Sylvie Willis
The Apollo 11 mission was a close call, with astronauts Neil Armstrong and Buzz Aldrin facing multiple challenges, including a fuel warning light that came on when they were just 100 ft (30 m) above the lunar surface. Aldrin recalled that they had about 15 seconds of fuel left when they touched down. The lunar module was a two-stage vehicle with separate engines and tanks for landing and ascent. The descent stage contained two tanks of aerozine 50 fuel, two tanks of nitrogen tetroxide oxidizer, water, oxygen, and helium tanks. The total fuel and oxidizer for the descent stage were 18,184 kg, of which 17,414 kg were consumed.
| Characteristics | Values |
|---|---|
| Fuel remaining when the fuel light blinked on | 15 seconds worth of fuel |
| Total fuel | 18,184 kg |
| Descent fuel | 17,414 kg |
| Ascent fuel | 4,836 kg |
| Fuel density | 793 kg/m^3 |
| Oxidizer density | 1440 kg/m^3 |
| Descent fuel tank diameter | 4 feet |
| Descent fuel tank length | 6 feet |
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What You'll Learn
The Lunar Module had 15 seconds of fuel left when it landed on the Moon
The Apollo 11 mission was a nerve-wracking experience for the astronauts and the team at NASA. The Lunar Module, Eagle, had a fuel capacity of 18,184kg, but when the craft was 100ft (30m) above the lunar surface, a fuel light blinked on. The Eagle dropped 90ft in the next 30 seconds, leaving the crew with 15 seconds of fuel to navigate the final 10ft to the Moon's surface.
The Eagle's descent was a feat that succeeded by the finest of margins. The LM was never at risk of not being able to take off again, as the computer was programmed to auto-abort the landing when it reached the fuel-too-low point. The astronauts also had dedicated abort fuel to return to the Command and Service Module (CSM) in orbit.
The LM was a two-stage vehicle with separate engines and tanks for landing and ascent. The descent stage was the bottom part of the spacecraft and was an octagonal prism 4.2m across and 1.7m thick. It contained the landing rocket, two tanks of aerozine 50 fuel, two tanks of nitrogen tetroxide oxidizer, water, oxygen and helium tanks, and storage space for lunar equipment and experiments. The ascent stage functioned as a single spacecraft for rendezvous and docking with the CSM.
The Lunar Module lifted off from the Moon after 21 hours and 36 minutes on the surface. It docked with the CSM, piloted by Michael Collins, and was jettisoned into lunar orbit. The fate of the LM is unknown, but it is assumed that it crashed into the lunar surface within the following one to four months.
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The LM had two tanks of aerozine 50 fuel
The Lunar Module (LM) of Apollo 11 used Aerozine 50 as fuel for both the descent and ascent stage engines. Aerozine 50 is a 50:50 mix by weight of hydrazine and unsymmetrical dimethylhydrazine (UDMH). It was developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II ICBM rocket engines.
The LM could pump fuel back and forth between the ascent engine and reaction control system (RCS) tanks, which offered some contingency options. Aerozine 50 was chosen over monomethylhydrazine (MMH) due to its higher density and boiling point, and its lower freezing point of -7°C compared to MMH's -52°C.
The LM was a two-stage vehicle, with separate engines and tanks for landing and ascent. The bottom part was the landing stage, while the top part was the ascent stage. The fuel figures were separate for each stage, and each stage had its own fuel that couldn't be used by the other.
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The LM used 17,414kg of fuel to descend to the Moon
The Apollo Lunar Module (LM) was a two-stage vehicle designed for space operations near and on the Moon. The LM used separate engines and tanks for landing and ascent. The descent stage contained the landing rocket, two tanks of aerozine 50 fuel, two tanks of nitrogen tetroxide oxidizer, water, oxygen and helium tanks, and storage space for lunar equipment and experiments.
The descent engine was started as the craft approached perilune, beginning the powered descent. During this time, the crew flew on their backs, relying on the computer to slow the craft's forward and vertical velocity to near zero. Control was achieved through a combination of engine throttling and attitude thrusters, guided by the computer with the aid of landing radar.
The LM descent to the Moon's surface consumed 17,414kg of fuel out of a total of 18,184kg, leaving only 770kg of fuel. This figure includes the weight of the fuel and oxidizer. The fuel and oxidizer are stored separately. The descent stage was left on the Moon when the ascent engine fired, leaving the Moon and docking with the Command and Service Module (CSM).
The Lunar Module was designed after NASA chose to reach the Moon via Lunar Orbit Rendezvous (LOR) instead of direct ascent or Earth Orbit Rendezvous (EOR) methods, which would have involved landing a much heavier, complete Apollo spacecraft on the Moon.
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The LM ascent stage consumed 4,836kg of fuel
The Lunar Module (LM) was a two-stage vehicle, with separate engines and tanks for landing and ascent. The bottom part was the landing stage, and the top part was the ascent stage. The LM ascent stage consumed 4,836kg of fuel. This was in fact just the propellant in the ascent module tanks. The LM descent to the Moon's surface consumed 17,414kg of fuel out of a total of 18,184kg, leaving only 770kg of fuel.
The LM's ascent engine fired, leaving the descent stage on the Moon's surface. After a few course correction burns, the LM rendezvoused with the CSM (Command and Service Module) and docked to transfer the crew and rock samples. The ascent stage was then separated. The LM ascent and descent stages operated as a unit until staging, when the ascent stage functioned as a single spacecraft for rendezvous and docking with the CSM. The descent stage comprised the lower part of the spacecraft and was an octagonal prism 4.2 meters across and 1.7m thick. The LM's development was plagued with problems, and it was overseen by Grumman. The LM became the most reliable component of the Apollo-Saturn space vehicle.
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The LM's descent stage contained two tanks of nitrogen tetroxide oxidizer
The Lunar Module (LM) of Apollo 11 was a two-stage vehicle designed for space operations near and on the Moon. The descent stage, which comprised the lower part of the spacecraft, contained two tanks of nitrogen tetroxide oxidizer, two tanks of aerozine 50 fuel, water, oxygen, helium tanks, and storage space for lunar equipment and experiments. The nitrogen tetroxide oxidizer is a powerful reagent in chemical synthesis, forming an equilibrium mixture with nitrogen dioxide. It is a storable oxidizer that is hypergolic with many fuels, including hydrazine, and can be stored as a liquid at room temperature. This property was discovered by Peruvian polymath Pedro Paulet in the 1890s, and later utilised by Nazi Germany for rocket technology.
Nitrogen tetroxide, or dinitrogen tetroxide, is the chemical compound N2O4. It is produced by the catalytic oxidation of ammonia (the Ostwald process), or through the reaction of concentrated nitric acid and metallic copper. It is commonly referred to as nitrogen tetroxide (NTO) and is a potent oxidizing agent in rocket propellant systems. Its high freezing point has limited its use in certain applications.
The total mass of the LM ascent and descent stages, including propellants (fuel and oxidizer), was 15,103 kg. The descent to the Moon's surface consumed 17,414 kg of fuel out of a total of 18,184 kg, leaving only 770 kg of fuel. However, another source states that the descent stage fuel was 6,975 lbs, and the oxidizer was 11,209 lbs.
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Frequently asked questions
The Apollo 11 lunar module, Eagle, had about 15 seconds of fuel left when it landed on the moon.
The Apollo 11 Lunar Module had a total of 18,184 kg of fuel.
The descent to the moon's surface consumed 17,414 kg of fuel.
The lunar module had 770 kg of fuel left after descending to the moon's surface.
