The Shuttle Fuel Tank: Withstanding Extreme Pressure

The pressure in a space shuttle's fuel tank must be very high to get the vehicle off the ground. The main combustion chamber pressure on the SSMEs at full power is approximately 3,008 pounds per square inch. The Space Shuttle External Tank (ET) was the component of the Space Shuttle launch vehicle that contained the liquid hydrogen fuel and liquid oxygen oxidizer. The ET was the largest element of the Space Shuttle and, when loaded, it was also the heaviest.

The Space Shuttle's main engines have very high pressure

The Space Shuttle's main engines operate at very high pressures. The pressure in the combustion chamber must be high to get the vehicle off the ground, and the turbopumps that feed the engine need to be pressurised to ensure positive delivery into the combustion chamber. The pressure in the Space Shuttle's main engines is approximately 3,008 pounds per square inch.

The Space Shuttle's external tank (ET) was the component of the Space Shuttle launch vehicle that contained the liquid hydrogen fuel and liquid oxygen oxidiser. The ET was the largest and heaviest element of the Space Shuttle. It was the "backbone" of the shuttle during launch, providing structural support for attachment with the Space Shuttle Solid Rocket Boosters (SRBs) and the orbiter. The ET consisted of three major components: the forward liquid oxygen (LOX) tank, an unpressurised intertank that contains most of the electrical components, and the aft liquid hydrogen (LH2) tank.

The ET supplied the fuel and oxidiser under pressure to the three RS-25 main engines in the orbiter. The LOX tank volume is 19,744 cubic feet at 22 psi and −297 °F. The LH2 tank has a volume of 53,488 cubic feet at 29.3 psi and −423 °F. The ET's operation pressure is 32-34 psi for the LH2 tank and 34.7-36.7 psi for the LOX tank.

The ET was jettisoned just over 10 seconds after the main engine cut-off and it re-entered the Earth's atmosphere. Unlike the Solid Rocket Boosters, external tanks were not re-used. They broke up before impact in the Indian or Pacific Ocean and were not recovered.

Cryogenic fuel rockets inject fuel into the engine

Cryogenic rocket engines use a combination of liquid fuel and oxidizer, which are gases that have been liquefied and stored at very low temperatures. The Space Shuttle's main engines require high pressure to propel the vehicle off the ground. The pressure in the combustion chamber is very high, and the fuel is injected into the engine at high pressure.

Cryogenic rocket engines, such as those used in the Space Shuttle, typically have a fuel injector as one of their major components. The fuel injector's role is to deliver the cryogenic fuel and oxidizer into the combustion chamber, where they are ignited to produce thrust. The fuel and oxidizer are pressurized by turbopumps to ensure they are injected into the combustion chamber effectively.

The Space Shuttle's external tank (ET) played a crucial role in this process. The ET was the largest and heaviest component of the Space Shuttle during lift-off and ascent. It supplied the liquid hydrogen fuel and liquid oxygen oxidizer to the three RS-25 main engines. The ET had three primary structures: the liquid oxygen (LOX) tank, the intertank, and the liquid hydrogen (LH2) tank. The LOX tank was at the top of the ET and had an ogive shape to reduce aerodynamic drag and heating. The LH2 tank was at the bottom, consisting of four cylindrical barrel sections and two domes.

The ET also featured a thermal protection system, primarily consisting of spray-on foam insulation, to manage the extremely low temperatures of the cryogenic fuels. This system included preformed foam pieces, premolded ablator materials, and phenolic thermal insulators to prevent air liquefaction.

The pressure in the combustion chamber of the Space Shuttle's main engines was approximately 3,008 pounds per square inch. This high pressure was necessary to generate sufficient thrust for liftoff. The turbopumps played a critical role in pressurizing the fuel and ensuring its delivery into the combustion chamber.

Turbopumps ensure positive delivery into the combustion chamber

The Space Shuttle's external tank (ET) provides the liquid hydrogen fuel and liquid oxygen oxidizer to the three RS-25 main engines in the orbiter. The ET is jettisoned just over ten seconds after the main engine cut-off.

The ET is comprised of three major components: the forward liquid oxygen tank, an unpressurized intertank, and the aft liquid hydrogen tank. The liquid hydrogen tank is the largest part but is relatively light due to liquid hydrogen's low density.

The turbopumps are a critical component in the Space Shuttle's main engines. They ensure a positive delivery of propellants into the combustion chamber by increasing the pressure of the liquid hydrogen and liquid oxygen. The turbopumps consist of two main parts: a rotodynamic pump and a driving gas turbine, usually mounted on the same shaft.

