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# c- subject: FAA-2013-0550 , Requests for Comments, Proposed Airship Design Criteria -, F' I- 

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- ,. '' To: Docket Operations, M-30, U.S. Department ofTransportation (DOT) , 1200 New Jersey ,_j Avenue SE. , Room W12-140 , West Building Ground Floor, Washington, DC**20~99-QO l:**  

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## I: S**~** From: Richard G. Van Treuren, P 0 Box 700, Edgewater FL 32132 , 386-345-4208 Summary: LMZ1M Criteria seeks to comply with FAA Documents " Transport Airship Requirements " and "Airship Design Criteria." The former is quoted in HCC 893. However, two sections ofthe FAA documents disagree with each other, are incomplete, are unevenly applied across buoyant flight, and are outdated. References (1) AIAA Paper " Explosion

- or Fire? Understanding Hydrogen Phobias " By Richard G

. Van Treuren, Jfugen K. Bock, Marc de Piolenc, March, 2013 (attached)
Specific Problem: FAA Document "Transport Airship Requirements" (March 2000) contains TAR 893 , which states: The lifting gas must be non-flammable, non-toxic and non-irritant. However FAA-P-8110-2 " Airship Design Criteria" dated 2/5/95 contains 4.48 Lifting Gas: The lifting gas must be non-flammable. The two documents a) do not agree with each other b) do not address explosivity, the excuse given for Congress to cut funding for military hydrogen-borne flight in 1922 c) seek to exclude hydrogen based on the mistaken beliefhydrogen is flammable without oxygen d) ignore today' s hydrogen- borne flight e) date to a time when the government-created and -subsidized industry served mainly LTA, so helium was both available and affordable f) sidesteps hydrogen ' s role as fuel ; with three times the BTU of petroleum by weight, hydrogen will be part ofmodern airship designs Recommendation: Revise TAR 893 and ADC 4.48 to read: The lifting gas must be free of oxygen. Supporting Documentation : Reference (1) attachedExplosion- or Fire? Understanding Hydrogen Phobias By Richard G. Van Treuren, 1 Jiirgen K. Bock,2 Marc de Piolenc3

These authors believe airships have a solid future ifwe examine popular conceptions concerning the unsuitability ofhydrogen , the history and technicalities ofhelium, and the outlook for both

. Robert' s gastight fabric and Charles ' hydrogen production combined for their first flight in 1783. Witnessing the first balloon in America, Thomas Jefferson speculated it could be used to move things , at least in the wind ' s direction

. About 70 years later French balloonist Henri Giffard perfected a wondrous fly-weight steam engine that propelled his ovoid envelope forward against a slight breeze. Today, visiting French Canada, Henri could operate his free balloons with no problem

. However, if he attempted to use his propulsion in Quebec, he would be in violation of CAR 542

.7 which states : "Hydrogen is not an acceptable lifting gas in airships. " Why does adding propulsion make an ovoid envelope ' s hydrogen unacceptably dangerous ? Regulations should not be arbitrary and are usually written from experience, or as sailors say,
" The Navy ' s safety rules are written in blood

." Some might explain the seemingly random regulation elements by assuming hydrogen was always unacceptably dangerous, but an exception was made only to allow free balloonists in American competition, who could not afford helium ' s rising price, to fly like their European brethren, starting in 2000

. The accident most often cited as the regulation ' s origin is the Hindenburg, which, according to TV and the internet, "blew up with no survivors on its maiden voyage. " But that ' s not it; helium had been used in America for nearly fifteen years when LZ-129 " exploded. " So, why is it so ruled now, when hundreds of balloons and airships had been flying with hydrogen for 130 years? It actually began with the British, who not only first discovered helium from a solar observatory in India, but later tried to extract helium from its natural gas entrapment in Canada

. Englishmen (not French, Germans or Italians) hoped the rare gas would extend the combat life of their tethered observation balloons, the sitting ducks then being regularly shot down on the World War One fronts

