Re: Cavorite Travel Times

pervect <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> On Mon, 1 Dec 2003 23:13:54 -0500, "Charles Talleyrand"
> <[EMAIL PROTECTED]> wrote:
> 
> >Cavorite is a useful material.  It blocks the force of gravity and can be used to
> >make a space ship in the following way:
> >
> >Make a large sphere with Cavorite shutters.
> >Close the shutters on the Earth's side blocking the Earth's gravity
> >Open the shutters on the Moon's side, letting the Moon pull us towards it.
> >
> >
> >Has anyone ever calculated the travel times this method requires?  It would
> >seem important to include a decelloration phase some time before
> >impact.  I would also like to go to other places beyond the moon.
> >
> >I just want to be sure this is where my investment dollar should go.
> >
> >-Thanks
> >-C.Talleyrand
> 
> Well, essentially you'll be in an orbit around the moon when you
> activate the cavorite.
> 
> We know that the moon orbits the Earth in about a month.
> 
> We also know that the orbital period follows the following
> relationship:
> 
> T^2 = (2*pi)^2 a^3 / GM
> 
> where a is radius of the orbit (for circular orbits), or the
> semi-major axis (for elliptical orbits).  (Keppler's law, basically,
> though I refreshed my memory from my physics textbook).
> 
> Therefore T is inversely proportional to the square root of the mass
> ratio.
> 
> The earth-moon mass ratio is .0123 (from the NASA planetary data fact
> sheet), so the period of an orbit is about 9 times larger.
> 
> This means that you'd have a 9 month period for a complete orbit.  The
> time from closest to furthest approach will be 1/4 an orbital period,
> or about 2.25 months.
> 
> Unfortunately, your velocity relative to the moon will be the negative
> of the moon's velocity relative to the earth.
> 
> The moon is moving at the right velocity to orbit a more massive body.
> Thus your velocity will be too high for a circular orbit around the
> moon.  I may be visualizing this wrong, but I think that you'll start
> out as close to the moon as you ever get, and as your orbit proceeds
> you'll get further away.
> 
> So you'd better have a third body (probably the sun) in the right
> position to kill off some of your excess lunar orbital velocity, and
> use its gravity to do some braking.

If you start at the equator and pull on the cavorite shutters all
around you, your ship will start to rise spontaneously because the
force of gravity is eliminated, but that of the centrifugal
acceleration will persist. In other words, you take off at 465 m/s,
though in a horizontal direction.

With that speed, it takes you about 10 days to reach Moon. Of course,
you should  account for the Moon's revolution while you're travelling.

When you're near the Moon, next step should be to get to the correct
orbit... You will be able to approach or, if desired, pass the Moon at
the relative speed of about 1100 m/s. Can anyone work out the details
of the mooning maneuver? What you want is the relative speed of zero.

N. B! you cannot use cavorite to take off from the near side of the
Moon. By closing the curtains on the Moon side you will merely
decrease the pressure you exert on the Moon, but it remains positive:
any celestial body opposite will be attracting Moon, anyway, and the
centrifugal force is always towards the Moon.