Kalpana One design (was Rotating space colonies)

Let's do a "back-of -the-envelope" reality check on the Brooks'
proposals listed below (edited for brevity). Wikipedia is the source of
all the basic information used in the forthcoming calculations except
for the density of meteorites ( (www.meteorites.com.au
).

1) The orbital velocity of the ISS is about 7.7 km/s at an average
altitude of about 350 km.

2) Meteoroids (small NEA's that enter the Earth's atmosphere) travel at
various orbital speeds in the vicinity of the Earth ranging up to 42
km/s. They also approach Earth in its orbit around the Sun at various
angles along the plane of the elliptic - from "overtaking" Earth from
behind to coming "head-on". The orbital speed of the Earth around the
Sun is about 29 km/s. Thus, any given small NEA could have a velocity
relative to the Earth ranging from 13 km/s ("overtaking" - 42 km/s plus
29 km/s)) to 71 km/s ("head-on - 42 km/s minus 29 km/s). The average of
these velocities is 42km/s. For the sake of argument (and to simplify
our calculation), lets say that we only want to try to capture the
slower NEA's with a velocity relative to the Earth of about 20 km/s.

3) The density of stony/iron NEA's averages about 4.5 gm/cm^3. The
density of nickel/iron NEA's ranges from 7gm/cm^3 to 8 gm/cm^3. We'll
call them about 7.5 gm/cm^3. If we want to use asteroids for
construction material (initially) we would prefer the nickel/iron NEA's.
We may not have the luxury of being that picky, though, so lets say we
capture a mixture of both - with an average density of about 6 gm/cm^3
(6000 kg/m^3).

4) We'll assume that we're only going to pick the NEA's that are about
4m. Again, for the sake of simplifying the calculations, lets assume our
NEA's are cubes. A 4 meter NEA would then be 64 m^3. This is about the
volume occupied by my (rather small) living room.

....to be continued - I have to go to work.

Chris

--- In spacesettlers@yahoogroups.com, "brooksn" wrote:
>
> --- In spacesettlers@yahoogroups.com, Matt Gallimore happygallimore@
> >
> > From: brooksn bhn1700@
> >
> > "But we aren't taking large asteroids from the asteroid belt, we are
taking 5 to
> > 10 meter asteroids that are passing by Earth, in fact they pass
within the
> > moon's orbit all the time. The amount of fuel needed to divert that
small an
> > asteroid just enough to enter the upper atmosphere for aerobraking,
strap on a
> > heat shield and you preserve more of the asteroid, is not very
costly
> > energetically. And then adjust the new elliptical orbit until you
meet up with
> > the ISS. "
> >
> > Agree that this can be done, but I have liability concerns bringing
objects
> > larger than 1 to 2 meters into the LEO.
>
> http://en.wikipedia.org/wiki/Meteoroid
> "Beech & Steel writing in Quarterly Journal of the Royal Astronomical
Society proposed a new definition where a meteoroid is between 100 m
and 10 m across."
>
> "The biggest asteroid to hit Earth on any given day is likely to be
about 40 centimeters, in a given year about 4 meters, and in a given
century about 20 meters."...
>
> >... "You have to travel to the location, mine it, then strap it to a
rocket (or
> > expensive mass driver) and then launch it. An asteroid can weight
100's of tons
> > and can be captured easily by adjusting an already Earth crossing
orbit. I doubt
> > 100's of tons can be sent up from the moon for the same cost."
> > .....
> > "But the purpose of your base was to launch material into orbit, you
need fuel
> > for that and volatiles in particular. Regolith or asteroid scrap,
radiation
> > shielding will be the easy part. What should be the number one
concern is cost,
> > energetically and monetarily and I don't see how a new lunar base
beats an ISS
> > small NEA capture. "...
> >
> > 1. Production scheduling
> > If we are doing orbital processing, then asteroid capture is done on
a schedule
> > of years to minimized fuel use adjusting dv....
>
>... Why? We can agree that start up costs favor ISS, but if 4 m bodies
are raining down on Earth once a year, how many are coming between Earth
and the moon? The Earth is ~6,300 km in radius, from Earth to the moon
is ~375,000 km, if we get one 4 m a year hitting Earth I can only
imagine we are getting over a dozen a year (being very conservative)
between us and the moon. 12 a year to pick from sounds like a pretty
generous production schedule. Sure you'll have to plan ahead for these
encounters and the first one will be a couple of years out (depending on
how much adjustment it needs) but once you get the 'train' of bodies
coming they'll come like clockwork from that point on....