Not sure I can see where lunar outweighs asteroid material.
Fuel costs, the moon includes launching all raw material from the lunar gravity well to LEO or GEO or where ever the base is. An asteroid has nearly no gravity well, especially borderline meteoroids which is what we'd likely use. The moon does not have to have to be captured though, so small asteroids would have to be found, (which there are some known NEO candidates), and adjusted to Earth orbit. Plus moving a 50 ton asteroid from a 'fly by' orbit to an aerobrake and capture orbit would seem to prove far less costly then moving 50 tons from the surface of the moon to lunar orbit much less Earth orbit. Also the moon has limited rocket fuel on site, whereas asteroids can provide a much larger range of fuel options.
Diversity of resources, the moon has very limited resources, Fe, Al, metal oxides, likely some amount of water on the poles, He3, etc. And in order to get more you'd have to 'travel' to the site on the moon, since it would seem unlikely that one site has everything you need. With asteroids essentially everything is available, from water/ammonia based dirty ice balls to carbonaceous to iron and everything inbetween.
Gravity, there's likely an advantage for the moon in regards to gravity, all mining and extraction techniques include Earth gravity in their process. It would be assumed that moon gravity would not be much different but zero g probably would. Also astronauts will likely be better off in the lower lunar gravity then the zero go of ISS. (Though with a rotating section or station that could change to whatever g we wanted.)
Energy, unless you stay at the poles and use a tower near the 'peak of eternal light' the moon will have limited solar energy (~50%). ISS would have a constant energy supply. The lunar base, if not at the pole, would have large swings in temperatures through the month and high heating/cooling bills to keep the station at a good temperature through out.
I could be missing something though, so I'm open to new information.
Brooks
--- In spacesettlers@yahoogroups.com, "csmyth3025" wrote:
If we capture asteroids then the constant distance is still there. Traveling on the moon from impact site to impact site and then launching what you find from the lunar gravity seems more costly then finding an NEA and capturing it. Though more available many volatiles are still missing and only in concentrated form at the poles.
Brooks
On 9/30/10 2:58 PM, brooksn wrote:
True. But that requires a whole lot of energy. Even if the asteroid
mass is negligible, you have the delta-V of getting to the asteroid and
then getting back to Earth orbit, which must be provided entirely by the
rocket equation. And of course we wouldn't want a zero-mass asteroid;
but the more mass it has, the more energy (and reaction mass) it will
take to change its orbit.
Getting stuff to/from the Moon requires delta-V too, but you have
options other than rockets to do it. In particular, for the large
amount of mass you would be shipping FROM the Moon, you could use a Mass
driver, which requires no reaction mass and doesn't rely on the rocket
equation.
> Traveling on the moon from impact site to impact site and then launching
> what you find from the lunar gravity seems more costly then finding an
> NEA and capturing it.
I don't see how. Again, you can move around on the lunar surface just
by turning wheels. To change orbits in space requires rockets. We
don't move things around on Earth using rockets, because they're
horrendously expensive (no matter how you measure it) compared to simply
pushing against the ground (or something bolted to the ground, such as
tracks).
> Though more available many volatiles are still
> missing and only in concentrated form at the poles.
True enough. But the majority of the mass you need to build a colony is
radiation shielding. Any old regolith or slag will work for that. As
Mike says, we'll probably end up using both, as well as materials
launched from Earth. But I will bet that the vast majority of the
material ending up in the first colonies will be lunar in origin.
Best,
- Joe
--- In spacesettlers@yahoogroups.com, Joe Strout wrote:
>
> On 9/30/10 2:58 PM, brooksn wrote:
>
> > If we capture asteroids then the constant distance is still there.
>
> True. But that requires a whole lot of energy. Even if the asteroid mass is negligible, you have the delta-V of getting to the asteroid and then getting back to Earth orbit, which must be provided entirely by the rocket equation. And of course we wouldn't want a zero-mass asteroid; but the more mass it has, the more energy (and >reaction mass) it will take to change its orbit.
> Getting stuff to/from the Moon requires delta-V too, but you have
> options other than rockets to do it. In particular, for the large
> amount of mass you would be shipping FROM the Moon, you could use a Mass
> driver, which requires no reaction mass and doesn't rely on the rocket
> equation.
My understanding is that mass drivers require very large amounts of energy and infrastructure, which might reduce delta-V energy costs, but would likely explode the actual monetary budget.
> > Traveling on the moon from impact site to impact site and then launching
> > what you find from the lunar gravity seems more costly then finding an
> > NEA and capturing it.
>
> I don't see how. Again, you can move around on the lunar surface just
> by turning wheels. To change orbits in space requires rockets. We
> don't move things around on Earth using rockets, because they're
> horrendously expensive (no matter how you measure it) compared to simply
> pushing against the ground (or something bolted to the ground, such as
> tracks).
