I saw an Apollo lunar program and i learn the whole trip to the Moon took a 3 days..I dont understand this..?

Question

It doesnt make sense to me cause the escape velocity of the Earth´s pull is 7 miles a second.. so u would think that once the spacecraft litterally shoots away from the gravity force it would keep a constant speed in its way to the orbit of the satellite where it would slowdown with retro rockets. At 7 miles a second ( wich is an unbelievable speed) it would take the astronauts 9.5 hours instead of 72 it actually took. Also is it possible to fire any object straight up, not being tangencial to Earth, to overcome our gravity?

Answer 1

It could be done again, but it would cost a lot of money. It's not as simple as getting the car out of the garage and doing a day-trip to Bournemouth. You would need to build yourself a Saturn V rocket and a complete Apollo stack - and get tooled up to do that before you can even start, and get all the infra-structure back into place. Another factor is that NASA's budget is a lot smaller now than it was in the 60's, so things take a lot longer. And the first moon landing sites WERE extensively surveyed from lunar orbit before the moon landings took place. The main factor, though, is that the objectives this time around are quite different, and the spacecraft to be designed are rather bigger and more versatile than they were the first time around.

Answer 2

you seem to be confused.

the escape velocity is the velocity you should have, UPON LEAVIGN THE SURFACE of a body, so that WITHOUT ANY FURTHER ACCELERATION (ie no force acting) you can leave the object's gravitational field.

clearly our rockets are not in that situation, because we do not shoot them out of some giant cannon but instead supply them with engines that keep on burning fuel.

the missions to the Moon kept on burning fuel for quite a while and then went on by inertia - but would have eventually come back to Earth, had they not been aimed at the Moon, and had you waited long enough.

If you had unlimited fuel resources and were not on a hurry, you could get a spacecraft to the Moon and never, say, exceed a very modest speed, say that of a bike - all you'd need would be to apply a force so low, that you'd just barely win over the spacecraft's weight (which obviously decreases w altitude / distance) and so barely accelerate it.


It's a bit as if you want to climb a hill on a bike, say a 200m high (656 ft) hill, with a 5% average slope i.e. distance 4'000m (13'100ft = 2.5 miles).

You can either keep on pushing on the pedals all the time at some modest speed, say 10 mph. It will take you 15 minutes.

Or you could be a bit crazy, and require to not have to pedal at all. In which case you'd need an initial speed of 62.6 m/s = 141 mph. In which case the trip would take just 63 seconds. But of course you'd need a huge amount of energy, much more than in the first option.


Hope this helps

Answer 3

The Apollo missions did take 3 days to get to the moon and here's why...

Once they escape Earth's gravity, they were still being slowed by gravity. If the Earth has enough pull to hold the Moon in orbit, it probably has some impact on the Command Module and Lunar Module as well.

They did not travel in a straight line. They had to 'point' the mission to where the Moon WOULD be in 3 days. So it was a longer trip.

Your 2nd question... I suppose that - if you had a super powerful rocket and pointed straight up, you could just keep going. The impact of gravity, friction, air pressure, guidance systems to allow PERFECT vertical trajectory... are just things to consider.

Answer 4

Sure, you can go like a bat out of hell for 9.5 hours to get there. The only way to stop in time would be to crash into the moon. The time factor has to balance the fact that you have to stop at the other end and be able to do that with the fuel you can carry. It's all about payload due to the type of chemical rockets we use to push the weight we send, against earths gravity pull, all the way there. This leads to the last point. As with all things like martial arts, jewelry repair, flowers, babies, etc... brute force is not always the answer. Sometimes you just can't get there directly from here and you have to go around the block and up the stairs.

Answer 5

But while it takes 7 miles/second to escape the gravity well, that doesn't mean that gravity stops. So they were fighting the pull of Earth's gravity all the way out, which slowed them down below the 7 mps to escape.

Then, too, they couldn't travel in a straight line of ¼ million miles, because the moon was moving in its orbit. So the distance was much greater than 250000 miles.

And they orbited the Earth a few times to adjust things before they hit their transitional window, and orbited again at the Moon before actually touching down. So from launch to touchdown was understandably a longer period than just the distance divided by their speed.