. After considerable expenditure on a Canadian natural gas helium extraction facility, the pocket dried up , and effort was abandoned as impractical

- for good reason . The decay of subterranean " granitic" rock Uranium and Thorium, over millions of years , has produced most of the world ' s helium. At or near any deep-seated Precambrian uplifting events , produced helium can move in nitrogen to collect in natural gas pockets

. If , in tum, the same area is also capped by rock dense enough to keep it underground, it is potentially recoverable

. Decades after scientists isolated samples , helium was found in nonflammable nitrogen cleaned from certain mid

-US natural gas pockets

. In 1906 a Dexter, Kansas natural gas well was found to contain 1

.84% helium concentration. Like unstripped nitrogen and argon, it was mainly an annoyance to consumers ofthe cooking gas .

1 AIAA TC ; Editor, THE NOON BALLOON; PO B ox 700, Edgewater, Florida 32 13 2-0700 2 SLTA Engineering.Consulting 3 AB AC ; Editor, Aerostation
American Institute of Aeronautics and AstronauticsWith America' s entry in the Great War on Britain ' s side, exploitation ofTexas helium took place under war conditions in a military atmosphere ; several agencies were involved but none had complete responsibility for helium

. Following a competition between plant design variations using the Joule-Thomson effect (to liquefy heavier components of the gas stream, still in use today), taxpayers funded a large scale facility in Fort Worth to extract helium from natural gas in the Petrolia Field near Wichita Falls , Texas. The Great War ended before a single balloon could be inflated. In spite ofthe considerable expense incurred, no observation balloon was then (or to this date) filled with helium and then attacked with "balloon buster" ammunition

- which, without question, would have brought the doped-cotton contraption down in flames

. The veil of secrecy that was thrown around helium activities in the early days had served to strengthen the layman' s beliefthat it was to be considered with awe and reverence , but continued funding was injeopardy with postwar "Return to Normalcy." Press connections yielded exposure like the 1919 National Geographic article, "Helium, The New Wonder Gas ," but the peacetime military showed no interest in adopting helium for its balloons , since its lesser lift then cost 70 (seventy) times as much as hydrogen. Helium became a solution in search of a problem ; there had been only one fatality in the US Observation Balloon Corps in the entire war. (Lt. Cleo Ross died when the burning balloon fabric fell on his parachute.) Without a death attributable to lifting gas , how could one be convinced hydrogen was too dangerous to use in balloons? Just then, English rigid airship R.38, being purchased by the US Navy, broke in two, resulting in heavy causalities

. Six months later the Italian semi-rigid Roma, purchased by the US Army, lost control and nose-dived into a power wire, also with a large percentage of the crew lost. Neither accident was caused by their lifting gas , nor had hydrogen been a step in either accident's train

. However, the unusually large loss of life prompted a Congressional hearing, seized as an opportunity by the Bureau of Mines ' Dr. Richard Moore

. Quoting BaM ' s Clifford Seibel: " As the Congressional Committee watched, Dr. Moore proceeded with the experiment. Holding a helium-filled yellow balloon at the end of a string, he applied a burning taper. His hand was trembling and the wobbling taper merely seared a spot on the balloon, weakening it enough for the gas to escape with a hissing sound, but without bursting the balloon

. When the taper was applied to the red balloon filled with hydrogen, there was a terrific explosion

. The windows were rocked, and Congressmen raised out of their seats
. . . 'Gentlemen,' he said, ' if any of your boys are flying in military balloons or airships, do you want their ships filled with helium or will you be satisfied if they use hydrogen?'