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.
> > Though more available many volatiles are still
> > missing and only in concentrated form at the poles.
>
> True enough. But the majority of the mass you need to build a colony is
> radiation shielding. Any old regolith or slag will work for that. As
> Mike says, we'll probably end up using both, as well as materials
> launched from Earth. But I will bet that the vast majority of the
> material ending up in the first colonies will be lunar in origin.
>
> Best,
> - Joe
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.
Brooks
From: brooksn bhn1700@...
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 concernsbringing objects
larger than 1 to 2 meters into the LEO.
"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. "
Depends on the goal. For basic research / processing, getting a couple tons to
the ISS should be easier than moving equipment to the moon. If we are planning
to build something big, the moon looks more interesting, at least for the next
few decades. Though the mass driver is starting to look not as easy as Oneal
proposed,nonetheless, the moon offers some advantages:
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.
With lunar facilities(admittedly more expensive) a more predictable production
schedule is possible.
2. Short communication lags
Being closer, teleoperation is easier.
3. Hardware reuse
Orbital capture approaches would have small craft hunting individual asteroids.
If problems develop (communication, mechanical), the craft is lost. On the
moon, there is a chance for repair or using salvaged components to repair other
units.
4. Processing
After some thought, I am not sure that material processing is more difficult in
zero g. There are ways to address it with a large enough facility. That said,
actual mining and material handling are aided by gravity. Initial ore
collection should be easier to engineer on the moon. No de-spinning of ore
needed.
5. Scalability
In many ways it is easier to leverage fixed facilities. Managing a flotilla of
small asteroid capture craft and orbital insertion involves long investment
cycles and more complexity as production increases. Expanding the processing
facilities in LEO would be less expensive than the moon, but high production
rates will be elusive until asteroid processing moves out of LEO. Once
asteroids weighing many thousands of tons can be handled, things look very
different. Until then, the moon offers potentially easier production
scalability. Most hab mass is not heavily processed. Very little mass of a
shielded hab is related to volatiles, carbonor metals uncommon to the moon.
Thereore, facilities could be progressively expanded with, hopefully, better
predictability of production. This becomes important when trying to build
structures weighing hundreds of thousands of tons.
Hello all,
Even if it would not make contact with surface, there would still be some odds that the rock would break up from stress, heating, whatever. Presumably by the time we are at this point there would be multiple space stations in LEO that would also be put at risk (not to mention taking out some satellite).
There have been too may events where people "knew" what they were doing and still screwed up bad (BP oil spill, NASA - mars probe where they used wrong units, Columbia and Challenger were both "evaluated" and blessed off), etc.
I personally lean towards moon, simple because it would be easier have human presence to monitor, maintain, etc., but it is ~60/40. If we found an asteroid with most of what we want that could be harvested under reasonable conditions then I would be swayed easily. However, the odds of aerobraking in earth atmosphere are nil. Out of curiousity, is there a specific asteroid that is even viable on paper with reasonable delta-v?
--- On Thu, 9/30/10, brooksn wrote:
Subject: [spacesettlers] Kalpana One design (was Re: Rotating space colonies)
To: spacesettlers@yahoogroups.com
Date: Thursday, September 30, 2010, 11:26 PM
--- In spacesettlers@yahoogroups.com, Joe Strout wrote:
>
> On 9/30/10 2:58 PM, brooksn wrote:
>
> > If we capture asteroids then the constant distance is still there.
>
> True. But that requires a whole lot of energy. Even if the asteroid mass is negligible, you have the delta-V of getting to the asteroid and then getting back to Earth orbit, which must be provided entirely by the rocket equation. And of course we wouldn't want a zero-mass asteroid; but the more mass it has, the more energy (and >reaction mass) it will take to change its orbit.
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.
> Getting stuff to/from the Moon requires delta-V too, but you have
> options other than rockets to do it. In particular, for the large
> amount of mass you would be shipping FROM the Moon, you could use a Mass
> driver, which requires no reaction mass and doesn't rely on the rocket
> equation.
My understanding is that mass drivers require very large amounts of energy and infrastructure, which might reduce delta-V energy costs, but would likely explode the actual monetary budget.
> > Traveling on the moon from impact site to impact site and then launching
> > what you find from the lunar gravity seems more costly then finding an
> > NEA and capturing it.
>
> I don't see how. Again, you can move around on the lunar surface just
> by turning wheels. To change orbits in space requires rockets. We
> don't move things around on Earth using rockets, because they're
> horrendously expensive (no matter how you measure it) compared to simply
> pushing against the ground (or something bolted to the ground, such as
> tracks).
