Rocket Fuel, Thermite, and Hydrogen: Myths about the Hindenburg Crash

There are many myths about the Hindenburg disaster, usually spread by “hydrogen advocates” who want to persuade people that hydrogen played no role in the tragedy.

This page explores and debunks some of the more common Hindenburg myths in detail, including:

• “The Hindenburg was painted with rocket fuel“
• “The Hindenburg was painted with thermite“
• “The Hindenburg’s outer cover was highly flammable“
• “Hydrogen burns without color, so it could not have been hydrogen burning“
• “People on the Hindenburg were not injured by the hydrogen“

• Commentary: The irony of the hydrogen advocates

Or for a shorter summary of this subject, visit: Photographic Evidence that the Hindenburg was not “Painted with Rocket Fuel”

Hindenburg Myth 1: “The Hindenburg was painted with rocket fuel”

This idea originated with Addison Bain, and comes from the fact that Hindenburg’s fabric covering was doped with a solution that included aluminum powder, and in certain sections iron oxide, which are sometimes used as components in solid rocket fuel.

Hindenburg’s cotton-canvas covering was doped to seal and protect it from water, wind, and damage from small objects, and to keep it taut for aerodynamic reasons as the ship moved through the sky.  The dope was a solution of cellulose acetate butyrate to which aluminum powder had been added.  At the top of the hull, a layer of iron oxide was applied to the inside face of the covering to protect the fabric from the UV radiation in direct sunlight.

The aluminum powder gave the ship its silvery coloring, but its practical purpose was to reduce the heating effects of the sun, which can cause an airship’s gas cells to expand and release their gas.

But while aluminum powder may be used in certain rocket fuels, that doesn’t mean that everything containing aluminum powder is a rocket fuel. (As an analogy, butyl rubber — polyisobutylene — is a component in both C-4 plastic explosives and basketballs, but that doesn’t make your basketball a bomb.)

Aluminum powder has many uses other than rocket fuel, including the manufacture of photovoltaic solar energy panels and metallic paints for cars, boats, furniture, and other items.

The chief ingredient in rocket fuel is an oxidizer; a substance which creates its own oxygen supply to support combustion. Without an oxidizer, you don’t have rocket fuel.

As explained by the website of NASA’s Kennedy Space Center:

A solid propellant always contains its own oxygen supply. The oxidizer in the Shuttle solids is ammonium perchlorate, which forms 69.93 percent of the mixture. The fuel is a form of powdered aluminum (16 percent), with an iron oxidizer powder (0.07) as a catalyst. The binder that holds the mixture together is polybutadiene acrylic acid acrylonitrile (12.04 percent). In addition, the mixture contains an epoxy-curing agent (1.96 percent). The binder and epoxy also burn as fuel, adding thrust.

Not only does rocket fuel require an oxidizer, but the oxidizer is by far the largest component of rocket fuel (approximately 70% in the case of the Space Shuttle).

The only substance in Hindenburg’s doping compound which could conceivably act as an oxidizer was the iron oxide added to one section of the covering, but it was in too small a quantity, and was too separated from the aluminum powder (at no point in the doping process were the aluminum powder and iron oxide mixed together), to act as an oxidizer in this application.

[For additional technical details regarding the Hindenburg's covering and "rocket fuel," see: The Hindenburg Hydrogen Fire: Fatal Flaws in the Addison Bain Incendiary-Paint Theory, A. J. Dessler "Dressler" - download pdf]

Without an oxidizer, even the Space Shuttle would still be fizzling slowly at its launch pad in Florida… just like this theory.

Perhaps the best evidence that the Hindenburg was not painted with “rocket fuel” are the photographs and films of the disaster. If the Hindenburg had been painted with anything even remotely as flammable as rocket fuel, its covering would have been quickly and totally devoured by the fire, but that did not happen, as you can see from the photos presented on this page.

Hindenburg Myth 2: “The Hindenburg was painted with thermite”

Basically a variation on the rocket fuel myth, many people seem to think that the Hindenburg was painted with “thermite.”

Scary word, thermite. Makes for a great sound bite And since thermite can be made from aluminum powder and iron oxide — which were used on certain sections of the Hindenburg’s covering — it is easy to see why this myth spread so rapidly.

