—-and sometimes based on—-corresponding Parts of the US Federal Aeronautical Regulations (FAR).

They do not flinch even from discussing certification costs and fees. Although they admit that the general policy of regulatory authorities is to require payments to government from the applicant that offset the costs incurred in administering and examining a certification application, they conclude that, compared with the cost of development of an airship, the regulatory fees charged are of only minor importance. It is not clear whether they consider here the costs incurred by idling the works while some bureaucrat makes up his mind! Perhaps it hasn’t happened to them…

Typography, binding and book design

The basic layout is in two columns, with generous leading and gutters, making the somewhat smaller than usual typeface easy to follow and to read. Equations are set in a slightly larger, bolder font and occupy the full width of the page, avoiding a common legibility problem with two-column layouts. There are no drop-outs to be found anywhere. The eggshell-white paper is thin enough to keep the book’s 500-plus pages within a thickness of less than an inch (2.5 cm), yet the paper is completely opaque, without bleedthrough and with perfect reproduction of fine-screen halftones. A color section is mentioned in the table of contents, but all pages in the review copy are single-color. The cover is paper, rather than cloth covered, printed front, spine and back in white on a dark blue background (reproduced in reverse for this review). This type of cover is less durable than the traditional cloth, but is in widespread use for textbooks and technical works despite this.

Second (English) Edition

Work is now in progress on a second edition, which will be published in English by Atlantis Productions. Note that this will not simply be a translation of the first, German edition but a new work, composed ab initio and including whatever revisions might seem appropriate considering response to the first edition. Both of the authors have a very strong command of English, so there is no reason to fear the damage that some excellent German technical works have suffered at the hands of translators (Eck’s treatise on Fans comes to mind).

A “must have” in either language.

1 While a more thorough and detailed comparison of the two books would have been desirable, it is unfortunately not possible, as Aerostation never received a review copy of Airship Technology. Such comparisons as can be made here are based on brief access to that book during a consulting stint.

This review originally appeared in Aerostation, Volume 27, No. 3, Fall 2004

January 15, 2010

Research Resources: Lighter Than (LTA) Air Flight

Return to ABAC Page

LTA Research Resources

compiled by F. Marc de Piolenc

To suggest resources not listed here, or to correct errors, please leave a comment below.

Libraries & Special Collections
Name/Collection Address/Telephone Description
Embry-Riddle University Library Daytona Beach, FL 32014
(904) 239-6931
Northrop University Library—
Pacific Aeronautical Collection
5800 W. Arbor Vitae St.
Los Angeles, CA 90045
(213) 641-3470
Documentation on West Coast aeronautical activity, including LTA. Photographs.
National Air and Space Museum Library Smithsonian Institution-A157203
Washington, DC 20560
In addition to its collection of books and documents, NASM also has an extensive graphic archive, much of it digitized.
University of Akron
Arnstein Collection
The University of Akron
University Libraries
Polsky Building
225 South Main Street, Room LL10
Akron, OH 44325-1702
Tel: (330) 972-7670
Fax: (330) 972-6170
email: jvmiller@uakron.edu
Papers of the late Dr. Karl Arnstein of Goodyear-Zeppelin Corp. Papers have been listed; the lists and some photographs are available on the University’s Web site. See Internet Resources for on-line access and use information.
University of Texas

Charles E. Rosendahl Collection

Douglas H. Robinson Collection

The University of Texas at Dallas
Special Collections Department
P.O. Box 830643
Richardson, Texas 75083-0643
Phone: 972-883-2570
Dr. Erik D. Carlson, Department Head for Special Collections (carlson@utdallas.edu)
Papers of the late VAdm Charles Rosendahl and the late author Douglas M. Robinson were donated to UT.
Zeppelin Archive

(Luftschiffbau Zeppelin GmbH)

c/o Zeppelin Museum
Seestraße 22
D-88045 Friedrichsafen
Contact: Barbara Weibel (waibel@zeppelin-museum.de)
Phone: 0049 7541 3801 70
Fax: 0049 7541 3786 249
Housed in the same building as the Zeppelin museum, this is a Zeppelin/LTA archive with about 500 linear meters of papers, 7,000 plan sheets and about 17,000 photographs. Another large collection, of books, is housed with the Zeppelin Company archives. Hours are Tuesday to Thursday 9-12 am and 1-5 pm, but an appointment is required.

Name Address Description
Zeppelin Museum Friedrichshafen Seestraße 2288045 Friedrichshafen


Tel: +49 / 7541 / 3801-0

Fax: +49 / 7541 / 3801-81


The Zeppelin museum. Open May-October Tuesday-Sunday, 10 am
to 6 pm; November-April Tuesday-Sunday, 10 am to 5 pm
Aeronauticum, Nordholz

Deutsches Luftschiff- und Marinefliegermuseum

Peter-Strasser-Platz 3, 27637 Nordholz

Postfach 68, 27633 Nordholz

Telephone: 04741-941074

Telefax 04741-941090

Email: info@aeronauticum.de,


Located at the site of a former military airship base; collaborator
of the Heinz Urban museum at Meersburg mentioned elsewhere in these pages.
Has custody of the archives of the now-defunct Marine Luftschiffer Kameradschaft.

1 March-30 June and 1 Sept-31 October: M-Sat: 1300-1700

Sun and holidays: 1000-1800

1 July-31 Aug: daily 1000-1800

26 Dec-10 Jan: daily 1100-1700

Other times: open for groups by appointment

New England Air Museum Bradley International Airport

Hartford, Connecticut


…a true gem and a little treasure of LTA stuff. They have displays
and materials on the Hindenburg, various balloons, a CM-5 engine
nacelle (French WWI airship used by US), a large model of the R-100, a
Packard engine designed for the Shenandoah, and the K-28 control car undergoing
restoration. [Airship-List]
Point Sur Lighthouse Big Sur, California


Lighthouse has a nice display of Macon material, model, diagrams
of where it lies, a short video and overall is worth the trip.
Maritime Museum of Monterey
Stanton Center
Monterey, California


..has a good little area on the Macon, including some recovered
artifacts, models, and multiple videos which include interviews with Gordon
Wiley, son of CDR Wiley. Well worth a visit if you are in the area. [Airship-List]
Moffett Field Moffett Field

(near Sunnyvale, California)


The hangar looks great. You can sometimes gain entrance through the
small museum. This museum is a real treasure. Carol Henderson and her docents
have assembled the most impressive museum I have ever seen. It truly rivals
any professionally run museum such as Smithsonian ones. [Airship-List]
Deutsches Museum Museuminsel 1

D-80538 München

Tel: (089) 2 17 91
Fax: (089) 2 17 93 24

Answering machine: (089) 2 17 94 33

Covers all fields of technology, but reported by Siegfried Geist to
have “a worthwhile section devoted to LTA.” Open daily (except holidays)
from 9:00 am to 5:00 pm.
Stadt Gersthofen Ballonmuseum Bahnhofstraße 10

86368 Gersthofen

Tel: (0821)2491 135 or 101

Five floors of ballooning history, technology and artifacts. Videos
of current aerostatics activity, and a special exhibit on balloons as a
decorative theme. Open Weds 2-6 pm; San, Sun and holidays 10 am to 6 pm.

