Micro Gravity and A Space Elevator?

I haven't done any research in this area. Does anyone know of any
studies of micro-gravity inside the cab of a space elevator?

Remember to work, the entire system has to be under elastic tension. The
designs I've seen discussed use a big counter-mass at the far space end
of the cable to hold the system in place above the anchorpoint on
Earth's equator.

The trivial case is when the cab is down on the Earth side. Obviously
we're at 1G on the surface. I've presumed as the cab rises the effect of
Earth's gravity goes down as inverse square (Universal Gravitation):

https://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation

Are objects inside the cab of the space elevator near the "space" end
undergoing any form of microgravity? The system really isn't in free
fall because of the counter-mass suspended above it and the cable
running below. Does the tensive forces provide any form of microgravity
inside the cabin or are the occupants fully in 'free fall'? That doesn't
seem quite correct either. Only if the cabin were in orbit without any
connective cable. The counter-mass *is* appling force to the system to
hold it stable. Maybe the effect of any 'artificial gravity' are too
small to be consequential? If you were to suspend a cabin above the
counter-mass would you end up with an artificial gravity in the vector
direction of 180 degrees opposite the Earth's surface? i.e. the 'floor'
of the cabin becomes the surface of the cabin opposite the Earth,
alongside empty space?

I haven't studied this question at all. Any cites to any studies on this
appreciated.

Dave

On 2020-06-10 15:27, David Spain wrote:
I haven't done any research in this area. Does anyone know of any
studies of micro-gravity inside the cab of a space elevator?

Remember to work, the entire system has to be under elastic tension. The
designs I've seen discussed use a big counter-mass at the far space end
of the cable to hold the system in place above the anchorpoint on
Earth's equator.

The trivial case is when the cab is down on the Earth side. Obviously
we're at 1G on the surface. I've presumed as the cab rises the effect of
Earth's gravity goes down as inverse square (Universal Gravitation):

Yes, but you also have to take into account that as the cab rises, it
gains "orbital" velocity, which counteracts the gravity. The effect of
the "orbital" velocity increases until it exactly balances gravity when
the cab reaches the geosynchronous altitude.

Are objects inside the cab of the space elevator near the "space" end
undergoing any form of microgravity?

Yes, see above.

The system really isn't in free fall because of the counter-mass
suspended above it and the cable running below.
Irrelevant. The entire elevator is rotating at the geosynchronous
period. Below the geosynchronous point, this rotation is slower than
free-fall orbital velocity, so the cab will feel a residual
gravitational attraction towards Earth. Above the geosynchronous point,
this rotation is faster than free-fall orbital velocity, so the cab will
feel a "centrifugal" force out from Earth.

Does the tensive forces provide any form of microgravity
inside the cabin or are the occupants fully in 'free fall'?

Below the geosynchronous altitude, the elevator is holding the car up,
so there is an attraction towards the Earth and the floor of the cab.

Free fall comes when the cab is at the geosynchronous altitude.

If you were to suspend a cabin above the
counter-mass would you end up with an artificial gravity in the vector
direction of 180 degrees opposite the Earth's surface? i.e. the 'floor'
of the cabin becomes the surface of the cabin opposite the Earth,
alongside empty space?

Yes.

This discussion assumes that the cab is moving slowly along the
elevator. If the cab is moving fast, there are sideways forces and
accelerations that tilt the apparent gravity in the cab.

--
Niklas Holsti

niklas holsti tidorum fi
. @ .

On 2020-06-10 8:40 AM, Niklas Holsti wrote:
Yes, but you also have to take into account that as the cab rises, it
gains "orbital" velocity, which counteracts the gravity. The effect of
the "orbital" velocity increases until it exactly balances gravity when
the cab reaches the geosynchronous altitude.

Are objects inside the cab of the space elevator near the "space" end
undergoing any form of microgravity?

Yes, see above.


OK that makes sense and is totally interesting.

Is this an interesting way to get artificial gravity on a space station
'on the cheap' without rotation? Without taking orbital velocity into
effect by assuming we are stationary above the Earth surface thanks to
our cable and just use the acceleration of gravity calculator he

https://www.calctown.com/calculators...ty-calculation

I get a figure of 8.8836 m/s**2 for the acceleration of gravity at 200
miles up (322 km) (essentially LEO). Or roughly 8.8836/9.8 or .9g. How
accurate is that figure?

Dave

On 2020-06-10 16:43, David Spain wrote:
On 2020-06-10 8:40 AM, Niklas Holsti wrote:
Yes, but you also have to take into account that as the cab rises, it
gains "orbital" velocity, which counteracts the gravity. The effect of
the "orbital" velocity increases until it exactly balances gravity
when the cab reaches the geosynchronous altitude.

Are objects inside the cab of the space elevator near the "space" end
undergoing any form of microgravity?

Yes, see above.


OK that makes sense and is totally interesting.

Is this an interesting way to get artificial gravity on a space station
'on the cheap' without rotation?

