Are there any Cons in using rotational speed of Earth for Rockets?

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I have 2 advantages of using rotational and orbital velocity of Earth in assisting easier rocket travel...

1. Uses less fuel as the rotational speed contributes to the rocket
2. Assists the rocket to easily produce the necessary escape velocity


Are there anymore adv??? I can't seem to notice any disadvantages...

are there any ?
 

Answers and Replies

  • #2
tiny-tim
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slows down the rotation of the Earth very slightly! :biggrin:

"there's no such thing as a free launch!" :wink:
 
  • #3
Drakkith
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You can only launch something in the direction that the earth is rotating. If you don't want to go that way, then you can use the rotational speed of the earth.

Also, if you want to go the opposite way, you must expend more fuel to do it.
 
  • #4
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You can't launch from the north or south pole.
 
  • #5
K^2
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Retrograde orbits are the only problem, really. If you want to get orbits with higher inclination, you can always launch from further north or south from equator.
 
  • #6
arildno
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Physics isn't politics.

In the sense that choices politicians have (pros and cons about, say, public healthcare) do no exist for physicists.

You must, necessarily, take into account the rotation of the Earth if you are to make asuccessful launch.
Thus, "pro/con"-thinking is largely irrelevant, doable/undoable is, for example, a more relevant concern.

Politics enter when deliberating whether to fund or not a space launching project that is optimized for its purpose, and that optimization will have, as one of its necessary parameters, how to deal with the rotation of the Earth.
 
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  • #7
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I have 2 advantages of using rotational and orbital velocity of Earth in assisting easier rocket travel...

1. Uses less fuel as the rotational speed contributes to the rocket
2. Assists the rocket to easily produce the necessary escape velocity


Are there anymore adv??? I can't seem to notice any disadvantages...

are there any ?
Are these really two different issues? Assuming that the launch does not fail, the rocket will reach its required velocity (for satellites it's not the escape velocity but less).
This is realized with more or less fuel, depending on the direction of the launch.
 
  • #8
Drakkith
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You can't launch from the north or south pole.
Any particular reason why you can't? Other than the expense of building launch facilities and transporting the launch vehicle there.
 
  • #9
D H
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Any particular reason why you can't? Other than the expense of building launch facilities and transporting the launch vehicle there.
That expense alone does the concept in. A launch site at the South Pole would almost certainly violate the Madrid Protocol to the Antarctic Treaty. A launch site at the North Pole? There is no land there, just a bunch of floating pack ice. That pack ice does not stay put. The floes move around, crash into one another, etc. Nothing is permanent.
 
  • #10
A launch site at the North Pole? There is no land there, just a bunch of floating pack ice.
A sea-launch type effort might be possible soon. You can already get pretty close to the north pole in summer.

Of course why you would want to is another question
 
  • #11
BobG
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The North Pole or South Pole would have another major limitation. The only inclination you could launch into would be a 90 degree inclination. The launch site essentially has to lie in the orbit plane of your launch.

The orbital speed of the Earth won't come into play for a satellite orbiting the Earth - only the rotational speed. And the pro is a major pro. If the satellite is going into a high altitude orbit, one that uses an upper stage booster, the satellite will be launched almost due East into a parking orbit even if it's final inclination is higher, such as a GPS satellite with a 55 degree inclination. You want to change the inclination as far away from the Earth as possible when your Delta V's are small (keeping in mind that a launch is a huge Delta V).

Naturally, if it's a low orbiting satellite that's going to be launched directly into its final orbit, then you have to just suck up the fuel costs. But, Kodiak Launch Complex is a good launch site for retrograde polar orbiters, molniya orbits, and tundra orbits just because it is so far North (about 57 degrees latitude). None the less, it hasn't attracted enough commercial customers to make it self sustaining.
 
  • #12
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Any particular reason why you can't? Other than the expense of building launch facilities and transporting the launch vehicle there.
I'm sure you COULD launch from the north or south pole, but not if you want to use the rotational speed of the earth to launch a rocket.

And hence, as an answer to the OPs question, this can be considered a con. Perhaps the most obvious one.
 
  • #13
Drakkith
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That expense alone does the concept in. A launch site at the South Pole would almost certainly violate the Madrid Protocol to the Antarctic Treaty. A launch site at the North Pole? There is no land there, just a bunch of floating pack ice. That pack ice does not stay put. The floes move around, crash into one another, etc. Nothing is permanent.
Of course, I was simply wondering if the reason was due to something like what you mentioned, or because of some reason in physics.
 
  • #14
sophiecentaur
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This is not really a 'Physics' question. It's an Engineering matter and, consequently, MONEY comes into it. The orbital speed in low orbit will be about fifteen times the speed of the Earth's surface so the differences are not enormous for launches in any direction - just important economically.
You can launch in any direction and put a payload into orbit. But the cheapest launch per kg of payload (or the max payload for a given amount of fuel) will be from the Equator and in the direction of Earth rotation. Hence, only when the orbit direction is very important, will the launch be non-standard.
 

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