Meersburg am Bodensee

Schloßplatz 8

D-88709 Meersburg am Bodensee


Tel: 07532 7909

After hours: 07532 41042

Small private museum run by Heinz Urban, specializing in technical
Zeppelin artifacts. Collection includes a spark transmitter from a naval
Zeppelin, the complete bomb-release panel of LZ6 and many other technical
items. Open March through mid-November daily, 10 am to 6 pm. Guided tours
by appointment.
Albert-Sammt-Zeppelin-Museum Hauptstraße

D-97996 Niederstetten


Small museum honoring a commercial Zeppelin officer of local birth
who rose from helmsman in 1924 to command of LZ130. Multimedia presentation
on Zeps.

Zeppelinheim (near Frankfurt/Main)

Zeppelin-Museum Zeppelinheim
Kapitän-Lehmann-Straße 2

63263 Zeppelinheim


A small Zeppelin museum housed in a municipal building in a Frankfurt
suburb, near the airport. When I was there in ’80, the Curator was an old
Zeppelin-Reederei Maschinist.
Zeppelin Museum
Manfred Petersen

Museerne iTønder

Kongevej 55,

DK-6270 Tønder

Tel:. (0045) 74 72 26 57 * (0045) 40 59 62 41

This is the old “Tondern” Zeppelin base.
Central Museum of Aviation & Cosmonautics Krasnoarmeyskaya 14



NAS Richmond Museum

c/o Ford U. Ross

11020 SW 15th Manor

Davie, FL 33324


Display commemorating Navy blimp ASW activity in World War II
Soukup &
Thomas Balloon Museum
700 N. Main St.

Mitchell, SD 57301

Tel: (605) 996-2311

Fax: (605) 996-2218

Museum Director, Becky Pope : beckyp@btigate.com

Museum of Flight East Fortune Airfield

North Berwick

East Lothian. EH39 5LF


Tel: 062 088308 or

0131 225 7534

Models of the R100 and R34, plus the Lion Rampant Standard which adorned
the front of the R34.  There is also a plaque commemorating R34’s
[transatlantic] flight  to be seen [East Lothian was the point of
departure]. Several other LTA items are featured, including film excerpts,
handouts and bits of Zeppelin frame. [Ian Paterson]

Name Address Description
of Balloon & Airship Constructors
P.O. Box 3841

City of Industry, California 91744

email: abac@archivale.com

Publishes quarterly Aerostation (now part of LTAI’s Airshipworld


Airship Heritage Trust c/o Shuttleworth College

Old Warden Park

Biggleswade, Bedfordshire SG 18 9EA


Tel: +44 (0)1767 627195

Charitable organisation with a large collection of airship artefacts
and photographs relating to the

British Airship Programme from its early days at
the turn of the century to the Skyships of the


The Airship Association
The SecretaryThe Airship Association

6 Kings Road,

Cheriton Folkestone, Kent CT20 3LG England.

Email: info@airship-association.org

Premier UK-based LTA association. Publishes the quarterly magazine
Balloon Federation of America Box 400

Indianola, IA 50125

Tel: (515) 961-8809

Fax: (515) 961-3537

Publishes bimonthly Balloon Life
The Bombard Society 6727 Currant Street

McLean, VA 22101

Association of upmarket hot-air ballon operators.
Experimental Balloon
and Airship Association
Brian Boland

PO Box 51

Post Mills Airport

Post Mills, VT 05058

Free membership for anyone interested in experimental balloons or airships
Fédération Française de l’Aérostation 3 bis, square Antoine Arnauld
75016 Paris


LTA Society Box 6191


2000 Republic of South Africa

Japan Bouyant Flight Association

Kyoritsu Kenkyru

402 Hitotsumatsu Bldg 1

2-3-14 Shiba Daimon, Minato-ku




The Lighter Than Air Society 1436 Triplett Blvd

Akron, OH 44306

Tel: (847) 384-0215 (Robert Hunter)

fax: (330) 668-1105 (Attn: E. Brothers)

Publishes Buoyant Flight
National Balloon Racing Association Rt 11, Box 97

Statesville, NC 28677

(740) 876-1237

Naval Airship Association 901 Pillow Drive
Virginia Beach, VA 23454

(757) 481-1563

Publishes newsletter The Noon Balloon
Scandinavian LTA Society Drevkarlsstigen 2-4


S-191 53 Sweden

Zeppelin Kameradschaft Kapitän-Lehmann Str. 2

Zeppelinheim 6078


Internet Resources
World Wide Web (WWW) Sites
Name Description
of Balloon and Airship Constructors
Direct access to the 1600+ item Library List of LTA technical documents
available as reprints. LL can also be downloaded in ASCII or PDF format.
Links to other LTA organizations.
Home Page for Lighter-Than-Air Craft
Hosted at the University of Colorado’s Web server by John Dziadecki,
this is truly the central reference for LTA on the Web.
The Airship Association
Announces AA meetings and other LTA activities, esp. in Britain, plus
membership and subscription information. It has many links to other LTA
Airship & Blimp
Maintained by a young Swiss studying in the USA, it has many links
to other LTA resources, including photo archives.
Balloon Technology Database NASA-funded database of balloon technology, with 2300 documents indexed
as of 1997. Check the “Balloon Technology” box before beginning your search.
Promotions Dirigeables Web site of Paris-based LTA organization. Pages are bilingual (English/French).
Technical Committee

American Institute of Aeronautics and Astronautics

Announces LTA TC activities. Note that permission may be required for
attendance by other than TC members; email first.
Society [USA]
LTA organization with a primary emphasis on LTA history. Web page has
membership information, announcements and an email link.
Naval Airship Association Organization of former US Navy airshipmen dedicated to preserving the
memory of USN airship anti-submarine activity in WW II. Helps maintain
the LTA exhibits at the Naval Aviation Museum, Pensacola, Florida. Page
has announcements and membership information.
University of Akron
Archival Services
Information on how to use the University’s archival services. U. of
Akron is the custodian of the Karl Arnstein Papers.
Alan Gross (Airship Al) Independent consultant and lighter-than-air archivist.
Email Lists


World-wide discussion group about airships sponsored by the [UK] Airship
Association. To subscribe, send email to the address at left with the words
in the message body.


