Biological Balloon Bomb Was "High Priority" in U.S. Germ War Program
Leveraging knowledge of Japan's WW2 Fu-Go balloons, the US modified high-altitude surveillance balloons used to overfly the USSR to carry an anti-crop cluster bomb. The program "did not run smoothly."
Recently I wrote about revelations from two FBI documents that indicated that Japan’s WW2 “Fu-Go” balloon barrage over North America included some balloons that carried anthrax and, quite possibly, bubonic plague. This follow-up article examines a little-known project by U.S. biological warfare agencies to utilize free-floating, high-altitude surveillance balloons for use as biological weapons (BW) delivery systems.
The U.S. successor to the Fu-Go balloon attack was Weapons System (or WS) 124A, more colorfully known as Project Flying Cloud. WS-124A was a free-floating balloon meant to fly up to nearly 40,000 feet and, upon timed release, drop an 80 lb. bomb containing dry anti-crop pathogens over an enemy’s farmlands. The “enemy” in this case was the Soviet Union.
There isn’t a lot of material about WS-124A, and this article relies on what appears to be the primary documentation currently available. One unexpected aspect of the research into the biological balloon bomb for me was how much more massive was the U.S. balloon program in general. This article cannot substitute for a full history of the entire subject. For that, it’s worth following the links I’ve embedded throughout.
The article below will, among other things, show that, as a 2001 Army textbook put it, the military’s anti-plant balloon bomb was developed “[c]opying the method the Japanese developed during World War II” (page 51).
The Air Force balloon program centered around the creation of high-altitude surveillance balloons that could substitute for high-risk aircraft overflights of East Europe, China and the Soviet Union in the early years of the Cold War. The military’s balloon programs went by many names over the years: projects Skyhook, Helios, Mogul, Gopher (WS-119L), Grayback, Moby Dick Hi, Grandson, and Genetrix.
According to a February 2023 article in Vice, the military has not abandoned using balloons for various purposes, including surveillance. Vice’s article itself relied a good deal on an earlier July 2022 article at Politico, “U.S. military’s newest weapon against China and Russia: Hot air.”
Skyhook was the oldest program, initiated by the Office of Naval Research in 1947, using technological breakthroughs on balloon material design from University of Minnesota scientists Jean Piccard and John Ackerman. After World War II, Piccard joined up with Otto W. Winzen, chief engineer at Minnesota Tool and Manufacturing Co., and together they settled on use of polyethylene as the best plastic to make large balloons — the same kind of plastic used to bag carrots. (The Japanese had used paper balloons.) By happenstance, General Mills was nearby, and their balloon division became the military’s primary contractor for the project.
General Mills wasn’t the only contractor. Important advances on the “automatic altitude control system” came from a group of meteorologists and physicists experimenting on balloons at New York University. According to NASA historian Curtis Peebles’ 1991 book, The Moby Dick Project: Reconnaissance Balloons Over Russia (Smithsonian Institution Press), “The NYU group studied the ballast system used on the FUGO” (pg. 88).
Peebles wrote that the idea of using balloons for modern forms of surveillance “was first proposed in a 1946 study by the RAND corporation” (p. 100). He also noted that polyethylene was abandoned by 1951 as too brittle for use in low temperatures. “Bakelite’s DE-2500 was picked as the standard for balloons” (p. 102).
The Skyhook and Moby Dick balloon programs were unclassified, and were often used to mask classified programs, such as Flying Cloud. The unclassified programs could be used to work out technical issues, while also carrying out other missions, such as gathering data on cosmic rays, or working out the squirrelly weather and wind patterns of the upper atmosphere. The latter was necessary as military aircraft were engineered to fly ever higher.
There is also another aspect to the balloon program that I’m not going to discuss here, primarily because an adequate discussion would require a full article treatment. That other aspect concerns the overlap between balloon operations and the reports of UFOs in the later 1940s and 1950s. Author Nicholson Baker recently examined this issue. There’s a vast literature on this subject, and if the reader is looking for an airing of this controversy, he or she will have to look elsewhere. I will only note here that for years the primary debunkers of UFO sightings had some kind of military or government connection, but on the other hand, so did a number of the UFO proponents, like purported Roswell whistleblower, Colonel Philip Corso.
