Japanese
ICBM (Inter-Continental Balloon Missiles)
Attack Against North America!
Attack Against North America!
7 Jan 2015
Not many
folks know much about the Japanese bombardment of the US in the latter stages
of WW-II. But, it’s true. The following story attempts to unravel the mysterious
events.
After the
Japanese attack on Pearl Harbor on 7 Dec 1941, American forces retaliated by
striking the Japanese capital Tokyo and other places on Honshu Island on 18 Apr
1942. Led by US Army Air Force Lieutenant Colonel James Doolittle, the Doolittle
Raid demonstrated that Japan was vulnerable to American air attack.
In turn,
the Japanese government sought ways to seek revenge by striking the US
mainland. Early attempts featured lone submarines bombarding facilities along
the Oregon and California coasts during the summer of 1942. These 3-4 attacks
amounted to nothing more than nuisances and soon ended. However, one group
continued to ponder possible strategies that might actually threaten the US
civilian population or at least might create a panic.
The Fūsen
Bakudan Campaign (風船爆弾, or fūsen bakudan, "Balloon bomb"), or Fu-Go (Windship Weapon)
became, their preferred strategy. (I have coined the term ICBM to spark heightened
reader interest.) The concept was the brainchild of the Imperial Japanese
Army’s Number Nine Research Laboratory. The essence of the Fu-Go was to fly
weaponized balloons across the Pacific Ocean to the US; they would be pushed by
strong upper atmospheric winds. Upon arrival, the balloons would release their
bombs.
The Japanese
had studied these high altitude winds over their
country, traveling from west to east at 80-120 mph. Winds were strongest from
November through March. Later they became known as the polar jet stream.
The Japanese believed that the winds blew across the entire Pacific and beyond.
Typically
the jet stream blew at altitudes above 25,000 ft and below ~ 35,000 ft and thus
would be capable of transporting a large balloon across the Pacific, a three to five day trip of more than 5,000 mi. See an interesting visualization
of a dynamic jet stream surging across the NE Pacific:
The
balloon’s weapon payload (~77 lbs) consisted of four small (11 lbs each) incendiary plus
one high explosive bomb (~33 lbs). After crossing the Pacific it would arrive over US and Canadian shores and
finally release the bombs. The objective was to kill
people, destroy buildings, and ignite fires on farmland and in forests.
Obviously the balloons were unguided, so there could be no specific targets, but
it might serve as a panic weapon to
terrorize the US population. This was
in fact what the Japanese hoped to accomplish. The Japanese analysts had
estimated that perhaps 7-8% might actually deliver their ordnance over North
America.
The Fu-Go
weapon development was lengthy (2.5-years), because the technological problems
were challenging:
- Altitude control system
- Weapon release
- Balloon destruction
- Balloon manufacturing
A
hydrogen balloon expands during the day when warmed by the sunlight, and rises;
then it contracts when cooled at night, and descends. The Japanese
engineers devised a clever control system, driven by an altimeter mechanism that would either activate the dropping of ballast or the release of hydrogen, when appropriate. After launch from Japan coastal sites, the Fu-Go would initially climb to its nominal design cruising altitude of 30,000-ft.
But, as hydrogen gas slowly leaked from the balloon, it would begin to lose altitude. Then when the balloon descended below 25,000 ft, its control system electrically fired a charge to cut loose two small sandbags (7 lbs or 3 lbs each). There were 36 sandbags in total. This action prevented the balloon from descending farther. As shown above, the sandbags were carried on a cast-aluminum, four-spoke wheel that was designed to discard two bags at a time to keep the wheel balanced.
But, as hydrogen gas slowly leaked from the balloon, it would begin to lose altitude. Then when the balloon descended below 25,000 ft, its control system electrically fired a charge to cut loose two small sandbags (7 lbs or 3 lbs each). There were 36 sandbags in total. This action prevented the balloon from descending farther. As shown above, the sandbags were carried on a cast-aluminum, four-spoke wheel that was designed to discard two bags at a time to keep the wheel balanced.
Conversely,
when the balloon rose above 35,000 ft, the altimeter activated a valve to vent
a small volume of hydrogen to stop the balloon’s climb. (This happened during
the day when the sunlight further expanded the gas, causing the balloon to
rise.) Hydrogen was also vented if the balloon's internal pressure reached a critical
level that might cause the balloon to rip apart.