The emphasis in this list is on airships. To subscribe, send an email
message with the word


in the subject line

Balloon Mailing List


Hosts discussion of balloons, both gas and hot-air. To subscribe, send
a message to the address at left with

subscribe balloon [your email address]

in the body of the message.

AirshipList To subscribe, send a blank message to AirshipList-subscribe@yahoogroups.com

Indexes and Bibliographies
Source/Order Number Title & Description
Kent O’Grady

36 Martinglen Way NE

Calgary, Alberta T3J 3H9


email: kogrady@cadvision.com

Index of Buoyant Flight Bulletin – Lighter Than Air Society
260 pp. Cost:

$23.00 US for orders from the USA

$28.00 CDN for orders within Canada

$30.00 CDN for orders from any other country-surface

$45.00 CDN for orders from any other country-airmail

Index of Dirigible – Airship Heritage Trust

23 pp. Cost:

$4.50 US for orders from the USA
$6.00 CDN for orders within Canada

$8.00 CDN for orders from any other country-surface

$14.00 CDN for orders from any other country-airmail

ABAC – Acq. #126 Index of Daniel Guggenheim Airship Institute Report file. This is a different body of work from the papers that appeared in the DGAI’s three Publications. Now if we only knew where to get our hands on the reports themselves…
ABAC – Acq. #301 LTA Society Preliminary Inventory [this is a list of what LTAS donated to the University of Akron, which appears to have retained the Arnstein papers and donated the books to a county library]
ABAC – Acq. #439 Index of LTA Articles in Military Review
ABAC—Acq. #1427 Bibliography of LTA Articles in the US Naval Institute Proceedings 1912-60
ABAC – Acq. #463 David Taylor Model Basin tests of airship models
ABAC – Acq. #713 BuAer Technical Notes, 1916-1924. Another obscure report series.
ABAC – Acq. #802 Index of Aerostation through Volume 7 Number 3 [current volume is 22]. Kent O’Grady (see above) is preparing an up-to-date index.
ABAC – Acq. #946 Index of Airship #s 51-65 (Mar 81-Sep 84)
ABAC – Acq. #1409 Index of US Army Air Corps LTA Information Circulars

Return to ABAC Page

December 5, 2009

Muscle Powered Blimps

Filed under: Aeronautics,Lighter than Air — piolenc @ 4:44 pm

An Introduction to

Muscle Powered Ultralight Gas Blimps

by Robert (“Rex”) Rechs

Rex is a long-time member of the Association of Balloon and Airship Constructors (ABAC), a contributor to Aerostation magazine and an experienced LTA builder, rigger and pilot. This is in addition to his lifelong work in every phase of aviation as both pilot and mechanic.

This volume is intended to be a companion to his Building Small Gas Blimps, but can be read alone if you do not plan to build this kind of machine, but only want to learn about it.


Section Title Page
Foreword 1
Introduction 2
Acknowledgments 2
Ultralights 3
History 5
Design Considerations 35
Details and Compromises 47
Ergonomics 87
Rocket Science for Pedal Power 87
The White Dwarf man-powered blimp 140
The Brazilian Dirigible Caloi 179
Vintage Designs 186
Shimano Bicycle Parts Catalog 190
Contacts 210
Bibliography 211
Related Books 212
Organizations 213
Conclusion 214
About the Author 215

Softbound – price: $40 (US currency).


Order on-line

Build Your Own Gas Blimp – really!

Filed under: Aeronautics,Lighter than Air — piolenc @ 4:21 pm

Building Small Gas Blimps


by Robert (“Rex”) Rechs

Rex is a long-time member of the Association of Balloon and Airship Constructors (ABAC), a contributor to Aerostation magazine and an experienced LTA builder, rigger and pilot. This is in addition to his lifelong work in every phase of aviation as both pilot and mechanic. There is probably not another individual on the planet who could have put together such a complex and comprehensive book project.  First published in the late 70’s and extensively revised in 1997, this book was published and promoted exclusively by its author until recently, when he kindly offered the publishing rights to ABAC (copyright remains with the author and ABAC’s use is nonexclusive; for permissions, contact the author directly at r.recks@juno.com).  The book includes detailed lists of materials, parts and suppliers. It is extensively illustrated.

Building a blimp – any manned aircraft, for that matter – is a non-trivial undertaking. What is remarkable about this book is that it actually puts the task within the reach of a determined and patient amateur builder.

ABAC’s edition has essentially the same contents as the 1997 revision. Changes made by ABAC are primarily cosmetic: we’ve numbered the pages, added a table of contents and corrected some typographical errors. The new edition is re-published through CreateSpace, an Amazon affiliate. Only soft covers are available.


Section Title Page
Foreword 1
Preface 2
Outline. 3
Glossary 4
Blimp History 6
Design Criteria 7
Ultralights 9
Standard Type Certification 10
Standard Sizes 11
Materials 13
Workmanship 16
Ground Support 22
Masts 29
Hangars 43
Gondola/Airframe 48
Instruments 70
Instruments &
Engines 82
Ducted Fans 86
2-Stroke Engines—-Suppliers 88
4-Stroke Engines—-Suppliers 89
Propellers—-Suppliers 90
Valves and Pressure System 91
Fins 102
Envelopes 125
Fabric & Webbing—-Suppliers 138
Assembly Procedure 145
Bibliography 153
Airship Fin & Rudder Loads
(BuAer LTA Design Memorandum
No. 169)
Gas Airship Parts—-Suppliers 160
Catalog Section. 161
Airship Technical Notes. 185

Soft cover – price: $40 (US currency).


