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 MurphyIn 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....