Mercedes Mullins
Space shuttles require a lot of fuel to launch and manoeuvre in space. The amount of fuel needed depends on the space shuttle's design and mission. For example, the NASA Space Transportation System (STS) vehicle, or Space Shuttle, uses two single-engine Solid Rocket Boosters (SRB) in Stage 0, an external tank providing propellant for the three Space Shuttle Main Engines (SSME) in Stage 1, and two Orbital Manoeuvring System (OMS) hypergolic liquid-propellant rocket engines in Stage 2. The external tank holds more than half a million gallons of self-combustible liquid, while the solid rocket boosters contribute two million pounds of rubbery aluminium fuel, generating 85% of the thrust needed for liftoff. The main engines of the space shuttle use liquid hydrogen and liquid oxygen as fuel, which is much more efficient than the fuel used in traditional rockets.
| Characteristics | Values |
|---|---|
| Fuel in the external tank | 629,340 kg (1,387,457 lb) of liquid oxygen (LOX) and 106,261 kg (234,265 lb) of liquid hydrogen (LH2) |
| Fuel in the two solid rocket boosters | 500,000 kg (1.1 million lb) of Ammonium Perchlorate Composite Propellant (APCP) |
| Total weight at launch | 4.5 million pounds |
| Fuel in the main engine | 385,000 gallons of liquid hydrogen and 143,000 gallons of liquid oxygen |
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What You'll Learn
- The space shuttle's main engine uses liquid hydrogen and liquid oxygen
- Solid rocket boosters generate 85% of thrust
- External fuel tanks hold half a million gallons of self-combustible liquid
- The shuttle drops its boosters and external tank before reaching orbit
- Returning shuttles can glide back to Earth without fuel
The space shuttle's main engine uses liquid hydrogen and liquid oxygen
The space shuttle is composed of three main parts: an orbiter that holds the crew and the three main engines, an external fuel tank, and two solid rocket boosters. The external fuel tank (ET) is the component that contains the liquid hydrogen fuel and liquid oxygen oxidizer. The ET supplies the fuel and oxidizer to the three RS-25 main engines in the orbiter under pressure. The RS-25, or Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that burns liquid hydrogen and liquid oxygen propellants, with each engine producing 1,859 kN (418,000 lbf) thrust at liftoff. The RS-25 engine consists of pumps, valves, and other components working together to produce thrust. The fuel and oxidizer enter the orbiter at the umbilical disconnect valves and flow through the orbiter's main propulsion system (MPS) feed lines.
The space shuttle's main engines use a significant amount of liquid hydrogen and liquid oxygen. The main engine uses 385,000 gallons of liquid hydrogen and 143,000 gallons of liquid oxygen. The liquid hydrogen feed line flow rate is 465 lb/s (12,700 kg/min) with the main engines at 104% or a maximum flow of 47,365 US gal/min (2.9883 m3/s). The ET is the largest and heaviest element of the space shuttle when loaded. It consists of three major components: the aft liquid hydrogen (LH2) tank, which is the largest part but relatively light due to liquid hydrogen's low density, the liquid oxygen tank, and the solid rocket boosters.
The liquid oxygen and liquid hydrogen propellants take different routes through the engine. The liquid oxygen sensors allow for the maximum amount of oxidizer to be consumed in the engines, while still allowing for sufficient time to shut down the engines before the oxidizer pumps run dry. The liquid hydrogen line from the low-pressure turbopumps to the high-pressure turbopumps is insulated to prevent the formation of liquid air. Residual liquid oxygen and liquid hydrogen are vented through the engine after shutdown, with the liquid hydrogen venting through the liquid hydrogen fill and drain valves.
