"...now I really don't agree with this one. His major whinge is about amortising the development costs over the number of flights, while glossing over the real problems that modular space-assembly approaches have. For example he compares a 100-ton booster with a 10-ton booster - but can you imagine building a space vehicle out of 10 modules??? "

Suppossing a Mars spaceship needs to be 100 ton [or 200 ton] in LEO, how much of that mass is rocket fuel?

Can this 100 ton [or 200 ton] Mars spaceship have rocket stages? Or must it be only a single stage? In other words, does the entire vehicle that leave earth to remain intact- must land on Mars surface and return to Earth as single entity, if not, what kind of stages do you envision would be best for this 200 ton spaceship.