Re: Real numbers would be interesting
Yes, the first stage will require more fuel, but fuel is only a tiny part of the cost of the launch. I was amazed when I learnt how little of the launch cost is fuel. Musk's approach is neatly outlined by this:
Musk reiterated the origin of the SpaceX production model, saying fuel is only 0.3 percent of the total cost of a rocket, with construction materials accounting for no more than 2 percent of the total cost, which for the Falcon 9 is about $60 million.
So, the obvious cost savings are to be made by i, making the vehicle more cheaply, and ii, reusing it.
Musk has made the vehicle cheaper to build by:
-using the same propellant in the upper and lower stages means that operationally, you only need to have one set of fuel tanks. If you can imagine a situation where you have a kerosene first stage, hydrogen upper stage, and solid rocket side boosters, you’ve just tripled your cost right there.
- the upper stage of a Falcon 9 is simply a short version of the first stage. That may seem pretty obvious, but nobody else does that. They tend to create upper stage in a totally different way than they create the first stage.
- The Merlin engine — we used it on the upper stage of Falcon 9, on the main stage of Falcon 9 and on the first stage of Falcon 1. So we get economies of scale in use of the Merlin engine.
-Our tanks are friction stir welded, [aluminum] skin and stringer designed as opposed to machined aluminum, [giving us] a 20 fold advantage in the cost of materials, and our stage ends up being lighter …because geometrically, we can have deeper stringers.