Re: The wheel goes round
basically yes.
HOTOL had three main problems.
1 - they wanted full liquifaction of the air, which meant they ended up using waaay more hydrogen than they could burn. SABRE doesn't cool the air down that much, but even then there's spill-over in air-breathing mode.
2 - having the engine at the back led to problems as the centre of mass and centre of lift shifted through the flight profile. This is why SKYLON's engines are on nacelles.
3 - HOTOL had a launch sled which turned out to be a massive pain in the arse. Skylon doesn't.
Also, there are also advances in materials technology that help the design to close as well,
Biting the hand that feeds IT
