Fu-Go Submarines

[World B4]

Fu-Go balloon bomb - Wikipedia

en.wikipedia.org

Japanese submarine I-34 - Wikipedia

en.wikipedia.org

Japanese submarine I-35 - Wikipedia

en.wikipedia.org

After months of research, Kusaba's team developed a six-metre (20 ft) prototype balloon capable of flying at 25,000 feet (7,600 m) for 30 hours.[10] The ballons were constructed from five thin layers of washi, a durable paper derived from the paper mulberry (kōzo) bush, which were glued together with konnyaku (Japanese potato) paste. The Army mobilized thousands of teenage girls at high schools across the country to laminate and glue the sheets together, with final assembly and inflation tests at large indoor arenas including the Nichigeki Music Hall and Ryōgoku Kokugikan sumo hall in Tokyo.[11] The original proposal called for night launches from submarines located 600 miles (970 km) off the U.S. coast, a distance the balloons could cover in 10 hours. A timer would release a five-kilogram (11 lb) incendiary bomb at the end of the flight.[12] Two submarines (I-34 and I-35) were prepared and two hundred balloons were produced by August 1943, but attack missions were postponed due the need for submarines as weapons and food transports.[10]

The I-34 and I-35 were Type B1 cruiser submarines with aircraft hangars. I would like to know more about the way they were "prepared", and I can't find any photos of the 20 ft diameter balloons they would have used, despite 200 being made. They would not have been usable for intercontinental launches (those balloons were larger, with a 33ft diameter), perhaps their materials were re-used, or they were destroyed before the Americans could see them?

 

[World B4]

Japanese submarine I-55 (1943) - Wikipedia

en.wikipedia.org

 

[ArmchairSamurai]

http://www.project1947.com/gfb/fugo.htm

I just found this. Scroll down in the "Sources and Notes" section and the article mentions said submarine-launched Fu-Go balloon

 

[ArmchairSamurai]

https://www.airuniversity.af.edu/Portals/10/ASPJ/journals/1968_Vol19_No1-6/1968_Vol19_No2.pdf

Page 71 outlines the six-meter balloon designed by Kusaba. Unfortunately, still no photos. Very detailed accounts though on the manufacture and use of balloons in the war by Japan.

 

[ArmchairSamurai]

https://apps.dtic.mil/sti/pdfs/ADA195038.pdf

Page 2 also mentions the submarine-launched balloons. Overall the paper gives a little more information on the Fu-Go.

Underlying sources for both papers may yield more information...

 

[Nik]

IIRC, the war years fell in a different phase of el-nino / la-nina cycle to original study, so that the winds were much less favourable than expected...

Perhaps fortunate, as even the few whatsits that reached land caused problems. A local forest fire or two, a picnic party decimated...

Can you imagine dozens of local fires merging to a scale we've recently seen ??

Uh, yes, as a couple of years later, the USAF carpet-bombed so-flammable Japanese cities with incendiaries...

 

[Dave_sic]

Fu-Go balloon bomb - Wikipedia

en.wikipedia.org

Japanese submarine I-34 - Wikipedia

en.wikipedia.org

Japanese submarine I-35 - Wikipedia

en.wikipedia.org

After months of research, Kusaba's team developed a six-metre (20 ft) prototype balloon capable of flying at 25,000 feet (7,600 m) for 30 hours.[10] The ballons were constructed from five thin layers of washi, a durable paper derived from the paper mulberry (kōzo) bush, which were glued together with konnyaku (Japanese potato) paste. The Army mobilized thousands of teenage girls at high schools across the country to laminate and glue the sheets together, with final assembly and inflation tests at large indoor arenas including the Nichigeki Music Hall and Ryōgoku Kokugikan sumo hall in Tokyo.[11] The original proposal called for night launches from submarines located 600 miles (970 km) off the U.S. coast, a distance the balloons could cover in 10 hours. A timer would release a five-kilogram (11 lb) incendiary bomb at the end of the flight.[12] Two submarines (I-34 and I-35) were prepared and two hundred balloons were produced by August 1943, but attack missions were postponed due the need for submarines as weapons and food transports.[10]

The I-34 and I-35 were Type B1 cruiser submarines with aircraft hangars. I would like to know more about the way they were "prepared", and I can't find any photos of the 20 ft diameter balloons they would have used, despite 200 being made. They would not have been usable for intercontinental launches (those balloons were larger, with a 33ft diameter), perhaps their materials were re-used, or they were destroyed before the Americans could see them?

the balloons were likely destroyed during the firebombing campaign and i dont know of any photos.


i can only guess what the modifications on the submarines were.