. . .a member of the group said, ' We can't make the Army and Navy use helium, but we can say that none of the money we appropriate can be utilized to fill balloons or airships with hydrogen

. ' Later, with a twinkle in his eye, Moore accused me of adding some air to the red balloon to create an explosive mixture-something I never admitted ." The helium industry owes its origination to this outrageous fraud, which was otherwise never publicized- or challenged. Incredibly, no one asked any questions. The R

.38/ZR-2 ' s and Roma ' s hydrogen had not exploded and helium would not have prevented the accidents. Besides, these were not the sitting-duck, tethered balloons the helium had been sought for in the first place. The stunt was · brilliant: had Moore arranged a clear 0 2-H2 flame , it would radiate only about 17% to 25% of its flame energy, and about half that fractional remainder would have been absorbed by atmospheric moisture in a few feet ' s distance. With an oxy-hydrogen explosion, the astonished

2 American Institute ofAeronautics and AstronauticsCongressmen "purchased" what Moore was " selling. " Let's take a moment to remember why this stunt, as Seibel admitted, was such a bald-faced lie. It ' s as easy as 1-2-3.

Fig 1. One-02 ; Two: Ignition temperature; Three: Fuel. Without all three legs of the triangle, there can be no fire. Furthermore, without all three legs and effective containment, there can be no explosion. There are not now, nor have there ever been, exceptions to these rules. Unlike in Moore's deceitful balloon stunt, there is neither oxygen nor ignition inside an airship envelope. As AIAA LTA TC ' s own Dr. Pant' s video demonstration showed, a buoyant hydrogen-filled envelope, when holed by a hot poker, can not explode. Its pressure forces the hydrogen out the opening until the balloon collapses. The funding cut came without such supporting tests , or even a second opinion. Wartime observation balloons (for which the helium had been originally sought) had not blown up when shot full of Brock, Sparkelt and Pomeroy " balloon buster" fighter plane ' s ammunition for a simple reason: if so contaminated with enough air as to be explosive, they could not fly

. So as we see, the off-target excuse for cutting powered hydrogen-borne flight funding was a lie, which nonetheless became military procedure enforced by the budget, which then gave birth to today ' s civil regulations. In spite of 90 years ' inertia of " that' s the way we ' ve always done it," there is no sense in forbidding efficient, affordable hydrogen-borne flight based on fear of impossible explosions

. As if acknowledging the fraud, TAR 893 states: " The lifting gas must be non-flammable, non-toxic and non-irritant. " So , instead of explosion, and discounting ammonia' s toxicity, seemingly the main objection, by FAA regulation, is the possibility of fire. Sound motion pictures cameras had not been invented in time for Moore ' s infamous Congressional hoodwinking, and in fact there is but one photo of a grounded WWI Army balloon rupturing during deflation labeled as " explosion," noted without injury. So how does one promote hydrogen as deadly, if not from explosion, then uncontrollable fire? Once again, an accident came along to help the anti-airship lobby. We have dozens ofphotos and 34 continuous silent motion-picture seconds of , mainly, nitrate-doped fabric burning . Since it's impractical to photograph actual oxy-hydrogen fire , and in spite of the complete lack ofpresented evidence the lifting gas played any ma jor role in the accident, Hindenbur g illustrations became ubiquitous with anything about hydrogen in our international culture. Open an encyclopedia to the hydrogen listing, and you will see tho se photographs ofbuming fabric , black smoke, and brilliant light.
3 American Institute of Aeronautics and AstronauticsFig.2. If leaking out or burning, hydrogen could provide no lift to the 242-ton airship still level after about ten seconds of fabric fire. Two generations ago advocates of conversion to safer, cleaner black oil pointed out how a stray cinder from the coal-fired stack would easily ignite the fabric on shipboard airplanes. Those who would as a result retire airships lacking affordable, available helium have yet to agree on a uniform theory ofwhere hydrogen fits into the Hindenburg accident development train

. The research and testing of Dr. Addison Bain, duplicated with other LZ-129 fabric samples in three other labs in two countries, revealed H2 need not have been present when the fabric ignited. By contrast, to insert hydrogen in between the igniter and the fabric:
1. Hydrogen at about .03613 psi must first escape from a container designed to hold it, while confounding layered safeguards designed to reveal a leak from any cause. 2. Hydrogen must then be retained by the outer cover incapable of containing it or handling lift loads , while avoiding diffusing into air in the space designed not to allow pressure buildup during rapid altitude-changing maneuvers. 3

. Nature's most quickly-dispersing gas must then linger in combustible concentrations in the air, while not floating into higher sections known to be uninvolved.