A Controversial Program
Air Force historian Dorothy Miller discussed the balloon bomb program in her top secret History of Air Force Participation in the Biological Warfare Program 1951-1954. She described the program as getting underway in 1950.
A separate Air Force report, which was issued in 2000 and catalogued the presence of biological or chemical weapons material existing at Air Force bases within the continental United States, mentioned the balloon bomb as well.
According to the latter report, the Flying Cloud program was managed by the Special Weapons Branch at Wright Air Development Center (WADC), Wright-Patterson Air Base in Ohio. The top secret project had been initiated by the U.S. Army’s Chemical Corps, the military’s primary biowar agency, but it utilized funds from the Air Force’s brand-new Air Research and Development Command (ARDC). The military’s official statement of the need for such a system was made on April 5, 1951, and approved on June 23, 1952.
Miller’s history of the program provides the most detailed overview, while a May 1953 “status report” by R.E. Stine for the Chemical Corps Biological Laboratories (PDF pgs. 33-69) offers a wealth of technical details. Stine’s report was approved by the director of the laboratories, John L. Schwab.
As an interesting aside, Schwab had been head of the joint CIA-U.S. Army Special Operations Division (SOD) at Camp Detrick. He was a close colleague for Detrick’s other SOD top scientist (and SOD Acting Chief), Frank Olson. Olson was murdered by the CIA in November 1953, likely because he was considered a security risk due to disgruntlement with CIA crimes.
Schwab had close and daily contact with CIA leadership and researchers involved in MKNAOMI, the covert program the CIA operated in collaboration with the U.S. Army. The Agency and the Army worked in tandem, as the 1970s U.S. Senate Church Committee put it, “developing, testing, and maintaining biological agents and delivery systems for use against humans as well as against animals and crops” (pg. 6).
In 1959, Schwab gave a sworn affidavit in the sedition trial of journalist John W. Powell, who had disclosed use of U.S. germ warfare in the Korean War. Schwab testified that the U.S. had a capability to wage germ warfare going back to January 1949.
Getting back to our main topic, the major secondary source on the balloon biological bomb material is aerospace historian Curtis Peebles’ book, mentioned above.
Miller said the biological balloon bomb program was considered “high priority.” The program “represented about one-sixth of all development effort that had been expended on biological warfare munitions” (Miller, pg. 112).
Besides the Chemical Corps and WADC, the program utilized a number of contractors including the Air Force’s Cambridge Research Center in Cambridge, Massachusetts, and both the General Mills Corporation and the Wenzen Research Company in St. Paul, Minn.
The development of the WS-124A balloon itself was mostly a joint enterprise between the military and its by now long-time contractor, General Mills. The project engineer for the program at General Mills was active Lutheran churchgoer Marvin A. Sandgren, who by September 1952 successfully had developed “a feasible working design on all components, except the heater and [biological] agent package” (Stine, PDF pg. 40).
Even so, according to Miller, the program “did not run smoothly” (p. 113). There were a number of problems with the development of the balloon and its bomb. The latter was known as the E77 biological bomb.
According to Stine’s “status report,” by the end of December 1952, “the task of evaluating General Mills’ work and developing an operational balloon-delivery system for the E77 and other munitions was established by the Air Force at its Cambridge Research Center, Cambridge, Massachusetts, under Air Research and Development Command” (pg. 39). What the “other munitions” were, Stine does not say.
Miller recorded the difficulties. “Military specifications were deficient.” There were “engineering difficulties.” There also were storage problems, given the need to keep biological agents within certain temperatures, and the amount of time needed for such agents to be stored. “In addition,” Miller wrote, “Headquarters Command protested that its mission was hampered by the lack of definition of policy” regarding use of biological weapons (Miller, pgs. 113-114).