Unfortunately, the truth is a little more boring. While it is true that a thermite reaction can be created with a mixture of aluminum and iron oxide, it requires a ratio of about 1 part aluminum to 3 parts iron oxide [download pdf]. The dope used on Hindenburg’s silver-colored hull contained 5 parts aluminum to 1 part iron oxide; basically the reverse of the ratio needed for thermite. In other words, Hindenburg’s dope contained less than 1/10 the amount of iron oxide needed to create a thermite reaction.

In fact, since actual thermite requires 3 parts of heavy iron oxide for every 1 part of light aluminum powder, if the Hindenburg had been painted with thermite it might never left the ground in the first place; the designers of a lighter-than-air dirigible would never paint the ship with thermite, not only because of its flammability, but also because of its extremely heavy weight.

Finally, a thermite reaction requires the components to be well blended, and if they separate, the mixture is useless. The aluminum powder and iron oxide on Hindenburg were applied separately, in different layers, and were not mixed together as in thermite. (Addison Bain refers to “thermite hot spots” — small points where he found the iron oxide in the first layer of dope to have bled through to the subsequent layers of aluminum powder — but he does not offer evidence of how widespread this might have been, or any evidence that a significant overall thermite reaction occurred during the burning of the Hindenburg.)

The best evidence that no significant thermite reaction took place are the photographs and films of the fire. As mentioned above, iron oxide was applied only to the upper portion of the Hindenburg, to protect the covering from the UV radiation in sunlight. (The lower part of Hindenburg’s hull was doped only with aluminum, since there was no point in adding the additional weight of a layer of iron oxide to a part of the ship not exposed to the sun.) Photographs and film of the Hindenburg fire show no difference in the speed at which the covering of the upper hull burned as compared to the lower hull. If the upper hull had really been painted with thermite, it would have burned at a much faster rate than the lower hull.

In fact, the only lines of demarcation seen in the photographs of the fire are between gas cells, because it was primarily the hydrogen — and not the covering — which was burning.

Hindenburg Myth 3: “The Hindenburg’s outer cover was highly flammable”

This is the generalized version of the rocket fuel and thermite myths. Certain hydrogen advocates have tried to argue that the covering was so highly flammable that it was the covering — and not the hydrogen — which was the primary factor in Hindenburg’s rapid destruction.

In fact, the Hindenburg’s covering, while certainly combustible, was not especially flammable, and the covering material itself actually burned quite slowly. Even after the crash, large areas of the covering remained unburned, indicating that the covering could not have been highly flammable, and many sections burned only when exposed to the direct heat of the burning hydrogen, as seen in the films and photographs of the disaster.

As discussed above, Hindenburg’s covering was made of cotton canvas doped with a solution of cellulose acetate butyrate, to which aluminum powder (and in some places iron oxide) had been added.

Canvas doped with cellulose acetate butyrate is combustible but nonflammable; in other words, it will burn if held in a flame, but tends to self-extinguish when removed from heat. [See, The Hindenburg Fire: Hydrogen or Incendiary Paint?, A. J. Dessler, D. E. Overs, and W. H. Appleby, "Dessler/Overs/Appleby," pdf available here.)]

(Some discussions of the Hindenburg incorrectly claim that the dope contained cellulose nitrate, rather than cellulose acetate. In fact, the designers of Hindenburg deliberately avoided cellulose nitrate precisely because it was known to be flammable, and they chose the safer cellulose acetate instead. The dangers of cellulose nitrate were well understood at the time, since it was used in the first photographic films which were known to be highly flammable. Cellulose acetate filmstock was introduced as an alternative in the 1920s, and was known as “safety film.”)

The addition of aluminum powder may have made the doping solution somewhat more combustible, but it was still a far cry from rocket fuel.

