Space stations beyond ISS

samy · 2007-10-06 10:52:53

Leaving aside the debate of *whether* we should colonize free-floating space. Let's start this thread with the premise that we *wish* to build some more space stations. Maybe 10 years from now, maybe 100, maybe 1000, doesn't matter. But I just want to explore the possibilities of building habitats somewhere other than on planets, moons or asteroids.

Whenever we get to our civilization's next space station, what should it be like? What is important in the design of a space station? What sort of roles should it fill? What kind of architecture should it go for?

In my opinion, the next space station (heretofore referred to as NSS) should be built with long-term human habitability in mind. We've done the short-stay scientific research station with ISS, and it's time to go for the next step and see whether it's possible to engineer long-term habitability.

Accepting that premise (long-term human habitability) strongly suggests that we should attempt to provide artificial gravity just to be on the safe side, since we do not yet know the effects of long-term lack of gravity on habitability. And if we intend to try to implement artificial gravity, that places lower limits on the station's size. You can only implement artificial gravity on stations that are big enough.

Specifically, the g-force provided is linearly dependent on two variables. The radius of rotation, and the square of the rotations per minute. We could have a very small radius of rotation, but then the RPM (because it grows with square) would have to be insanely high. According to some studies, the highest RPM humans can tolerate long-term is 2 RPM. So if we set that 2 RPM as our parameter, we can calculate the necessary radius to establish 1g of artificial gravity, and the radius turns out to be ~224 meters. We could have a smaller radius, but then we'd have to increase RPM to intolerable levels, or we'd have to do with less than 1g of gravity. Personally, I'd rather we try for the full 1g. So, we end up establishing a lower limit of 224 meters for the radius of rotation for the NSS.

Premise 2: Minimize cost. I want to do the calculations for the very lowest limit possible, and see if the most minimal 1g space station possible is even economically doable. If the most minimal 1g space station is not economically possible, then we'll have to be stuck with things like ISS for the foreseeable future.

Accepting premise 2, cost minimization, means we want to find the shape that has the smallest surface area. The amount of surface area is directly proportional to the amount of metals (for building the superstructure) that we will need to import out of Earth's gravity well (or out of asteroids, or any source, really). The less surface area, the less raw materials we will need to build the superstructure.

To have the same gravity at each point along the walkway inside the station, that walkway will need to be the same distance from the center of rotation, i.e. the livable surface will form a circle around the center of rotation. If we include all the space inside the circle in our space station, we will create a disc-shaped station, with no ceiling. If we looked up, we'd see buildings hanging 2*224 meters above our heads. However, that is a bit of a wasteful design. Doing a torus instead, so that we cut out the center of the disc and leave it open to space, will result in surface area/amount of imported metals reduction of noticeable proportions as follows:

Parameters: Radius of rotation 230 meters. Width of habitat 20 meters.

A disc would have a surface area of 361,283m2 and a volume of 3,323,805m3.

A torus would have a surface area of 90,800m2 and a volume of 454,002m3.

As we can see, if we were to build a disc instead of a torus, we'd have to import 4 times the amount of metal, at 4 times the cost. Building a torus instead of a disc is 75% cheaper.

However, it will be a lot easier to live inside the tube if its cross-section is a square (or rectangle) instead of a circle. It would be fairly difficult to construct buildings when the "ground" isn't level. Try placing furniture in a room whose floor curves noticeably. So in the interests of ergonomy, I'm exploring the possibility of a torus that has a tube cross-section of a square instead of a circle.

A squaroidal torus of the same dimensions as the above would have a surface area of 115,611m2 and a volume of 578,053m3. That's a 27% increase from the circloidal torus. It means a 27% increase in cost. Or, conversely, at the same cost, we could have a livable area width of 15,6 meters as opposed to the 20 meter circloidal width, if we wanted to keep costs the same.

For simplicity of building stuff inside the torus, I am going with a squaroidal cross-section even though it will mean a slightly increased cost (or reduced width). So we've determined the shape the space station should be. It's going to be an approximately 230m radius torus which means 1445m long habitat. You make a morning jog through the hab, when you get back to your starting point, you'll know you've jogged nearly 1.5km. This'll be a more impressive jog distance when we build a 2g space station.

