To Victor; Why not just use boosters instead of external tanks?
ICBM's need to be as thin as possible, the wider they are the harder they are to carry, launch, and build silos for.
Actually the US and Soviet space shuttles are good examples to examine in this regard.
The US Space Shuttle is pretty much the equivalent of a C-130 with an enormous belly fuel tank and two large solid rocket boosters to get it moving.
The main engines are in the shuttle and to keep the size of the shuttle small it has an enormous external fuel tank. The problem is that the main engines are not powerful enough on their own to get the shuttle moving so two very powerful solid rocket boosters are fitted to get the whole craft moving.
The Soviet Buran is actually a glider that sits on a powerful rocket that takes it into space.
the different approaches result in different advantages and disadvantages.
the US shuttle takes its powerful engines into space and brings them back... they weigh about 10 tons. This reduces the max payload and acts as dead weight for the period after entering orbit until they are used to deorbit and also the flight back to earth.
the Soviet Buran does not have those big powerful rockets so it can carry more payload.
It also has the enormous advantage that you can take the Buran off the rocket and fit a payload with a fairing and launch that into space as one unit up to 120 tons.
Why ask in the first place if you already know the idea is unpractical? Not that it isn't nice having a conversation...
It is good he asked.... someone might have had a better solution, or another reason why it didn't make sense that he didn't know before....
external tanks seems more safer.
A rocket that size is a bomb... whether the fuel is external or internal... if it blows up then there is no safer.
remember the Challenger failed because one of the o rings connecting the external fuel to the shuttle had frozen and failed... so it was not safer.
There is a reason most modern day ICBM's are solid-fueled.
In terms of safety rocket fuel is rocket fuel... solid rocket fuels are not safer than storable liquids in terms of ICBMs... and liquid fuels are more powerful.