The
altitude control system weighed over 325 lbs, or 4 times more than the bombs.
The 36 sand bags alone weighed over 200 lbs.
Thus
the control system cleverly orchestrated the balloon through three-five days of
flight. The
balloon’s cyclic up and down flight path continued as it drifted (typically
80-120 mph) crossed the Pacific.
When it reached the West Coast
of North America, it was supposed to
have already dropped its 36 ballast sandbags. The next time the balloon dropped
below 25,000 feet, the bombs (also carried on the ballast wheel) were released
as ballast, but with a very different impact! The incendiary bombs were supposed
to start fires wherever they landed.
It was a final flash of gunpowder that released these bombs and simultaneously lit a 64-ft
long fuse that hung from the balloon's equatorial
belt. The fuse slowly burned upward toward the balloon itself. After
burning 84 minutes, the fuse reached the balloon’s equator and ignited a flash bomb that destroyed the entire
balloon canopy. This was intended to remove all evidence the Japanese attack
had taken place.
Initially
each balloon was made of conventional rubberized silk, but it was heavy and
leaked too much gas. An improved balloon material had just been created that
exhibited less leakage and weighed less. A Japanese military order went out for ten thousand
balloons made of washi, a paper
derived from mulberry trees that was impermeable and very tough. Multiple laminations were produced in squares about the size of a road map. The individual pieces were glued together to form three or four laminations using edible konnyaku
(devil's tongue) paste. One balloon envelope needed forty to sixty laminated squares to produce the 32-ft diameter sphere.
Hungry workers stole the paste and ate it. The workers
were fed poorly and worked long hours, six days per week. Many workers were teenage schoolgirls. They assembled the
balloons in many locations throughout Japan. Large
indoor spaces, such as sumo halls, sound stages, and theatres, were required
for the envelope assembly.
The
first balloon was launched on 3 Nov 1944.
The
Japanese soon activated three east coast launch sites on the island of Honshu.
They found that the best time to launch was (1) just after the passing of a
high-pressure front (i.e., cold front), and (2) when local wind conditions were
most suitable, usually several hours prior to the onset of onshore breezes near
sunrise.
Best
launch conditions occurred on only about fifty days during the 1944-45 winter,
when maximum jet stream velocity was present. The combined max launch capacity of
all three-launch sites, all located on the main island of Honshu, was ~200
balloons per day. Twenty eight hundred soldiers manned the sites and were
responsible for the launches and associated support duties.
In
total, the Japanese launched ~9300 balloons that winter. Best estimates are
that less than 800 arrived on the North American continent. Of those, some
285-balloon remnants have been found to date. Little or no physical damage was inflicted; forest fires
were hard to start in mid winter in the Pacific Northwest with so much ground
covered with snow or subject to the intense rainy season. Note that the Pacific Northwest
(Oregon, Washington, and British Columbia) received the brunt of the attacks.
However, there was only one tragic event. On 5 May 1945,
a Reverend Archie Mitchell and his pregnant wife Elsie drove up to Gearhart
Mountain in Southern Oregon (east of Medford) with five of their Sunday school
students, aged 11–14 yrs., to have a picnic.
The group had to stop at a spot near Bly, Oregon, due
to construction and a road closing. Elsie and the children got out of the car
while Archie drove on to find a parking spot. As Elsie and the children looked
for a good picnic spot, they saw a strange balloon lying on the ground. (No one
knows how long it had been there.) As the group approached the balloon, a bomb
attached to it exploded, killing Elsie and all five children instantly. The US
news blackout, in effect since Jan 1945, was immediately called off following
this incident.
With no
evidence of any effect, General Kusaba was ordered to cease operations in April
1945, believing that the mission had been a total fiasco. The expense was
large, and in the meantime B-29s had destroyed two of the three hydrogen plants
needed by the project.
The last fire balloon was launched in April 1945. The
remains of balloons continued to be discovered after the war. Eight were found
in the 1940s, three in the 1950s and two in the 1960s. In 1978, a ballast ring,
fuses and barometers were found near Agness, Oregon and are now part of the
collection of the Coos Historical & Maritime Museum.
A short video clip highlights the Fu-Go program:
Sources:
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