huntzing@PICA.ARMY.MIL (CCL-S) (09/29/89)
From: "Hugh A. Huntzinger" (CCL-S) <huntzing@PICA.ARMY.MIL> Other B-70 tidbits (recalled from my Undergrad research paper) The problem of supersonic heating was "resolved" by utilizing the fuel supply as a heat sink. Reportedly, if the fuel temperature was above "X" degrees, takeoff was denied. Also on fuel, they (I assume GE) "had to develop" a new fuel to provide greater power for the system (see last week's discussions on thrust/weight) and had developed a probably very expensive **BORON** based fuel. 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
djm@castle.edinburgh.ac.uk (D Murphy) (10/03/89)
From: D Murphy <amdcad!djm@castle.edinburgh.ac.uk> 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....
howard@cos.com (Howard C. Berkowitz) (10/07/89)
From: howard@cos.com (Howard C. Berkowitz) In article <9865@cbnews.ATT.COM>, amdcad!djm@castle.edinburgh.ac.uk (D Murphy) writes: > 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. Again an anecdote from memory, there was a very practical problem with boron-based fuels. The solids problem, in some fuel formulas (not necessarily that of the XB-70), went beyond corrosion: it extended to putting dense white clouds of oxidized boron into the air, such that visibility for the next plane taking off, the tower, landing planes, birds, Russian spies, etc., were all seriously impaired. There is a story of a test, I believe at Edwards AFB, of an early boron experiment -- there was concern that the plane had sufficient fuel to stay aloft until the clouds settled enough for the crew to see the runway. Perhaps readers can contribute details (or anecdotes) of Great Fiascoes in Military Technology [sci.military.snafus, .fubars, or .fubabs]. For example, I have heard tales of two winners: a 1950-vintage interceptor called the XP-72, and a suppposedly advanced weapons control system for an advanced helicopter (Cheyenne?) I saw the XP-72 in a Ground Observer Corps (anyone remember that?) identification handbook in the early 50's. It was a stubby-winged (delta?) jet fighter, with what I can best explain as a beak. I was told the beak was a reinforced nose, and the aircraft was intended for survivable ramming attacks against bombers. Anyone know anything? I heard of the helicopter control system while doing human factors work. The gunner was equipped with a hands-free gunsight slaved to his eye movements. This technology has been demonstrated, and can work. The improvement, however... Allegedly, an additional goal was hands-free control of weapons release. One bit down to fire rockets, twitched the left cheek for guns, etc. Unfortunately, the first test gunner had hay fever. On arming weapons, he sneezed...tightening his face sufficiently to salvo all weapons. Of course, the noise and recoil caused him to toss his head, breaking lock. Between sneezing and recoils, he wiped out most of the range, with incidental damage to the target. It ,o -- howard@cos.com OR {uunet, decuac, sun!sundc, hadron, hqda-ai}!cos!howard (703) 883-2812 [W] (703) 998-5017 [H] DISCLAIMER: Opinions expressed are not necessarily those of the Corporation for Open Systems, its members, or any standards body.