Order on-line

Model Hot-Air Blimps, a cheap intro to LTA

Filed under: Aeronautics,Lighter than Air — piolenc @ 2:43 pm

Model Hot-Air Blimps: How to Build and Fly Them

by Don James

The ABAC gets many inquiries about plans, kits and books for building model hot-air balloons and airships; some even want to build gas free-flight or RC balloon or airship models. On the gas blimp side of things, we don’t hesitate to recommend the excellent Peck Polymers products (nope, we’re not stockholders!), but for our mostly young inquirers on limited budgets we have not had much to offer.

Enter Don James, founding member of ABAC, graphic artist and perennial LTA enthusiast. In 1980 he and ABAC’s then-President George Wright prepared a 20-page booklet for publication by ABAC. Urgent personal business forced the book to be shelved. The master was misfiled in a folder marked “Promo Pamphlets, etc.” and that was that until Yours Truly, trying to put order in the files, stumbled across it.

Don had set out to provide his own children with a cheap and safe pastime that would teach skills and provide instruction, along with hours of fun. The result was an extensive series of free-flight hot-air blimps made of cheap, commonly-available materials and requiring only ordinary tools for construction. The manual that he prepared based on his experiments is extensively illustrated and provides step-by-step instructions not only for building, but also for designing model blimps. For those who don’t want to design their first project, plans for Don’s “Alpha Blimp” are provided in a tabloid-size centerspread. Instructions for building the “firepot” or heat source, which burns old newspaper, are also included. Inflation and flying directions are copiously illustrated, and the final section diagrams modifications for adding a small model-airplane engine for powered flight.

The book has been re-typeset using the desktop publishing technology that was more or less a dream in 1980. Don’s excellent line drawings and well-exposed b&w photos of his own ships have come through in fine shape and have simply been scanned and incorporated as is. Thirty pages, 6″ x 9″ softcover book, dwgs, photos. US $14 postpaid.


  • Order on-line, through Amazon/CreateSpace, using your credit card.

Can You Really Build a Hot-Air Balloon?

Filed under: Aeronautics,Lighter than Air — piolenc @ 2:12 pm

The answer is a qualified “yes.” Here’s what the rigger who literally wrote the book on this subject has to say in the Foreword to his three-and-a-half-volume compendium Build Your Own Balloon:

“This book has been prepared as a guide for the aspiring balloon owner who does not realize the many considerations and details that go into its construction. This book has not been written to encourage individuals to undertake such a  project, but by explaining engineering details it is hoped that you will consult a commercial manufacturer of FAA Type Certificated sport balloons for quality made equipment.

It is realized that many readers will give serious consideration to homebuilt construction; which is, of course, a noble undertaking. Not however without the pitfalls of high cost and poor balloon life; or worse yet, unsafe equipment that the FAA may not let you fly, or may subject to severe operating limitations.

So yes, it can be done, but not just anybody should do it. The author quoted above makes it clear that most of the people who read his book should probably NOT undertake the construction of a balloon. Traits required to do the job successfully are persistence, patience and above all the ability to critically evaluate one’s own work, or at least to listen with an open mind to constructive criticism by others.

Few things look simpler than a hot-air balloon. There’s this big bag filled with hot air, a basket underneath, something to provide heat (where did I put that old camp stove…?). No problem, right? All that’s left to procure is the sandwiches and Champagne.

In fact, a thermal balloon draws on a wide range of skills, from harness-work to welding, and an equally wide range of knowledge from trigonometry to aerostatics to navigation. No matter how much you already know, there will be skills to be acquired and tasks to be contracted out, and you had better be prepared to ruthlessly throw away your own first efforts and start over, because your life will depend on your unwillingness to compromise quality.

Yet even the majority who take things no further than buying the book will learn much that is helpful about the sport of thermal ballooning and about the critical design points of balloons and their support equipment. Balloons are not cheap – that’s the motive for considering building one yourself – and the ability to critically evaluate somebody else’s work could save hundreds, perhaps thousands of dollars, and maybe a life or two.

“Balloon Books”

Build Your Own Balloon Vols I-III + Appendices

Copyright 1996 A.B.A.C.

Compiled by a member of the Association of Balloon and Airship Constructors (ABAC), a licensed balloon and airship pilot, rigger and constructor, these books assemble in one three-volume set the information essential to any amateur considering the construction of a hot-air balloon. They include detailed lists of materials, parts and suppliers. The Appendices contain a brief discussion of gas balloons.


Volume I – Design Criteria contains engineering and safety data. Includes international standards, a review of the state of the art and many time-saving ideas and techniques. (180 pages)

Volume II – Materials & Suppliers contains a comprehensive list of components, specifications and prices [note: prices will be out-of-date], plus information on how and where to order. (206 pages)

Volume III – Plans & Construction contains detailed production drawings, assembly instructions and pictures of most components. (175 pages)

Appendix I – Notes on ultralight hot-air balloon construction.

Appendix II – Notes on spherical gas balloon construction.
[Appendices are bound together in one thin volume, 64 pages]

A word of warning: these books are crudely produced. They are sold for their information content, not their beauty!


Order on-lineOrder on-line through Amazon/CreateSpace

Volume 1 ($30): https://www.createspace.com/5854671

Volume 2 ($30): https://www.createspace.com/5875635

Volume 3 ($30): https://www.createspace.com/6393966

Appendices ($20): https://www.createspace.com/6396032

December 3, 2009

Book Review (fiction): ZRS, by Rowan Partridge

Filed under: Aeronautics,Lighter than Air — piolenc @ 7:09 pm

Review of ZRS

by Rowan Partridge

Reviewed by F. Marc de Piolenc, ABAC. This review first appeared in Aerostation, Volume 24, Number 3, Fall 2001.

Published by Atlantis Productions, P.O. Box 700, Edgewater, Florida 32132-0700, USA. Softbound, coated cover. $25.00 + postage for the printed version, $10 for the ebook version on CD-ROM (in Microsoft Reader format).

A few days ago my post office box was graced with review copies of Rowan Partridge’s opus and Rich van Treuren’s Hindenburg: the Wrong Paint.., which reached my outpost of civilization in the southern Philippines with amazing speed. I started with ZRS, figuring that it would be the more difficult to review. It is after all a first work of fiction, and privately published, which in my sad experience portends a very difficult “read.” To my surprise and delight my fears were unjustified, and I raced through the book, pausing only for food, a few hours of sleep and the odd marginal note. The book was a damn’ good read, as it turned out, and I would have considered it money well spent if I had paid the list price. I cannot account for the excellent quality of this book, because I know nothing of the process of its production. Perhaps Mr. Partridge had the services of a good novel editor or book doctor; perhaps he is simply a very gifted writer – one who has the rare ability to look critically at his own work. That question will have to be answered by somebody else. Suffice it here that the results are worthwhile.

