Rocket Fuel: Liquid vs Solid Propellant

• Rocket Fuel and Aviation Fuels are important for integrative studies

Liquid Propellant vs Solid Propellant

• Liquid propellant consists of a mixture of liquid fuel and a liquid oxidizer, which allows for versatility.
• Liquid propellant is more complicated, requires extra weight, but provides better performance.
• Solid propellant is cheaper and simpler, but can't be controlled after ignition.
• Solid propellant is used in rocket boosters since it is more stable and has quick readiness just before launch.

Rocket Fuel

• RP-1 (Rocket Propellant-1 / Refined Petroleum-1) is a highly refined kerosene formulation used as rocket fuel.
• Liquid-fueled rockets using RP-1 are known as kerolox rockets.
• RP-1 was developed in the 1950s and is outwardly similar to kerosene-based fuels like Jet A and JP-8 used in turbine engines, but manufactured to stricter standards.
• RP-1 has a lower specific impulse than liquid hydrogen.
• RP-1 can be stored at ambient temperatures
• RP-1 has a lower explosion risk.
• RP-1 possesses a higher density, resulting in greater energy density
• RP-1 is far less toxic and carcinogenic compared to hydrazine.
• RG-1 and T-1 are highly refined kerosene formulations similar to RP-1.
• RG-1 and T-1 are the main kerosene fuels used in Russia and former Soviet countries.
• RG-1 and T-1 densities are slightly higher, ranging from 0.82 to 0.85 g/mL, compared to RP-1 at 0.81 g/mL.
• Chilling kerosene can achieve higher densities.
• SpaceX revisited this idea for their Falcon 9 rocket, using cooled RP-1 at -7 degrees Celsius to achieve a 2.5-4 percent density increase.
• Using liquid methane and liquid oxygen as propellants is called methalox propulsion.
• Liquid methane has a lower specific impulse than liquid hydrogen.
• Liquid methane is easier to store due to its higher boiling point and density.
• Liquid methane leaves less residue in engines compared to kerosene, benefitting reusability.
• Methane is a powerful greenhouse gas and the second-largest contributor to climate warming after carbon dioxide.
• Methane leaks in transport can substantially contribute to climate change.
• Production of methane on Mars is expected to be possible via the Sabatier reaction.
• Unsymmetrical Dimethylhydrazine (UDMH) is a derivative of hydrazine, often used with nitrogen tetroxide oxidizer and less frequently with IRFNA or liquid oxygen.
• UDMH is stable and can be kept loaded.
• In some kerosene-fueled rockets, UDMH functions as a starter fuel to initiate combustion and warm the rocket engine before switching to kerosene.

Black Carbon

• Black carbon, also known as soot, is a component of fine particulate air pollution.
• Black carbon is formed by incomplete combustion of wood, waste, and fossil fuels, creating carbon dioxide (CO2), carbon monoxide, and volatile organic compounds.
• Black carbon warms the atmosphere by absorbing light and exacerbates warming of air and surfaces in concentrated regions.
• Black carbon alters weather patterns, hinders cloud formation, reduces glacier/ice's ability to reflect light, and impacts ecosystem cycles.
• The substance lasts only days to weeks in the atmosphere but has significant direct and indirect impacts on the climate, snow and ice, agriculture, and human health.
• Black carbon particles are very small, can penetrate deep into the lungs, and facilitate the transport of toxic compounds into the bloodstream.

Aviation Fuel

• Jet fuel (Jet A-1 type aviation fuel, also called JP-1A) is used globally in turbine engines (jet engines, turboprops) in civil aviation.
• Jet fuel is a carefully refined, light petroleum; kerosene for jet fuel.
• Jet A-1 has a flash point higher than 38°C and a freezing point of -47°C.
• Jet A is a similar kerosene fuel type only normally available in the U.S.
• Kerosene-gasoline mixture (Jet B), also called JP-4, is used for military jets.
• Jet B is a blend of about 65% gasoline and 35% kerosene.
• Jet B is used in regions with particularly low temperatures due to its flammability.
• Jet B has a flash point of 20°C and a freezing point as low as -72°C.
• Engines must be suitable for the use of the fuel.
• Aviation gasoline, also called avgas is usually only used in the older piston engines of sports aircraft and small private aircraft that require leaded fuel.

Sustainable Alternatives

• Bio-propane, developed by Orbex, is made from plant and vegetable waste material.
• Bio-Propane reduces carbon emissions by 80% compared to traditional petroleum gas.
• Bio-Propane remains liquid at cryogenic temperatures, so it can easily be mixed with liquid oxygen.
• POP-FAME (Polycyclopropanated Fatty Acid Methyl Ester) is based on the antifungal bacteria Streptomyces.
• POP-FAME will be "more than 50 megajoules per liter after chemical processing," according to a Science News release.
• A popular kerosene-based rocket fuel has around 35.
• POP-FAME is more energy efficient at a lower consumption rate, and because it's biofuel, it produce fewer toxic byproducts.
• Sustainable Aviation Fuel (SAF) is the main term used by the aviation industry to describe a nonconventional aviation fuel.
• SAF's chemical and physical characteristics are almost identical to those of conventional jet fuel.
• SAF can be mixed with conventional jet fuel to varying degrees.
• SAF uses the same supply infrastructure and do not require the adaptation of aircraft or engines so are called “drop-in fuels”.