I'm going to refine and minimize the dimensions of the cross-section now. To avoid bumping our heads, we don't need the ceiling to be much higher than 2.5 meters or so. However, we might like to have more headroom than that simply for air circulation and the feeling of openness, to avoid any claustrophobic kinds of feelings. I would personally suggest a ceiling height of 5m -- a nice, good headroom without going nuts with open "sky". But, perhaps, while we're doing an exercise in minimalization, I should tone that down a bit. I'll go with a 3m ceiling.

As for the width of the habitat, I think there needs to be a transit system running through the length of the hab, a "road" as it were. Since the hab will be too small for vehicles of any kind (except perhaps bicycles) this pretty much means the road will take approximately a human's width, perhaps a little more for comfort. Let's give the road a 2m width, that will be enough for one-direction traffic, and enough space to dodge another person as well if they're coming from the opposite direction. So the road alone will require 2m of width for the hab. The rest of the width for the hab is all about the widest item to be included in the station. If the station will have a nuclear reactor 50m wide, then the hab will need to be 52m wide altogether. If the biggest item to be accommodated is a 2m bed, then we could build a hab only 4m wide. I would say that 4m width is probably as small as a hab could be possibly constructed. It would probably require much more, but I'd say 4 is the minimum.

So, now we have a hab that is 4m wide, 3m high to the ceiling, and 1445m long. Now that we know the width, we can calculate that the rotational radius (from center of rotation to center of hab) is 226m (224m to the inner surface of the hab + 2m to the center of hab). With these parameters, let's re-do our calculations.

Rotational radius: 226m
Disc hab width: 4m
Torus hab width: 4m
Rectanguloidal torus hab width: 4m
Rectanguloidal torus hab height: 3m

Disc A = 326,600m2 V = 641,860m3
Torus A = 17,844m2 V = 17,844m3
Rectanguloidal torus A = 19880m2 V = 17040m3

By these figures we can see that by rectangularizing the cross-section of the hab, we increased the surface area, but actually decreased the amount of livable space (volume) from the torus. Compared to the torus, we have 111% the surface area (and thus cost of materials importation) but only 95% the volume. If we were to pull the ceiling down to 2m, we could reduce these figures to 95% and 64% of the torus. If we'd increase the ceiling to 4m (same as width, thus a squaroidal cross-section instead of rectanguloidal) we'd have 127% the area and 127% the volume. 5m ceiling would have 143% the area and 159% the volume. As we can see from these numbers, the higher the ceiling goes, the more dominant the volume becomes. If the hab height is less than width, we have more area than volume. If the hab height is equal to width, area and volume are equal. If the hab height is more than width, then the volume starts to exceed area. In any case, let's move on with the final figures for our hab.

Rotational radius: 226m
Rectanguloidal torus hab width: 4m
Rectanguloidal torus hab height: 3m
Rectanguloidal torus hab length: 1420m
Rectanguloidal torus surface area: 19880m2
Rectanguloidal torus interior volume: 17040m3

For comparison, ISS interior volume is approximately 1000m3, so this would have the interior space of 17 ISSes.

Next, I'm going to calculate the cost of getting the raw materials into GEO. I don't know what kind of material and thickness ISS walls are constructed of, so I could use help to refine those numbers. I have guessed the below numbers:

Wall thickness: 0,01m (10cm)
Wall volume: 0,01m*19880m2 = 199m3
Wall density: 2700kg/m3 (aluminum)
Superstructure mass: 536,760kg

Now, we have a huge torus built, but we still need to fill it with an atmosphere. Let's go with a simple 80/20 N/O mix. So, we multiply the volume by 80% and multiply that with nitrogen density, do the same with oxygen.

Nitrogen mass: 17,054kg
Oxygen mass: 4,870kg

Adding all of those together, we get

Total mass (superstructure + interior atmosphere): 558,684kg
Price to GEO: 20,000$/kg
Price to GEO: 11,173,672,331 $ = approx. 11 billion

And that's just for transporting the raw materials, not including obtaining the raw materials, building them into modules, manpower, or anything else. I could use some help with estimating those figures.

