How Can Rockets Travel To The Moon, If MoonTravels at 6mKPM

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Roonyroo
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How Can Rockets Travel To The Moon, If MoonTravels at 6mKPM

16 Feb 2014, 15:05

How can a rocket travel to the moon, if our entire solar system travels at 6million kilometres per hour ...
I'm guessing astronauts routinely get run over by speeding rogue planets on the way to the moon ...

So just how many rockets have we made, which travel at 6 million kilometres per hour, & who gets to clean up 6 million kph pile ups in space ...

Did they paint special fins on that fat ass rocket in the 70's to get it to travel at 6 million kph, or is this the smoking gun all we have is really 6 million kph roadkill in space ...

Buzz aldrin should be flat, not round ... jus saying ...

So how do we get to the moon without travelling to the moon at 6 milion kilometres per hour, did they keep buzz aldrin well fed on beans ... ???
kon
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

16 Feb 2014, 15:13

Is this a joke? Good question.
http://lmgtfy.com/?q=relative+speed

How can I walk to my kitchen when the earth is rotating at 1000 mph but I only walk 3 mph?
Last edited by kon on 18 Feb 2014, 17:26, edited 1 time in total.
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VxE
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

16 Feb 2014, 15:57

Either it's a really bad attempt at humor, or Roonyroo has never run alongside a flying frisbee. Either way... what's the deal with the swear filter!? Can I still play [foul/derogatory language][foul/derogatory language]in's Creed 4?
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tidbit
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

16 Feb 2014, 17:12

Roony:
When you're sitting in a car that is traveling 60 MPH you are actually moving even though you're sitting down. So although you're not moving (such as walking/running) but the car is, you're ON the car (in it, on the seat/floor). Its speed is transfered to you. So infact you are also moving 60 MPH.
If you were to drop a ball out the window, the ball is not being affected by the car so it would very rapidly slow down and it would then be behind you.

Now apply that on a galactic scale. The universe affects the galaxy, the galaxy affects the sun, the sun affects earth, earth affects the car, the car affects you. You are now moving at the speed of: universe+galaxy+sun+earth+car+you, basically.
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jethrow
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

16 Feb 2014, 17:35

... and don't forget to figure in Time dilation. Once you fully understand that, the initial question becomes trivial ;)
Guest10
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

16 Feb 2014, 23:55

how does higgs field figure into this? :lol:
wie funktioniert Higgs Feld abbildung in diesem? :ugeek:
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tidbit
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

17 Feb 2014, 10:08

sweet gif.
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LinearSpoon
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

17 Feb 2014, 10:42

Orbital physics 101 (Disclaimer: There may be some inaccuracies)

The hardest part of going to the moon is actually getting off Earth and into orbit. By far the majority of your fuel will be spent here (think of spacecraft dropping empty fuel tanks shortly after takeoff). At this point, air resistance and gravity both are working against the ship to keep it down.

Once you have lifted to a certain point you can begin turning the ship and burning closer to horizontal (relative to the surface of the Earth). Even in orbit gravity from the Earth will still affect you, pulling your towards the planet. The reason burning parallel to the surface of the planet puts you into orbit is that if you build up enough horizontal velocity, instead of falling into the planet, you will miss the planet and begin falling in a circle. By this point, air resistance is no longer a factor and gravity is actually helping you. This maneuver is called a gravity turn.

Here, the green arrow is gravity's affect on your ship, S. The red arrow is your horizontal velocity. The final travel path will look something like the purple arrow considering both inputs.
Image

Once in orbit, you have some time to think and plan (though this is actually done well before launch...). You are not spending much if any fuel to keep yourself flying around Earth in orbit. From here, it's a matter of waiting until the right time to perform another burn. Generally it's most fuel efficient to perform the burn at your periapsis, which is your closest point in your orbit to the planet and the point where you are already going the fastest. Burning prograde (in the direction that you're already travelling) at this point will extend your apoapsis, which is the furthest point in your orbit from the planet.

Here, you need to burn in the direction of the red arrow to extend your apoapsis towards the Moon. Remember gravity is still working on your ship, which is why your travel path still curves around the planet.
Image

At some point, your apoapsis will extend into the Moon's sphere of influence, which is the area where the Moon's pull on you due to gravity is stronger than the Earth's pull. Now, one of three things might happen. Your velocity might be enough to shoot you completely past the moon and into the Sun's sphere of influence. The Moon might have enough influence on you to swing you back around into Earth's sphere of influence. Or you could have a bad day and smack into the moon completely. That is, if you do nothing. To actually land on the Moon or establish orbit with it, you just need to burn retrograde (the opposite direction from the direction you're travelling) to kill off some of your velocity and let yourself get pulled into orbit.

The process to make it back to Earth is similar in reverse, but escaping the Moon takes much less fuel as it has no atmosphere and much weaker gravity, added to the fact that the ship will have less mass having spent most of its fuel reaching the Moon.