Answer 6

There is a difference of escape velocity and being able to escape earths gravity. Escape velocity is not escape at all. It is the speed at which must be reached so that an object in "orbit" free falls back to earth at the same rate the earth is moving. So that the fall never brings you closer to the ground, because there is always new ground. The moon is held in orbit by earths gravity, so you would have to go farther than the moon to be "out of earths gravity". There is lead time, yes..the target was aimed three days ahead of the moon. the moon is a quarter of a million miles away. 250,000 miles. The Apollo trip was that of:
1- Launch
2- Orbit stabilization
3- The engine firing that caused the spacecraft to leave earth orbit (they have a special name (trans lunar burn or something))
4- Three day travel to the moon
Now I cant quite remember but somewhere around here the LEM was moved out of the housing and brought around to attach to the nose of the command module.
5- Lunar orbit - orbit stabilization
6- LEM detaches and goes for landing - blah blah lunar surface stuff - top half of lem launches for return to command module.
7- Orbit stabilization- trans earth burn and leaving of lunar orbit
8- Lead time 3 days ahead of earth to catch it
9- Direct approach for splashdown
10- Splashdown
While the spacecraft is lunar orbit, no telecommunication is available when she is behind the moon LOS and AOS - Loss and Aquisition of signal. Radio Communication takes 1 1/2 seconds to travel to the moon -(reason for breaks of silence and the "roger beep") Apollo 17 got a great video of lunar launch because a technician on his own was aware of the signal delay and panned the camera to catch the launch (I have the video on file)

Answer 7

Many people above me are close to the right answer but not right on.

It is true, spaceflight is much different than just driving on a road straight to your destination. Because of the effects of gravity, every trajecotry a spacecraft takes is essentially an orbit of a central body. When the Apollo crafts went to the Moon, they never reached escape velocity, which is the velocity required to enter into a hyperbolic orbit that would take the craft out of Earth orbit. Escape velocity depends on where you are in orbit around a body and is calculated as:

V = sqrt(2GM/r) where, M is mass of the central body, G is the gravitational constant and r is the distance you are from the center of that body. (This is a tangential speed as well. To escape at anything other than tangential to a current orbit, the equation changes accordingly)

The Apollo craft instead began by entering a roughly circular orbit around the Earth, performed the maneuvers necessary to prepare for the trip to the Moon, and then fired the TLI thrusters (Trans-Lunar Injection). This actually put them into an EARTH orbit carefully orchestrated to put them on an intercept path to the Moon. If you saw the orbit they took from above it looks like an elongated figure 8. This is called a free return trajectory.

Free return is just that, once the Apollo capsule was on that trajectory, unless they burn their engines, they would simply slingshot around the Moon and be on a trajectory right back to Earth. This was a safety feature built into the mission, in case something went wrong on the way there. Apollo 13 had just burned out of its free-return trajectory to begin preparations to enter Moon orbit when its well-known disaster happened. That's why they had to re-burn to enter back into a trajectory that would take them to Earth.

That said, if nothing does go wrong in the mission, a few burns would pull the craft out of the free-return (which is in Earth orbit still) and then inject them into Lunar orbit. Once there, the missions commenced and the LEM landed. After the mission the LEM's upper stage took off from the surface of the Moon, and docked with the service module. A burn was performed to exit Lunar orbit (actually reaching escape velocity from Lunar orbit) and re-enter into a Earth orbit that would take them home.

I'm sure I just confused the heck out of you and I apologize. To put it simply, there are no straight line paths in space. As soon as you send something in one direction gravity begins pulling on it, and its path changes. Therefore, orbits must always be used to control the flight of a craft through space.

Answer 8

Because of the movement of both bodies, the rocket doesn't make a straight line path from the earth to the moon. It circles the earth then uses that momentum to slingshot to the moon. This takes a bit more time. I've found a site that shows the path of the Artemis project which uses a similar trajectory. There is an illustration of the path there.

Answer 9

The gravitational field of the earth slows the ship as it travels away from the earth. To answer the fake moon travel crap, why would the country spend 14 years, 26 billion dollars, kill 3 astronauts and employ 200, 000 people just to make a movie faking a landing ? I also hear Columbus never made it to the new world. We actually live in spain.

Answer 10

The craft hat to get into orbit first, slowly increase to escape velocity, travel to about halfway, turnaround, begin the slowdown process, get into a good orbit. it was not just a 9.5 hour straight shot.