It is certainly a way to get any desired apparent gravity from one-gee
to zero-gee, without a centrifuge. Building "stations" at various
altitudes along the elevator of course increases the stress on the
elevator cable a little.

But I wouldn't call a space elevator "cheap" :-)

--
Niklas Holsti

niklas holsti tidorum fi
. @ .

On 2020-06-10 1:06 PM, Niklas Holsti wrote:

But I wouldn't call a space elevator "cheap" :-)


Good point. Plus it relies on unobtainium for the cable. I've heard
carbon nano-tubes *might* be strong enough. But haven't seen them laid
out in 36,000 km long "cables" either.

Dave

On Wednesday, June 10, 2020 at 2:01:52 PM UTC-4, David Spain wrote:
On 2020-06-10 1:06 PM, Niklas Holsti wrote:

But I wouldn't call a space elevator "cheap" :-)

Good point. Plus it relies on unobtainium for the cable. I've heard
carbon nano-tubes *might* be strong enough. But haven't seen them laid
out in 36,000 km long "cables" either.

Nothing even remotely approaching obtainium is on the horizon for a space
elevator for Earth.

It would be possible for the Moon today, given its much lower gravity. Given
its very slow rotation, a geosynchronous anchor would not work, but they could
use one of the Moon's LaGrange points.

On 2020-06-10 2:01 PM, David Spain wrote:
On 2020-06-10 1:06 PM, Niklas Holsti wrote:

But I wouldn't call a space elevator "cheap" :-)


Good point. Plus it relies on unobtainium for the cable. I've heard
carbon nano-tubes *might* be strong enough. But haven't seen them laid
out in 36,000 km long "cables" either.

Dave


https://figshare.com/articles/Growth...bution/2393992

Just need to scale this process up by a factor of 72E6 meters in length.
No quite so much in diameter.... :-)

Dave

On 2020-06-10 2:16 PM, Scott Kozel wrote:

It would be possible for the Moon today, given its much lower gravity. Given
its very slow rotation, a geosynchronous anchor would not work, but they could
use one of the Moon's LaGrange points.


You're thinking a fuel depot? Water pumped up from the surface to the
anchored depot at L1 or L2? Micro-gravity available when docked?

Dave

In article , says...

I haven't done any research in this area. Does anyone know of any
studies of micro-gravity inside the cab of a space elevator?

Remember to work, the entire system has to be under elastic tension. The
designs I've seen discussed use a big counter-mass at the far space end
of the cable to hold the system in place above the anchorpoint on
Earth's equator.

The trivial case is when the cab is down on the Earth side. Obviously
we're at 1G on the surface. I've presumed as the cab rises the effect of
Earth's gravity goes down as inverse square (Universal Gravitation):

https://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation

Are objects inside the cab of the space elevator near the "space" end
undergoing any form of microgravity? The system really isn't in free
fall because of the counter-mass suspended above it and the cable
running below. Does the tensive forces provide any form of microgravity
inside the cabin or are the occupants fully in 'free fall'? That doesn't
seem quite correct either. Only if the cabin were in orbit without any
connective cable. The counter-mass *is* appling force to the system to
hold it stable. Maybe the effect of any 'artificial gravity' are too
small to be consequential? If you were to suspend a cabin above the
counter-mass would you end up with an artificial gravity in the vector
direction of 180 degrees opposite the Earth's surface? i.e. the 'floor'
of the cabin becomes the surface of the cabin opposite the Earth,
alongside empty space?

I haven't studied this question at all. Any cites to any studies on this
appreciated.

See "Apparent gravitational field" he

https://en.wikipedia.org/wiki/Space_elevator

A rough approximation is that there is one point on the length of the
space elevator where the cabin crawling up the elevator is in "free
fall". This altitude is the geostationary orbital altitude. Anything
below that, and the earth's gravity is greater than centripetal force.
Anything above that, and the centripetal force is greater the earth's
gravity (so "down" is away from the earth!).

This also has a huge impact on what happens to any mass released from
the elevator. From the Wikipedia entry:

Any object released from the cable below that level would initially
accelerate downward along the cable. Then gradually it would
deflect eastward from the cable. On the cable above the level of
stationary orbit, upward centrifugal force would be greater than
downward gravity, so the apparent gravity would pull objects
attached to the cable upward. Any object released from the cable
above the geosynchronous level would initially accelerate upward
along the cable. Then gradually it would deflect westward from
the cable.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

On Wednesday, June 10, 2020 at 2:28:39 PM UTC-4, David Spain wrote:
On 2020-06-10 2:16 PM, Scott Kozel wrote:

It would be possible for the Moon today, given its much lower gravity. Given
its very slow rotation, a geosynchronous anchor would not work, but they could
use one of the Moon's LaGrange points.

You're thinking a fuel depot? Water pumped up from the surface to the
anchored depot at L1 or L2? Micro-gravity available when docked?

I wasn't advocating or opposing a Moon space elevator, just saying that it is
technologically feasible with today's materials.

I read somewhere that a Mars space elevator is technologically feasible with
today's materials, but I am not sure about that.