The two-dimensional characters, jerky action and implausible plot line that are “par for the course” with much privately published work (and an unjustifiably high percentage of “mainstream” publishers’ offerings as well) are absent. Indeed, Partridge takes on a very difficult characterization – that of co-protagonist Susan Briars, née Thornton – and pulls it off with riveting efficiency. Suzie emerges as a very difficult character to like or to identify with, but very easy to believe. Her husband, the Commanding Officer of the airship Long Island, is not quite as well developed; we see him mainly through Suzie’s eyes at the beginning of the book, and through his actions and utterances under fire as the plot develops.

Not surprisingly, considering the author’s citizenship, the real hero of the book is an Australian Naval officer originally detailed to observe US Navy LTA operations, who ends up filling an operations slot on the Long Island after Pearl Harbor, and much of the climactic action of the book centers on Australia.

The book is billed as an historical novel, but the label doesn’t quite fit. The canons of historical novelry require that pivotal historic events not be tampered with, preserving the broad outline of history as it happened. The fictitious characters and action have to be embedded in that unalterable matrix. The “history” of the world in which ZRS takes place, on the other hand, deviates radically from that of our universe, which puts the novel in the genre known as “alternate history.” Yet even that newly-recognized genre has its canons, which cannot be violated without taking the risk of negating the willful suspension of disbelief that is the core of the interaction between a novelist and his readers. Ideally, altering a single pivotal event or circumstance must give rise, plausibly, to the all the other differences between the novelist’s universe and that in the history books, and Partridge has almost attained that ideal.

His hypothesis is simply that the demise of rigid airships was due largely to bad luck compounded by hubris. If that postulate is accepted, then it is not difficult to see the presence or absence of key personalities – combining familiarity with the technique of lighter than air flight, military or political authority, and restraint – as the “driver” of all the key LTA events. Thus by saving one vital LTA figure (and one airship) from early extinction, Partridge works a fateful change in the development of rigid airship operations in the US Naval service.

In the world of ZRS, the Akron‘s encounter with the North Atlantic one stormy night is not fatal, as it was in sad historical fact. Instead, a waterlogged and damaged ship bounces back into the air and limps home, carrying Admiral William Moffett and an important lesson which Moffett will not hesitate to impart with all his authority and vigor. The survival of Moffett, a key figure if ever there was one, has a cascade effect on later events. The Admiral remains a champion of lighter than air development while recognizing the limitations of that technology. On the one hand, he pushes the construction of new ships, both in the corridors of the Navy Department and in the halls of Congress. On the other, he resists pressure to push the ships’ operations beyond their capabilities. In particular, he puts his authority and prestige behind the withdrawal of the damaged Macon from the West Coast fleet problem that would lead to her loss in our world – saving her, too, for another day.

Though nominally retired by the time the action in the book takes place, Moffett still figures as an extremely influential friend and elder statesman of LTA.

Other survivals include the R.101, which returns to the mast shortly after starting off on her maiden voyage to Karachi, the CO refusing to be responsible for the consequences when the overloaded, baulky ship encounters bad weather, and the Hindenburg, which was filled with helium as originally intended, the helium having been released to Germany thanks to the earnest lobbying of Admiral Moffett.

All the saved ships but Akron figure in the plot…as cannon fodder! Macon is destroyed on her mast at Ewa, Oahu, Hawaii, during the Japanese raid on Pearl Harbor; R101 is lost while evacuating wounded soldiers from Singapore (with the Australian officer’s wife, a nurse, aboard), and Hindenburg, now filled with hydrogen to maximize lift and making a liaison/cargo flight to Japan in the service of the deutsche Kriegsmarine, is destroyed by fighters from the Long Island.

With little to criticize on literary grounds, it is time to deal with some technical difficulties.

First, the airship Long Island:

She is an outgrowth (with the emphasis on growth – 12 million cubic feet!) of the Akron and Macon, most of whose salient characteristics she shares: deep frames, inboard engines driving pivoting propellers. But there is a jarring difference. The outer cover is now made of metal – presumably duralumin – bonded to the transverse frames and longitudinals with a mix of rivets and adhesive/sealant. This configuration Partridge calls “metalclad,” but it has no resemblance to the airships developed by ADC, Schwartz or Slate – it is simply a framed rigid airship with aluminum substituted for fabric in the outer cover. All the features of conventional rigids that can be dispensed with in a true metalclad are retained: fabric gas cells, shear wiring, netting and so on, along with their weight and (in the case of the cells) fragility. It is clear that the author is aware of at least some of the difficulties this hypothetical airship type presents, because he has Susan Briars (an MIT- and Stanford-trained engineer and a convert to LTA) criticize it bitterly. It seems, however, that the gas cells in particular are needed as plot drivers, as a casualty to two gas cells during airplane recovery operations is the source of the first major peril surmounted by the Long Island and her crew. How this configuration was chosen by the Navy over the much more sensible ones already proposed and proven is not explained, but the simplest surmise is that the unlikely combination of personalities and talents required to create the true metalclad types simply didn’t appear in ZRS‘ universe – and that really is more plausible than what actually occurred! After all, if a novelist had dared to use a character like, say, Fritsche or Slate in his work, he would have had difficulty making him credible to the reader.

Materials:The author refers to a sandwich consisting of a wood core with aluminum facings as “Alclad.” That name is in fact a trademark for an all-metal Alcoa product consisting of duralumin sheet with thin layers of pure aluminum on both faces for corrosion protection. Goodyear’s trade name for their balsa core, aluminum face sandwich material, used in blimp car structures among other places, is Bondolite.

Firearms: The author arms his Australian hero with a “.38 caliber Browning revolver.” To the best of my knowledge, John Browning had no interest in revolvers and spent his entire career on magazine-fed weapons.

[Note (December 2009): I have since learned that the Fabrique Nationale d’Armes de Guerre in Belgium, which produced and marketed many of Browning’s designs, obtained his permission to market a line of revolvers under the Browning name, even though he had no hand in their design. I don’t know whether any of them were chambered for a .38 caliber cartridge, but there certainly were “Browning” revolvers.]