If oriented optimally towards the sun, the station's surfaces would present a 5680m2 catchment area (4m width * 1420 m length) for solar rays. If the entire surface were to be covered with space-rated solar panels (1kg = 1m2 = 300W) it could produce 1.7MW while adding 5680kg to the station weight. (Covering the entire station area, including the central gap, with a disc of solar panels, would produce approx. 49 MW and would weigh 163 tons.) At $2.50/Watt, it would add 4.26 million dollars to the station's cost to include that 1.7MW power plant.

More thoughts to come...

Tom Kalbfus · 2007-10-06 11:17:46

Why not find an asteroid that's 500 meters in diameter and spin it so that it experiences 1g at its extremities. Getting an asteroid into GEO is difficult, but there is an alternative, namely Extreme Elliptical Orbit (EEO). One way to capture a Near Earth Asteroid is to deflect its path so that it encounters the Moon. The Moon's gravitational influence robs the asteroid of some of its incoming velocity enough so that it gets captured into an EEO, the lower portion of which grazes the Earth's atmosphere while the upper portion of which is in the vicintity of the Moon's orbit. The atmospheric grazing slowly lowers the upper portion os the asteroid's orbit so that it is no longer influences by close passes of the Moon's gravity. Afterwards a correction is applied to the asteroid while in the upper portion of its orbit so that the lower portion no longer grazes the Earth's atmosphere. Once securely in Earth's influence the asteroid is spun up for artificial gravity and cavities are excavated for human habitation. The asteroid remains in an EEO as the energy required to circularize the orbit is not justified, EEOs are much more useful than GEOs. One can mine the asteroid for materials and build spaceship's that are launched from EEOs with less energy than would be required from GEOs. If you want to build Solar Powered Satellites, they can be stationed in an Earth synchronious EEO, such that the SPS will appear to move in a stationary epicycle relative to a fixed position on Earth's equator. The SPS will always stay within the line of site of the power receiving station on Earth, but it will appear to move west for a time and then east, get further away and then closer. The SPS will have to aim its microwave beam toward the power receiving station as it orbits in its EEO. The orbital period of the EEO is 24 hours though in its lower portion, the satellite will advance faster than the Earth rotates and in it upper portion it loses ground to Earth's spin.

Terraformer · 2007-10-06 11:36:10

The next station should be a Shipyard. Maybe having a big zero gravity construction area and hanger where the airlock would be. At each end of the cylindar would be spokes sticking out with the habs on. The radius of the cylindar, plus the spoke length, plus the hab height, would have to add up to 224 metres. The parts would all be launched unmanned so only one mission is needed for actual construction, another for all the resources. Airlocks would be placed in between each hab incase of puncture by meteroids and other debris. Also, if the oxygen is going down and no shipment can be scrambled, that area can be blocked off to live in until a ship arrives.

samy · 2007-10-06 11:40:28

It would definitely be interesting to try out some robotic mining techniques. I think hollowing out an asteroid would have to be done by robots and not by humans in very bulky and very vulnerable to damage space suits. What do you think?

What kind of energy would be required to spin up a d=500m asteroid? Let's take Golevkaas an exercise.

Golevka m = 2.1E11 kg
Radius r ~= 300m

One rocket to a point on the surface, to produce tangential thrust. Another rocket to the opposite point on the surface, to produce tangential thrust in the opposite direction. How powerful would the rockets need to be to make it do 2rpm?

First we need to calculate the target rotational energy

Erot = 0.5Iw2 = 0.5 * 0.4mr2 * w2

m = 2.1E11 kg
r = 300m
w = 2 rpm = 4pi rad / 60 sec = 1/15 pi rad/sec

Erot = 1.66E14 J = 166 000 GJ

P = 1GW power plant

t = E/P = 166 000 GJ / 1 GW = 166 000 sec =~ 1,92d

So, if my calculations are correct, a 1GW power plant could set up that rotational speed in two days. A 10MW solar array could power the sufficient rotation in 192 days, less than a year. Are my calcs in the right ballpark?

Tom Kalbfus · 2007-10-06 14:51:02

At a casual glance, it looks ok. Golevka is an interesting object, it looks lumpy, perhaps thats a good sign, we'd want it to be a solid chunk of rock, not a roundish pile of rubble, so that it holds itself together with spin.