In the latter stages of the program, there were differences over how and where the bomb would be filled with biological agents. Would that occur inside the “Zone of the Interior,” i.e., inside the continental U.S, or would the materials be shipped abroad for assembly closer to the intended target sites?
There were bureaucratic disputes as well. Air Materiel Command (AMC), from which ARDC had been spun off in 1951, was upset because there was no AMC monitor on the Flying Cloud project. Air Force headquarters personnel were similarly upset when the E77 munition was left off an Air Force “operating document” without their knowledge. Meanwhile, the Air Force Deputy Chief of Staff for Operations at one point failed to approve the operational and logistic concept for a balloon delivery system.
This all led to a “staff study [by Special Weapons Division] which concluded that balloons were not suitable for delivery of biological warfare agents and a recommendation that work on all such systems be discontinued” (Miller pg. 114), a conclusion the Chemical Corps itself did not agree with (as described further below).
Compartmentalization and Secrecy
Somehow, the program lumbered ahead anyway. It certainly had its defenders and proponents within the BW research community. The controversy over WS-124A is more understandable if we realize that, contrary to what the public has been told for decades, the Japanese did successfully find a way to position biological warfare agents on some of the balloons they sent over North America in the closing months of World War Two. But it’s not clear how widely distributed that knowledge was throughout the military.
As early as 1947, the Chemical Corps wrote in its in-house history of the Chemical Warfare Service during World War II, “Biological Warfare Research in the United States” (PDF, pg. 527):
The Japanese balloon was well-adapted to spread biological warfare agents, particularly for serious epidemics of livestock. The balloon incidents prove that the U.S. and Canada are open to this form of attack from the Asiatic mainland.
Peebles’ history presents a couple instances where U.S. scientists or government contractors relied on technical innovations found in Japan’s Fu-Go balloon bombs. Besides the work of the NYU group discussed above, another instance concerned the gondola for the Gopher surveillance balloons, developed around the same time as the Flying Cloud project. Gopher’s gondola leaned on the Japanese model as a “starting point” (Peebles, pp. 104-105).
In his discussion of the Fu-Go balloons, Peebles concluded.
The real importance of FUGO was technical: it was the first balloon to travel vast distances at a controlled altitude. These were two of the technical accomplishments [distance and control] necessary for the U.S. reconnaissance balloon program that was to follow a decade later. [pg. 81]
Yet, whatever reliance the U.S. military scientists had upon the Fu-Go experience was still kept secret, even among the scientists working on the project. Japan’s BW expertise, whether that of Unit 731’s biological warfare experiments, or Noborito’s balloon barrage program, was something to be denied, the better to protect the then-highly secret collaboration between Imperial Japan’s scientific experts and the U.S. military and CIA. Inside Japan, military records for both the balloon and BW programs had been destroyed at the end of the war.
How did the compartmentalization of secret programs work? One pertinent anecdotal example was described by Bernard “Duke” Gildenberg, who worked on classified Skyhook balloon projects at Holloman Air Force Base. In a 2004 article for Skeptical Inquirer, Gildenberg described working on the Moby Dick balloon surveillance balloon:
Late in 1952, I spent a month at Edwards AFB, California, to forecast three-day trajectories for Moby Dick flights, as specified in my travel orders. Forty years later, I discovered from Peebles's The Moby Dick Project (Peebles 1991) that I actually had been working on a top-secret program called Flying Cloud, WS-124A!
Skyhooks were to be evaluated as a balloon bomber in the event of an actual war. Proposed payloads included nuclear warheads, but the program was abandoned as intercontinental ballistic missiles became viable.
Such compartmentalization is also apparent in Stine’s May 1953 “status report” on the balloon bomb program mentioned throughout this article.
Stine wrote, “There is no known predecessor to the E77 bomb as a method of disseminating biological warfare agents.”
