[vkou]

My point is that scaling up from sub-orbital to orbital is extremely hard. It's not that far removed from going from airplane to rocket, in terms of complexity.

You're going from having a top speed of Mach 3 to a speed of Mach 27 (Stage separation and max Q at Mach 6 and 5). You're shaving every conceivable weight-adder. You're dealing with a rocket the size of a skyscraper, which crumples in on itself when not filled with fuel.

This isn't AWS, where you scale your app by spinning up a couple new nodes. The difference from a suborbital hop to orbit is increasing your delta-v budget nine-fold.

[anovikov]

Well, not it isn't. Their current rocket must have a delta-v of about 2.5km/s, so we are speaking of about 3.5-4x increase. Yet, that's a lot.

But remember their current rocket uses hydrolox. That isn't an easy fuel mix to work with! Russians for example, still haven't managed it.