Now an Extremely Elliptical Synchronius Orbit has an advantage, its easier to capture an asteroid into this orbit and its easier to send an asteroid like this out of Earth's orbit. If you wanted to, you could use the engines to send the asteroid on another Lunar encounter to fling it on a Mars ward Trajectory, and then you'd need to use the engines again to slow it down so that Mars would capture it. An asteroid such as this would also be suitable for a manned Jupiter mission, you'd need am asteroid with a nice thick rind to shield the crew from the lethal van Allen belts of Jupiter. A rotating habitat is advisable for interplanetary voyages beyond Mars, although you might get by without one on a trip to Mars.

samy · 2007-10-06 15:45:08

Interestingly, wouldn't spinning an asteroid automatically tend to form it into a more round shape?

Namely, if I understand the nature of rotation correctly, the furthest extremities of the asteroid would feel the most severe g-forces and thus be the most likely ones to break away? If there was a high "spike" on an asteroid for example, its tip would feel pretty strong g-forces and try to tear away, thus rounding the asteroid when it pulls free. So spin an asteroid fast enough and it'll "shake loose" its bigger extremities for a more roundish shape.

It might even be a good idea to take an asteroid to higher RPMs for a while before settling, just to "shake off" any matter that's risk-prone and might collapse during the coming centuries. If we need 2 RPM, maybe we could take the asteroid to 4-5 RPM for a little while first, to "shake off" all the unstable matter, then bring it back down to 2 RPM and we should have a pretty stable core left.

If I understand rotation correctly.

(Of course, this would only be sensible for fairly small objects. For bigger objects, doing some excess RPM would be fairly energy-hungry.)

Tom Kalbfus · 2007-10-06 15:54:48

Interestingly, wouldn't spinning an asteroid automatically tend to form it into a more round shape?
Namely, if I understand the nature of rotation correctly, the furthest extremities of the asteroid would feel the most severe g-forces and thus be the most likely ones to break away? If there was a high "spike" on an asteroid for example, its tip would feel pretty strong g-forces and try to tear away, thus rounding the asteroid when it pulls free. So spin an asteroid fast enough and it'll "shake loose" its bigger extremities for a more roundish shape.
It might even be a good idea to take an asteroid to higher RPMs for a while before settling, just to "shake off" any matter that's risk-prone and might collapse during the coming centuries. If we need 2 RPM, maybe we could take the asteroid to 4-5 RPM for a little while first, to "shake off" all the unstable matter, then bring it back down to 2 RPM and we should have a pretty stable core left.
If I understand rotation correctly.
(Of course, this would only be sensible for fairly small objects. For bigger objects, doing some excess RPM would be fairly energy-hungry.)

You know, some asteroids might already be spinning that fast already. If two asteroids collide, the result might include a fragment thats spinning quite rapidly and experiencing negative gs on its extremities, but if the fragment is solid, there's no reason why it should continue to spin this fast, the result is similar to a stalagtite hanging from the ceiling of a cave. A solid rock doesn't need gravity to hold itself together and if there's nothing to slow its spin in a vacuum, we might just find a pre-spun asteroid. Of course changing the orbit of such an asteroid might prove to be a little more difficult.

samy · 2007-10-06 16:06:29

An excellent point. Not having to spin up an asteroid would save a lot of energy that could be used on other things instead. It would make a LOT of sense to look for a 300m asteroid that spins at 2RPM, or a larger asteroid that spins more slowly than that. Considering how many asteroids there are, odds are there have to be some that fit the profile.

While I'm here, what are the advantages of colonizing an asteroid as opposed to a comet?

I'm given to understand that comets are much richer in ices and other volatiles, so wouldn't they be more promising locations?

samy · 2007-10-06 18:38:35

Going back to my little thought experiment, the NSS Enterprise:

We've got a 3m high x 4 m wide x 1420 m long living space filled with 80N/20O. We can breathe there, but not for long. The next step is thinking about the life support systems.

In BIOS-3 the Russians managed to keep O and CO2 in balance with Chlorella algae -- 8m2 per inhabitant. So if we covered the entire 4x1420 m2 floor with Chlorella, that's 5680m2 of exposed algae which can support 710 people breathing in and out indefinitely. Unless we can find a better CO2->O mechanism, the absolute upper limit of the station's personnel is 710 people, and they would need to be wading in algae 100% of the time. So, having less people and dedicating less space to algae would be desirable. Let's also remember that fully 50% of the station's floor space is tied up in the 2m wide sidewalk running through the station.

