How does an astronaut return from the moon?

Question

The lift off from earth uses most of its gas so how is it able to launch from the moon back to earth?

Answer 1

The aliens help them by towing them behind there space ships and when they reach the earth's atmosphere they release the tow rope.

Answer 2

when astronautes take off, they use 3 main fuel cells to blast off. these three fuel cells eventually are broken off as the run out, and as the rocket increases altitude. to help the climb to the escape velocity, 4,500 mph, they have to loose weight. they drop the empty fuel cells and they end up bruning up for the most part in the atmosphere, and the remains land in the ocean. the lunar module itself doesn't need as much fuel when they are ready to escape the moon. they rely on the moon's gravity, and the earth's gravity to get back to earth. because the moon is obviously less massive than the earth, and object doesn't have to have as much thrust, and velocity, needed to escape the body. the lunar module doesn't actually have that much fuel. it uses about 50% of it to get off the moon, and saves the other half incase it needs to maneuver. the earth's imense gravitational force pulls the module back into the atmosphere. the remaining fuel is used to angle the space craft so it doesn't get destroyed in the entrance.

Answer 3

When Apollo flew to the Moon, it faced the following conditions. On the Earth, the gravity is 6 times more than on the Moon, and the Earth's atmosphere adds a lot of drag to an ascending vehicle, that isn't a factor on the airless Moon.

Next, the final (3rd) stage of the Saturn V is needed to finish the job of reaching the Earth escape velocity of 25,000 MPH. To get into Moon orbit from it's surface, the Apollo LM only needs to get up to 3,000 MPH.

Next, scienceman's answer was 100% wrong in almost every possible way.

" when astronautes take off, they use 3 main fuel cells to blast off."

No, fuel cells in a spacecraft are used to provide electrical power, only. They are NOT rocket engines. They provide zero thrust.

"these three fuel cells eventually are broken off as the run out, and as the rocket increases altitude."

On the Shuttle, there are 3 Main Engines and 2 Solid Rocket Boosters. The solids are discarded about 2 minutes into the flight, and the mains shut down after 9 minutes.

But, as the Shuttle DOESN'T go to the Moon, none of that is at all relevant to the actual question that was asked. That rocket was the Saturn V, none of whose stages were reusable.

"to help the climb to the escape velocity, 4,500 mph, they have to loose weight."

Earth orbit velocity is 17,500 MPH. Trans Lunar Injection velocity is 24,500 MPH.

"they drop the empty fuel cells and they end up bruning up for the most part in the atmosphere, and the remains land in the ocean."

On the Saturn V they drop used up rocket stages, and on the Shuttle, they drop off the used up pair of solid boosters, and later, the now empty external fuel tank. Only the Boosters are fished out of the ocean and re-used.

"the lunar module itself doesn't need as much fuel when they are ready to escape the moon."

True, though I explained why not...

"they rely on the moon's gravity, and the earth's gravity to get back to earth."

No, the Moon's gravity is what the LM has to overcome to get into Lunar orbit, and it is what the CSM has to overcome in order to go back to Earth. Once they leave the Moon's orbit, then they do fall most of the way to Earth, due to it's more powerful gravity. Each body that the spacecraft has to go away from, exerts gravity that they must *overcome*.

"because the moon is obviously less massive than the earth, and object doesn't have to have as much thrust, and velocity, needed to escape the body. the lunar module doesn't actually have that much fuel."

It has enough for the job. If you want to address such issues, saying "more" or "less" isn't particularly informative. Did you also forget to mention that the LM is smaller than a Saturn V?

"it uses about 50% of it to get off the moon, and saves the other half incase it needs to maneuver."

No. Most of the LM Ascent Stage fuel supply is for the engine that puts the craft back into Lunar orbit. The RCS motors use very little fuel, relative to the ascent engine.

"the earth's imense gravitational force pulls the module back into the atmosphere."

Not if the Apollo CSM doesn't fire it's SPS main engine so as to leave the Moon's orbit, which involves accelerating the spacecraft from 3,000 MPH to 5,000.

"the remaining fuel is used to angle the space craft so it doesn't get destroyed in the entrance."

Thats almost right. The returning CSM needs to stay in the right course, so that it hits the atmosphere at an angle that neither skips it off of the atmosphere, nor dives it in and burns up.  

Oh, two astronauts were in the LM when it was on the Moon, and the third astronaut was in the CSM, in lunar orbit. All 3 went home in the CSM, of course.

Answer 4

The Moon has much less gravity than the Earth, thus significantly less fuel is needed to reach escape velocity from the Moon as opposed to the amount needed to escape the Earth's gravity.  Once that velocity is reached, the engines are turned off and the capsule returns to Earth via it's own inertia, picking up more speed as it interacts with the Earth's gravity.

Answer 5

They don't actually land the whole shuttle on the Moon, just a landing pod. The pod then returns to the shuttle, which takes off much easier, since it's still in empty space.

Also, the initial takeoff uses two extra gigantic fuel containers attached to the shuttle. The liftoff uses those, so they simply fall off, but the shuffle also has it's own fuel. After that, traveling through space is much smoother, using less of the shuttle's fuel. When it reaches the Moon it still has most of it's own fuel left.

Going back, it uses much less fuel than getting there, since the shuttle is pulled by Earth's gravity.