The 33ft FuGo Balloon required a Launchpad with anchorpoints in the ground to tie the balloon down while the lifting gas was introduced.
some similar Launchpad or at least some kind of stabilization device would have surely been helpful in launching the 20ft balloons aswell.

the intercontinental balloon was filled with large ammounts of hydrogen from gas cylinders only one launchsite had a hydrogen generator. (otsu launchsite 1st batallion special balloon regiment)
the limited space on a submarine might have been better used by carrying a hydrogen generator and two boxes of chemicals than
the large and heavy gas cylinders.

so the preperations i would expect are:
1 cleaning the hangar and removing sharp objects to protect the paper balloons
2 installation of anchorpoints on deck to tie the balloon down
3 mounting a small chemical reactor to generate hydrogen

i cannot present hard sources on this topic !
facts on the intercontinental balloon are taken from:
SMITHSONIA N ANNAL S O F FLIGH T ~ NUMBE R 9 Japan's World War II Balloon Bomb Attacks on North America by Robert C. Mikesh

 

[Scott Kenny]

the intercontinental balloon was filled with large ammounts of hydrogen from gas cylinders only one launchsite had a hydrogen generator. (otsu launchsite 1st batallion special balloon regiment)
the limited space on a submarine might have been better used by carrying a hydrogen generator and two boxes of chemicals than
the large and heavy gas cylinders.

A submarine has lots of seawater and lots of electricity. Can just run an electrolysis cell, which also makes oxygen for the sub.

 

[Dilandu]

A submarine has lots of seawater and lots of electricity. Can just run an electrolysis cell, which also makes oxygen for the sub.

You would need about 4,5 kilowatt/hour for each cubic meter of hydrogen. Assuming the volume of 6-meter diameter aerostat is about 113 cubic meters, you would need about 500 kilowatt/hour to fill just one balloon.

Not sure how powerful were dynamos on Japanese submarines, though. US "Balao"-class could provide about 1100 kilowatt while charging batteries.

 

[Dave_sic]

The 1st Battalion at Otsu utilized hydrogen that was generated from caustic soda and ferrosilicon in the following formula. 2NaOH + Si + H20 = Na2Si03 + 2H2 This required more than 2,000 tons of caustic soda to launch 4,000 balloons. The requirement of ferrosilicon was in the same proportion required by the formula—no small amount.
/|\
_|_ [taken from the above mentioned source.]

Electrolysis of untreated seawater is dangerous because of all the chlorides that create chlorine gas, stuff that you dont want on a submarine. the gas is also produced at atmospheric pressure and would require some kind of gasometer if its not compressed.

carrying two crates of chemicals and mixing them to launch maybe 50 ballons per night appears to be easier than electrolysis,
still possible as the submarine has to be surfaced to launch the balloons thus beeing able to run the diesel engines for electricity.

 

[Scott Kenny]

You would need about 4,5 kilowatt/hour for each cubic meter of hydrogen. Assuming the volume of 6-meter diameter aerostat is about 113 cubic meters, you would need about 500 kilowatt/hour to fill just one balloon.

Not sure how powerful were dynamos on Japanese submarines, though. US "Balao"-class could provide about 1100 kilowatt while charging batteries.

I'd expect the dynamos on the Japanese subs to be comparable to the US subs.

The 1st Battalion at Otsu utilized hydrogen that was generated from caustic soda and ferrosilicon in the following formula. 2NaOH + Si + H20 = Na2Si03 + 2H2 This required more than 2,000 tons of caustic soda to launch 4,000 balloons. The requirement of ferrosilicon was in the same proportion required by the formula—no small amount.
/|\
_|_ [taken from the above mentioned source.]

Implies that each balloon would take half a ton of caustic soda and half a ton of ferrosilicon per balloon filled, 1 ton total materials.

I'm having a hard time believing that the balloons would be filled via chemical reaction, since there's a pretty strong limit on how much cargo a sub can carry, both by volume and by weight.

Electrolysis of untreated seawater is dangerous because of all the chlorides that create chlorine gas, stuff that you dont want on a submarine. the gas is also produced at atmospheric pressure and would require some kind of gasometer if its not compressed.

carrying two crates of chemicals and mixing them to launch maybe 50 ballons per night appears to be easier than electrolysis,
still possible as the submarine has to be surfaced to launch the balloons thus beeing able to run the diesel engines for electricity.

yes, the chlorine causes issues, but if you're only wanting the hydrogen you simply vent the oxygen and chlorine overboard while on the surface. The chlorine comes out at the anode along with the oxygen. And you do not have to run the electrolysis cells at atmospheric pressure, the USN Electrolytic Oxygen Generators run at about 2000psi to directly fill O2 tanks (granted, those run on pure water spiked with KOH as the electrolyte, not seawater).

With the sheer weight of chemicals needed, I don't see how filling balloons can be done that way. Call it 5-6 balloons per aircraft carried and 2 balloons per torpedo. With the knowledge that no submariner would go to sea without at least the torpedo tubes loaded, so you only have about 11 torpedo equivalents. 27-28 total balloons if filled using chemicals.

 

[Dilandu]

I'd expect the dynamos on the Japanese subs to be comparable to the US subs.

Not sure about it, Japanese submarines weren't exactly technologically advanced.

 

[Scott Kenny]

Not sure about it, Japanese submarines weren't exactly technologically advanced.

It's simple physics at that point. Need a generator big enough to recharge batteries relatively quickly while on the surface. Even if the subs are still using direct drive diesels and aux generators instead of diesel-electric power.

 

[Tzoli]

Not sure about it, Japanese submarines weren't exactly technologically advanced.