One potential idea might be to double-use the sidewalk space. Have algae mats, and then right above them grating which would serve as the sidewalk area. Basically, the sidewalk would be 10-20 cm above the algae mats. Having the sidewalk consist of grating instead of solid would allow the atmosphere into more or less unhindered contact with the algae mats under the sidewalk. Forget red carpets, NSS has green carpets to walk on!

Dual-using the space under the sidewalks gives us a 2x1420m algae growth, which can support 355 people. For that matter, why not make the entire station's flooring grating-on-top-of-algae-pool? Living quarters and everything with algae underneath. That'd give us the previously calculated 710 people max. However, we probably won't even be able to fit even 355 people on the station, so it might be pushing it to have algae carpeting everywhere. We just don't need that much CO2 processing power.

The CO2->O problem is thus fairly trivially solved as long as our station numbers in the hundreds and not in the thousands.

Next up, food and water...

Martian Republic · 2007-10-06 18:46:26

An excellent point. Not having to spin up an asteroid would save a lot of energy that could be used on other things instead. It would make a LOT of sense to look for a 300m asteroid that spins at 2RPM, or a larger asteroid that spins more slowly than that. Considering how many asteroids there are, odds are there have to be some that fit the profile.
While I'm here, what are the advantages of colonizing an asteroid as opposed to a comet?
I'm given to understand that comets are much richer in ices and other volatiles, so wouldn't they be more promising locations?

An asteroid has an elongated orbit that we could get to once we develop something like fusion rockets on a timely bases.

Comets go away for a long time like Hallie's Comet does for eighty years or so and doesn't stay in the inner solar system for more than a few months. So you would have to catch it and have resource for eighty years until Hallie's comet come back around. So you would have to change the orbit of those orbits of the comet that you wanted to colonize. Which is not very likely, because it would take too much energy to redirect that comet to the orbit that you want it to go in.

Larry,

samy · 2007-10-06 18:57:57

Not all comets have such long periods. For example

http://en.wikipedia.org/wiki/Comet_Encke

Period 3.30a
Aphelion 4.11 AU

Stays pretty well in the inner solar system and crosses Earth orbit twice in 3.30 years. Hopefully it's not the only short-period comet.

samy · 2007-10-06 19:21:56

Water

http://science.nasa.gov/headlines/y2006/30oct_eclss.htm

In Iraq they're testing a "refrigerator sized unit" which purifies 4 gallons per minute. If we assume that 4 gallons is enough for one person's drinking water needs per day, then that unit would be enough for 1440 people. Like oxygen, drinking water appears trivial as long as we are talking hundreds and not thousands of inhabitants.

Shower and industrial water is, of course, a different issue altogether, but we can consider them a luxury and think about them later, until we've resolved all issues with the absolute necessities first.

Food

http://newmars.com/forums/viewtopic.php?t=229

Estimates for required area for food production range from 50-80 m2 per person. Even if we made the entire station a huge farmland, its 5680m2 would still only feed 71 people (who would not have any room to sleep because the entire station is farm).

So food production is the real chokepoint. Scrubbing air and water of impurities is comparatively trivial, but food production is what will restrict the amount of people we can cram onto a space station.

With half the station's area taken up by the sidewalks anyhow, we're talking 30 people if the entire remaining area were farmland. And because we want some room for other things on the station than farmland, too, let's say we could have 10-20 people permanently living on a closed environment 3x4x1420 m3 in size.

Terraformer · 2007-10-07 03:09:14

Am I talking to myself? What about a shipyard that could construct other stations and ships. If you are talking about moving my asteroids then you obviusly have identified the resource for the ships & stations.

samy · 2007-10-07 07:51:30

I don't know if a shipyard, specifically, but in general I agree that what we really need in space is a minerals processing plant. A place that can take lunar rock and asteroid rock and refine it into its component elements. Also, a mining/cargo ship. Those are the two things we need really badly to be our first steps. Having those two would reduce costs of future space endeavors drastically because we wouldn't need to import every ton of material from Earth.

Tom Kalbfus · 2007-10-07 08:09:57

Am I talking to myself? What about a shipyard that could construct other stations and ships. If you are talking about moving my asteroids then you obviusly have identified the resource for the ships & stations.

