# Space Elevator

#### Atlan0001

Nice idea, but....

.... It would be better if a way was found to construct an elevator based on force, or even light, something / anything non-matter, between the surface of the Earth and geosynchronous orbit some 22,000 miles up. There is too much now, and always has been, including non-material, between here and there that would continuously damage and even destroy an elevator made of matter.

#### LKK

I guess there's the design to use the momentum of launched projectiles to hold things up, closer to recognizable tech than anything none structural that I can think of

Atlan0001

#### Questioner

My thought/question with a space elevator is if the mass in orbit changes doesn't that require a change in orbital speed or radius from Earth?

One might need a constant exchange with counter weights (masses) otherwise i would think it would require fuel to change the orbital speed or 'elevation' (radius).

Not a physics guy, but that would be my concern with a space elevator.

#### LKK

Except for drag effects a feather and a moon orbit at same velocity at given distance

#### Questioner

Nonphysicist, out of my element,
but
thought experiment
if one increased the mass of the Earth without changing the radius from the Sun or speed of orbit i am pretty sure the Earth would spiral outward or fly into deep space because of increased inertia.
Counter intuitively if the mass decreased the Earth would move in toward the Sun because of reduced inertia.
It's the feather and hammer falling at the same speed in vacuum.

My additional question is (even using counter weights/masses) what goes on as masses are halfway (fractions) up & down the ribbon/cable between orbit and terraferma?

If i were a serious invester in the project i would want detailed physics modeling for all the dynamic states to make sure it works.

#### Questioner

Lastly is weather on the low end of the ribbon/cable.
Lightening strikes wind and moisture would have to be considered.
Not sure how or if that could be dealt with.

#### Questioner

Maybe for low altitude weather the bottom of the ribbon cable could be hoisted up out of it?

#### LKK

Nonphysicist, out of my element,
but
thought experiment
if one increased the mass of the Earth without changing the radius from the Sun or speed of orbit i am pretty sure the Earth would spiral outward or fly into deep space because of increased inertia.
Counter intuitively if the mass decreased the Earth would move in toward the Sun because of reduced inertia.
It's the feather and hammer falling at the same speed in vacuum.

My additional question is (even using counter weights/masses) what goes on as masses are halfway (fractions) up & down the ribbon/cable between orbit and terraferma?

If i were a serious invester in the project i would want detailed physics modeling for all the dynamic states to make sure it works.
You're talking about inertia now entirely different subject , You would indeed have to balance inertia during operations, my understanding though is that the energy gain of raised objects would come from the enormous inertia of the Earth.

#### Questioner

With an orbiting object if either the mass or speed is increased the radius to the gravitational body must be decreased to sustain an approximately circular orbit.
If one increases the orbiting body's mass one must reduce the speed.
If one increases the speed of an orbiting body one must reduce the mass.
I believe that is all correct.

With a space elevator the speed and radius must remain constant to keep the ribbon/cable in place.
So one must use exchange of counter weights/mass to keep the mass constant.
That also might reduce the energy expenditure hauling stuff up.

I am still uncertain of the physics of partial positioned masses as well as additional stresses on the ribbon/cable. I wonder if there might be some lateral stresses/pulls with partially lifted masses, perhaps pulling on the orbiting body as well.

#### LKK

That is simply untrue, as the space station was built with more and more mass the orbit was affected by drag etc. but not by the greatly increased mass

#### Questioner

Even using counter weights doesn't really mitigate the energy demands easily.

Lifting something from the face of the Earth is probably essentially like shooting a rocket into space.
The initiation energy is tremendous (greatest).

That is a vector that pulls perpendicular to the orbiting object's inertia. It is a drag on its radius.

Lowering a counter mass has the inverse energy return. At the top of drop it delivers very little energy. Increasing to greatest energy at the bottom, closest to the surface of the Earth.

So a simple pulley & counter weight/mass wouldn't work to offset energy/lift.
I think that would double the downward pull on the orbiting object as well.

