My first thought is that it's best to approach from a pole, so that you
don't have to fight centrifugal force to stay on after you land. (I'm
thinking of a small one where the asteroid's gravity won't be any
help.) Then deploy a mesh bag around the whole asteroid and have your
robots crawl around on the relatively predictable inside of the bag,
right side up relative to the centrifugal force once they leave the
pole.
I'd assume vehicle carrying people on this mission would have a docking module at it's c.g. which would dock at pole as you suggest. Believe we should just start boring at pole & store excavated material in containers we brought. If asteroid is 1km or > our bore tunnel could go away from axis & start to provide gravity from asteroid rotation for workers.
Still think we must put that mesh bag over outside of entire asteroid to assure asteroid doesn't fly apart from the boring. I think we should build whole first colony inside an asteroid as proposed in a 1964 book "Islands in Space" by Cox & Cole. Ed S.
It has been suggested that one could build a habitat from an iron
asteroid by boring into the center, putting an insulated bottle of
water in the center, refilling the whole, and then using mirrors to
melt the whole thing. When the heat finally melts the container of
water, the expanding steam causes the asteroid to balloon out into a
steam-filled iron bubble.
to melting, inserting a pipe, and gently adding nitrogen until you
have your bubble. More like a glass blower.
Dan Wylie-Sears schrieb:
>
> My first thought is that it's best to approach from a pole, so that you
> don't have to fight centrifugal force to stay on after you land. (I'm
> thinking of a small one where the asteroid's gravity won't be any
> help.) Then deploy a mesh bag around the whole asteroid and have your
> robots crawl around on the relatively predictable inside of the bag,
> right side up relative to the centrifugal force once they leave the
> pole.
>
> Any better ideas?
If the asteroid had a dust/sand-layer, I would not try to "land" the
"lander" but to let him slam down to scoop the dust into it's
container-body. The lander would be crash-hardened for sure.
Afterwards the lander get's up again to the mothership (with it's
thrusters), docks in and the mothership carries the lander back to the
ISS where the dust load can get analyzed.
If there are precious materials in this layer and I think there will be
a lot of them, like platinum, gold and if a near Sun asteroid was
choosen also he3, they could be obtained pretty simple since the
materials don't have to get grinded any more.
Another way would be to obtain stoney materials with robot arms from a
craft which hovers short above ground.
This would be also a container "lander" which does not land but just
collects materials until the container is full and docks than also back
into the mothership.
For that you need also observation and communication satellites which
have been brought with the mothership which is also a communication hub,
to the asteroid.
I made a design of this mothership (patent in UK, patent-applications
are pending in Germany and the US).
If you are interested take a look at
http://solar-thruster-sailor.info/figs/fig19-21d.html
or at
http://www.solar-thruster-sailor.info/PosterSSS.pdf .
The system enables direct launch of a mothership which can carry several
daughter units. Those daughter units would be already docked in at launch.
The mothership is a solar-electric spacecraft which also has solar sails
for fuelless attitude control and station keeping and has as well ample
solar cell arrays to power the craft and recharge the accumulators of
the daugher units.
Best wishes
Frank
The Solar Sail
From: Schonert Edward
> & start to provide gravity from asteroid rotation for workers.
Careful with that assumption. If the centrifugal force is greater than
the gravity of the asteroid, then what's holding the asteroid together?
Regards,
Mike Combs
From: sailor.barsoom
iron
> asteroid by boring into the center, putting an insulated bottle
of
> water in the center, refilling the whole, and then using mirrors
to
> melt the whole thing. When the heat finally melts the container
of
> water, the expanding steam causes the asteroid to balloon out
into a
> steam-filled iron bubble.
>
> Seems a bit chancy to me. Instead, I'd suggest heating the
asteroid
> to melting, inserting a pipe, and gently adding nitrogen until
you
> have your bubble. More like a glass blower.
I wrote a short sf story where a group of colonist use the former method
to start on their first "quick and dirty" habitat:
http://writings.mike-combs.com/havnrock.htm . I even managed to work in
a quick reference to the "Cole technique".
If I were writing the story again today, though, I'd probably describe
the method more like the latter proposal than the former.
Many Regards,
Mike Combs
"Combs, Mike" wrote:
>the gravity of the asteroid, then what's holding the asteroid together?
Probably the asteroids structure, if it is a single piece of material. I believe this is how astronomers currently determine the structural strength of asteroids, by checking if it's spin would pull it apart if gravity were all that was holding it together. This underestimates the strength of nickle-iron asteroids for sure, but it does determine which asteroids must be more than lumps of dust.
Sincerely
-Michael Persohn-Costa
"It is better to fail in originality than to succeed in imitation."
-Herman Melville
On Fri, Apr 11, 2008 at 7:09 PM, Michael Persohn-Costa
(...)
> Probably the asteroids structure, if it is a single piece of material. I
> believe this is how astronomers currently determine the structural
strength
> of asteroids, by checking if it's spin would pull it apart if gravity were
> all that was holding it together. This underestimates the strength of
> nickle-iron asteroids for sure, but it does determine which asteroids must
> be more than lumps of dust.
(...)
of known ones that rotate faster than what its gravity can hold. In fact the
only one that I know is 1998
KY26,
which rotates once each five minutes and is 30 meters across, so it has to
be strong enough to hold itself against an acceleration of 0.0001 g or so
(which despite being a ridiculous value would still be higher than its
gravity, I think).
IIRC, though, typically asteroids have periods of a few *hours*, resulting
in negligible centrifuge effect, and so using speed of rotation to find
strong asteroids would yield very few results, I am afraid.
Wasn't the question "the best way to land"?