· 4. At that moment an ignition source of at least 457 degrees centigrade must appear in the

bubble ' s vicinity by getting past the outer covering that ignites at 195 °C. 5

. Burning six times faster than gasoline, weak-radiating oxy-hydrogen rising upwards must somehow create a mechanism t6 enable hydrogen below to further escape, and add the right mix ofoxygen to properly sustain combustion with enough BTUs to fry the covering in all directions, burning downwards towards other airship components. That list of highly improbable events had to take place in exact order and with very precise timing, depending in tum upon an equally improbable combination of circumstances (first

" flying moor" in such charged conditions , rain as hydroscopic nose ropes dropped, etc.) , makes a powerful argument (heretofore missed) that the Hindenburg was actually a pretty safe airship! No surprise Captain Hans von Schiller insisted on taking GrafZ e ppelin on its next scheduled run to South America on May 11

# t\ 193 7

- only to be shouted down. Likewise men bearing bum scars from LZ-129 eagerly climbed aboard LZ-130 for its spy missions in 1939. Others would argue it' s insane to hold an entire technology hostage for three-quarters of a century on account of the single fatal accident (13 passengers jumped out before landing) in a 14+year, 2,250+ flight, multi-million-passenger mile service history of LZs 7-17 , 120-130. More useful lessons should be learned from the GrafZeppelin(s): both LZ-127's incredible decade of performance and safety using weight-neutral fuel , and LZ-130 ' s rework so it only lost 55 ,000 pounds of lift trying to convert to helium

- only to fly with hydrogen some 30 missions.

4 American Institute ofAeronautics and AstronauticsIf one ' s mindset must have H 2 in between the outer fabric and the igniter as the last word on LZ129 or future separate

-cell and outer cover rigids, the lesson should be obvious : don ' t use materials nature



### - let alone a burst of my -h ydrogen - can ignite

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Fig. 3. Ralph Upson left Goodyear in 1921 in pursuit of a modern H2 design for efficiency, with the side benefit metalclads could not suffer fabric fire . The single, impractically small demonstrator ZMC -2 tried to point · out that nature continued to ignite flammable envelopes filled with air or "smothering" helium. Right: One 'SK' bag like this was actually ignited with tracer bullets, dispelling the myth of 

### He invulnerability dating to 1922.
Lest there be a crack in the dam, the airships

-are-doomed crowd roll out popular misquotes exacerbating fear of the fuel/oxygen ratios and minimum ignition energy, conjuring up a vision of gas that is surely too dangerous for airship use. Fact is , in the open air, ignition energy at the lower flammability limit is about the same for methane, gasoline, and hydrogen

. Problematic, if it was not so difficult to form and maintain a combustible mixture of H2+02 in open air. By contrast, petroleum vapors accumulating in low places persisting in combustible concentrations for extended periods have 22 (twenty-two) times the explosive power of oxy-hydrogen

. H2 dissolves , disperses [3

.8 times faster than methane] , and rises away from possible ignition sources [2

.75 meters per second]. Nevil Shute wrote of British ships whose valves opened directly under the cover : "

. ..there was no great danger of fire in the air, for any gas escaping would go upwards and out ofthe top ofthe ship , remote from any likely source ofignition." Furthermore, helium ' s single advantage, that of not combining with oxygen, did not stop airship fires , as Sir Barnes Wallis ' associate P.L. Teed predicted when he wrote in 1925 , "

. .. it is considered that the danger of fire on a helium-filled petrol-propelled airship is actually greater than on a hydrogen-filled and hydrogen

-kerosene propelled vessel.. ." Because helium required larger displacement for the same payload, it demanded more fuel; larger, more numerous tanks meant more explosive ullage. 