He continued:
“… it was not until World War II that any nation deliberately planned and executed a large-scale balloon delivery system for the express purpose of delivering munitions upon an enemy. During the latter part of World War II, the Japanese launched a well-planned and implemented mass balloon attack upon the North America continent. The balloons, in this instance, carried incendiary or fragmentation bombs. During a six-month period, the Japanese launched 9,000 balloons which crossed the Pacific Ocean at altitudes of 30,000 to 35,000 feet, MSL [Mean Sea Level]. Although only 283 units were located, it has been estimated that at least 1,000 balloons reached this continent, the distribution ranging from Southern Canada to central Texas and as far east as Iowa.” (PDF pg. 38)
We know from the FBI documents that I analyzed and offered for download last month that some of the balloons carried anthrax, and quite possibly bubonic plague. Moreover, the 1950 FBI document, for which I obtained further declassification from the National Archives, included a Canadian report that showed there were Japanese balloon landings in far northern Alberta, some 600-700 miles north of the U.S. border.
What did Stine really know, and what did he consciously hide? We will likely never know. But this compartmentalization of intelligence data is precisely calculated to keep things secret, and even years — decades! — later, it still keeps things secret, or at least very difficult to interpret.
One thing Stine did feel certain about in his May 1953 report, the balloon program was no failure. He concluded, “Sufficient success has been achieved with this program to indicate that a balloon-delivery system is feasible for delivering a payload to a designated area. This forms a justification for the development of the E77” (pp. 38-39).
The Weapon’s Design
Stine’s report provided a good overview of the E77 bomb, and how it was used to spread biological agents over a target.
The bomb itself weighed 80 pounds. It was “intended primarily for the dissemination of dry anticrop pathogens” via “a free-flight balloon” (pg. 36). The bomb carried five BW agent containers. The containers held 16-1/2 pounds of “carrier” and 1-3/4 pound of agent fill.
A relatively short discussion of the E77 bomb in the July 1953 Seventh Annual Report of the Chemical Corps Biological Laboratories further described the containers. Each container held “approximately 3-1/2 lbs. of feathers and anti-crop pathogens... grouped centrally around a chemical type heater which maintains the proper temperature control for preserving viability of the fill” (pp. 61-62).
The heating element was “of the exothermic-reaction chemical type,” utilizing water in contact with a mixture of sodium monoxide and granular aluminum (Stine, pg. 37).
The five containers were placed inside a cylinder “32 in. in diameter and 24 in. high.” The cylinder was made of “wood-reinforced fibreboard… lined with 2 in. of styrofoam insulation” (Seventh Annual Report, pg. 61). Non-metallic materials were used as much as possible in order to evade enemy radar.
All sources I’ve examined state the bomb was to be dropped by a combination of timer and barometric sensitive devices, though at least one test utilized radio control release. Stine described a “master time switch” used to release the bomb. The bomb cylinder was to then fall away from the main balloon and a parachute (or “dragshute”) would open and the bomb would slowly descend down to a pre-selected altitude of some 1,000 to 5,000 ft.
In quite an ingenious fashion, a barometric switch would determine when the proper altitude had been reached, and the bomb would open “in a clamshell fashion,” ejecting the five containers along with the heater system. As the agent containers fell, according to Stine’s account, “an arming lever is released that permits a spring-actuated, hollow plunger to puncture a small carbon dioxide bottle. The released gas pressure moves a sliding disc which in turn forces the agent-carrier fill from the container in the form of an extended column” (Stine, PDF pg. 37).
Once released, out would come the contaminated chicken or turkey feathers, or paper bits permeated with wheat rust or other anti-crop pathogen, spreading over a wide area. Released during the spring months, the new crops were more susceptible to infections and artificially induced disease. The result would be — military scientists gruesomely hoped — widespread crop failure and famine. If nothing else, like other bioweapons, the attacks would induce panic and fear among the “enemy.”
Stine was enthusiastic. “There are many agent candidates that may be carried in this balloon,” he wrote, remarking that Flying Cloud could also be used as an “antianimal munition.”
