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How did the lunar ascent module get out of the moons gravitational field?

boogawooga - 2009-03-29 03:06:05 - Astronomy Space

If it took millions of horsepower and hundreds of tonnes of fuel to get the astronauts to the moon, how come it looked like it only took a pop under the lunar ascent module to get them back home? I know the moons gravity is only less than 20% of the Earth's, but surely it would take a much larger craft with lots more fuel to escape from the moon's gravity?

Best Answer:

The LEM ascent stage had an engine that could produce about 15,500 N of thrust. The ascender itself had a mass of 4,500 kg. From Newton's laws, F = ma, so a = F/m = 15,500 / 4,500 = 3.4 m/s² Lunar surface gravity is 1.6 m/s², so the resulting acceleration is 1.8 m/s² which is easily enough to get off the moon. Bear in mind there is no atmospheric drag to worry about and the moon's gravity well is much shallower than the earth's.

Answers:

apparently not. please don't start with the "we never went to the moon" thing. all the myths around that conspiracy theory have been debunked.

because the whole moon landing was a carefully crafted hoax. some people really think that. google it, the evidence is actually quite compelling.

You're right. And the scientists were so sure that they had everyone fooled. I guess you get the credit or seeing what everybody else missed for 40 years. Including thousands of other scientists who were not involved and who had no reason to go along with a hoax that would have totally destroyed their profession if discovered.

Oh please.......! The launcher on Earth had to lift not just the lunar ascent module but the descent stage, the command module, the service module and the second and third stage rockets, their fuel, AND the first stage and it's fuel. The lunar ascent module just had to lift itself, and two men. The weight of lunar rocks was pretty much balanced by the cameras and other equipment that was left on the moon.

it would take a lot less energy to escape from moon surface than earth surface. despite what you may think the reason is not mainly the gravitational field of the erath which is stronger than moon. this is in fact the second most important reason. the most important reason is the friction which is caused by atmosphere of the earth. when flying with the speed of a spacecraft (which is few kilometers per second) you hit a great volume of air, which causes a lot of heat (kinetic energy changes to heat). however on the moon, because there is no atmosphere you wont have to recover the huge deal of wasted energy which converts to heat due to friction. therefore you will need a lot lot less amount of energy to get out of moon's surface. this difference is significant enough that you actually wont need much fuel to get out of the surface of the moon if you compare it with the earth.in fact only if you can make a constant force a little more than the gravitational force of the moon on the spacecraft, you can theoretically get out of the surface (newton 2nd law), while this can not be applied to escaping from the surface of the earth because it is not possible to underestimate the huge friction force on the spacecraft. also, don't worry about Apollo mission if you doubt it. the thing is that, moon is geologically dead which means its surface does not change. therefore the changes on the surface that astronauts made there would be there forever. if that is a lie, it will be revealed with a rather big telescope. but I really really doubt it is not true. because if it wasn't true, Russia would claim that it is not true during the cold war.

It simply went into orbit with little effort due to the low gravity of the moon.

First you would have to show that the rocket engine and ascent stage was not capable of producing enough power and light enough for the job in hand. They knew what was required and dealt with it. I think most if not all rocket scientists do not have an issue. ETA, not forgetting that the Saturn V was required to also lift itself and all the gear and fuel including the fuel it needed at that moment to get to the moon and break earths orbit. No mean feat. The CM and LM were part of the package. The ascent stage only had to get from the moon to dock with the CM and did not have to carry all the fuel and other gubbins required. Beauty of the system employed to land.

The LEM ascent stage had an engine that could produce about 15,500 N of thrust. The ascender itself had a mass of 4,500 kg. From Newton's laws, F = ma, so a = F/m = 15,500 / 4,500 = 3.4 m/s² Lunar surface gravity is 1.6 m/s², so the resulting acceleration is 1.8 m/s² which is easily enough to get off the moon. Bear in mind there is no atmospheric drag to worry about and the moon's gravity well is much shallower than the earth's.

The ascent stage only went into lunar orbit. The escape was provided by the bigger engine on the command/service module. However, consider the different requirements. The Saturn V had to launch a fully fuelled Apollo command/service module, plus a fully fuelled lunar module, plus three men and all their consumables, against Earth's gravity to a speed of 25,000 mph. The lunar module had to lift only itself and two men against lunar gravity to a speed of around 3,000mph. Virtually all rubbish was chucked out, including the backpacks and overboots, and even the cameras once the film had been taken out. Also, please consider the fact that the Moon landing footage and all the calculations has been available to be seen by professional rocket scientists for the past four decades. Funny how none of them, from wherever they may come, seem to find any problems with it. If they don't, why do you?