### Iri the only such comparison possible, materials and techniques of 1914

- 1918 were obviously les s advanced than 1942-1955 , so the advantage should be with the newer, less numerous , less fired upon, fewer ground cycle, helium ships

. Yet in production airships even operated for several years in wartime conditions , we see : Hydrogen

- fill ed SS ships 158 built 8 lost with fire involvement 7 men killed

.5 Helium

- filled K ships 134 built

12 with fire involvement 25 men killed

American Institute of Aeronautics and AstronauticsSadly, the fraudulent promise of explosion

- or, that is , fire safety- was only one of the deadly lies made to doubting airshipmen in 1923 as their non-flying Bureau of Mines masters promised

" 92 percent of H2 ' s lift. " At first arguing "reusable" helium would be cheaper and in spite of the Navy and War Departments being appropriated new sums annually (then transferred to the BoM to defray costs of helium extraction, compression and transport) , military LTA operations were drastically curtailed. The flightless bureaucrats were never held responsible as most every airship then in the nation's inventory had to be thrown away, and higher-elevation stations closed. BLM's funding was assured, but the actual expense of the helium dictation is impossible to calculate since it gave HTA, with no such expensive and performance-sucking restraint, just the leg-up it needed to bury LTA in the struggle for peacetime funding and development. Worse, helium supply never met demand as the Navy's two rigids had to share one fill of the gas. Realworld leakage exceeding the meager allotments demanded safety-valve capping on the ZR-1 by 1925. Tossed aloft by storms but unable to vent normal expansion, it's likely a cell burst; the unsupported, strained structure broke; and fourteen men were lost with their ship

. As the Navy released a statement about " large, unbalanced forces ," Zeppelin Captain-instructor Anton Heinen refused to parrot the party line, publicly stating, " Those valves were put there for a purpose! " Increased operational costs lead to less training and all-weather experience. Yet surviving USS 

### Los Angeles was often unable to replenish her leaky cells even when funds were available. Servicing only a handful of airships , Petrolia yielded some 46 Mft3 before being depleted in about eight years. Though England had refused helium for its airships and neither Italy, France nor Germany had then asked for it, by 1928 helium was entrenched in American airship culture, so funding for a replacement plant easily passed Congress. Constructed near Amarillo , the new plant started extracting helium from the Cliffside natural gas field in 1929. Larger ships were (and are) more expensive, and a single day in 1931 saw two helium-filled rigids fly together; it never happened again

. No one asked the BoM why helium could not be vented to save the lives oftwo linemen yanked aloft in 1932. When ZRS-4 was lost (along with seventy-three more men) while operating at helium-recommended altitudes in a wild storm, Heinen' s public complaints about the helium policy were again shouted down. Two smaller plants extracting from fields in Thatcher, Colorado and Dexter, Kansas were purchased and later closed by the Government under the 1937 Helium Act. The 50 ,000 acre Hugoton field became the primary global source with its concentrations of helium ranging from 0.3 percent to 1

.9 percent. The plant could extract some 24 Mft3 annually, but in spite ofwartime funding and priority, some K-type blimps actually awaited helium for erection on the west coast in 1943

. Boldly deployed overseas, helium shipments to the few dozen blimps was a challenge not fully met, a lesson for those assuming the US LTA can thrive as a helium importer. Since then, numerous accidents and incidents have their origins in forced acceptance of lesser purity, inability to reach favorable altitudes, and the operationally /economically prohibitive inability to dump lift. The US Navy's record of achievement coupled with its low death rate is testimonial to extraordinary airshipmen. Postwar, non-LTA uses of helium developed slowly owing to its price, set by the Interior Department. Ironically the Navy, just then adopting liquid helium transport, ceased regular airship operations as increasing non-LTA demand for helium strongly suggested it should no longer be discarded during peak natural gas pricing. With the Helium Act of 1960, the government incurred debt to build a pipeline in Texas , Oklahoma and

6 American Institute ofAeronautics and AstronauticsKansas to collect Hugoton Field crude helium. It was pumped into a natural geological formation named the Bush Dome. The BLM manages this natural Cliffside reserve, the only significant storage facility for crude helium in the world. Industrial gas companies , initially offered incentives, attached and purchased crude helium from the Cliffside reserve via stipulated annual allocations. Their sales gradually increased through following decades owing in part to helium 's price not being connected to any fundamental market-based activity. Rather, it was ball-parked annually by the total cost of the government helium program, plus accrued interest, divided by the estimated recoverable helium in the reserve. This continued until the cost of the program became a political liability. The Helium Privatization Act of 1996 mandated BLM sell its reserves by December 31 , 2014 to cover the debt.

