[EliRivers]

"Based on the rocket equation"

I understand the whole point of this is that the rocket equation, assuming as it does that you'll be carrying all the fuel you need with you right from the start, doesn't apply until you get to about 28 km up, and once you get to that point you're not starting from zero speed; you're starting at about mach 5.

Anyway, on the the answer to your question. The projected outcome is that the cost per KG of payload into orbit is less. So that's why. Because it will be cheaper.

[7952]

The difference to a conventional rocket is that you have more fuel left at 28 km up. A vertical launch rocket with this kind of engine would also have much of the same benefit. And with none of the extra weight, complexity, and cost of wings, landing gear etc. And that first stage could be reusable based on the SpaceX model.

So why not use the extra fuel to increase payload or have a reusable second stage? This could reduce costs for conventional launch companies, and make Skylon less viable.

The projections would have to make assumptions about development costs. That seems rather hard to predict with any accuracy. Especially considering how revolutionary every part of the craft would need to be.

[avmich]

> And with none of the extra weight, complexity, and cost of wings, landing gear etc.

> And that first stage could be reusable based on the SpaceX model.

Do you see a contradiction in these statements?

[7952]

No?

[avmich]

Specifically, "landing gear" vs. "SpaceX model"?

Don't you think SpaceX uses landing gear?.. You see what I mean?