Instability of long cylinders

> Assume a box...any first year mechanical engineer knows that five (5)
> sides of a box need to be cross braced otherwise the box
> cannot handle forces from all directions.

You know, I did more than first year mechanical engineering - and I've not
sure what you're saying here. (Though there are several possibilities.)
Could you try using diagrams, or possibly even english? :)

> Yes, we could use trusses or wires or even clear
> cylinders of fabric for cross bracing, but we will still need to
> address the issues of basic box bracing.

Or you could use internal pressure. The Atlas rocket balloon tank couldn't
be removed from it's construction frame until after it has been presurised.
No additional cross bracing was needed due to that pressurisation. Cylinders
will only be presurised to one atmosphere, but they will have a lot of
outward 'faux pressure' due to the mass per area and rotation. You won't be
able to poke it inwards with your finger.

> Any long cylinder in space is going to have a number of forces acting
> on it no matter how small. However, due to the megaconstruction every
> force is amplified.

Possibly you mean 'every angular force' due to greater leaverage. Additional
mass won't make any difference to the acceleration of gravity.

> So all the gravitional sources are varying in time.

Yes, so? It'll be miles long and wide. If it moves a few hundred meters
outside of its ideal orbit, who will care, or even notice?

> Next is the solar wind and the earth magnetic field.

Solar wind will have near 0 effect. Earth's magnetic field is barely
measurable where cylinders are planned.

> That brings up an interesting point. The Tether problem. For a long
> cylinder traveling through a magnetic field (earth, sun, solar flare,
> CME, etc) there will be induced by the m-field a significant electric
> difference between the ends, and possibly a number of nodes due to
> standing waves of ions.

So we earth all the metal parts to each other, and add an electron gun to
neutralise charge relative to incoming space craft. Does the sun have a
significant magnetic field at 1AU?

> The solar wind by itself will create a differential force.

Two newtons VS twenty million tons. I'm not going to be betting on the two
newtons.

> Any comet, asteroid, CME or other mass hitting, even glancing, the
> cylinder will introduce an instability.

That's what radar is for. Diverting, or collecting debris is going to be
childishly simple for anyone who can build such cylinders.

> So, to your question. Once you shut off all the ONeill stabilizers,
> what happens...

And the answer is:

> Two counter rotating cylinders would provide some stability due to
> gyroscopic forces. However, given the list of forces above, other
> dynamic stability solutions would still be needed.

Most of the forces you list woudl either have zero or zero-sum effect.

> Finally, there is going to be assumed risk. We do not have the
> technology of Ringworld Engineers, Dyson's Spheres or Deathstars just
> yet. We barely have the technology to kludge together ISS,

Correction: The American Government (which dispite all misconceptions of
their population, strangely does not represent the sum total of all human
engineering capacity) barely has the political *interest* to kludge together
the ISS. Which is why they've used it as a pork programme the past twenty
years. See also 'Mir'. Or Skylab. Or NASA's Station C concept. Or Bigalow's
latest set of toys.

> The cost just to ship the materials into earth orbit, either from the
> ground or elsewhere, is huge. Currently, the $/lb (USD) cost for NASA
> is 20k-30k and for the commercial folks even to LEO is $5k to $10k

Actually NASA's up to about $50k - $100k at the moment. ;)

And the fuel costs to LEO are only about $40 per kilo. Me thinks there's a
little fat to be trimmed there. ^.^

John