Trans Planetary Elevator?

[daniel l.]

In a situation of mutual tidal locking where to planets are absolutely locked to each other, How easy would it be to build a space elevator between them that takes people from the surface of one to the other, A good place to do this would be the Pluto system.

[Speeding Mullet]

In theory possible, but the practicalities are made difficult (not considering the difficulty of making a SE in the first place) by orbital eccentricity and inclination.  All known orbits are elliptical so you need to design a way for the SE to compress between the difference in the semi-major axis and the semi-minor axis of your co-orbital ellipse as well as taking into account libration etc.

This thread has some good info, and discusses the Pluto Charon relationship with respect to Space Elevators.

SM

Edit: Nice location btw, its a favorite through my astro bins

 

Edited July 31, 2016 by Speeding Mullet

[Nibb31]

9 hours ago, daniel l. said:

In a situation of mutual tidal locking where to planets are absolutely locked to each other,

You would also need both objects to orbit with zero inclination and zero eccentricity. What is the probability of such an orbit occurring ?

 

[Tex_NL]

In theory it should be possible, in practice absolutely not.
We simply do not have the technology. And ANY advanced society that does have the required tech to build such a contraption will also have the tech to transfer crew/energy/cargo between the two faster, easier, safer and cheaper.

Edited July 31, 2016 by Tex_NL

[wumpus]

I'd suspect that current tech can handle building a "rope" that can handle's Pluto's gravity, but I have no idea what Pluto's lack of temperature would do to it.  I also suspect that any definition of "requirements to build a space elevator" haven't looked to closely to the dynamic effects of a device attempting to "climb" the elevator: since we're still at "stage one: support its own weight" the available calculations aren't likely to include this.

But using "Pluto+Charon" shouldn't been the same as "Earth + the Moon moved to GSO".

[PB666]

Not planets tidally locked planetoids might be possible. That space elevator is a far future/never technology. 

[UmbralRaptor]

If you assume a space elevator, one can go up beyond the normal synchronous altitude and just let go to be launched elsewhere. Mid-course corrections and landing are not included.

[HopDavid]

On July 30, 2016 at 6:28 PM, Speeding Mullet said:

In theory possible, but the practicalities are made difficult (not considering the difficulty of making a SE in the first place) by orbital eccentricity and inclination.  All known orbits are elliptical so you need to design a way for the SE to compress between the difference in the semi-major axis and the semi-minor axis of your co-orbital ellipse as well as taking into account libration etc.

This thread has some good info, and discusses the Pluto Charon relationship with respect to Space Elevators.

SM

Edit: Nice location btw, its a favorite through my astro bins

 

Incorrect.

Eccentricity of Charon's orbit about Pluto is very, very close to zero. I believe the obliquity is also very close to zero.

On July 31, 2016 at 3:09 AM, Nibb31 said:

You would also need both objects to orbit with zero inclination and zero eccentricity. What is the probability of such an orbit occurring ?

 

Quite high. That describes Pluto and Charon. The zero eccentricity is an outcome of eons of tidal evolution. See The Orbit of Charon is Circuler by Buie et al.

[HopDavid]

On July 31, 2016 at 1:51 PM, UmbralRaptor said:

If you assume a space elevator, one can go up beyond the normal synchronous altitude and just let go to be launched elsewhere. Mid-course corrections and landing are not included.

This is a good observation. Many wrongly believe an elevator's only purpose is getting off the ground. But the elevator can also impart velocity.

Speed of a payload on an elevator is ωr where ω is angular velocity in radians and r is distance from body center. The farther you are from center, the bigger r is. So an elevator from Ceres, Vesta or Phobos can provide delta V for insertion to a transfer orbit to another destination in the solar system.

However in an elevator between Charon and Pluto, synchronous orbits would be at Pluto, Pluto Charon L1 and Charon. Releasing from points other than these will drop you towards either Pluto or Charon.

To luanch into a heliocentric transfer orbit you'd need an elevator from Charon's far point through Pluto Charon L2. Or an elevator from Pluto's far point through Pluto Charon L3.

[lugge]

A rope on pluto has to pull far less weight than a rope for an earth-based elevator.

Thus, I would assume we currently have the materials to construct such a rope. However, on pluto, you can achieve orbit for far less dv, thus, a space elevator makes less sense on such small bodys.

This is just theory. In practise, a pluto-charon elevator is in a even more distant future than a earth-based one, and even such can be seen as sci-fy.

[HopDavid]

14 hours ago, lugge said:

However, on pluto, you can achieve orbit for far less dv, thus, a space elevator makes less sense on such small bodys.

As I just said upthread, getting off a body isn't the only thing an elevator would be used for.