Language:The lure of naturalistic dialog is almost irresistible, and the author yields to temptation, attributing some rather unlikely modes of speech to his American characters in particular. Naturalistic dialog requires careful research and immersion when operating with dialects other than the author’s own mother tongue, and it is clear that Partridge’s linguistic research could not match the meticulousness of his research into naval and LTA matters. This makes the often bizarre utterances of his characters a bit distracting, at least to an American reader. Of course he is in the good company of many noted British and Commonwealth authors, including Ian Fleming (who has one American villain say “Get the photo?” quite a lot), and even Agatha Christie, despite her American antecedents.

As for the German characters, their speech is straight Katzenjammer, not Hochdeutsch. Herr (or is it Doktor?) “Linstein,” the Goodyear engineer whom we meet briefly, is given to exclamations in “German” that would have had my instructors reeling. It is important in any case to note that real foreign-born educated speakers of English are proud of their ability to speak the acquired language, and are therefore very unlikely to lapse into the mother tongue in the first place, so having Linstein say “nicht verstehen!” is the equivalent in implausibility of having a modern, educated Frenchman yell “sacrébleu!” in conversation with American colleagues (only worse, because “nicht verstehen!” is not grammatically correct). Aboard Hindenburg, things get even more chaotic, as the helmsman of the Kriegsmarine Zeppelin is attributed the Army rank of Gefreiter (private first class or lance-corporal). The author even manages to misspell “jawohl” and “Kapitaen.”

Fortunately for us readers, both episodes are brief, and we are so thoroughly “hooked” by the time these hiccups occur that they make very little difference to the enjoyment of the book as a whole. The contrast between the photographic accuracy of the Long Island, her crew, ranks, positions and procedures, on the one hand, and the casual treatment of their German opposite numbers, on the other, is jarring nonetheless.

Plotting is little short of ingenious. The author has somehow managed to get one ship involved in nearly all the major events of the early part of the Pacific war: Pearl Harbor, the evacuation of Singapore, the Japanese raids on New Guinea and northern Australia, the Doolittle raid on Tokyo and the battle of the Coral Sea which closes the book. Only the Philippines get left out. He does this without obvious effort, the plot flowing smoothly and without resort to fantastic coincidence. One artifice in particular that he has not resorted to is making the ship “charmed” or invulnerable. Long Island is nearly lost early in the book and has to undergo extensive repairs Stateside; she ends her career draped across the deck of the carrier Lexington, riddled by Japanese airplanes in the Coral Sea battle.

Well worth the time and effort required to obtain a copy, this one is a “keeper.”

Book Review: An Engineering History of the ZRS-4/5 Fin Design

Filed under: Aeronautics,Lighter than Air — piolenc @ 6:52 pm

Review of: An Engineering History of the ZRS-4/5 Fin Design

by Jeffrey Cook

Reviewed by F. Marc de Piolenc

This review first appeared in Aerostation, Volume 21, Number 2, Summer 1998, which was incorporated in issue no. 36 of Gasbag, the journal of the [New Zealand] Lighter Than Air Institute.

Published by the Author:

Jeffrey Cook
1857 West Aspen Avenue
Gilbert, Arizona 85233

1997. 85 + vi pages, hardbound, 8 3/4 x 11 inches, summary, references, illustrations,4 appendices. Price is $25 US in the USA, Canada and Mexico, $30 US outside North America

This book is dedicated to the memory of Donald Woodward, who contributed to the author’s research and would have reviewed the resulting work for ABAC. Don was one of perhaps two or three people in the world qualified to pass on the validity of the author’s conclusions; this reviewer will have to be content with discussing presentation and plausibility.

The book is true to its title. It is a concise and (so far as this reviewer can determine) complete history of the design of the fins of the U.S. Navy rigid airships Akron and Macon. As such, it covers not just the procedures that were followed, but the key influences on the designers that led to the adoption of those procedures. As such, it can be read as a capsule history of an important phase of the design of light metal structures, as actualized
in (and to some degree actuated by) the design of those critical and ultimately fatal structures.

But it is unlikely that Cook, or anybody else, would have felt any compulsion to write this work if the structures in question had not been blamed for the loss of one of the ships. With the wreck of the Macon lost in deep water and beyond the reach of then-available salvage techniques (her remains were found in 1990), it was inevitable that there would be controversy concerning the exact mode of failure and the critical flaw that doomed the ship and the US Navy’s rigid airship program. It is into this critical-flaw controversy that Cook has bravely waded, reaching (and clearly and forcefully expressing) his own conclusions concerning the identity of the critical factor leading to the loss of the Macon.

Before discussing the substance of the book, a few words about format, typesetting and printing. The book is self-published and the author did the typesetting and page composition himself as well, so he is responsible for the degree to which these contribute to or detract from the organization of the book. The print quality is good, and the author’s two-column layout and generous leading make the text easy to follow. The 12-point serif type font used throughout is also legible and comes through very well in the impression, with no drop-outs, ligatures or smears.

The one truly deplorable feature of the book’s layout is that all illustrations are placed in a section of their own toward the end of the book. Having worked in desktop publishing for twelve years and encountered many of the same problems experienced by Cook, this reviewer cannot help sympathizing with this approach. It is in fact extremely difficult to arrange pictures and words together on a page in a way that is logical, consistent and visually pleasing. If the text is divided into columns, the difficulty increases. Constraining the illustrations to either column or page width has an unfortunate effect on the legibility, appearance and usefulness of many figures, while leaving them at their optimum sizes makes text flow awkward. Nevertheless it is always wrong to organize a book for the publisher’s convenience rather than the reader’s, and so one cannot help wishing that the author had made the (admittedly considerable) extra effort required to put the figures with the text that they support.

A spell-checker would have been helpful, as creative spelling (e.g. “beaurocracy” in a section heading, “Burghundy” and “Wiezen” on page 41) and typographical errors have escaped proofreading. That said, it must be noted that the quality of the photos is consistently excellent, a great deal of trouble having obviously been taken to make it so. The line drawings suffer from drop-outs in the fainter lines, but fewer than this reviewer would expect, considering the variety in the originals and the sometimes extreme reductions required to give illustrations of publishable size. Graphs, charts and tables are all clear.

The one significant and staggering omission from the illustrations is that there is no drawing of the aft hull and fin structure, which is the focus of the entire book! Assuming that there was a compelling reason for that omission, a description of the structure in question and of the frame numbering system would have been welcome. The one-page Introduction concisely exposes the purpose and organization of the book, but also self-deprecatingly (and inaccurately) describes it as “…written in a style which combines the abstract miasma of an academic thesis with the disjointed tedium of a government contract report, while cleverly omitting anything that might be considered even remotely interesting.” In fact the organization of the book is well thought out and the writer’s style is quite free of the disagreeable elements that he attributes to it.