In discussing the flammability of the covering, however, it is important to differentiate between two questions:

• (A) Whether the covering was sufficiently flammable to have been the initial source of the Hindenburg fire (i.e., whether the covering itself could have been ignited by an electrical discharge, and then ignited the hydrogen, as suggested by Addison Bain)

or

• (B) Whether the covering was so highly flammable that it was the main cause of the destruction of the ship, rendering the presence of hydrogen an insignificant factor in the crash (as suggested by some hydrogen advocates who go far beyond the claims made by Addison Bain, and who argue that Hindenburg’s covering was so highly flammable that the ship would have been destroyed by fire even if it had been inflated with helium, a position repudiated by Bain himself.)

While there is evidence that Hindenburg’s covering might have been sufficiently flammable to be a source of the initial ignition (as suggested by Addison Bain), there is overwhelming evidence that the covering was not so highly flammable that it was a major factor in the subsequent destruction of the airship (as suggested by those who have taken Dr. Bain’s theories well beyond the limits of his own suggestions).

Various scientific tests performed on doped canvas replicating the covering of the Hindenburg show that the covering itself actually burned quite slowly. In fact, without the presence of hydrogen, the covering would have taken almost 40 hours to burn completely: The upper covering, containing iron oxide plus aluminum, would have taken about 30.9 hours, and the lower covering, containing aluminum alone, would have taken 37.9 hours. (See, Dessler/Overs/Appleby, cited above.)

In fact, Addison Bain’s own experiment with a 2-1/2″ piece of the actual covering of the Hindenburg, shown on the British television program Secrets of the Dead, What Happened to the Hindenburg, shows that it would have taken approximately 40 hours for the Hindenburg’s covering to burn. (Cited in Dessler/Overs/Appleby.)

Even the television show Mythbusters declared this myth as busted.

And you can see for yourself that the Hindenburg’s covering was anything but highly flammable. Photographs of the wreckage show that even after a fire so intense that it destroyed an 800-foot airship in about 34 seconds, sections of the covering still remained unburned.

Hindenburg Myth 4: “Hydrogen burns without color, so it could not have been hydrogen burning”

This myth contends that since hydrogen burns with a mostly invisible flame, and since the Hindenburg’s flames were orange, it could not have been the hydrogen that was burning.

Many versions of this theory are supported by a color photograph of the Hindenburg burning with a bright orange flame.

Or, more accurately, a colorized photograph of the Hindenburg burning, since no color photographs or films were taken of the Hindenburg disaster. Any color photo or video on the internet showing the Hindenburg on fire is a black & white original which has been colorized, and whoever added the color could have just as easily made the flames pink, purple, or green.

(Color Kodachrome photographs were taken after the crash, but they show the wreckage on the ground, after all the hydrogen had burned off.)

But hydrogen does, in fact, burn with a mostly invisible flame, and even the original black & white photographs show flames which are clearly visible.

So here’s the simple explanation: Hydrogen does burn mostly without color… but only when hydrogen is the only thing burning.

As the Hindenburg was consumed by flame, it was not only the hydrogen which burned; it was also the canvas covering, the duralumin (an aluminum alloy) framework, the steel bracing cables, the gelatine-cotton gas cells, the tanks of diesel fuel, and even the tables and chairs. And no-one has ever claimed that diesel fuel, canvas, aluminum, or steel burns with an invisible flame.

In addition, not only did the rest of the Hindenburg’s components emit color and light themselves as they burned, but they also acted as a mantle. A “mantle” is the part of a gas lamp that glows to emit light. Most flammable gases burn without color, which is why gas lanterns always use a mantle; the gas burns and creates heat, but it is the mantle which glows and emits light. The duralumin girders and steel bracing wires of the Hindenburg were perhaps the largest mantle in gas lamp history.

During World War I, many of the hydrogen zeppelins sent by the German Army and Navy to bomb England, France, and Belgium were shot down and burned, and all burned with bright orange, yellow, and red flames — just like the Hindenburg.

Hindenburg Myth 5: “People on the Hindenburg were not injured by the hydrogen”

This is probably the most absurd myth about the Hindenburg disaster, and one that is frequently promoted by advocates of hydrogen as an alternative to fossil fuels. (And because of its extreme absurdity, this may be the claim which most undermines the credibility of these hydrogen advocates).