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.
> > Though more available many volatiles are still
> > missing and only in concentrated form at the poles.
>
> True enough. But the majority of the mass you need to build a colony is
> radiation shielding. Any old regolith or slag will work for that. As
> Mike says, we'll probably end up using both, as well as materials
> launched from Earth. But I will bet that the vast majority of the
> material ending up in the first colonies will be lunar in origin.
>
> Best,
> - Joe
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.
Brooks
--- In spacesettlers@yahoogroups.com, Matt Gallimore wrote:
>
> 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 concernsbringing objects
> larger than 1 to 2 meters into the LEO.
"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."
If the above is accurate, then 10 m is considered the upper limit for a meteor. So it is expected to burn up without incident, especially considering its estimated that 4 m bodies hit Earth every year. I definitely agree we should start small 1 to 2 but going up to around 5 shouldn't be a problem after proof of concept on the smaller bodies.
http://en.wikipedia.org/wiki/Near-Earth_asteroid#Near-Earth_asteroids
"Objects smaller than about 150 m (500 ft) in diameter (i. e. H = 22.0 with assumed albedo of 13%), are not considered PHOs (Potentially Hazardous Objects)."
Not that I'd want to get remotely close to that limit.
> "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. "
> Depends on the goal. For basic research / processing, getting a couple tons to
> the ISS should be easier than moving equipment to the moon. If we are planning
> to build something big, the moon looks more interesting, at least for the next
> few decades. Though the mass driver is starting to look not as easy as Oneal
> proposed,nonetheless, the moon offers some advantages:
>
> 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.
> With lunar facilities(admittedly more expensive) a more predictable production
> schedule is possible.
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.
> 2. Short communication lags
> Being closer, teleoperation is easier.
Agreed, since we've pretty successfully ran rovers on Mars though, I think it may be manageable.
> 3. Hardware reuse
> Orbital capture approaches would have small craft hunting individual asteroids.
> If problems develop (communication, mechanical), the craft is lost. On the
> moon, there is a chance for repair or using salvaged components to repair other
> units.
Also agree, but how much of an increased risk is this? Sure it goes in lunar's favor but compared to all the other costs?
> 4. Processing
> After some thought, I am not sure that material processing is more difficult in
> zero g. There are ways to address it with a large enough facility. That said,
> actual mining and material handling are aided by gravity. Initial ore
> collection should be easier to engineer on the moon. No de-spinning of ore
> needed.
Agreed.
> 5. Scalability
> In many ways it is easier to leverage fixed facilities. Managing a flotilla of
> small asteroid capture craft and orbital insertion involves long investment
> cycles and more complexity as production increases. Expanding the processing
> facilities in LEO would be less expensive than the moon, but high production
> rates will be elusive until asteroid processing moves out of LEO. Once
> asteroids weighing many thousands of tons can be handled, things look very
> different. Until then, the moon offers potentially easier production
> scalability. Most hab mass is not heavily processed. Very little mass of a
> shielded hab is related to volatiles, carbonor metals uncommon to the moon.
> Thereore, facilities could be progressively expanded with, hopefully, better
> predictability of production. This becomes important when trying to build
> structures weighing hundreds of thousands of tons.
As production increases in LEO I would expect complexity to drop, the first few will be the trickiest, as hardware is used in all areas the bugs work out and the personel becomes more experienced. How much scalability are you anticipating? If we process six 5 m asteroids a year in LEO at 400 tons a pop, that's 1200 tons a year. After a few years of production and expansion we should have quite a station built up I would think. On the mass for shielding, both locations provide it, though moving around 100's of tons of mass on the moon will be more difficult then in zero g. But volatiles provide a monetary/energy problem for the moon, there is a greater need on the moon and a greater shortage as well.
Brooks
Well I lean 80:20 to asteroid/LEO, but can be convinced otherwise.
http://neo.jpl.nasa.gov/risk/1991ba.html
http://en.wikipedia.org/wiki/1991_BA
Here's a nice one behind door number 2 for your shopping pleasure. It's a 6 meter beauty weighing in it a modest 374 tons, and she's already passed within 160,000 km of Earth before, half the distance to the moon. :)
Brooks
--- In spacesettlers@yahoogroups.com, Christopher Pratt wrote:
The thread has compared cost between two scenarios. I wonder which strategy would be more dangerous to the workers? I was trying to imagine the actual work involved. It can't all be roboticized, just as work now on the ISS isn't. If it is related, also, which condition would be more dangerous, processing ore in low gravity, no gravity, or normal gravity? I mean, dangerous to the humans involved. I know you'll say, 'different dangers,' but would it be possible to consider this element as a 'cost factor' in any case, and make a decision as to which situation is the more costly in terms of human life?