Cook begins his story just after World War I, during the transition from externally-braced fins with nearly no inherent bending strength to cantilever and semi-cantilever fin designs. We are thus spared any attempt on the author’s part to summarize the entire history of rigid airship development to that point. Cook’s approach immerses us in the story at just that point at which the engineering issues that are the focus of the book came to the fore.

As the story opens, this reader at least is struck not only by the absence of knowledge of true fin loads possessed by the Zeppelin designers, but also by their nonchalance in the face of this ignorance. It does not accord with the popular image of systematic, penetrating German engineering research. Apparently, the Germans (at least the Friedrichshafen crowd; little is said about Schütte) were content with turning tests that gave gross hull bending moments, but no details of fin forces and their distribution. The result was fins that were understrength with respect to average pressures and dangerously weak with respect to the peripheral suction peaks that were left completely out of consideration. The short and unhappy careers of the ships ceded to the Allies as spoils of war are thus easily explained. It is clear that such success as the wartime Zeps had was due to alert aerology and skillful ship handling, rather than to design. In the immediate postwar years, with the German effort temporarily shut down, the scene shifts to the Allies, and particularly to Britain and the USA, newcomers to rigid airship design but with aggressive development programs staffed by competent researchers eager to know the truth. A pattern is soon established in which operational experience with one airship points out the need for revised load estimates. New tests are then ordered in support of the design of the next generation of ships. The test results are delayed (data gathering and data reduction were, by current standards, prohibitively slow and labor-intensive), arriving after the design is frozen based (necessarily) on guesses. The new guesses prove inadequate, and the cycle repeats. Thus Burgess’ 1920 average fin pressure estimate of 0.75 lb/ft2 gives way, after the R.38 (ZR-2) disaster and the C-7 turning tests, to 40% of dynamic pressure or 1.7 lb/ft2 on C-7, with peaks four times as great. Another consistent pattern is disregard of theoretical aerodynamic calculations if the results did not fit the designers’ current estimates. Clearly the empiricists had a stranglehold on airship development at that time, perhaps because aerodynamic theory, then undergoing rapid and successful development, still carried the taint of 19th century inadequacy. This is unfortunate, because in the early Twenties it appears that the theoreticians were well ahead of the empiricists. Cook notes that independent calculations made in Italy, Britain and the USA had all predicted turning loads much higher than those estimated for ZR-1 and ZR-2. These were simply ignored. The taint of theory seems to have also affected consideration of model-scale tests, however carefully and consistently executed. Thus Cdr. Fulton’s dismissal of the 1931 NACA tests on the 1/40 scale model, which clearly showed that the pressures and their distribution were very much different from what had been assumed. Fulton’s demand that the tests be done over effectively removed them from consideration. When the confirming test results were published in 1937, they were too late to contribute to anything but a post-mortem.

Despite the precariousness of contemporary knowledge of the atmosphere, its interaction with their fragile craft and the stresses evoked within the craft themselves, the LTA designers of the period (at least in the USA) appear to have projected such calm self-confidence that their work was treated by many laymen directly concerned with airship construction and operation as belonging to an established discipline like naval architecture, rather than one that was extending its reach furlongs beyond the boundaries of what was known. Thus we have the ludicrous spectacle of the Navy contracting officers, Goodyear-Zeppelin Corp. and the Bureau of Aeronautics wrangling over contractual penalties for a weight increase in the aft structure of the projected ships as if they were discussing a new class of destroyer escort rather than an experimental aircraft. This the author sets forth without comment, allowing it to tell its own story.

The specifics of the ZRS-4/5 fin design history yield fascinating tidbits. This reader knew that the fin design had been revised early in the design process, and had always assumed it was for aerodynamic reasons. After all, the new or Mark II fin design had a larger span and a higher aspect ratio. Clearly, this was a late manifestation of the early postwar dissatisfaction with the Zeppelins’ inadequate tail surfaces and consequent “hunting” motion. A higher aspect-ratio fin would give a steeper normal-force curve, hence stronger restoring forces. In fact (and regrettably, as it turns out) aerodynamics was not even considered in the change, whose purpose was to make the base of the lower fin visible from the control car! The change would both increase the steady fin forces and their moments (which the author discusses in detail) and make the fins more vulnerable to the gust transient loads (which are not discussed), and one of the widely-held beliefs considered by Cook is that the change caused the catastrophe by overloading Frame 17.5 (the first to fail in the Macon crash). It seems plausible—the new fins’ forces were taken by only two transverse frames, versus three in the original design. Without reinforcement, goes the argument, the remaining two frames would be overloaded. Cook dismisses this hypothesis with one little-known fact—that Frame 17.5 was in fact reinforced with about 170 pounds of additional material—and a simple and plausible argument namely that any engineer of even minimal competence would have altered the hull design to take the redistributed fin loads. The deep-frame-vs-cruciform controversy is also disposed of, the author stating (correctly) that there is nothing inherently bad or good about cruciform girders (advocated by classic Zeppelin designers) or the deep, inherently stiff frames used in ZRS-4/5, so long as the structural members are properly sized for the loads applied to them.

Fatigue in Frame 17.5 is next in line for consideration. Advocates of this hypothesis (perhaps influenced by Nevil Shute’s novel No Highway) point out that Akron and Macon had roughly the same number of flight hours when they crashed. For the coincidence in flight hours to be meaningful, however, the two ships would have had to have the same load histories, and Akron never had to endure the aerial whiplash over Texas that gave Macon‘s crew the first warning of her fins’—or rather the supporting frames’—inadequacy. Cook also points out that the only kind of fatigue that Macon‘s structure could have experienced is the “low cycle” variety, which came in for much scrutiny in the late Fifties after several airliner crashes. A key prerequisite for low-cyle fatigue is that the cyclic stresses approach the yield point of the material. That in itself would indicate an error in stress analysis or in the assumed aerodynamic loads, so that fatigue, even if it occurred, could not be the root cause of the frame’s failure. This leaves, of the four hypotheses considered, only the last, namely that incorrect assumptions concerning the magnitude and (especially) the distribution of aerodynamic loads were at fault. By thoroughly documenting both the assumptions that were made (including uniform areal load) and the experimental evidence that should have been allowed to alter this picture, the author makes a convincing case for the belief that the forward 1/3 of the fins were much more highly loaded than the designers expected. As most of the excess load would have been forward of the foremost attach point (at the infamous Frame 17.5),there would have been a torque on the attach point in addition to excessive bending, which also accounts for some observations by witnesses. Cook does not ignore the fact that the frame, and not the fin structure, actually failed. The fin should have failed first by design, and the fact that it did not is used to support the fatigue hypothesis. To counter this, Cook brings in the Special (Durand) Committee’s opinion that the stress analysis techniques used were not quite up to handling the complexities of the ZRS’ structures, the “energy” or “least work” method developed later indicating that Frame 17.5 should have been made stronger.