I think regardless of where the energy is spent,
either keeping the orbiting body in position as the target mass is lifted, it still takes the same total energy as launching a rocket from the surface of the Earth.
The fuel to keep the orbiting body in position must itself already be pre-lifted into orbit.

Honestly I don't think it really works to any advantage.

It is a 'slight of hand' of the imagination.

#### LKK

The thing is the energy to raise something to orbital hight is a tiny fraction of what a rocket spends to get something into orbit. It would be a small fraction even if all the total inertia came from electricity. In this case however only raising it is necessary, the necessary added inertia is robbed from enormous well of that from the spinning Earth.

#### Questioner

It is deceptive/seductive to imagine massive orbiting bodies are immovable,
but it is incorrect.

When gravity assist is used to accelerate spacecraft it slows the speed of the orbiting body a proportionally tiny amount.

The same thing applies to an asteroid orbiting the Earth,
except in that case the proportion is not as miniscule.
The total lifting energy is extracted from the orbiting body's orbit.
Eventually the energy deficit comes due,
with the asteroid spiraling &/or crashing into the Earth.

It sounds wonderful, magical,
problem is the physics just don't add up.

#### Questioner

final fantasy footnote:

If one could connect a ribbon/cable all the way to the moon it becomes theoretically plausible,
because the moon is spiraling outward anyway and is super massive to boot.

#### LKK

It is deceptive/seductive to imagine massive orbiting bodies are immovable,
but it is incorrect.

When gravity assist is used to accelerate spacecraft it slows the speed of the orbiting body a proportionally tiny amount.

The same thing applies to an asteroid orbiting the Earth,
except in that case the proportion is not as miniscule.
The total lifting energy is extracted from the orbiting body's orbit.
Eventually the energy deficit comes due,
with the asteroid spiraling &/or crashing into the Earth.

It sounds wonderful, magical,
problem is the physics just don't add up.
If you studied up on beanstalks You would find that the energy is actually coming from the counterbalance at the end of the tether, which has it to spare, not only that but the moment that counterbalance begins to change velocity, it changes the angle of the tether which immediatly begins correcting the velocity

#### Questioner

One could have a surplus of inertia in the orbiting body and have the tether tension hold all that stress, but the cable/ribbon would have to be incredibly strong and how would one get the orbiting body in (orbital) place & connected to the ribbon?
I suppose a flyby with a single chance to connect the ribbon?
Even if possible it would have effects on the Earth plus asteroid's center of mass/gravity.

Not sure most people would like that.

But like i say,
the Moon is good to go with incredible potential lifting power.
1) a long enough ribbon
2) avoiding low altitude storms
3) the ribbon avoiding near Earth asteroid flybys.

Heck,
it's easy peasy.
Good as done! Lol

#### LKK

One could have a surplus of inertia in the orbiting body and have the tether tension hold all that stress, but the cable/ribbon would have to be incredibly strong and how would one get the orbiting body in (orbital) place & connected to the ribbon?
I suppose a flyby with a single chance to connect the ribbon?
Even if possible it would have effects on the Earth plus asteroid's center of mass/gravity.

Not sure most people would like that.

But like i say,
the Moon is good to go with incredible potential lifting power.
1) a long enough ribbon
2) avoiding low altitude storms
3) the ribbon avoiding near Earth asteroid flybys.

Heck,
it's easy peasy.
Good as done! Lol
LOL def some serious engineering challenges there! It's actually envisioned that they'll start from synchronis orbit and just extend the tether up and down from there

#### Questioner

But if one is going to overload/pump-up beyond the initial minimum inertia it will take tons of fuel to put the tension on the ribbon.
Doesn't happen by magic.
No free rides that way.

#### LKK

It's assumed the mass of the counterweight will be aquired in space then using gravity maneuvers to move it into place

#### LKK

Don't get me wrong I think there are a lot of extreme challenges to this idea

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