Post by Anders Hoveland on Feb 1, 2011 18:30:22 GMT -8
The most energetic reaction that is possible for a rocket is a mix of OF2 with a Li-Be alloy. Beryllium and Oxygen together release 24.36 kJ/g. Lithium and Fluorine release 23.75 kJ/g.
While using ozone instead to burn Be would yield 26.26kJ, ozone is sensitive to detonation. Oxygen difluoride will yield 23.8 kJ/mol extra energy than a comparable mixture of O2 and F2. There are 54g/mol for OF2, thus it is calculated that the use of OF2, rather than O2 and F2, should provide an extra 0.44 kJ/g. Lithium is fairly expensive (US$95/kg). Beryllium is much more so ($745/kg). While lithium-Al alloy is already used (as structural material) for that large central brown colored exterior fuel tank on a rocket, this tank is recoverable. The fuel inside the tank has far more mass than the tank itself, so using Lithium as rocket fuel is not economical.
Using a new article: "A New Determination of the Heat of Formation of Oxygen Difluoride" by WARREN R. BISBEE, Rocketdyne Division, North American Aviation
The heat of formation of OF2, with this newly determined value, is 16.994 kJ/mol (0.3147 kJ/g); this calculation does not agree with my earlier one. Wikipedia claims a 24.5 kJ/mol heat of formation, which gives a value of 0.454 kJ/g. Thus, three different values have been calculated for the additional energy OF2 will contribute.
In normal rockets that burn H2 with O2, extra liquid hydrogen is used beyond the stoichiometric quantity. The heat released from formation of water molecules causes the excess liquid hydrogen to boil, and this is what provides the thrust. Liquid oxygen is much heavier than liquid hydrogen, and this is why using extra hydrogen has a higher specific impulse than burning all the hydrogen.
The reaction between Beryllium and oxygen, with liquid hydrogen present, has a higher specific impulse than liquid hydrogen burning with oxygen. The highest specific impulse for a chemical propellant ever tested in a rocket engine was lithium, fluorine, and hydrogen (a tripropellant), which gave a value of 542 seconds (5320 m/s).
While using ozone instead to burn Be would yield 26.26kJ, ozone is sensitive to detonation. Oxygen difluoride will yield 23.8 kJ/mol extra energy than a comparable mixture of O2 and F2. There are 54g/mol for OF2, thus it is calculated that the use of OF2, rather than O2 and F2, should provide an extra 0.44 kJ/g. Lithium is fairly expensive (US$95/kg). Beryllium is much more so ($745/kg). While lithium-Al alloy is already used (as structural material) for that large central brown colored exterior fuel tank on a rocket, this tank is recoverable. The fuel inside the tank has far more mass than the tank itself, so using Lithium as rocket fuel is not economical.
Using a new article: "A New Determination of the Heat of Formation of Oxygen Difluoride" by WARREN R. BISBEE, Rocketdyne Division, North American Aviation
The heat of formation of OF2, with this newly determined value, is 16.994 kJ/mol (0.3147 kJ/g); this calculation does not agree with my earlier one. Wikipedia claims a 24.5 kJ/mol heat of formation, which gives a value of 0.454 kJ/g. Thus, three different values have been calculated for the additional energy OF2 will contribute.
In normal rockets that burn H2 with O2, extra liquid hydrogen is used beyond the stoichiometric quantity. The heat released from formation of water molecules causes the excess liquid hydrogen to boil, and this is what provides the thrust. Liquid oxygen is much heavier than liquid hydrogen, and this is why using extra hydrogen has a higher specific impulse than burning all the hydrogen.
The reaction between Beryllium and oxygen, with liquid hydrogen present, has a higher specific impulse than liquid hydrogen burning with oxygen. The highest specific impulse for a chemical propellant ever tested in a rocket engine was lithium, fluorine, and hydrogen (a tripropellant), which gave a value of 542 seconds (5320 m/s).