[russss]

The liquid nitrogen is just used for the ground tests. On the Skylon itself, this cooling capacity will come from boiling the liquid hydrogen fuel.

[iwwr]

Skylon would basically use the cryogenic fuel as a giant internal heat sink.

A more fanciful application of the concept: http://tvtropes.org/pmwiki/pmwiki.php/Main/StealthInSpace

[felixfurtak]

How is this different to HOTOL ?

[zizee]

Similar concept, different design.