Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!rutgers!att!cbnews!military
From: amdcad!djm@castle.edinburgh.ac.uk (D Murphy)
Newsgroups: sci.military
Subject: Re: B-70 bomber program
Message-ID: <9865@cbnews.ATT.COM>
Date: 3 Oct 89 13:06:11 GMT
References: <27553@amdcad.AMD.COM>
Sender: military@cbnews.ATT.COM
Organization: Edinburgh University Chemistry
Lines: 33
Approved: military@att.att.com



From: D Murphy 

In article <27553@amdcad.AMD.COM> huntzing@PICA.ARMY.MIL (CCL-S) writes:
>
>Any ideas/comments on why the boron in the fuel?  I always had taken this
>info. at face value & shrugged when it came to how/why.
>
>-hummer

Basically for reasons of thermodynamics. Using hydrides of boron as a fuel
will convert weak B-H bonds to strong borate (B-O bonds) and water. The
energy difference between the fuel and exhaust chemical bonding is the
(roughly) amount of energy you will get out of burning a unit amount of
the fuel.

Unfortunately, boron hydrides are VERY corrosive, and without the ceramics
available today the engines would not have lasted long. In addition, they
are difficult (== expensive) to handle because they tend to be unstable to
water and air. This may be alright in a chemistry lab but poses logistics
problems elsewhere (and severe hazard for ground crews). Finally (I'm not
sure about this, but I rather suspect it would be true) the products of
the reaction would likely be solid. This would impose another degradative
strain on the engines - that of abrasion. It would also cause problems if
the products were volatilized when the engines were running. Once they'd
been shut down you'd get some condensing on the inside of the engines which
could easily lead to the whole thing siezing up.

If they *really* wanted a wonder fuel, they could always have tried
hydrogen :-)

Murff....