Edit: Never mind. wolf550e and cstross are right. If Falcon Heavy flies it will be the 3rd largest rocket (in terms of payload) that has ever flown behind the Saturn V and the Energia.
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I think you're being a little nit-picky. "Largest" is not exactly a precise term but would generally apply to length and width; not exactly the best way to classify launch vehicles.
Payload capability is the important attribute of a launch vehicle and is generally how vehicles are ranked. Using the word "large" for payload capability may not be precise but it is not factually incorrect.
Payload capabilities:
Ares V: 160 metric tons (cancelled)
SLS (Smaller Ares V): 130 metric tons (in development)
Saturn V: 125 metric tons (retired)
Energia: 100 metric tons (retired - one successful flight)
Falcon Heavy: 54 metric tons (in development)
Space Shuttle: 24 metric tons (retired)
Delta IV Heavy: 22 metric tons (in operation)
Proton Rocket: 21 metric tons (in operation)
The Falcon Heavy may end up being the most capable launch vehicle in operations if the re-incarnated Ares V vehicle (SLS) NASA is developing gets canceled again.
Please add this line, for a vehicle which flew and suceessfully put its payload in orbit:
Energya: 100 metric tons (retired)
Ares V and SLS have never flown, yet.
So if Falcon Heavy works and flies before SLS, it will be the third most capable (in terms of mass to LEO) launch vehicle ever flown, not second, and the most capable of those availbale at the time, since the two vehicles which have succesfully lifted more mass are both retired.
Being third and the only one currently availbale should be good enough. There is no need to lie and claim you are second.
... And I'm not sure what the Chinese have got, but it's certainly man-rated and they're planning a manned space station mission early next year, so it's unlikely to be less than 10 metric tons to LEO and could well be a lot more.
Forgot about the Energiya. To bad it only flew successfully once. Had the Soviet Union not crumbled around the same time things may have been different.
Energia flew twice -- once with a Polyus military payload aboard, and once with an unmanned Buran test flight.
The Polyus mission failed because after it separated from the Energia stack it rotated through 360 degrees rather than the intended 180 degrees and instead of inserting itself into orbit it executed a de-orbit burn. Very expensive software error!
The Buran flight -- the Buran shuttle was carried as a payload slung on the side of the Energia launcher, without engines of its own -- was a complete success.
Alas, Energia cost a ton to fly and when the USSR ran out of money it was the first program to be cancelled. However, part of it (the strap-on boosters) remain in service as the Zenit launcher.
There were plans for an extended Energia ("Vulkan") with a 200 ton payload to LEO, presumably for lunar and translunar manned exploration missions. I suspect it would have worked, if the USSR had the money and the motive to build it, given that it was a modular design based on an existing flying stack. More here:
The much-delayed Angara also has variants in excess of 60T, though it's not clear whether these big ones will actually be built (they're dependent on demand, like the never-built Atlas V heavy).
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I think you're being a little nit-picky. "Largest" is not exactly a precise term but would generally apply to length and width; not exactly the best way to classify launch vehicles.
Payload capability is the important attribute of a launch vehicle and is generally how vehicles are ranked. Using the word "large" for payload capability may not be precise but it is not factually incorrect.
Payload capabilities:
Ares V: 160 metric tons (cancelled)
SLS (Smaller Ares V): 130 metric tons (in development)
Saturn V: 125 metric tons (retired)
Energia: 100 metric tons (retired - one successful flight)
Falcon Heavy: 54 metric tons (in development)
Space Shuttle: 24 metric tons (retired)
Delta IV Heavy: 22 metric tons (in operation)
Proton Rocket: 21 metric tons (in operation)
The Falcon Heavy may end up being the most capable launch vehicle in operations if the re-incarnated Ares V vehicle (SLS) NASA is developing gets canceled again.
(added Energia)