(TGD) consensus: "Halfway to Anywhere" as a start?

(Was Re: NEA trajectory / relative velocity)
Ryan Healey wrote:
> Are you refereing to the dV required to get off this rock?
> Because if you are then it is also a problem for the moon and
anywhere else you plan to go, once your in HEO your pretty much right
next door in terms of dV.

Basically what I was saying.
Where the discussion was going (TGD) was the target from (the old
saying goes) "Halfway to Anywhere".
From the ground, it's all out of reach without a lot of effort, and
for any of this to work, you've got to have something going on in
Earth Orbit (Except for those who advocate doing everything on the
surface of the Moon or Mars. We seem to be in agreement that these
are going to be hard to do anything, except develop these bodies
exclusively -and where's the profit?).
To have a long term program with lots of growth potential (including
our dream; the stars & beyond?), you've got to have profit. To have
profit, you've got to have markets to serve with a product. It's hard
to foresee anything of this sort working from the surface of Mars or
Luna.
Therefore, HEEO seems to be the best attainable -relatively near
term. LEO is too limited: polluted, rare sunlight, too hard to get
to/from interplanetary space (including Luna, for all intents &
purposes). Jumping right into a base/space manufacturing facility
(SMF) on an NEA/Diemos is too far. Too hard to do now, and too far
from Earth markets.

As for the orbital velocity differences, I was waiting for Al or
somebody to quantify things.
I was more-or-less omitting consideration of the relative masses and
them orbiting the common center. I hadn't worked it out in detail,
but the mass differences between Earth, an NEA, or a spacecraft are
inconsequential compared to the differences in mass between any of
these & the Sun.
Perhaps a grain of zodiacal dust at 1AU might have a significantly
different orbit compared to Earth... But for something stepping off
the moving platform of HEEO or even LEO (moving at Earth's speed
around the Sun), the nearly circular orbit 1AU NEA has much less
relative velocity than the surface of Luna.

There's not much said about the O'Leary type plans to bring a chunk
of NEA back to HEEO intact, but that's the ultimate. It's why I said
that if anyone does this, then the Lunar mine is probably out of
business, except as an exploration base.
For a similar effort, you're not going to bring several hundred
million tons of refined ices, metals, and unprocessed rock to HEEO
from Luna. Maybe a mass driver could be emplaced, and run for several
years, but even then, it's not going to get the quality of materials.
It's true that there may very well be veins of ices & enriched
metals we know nothing about on Luna. All we have samples of is
erratic (probably impact ejecta) basaltic rock and regolith.
With an ~800 meter stony-iron NEA, we _know_ for a fact that there's
only a few percentage points difference between what we predict it'll
have, and what it is in fact. It will most certainly have close to a
certain percentage of ices, metals, and rock, all in the same volume
which we can handle. We'd have to do an extensive survey of the Moon
to find all this, and it won't be within 800 meters of each other and
~3km/sec from HEEO.

Back to "Halfway to Anywhere":
For the The Great Debate, do we agree that we'll need a SMF, probably
in HEEO?

John F. wrote
>>>>"... Its orbit is very like ours (definition of NEA). Similar
mean distance from the Sun necessarily means that its velocity around
the Sun is similar to ours around the Sun. Hence, low Delta-V
requirement."
andy-nimmo wrote:
>>> This is simply untrue. For its velocity to be similar to ours in
a similar orbit it would have to have similar mass to us, and none of
these do.
Al Globus wrote:
>> What matters is the ratio between the mass of the Sun and the
object orbiting about it. If the masses are reasonably similar they
each orbit about/in between them. As long as the sun's mass is
sufficiently dominant, the satellite effectively orbits around the
center of the sun regardless of its mass.
andy-nimmo wrote:
> No argument re your physics, but a major one with your
interpretation of the result. If Earth's mass is as domininant re the
asteroid's mass as the Sun's is to ours, then as far as we humans'
rocket engineering and fuel are concerned the velocity differences
will indeed amount to a high delta V - even if for general
astronomical puposes there may seem little difference.