Again, I am no rocket scientist. This explanation is completely based off of my own understanding of it. Kon is correct though, all speed measurements are relative. For example, speed on Earth is usually relative to the surface of the Earth. The speed of the Moon relative to Earth is nowhere near 6m KPH. Hopefully my explanation shows that speed itself isn't as important as timing. If you launch at the wrong date, or burn at the wrong time, you can easily miss the Moon entirely...
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tidbit
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

17 Feb 2014, 10:57

Do you play Kerbal Space Program? :P Rocket Science for beginners, in the form of awesome, fun and frustration.
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LinearSpoon
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

17 Feb 2014, 11:24

I played it for a time, but I haven't done much more than land on the Mun and Minmus. In fact, that's where most of my understanding of this comes from...
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xZomBie
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

18 Feb 2014, 01:56

Jebediah Kerman always comes back even after he crashed in Kerbin. :D
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tidbit
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

18 Feb 2014, 10:19

So just how many rockets have we made, which travel at 6 million kilometres per hour, & who gets to clean up 6 million kph pile ups in space ...
Other info:
Our average shuttle/rocket and ISS travels at about 27,500kmh. Satellites can vary.
Space debris is a MASSIVE problem. http://en.wikipedia.org/wiki/Space_debris. Basically millions of things traveling faster than bullets, the size of a bullet to a minivan. There is even a pretty sweet anime about it. They are space janitors. Planetes: http://www.animenewsnetwork.com/encyclo ... hp?id=2654

Another realistic (well, Planetes is less realistic, but it's not mechas, robots, star-trek like stuff) space anime that is pure awesome:
Space Brothers (warning, you'll LOL and facepalm a lot): http://www.animenewsnetwork.com/encyclo ... p?id=13890
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Zelio
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

18 Feb 2014, 13:16

@tidbit: offtopic, but if you like "Planetes" and "Space Brothers" then try "Moonlight Mile", it is a bit old (2007) and more a science fiction anime for japanese adult, but maybe you will have more stars in your eyes...
http://myanimelist.net/anime/1941/Moonl ... :_Lift_Off
http://myanimelist.net/anime/2929/Moonl ... Touch_Down
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tidbit
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

18 Feb 2014, 13:30

Seen that :P was kinda cheesy and the nudity/sex scenes didn't help too much (I prefer story. not hotties and violence. It doesn't hurt, though. If kept under control). But not too bad either.
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Roonyroo
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

19 Feb 2014, 12:28

Thanks for replying guys , lol

The problem is the moon isnt strictly rotating around the earth ... the moon is travelling at a fixed speed of 6million kmh, so as soon as the shuttle travelling at 27,000 kmh leaves the earth, the moon because its travelling at 6million kmh should fly past the shuttle making it impossible for the shuttle to reach the moon

Also you guys seem to be making an assumption that the moon is stuck in the gravitation field of the earth, when in fact the moon moves relative to the rotation of the solar system

Basically if the earth wasnt there, the moon would still travel in the exact same position at 6 million kmh

So if there's no gravitation field or centrifuge to hold the moon in place, how is a shuttle travelling at 27k kmh reaching an object travelling at 6million kmh ...



Check out

http://www.universetoday.com/60174/does-the-sun-move/

"We mainly talk about everything in the solar system orbiting the Sun and celestial objects outside the solar system being in relation to the Sun.

The answer to the question is : Yes. The Sun and the entire solar system orbits around the center of the Milky Way galaxy. The average velocity of the solar system is 828,000 km/hr. At that rate it will take about 230 million years to make one complete orbit around the galaxy."


So how is a rocket reaching the moon when it leaves the rotation of the earth ... travelling at only a crappy speed of 27k kmh, when the entire solar system is travelling at over 800,000 kmh ...

Magic gravity fields, centrifuges etc?
Last edited by Roonyroo on 19 Feb 2014, 12:44, edited 1 time in total.
kon
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

19 Feb 2014, 13:11

lol. I think you are trolling, but on the off chance you aren't... Everything you said is wrong or misinterpreted. You are missing a critical point about speed. In order to measure something's speed, you have to measure it in relation to something else.
Roonyroo wrote:The problem is the moon isnt strictly rotating around the earth
You're seriously saying the Moon doesn't orbit the Earth?
Roonyroo wrote:... the moon is travelling at a fixed speed of 6million kmh,
Speed relative to what?
Roonyroo wrote:so as soon as the shuttle travelling at 27,000 kmh leaves the earth, the moon because its travelling at 6million kmh should fly past the shuttle making it impossible for the shuttle to reach the moon
It's not like dropping a tennis ball out of a moving car. The Earth and the Moon are moving at close to the same speed around the Sun. Once a Saturn rocket leaves earth, it is moving at the speed of Earth plus its escape velocity.
Roonyroo wrote:Also you guys seem to be making an assumption that the moon is stuck in the gravitation field of the earth, when in fact the moon moves relative to the rotation of the solar system
The moon orbits the earth at 1.022 km/s (Speed relative to the Earth). The Earth orbits the Sun at 29.78 km/s (107200 km/h) (Speed relative to the Sun). The Sun orbits the galactic center at 220 km/s ( 792000 kph) (Speed relative to the galactic center). The Milky Way moves at approximately 552 ± 6 km/s relative to CMB rest frame.
Roonyroo wrote:Basically if the earth wasnt there, the moon would still travel in the exact same position at 6 million kmh
Wrong.
Roonyroo wrote:So if there's no gravitation field or centrifuge to hold the moon in place, how is a shuttle travelling at 27k kmh reaching an object travelling at 6million kmh ...Magic gravity fields, centrifuges etc...
You keep using those words... I don't think they mean what you think they mean.
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LinearSpoon
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Re: How Can Rockets Travel To The Moon, If MoonTravels at 6m

20 Feb 2014, 12:53

You seem to be making a lot of assumptions about space travel:
1. That the moon and the rocket speeds are measured relative to the same source.
2. That a rocket leaving the Earth will not "inherit" the Earth's velocity.
3. That getting to the moon is just a matter of "chasing it" until you catch up to it.
4. That the Earth's gravity does not keep the moon in orbit around Earth. Or maybe you were implying gravity doesn't exist.

I am tempted to regard this as a troll thread...

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