On 9/30/10 10:26 PM, brooksn wrote:
> 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.
I think we need some real numbers -- it seems to me that changing the
orbit of a few hundred tons of anything DOES cost quite a lot
energetically. You'll need reaction mass -- a lot of it -- and if you
object to a mass driver on the Moon, you should object even more
strenuously to one on a passing NEA. So that means that the reaction
mass has to be fuel and oxidizer. Quite a lot of it, so now in addition
to the hundreds of tons of asteroid, you're also accelerating all that fuel.
Sounds hard to me.
> My understanding is that mass drivers require very large amounts of
> energy and infrastructure, which might reduce delta-V energy costs, but
> would likely explode the actual monetary budget.
I don't think so. Energy's cheap on the Moon, at least during the day
(or if you have a sub-sized nuclear power plant). And the
infrastructure isn't much compared to what you'd need to process an
asteroid. Mostly struts and coils of wire.
Best,
- Joe
Chris,
I'm neither an engineer nor a mathematician, so I'll just have to trust you on your figures. As to your scenario, though, I will comment. First, It still seems to me that you are putting the cart before the horse. At present we have One (1) damn flimsy space station (sans gravity of any sort) in orbit and One (1) experimental Bigelow habitat at half size. We have NO facilities on the moon, or elsewhere to provide living space for humans, let alone to provide materials for the construction of a large habitat. The first steps (and THAT is the primary imperative that MUST concern us if we are EVER going to establish a permanent presence in space), are to provide low cost access to space for men and materials and to provide facilities for those men (and women) to live and work in an environment that will allow them to retain their musculo-skeletal strength and health over the long term so that they can return to Earth if they so desire. Given the state of the worlds varied economies, NO-ONE is going to be investing hundreds of billions of dollars to construct a huge habitat right off. Therefore, we need to come up with a way to get workable habitats in space that don't call for that level of investment. Once we have large numbers of people living and working in space, and the nations see that it can be economically fruitful and that people are determined to settle there despite the apathy of governments, interest in further development will begin to grow.
In the beginning, though, we need to start simple and cheap. Suppose we place seven (7) shuttle external tanks in a stable orbit and arrange them in a rosette (six arrayed around a seventh placed in the center), weld them and cable them together to form a single cylindrical unit. Each tank has the dimensions 154'X27.6', which gives us an outer circumference of roughly 260' and a length of 154'. if we then install a flat deck in each of the tanks so that as the structure rotates it becomes the floor, we should end up with a usable area of about 40,000 sq' under 'gravity'. distance from the 'floor to the center of rotation would be in the neighborhood of 35-40', so one might experience some slight disorientation due to coriolis forces, frankly I'm not sure (but neither is anyone else), but chances are it could be gotten used to. SHIELDING, yes, the BIG problem. Again, I don't know what can be done about that, unless possibly a barrier could be built, between the sun and the structure, composed of materials brought up in bulk from Earth (concrete, H2O, pulverized rock, etc.), certainly one would think that we will have saved enough by utilizing available resources for the structure to finance a bit of shielding.
In any case, this is just a rough scenario, but you take my point. We have to start with what we HAVE and develop that as far as we possibly can to get an infrastructure in space that will be able to form the workforce that WILL work on the dedicated worldlets like Kalpana 1 and the O'neil habitats, and others that we can't even envision today. Without places like my little mock-up above, I fear that we may never get the people and resources into space that are necessary for us to begin the process of industrializing and colonizing our planetary space, let alone interplanetary spaces.
Victor
Sent: Thursday, September 30, 2010 5:34 AM
To: spacesettlers@yahoogroups.com
Subject: [spacesettlers] Kalpana One design (was Re: Rotating space colonies)
Your point is well taken, Victor - but we need to distinguish between an
"orbiting space colony" and those facilities that will necessarily
precede its construction. I would put these predecessor facilities
(habitats, if you prefer) more into the category of construction shacks
or construction camps. These types of facilities will be needed, of
course - both on the Moon (the most likely source of raw and processed
construction materials) and in orbit (to effect the construction of the
station). The initial facilities on the Moon will likely develop into
lunar colonies in their own right - in much the same way that Boulder
City, Nevada has become a city with its own economic base despite its
purpose-built function as quarters for the workers (and in many cases,
their families) who were constructing the Hoover Dam (a 5-year project
that was in 1931-1936 located in an isolated and remote area).
I'm inclined to think that a 100-person orbiting space colony is about
as small a "village" as you could get. Anything smaller would most
likely be a corporate or government "purpose-built" facility. There will
no doubt be larger colonies built - such as Kalpana One - designed to
house 3000 people and more. In this respect, I agree that Kalpana One is
a 2nd or 3rd generation facility. A 100 person facility is a first
generation true orbiting space colony in my mind.
