Mechanical energy transmission cables

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This article is speculative. It covers topics that are not straightforwardly derivable from current knowledge. Take it with a grain of salt. See: "exploratory engineering" for what can be predicted and what not.

Up: Energy transmission

[Todo: make and add doublelog energy transport density graph - (chemical + mechanical + inertial) compound]

Due to the very high energy densities that are handleable with diamondoid nanosystems [reference needed] and the available superlubrication energy could potentially transmitted mechanically.

Depending on the magnitude of superlubrication and effectiveness of infinitesimal bearings the feasible transmission length-scale will be determinable.
[Todo: estimations / general estimation formula]. This length scale probably can be expected to be quite large.

Energy could be transmitted via translative or rotative or combined movement of diamondoid rods. For translative movement any diamondoid rods can be employed. For rotative movement strained shell diamondoid rods or nanotubes are suited best. For continuous pulling flexible belts ropes or chains can be considered.

Power is force times speed (corresponding to voltage times current).

  • The force is limited by the tensile strength of the used rods.
  • The speed is limited by the turn radius and thus indirectly by the tensile strength of the housing structure.

When speed is increased speed dependent friction rises quadratically. This can be limited by the use of infinitesimal bearings as concentrical cylindrical shells along the whole length of the cable. Bearing thickness reduces the relative speeds linearly. With rising speeds centrifugal forces become exceedingly high making beefy supporting structures necessary. Power densities beyond the already very high limit for diamondoid systems are then accessible and cable damage becomes a very serious hazard. For lower power densities and lower speeds sharp bends are still problematic because of the limited flexibility (bendability) of such cables. Specially designed turning elements may be usable.

For medium long to very long distances one can meet the limit of specific strength that is the rods can't turn/pull their own inertial weight anymore. This limits the power-up rate (unit: watts per second). energy storage cells [Kickstart with interfacial drives to circumvent this ?] The energy transfer speed (propagation of the rising flank after power-up) is equal to the (very high) transversal or longitudinal speed of sound of the choosen diamondoid material but still significantly slower than electrical impulse propagation. The maximum speed of continuous axial movement is not limited by the speed of sound though. For all practical purpouses this limit is so high that it wont matter much. Continuous rotative, alternating rotative and reciprocative movement might have benefits for all but power densities so high that they require global scale bending radii (cables carrying speeds exceeding csound in diamond).

Example: Limit for areal power density:
50GPa ... ~ tensile strength of natural diamond - mechanosynthetisized one will be stronger
csound ... the longitudinal speed of sound in diamond

  • 1000th csound: 50GPa * 18m/s = 900GW/m2 = 9GW/dm2 = 90MW/cm2 = 900kW/mm2
  • 100th csound: 50GPa * 180m/s = 9TW/m2 = 90GW/dm2 = 900MW/cm2 = 9MW/mm2 (seems practical)
  • 10th csound: 50GPa * 1.8km/s = 90TW/m2 = 900GW/dm2 = 9GW/cm2 = 90MW/mm2

Note that if the cable (for whatever reason) is free standing and goes around in a cricle there is a scale invariand speed limit of about 3km/s above which a nanotube ring ruptures due to centrifugal force. This also poses a limit to areal power density in small scales of at least 15MW/mm2. soem form of nanoscale levitation method may be needed to reach such powerdensity levels.

[Todo: Compare to expensive overhead power line ~ 1MW/mm2] [note the involved high kinetic energies]

To minimize acoustic losses in the environment a (high) number of litzes/strands operated in different phases can be combined. Elastic losses translate to capacitive losses in electrical lines. Rotation has higher stiffness but also higher speed dependent power dissipation [to verify]. Translation has lower stiffness and lower speed dependent power dissipation [to verify].

Note: Inertal energy is bound in non-sinusodial steady state operation and surfaces at shutdown.

[Todo: Discuss insertion and extraction of mechanical power]
[Todo: There seems to be a discrepancy to the power densities noted in Nanosystems. Note that they are related to volume not area like here.]

Transporting chemical energy

The idea is to pack some energy storage cells on the energy transport track. Its probably very useful for low speed systems - including almost all the stuff of everyday use. For high sppeed systems at some point the kinetic energy will outgrow the chemical energy since it grows quaddratically instead of linear with speed. Also chemomechanical converters are slower than mechanomechanical transmissions and may loose efficiency when operated to fast.

Mechanical energy transmission cables vs electrical superconductors

It's still unclear whether superconductors will some day meet widespread use. It doesn't seem too unlikely though.

  • With advanced thermal isolation even today's superconductors may be usable. These YBCO superconductors contain not the most abundant but also not exceedingly rare elements.
  • The discovery of a practically usable room temperature superconductors is (as of 2017 to the knowledge of the author) still an unpredictable scientific discovery. Superconducting topological insulators may be a promising field.
  • With advanced mechanosynthesis a giant space of strongly metastable non-equilibrium structures becomes accessible that is not accessible via conventional thermodynamic production methods (mixing,melting,annealing,...). The neo polymorphs. This allows for much more powerful random and systematic search.

Measuring the remnant resistance of superconductors has (to the knowledge of the author) never been archived (physics usually does not like true infinities / true zeros). So the energy transmission efficiency should be even higher than the one of mechanical energy transmission cables.

The downsides of superconducting energy transport in comparison are:

  • involvement of not so extremely abundant elements
  • susceptibility to electromagnetic interference (solar storms / EMPs)
  • associated strong magnetic stray fields
  • achievable efficiencies for mechanical energy transmission cables should be near 100% anyway.

On a highly speculative note:
Has anyone thought about bearing things by floation them on superfluids?

Alternate uses

Warning! you are moving into more speculative areas.

Beside energy transport continuous linear movement cables could be used for the forces they develop. When curvature and speed produces forces exceeding gravitational acceleration (note that there is no need for escape velocity) the cable could (very speculatively) lift by itself and build a launch loop. When such a cable is cut a big scale explosion may follow depositing lots of material at the explosion site.

A better approach may be J. Storr Halls static Space Pier.
If you want some discussion of the widely known space elevator concept in light of advanced APM capabilities go here.