h a l f b a k e r y
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Gravitational potential energy is what we want to feed off
Our solar system has a lot of rocks that are falling towards
the sun, but keep missing it because of their tangential
velocity. If some of them could be nudged so that their
velocity was no longer tangential, but pointed a bit
inward, then that potential energy would become ... more
accessible, albeit in slightly scary ways.
Of course, the nudge would need some energy itself, but
less than the kinetic energy that would ultimately become
Meanwhile, Mars is no fit place for human colonisation.
Why not? Well the gravity is so weedy that a human child
born there would (I hear) be fatally deformed. Also, the
gravity is so weedy that the place might struggle to hold on
to an atmosphere. Also, there's not much atmosphere -
needs a whole lot more oxygen, much of it bonded with
hydrogen. Also, it's cold.
Apparently, the current plans to put a human base on Mars
have a rule about not impacting the existing Martian
environment. I find this quite funny. In the past, European
colonists disgraced themselves by treating inhabited lands
as if they were uninhabited. That was a Bad Thing. Now,
however, we seem to be treating an uninhabited planet,
Mars, as if it were inhabited. I mean, to whom, exactly, are
we showing respect and consideration by leaving it
pristine? Anyway, enough of that rant.
Meanwhile, follow me to the asteroid belt. Yes, now you
mention it, it *does* occupy the next orbit out from Mars.
Unfortunately, there's not enough of it* to do more than
pilot this idea, but once we've proved the concept, we can
move on to the Kuiper belt and the Oort cloud to get some
scale. Notwithstanding any carping from NIMBYs on the
Now, if we hoik our POV out of the ecliptic plane for a
moment, we see that most of the asteroids are orbiting
anticlockwise (on the arbitrary assumption that we hoiked
north, not south). A few, however, have retrograde orbits.
That is, they are orbiting clockwise, from where we now sit.
Whether these are interlopers from another star system, or
just maladjusted, narcissistic rocks that don't play well with
others, let us regard them for the time being as our special
Imagine one of these retrograde-orbiting rocks dressed up
as a picador. Imagine the normal, anticlockwise rocks as
on-rushing bulls. We will need an initial investment of
energy and reaction mass to get the picador-rock close
enough to a bull-rock to initiate a gravitational interaction.
That's why, earlier on, we sent up a small spaceship with
some robots and some innocent-looking equipment in
crates, to park on the picador-rock and make a few
The picador rock now packs some sensors and, with the
aid of these, it divides on-coming bull-rocks into two kinds,
namely, rocks to throw and rocks to tap.
If it is going to throw a rock (i.e., alter its course so that its
orbit starts to decay), then we do one of those sling-shotty
things which have already been demonstrated by earlier
real-life space probes, the difference being that, the thing
we're sling-shotting around is of a similar order of
magnitude to the picador-rock itself, so its course is also
If it is going to tap a rock, it uses its picador-pike. Imagine
a giant steel knitting needle wedged right through the
middle of the picador-rock. The purpose of this is that it
should *only just* touch the bull-rock as it rushes past. If
there is more than the lightest touch, then the pike will snap
off. However, if the touch is judged just right, it will set the
picador-rock spinning. (The pike might be constructed in
sections, connected by a slack internal tether, so that, if the
end section does snap off and go spinning away into
space, the picador can reel it back in using that tether).
That pike tether is different and separate from the *other*
tether, which connects the picador-rock to the little
spaceship which arrived to fit it out. The attachment of this
other tether is very precisely related to the axis of spin
implied by the direction of the picador-pike, so that, after a
tapping contact, the tether does not get tangled by the
You see, we need a non-spinning object alongside the
spinning picador rock, in order to convert that spin into
electrical power. And we need the electrical power to
charge up the gimbal-mounted mass drivers which,
together with a modest amount of reaction mass, we use to
position and re-position the picador-rock between
encounters with bull-rocks.
You remember that there were sensors contributing to a
decision about which rocks to throw. Well, those sensors
are looking for two things, namely, evidence of high density
and evidence of water ice.
Any approaching object with one or the other (or both?) of
those things is to be sent in the ultimate direction of Mars
(possibly by way of a longish spiral path).
It is very important that they not strike Mars at a funny
angle. Two moons are quite enough. We are trying to
make Mars bigger and denser, not break bits off it. A
matador-vehicle based either on Phobos or Deimos would
therefore be used to land temporarily on the bull-rock
during its final approach to Mars, adjust its course so that it
bull's-eyes the red planet, and jump clear before it actually
does. Repeat this until Mars is heavy and watery enough,
(and with a bit of Martio-thermal energy) to support human
habitation. Then stop. That part is important. If we forgot
to stop before commencing colonisation, that would be
Now, bearing in mind that much of this activity (after the
initial pilot) is going to be based right out in the Kuiper Belt
and Oort Cloud, we'll have plenty of time to insert other
devices to capture energy from objects slingshotted past
them, and to store it so as to provide a future source of
energy for all those human-initiated activities which need to
be carried on sort-of within the solar system but too far
from the sun for solar panels to be much use. Early plans
envisage a Nickel-Metal Hydride double-A cell scaled up
volumetrically by a factor of the Japanese national debt
and parked in orbit off Pluto.
*According to Wikipedia, //99.9% of the asteroid belt's
original mass was lost in the first 100 million years of the
Solar System's history//. However, [8th of 7]'s solicitor has
advised him not to take questions on how *that* happened,
so we'll just have to work with what we've got.