Care to elaborate?
IJN built the largest and longest ranged submarines of the world and had quite an experience with cruiser and aircraft carrying types. Carried good torpedoes as well.
They were not effective because the IJN not used them as convoy hunting units but as support for the fleets.

 

[Dave_sic]

I'd expect the dynamos on the Japanese subs to be comparable to the US subs.


Implies that each balloon would take half a ton of caustic soda and half a ton of ferrosilicon per balloon filled, 1 ton total materials.

I'm having a hard time believing that the balloons would be filled via chemical reaction, since there's a pretty strong limit on how much cargo a sub can carry, both by volume and by weight.



yes, the chlorine causes issues, but if you're only wanting the hydrogen you simply vent the oxygen and chlorine overboard while on the surface. The chlorine comes out at the anode along with the oxygen. And you do not have to run the electrolysis cells at atmospheric pressure, the USN Electrolytic Oxygen Generators run at about 2000psi to directly fill O2 tanks (granted, those run on pure water spiked with KOH as the electrolyte, not seawater).

With the sheer weight of chemicals needed, I don't see how filling balloons can be done that way. Call it 5-6 balloons per aircraft carried and 2 balloons per torpedo. With the knowledge that no submariner would go to sea without at least the torpedo tubes loaded, so you only have about 11 torpedo equivalents. 27-28 total balloons if filled using chemicals.

yeah but those numbers are for the 10m balloon . the 6m balloon has a much smaller volume,
should be roughly 1/5, so you can fill 5 times as many balloons (4.5 calculated)

 

[Scott Kenny]

yeah but those numbers are for the 10m balloon . the 6m balloon has a much smaller volume,
should be roughly 1/5, so you can fill 5 times as many balloons (4.5 calculated)

Okay, though I'd round down to 4 balloons due to losses and impure chemicals.

That's a much better number, maybe 112 balloons filled, and possibly faster than what an electrolysis cell can produce.

 

[Dave_sic]

Okay, though I'd round down to 4 balloons due to losses and impure chemicals.

That's a much better number, maybe 112 balloons filled, and possibly faster than what an electrolysis cell can produce.

even better, i have read my source again and they mention 200 balloons were made for the attack and 2 submarines converted.
that makes a nice and round 100 balloons for each sub like we just calculated and still leaving space for a limited torpedo armament that you suggested.

i also worried that electrolysis might be too slow. the launchstations on land relied on bottled gas from chemical plants (or from the reactor at otsu) while all launchstations were on the shore. building a powerplant and electrolysis station on land is much more easy than installing one on a sub and they still didnt do it.

both options are possible but im more convinced they had a chemical reactor installed than an electrolysis system.

 

[Scott Kenny]

even better, i have read my source again and they mention 200 balloons were made for the attack and 2 submarines converted.
that makes a nice and round 100 balloons for each sub like we just calculated and still leaving space for a limited torpedo armament that you suggested.

i also worried that electrolysis might be too slow. the launchstations on land relied on bottled gas from chemical plants (or from the reactor at otsu) while all launchstations were on the shore. building a powerplant and electrolysis station on land is much more easy than installing one on a sub and they still didnt do it.

both options are possible but im more convinced they had a chemical reactor installed than an electrolysis system.

Fair enough, that's getting into a range I'm comfortable running with chemicals. I'd still rather have an electrolysis unit, but I'm a nuclear submarine sailor. EOGs go down that's a very quick trip to port!

 

[Dave_sic]

Fu-Go balloon bomb - Wikipedia

en.wikipedia.org

Japanese submarine I-34 - Wikipedia

en.wikipedia.org

Japanese submarine I-35 - Wikipedia

en.wikipedia.org

After months of research, Kusaba's team developed a six-metre (20 ft) prototype balloon capable of flying at 25,000 feet (7,600 m) for 30 hours.[10] The ballons were constructed from five thin layers of washi, a durable paper derived from the paper mulberry (kōzo) bush, which were glued together with konnyaku (Japanese potato) paste. The Army mobilized thousands of teenage girls at high schools across the country to laminate and glue the sheets together, with final assembly and inflation tests at large indoor arenas including the Nichigeki Music Hall and Ryōgoku Kokugikan sumo hall in Tokyo.[11] The original proposal called for night launches from submarines located 600 miles (970 km) off the U.S. coast, a distance the balloons could cover in 10 hours. A timer would release a five-kilogram (11 lb) incendiary bomb at the end of the flight.[12] Two submarines (I-34 and I-35) were prepared and two hundred balloons were produced by August 1943, but attack missions were postponed due the need for submarines as weapons and food transports.[10]

The I-34 and I-35 were Type B1 cruiser submarines with aircraft hangars. I would like to know more about the way they were "prepared", and I can't find any photos of the 20 ft diameter balloons they would have used, despite 200 being made. They would not have been usable for intercontinental launches (those balloons were larger, with a 33ft diameter), perhaps their materials were re-used, or they were destroyed before the Americans could see them?

i have info on the small 6m FuGo ballons:
all of them were used as weather balloons and experiment carriers in the development phase for the large 10m FuGo ballon.

this was written in the smithsonian annals of flight 9 paper.

Japan's World War II balloon bomb attacks on North America

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