Match the spin, then descend.
In my opinion.
To: spacesettlers@yahoogroups.comFrom: lucioc@...: Fri, 11 Apr 2008 19:22:52 -0300Subject: Re: [spacesettlers] What's the best way to land on a spinning asteroid?
On Fri, Apr 11, 2008 at 7:09 PM, Michael Persohn-Costa wrote:(...)> Probably the asteroids structure, if it is a single piece of material. I> believe this is how astronomers currently determine the structuralstrength> of asteroids, by checking if it's spin would pull it apart if gravity were> all that was holding it together. This underestimates the strength of> nickle-iron asteroids for sure, but it does determine which asteroids must> be more than lumps of dust.(...)I suspect that there are very few asteroids of the thousands and thousandsof known ones that rotate faster than what its gravity can hold. In fact theonly one that I know is 1998KY26,which rotates once each five minutes and is 30 meters across, so it has tobe strong enough to hold itself against an acceleration of 0.0001 g or so(which despite being a ridiculous value would still be higher than itsgravity, I think).IIRC, though, typically asteroids have periods of a few *hours*, resultingin negligible centrifuge effect, and so using speed of rotation to findstrong asteroids would yield very few results, I am afraid.
--- In spacesettlers@yahoogroups.com, "Lucio de Souza Coelho"
wrote:
> I suspect that there are very few asteroids of the thousands and
> thousands of known ones that rotate faster than what its gravity can
> hold.
"Measurements of the rotation periods of large asteroids in the main
belt show that there is a lower limit. No asteroid with a diameter
larger than 100 metres has a period of rotation of less than 2.2 hours.
For asteroids rotating faster than approximately this rate, the
centrifugal force at the surface is greater than the gravitational
force, so any loose surface material would be flung out. However, a
solid object should be able to rotate much more rapidly. This suggests
that the majority of asteroids with a diameter over 100 metres are
actually rubble piles formed through accumulation of debris after
collisions between asteroids."
RUBBLE PILES FULL OF WEALTH.
--- In spacesettlers@yahoogroups.com, "Lucio de Souza Coelho" wrote:> I suspect that there are very few asteroids of the thousands and > thousands of known ones that rotate faster than what its gravity can> hold.For the larger ones, wikipedia agrees:"Measurements of the rotation periods of large asteroids in the main belt show that there is a lower limit. No asteroid with a diameter larger than 100 metres has a period of rotation of less than 2.2 hours. For asteroids rotating faster than approximately this rate, the centrifugal force at the surface is greater than the gravitational force, so any loose surface material would be flung out. However, a solid object should be able to rotate much more rapidly. This suggests that the majority of asteroids with a diameter over 100 metres are actually rubble piles formed through accumulation of debris after collisions between asteroids."
From: Michael Persohn-Costa
material.
OK, as long as we have a firm understanding that although some asteroids
may be, most are probably a mix of different materials.
But even given that, of how much use is such spin gravity going to be?
I'd be surprised if it was more than a very few percent of a G, and
we're already concerned that the moon's 1/6th G is probably not enough
to maintain health.
I can think of only one way that the angular momentum of the asteroid
might be of some use in this regard. If we had a very long set of
cables and/or a long pressurized tunnel (I'd prefer the latter) going
out to a habitat sphere at the end, the sphere would be describing a
much wider circle with the same period than any point on or beneath the
surface of the asteroid. This might be a way to have useful amounts of
spin gravity while maintaining a convenient, non-rotating connection to
the asteroid itself.
Regards,
Mike Combs
I think the first phase of using asteroid material will be to bring
it to near-earth space, not to develop it in its original orbit. I
envision minimal processing with robots, so in that case it's
definitely a simple tether rather than a pressurized tube.
processing, and to store energy that can readily be used for the
final maneuvers near earth by simply releasing material from the end
of the tether. It would be spun up by using a mass driver at the end
of the tether. The initial spin of the asteroid just provides a head
start.
I suspect that small asteroids held together by their structure would
include a fair number with markedly faster spin than large asteroids
have. Over the eons, collisions have happened. Since there's more
off-center than center, most of the collisions would involve
significant change of spin. In roughly half the collisions, it would
add to the previous spin; in about an eighth of cases it would add
three times in a row, and so on. So we ought to be able to find a
small asteroid where the spin is enough to provide a fair amount of
ready-supplied angular momentum that we wouldn't have to build up
with the mass driver. But I don't know whether that imposes too much
of a restriction along with finding a good orbit.
--- In spacesettlers@yahoogroups.com, "Combs, Mike"
>
> From: Michael Persohn-Costa
>
> > Probably the asteroids structure, if it is a single piece of
> material.
>
> OK, as long as we have a firm understanding that although some
asteroids
> may be, most are probably a mix of different materials.
>
> But even given that, of how much use is such spin gravity going to
be?
> I'd be surprised if it was more than a very few percent of a G, and
> we're already concerned that the moon's 1/6th G is probably not
enough
> to maintain health.
>
> I can think of only one way that the angular momentum of the
asteroid
> might be of some use in this regard. If we had a very long set of
> cables and/or a long pressurized tunnel (I'd prefer the latter)
going
> out to a habitat sphere at the end, the sphere would be describing a
> much wider circle with the same period than any point on or beneath
the
> surface of the asteroid. This might be a way to have useful
amounts of
> spin gravity while maintaining a convenient, non-rotating
connection to
Most asteroids don't spin fast enough to present this kind of
a problem. That's the reason why the asteroid doesn't fly apart
to begin with. So, most of the time, a landing could be done
anywhere on it, with a corresponding small adjustment thrust.