The Adventures Of Don Quick (1970)
'The Benefits Of Earth' (Complete Episode) - Ian Hendry [Ian Tindale, Apr 03 2016]
apparent retrograde impact from 1939
[pertinax, Apr 04 2016]
||Mars has not yet been proved to be uninhabited,
although the definition of "uninhabited" might have
some bearing on the discussion.
||Inhabited by bacteria? Distinctly possible, underground.
Widely known to exist underground on Earth. Plus we
giant meteor impacts have spread Earth surface-debris
throughout the Solar System and beyond. Some lucky
Earthy bacteria might have been sent to Mars millions
or even a couple billions of years ago, and if they
arrived gently enough, their descendants could be all
over, not far beneath the surface.
||As for more-complex life-forms inhabiting Mars, that
seems rather less likely. They're generally not as tough
as bacteria, and Mars certainly does have a very harsh
environment. Nevertheless, if they exist, they have
adapted to that environment, and if we mess it up,
thinking that they don't exist, we could be making a Big
||I'm convinced. [pertinex] and [Vernon] are one and the same.
||Is there a Reader's Digest version ?
||[blissmiss], I disagreed with something [pertinax] wrote.
I'm definitely a different person.
||[pertinax], are you and [Vernon] married?
||So, if I guess correctly from my skim-read, the idea is
to slingshot useful asteroids into Mars to make it a
warmer, gravitier, wetter place?
||But why not also use some of the impacts to slow
down Mars' orbit and bring it closer to the sun?
Otherwise the heating bills are going to be crippling
when we move in.
||However, as soon as they find life there (and they
will), I think this idea becomes bad. Apart from
anything else, any life which is either orthogonal to
terrestrial life, or which has a couple of billion years
of independent evolution, is going to be immensely
valuable, and probably worth delaying any Martian
terraforming for a few decades.
||//Mars has not yet been proved to be uninhabited//
||OK, this is true. However, we might say (with a little poetic licence) that Loch Ness has not yet been proved not to have a monster. My point is, how many "haven't found anything yet" results do we want to accumulate before we are willing to conclude "there's probably nothing there"?
||//I disagreed with something [pertinax] wrote. I'm definitely a different person.//
||Non sequitur. I sometimes do that myself, given the passage of a little time.
||// [pertinax], are you and [Vernon] married? //
||What happens in Vegas stays in Vegas.
||//the idea is to slingshot useful asteroids into Mars to make it a warmer, gravitier, wetter place?//
||Yes. But you forgot the bit about the picadors. If there's no hat, we're not going.
||//probably worth delaying any Martian terraforming for a few decades.//
||I have no problem with that.
||[pertinax], we've barely started looking, and what
we've found so far pretty much excludes the surface
from having life-as-we-know-it. Underground,
however, perhaps only a decimeter or so, solar UV can't
reach and the perchlorates at the surface may not be
down there. But nothing so far sent to Mars can reach
that depth to see what's there.
||[MaxwellBuchanan], the reason Mars lost its
atmosphere was because its planetary magnetic field
stopped getting generated in its core. That let the Solar
Wind literally blow most of its atmosphere away. If we
decide the existing environment can be destroyed, then
what we should do is collide something BIG with Mars,
so as to re-melt the interior and let its magnetic field
generation system start up again. Or we could wrap it
in superconductors. and do the field-generating
||With a thick enough atmosphere, Mars can be plenty
warm enough. Mars doesn't have Earth's problem of
being too close to the inner edge of the Goldilocks
Zone. (In about 300 million years the prediction is that
naturally increasing Solar radiance will make Earth
uninhabitable, long long before the Sun turns into a red
giant.) To give Mars a thicker atmosphere, well, Venus
has plenty to spare (90 times as much atmospheric
pressure as Earth).
||Regarding pertinax, I've never met that person that I
know of. And I've never been married, either.
||OK, I'm happy to wait while bacterium-miners have a poke around. But, if they come up empty ...
||//But why not also use some of the impacts to slow down Mars' orbit and bring it closer to the sun?//
||Of course, the elegant thing to do would be to swap it with Venus - without damaging, you know, that other rock that orbits between them. Then, to terraform Venus, we'd have to raise its pH by bombarding it with those Oort Cloud objects made mostly of soap flakes.
||No no no. That would still leave you with two
inconveniently distant holiday homes. We should
||(1) put one or both of them into Earth orbit, at a
decent distance so that tidal effects aren't too
||(b) Put them both in solar orbits close to earth
(ditto above regarding tides), so that at least we
can hop across easily once every few orbits when
things line up.
||// [8th of 7]'s solicitor has advised him not to take questions on how *that* happened, //
||You can ask all the questions you like, it's just that we've been advised not to answer.
||Retrograde orbits sounds like trouble - prograde collisions between orbiting bodies are fairly tricky, because Dinosaurs. I'd be nervous about introducing retrograde objects into the inner solar-system which presumably is not just a cataclysmic eruption of ash and fire resulting in a global winter for a thousand years, but more a planetary vaporisation style event, should the calculations turn out to fail to take the metric system into consideration (for example). Poking with long sticks might be appropriate, but what speeds are we talking about with retro-vs-pro grade objects? Pretty fast, I'd warrant.
||// I'd be nervous about [...] a planetary vaporisation style event //
||But, since you ask, a quick Google suggest the order of 50km/s. Apparently, it's happened before (see link), and here we still are.
||You do realize, [pertinax], that everybody boos the picador?
||In space, no-one can hear you boo.
||Indeed, if you want to be a cosmastronaut you have
to lay off the boos.
||I am willing to pay a premium for fresh orbitals.