Constructing a Stanford Torus-type 100 person facility is a massive
undertaking. If one takes the 1977 Ames Research Center study for
shielding requirement for radiation workers (5 rem/yr) as a baseline
requirement (with shelters akin to "hurricane shelters" to weather
infrequent intense CME's from the Sun), the shell of the torus and, I
would think, the "spokes" as well, will have to be constructed with
about 2800 kg/m^2 "walls". As it turns out, this mass is equal to about
1 meter of "typical" concrete - which has a mass of about 2400 kg/m^3.
High density concrete is more than twice as dense as "typical concrete"
so a designed concrete shell one meter thick with a 3,000 kg/m^3 density
should be easily achievable. Likewise, glass for skylights (more likely,
lightwave guides) is about as dense as concrete (ranging from 2000
kg/m^3 to ~8000 kg/m^3). A one meter thick shell of reinforced concrete
and glass "skylights" seems a reasonable design point.
The amount of mass for this shell is tremendous. If one assumes that the
torus has, as I stated in my previous post, a radius at the main "deck"
of 223.4 meters and a "tube" diameter of 15 meters, the surface area
that must be covered is 66,146 m^2 [Area=(4*pi^2*a*r)+(4*pi^2*r^2),
where a=the inner radius of the torus and r=the radius of the torus
"tube"]. The mass of the shell of the torus alone comes in at a
staggering 198,438,178 kg.
If one assumes that the torus is connected to the central hub by three
15 meter diameter "spokes", the surface area of these spokes will be
30,522 m^2 [pi*15 m*215.9 m*3]. At 3000 kg/m^2 the mass of the spokes
adds another 91,566,430 kg.
By my calculation the mass of a 100 person Stanford Torus-type space
colony with three "spokes" adds up to about 290,004,600 kg. If we add
another 10,000,000 kg for the hub and miscellaneous structures that
brings the total up to about 300,000,000 kg, or about 300,000 metric
tons. This is a lot less than the 7 million metric tons for Kalpana One,
but it's still a huge amount of material.
I suspect that such a facility will probably be built by transporting
components (from the Moon, most likely) to the orbiting construction
site. In this regard I envision the components as sections similar to
the cylinder sections used to construct the English Channel tunnel.
Any comments on this scenario (or my calculations)?
Chris
--- In spacesettlers@yahoogroups.com, "Victor Smith"
>
...The stated mass requirements for the Kalpana 1 is 7 million tons
(including shielding). The authors of the plan therefore specefied that
the habitat must be assembled from materials derived from either the
moon or NEO asteroid harvesting, either of which is going to require a
whole infrastructure of its own. This is why I say that K-1 is, at best,
a second generation habitat, and probably 3g.
> > My understanding is that mass drivers require very large amounts of
> > energy and infrastructure, which might reduce delta-V energy costs,
> > but would likely explode the actual monetary budget.
>
> I don't think so. Energy's cheap on the Moon, at least during the
> day (or if you have a sub-sized nuclear power plant). And the
> infrastructure isn't much compared to what you'd need to process
> an asteroid. Mostly struts and coils of wire.
There's been later talk of much larger sized EM accelerators for launching tanks of liquefied oxygen from the moon. But we shouldn't let those much more ambitious proposals skew our perceptions of using mass drivers for lunar or asteroidal ore retrieval.
Regards,
Mike Combs
Absolutely, Brooks. It's the tourism guys that are keeping us in the race at present. Imagine where we'd be right now without all the private aerospace companies infusing enthusiasm, new tech and public relations into the space movement. We'd be at a standstill. They get, and will continue to receive BIG KUDOS from me.
Victor
Sent: Thursday, September 30, 2010 8:45 AM
To: spacesettlers@yahoogroups.com
Subject: [spacesettlers] Kalpana One design (was Re: Rotating space colonies)
I would agree with the vocations mentioned for the colony but I would add one more big one, tourism. It definitely doesn't inspire the exciting science based or exploratory visions most space enthusiasts have when we think of humanity expanding into space. But it is right now more economically viable as a human expanding space oriented industry then anything else we have going, except government of course. So I would add hotel workers and guests to the list of inhabitants.