One striking omission from the treatment of fin design in the book is that absolutely nothing is said about the aerodynamic phenomena that give rise to the fin loads, and their peculiar distribution. For instance, the load peaks at leading and peripheral edges are conspicuous in the text and illustrations (and Cook attributes the loss of the Macon to ignorance of them), but leading-edge suction is never discussed. Likewise, the fact that gust loads on fins are much higher during gust entry than when a steady state is established is mentioned in connection with the Daniel Guggenheim Airship Institute’s tests, but the unsteady aerodynamic phenomena that give rise to the effect are not. Gust entry affects not just the total load on an aerofoil, but also its distribution, making unsteady aerodynamics highly relevant. But the author’s discussion is in terms of
an equivalent steady angle-of-attack, which may not be equivalent at all. Not that this consideration would threaten the author’s conclusion; it would in fact reinforce his thesis. It would, however, lessen the culpability of the Macon‘s contemporaries because unsteady phenomena were just beginning to be understood at that time. Unsteady lift might also account for the fact that Macon was de-finned by a gust generally thought not to have been especially severe. In unsteady flow, it is the rate of change of aerodynamic loading (the “steepness” of the gust onset) that matters, not absolute magnitude. The fascinating question of aerodynamically-induced distortion of a poorly-supported outer cover and its reciprocal effect on the fin loads is mentioned in connection with the Shenandoah‘s famous mast breakaway, in which the top fin also collapsed, but not considered further. Presumably, the Macon‘s outer cover was better-supported than that of the Shenandoah. The treatment is purely from the point of view of the structural engineer of that time, whose only reliable knowledge of the loads that he was meant to overcome was empirical, and usually reached him too late to do much good. The result is an implied rebuke to those responsible for designing ZRS-4 and ZRS-5, as if the author were saying “see, if I could figure this out, so could you.” In this, the author disagrees with Don Woodward, to whom the book is dedicated and who believed that fatigue—a phenomenon little known and poorly understood at the time—had played a critical role in the Macon fin failure.

Thorough without being pedantic, well presented and clearly reasoned, this book belongs on the shelf of anyone interested in rigids and their turbulent technical history.

December 2, 2009

Airships in Disaster Recovery

Filed under: Aeronautics,Lighter than Air — piolenc @ 6:24 pm

The Potential Role of Airships in Disaster Recovery

Within the very broad field of aeronautics, dirigible airships occupy a niche that overlaps only slightly the fields of application of other aircraft. On the positive side, their most prominent characteristic – the ability to sustain flight without expending energy – makes them well-suited to missions requiring long endurance. This also allows them to hover over one spot for extended periods if that is necessary; this is impossible for airplanes and requires very high fuel burn rates for helicopters hovering out of ground effect. Airships are also able to operate from minimally prepared bases – possibly no more than a clearing sufficiently large to accommodate the mooring circle. They are able to operate quietly and with low vibration levels, making them good instrument platforms. They can carry bulky equipment, externally mounted, that would impose an intolerable drag penalty on airplanes or helicopters. With suitable equipment, an airship can operate from water with less weight and drag penalty than adding floats to an airplane. Due to low flight speeds, operating airships at night carries less risk than for other types of aircraft.

On the negative side, airships are inherently low speed, low altitude machines – higher speeds penalize payload by requiring large increases in installed power, while higher altitude operation increases both weight and drag by requiring a higher air displacement for a given gross lift. When operating near the ground they are vulnerable to gusts, especially during takeoff and landing. To a greater extent than with helicopters and airplanes, they require a dedicated and well-trained ground crew.

In the immediate aftermath of a large-scale disaster, whether natural or man-made, several needs must be met more or less simultaneously:

1. Medical attention for injured survivors, whether in situ or by evacuation.

2. Identification and sanitary disposal of the dead.

3. Food, clean water and shelter for survivors rendered homeless and destitute by the catastrophe.

4. Repair of damaged infrastructure to restore normality as soon as humanly possible.

Central to successful disaster management and disaster mitigation is thorough planning and coordination of the effort; that in turn requires that the planners and coordinators have accurate and thorough knowledge of the situation in the affected area. With the regular telecom infrastructure down, that knowledge can only come from two sources: radio-equipped aid workers on site, and aerial survey. The first is very accurate and current, but limited in coverage by the difficulty that a human being has in moving about in a devastated
landscape. The second is potentially very expensive if provided by helicopters. Worse, it places information-gathering in competition with airlift requirements, in effect forcing those directing the relief effort to choose between helping known victims and learning who else needs help.

Suitably selected and employed, airships can contribute to the relief effort in the following ways:

1. By taking over the survey and surveillance side of the relief mission, freeing heavier than air machines – primarily helicopters – to carry relief supplies and personnel and evacuate the injured.

2. By serving as communications relays for line-of-sight, low power communications gear, including (with suitable equipment) cellular telephones. For this purpose, antenna arrays can be suspended from the control car, or even larger arrays with large effective apertures
can be carried within the envelope.

3. By serving as platforms for news reporting, preventing the news media from becoming a logistics burden and security risk on the ground.

4. By carrying VIPs on fact-finding tours without hindering the relief operation.

In order for them to operate satisfactorily, however, certain conditions have to be met.

1. The airship(s) employed must have sufficient radius of action to operate from outside the affected area, so that their basing and support requirements do not burden the relief effort.

2. Missions must be planned and monitored with care. Weather, especially, must be monitored and early warning given to airship pilots of hazardous conditions.

3. Air traffic control personnel must be made aware of the limitations of airships; whenever possible, airships should be kept clear of other aircraft. This is usually easy to accomplish.

4. Dispatch and control of airship operations should be entrusted to competent authority familiar with their strengths and limitations; dispatchers must resist assigning missions for which the available ships are unsuited.

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