[ExI] Skylon- a plane that can fly anywhere in under four hours!

spike spike66 at att.net
Thu Dec 18 17:07:52 UTC 2014

>... On Behalf Of Keith Henson
Subject: Re: [ExI] Skylon- a plane that can fly anywhere in under four
>>... John I am not going to get too excited by this until I see that they
can make that precooler perform the way they say it will.  I did the numbers
on this a few years ago and they suggested that this precooler would need to
be higher performing than any heat exchanger we have.  If the Brits get it
to work, then I will offer a Jolly good show, chaps, jolly good.

>...Spike, they did.  And indeed the performance is better than any previous
heat exchanger.  The tubing is so fine that the things look like fabric.  I
have seen them up close.

Cool, Keith that gives me confidence in those calculations I did.  It looked
to me like they would need something like that to get sufficient heat
transfer.  In general a pressure tube wall thickness is proportional to its
inner diameter, which makes sense if you look at the equations for hoop
stress in a cylinder.  Greater heat transfer means smaller ID tubes, thinner
walls, and so forth.  My single-digit BOTECs were suggesting a heat
exchanger that would do the job would need tubes smaller than anything I
have seen, which makes them very delicate and subject to leakage.  

The next trick they must have solved is figuring out how to make this heat
exchanger stand up to a shock wave.  Now that's technology indistinguishable
from magic.


>...What amazed me was that these things, with thousands of brazed joints,
don't leak helium.  Keith

Ja, helium wants to be free.  That stuff is hard to contain.  Any tiny crack
or imperfection in any joint or anywhere and it's game over man.


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