Why did it take Appollo 75 hrs to get to the moon?

Apollo rockets to the moon achieved 25,000 mph to escape earth's gravity. It's 250,000 miles to the moon at that speed it would take only 10 hrs to reach the moon. why did it take 75 hrs? The flight path released by NASA in a 1969 press release shows a DIRECT path to the moon. If earth's gravity slows it down then how do the smaller than Saturn V rockets to mars ever make it? and wouldn't the moons gravity counter earth's at some point? also, with limited oxygen and food and water wouldn't they want to get there ASAP?The numbers don't add up.|||Any map showing a direct path to the Moon is an oversimplification for the media. A trip to the Moon involves some tricky navigation, first establishing an orbit around Earth, then an orbit which takes the craft to the Moon, and finally establishing an orbit around the Moon. You can see the actual paths followed by all the Moon voyages in the software Starry Night Apollo.|||The rocket does not continue at that speed. It does slow down some and also you need to take into account that both the earth and the moon are in motion, not stationary, as the rocket is propelled towards the moon. It DOES add up if you are educated in all the variables involved. |||Regardless of what NASA released in 69, it is impossible to fly to the moon in a straight line. The moon after all is orbiting around the world and in 10 hrs. it would have gone almost half way around the world. Also Apollo did not fly there at a steady 25000 MPH. They had to slow down for landing.|||It's not a simple straight line. After reaching orbit, the ship goes through hours of checkouts and prep work before doing a burn to alter it's orbit toward the moon. It's only at that point, btw, that it reached the maximum velocity.





Then, the moon is moving in relation to the earth, so they have to travel a curved path.





Trust me, they took the shortest route they could safely take.


|||Top speeds are achieved over the time of accelleration....the speed is increasded over a time period.As well, the moon and earth are not static entities,they are rotating around each other while travelling through space.


I think the trajectory must be such that one travels to the place the moon will be when one gets there by a curved trajectory that is longer than the actual straight line distance.


The ship must also decellerate somewhat at the otyher end, so this adds time to the flight as well.|||First of all, the answerer above is correct in saying that any image of a direct path to the Moon is a drastic over simplification of the flight path.





The Saturn V rocket's only purpose was to launch the LEM, Command Module, and TLI (trans-lunar injection) motor into Earth orbit. The TLI motor then fired at a tangent to the Earth orbit which extended out the spacecraft's orbit of the Earth to something more elliptical. The orbit taken actually looks like a figure-8 when plotted in 2-D. This is called a free-return trajectory which basically means that if something goes wrong (as with Apollo 13) the space craft will, using the Moon's gravity, automatically "return" to Earth without any engine usage.





Free-return's are very technical and require precise timing. The reason it took 75 hrs to reach the Moon was also that the craft was NOT going 25,000 mph. It never reached escape velocity for Earth's gravity. It was ALWAYS in an Earth orbit until it got close enough to the Moon for the Moon's gravity to become dominant over Earth's.





Gravity is inverse-squared proportional to distance, meaning that as the distance from the source of gravity increases the force reduces by a squared value (i.e. 2 times the distance = 1/4th the gravitational pull in proportion).





The food and oxygen taken on trips to space is delicately balanced with the design of the system at the design phase. This is where they determine how large the craft will need to be, how many people it will carry, how long it will need to stay in orbit, how much power it needs, weight of food, medical supplies, water, oxygen, etc. This is why it takes years and years to develop new spacecraft especially for manned spaceflight.





I would suggest you take some Physics classes, and learn your Newtonian mechanics/laws. This will greatly aid you in understanding how gravity/orbits work. If this is really interesting to you, astrodynamics and aerospace engineering are great fields to get into.|||Yes, the earth's gravity did slow Apollo 11 down. It took 73 hours. The trans lunar injection (TLI) burn was at T+2h 50m 13s, and brought the speed up to 24,300 mph. Lunar orbit insertion was at T +75h 49m 50s, and was behind the moon. By that time, the radial speed relative to earth was zero!





The mars missions are a lot less massive, so a smaller rocket can boost them to higher speeds.





The object was not to get them to the moon asap. The object was to get them to and moon and back as safely as possible, within the (political) deadline. A faster rocket would actually have increased the risk.


|||They didn't actually go in a straight line, and they didn't maintain that constant speed.|||You're right about the 10 hours but their speed was not a constant 25,000mph. When the trans-lunar injection burn ended the spacecraft was traveling at around 25,000 mph. As they headed towards the Moon their speed slowed gradually. Earth's gravity was pulling them back. By the time they entered the Moon's sphere of influence or gravity field the craft had slowed to around 6000 mph. As they continued on, the Moon's gravity took over and as they began to be pulled toward the Moon they began to speed up again. |||You're telling us the numbers don't "add up," but you don't do the numbers right. Before you start criticizing, it would be wise of you to take an elementary orbital mechanics class. You asked this same question a month ago and were given the correct answer then, including the math. That makes this repetition of the question less a request for information and more of an attempt to make a point.





I have the diagrams released to the press in 1969, and I don't see any that is a "direct path" to the Moon. A colleague of mine plotted the actual Apollo orbit to scale using the velocity figures given in the press kit and came up with a trajectory that (when the outbound and inbound portions are combined) is about the shape of an elongated bowling pin. The display you see at Mission control showing that long figure-8 is not too far off scale.





The translunar trajectory was an orbit. That means its velocity varies depending on altitude. And if altitude varies greatly, then so does velocity. The 25,000 mph achieved after the translunar injection (TLI) is the velocity at perigee. The apogee of the orbit is a couple hundred thousand miles in altitude. And the period of such an orbit can also be computed.





Fuel is the limiting factor, not oxygen or food or water. Water is produced in spades as a by-product of the power generator. Oxygen is very compact when stored cryogenically. Fuel, however, is the big deal. A higher-energy orbit requires more fuel for the LOI-1 insertion burn and for the TEI injection burn after lunar orbit operations. That fuel must be carried with them, thus requiring more fuel at TLI.





Smaller rockets deliver payloads to Mars while still being smaller than the Saturn V by first noting that the payloads are vastly less massive than the Apollo stack. But most important, the Hohmann transfer between Earth orbit and Mars orbit does not require vast amounts of energy. The spacecraft is placed into a solar orbit, but it that reference frame it already has all the velocity of Earth's path along its own orbit. The rocket only has to add enough to raise the aphelion to Mars' orbital distance. Your mistake is in trying to make a direct comparison between "rocket to Moon" and "rocket to Mars, which is much farther away."





Sorry, if you're going to try to argue that Apollo's trajectory and time scale are somehow wonky, you'll actually have to exhibit some understanding of how orbits work.|||fuel was, and is, the limiting factor.





please read up on the subject. you clearly need to.





i like _fundamentals of astrodynamics_ by bate, mueller and white. they discuss hohmann transfer orbits, and patched conics for lunar trajectories. just like apollo used.