Brooks
--- In spacesettlers@yahoogroups.com, "Victor Smith" wrote:
Interesting, well radiation would be worse on the moon since it is outside the magnetic field of Earth vs. ISS which is very much within. I could only guess on ore processing, if the moon uses Earth processes, then high temperatures and pressures, acids, etc. may be involved, if ISS uses zero g to seperate through modest and repeated centrifuges/distillation then not much at all but I am very much guessing on that one. ISS has an 'escape pod' for emergencies that can get the crew home, the moon has no such ability, it would be a launch and 3 days to make it back home. Not a huge burden but a consideration. Also the moon likely has an advantage with 1/6 gravity, the harm to the human body by zero g is substantial, the moon may partially or mostly remove that harm. (Though a spinning habitat removes the issue, we don't have one yet or know its complexity, nor if ISS could even be retrofitted to have one.)
--- In spacesettlers@yahoogroups.com, "janet_baker76" wrote:
--- In spacesettlers@yahoogroups.com, Joe Strout wrote:
>
> On 9/30/10 10:26 PM, brooksn wrote:
>
> > 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.
>
> I think we need some real numbers -- it seems to me that changing the
> orbit of a few hundred tons of anything DOES cost quite a lot
> energetically. You'll need reaction mass -- a lot of it -- and if you
> object to a mass driver on the Moon, you should object even more
> strenuously to one on a passing NEA. So that means that the reaction
> mass has to be fuel and oxidizer. Quite a lot of it, so now in addition
> to the hundreds of tons of asteroid, you're also accelerating all that fuel.
>
> Sounds hard to me.
> > My understanding is that mass drivers require very large amounts of
> > energy and infrastructure, which might reduce delta-V energy costs, but
> > would likely explode the actual monetary budget.
>
> I don't think so. Energy's cheap on the Moon, at least during the day
> (or if you have a sub-sized nuclear power plant). And the
> infrastructure isn't much compared to what you'd need to process an
> asteroid. Mostly struts and coils of wire.
>
> Best,
> - Joe
I can't find the reference, but I've heard the mass driver requires a pretty substantial amount of energy. You have to build all the infrastructure for the moon, the base to live in, the coils, the track, the power plant, the baskets, something to catch it in orbit, or at a lagrange point, then they'd still have to process it there. Unless you process on the moon and then launch. None of which has been done, unlike the asteroid which is doing everything we've already done before. Adjusting an asteroids orbit, aerobraking in an atmosphere, etc. the new part is the processing of the ore which will be the same for both locations.
Brooks
"janet_baker76" wrote:
>
> The thread has compared cost between two scenarios. I wonder which strategy
>would be more dangerous to the workers? I was trying to imagine the actual work
>involved. It can't all be roboticized, just as work now on the ISS isn't. If it
>is related, also, which condition would be more dangerous, processing ore in low
>gravity, no gravity, or normal gravity? I mean, dangerous to the humans
>involved. I know you'll say, 'different dangers,' but would it be possible to
>consider this element as a 'cost factor' in any case, and make a decision as to
>which situation is the more costly in terms of human life?
In the next 20 years expect robotics to undergo a revolution, developing far
greater capabilities and at far lower cost. As this occurs, an orbital facility
/lunar base would not inherentlly need human presence, just resupply of spare
parts.
Before expressing too much hubris about what humans can do better: any tool we
could use, we could still use with telepresence.
Looked at that way, if there is no premium to the human experience of working in
space, then we could reduce human life risk to where it is not a "cost factor."
On 10/1/10 11:22 AM, brooksn wrote:
> 'float' off the asteroid and use the gravity of the spacecraft to nudge
> the asteroids trajectory. ... The energy requirements would be modest.
Not if you're still talking about capturing an asteroid into Earth
orbit. We're talking about a 300-ton asteroid that ranges from 0.7 to
3.6 AU from the Sun. You're not going to circularize that and match
Earth orbit just by parking a spacecraft next to it.
> NASA has already done this.
I wasn't aware that this had ever been done except on paper. Do you
have more details?
Best,
- Joe
Twenty years? Hmmm. The Japanese have been giving it a lot of attention in the last twenty years, due to their severe demographic problem, but they haven't cracked that nut. I would think we'd see some progress, but in twenty years, everything roboticized to the point of needing no human presence? Hmmm. Let's assume not, just for discussion. In that case, which of the scenarios you've been discussing would be more dangerous to workers?
From: janet_baker76
last twenty years, due to their severe demographic problem, but they haven't
cracked that nut. I would think we'd see some progress, but in twenty years,
everything roboticized to the point of needing no human presence? Hmmm. Let's
assume not, just for discussion. In that case, which of the scenarios you've
been discussing would be more dangerous to workers?"
If humans must do the work, then the moonis more dangerous.
-Travel to and from the moon is more difficult, and therefore riskier.
-There are more options (rocket designs)that could ferry emergency supplies to
a orbital station. Getting to the moon will be very limited. Even if China,
Russiaand the US design rockets capable of delivering large payloads to the
moon, the general sentiment remains true.