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Fig. 4. 90% of US consumers are non-LTA, outspending airship financiers in the race to the bottom of the world's most practical helium supply. Most exists within a 250 mile radius of Amarillo, Texas, mapped here and as seen from space. Each K-bottle holds a paltry 283 cu ft, but all containment schemes are Murphy's playground. Quoting one industry report, "All

... helium assets (i.e., large cryogenic facilities) are on the Hugoton field

... and there they will sit until there is no more gas to run through them. There has been no push by any industrial gas company to locate and secure new sources." Hugoton reached highest production in the late 1970s, but the point of "peak helium ," where demand exceeded production causing reserve drawdown, was decades later. Users were first troubled by noticeable shortages in 2006. As energy costs rose, the price charged by helium suppliers reflected distance traveled from the liquefier. Though natural gas is the darling of energy-independence and environmentalism, as its price dropped below production cost, it has attracted little new drilling investment. The gas (and its helium by-product) tended to stay in the ground even with richest helium concentrations in seemingly inexhaustible pockets. (Nor would helium consumers want natural gas demand to dramatically spike, since it might mean venting the time-consuming helium.) Meanwhile the National Research Council highlighted the need to establish a market-based price to avoid depletion of the Federal Helium Reserve, transfer of taxpayer assets to private companies, subsidization of exports, and retarding efforts to develop lesser quality sources of helium. Nothing was done, and helium suppliers began refusing new customers. By October 2012 , in a highly visible example, the America's Challenge balloon race · was all hydrogen-filled for the first time. When the Bush Dome goes off-line next year (or later, when empty), price and availability will be in lock-step with natural gas consumption, totally regardless of helium demand. The situation seems bleak to those whose future is dependent on widespread freezing winters or clean-air legislation that spike natural gas demand to bring its price up. Meanwhile today 's helium price is downplayed as a small fraction of an airship's build
7 American Institute of Aeronautics and Astronauticscost, but promises ofnew fabrics and bonding technology' s permeability rates will be challenged by modem designs ' demand for higher envelope pressures - and Murphy

. When a rare commodity' s demand exceeds capacity, governments institute rationing and price controls. Only favored users are given supply, at a price set by a bureaucrat. High-tech consumers like India and China will fatten overseas suppliers in stable countries , as weaker helium sources come on lineas prices support their plant investment in blessed natural gas pockets ofunknown longevity

. Overcoming the huge mental block created by the astonishing burning fabric images and flaming rhetoric , however challenging, is airship ' s only hope of a profitable future. That' s because the most compelling reason for discarding helium is not explosion, or even fire

- but performance

. Two US Navy officers who ' d refused to swallow the helium propaganda, even at WWII's height, self-published the harsh facts. "Helium, at standard conditions (32 F., 29

.92" Hg, 100% purity) has 93 per cent the lift of hydrogen. In practical operation, because helium is never available at purity greater than 97 per cent, and because of operational considerations which result in a further lowering of purity of helium relative to that of hydrogen, the lift difference is rarely less than 1 0%

. As the temperature of the air mass in which the airship operates increases , a further disparity is introduced which increases the lift advantage ofhydro gen. .. The structural weight of the ship is constant, service load including fuel is constant (for the same range) and the entire loss oflift must come out ofthe only remaining variable

- the pay or military load

. Let us assume an airship of 10 mft3 capacity of 50 percent dead weight and 30 percent service load : Standard gros s lift Dead weight Useful load Service load (fuel , etc
.) Military load Hydrogen Helium 375

