BTW... In another recent thread elsewhere, discussion was about one recent earthquake in LA. Back in 1906, San Francisco (City, north of the City of Angels in California) had a rather large earthquake, and around that same time, Alva Reynolds was experimenting with his "Man Angel" around Huntington Beach (a resort just south of LA):
His "rowing balloon" was filled with hydrogen, 34 feet long carrying an 18 pound frame plus passenger weight (adult male.) He was wise enough to understand the "tear drop" shape of a solid slipping through a liquid.
But solving for the volume of a cylinder, "pi" (at 3.14159 approx.), times the radius (distance from the middle to one edge) squared, times the height (length in this case) of 34 feet, and estimating the radius of his balloon as perhaps 10 feet, say 10,681 cubic feet of balloon.
So if carrying say 50 passengers including crew, 534,070 cubic feet of lifting gas (hydrogen).
Per Wikipedia, in part:
Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 1.00794 u, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the universe, constituting roughly 75% of all baryonic mass.
The "problem" maybe? Wikipedia continues:
At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H2.
All sounds good. Except maybe for the bit "highly combustible". That does NOT sound good? H2 was used in the Hindenburg zeppelin, which was destroyed in a midair fire over New Jersey in 1937.
About the Hindenberg here:
http://en.wikipedia.org/wiki/LZ_129_Hindenburg
In part:
A large German commercial passenger-carrying rigid airship.
Elsewhere, about "large", she (?) was 245 metres (804 ft) long and 41 metres (135 ft) in diameter, longer than three Boeing 747s placed end-to-end, longer than four current Goodyear Blimps end-to-end, and only 24 metres (79 ft) shorter than the RMS Titanic.
And:
The design originally called for cabins for 50 passengers and a crew complement of 40.
Cabins??? So our GTA Zeppelin might be though of as perhaps lifting 1/2 the weight of passengers including crew.
But there's still that fire hazard thingee.
Again per Wikipedia:
The duralumin frame was covered by cotton cloth varnished with iron oxide and cellulose acetate butyrate impregnated with aluminium powder. The aluminium was added to reflect both ultraviolet, which damaged the fabric, and infrared light, which caused heating of the gas.
And:
Following the destruction of Hindenburg, the doping compound for the outer fabric covering of Graf Zeppelin was changed: bronze and graphite were added to prevent flammability and also improved the outer covering's electrical conductivity.
And:
Hindenburg was powered by four reversible 890 kilowatts (1,190 hp) Daimler-Benz diesel engines which gave the airship a maximum speed of 135 km/h (84 mph).
So those designs were intended to go faster than most ground vehicle speed limits, with attendant "large" engines.
Again per Wikipedia:
To reduce drag, the passenger rooms were contained entirely within the hull, rather than in the gondola as on the LZ 127 Graf Zeppelin and consisted of two decks. The upper deck, "A", contained the passenger quarters, public areas, a dining room, a lounge, and a writing room. The lower deck, "B", contained washrooms, a mess hall for the crew, and a smoking lounge. Long slanted windows ran the length of both decks.
Hehe... A "mess hall for the crew"??? Sounds a bit "overbuilt" for a day-tripper sight-seeing airship perhaps.
An amusing article from 2011 "A Comeback For Hydrogen Flight?":
http://www.avweb.com/avwebflash/news/AComebackForHydrogenFlight_204202-1.html
Includes:
One purpose of the flight was to demonstrate that modern hydrogen-filled balloons are safe and practical. The price of helium is getting too high for many sport flyers, he said. The two crews flew for about eight hours.
And:
"(Drew) Barrett, who is from Tampa, Fla., told the Record he has flown many types of aircraft, but gas ballooning "is the most perfect and pure flying I've ever done."
But it is of course possible that the citizens of Toronto will want to talk on endlessly about "pubic (sp?) transport" (including subways) instead of having fun and making money for their city, as well as promoting it to the world.