The nozzle of the RS-25 engine is bell-shaped, referred to as a de Laval nozzle. The nozzle has an unusually large expansion ratio of about 69:1 for the chamber pressure. The angle of the nozzle walls is varied to reduce pressure around the rim, preventing flow separation. The inner surface of each nozzle is cooled by liquid hydrogen flowing through brazed stainless steel tube wall coolant passages. A coolant control valve is mounted on the combustion chamber coolant bypass duct of each engine, which regulates the amount of gaseous hydrogen allowed to bypass the nozzle coolant loop, controlling its temperature.
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Solid rocket boosters generate 85% of thrust
The Space Shuttle Solid Rocket Boosters (SRBs) are an integral part of the space shuttle's launch system, providing the majority of the thrust required for liftoff. Each shuttle is equipped with a pair of SRBs, which are the largest solid-propellant motors ever flown and designed for reuse. These boosters are approximately 149.16 feet (45.46 meters) long and 12.17 feet (3.71 meters) in diameter, weighing in at a massive 1,300,000 pounds (590 tonnes) each.
The SRBs are responsible for generating an impressive 85% of the thrust needed to propel the shuttle off the ground and into orbit. This equates to roughly 2,800,000 pounds-force (12 MN) of thrust at sea level, increasing to a staggering 3,300,000 pounds-force (14.7-15 MN) shortly after liftoff. This amount of thrust is roughly double the most powerful single-combustion chamber liquid-propellant rocket engine ever flown, showcasing the sheer power of solid rocket boosters.
The primary propellant for the SRBs is ammonium perchlorate, an oxidizer, along with aluminum powder as fuel. Each solid rocket motor on the Space Shuttle holds approximately 500,000 kilograms of propellant, contributing to the massive thrust generated during liftoff. The boosters work in tandem with the shuttle's three main engines to achieve the required thrust for a successful launch.
The SRBs play a critical role in the first two minutes of the shuttle's ascent. After their fuel is exhausted, they are jettisoned from the shuttle at an altitude of about 146,000 to 150,000 feet (45-46 km). The separation sequence involves thrust vector control actuators, ensuring the thrust of each SRB drops below a certain threshold. Following separation, the boosters parachute into the Atlantic Ocean, where they are recovered, examined, refurbished, and reused for future missions.
The Space Shuttle Solid Rocket Boosters are a testament to engineering ingenuity, providing the necessary thrust to launch the shuttle into space while also being designed for reusability. Their contribution of 85% thrust during liftoff highlights their indispensable role in space shuttle launches.
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External fuel tanks hold half a million gallons of self-combustible liquid
A space shuttle consists of three main parts: an orbiter that holds the crew and payload, an immense external fuel tank, and two solid rocket boosters. The external fuel tank holds more than half a million gallons of self-combustible liquid. This fuel is essential for the shuttle's three main engines, providing the necessary propellant to propel the shuttle into orbit.
The external fuel tank plays a critical role in the space shuttle's operation. Its primary function is to store and supply the fuel required by the shuttle's main engines. The tank's capacity is impressive, holding over half a million gallons of self-combustible liquid. This fuel consists of a combination of liquid oxygen and liquid hydrogen, with the former acting as an oxidizer and the latter as the primary fuel component.
The liquid oxygen and liquid hydrogen work together to provide the necessary propulsion for the space shuttle. During the shuttle's ascent, the liquid oxygen ensures the combustion of the liquid hydrogen, enabling the engines to generate thrust. This combination of propellants is chosen due to their high energy density, which provides the required power to lift the shuttle out of Earth's atmosphere and into orbit.
The external fuel tank's design is carefully engineered to accommodate the unique challenges of space travel. Its immense size is necessary to hold the large volume of fuel required for the shuttle's journey. Additionally, the tank is designed to be lightweight, as every pound counts when escaping Earth's gravity. The tank's structure is optimized to balance fuel storage efficiency with weight considerations.
The external fuel tank is an essential component of the space shuttle, and its performance directly impacts the shuttle's capabilities. The amount of fuel it carries determines the shuttle's range and endurance in space. A well-designed tank maximizes fuel efficiency, ensuring that the shuttle can utilize its propellant effectively during ascent and orbital maneuvers. The tank's reliability is also critical, as any malfunction or fuel leakage could compromise the mission's success.