Whatever caused the initial ignition of the Hindenburg fire (whether it was the covering ignited by an electrical discharge, or leaking hydrogen which caught fire, or even sabotage, which is unlikely) the airship was incinerated in less than a minute — and came crashing to the ground as smoldering wreckage — because virtually the entire space of the ship’s 800-foot hull was filled with hydrogen which erupted in flame. Yet many hydrogen fuel advocates contend that the millions of cubic feet of hydrogen in Hindenburg’s gas cells (representing, according to Addison Bain’s own estimate, over a billion BTUs of energy) somehow had no effect on the passengers and crew when it burned.

The newsletter of the American Hydrogen Association informed its readers: “No deaths were due to the hydrogen fire that was ultimately ignited by the burning skin of the Hindenburg.” [Hydrogen Today, vol. 10, no. 2, 1999, p.8 - download pdf]

According to the Association’s website:

Hydrogen is about fifteen-times lighter than air. After ignition by the violently burning surface varnish, flames from hydrogen combustion traveled upward, far away from the crew and passengers in the cabins below. What fell to the ground with the passengers were burning shrouds from the exterior fabric, a large inventory of diesel fuel, and combustible materials that were in the cabins…

Sixty-two persons from the Hindenburg lived through the disaster by being fortunate enough to ride the Hindenburg down and escape the flames and wreckage that fell to the ground. Many of these survivors were relatively unharmed.

Dr. Karl Kruszelnicki, an Australian hydrogen advocate who is a popular television science expert known as “Dr. Karl,” has gone so far as to claim that the Hindenburg’s hydrogen was not only “totally innocent,” but did not even contribute to the ensuing fire:

In all of this, the hydrogen was innocent. In the terrible disaster, the Hindenburg burnt with a red flame. But hydrogen burns with an almost invisible bluish flame. In the Hindenburg disaster, as soon as the hydrogen bladders were opened by the flames, the hydrogen inside would have escaped up and away from the burning airship – and it would not have not contributed to the ensuing fire. The hydrogen was totally innocent.

[The photographs of the disaster make clear how just ridiculous Dr. Kruszelnicki's arguments are, and as a scientist he should also understand why the Hindenburg did not burn with an invisible flame; his complete article is rebutted here.]

Hydrogen advocate Greg Blencoe from the company Hydrogen Discoveries claims:

The clean hydrogen flames [emphasis added] swirled above the occupants of the passenger compartment, and all those who rode the airship down to the ground survived. Thirty-five of the thirty-seven casualties perished from jumping to the ground, and most other injuries resulted from diesel burns.

Silverwood Energy makes the same recycled claim, including the reference to “clean hydrogen flames.”

The American Hydrogen Association newsletter states “The sixty-two surviving persons that rode the gently falling Hindenburg (emphasis added) to the ground had only slight injuries” [Hydrogen Today, vol. 10, no. 2, 1999, p.9 - download pdf].

And another website similarly claims that “those who remained aboard the ship during its relatively gentle descent to the ground escaped with minor injuries.”

[The concept of a "gently falling Hindenburg" is certainly not borne out by films of the disaster, which show the airship crashing violently to the ground in less than half a minute.]

One hydrogen cell retailer offers a “Brief History of Hydrogen” in which they discuss the Hindenburg and state: “the hydrogen burned safely above the passengers and didn’t cause a single death.”

And there is even a hydrogen advocate who argues that “Hydrogen was used very successfully as a lifting gas until the Hindenburg disaster gave it an unwarranted bad reputation,” and claims “it is even possible that the hydrogen contained within the Hindenburg when the skin caught fire actually mitigated the disaster somewhat if anything.”

[The idea that the hydrogen "mitigated" rather than exacerbated the disaster is simply nonsensical; even if it were the covering which was the initial source of ignition, the subsequent fire would have progressed very differently if the airship has been inflated with helium rather than hydrogen.]

How does one even begin to address the claim that almost 7 million cubic feet of hydrogen can burn in about 34 seconds, and completely destroy an 800-foot airship, and yet not be responsible for injuring any of the passengers or crew?