“By adding a suitable antianimal fill such as a pellet, the bomb could be transformed into an antianimal munition, Stine wrote” (PDF pg. 39).
According to Peebles’ account, the bomb would contaminate “an area comparable in size to that affected by a low-yield nuclear weapon” (Peebles, pg. 128).
According to Nicholson Baker’s article mentioned earlier, a December 15, 1951 Air Force memo baldly stated, “The anti-crop program is aimed at the bread basket of the Soviet Union.”
In addition to the heating system, there was a “neutralizer system” meant to detoxify the agent fill within minutes if necessary. This was essential so accidental release didn’t contaminate “friendly” forces. The neutralizer would permeate the container fill with sulphur dioxide if one of three conditions were met: the balloon failed to reach 20,000 feet altitude in one-and-one-half hours; or the balloon were to descend by 600 ft. or more during its ascent to 20,000 feet; or the balloon descended back to 20,000 feet or less after having spent up to 48 hours at 22,000 ft. or greater altitude (Stine, PDF pg. 37).
Getting Off the Ground… or Not
According to Stine, the balloon bomb entered its “final engineering stages” and was ready for its finishing tests in the summer of 1953. As it was, the definitive testing really didn’t occur until autumn 1954.
According to Miller’s history, the concept of the balloon BW bomb and delivery system was agreed upon “orally” by Air Materiel Command and Wright Air Development Center in November 1953. Yet Air Staff was still “reluctant to commit resources and and activate units until test results showed the use of balloons to deliver biological munitions to be practical” (pg. 115).
As I interpret this, for all the secrecy around Japan’s experience, it did not seem that their use of BW in the Fu-Go balloons had been all that successful, or the dataset to determine this was still way too small. As a result, top officials may have felt it was not enough to rely on Japan’s experience. The new engineering efforts had to be exactingly assessed.
A new set of tests were organized. Between October and December 1954, forty-one balloons were launched from Vernalis, California, with most of them traveling some 1500 miles eastward. The tests were meant to simulate combat conditions. The experiments supposedly proved “the military characteristics for the 124A system had been met.” Moreover, the balloon “could be considered a general purpose carrier and could be flown with the E77 bomb or an equal weight payload for any purpose contemplated in balloon probing or transport systems” (Miller, pg. 116, italics added for emphasis).
According to Gildenberg’s article above, the balloon was also considered for a possible nuclear payload, though I’ve never seen any other source mention this. Peebles’ book stated that WS-124A would be compatible with the balloons developed by Project Grandson for Soviet high-altitude surveillance. Instead of cameras, the balloons would carry biological or chemical weapons. They might also be used to drop biological weapons that relied on insect or animal vectors.
In addition, unlike the regular Skyhook-type surveillance balloons, Flying Cloud was designed to “be launched in much worse weather conditions than Grandson (winds of 30 knots with gusts up to 45 knots)” (Peebles, pg. 128, parentheses in original).
According to a history of balloon operations at Holloman Air Force Base in New Mexico from 1947-1958, a “covered wagon” was used to house the balloons prior to launch.
This was an invention of Balloon Branch personnel at Holloman, and bore a strong resemblance to the old-style Conestoga wagon. The balloon was completely contained within the "wagon" during inflation and until the moment of launch, at which point a canvas cover was mechanically released on one side and along the headboard, and the balloon was sent on its way. Extended delays in scheduled launch time, and changes of wind direction were much less serious when a launch was conducted in this manner. (pg. 78)
In both Miller’s and Peebles’ accounts, the Vernalis tests were themselves not without controversy. The Air Materiel Command monitor for the project didn't feel the tests met their requirements. The conclusion that the WS-124A system had only a 24 percent probability of hitting a target area was problematic. Maybe up to 40 percent was achievable, some felt, with more operational experience. Also considered problematic was the fact that the test launches had been limited to certain times of the year and subject to the vagaries of the weather.
