Interesting article on aluminum in rockets

[drwayne]

http://www.aerospaceweb.org/question/propulsion/q0246.shtml<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[chriscdc]

Are only the atoms on the surface of the particles oxidised by this reaction?<br /><br />Have the types of fuel changed alot, as I would expect that the size of aluminium particles would have become more uniform and thus improving its performance as a rocket fuel. <br /><br />I read a week ago a newscientist article about using colloidal iron or aluminium as a fuel medium, for cars. Does anyone know any good (technical) sites about using aluminium as a rocket fuel?

 

[gunsandrockets]

Very very interesting. Thanx for that info.<br /><br />But that leads to a question. Does that mean schemes for using a LOX/Al burning rocket engine (using lunar derived LOX/Al) woudn't be practical? If particles of aluminum oxide clump so readily, I think a pure LOX/Al rocket would suffer from a very poor ISP, wouldn't it? Am I missing something here? Has an experimental LOX/Al rocket engine ever been test fired? What was it's measured ISP?

 

[mlorrey]

It is interesting how 1950's research into high performance fuels is now resurfacing, as people are finally getting deprogrammed from following the NASA party line about "hydrogen is best".<br /><br />As another example, I found some 1960's ramjet missile research that demonstrated that a slurry of kerosene (RP-1 or JP-4) and boron particles offered Isp slightly in excess of LH2, when burned with either LOX or peroxide, while at the same time being a much denser fuel than hydrogen (more than ten times denser). The density advantage means you can get the same Isp while having a much smaller launch vehicle, which ultimately results in lower aerodynamic losses, more payload in orbit, and lower overall fuel consumption.<br /><br />Dunn also has a great article on alternative fuels. For example, common welders MAPP gas, liquified, burned with LOX can put 2.5 times more payload in orbit than an equivalent tankage volume of LH2/LOX. As it is liquid at a temp slightly higher than LOX, you don't get the extreme cryogenic issues of LH2, while still being able to cool your vehicle actively with the fuel before combustion, particularly if you are doing any airbreathing propulsion in the boost phase.

 

[vogon13]

A boron / kerosene fuel mixture was actually ground tested in a jet aircraft engine, once.<br /><br />{The smoke was staggering}<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p>A boron / kerosene fuel mixture was actually ground tested in a jet aircraft engine, once. <br /><br />{The smoke was staggering} <p><hr /></p></p></blockquote><br /><br />Of course it was, as boron combusts with oxygen to become boron oxide, i.e. bauxite, which, when it cools, precipitates as particulates. However, bauxite is not toxic, either. The smoke offends the tree hugging whale shavers, makes bureaucrats nervous about taxpayer lawsuits, and elected officials nervous about reelections, but in no way has ever been demonstrated to be toxic.<br /><br />Frankly, I like a lot of smoke in my rocket launches. Those purely LH2/LOX launches with their invisible light blue flames and zero exhaust smoke are anticlimactic, uninspiring, and contribute to public disinterest in space. You can't have a fourth of july fireworks show without a lot of smoke in the air.<br /><br />Boron/kerosene slurry provides Isp of 457 (varying depending on the percent mixture between the boron and kerosene): slightly better than LH2.<br /><br />Its detractors complain about 'coking' in the exhaust nozzle, but that is simply poor engine design. The thermoelectric /MHD effects of the combustion attract BOX to the walls of the nozzle due to static charging, just like the Sharper Image "Ionic Breeze" grabs dust out of the air. Reversing the current flow and polarity of the engine nozzle will cause the box to be repelled from the nozzle walls.<br />

 

[danwoodard]

>>>boron combusts with oxygen to become boron oxide, i.e. bauxite, which, when it cools, precipitates as particulates. However, bauxite is not toxic, either<br /><br />Bauxite is primarily aluminum hydroxide <br />http://en.wikipedia.org/wiki/Bauxite<br /><br />Boron oxide is not particlarly toxic at lower concentrations, but combustion exhaust would indeed produce dense smoke, as also ocurrs with aluminum fueled rockets.

 

[mlorrey]

Yeah, I misspoke, meant to say borax, which isn't BOx, it is NaBOHx which would occur when the exhaust settled in the ocean and reacted with dissolved sodium.<br /><br />Anyhoo, there are clean burning boron fuels, particularly tetraborane with hydrazine, the boron combusts with the nitrogen to produce BN and you get a lot of hydrogen that you can then combust with either LOX or ram/ejector air. tetrboran and hydrazine alone get 440 sec Isp. Burning the H with air gets you in the thousands, with LOX should get an additional stage of combustion, particularly if you add it after the MMH/tetraborane products expand, as in an MIPCC airstream. I'm not sure how you combine Isp for two combustion stages.

 

[webtaz99]

Aluminun/LOX monopropellant has been tested.<br /><br />http://www.space-rockets.com/lsp.html<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[cdr6]

The U.S. Government operates the largest hydrogen production facility in the world, located in the California desert, the facility was originaly built for the production of fuel for the Apollo program. <br /><br />Hence NASA's choice to go with hydrogen becomes one of cost effeciency, having the necessary production capability already on hand. <br /><br />The choice in reality has very little to do with "party lines" and more with economy in the "CEV" sense.

 

[mlorrey]

Really? Then perhaps you can tell us exactly how much that hydrogen costs NASA to produce, because they won't release it to the public, likely because they would be, once again, embarrassed. Perhaps they can also tell us how much of that hydrogen is produced with energy produced by combustion of oil taken from the strategic oil reserves at a discount (i.e. not market) price. Given the inefficiencies of power generation, transmission, electrolysis, and liquifaction, I highly doubt that they produce liquid hydrogen for less than the cost of purchasing RP-1 from a refinery in bulk.

 

[cdr6]

I don't think that NASA is the operator of the facility, I think it's run by the DOE. <br /><br />NASA buys alot of goods and services from various sources, the processes and cost of which we are not privy to. <br /><br />At Ames we learned very painfully that "civilian" and "cheap" do not necessairly equate out as "cost effective." <br /><br />In purchases of this size no real money actually changes hands between agencies. It is done computer to computer only. In much the same fashion as the FAA fines an airline (for various infractions) where in the airline is forced to carry the mail for "x" number of months for free. The "services part" of the "goods and services" mentioned above.