• One could list the fatalities of the Hindenburg disaster and describe how each one died. Patrick Russell has a brilliant blog which describes the fate of each person on Hindenburg’s final flight. For example, Patrick’s research conclusively refutes the oft-cited claim that “35 of the 37 casualties perished from jumping to the ground.” (Although even if that claim were true, these victims would not have needed to jump from a burning airship in the first place if the Hindenburg had been inflated with helium rather than hydrogen.)

• One could review the scientific evidence (above) demonstrating that the covering alone would have taken up to 40 hours to burn, so if the Hindenburg had been inflated with helium the passengers and crew would have had ample time to exit to safety.

• One could refer to a diagram showing the locations of the crew (survivors in green, casualties in red). Crew members and passengers who were in a position to exit quickly generally lived, while those who were trapped in the ship perished.

• One could point to the unanimity of opinion among respected airship historians who agree that, whether or not Hindenburg’s covering was the source of initial ignition, it was the presence of hydrogen which was responsible for the severity of the crash.

• One could consider the lack of fire in the many incidents and accidents involving helium-inflated airships, such as the USS Shenandoah (which, in addition, was also doped with an aluminum powder solution).

• Or one could simply watch the film of the disaster once again and approach the matter with basic common sense.

But perhaps the larger point is the absurdity of this debate itself. In their determination to exonerate hydrogen at all costs, hydrogen advocates like Greg Blencoe and others have made the macabre, autopsy-like argument that it was not the hydrogen itself which killed the victims of the Hindenburg, but other things (diesel fuel, burning material from the cabins, jumping from a great height… anything but hydrogen). But even if those arguments were true — which they are simply not — do the hydrogen advocates really think it matters what particular substance (hydrogen, diesel fuel, or burning bed linens) caused particular injuries, since the Hindenburg itself would not have crashed to the ground in less than a minute if had not been inflated with hydrogen?

These arguments are like claiming that the San Francisco earthquake of 1906 did not cause many casualties, since most of the deaths were actually caused by the ensuing fire, and not by the earthquake itself.

The Irony of the Hydrogen Advocates

Many of the myths about the Hindenburg disaster — from the nonsense about rocket fuel to the absurd claim that nobody was injured by the hydrogen fire — have been circulated and promoted by hydrogen advocates who seem determined to prove that anything but hydrogen was responsible for the destruction of the Hindenburg and the deaths of its victims.

For example, the South Carolina Hydrogen and Fuel Cell Alliance (whose board of directors seems to include people with a scientific background) uses its Twitter account to send frequent and repetitive tweets claiming that “NASA” found that the Hindenburg’s covering was “sealed w/ solid rocket fuel.”

The National Hydrogen Association website publishes an FAQ and distributes a “Fact Sheet” [pdf] which make a similar claim.

And in their zeal to exonerate hydrogen, the hydrogen advocates are not restrained by the normal rules of logic. For example, to support its claim that no-one was harmed by the hydrogen fire on the Hindenburg, the American Hydrogen Association states that the hydrogen fire “was over in less than a minute.”

They explain:

“In less than one minute after the hydrogen bags were interrupted and the hydrogen started to escape, the hydrogen was gone. You can count the seconds in the news reel film of the disaster.” [Hydrogen Today, vol. 10, no. 2, 1999, pp. 8,9 - download pdf]

They are correct. The hydrogen was gone in less than a minute… because the entire airship was gone in less than a minute.

How do the hydrogen advocates expect to be taken seriously on other matters relating to science and technology, when they are willing to put their names, websites, and reputations behind unscientific urban myths and absurdly illogical arguments?

The great irony is that the nonsensical claims about the Hindenburg disaster offered by these hydrogen advocates, which so badly undermine their own seriousness and credibility, are completely unnecessary to their cause. The fact that hydrogen was responsible for the Hindenburg disaster is completely irrelevant to whether or not hydrogen makes a good alternative to fossil fuels. In fact, hydrogen could (theoretically) be both a wonderful alternative fuel and a terrible lifting gas for passenger airships; there is no necessary contradiction between the two. Many substances which are ideal for one application are hazardous in another, and hydrogen advocates like those mentioned above, who can’t seem to understand or express this simple concept, just raise questions about their own analytical abilities. Many people support solar energy, but they don’t feel the need to claim that sunlight never causes skin cancer.