Peebles described the objections of the Air Forces’s Air Weather Service (AWS). They didn’t believe the October-December time frame had conditions that matched that of the spring period when such weapons were supposed to be used: “The improved accuracy in the late fall was due to the improved, more predictable, weather patterns, not their operational experience” (pg. 130). Furthermore, the sample provided by the test flights was considered too limited. The conclusion that the balloon was operationally ready was, they felt, invalid.
The AWS objections appeared to have been fatal to the program. Yet another reevaluation was planned. When AWS released its report on its objections in August 1955, Flying Cloud had, as Peebles put it, “faded from the scene and with it, a history going back through FUGO….” (pg. 130).
Nicholson Baker has speculated that the anticrop balloon may have been involved in crop failures in Hungary and Ukraine in 1953 and 1956, respectively. But lacking any documentation linking these episodes to known Flying Cloud overflights, there’s nowhere to really go with such theories.
From Genetrix to the U-2
The surveillance balloons also appeared doomed by the end of the decade. Not only did they often fail, with their contents and technology falling into Soviet hands, captured balloons fed Soviet propaganda about U.S. incursions. In any case, the program lost out to the high-flying U2 spy plane, and then later to the satellite surveillance program. The latter used high-technology camera equipment first developed for Grandson and similar balloon projects. Data on Soviet radar use from the balloon overflights were also used in the U2 program.
The use of balloons for BW purposes appeared to have been shelved forever, although we can’t know that for sure. Surely the hullaballoo around the Chinese balloon overflight over America last year was in some part spurred by U.S. institutional memories of both the surveillance and germ warfare uses for such balloons, a staple of U.S. Cold War research.
As a postscript it’s worth noting that just when the biological bomb balloon was being shelved, the use of high-altitude surveillance balloons was operationally accelerating. As one example, in July 1955 the project engineer for WS-124A at General Mills, Marvin Sandgren, submitted a report to the Office of Naval Research titled, “Study of the Feasibility of Using Plastic Balloons to Carry an Array of Loads at an Altitude of 100,000 Ft.”
In December 1955, a skeptical President Eisenhower decided to sign off on the latest iteration of the balloon surveillance program, Project Genetrix.
According to a CIA history of the the high-altitude U-2 and SR-71 spy planes, over the next few months over 500 balloons were sent flying from West European launch sites over East Europe and the Soviet Union. Less than 10 percent of these Genetrix flights were successful in obtaining the photographic reconnaissance data they were designed for. Worse, many of them had fallen into Soviet or East European hands, leading to protests by these countries against U.S. violation of their airspace.
The U.S. claimed the balloons were meteorological in nature, but the Soviets and their allies were not fooled. Only months before, the U.S. had been using balloons to drop propaganda leaflets. There was already a long history of U.S. attempts to overfly Soviet, Chinese, and East Europe territory with both airplanes and balloons. Furthermore, the Soviets were sure they had international law on their side. The Genetrix efforts had resulted in an embarrassing and potentially dangerous Cold War scandal.
The CIA history records the debacle: “All of this publicity and protest led President Eisenhower to conclude that ‘the balloons gave more legitimate grounds for irritation than could be matched by the good obtained from them,’ and he ordered the project halted” (pg. 86).
This wasn’t the final end of the Air Force balloon programs. There was still the episode of the WS-461L high-altitude balloon, the likely child of Sandgren’s efforts, meant to fly up to 100,000 feet, the better to escape Soviet air defenses. Eisenhower had been convinced that the Genetrix scandal would not be repeated.
In Summer 1958, the WS-461L balloons were launched. According to one account, “The overflight operation, named ‘Melting Pot,’ launched its balloons from the deck of the U.S. Navy ship USS Windham Bay (TCVU-92), a World War II escort carrier converted to an aircraft ferry.”
But human error in setting the “cut-down” timers for the balloons meant they didn’t descend over “friendly” territory. They came down in Poland! Yet another public fiasco, and apparently the end of the balloon reconnaissance missions over what was by then a very angry USSR.
The spying baton was passed to the U-2 aircraft, which would have its own history of scandal.