Hybrid Propellants

Posted on December 12, 2013 by Aerospace Engineering


Rocket Propellants

1) Liquid Propellants

2) Solid Propellants

3) Hybrid Propellants

 

Hybrid propellant engines represent an intermediate group between solid and liquid propellant engines. One of the substances is solid, usually the fuel, while the other, usually the oxidizer, is liquid. The liquid is injected into the solid, whose fuel reservoir also serves as the combustion chamber. The main advantage of such engines is that they have high performance, similar to that of solid propellants, but the combustion can be moderated, stopped, or even restarted. It is difficult to make use of this concept for vary large thrusts, and thus, hybrid propellant engines are rarely built. A hybrid engine burning nitrous oxide as the liquid oxidizer and HTPB rubber as the solid fuel powered the vehicle SpaceShipOne, which won the Ansari X-Prize.

PROPERTIES OF ROCKET PROPELLANTS  
Compound Chemical Formula Molecular Weight Density Melting Point Boiling Point
Liquid Oxygen O2 32.00 1.14 g/ml -218.8oC -183.0oC
Liquid Fluorine F2 38.00 1.50 g/ml -219.6oC -188.1oC
Nitrogen Tetroxide N2O4 92.01 1.45 g/ml -9.3oC 21.15oC
Nitric Acid HNO3 63.01 1.55 g/ml -41.6oC 83oC
Hydrogen Peroxide H2O2 34.02 1.44 g/ml -0.4oC 150.2oC
Nitrous Oxide N2O 44.01 1.22 g/ml -90.8oC -88.5oC
Chlorine Pentafluoride ClF5 130.45 1.9 g/ml -103oC -13.1oC
Ammonium Perchlorate ClH4NO4 117.49 1.95 g/ml 240oC N/A
Liquid Hydrogen H2 2.016 0.071 g/ml -259.3oC -252.9oC
Liquid Methane CH4 16.04 0.423 g/ml -182.5oC -161.6oC
Ethyl Alcohol C2H5OH 46.07 0.789 g/ml -114.1oC 78.2oC
n-Dodecane (Kerosene) C12H26 170.34 0.749 g/ml -9.6oC 216.3oC
RP-1 CnH1.953n ≈175 0.820 g/ml N/A 177-274oC
Hydrazine N2H4 32.05 1.004 g/ml 1.4oC 113.5oC
Methyl Hydrazine CH3NHNH2 46.07 0.866 g/ml -52.4oC 87.5oC
Dimethyl Hydrazine (CH3)2NNH2 60.10 0.791 g/ml -58oC 63.9oC
Aluminum Al 26.98 2.70 g/ml 660.4oC 2467oC
Polybutadiene (C4H6)n ≈3000 ≈0.93 g/ml N/A N/A

 

NOTES:

  • Chemically, kerosene is a mixture of hydrocarbons; the chemical composition depends on its source, but it usually consists of about ten different hydrocarbons, each containing from 10 to 16 carbon atoms per molecule; the constituents include n-dodecane, alkyl benzenes, and naphthalene and its derivatives. Kerosene is usually represented by the single compound n-dodecane.
  • RP-1 is a special type of kerosene covered by Military Specification MIL-R-25576. In Russia, similar specifications were developed under specifications T-1 and RG-1.
  • Nitrogen tetroxide and nitric acid are hypergolic with hydrazine, MMH and UDMH. Oxygen is not hypergolic with any commonly used fuel.
  • Ammonium perchlorate decomposes, rather than melts, at a temperature of about 240 oC.

ROCKET PROPELLANT PERFORMANCE  
Combustion chamber pressure, Pc = 68 atm (1000 PSI) … Nozzle exit pressure, Pe = 1 atm
Oxidizer Fuel Hypergolic Mixture Ratio Specific Impulse (s, sea level) Density Impulse (kg-s/l, S.L.)
Liquid Oxygen Liquid Hydrogen No 5.00 381 124
Liquid Methane No 2.77 299 235
Ethanol + 25% water No 1.29 269 264
Kerosene No 2.29 289 294
Hydrazine No 0.74 303 321
MMH No 1.15 300 298
UDMH No 1.38 297 286
50-50 No 1.06 300 300
Liquid Fluorine Liquid Hydrogen Yes 6.00 400 155
Hydrazine Yes 1.82 338 432
FLOX-70 Kerosene Yes 3.80 320 385
Nitrogen Tetroxide Kerosene No 3.53 267 330
Hydrazine Yes 1.08 286 342
MMH Yes 1.73 280 325
UDMH Yes 2.10 277 316
50-50 Yes 1.59 280 326
Red-Fuming Nitric Acid (14% N2O4) Kerosene No 4.42 256 335
Hydrazine Yes 1.28 276 341
MMH Yes 2.13 269 328
UDMH Yes 2.60 266 321
50-50 Yes 1.94 270 329
Hydrogen Peroxide (85% concentration) Kerosene No 7.84 258 324
Hydrazine Yes 2.15 269 328
Nitrous Oxide HTPB (solid) No 6.48 248 290
Chlorine Pentafluoride Hydrazine Yes 2.12 297 439
Ammonium Perchlorate (solid) Aluminum + HTPB (a) No 2.12 277 474
Aluminum + PBAN (b) No 2.33 277 476

 

NOTES:

  • Specific impulses are theoretical maximum assuming 100% efficiency; actual performance will be less.
  • All mixture ratios are optimum for the operating pressures indicated, unless otherwise noted.
  • LO2/LH2 and LF2/LH2 mixture ratios are higher than optimum to improve density impulse.
  • FLOX-70 is a mixture of 70% liquid fluorine and 30% liquid oxygen.
  • Where kerosene is indicated, the calculations are based on n-dodecane.
  • Solid propellant formulation (a): 68% AP + 18% Al + 14% HTPB.
  • Solid propellant formulation (b): 70% AP + 16% Al + 12% PBAN + 2% epoxy curing agent.

SELECTED ROCKETS AND THEIR PROPELLANTS  
Rocket Stage Engines Propellant Specific Impulse
Atlas/Centaur (1962) 0 1 2 Rocketdyne YLR89-NA7 (x2) Rocketdyne YLR105-NA7 P&W RL-10A-3-3 (x2) LOX/RP-1 LOX/RP-1 LOX/LH2 259s sl / 292s vac 220s sl / 309s vac 444s vacuum
Titan II (1964) 1 2 Aerojet LR-87-AJ-5 (x2) Aerojet LR-91-AJ-5 NTO/Aerozine 50 NTO/Aerozine 50 259s sl / 285s vac 312s vacuum
Saturn V (1967) 1 2 3 Rocketdyne F-1 (x5) Rocketdyne J-2 (x5) Rocketdyne J-2 LOX/RP-1 LOX/LH2 LOX/LH2 265s sl / 304s vac 424s vacuum 424s vacuum
Space Shuttle (1981) 0 1 OMS RCS Thiokol SRB (x2) Rocketdyne SSME (x3) Aerojet OMS (x2) Kaiser Marquardt R-40 & R-1E PBAN Solid LOX/LH2 NTO/MMH NTO/MMH 242s sl / 268s vac 363s sl / 453s vac 313s vacuum 280s vacuum
Delta II (1989) 0 1 2 Castor 4A (x9) Rocketdyne RS-27 Aerojet AJ10-118K HTPB Solid LOX/RP-1 NTO/Aerozine 50 238s sl / 266s vac 264s sl / 295s vac 320s vacuum

 


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