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The shuttle drops its boosters and external tank before reaching orbit
The space shuttle consists of three main parts: an Orbiter Vehicle (OV) or orbiter, two Solid Rocket Boosters (SRBs), and an external tank (ET). The OV is a stubby, airplane-like craft that holds the crew, the payload, and the three main engines. The SRBs are fueled by two million pounds of rubbery aluminium fuel, which generates 85% of the thrust needed for liftoff. The ET holds more than half a million gallons of self-combustible liquid hydrogen fuel and liquid oxygen oxidizer.
The SRBs are jettisoned before the shuttle reaches orbit, after just two minutes of launch. They drop into the ocean, where they are recovered and refurbished for reuse. The ET is jettisoned just before the shuttle reaches orbit, about six minutes after launch. The ET is not reused; it breaks up before impacting the Indian Ocean or the Pacific Ocean, away from shipping lanes.
The OV's three main engines are fuelled from the ET during lift-off and ascent. The ET is the "backbone" of the shuttle during launch, providing structural support for attachment with the SRBs and OV. It is connected to the SRBs and OV by various attachment points and bipods, and also carries electrical signals, controls, fluids, gases, and electrical power between the OV and SRBs.
The OV continues to operate after the SRBs and ET are jettisoned, using its two Orbital Maneuvering System (OMS) engines to complete orbital insertion. By the time the shuttle reaches orbit, 90% of its launch mass has been left behind.
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Returning shuttles can glide back to Earth without fuel
Space shuttles require a significant amount of fuel for launch and orbital operations. The shuttle consists of three main parts: an orbiter, an external fuel tank, and two solid rocket boosters. The external fuel tank holds over half a million gallons of self-combustible liquid, while the solid rocket boosters contribute about two million pounds of rubbery aluminium fuel, generating 85% of the thrust required for liftoff. The space shuttle's main engine uses 385,000 gallons of liquid hydrogen and 143,000 gallons of liquid oxygen.
However, returning shuttles typically burn all their fuel before re-entering Earth's atmosphere and glide back unpowered. This approach leverages the planet's atmosphere to create friction and slow down the shuttle. As the shuttle descends, the atmosphere acts as a brake, reducing its speed. This method addresses the challenge of slowing down during re-entry without relying on fuel.
The absence of fuel during the descent presents a unique challenge: the shuttle must land at the intended runway or be ditched. This constraint led to the construction of lengthy runways at various airports worldwide, such as the 4km runway in Luxembourg and the 5km runway at Kinshasa Airport in Congo.
To address the increased heat and friction experienced during the home stretch, space shuttles are equipped with a heat shield. This shield utilises ablation, where shock waves in the air and a continuous supply of vaporised material carry away the accumulating heat.
Overall, the ability of returning shuttles to glide back to Earth without fuel highlights the innovative strategies employed in space exploration. By exploiting the atmosphere's friction, shuttles can safely return to Earth while conserving fuel resources.
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Frequently asked questions
The NASA Space Transportation System (STS) vehicle, or space shuttle, uses two single-engine solid rocket boosters (SRB) as Stage 0, which provide 85% of the thrust needed for launch. The external fuel tank holds more than half a million gallons of self-combustible liquid. The main engine uses 385,000 gallons of liquid hydrogen and 143,000 gallons of liquid oxygen.
To return to Earth, the space shuttle exploits the planet's atmosphere to create friction and slow down, rather than using fuel. This creates more heat and friction than during launch, so the leading surface of the craft is protected by a heat shield.
The two solid rocket boosters use a mixture of ammonium perchlorate, aluminium, iron oxide, PBAN or HTPB polymers, and an epoxy curing agent. The main engine uses liquid hydrogen and liquid oxygen.
