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Is deep-cryo of LOX a performance uber-alles baby step?
On Saturday, March 5, 2016 at 2:36:40 PM UTC+13, Rick Jones wrote:
All the fun SpaceX have had with launch delays and deep cryo of the LOX (and RP-1?) has me wondering some peanut-gallery thoughts - the purpose behind the deep cryo of the LOX is to be able to fit more in a given size tank right? Why not simply make a bigger tank? I suppose there are follow-on effects, and it does mean a re-tooling, but in terms of operation and such, wouldn't just a slightly larger set of tanks be "easier" than deep cryo of the propellants? rick jones -- Don't anthropomorphize computers. They hate that. - Anonymous these opinions are mine, all mine; HPE might not want them anyway... feel free to post, OR email to rick.jones2 in hpe.com but NOT BOTH... Bigger tanks have larger masses and the performance of a rocket depends on the ratio of mass full versus mass empty. So, its the amount of propellant you can get into the SAME tank! Adding aluminum nanoparticles to LOX/RP-1 has little change on the specific impulse, but radical change on the propellant density. Adding Lithium or Beryllium particles to RP-1 increases both density and specific impulse, so performance is radically improved with these, although Beryllium has significant risk factors with the exhaust when added. http://ntrs.nasa.gov/archive/nasa/ca...9860018652.pdf Also, mass flow rate for a given pump volume increases when the propellant density is higher, so you can get more thrust from the same hardware, increasing thrust to weight by the same proportion. At nominal conditions structure fraction is 4.35% for each stage. With an 8% increase in propellant density structure fraction drops to 4.02%. With a 12% increase in propellant density (the most you can get by cooling) structure fraction drops to 3.89%. A densified super cool propellant with aluminum added is 22% greater density structure fraction drops to 3.57% With a 2.73 km/sec exhaust speed and the nominal values for the Falcon 9 first stage; Take Off Weight: 505,846 kg Propellant: 402,286 kg Structure 22,000 kg Prop Fraction: 0.795 Delta Vee: 4.330 km/sec Stage Load: 81,560 kg Density Increase: 8% 12% 22% - Density enchancement Take off Weight: 538,029 554,120 594,349 kg Propellant Wgt: 434,469 450,560 490,789 kg Structure Wgt: 22,000 22,000 22,000 kg Upper Stage Wgt: 81,560 81,560 81,560 kg Prop. Freaction: 0.808 0.813 0.826 MECO Velocity: 4.498 4.579 4.770 km/sec |
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Is deep-cryo of LOX a performance uber-alles baby step?
William Mook wrote:
Adding aluminum nanoparticles to LOX/RP-1 has little change on the specific impulse, but radical change on the propellant density. Adding Lithium or Beryllium particles to RP-1 increases both density and specific impulse, so performance is radically improved with these, although Beryllium has significant risk factors with the exhaust when added. http://ntrs.nasa.gov/archive/nasa/ca...9860018652.pdf Be that as it may, given that SpaceX wish to re-use at least engines if not entire stages, why would they put solid particles, even "nano" ones, into their liquid fuel - I would think that in addition to whatever those substances did to the performance they would also act like abrasives. Something one may not care about for a single-use engine but I'd think would be something of a downer for engines one expected to re-use. rick jones -- The glass is neither half-empty nor half-full. The glass has a leak. The real question is "Can it be patched?" these opinions are mine, all mine; HPE might not want them anyway... feel free to post, OR email to rick.jones2 in hpe.com but NOT BOTH... |
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Is deep-cryo of LOX a performance uber-alles baby step?
http://www.azonano.com/article.aspx?ArticleID=3085
It appears the issue of erosion is being addressed. Obviously fuels and oxidisers will be formulated with engine longevity in mind. |
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