The Space Shuttle Main Engine's (SSME) turbopumps spun at over 30,000 rpm, delivering 150 lb (68 kg) of liquid hydrogen and 896 lb (406 kg) of liquid oxygen per second to the engine. The turbopumps play a crucial role in achieving the required thrust for the Space Shuttle's propulsion.

The RS-25 engines, also known as the SSME, are liquid-fuel cryogenic rocket engines. Each engine can produce 1,859 kN (418,000 lbf) of thrust at liftoff. The engines underwent upgrades to enhance their performance, reliability, safety, and maintenance.

The RS-25 engines have gone through several versions, including the first manned orbital flight (FMOF), Phase I, Phase II or RS-25A, Block I (RS-25B), Block IA (RS-25B), Block IIA (RS-25C), and Block II (RS-25D). These upgrades aimed to improve engine performance, reliability, and reduce maintenance requirements.

In summary, the turbopumps in the Space Shuttle's main engines played a vital role in ensuring the positive delivery of propellants into the combustion chamber, enabling the engines to generate the necessary thrust for the Space Shuttle's propulsion system.

The pressure in the combustion chamber must be higher than the nozzle exit

The pressure in the combustion chamber of a rocket engine must be higher than the nozzle exit to generate thrust. Thrust is the force that propels a rocket or spacecraft and is the result of pressure exerted on the wall of the combustion chamber. The pressure distribution within the chamber is asymmetric, with the pressure decreasing near the nozzle exit.

The section ratio or expansion ratio is defined as the area of the nozzle exit divided by the area of the throat. The nozzle converts the slow-moving, high-pressure, high-temperature gas in the combustion chamber into high-velocity gas of lower pressure and temperature. Since thrust is the product of mass and velocity, a very high gas velocity is desirable. The nozzle is designed to be long enough or have a large enough exit area so that the pressure in the combustion chamber is reduced to match the ambient pressure outside the nozzle.

The pressure in the combustion chamber of the Space Shuttle's main engines, for example, is approximately 3,008 pounds per square inch. The fuel and oxidizer are pressurized by turbopumps to ensure positive delivery into the combustion chamber. The turbopumps on the Space Shuttle Main Engines (SSMEs) exist because without them, the engine would produce very little thrust.

The turbopumps on the SSMEs exist to produce thrust

The Space Shuttle's external tank (ET) is the component that contains the liquid hydrogen fuel and liquid oxygen oxidizer. The ET is the largest element of the Space Shuttle and, when loaded, it is also the heaviest. The ET consists of three major components: the forward liquid oxygen (LOX) tank, an unpressurized intertank, and the aft liquid hydrogen (LH2) tank.

The ET supplies the fuel and oxidizer under pressure to the three RS-25 main engines (also known as the Space Shuttle Main Engine or SSME) in the orbiter. The engines are used for propulsion throughout the spacecraft's ascent, with total thrust increased by two solid rocket boosters and the orbiter's two AJ10 orbital maneuvering system engines.

The RS-25 engine consists of pumps, valves, and other components working together to produce thrust. Fuel and oxidizer from the Space Shuttle's external tank enter the orbiter at the umbilical disconnect valves and flow through the orbiter's main propulsion system (MPS) feed lines. Once in the MPS lines, the fuel and oxidizer each branch out into separate paths to each engine, where they are allowed to enter the engine through pre-valves.

In the engine, the propellants flow through low-pressure fuel and oxidizer turbopumps (LPFTP and LPOTP) and then into high-pressure turbopumps (HPFTP and HPOTP). From these HPTPs, the propellants take different routes through the engine. The oxidizer is split into four separate paths: to the oxidizer heat exchanger, which then splits into the oxidizer tank pressurization and pogo suppression systems; to the low-pressure oxidizer turbopump (LPOTP); to the high-pressure oxidizer pre-burner, from which it is split into the HPFTP turbine and HPOTP before being reunited in the hot gas manifold and sent on to the main combustion chamber (MCC); or directly into the MCC injectors.

Meanwhile, fuel flows through the main fuel valve into regenerative cooling systems for the nozzle and MCC, or through the chamber coolant valve. The MCC cooling system then passes back through the LPFTP turbine before being routed either to the fuel tank pressurization system or to the hot gas manifold cooling system. Fuel in the nozzle cooling and chamber coolant valve systems is then sent via pre-burners into the HPFTP turbine and HPOTP before being reunited in the hot gas manifold and sent into the MCC injectors. Once in the injectors, the propellants are mixed and injected into the MCC, where they are ignited. The ejection of the burning propellant mixture through the throat and bell of the engine's nozzle creates the thrust.

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