- Evacuation of an low Earth orbit station is easier thanleaving themoon.
- Moon walksbring in dust to the habitat that is surely to give silicosis-like
respiratory problems.
- Lunar excursions would wear out spacesuits, giving another hazard.
Robotics will lessen the risks given above. In fact, I do not think we will get
out into space building anyreally large structureswithout a heavy use of
robotics. One reasonwill be safety.
I read the article you linked to Brooks. I suspect that engineers have
looked at the possibility of using window area as a means of eliminating
waste heat. I'm not familiar with the way they approach the thermal
regulation problem from a design standpoint, so if anyone else can shed
some light on the thinking that has been used in the design of the ISS
(and space stations in general), please let us know. I think Brooks has
a valid question here.
--- In spacesettlers@yahoogroups.com, "brooksn" wrote:
>
> http://science.nasa.gov/science-news/science-at-nasa/2001/ast21mar_1/
>
> Reading the above article, "Windows are a tremendous heat leak", also
it states that "MLI insulation does a double-duty job: keeping solar
radiation out, and keeping the bitter cold of space from penetrating the
Station's metal skin."
>
> And then it goes onto the issue of heat exchangers and radiators. But
if we were to design the station to use the windows for its heat loss
and use different insulation so that we protect from radiation but
reduce the 'thermos' effect we may reduce our need for external
radiators. What am I missing here? I understand if the effect is small,
then it would have a small effect. But right now they are saying the
window is a tremendous heat leak, that's a strong statement. And the
insulation is designed 'for' keeping heat in, but if use the windows and
less effective insulation it would seem a win win.
I agree with you 100% Victor. The first step is to provide a robust and
(relatively) cheap access to LEO. Secondly, we need a robust LEO
infrastrucure that can support the assembly and fueling of vehicles to
the Moon or other sources of raw materials. These LEO facilities will
also have to accomodate the assembly and fueling of vehicles to
transport prefabricated habitats, material processing facilities and
fabrication facilities to their point of usage.
establishing a robust LEO presence warrant seperate threads in their own
right. The subject of this thread (rotating space colonies) is, I think,
oriented towards the development of a permanent rotating colony in HEO
(above the protection of the Van Allen belts) - probably in a 2:1
resonance orbit with the Moon.
At this point we don't have the means to directly access a HEO facility.
Thus, LEO infrastructure (inside the protection of the Van Allen belts)
is our only practicle "jumping off" point to send out the personnel and
prefabricated facilities that will allow us to create the infrastructure
for HEO and beyond. Fortunately, this LEO infrastructure doesn't need
the sort of shielding that facilities outside the Van Allen belts will
need.
I don't know if there are already active threads in this forum on the
topic of cheap access to LEO and the LEO infrastructure needed to
support activities on the Moon or HEO. If not, perhaps we should start
threads on these subjects. This thread on rotating space colonies
assumes that the prerequisite mining, processing, fabrication and
transportation facilities are in place to allow for the admittedly large
scale effort needed in the construction of such a colony.
Chris
--- In spacesettlers@yahoogroups.com, "Victor Smith"
>
> Chris,
> I'm neither an engineer nor a mathematician, so I'll just have to
trust you on your figures. As to your scenario, though, I will comment.
First, It still seems to me that you are putting the cart before the
horse. At present we have One (1) damn flimsy space station (sans
gravity of any sort) in orbit and One (1) experimental Bigelow habitat
at half size. We have NO facilities on the moon, or elsewhere to provide
living space for humans, let alone to provide materials for the
construction of a large habitat. The first steps (and THAT is the
primary imperative that MUST concern us if we are EVER going to
establish a permanent presence in space), are to provide low cost access
to space for men and materials and to provide facilities for those men
(and women) to live and work in an environment that will allow them to
retain their musculo-skeletal strength...
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
).
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....
>Twenty years? Hmmm. The Japanese have been giving it a lot of attention in the last twenty years, due to their severe demographic problem, but they haven't cracked >that nut. I would think we'd see some progress, but in twenty years, everything roboticized to the point of needing no human presence? Hmmm. Let's assume not, just >for discussion. In that case, which of the scenarios you've been discussing would be more dangerous to workers?
Well, NASA has had two functioning robotic rovers on Mars for several years, carrying out a limited number of tasks.
--- In spacesettlers@yahoogroups.com, "csmyth3025"
>
> 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
minus
> 29 km/s)) to 71 km/s ("head-on - 42 km/s plus 29 km/s). The average of
> these velocities is 42 km/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.
volume will be about 33.5 m^3. We'll be conservative and say that the
NEA's we're going to capture are about 30 m^3. At an average density of
6,000 kg/m^3 our NEA will have a mass of 180,000 kg (180 metric tons).