.0 tons 337.5 tons 187

.5 tons 187

.5 tons 112

.5 tons

75.0 tons 187

.5 tons 150

.0 tons 112

.5 tons

37

.5 tons The entire loss of lift reduces the military load by 50 percent, not 7 per cent, as we have been lead to believe . . . It is quite conceivable that the additional [payload] could easily mean the difference between accomplishment and failure of a mission, or even the difference between saving and losing the airship itself. " Many (ifnot most) airship loses did not involve fire. The seemingly small but overwhelmingly significant difference between the gross lift per unit volume of helium vs . hydrogen was first explained by BuAer' s C

.P. Burgess

. " There is much misunderstanding and confusion regarding the loss in performance of airships resulting from decrease in the lift of the gas , especially from the use of helium instead of hydrogen. It is common practice in America to take the unit lifts ofhydrogen and helium as .068 and .060 lb ./ft3 in the standard atmosphere at sea level..

. From these figures , 11.8 % ofthe gross lift is lost by the use of helium instead of hydrogen; but the percentage los ses of useful and military or commercial load are much greater because the weight of the ship empty is a fixed quantity, and the ab solute lo sses of gross and useful lifts are therefore equal. " Burgess cited an example to find the percentage losses of useful and commercial loads due to the substitution of helium having 88

.2% as much lift as hydrogen :
"Loss ofuseful load is (1-

---. 882)/.38 = 31.0% Loss ofcommercial load is (1--- -. 882)/.20 = 59

.0%"

8 American Institute of Aeronautic s and AstronauticsBurgess explained those figures did not reflect the further crippling necessity of helium ships having to start out 30% empty (or full ballonets) to avoid venting the irreplaceable gas during climb out. At equal payload, the necessarily larger helium ship will have heavier propulsion and greater fuel consumption for the same speed

. Also not counted is dead weight of any onboard water recovery plant, since the ship loses at least six pounds for every petroleum gallon burned. Larger airships require matching increases in support facilities and personnel, etc
. Profitability after reaching a given ratio was first noted in a J

.K. Bock paper: " One characteristic parameter is the ratio of empty weight to the maximum lifting power which should be in the order of 50% as an engineering guideline. Aircraft (such as the Airbus family) reflect the engineering endeavors about the 50% ratio to be a realistic value for airborne carriers , partially only achieved by the use of carbon fiber materials , resulting in a ratio of 48 to 49 percent in the case of the A-380. Interesting are the data for the Hindenburg (LZ-129) with 54% , which proves that Zeppelins of that size were already at the brink ofbecoming economical carriers. " Small wonder the Germans always said the LZ-129 was the first Zeppelin to earn his keep (though they' d planned the longer LZ-131 ). A contemporary observer pointed out, "Eating up less than $300 worth of crude oil , they propel across the Atlantic fifty passengers at $400 each and 26 ,000 pounds of freight at $1 a pound

. A very tidy sum . . . for an average oflittle more than two day ' s work! "
Even at LZ-129 lift-size and propulsion-cost efficiency, payload weight

-profitability is still limited by BTUs per fuel pound carried. When used as fuel, hydrogen would greatly enhance propulsion-weight performance, since it packs in 3 (three) times the energy of gasoline per pound

. In previous papers authors presented a plan to build an airship with complete control of its static condition, without on board compressors, based on LH2 ' s 851-to-1 expansion ratio and paltry BTU value per cubic foot. One pound of hydrogen fuel can expand to 192 scf (each kg is equivalent to 11.98 m 3 and contains 39.4 kWh) , meaning its weight disappears while offering an option of 12 more pounds ofquickly-consumable lift. Helium ' s first task is to lift it self, since it' s double hydrogen ' s mass (weight @ STP : 100 ft3 = .54 lb., vs . 1.06lb. for He ). We go to great expense and operational hassle to keep helium pure to save payload (the only thing that can be changed). We ' d of course do the same for hydrogen, making internal combustion impossible

