[lutze]

Right, excellent.

Except the first stage doesn't run out of propellant does it, because it has to LAND again. Hence my puzzlement.

I know why multi-stage rockets are used... I'm asking why this rocket needs them, since they solve a problem it doesn't have by design.

[jessriedel]

Rockets don't have stages because they run out of propellant, they have stages so that you don't spend 99% percent of your fuel pushing engines and tanks into orbit which you don't need once you get there.

[jlgreco]

> "they have stages so that you don't spend 99% percent of your fuel pushing engines and tanks into orbit"

In fact you can kinda make a rocket that can reach orbit that doesn't have "stages" but rather jettisons engines themselves. Early Atlas rockets did this: they had one set of fuel tanks but two engines. About two minutes into the flight they would jettison one of the engines.

[nawitus]

Are you saying it should be single-stage-to-orbit? That's currently technologically nearly impossible, even if the rocket doesn't need to land back to Earth.

[nanofortnight]

Not as technologically impossible as you might think: http://www.reactionengines.co.uk/space_skylon.html

[tomelders]

I really don't understand why Skylon isn't getting more coverage.

[schiffern]

>they solve a problem it doesn't have by design.

This is where you're incorrect. Not having to accelerate the empty first stage to orbital speed (and back!) is a huge fuel savings.