5) In order to put our NEA in an orbit around the Earth close to the
orbit of the ISS, we'll need to slow it down from about 20 km/s to about
7.7 km/s (the orbital velocity of the ISS). This is a change of 12.3
km/s, or 12,300 m/s. If we multiply the mass of our NEA (180,000 kg)
times the change in velocity we need to make (12,300 m/s) we get
2,214,000,000 kg*m/s (for the scientifically minded, this is called a
NEWTON*s and is a measure of momentum - in this case it's a measure of
the change in the momentum of our NEA that we need to make in order to
slow it down enough to orbit the Earth somewhere in the general vicinity
of the ISS).
6) In rocketry they use the term "specific impulse" (Isp). This is a
measure of the change in momentum that a particular rocket engine (using
a given fuel) can produce per unit of propellant used. In this case
we're using kg for units of propellant. The Isp of a rocket engine/fuel
type is usually given in "seconds". Because this term is normally
applied to lifting things from the ground to orbit, the units "seconds"
works or mathematically for the formulas that the "rocket scientists"
use. In our case we need to convert this term to one we can use to
figure out how much fuel we'll need to move our NEA. As it turns out,
one Isp (second)=9.8 N*s/kg (fuel used).
7) The Space Shuttle's main engines (burning LOX and LH2) produce a
specific impulse of about 455 seconds. This is about as good as it gets
for a chemical rocket engine. Ion engines have higher Isp's, but the
only ones we have today produce very low overall thrust. If we plug our
numbers for the Shuttle's main engines into the above formula we have
455*Isp (seconds)=455*9.8 N*s/kg (fuel used). In the case of the Shuttle
main engines, one kg of fuel will give us 4459 N*s change in momentum of
our NEA.
8) Since the change in our NEA's momentum has to be 2.214*10^9 N*s and
our best chemical rocket engine will give us 4.459*10^3 N*s per kg of
fuel we have: kg (fuel)=(2.214*10^9 N*s)/(4.459*10^3 N*s)=about 496,500
kg of fuel. For comparison, the Shuttle external (fuel) tank holds about
735,600 kg of fuel (LOX and LH2) - the specifications for this tank,
according to Wikipedia, are as follows:
SLWT Specifications [3]
* Length: 153.8 ft (46.9 m) * Diameter: 27.6 ft (8.4 m) *
Empty Weight: 58,500 lb (26,500 kg) * Gross Liftoff Weight:
1,680,000 lb (760,000 kg)
9) If we use current technology, we'll have to find some way to loft
nearly 500,000 kg of fuel (plus a rocket engine complete with plumbing
and pumps) into LEO (7.7 km/s) and then accelerate it another 12.3 km/s
to catch up to our 30 m^3 NEA. Then we'll have to use our fuel to
remotely slow down our NEA so that it settles into an orbit somewhere in
the vicinity of the ISS. This is a pretty tall order.
10) A problem that hasn't yet been mentioned - but is critical - is that
we can't see 4 m NEA's until they're on top of us or are past us. We'll
have to vastly improve our tracking and observation capabilities if we
hope to capture one of these things.
11) We could greatly reduce our fuel requirements by using ion drives.
The trade-off is that - with the ion engines we have (or are on the
drawing boards today) - it will literally take many decades to produce
the change in orbital velocity needed for a 180 metric ton NEA. Also,
ion drives need a power source - solar panels or a nuclear reactor - to
produce the electricity needed to accelerate the ions to high
velocities.
>
> Chris
>
> --- In spacesettlers@yahoogroups.com, "brooksn" bhn1700@ wrote:
> >
> > --- In spacesettlers@yahoogroups.com, Matt Gallimore happygallimore@
> wrote:
> > >
> > > 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
--- In spacesettlers@yahoogroups.com, Joe Strout wrote:
>
> On 10/1/10 11:22 AM, brooksn wrote:
>
> > Well we wouldn't attach to the asteroid to move it, we'd station keep
> > 'float' off the asteroid and use the gravity of the spacecraft to nudge
> > the asteroids trajectory. ... The energy requirements would be modest.
>
> Not if you're still talking about capturing an asteroid into Earth
> orbit. We're talking about a 300-ton asteroid that ranges from 0.7 to
> 3.6 AU from the Sun. You're not going to circularize that and match
> Earth orbit just by parking a spacecraft next to it.
> > NASA has already done this.
>
> I wasn't aware that this had ever been done except on paper. Do you
> have more details?
>
> Best,
> - Joe
Sorry I misread the original study, they did do a detailed study on deflecting it.
http://www.b612foundation.org/press/press.html
http://neo.jpl.nasa.gov/neo/b612_report.html
Brooks