How do rockets come back from the moon?

Question

I know that rockets leave earth by burning up hydrogen, but the thing is the lower part of the rocket sheds off anyways in space. So how do rockets come back to earth. i.e. how did Neil Armstrong come back?

Answer 1

The Apollo system used a procedure called Lunar Orbit Rendezvous.  With this method, the combined Apollo spacecraft entered lunar orbit.  Then a small lander detached and landed on the Moon and returned back from the surface to lunar orbit.  Then after the crew had transferred back into the main spacecraft, it left lunar orbit and returned to Earth.

The important advantage of this plan is that the fuel needed to break lunar orbit and return to Earth didn't have to be carried down to the lunar surface and then back up again.  It remained up in orbit with the Apollo command and service modules.  Since fuel is the heaviest part of just about any spacecraft, not having to take it where it isn't strictly needed (i.e., down to the surface and back) saves on overall fuel usage.  Landing on the Moon would have been much more difficult if they'd had to carry all that fuel with them.

The important disadvantage is that in the early 1960s no one was really sure how to dock and undock two spacecraft.  So NASA used the Gemini project to practice that technique repeatedly.  Nowadays orbital rendezvous is a well-developed skill.  So our new missions will use not only the lunar orbit rendezvous, but will also use an Earth-orbit rendezvous step so that the whole Moon ship need not be launched from Earth in a single rocket.

Many different kinds of fuels can be used to propel spacecraft.  Our largest rockets often use hydrogen and liquid oxygen.  The lunar module, Apollo command module, and some of our modern upper-stages for rockets use a different fuel that was developed for defensive missiles.  Although less powerful than hydrogen, it's more reliable.

EDIT 1:

And again the Moon hoaxers rear their ugly heads.  You can rely on YouTube to educate you, if you wish.  I'll rely upon my college degrees and my 20 years of experience in the aerospace industry and my 25 years' experience as a photographer and photo interpreter.

Note how all the YouTube handwavers immediately dive into every single other conspiracy theory under the sun as soon as you mention any one of them.  And note how all the arguments are vague claims about how governments can't be trusted, and how people must have had this or that motivation.  Not one single attempt to address the actual facts and evidence.  Just a bunch of paranoia-mongering.

I have no clue where you're getting the notion that the Moon landings "aren't so popular."  The conspiracy theorists have been desperately banging the same old drums for 35 years.  They just bring up the same long-debunked arguments and ensnare a new generation of gullible folk.  Among the people who care to live outside YouTube, the Moon landings were real and relevant.

Answer 2

Good question..not really sure...but I do think that when they land again on earth some of them land in the water (I think?)

Answer 3

Armstrong came back in the capsule (the nose of the rocket) which floated back on parachutes after falling into the Earth's atmosphere.  It landed in the ocean where boats retrieved him and the capsule.

Answer 4

It takes less fuel to come back from the moon than it does to get there.

The moon only has a gravitational field 1/6 as strong as the Earths, therefore it takes much less force, and therefore much less fuel to lift off from the moon.

Additionally, while the lunar module landed on the moon, only a small part of it came back up. This further reduces the fuel needed to lift off. From Wikipedia, "The total mass of the module was 15,264 kg, with the majority (10,334 kg) in the descent stage."

So while 15,264 Kg landed on the moon, only 4,930 Kg came back up. It then rendezvoused with the command and service module, which then only had to initiate a small burn to break lunar orbit and literally fall back to Earth the whole way.

Answer 5

They don't. The West was upset because the Russians had first with Sputnik,Laika and Gagarin so iy was all faked. It just looked like they did on the monitors of the control room people and the bad pictures on the TV sets at home

Our governments lie to us all the time and they get away with it because we are all so gullible. In recent memory Saddam's alleged involvement in 911, the WMD, whitewashing the fact that Georgia started the hostilities in the current crisis and so on and so forth. In the past the Watergate scandal and goodness knows what else.

People say that a cover up couldn't have occurred with so many people involved. I say that 80% of them were fooled themselves and it's not difficult to pay people off....

And they keep getting away with it! Had iraq not been such a disaster the US would be at war with Iran right now. They were already halfway through convincing you that Iran is an rvil, backward, aggressive country. Which it's not.

Sorry, but that's the way it is :(

It's interesting that landing on the moon isn't so popular these days...

Even with the gravatational pull of the moon being a fraction of earth's

Answer 6

OK, the sequence of events is this:

The Saturn V rocket launches, the first stage burning liquid oxygen and kerosene.

The first stage burns all it fuel and drops away, leaving the second stage to ignite. The second stage burns liquid oxygen and liquid hydrogen.

The second stage burns out and drops away, leaving the third stage to ignite. The third stage also burns liquid hydrogen and liquid oxygen.

The third stage shuts down once the spacecraft has reached Earth orbit. After a couple of revolutions the thrid stage re-ignites and propels the spacecraft towards the Moon.

The Spacecraft separates from the third stage, turns around, docks with the lunar module (which was carried in the top of the third stage), then pulls away from the third stage. It now coasts the rest of the way to the Moon.

Once they arive at the Moon the spacecraft fires its SPS engine, which burns another type of fuel, to slow enough to be captured into lunar orbit.

The lunar module separates from the spacecraft and fires its own descent engine to slow it down so it can descend to the surface. It fires the engine all the way to touchdown.

After the astronauts have finsihed on the Moon the top part of the lunar module fires its engine and launches into lunar orbit, leaving the descent stage (the gold foil covered bit with the legs) on the surface.

The lunar module docks with the command module, the crew tranfer across, then the lunar module is discarded and the command module fires its rocket engine again to propel the spacecraft out of lunar orbit towards the Earth.

The spacecraft coasts the rest of the way until it hits Earth's atmosphere. Then it is slowed by friction with the air until it is frefalling towards the surface, when the parachutes open and it splashes down into the ocean.

So each stage has its OWN rocket engine with its own fuel supply.  

Answer 7

They go into the Moon's orbit and begin to revolve around the Moon until they gather enough speed and they they leave orbit and are on their way to the Earth! And it's the modules not the entire rocket!

Answer 8

The ascent stage of the lunar module had its own rocket, powerful enough to lift the stage, the two men inside it, and their cargo of moon rocks, from the moon's surface to lunar orbit. In orbit, they rendezvoused and docked with the command/service module, which also had its own rocket, powerful enough to take them out of lunar orbit and put them on an earth-bound trajectory. Once they were back at the Earth, the service module separated from the cone-shaped command module, which re-entered the atmosphere with the three astronauts and their moon rocks in it. Every part of the whole assembly except for the tiny command module at the top of the stack was eventually discarded.

Answer 9

The lunar module had a descent stage - with a rocket.  The top half was an ascent stage - yet another rocket.  All it had to do was make it up into lunar orbit.  They docked with the command module in orbit.  The command module had a rocket that got them out of lunar orbit and back to the Earth.  Then, even the command module dropped off, and the capsule reentered the Earth's atmosphere.

There are some really good NASA videos about this process.  I'm leaving out most of the very cool details.

If it were me, i'd have launched all these little bits into low Earth orbit on smaller rockets, assembled them there, gone to the Moon, and such.  But no.  They launched the whole kit and caboodle on a single Saturn V.  When the Russian N1 failed, they started down a road like that.  If the US had been slower, perhaps the Russians would have made the attempt. The built a lander for a single cosmonaut.