[Mvandenbergh]

For all that effort to reduce oxidiser mass by using atmospheric oxygen, it's still 80% propellant by mass. Saturn V was 85%.

Still impressive if they can make it work, since of course Saturn V wasn't reusable.

[avmich]

So, with Saturn-5 only 15% was dry mass - and with Skylon 20%? That's 33% increase. Moreover, Saturn-5 was staged - and Skylon is single-stage, and have single stage to orbit with 20% dry mass looks somewhat like a miracle.