. Inside the bag, the actual flammability limit for air-in-gas is 24

. 1 % , hardly a worry when no airship ever flew with even 12% contamination

. While only the oxygen contaminant need be cleansed for fire safety, a modem airship need not carry 0 2 absorbers or purifiers when using hydrogen as fuel, since contaminants are drawn into the combustion chambers. Further 0 2 isolation could be achieved by inflating ballonets with exhaust gases , or eliminating the ballonet. Nor can an H2 fueled ship fall into a pool ofits own dumped fuel. Once unchained from both helium pipeline and petroleum tanker truck, airships would be privy to the vast experience and knowledge base of the hydrogen industry, which produces millions of pounds and consumes it for everything from self-cooling megawatt 1, 800- and 3,600

- rpm generators to reducing windage in large frequency-changer sets to hydrogen:.bath " atomic " welding. Hydrogen ' s combustion energy per unit mass offers the highest specific impulse engines. 40-year old fuel cell tech was so reliable the Space Shuttle never carried batteries. Though a fuel in Hazard Category #2 like natural gas , safety rules and regulations are long established, insurance is available, manufacturing and handling technologies firmly in place. Darling of the anti-OPEC and clean air crowd, adoption of hydrogen fuel is in the running for

9 American Institute of Aeronautics and AstronauticsAIAA members ' proposed Z-prize, the first carbon-free airship flight. A beacon for environmentalists, it would seem to have the practical application of, say, the human-powered helicopter. To the contrary, helium's noble if fallacious goal of reducing airship fires could actually be achieved by building a carbonless, oxygen-free airship. Unlike petroleum, hydrogen is non-corrosive and non-toxic. Self-inerting, its ullage-free tankage is impossible to ignite. Without petrol, modem fire-resistant and retardant materials make this goal achievable.

Fig.S. Not unlike WWI airship "bases" hewn from forests and equipped with H 2 gen-sets, CDR Lou Prost (USN, Ret.) directed the conversion of the ex-L-19 to hydrogen for its successful decade flying Europe. Sold to Japan and converted back to helium, it was lost. Efficient and safe, or not, change is coming. Deep-pocketed consumers supporting the Helium Stewardship Act of 2012 (S.2374) warned, "In practical terms , this will happen sometime in 2013 when operating funds are projected to cease if action is not taken to reauthorize the Reserve." Price/availability after 2014 is obviously a worry for airship investors eyeing helium's lockstep with natural gas production. Even if abundant, helium costs much more than hydrogen, and the gap will widen as once-rich fields are exhausted and poorer concentrations are added to the helium pipeline, each increment ofproduction smaller than the last, and greater cost per unit of capacity. More cost-effective hydrogen production techniques continue to be developed, and in contrast to rising energy/transport costs, H2 's delivery price and availability will be limited only to areas possessing both sunlight and water. Near perfect purity is achieved with palladium filters, not requiring the activated charcoal at LN2-temps used in making ultra-pure helium. All of LTA tout hopes that modem weather-avoidance technologies will overcome the largest cause of past airship accidents, the majority of which were at least partially weather-related and often did not include fire. The increased operational options offered by higher-performance airships should be the safety-history lesson learned. These authors hope performance /profit projections for craft saddled with helium having to lift petroleum propulsion are conservative

. However, while Rear Admiral William Moffett publicly denounced the idea of US Navy rigids using even a small percentage of hydrogen for lift, the airship tender USS Patoka was quietly equipped with a hydrogen generator, lest something as simple as a stuck valve threatened the loss ofthe ship. Likewise, today ' s airshipmen need a backup plan. The helium industry owes its entire existence to the airship, but it will survive not having a market for its " balloon gas"

- purity product. Meanwhile, in our energy-dependent civilization, the hydrogen-fueled economy is inevitable. Airships are not. LTA can compete in the race to the bottom ofthe wells , or re-enter safe, profitable operations without further delay.
10 American Institute of Aeronautics and Astronautics