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Is deep-cryo of LOX a performance uber-alles baby step?



 
 
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  #1  
Old March 6th 16, 02:49 AM posted to sci.space.policy
William Mook[_2_]
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Default 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
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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
  #2  
Old March 8th 16, 08:19 PM posted to sci.space.policy
Rick Jones[_6_]
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Default 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...
  #3  
Old March 8th 16, 10:09 PM posted to sci.space.policy
William Mook[_2_]
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Default 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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