[7952]

The real question is why would you want to waste payload capacity hauling an aeroplane into orbit.

Skylon uses that extra efficiency to haul extra components into space. Such as the wings, landing gear etc. Based on the rocket equation it will only have usable payload if the mass of the craft can be kept very low. This would require lots of new technology and materials. Even with a better engine that would be very difficult.

The thing is that all that new technology could also be used by Spacex to improve a conventional rocket. And without the extra mass you would have have much higher payload. And the payload could be used by customers and not wasted on wings.

The best way to use new engine is probably to strap it onto a conventional rocket. Less complex and more payload. And maybe that extra payload could allow second stage reuse. That would make things even more competitive.

[andygates]

A payload hit is acceptable if the reusability is very great: they can just truck up bits of spacecraft, fuel for depots, crew modules and so on in many runs.

A fully-featured spaceplane is a paradigm-shifter. SpaceX decided not to try because the tech was too far down the line. Novel propulsion takes decades to prove out, and Reaction are working through it reasonably. The sticking point was the hypersonic precooler, and they've cracked that. A whole-engine scale demonstrator should be a relatively straightforward next step.

[7952]

Why is a space plane a paradigm-shifter?

[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?