I think building a space station from the material extracted from an asteroid, might be harder than building a space station out of an asteroid, because with an asteroid, you can start small, you can excavate a tunnel and bury a manufactured pressurized module within the asteroid's crust, and if the asteroid has the right spin, you'd also have pseudogravity. If you wanted to manufacture an entire spinning space station out of an asteroid while forgoing the stucture of that asteroid as you base, your going to have to do materials processing in space, and to conserve materials you tend to build thin walls leaving less protection from cosmic rays. Also there is a minimum size for rotating space stations, your going to have to build the whole thing and spin it up before moving in.

Otherwise larger space stations would probably hold themselves together better than asteroids if spun up, we're talking about Island Threes here. If you want to approach anywhere near the material limits of the structure, its better to work with manufactured materials than asteroid rinds.

publiusr · 2007-11-09 14:29:35

Asteroid mission images--from the past.

http://forum.nasaspaceflight.com/forums … 21&start=1

JoshNH4H · 2007-12-24 15:34:21

acce4pting premise 2, wouldn't say, 1/2 g, or mars g be better?

samy · 2007-12-24 16:27:35

acce4pting premise 2, wouldn't say, 1/2 g, or mars g be better?

I don't see that it is. If we intend to provide non-Earth gravity, I think heavier gravity (forcing greater exertion and keeping us in better health) would be better than lighter gravity (allowing us to slack and develop cardiovascular diseases).

JoshNH4H · 2007-12-24 19:27:50

also, lighter gravity would allow lighter materials. Remember that the hull materials need to go from (presumably) ~650 mb to 0 mb, and support their own weight.

JoshNH4H · 2007-12-25 07:28:18

Not to mention that, as you have stated multiple times, this is an excercize in minimalization. As such, smallest gee is lower cost, not to mention, you could make the station wider. this gives more space to grow the food, which you have explained, is the chokepoint. BTW, where did you get your figures for the amt. of m^2 /person (foodwise)

dicktice · 2007-12-25 14:04:55

This is a very interesting topic, but I'm confused. Is it about space stations orbiting Earth, or space colonies orbiting the sun?

A "shipyard" LEO, for the general purpose of gathering and/or assembling elements of projected interplanetary space expeditions, would be an exclusively near-earth exercise. On the other hand, proposing to place asteroid materials (or the asteroid itself!) in LEO would involve such a risk to the home planet as not to be taken seriously.

The LEO shipyard facilityprobably should comprise the next space platform, made up (say) of inflatable modules launched as needed from Earth. One of the initial "ships" to be assembled might even be become first LEO habitat.

But, to construct a habitat within a hollowed-out asteroid orbiting the sun, would involve interplanetary logistics a level of expertise at least a generation beyond our present capabilities in LEO.

But, what if a suitable asteroid's orbit around the sun could be made phase-synchronous with that of Earth? The trick as I see it, would (1) incline the hypothetical near-Earth asteroid's orbital plane a few degrees above and below Earth's and (2) reshape it to be a bit more eliptical so as to avoid risk of collision but have the same period as Eath's. Once the phase-synchronism has been established, year-round space travel would then be feasible to-and-from the space colony as easily and often as between the moon and Earth.

Terraformer · 2007-12-25 14:30:21

Of course, we could just alter the ISS to turn it into a shipyard without much effort. We might even be able to get it to the stage where it enlarges itself.

dicktice · 2007-12-29 11:54:21

I sure would like to know if the suggestion I made (two posts back) that phase-synchronization between Earth and a space colony circling the sun would be possible by elongating its orbit to pass both inside and outside Earth's, after tilting it's plane to avoid crossing collisions, in order to maintain the same period as Earth?

noosfractal · 2007-12-29 13:54:23

I sure would like to know if the suggestion I made (two posts back) that phase-synchronization between Earth and a space colony circling the sun would be possible by elongating its orbit to pass both inside and outside Earth's, after tilting it's plane to avoid crossing collisions, in order to maintain the same period as Earth?

You can have an elliptical orbit with the same period as the Earth's, but your asteroid/space station would tend to become another moon unless you locate it at one of the Earth-Sun Lagrange points (which, of course, orbit the Sun with approx. the same period as the Earth).

http://en.wikipedia.org/wiki/Lagrangian_point

Home, home on Lagrange,
etc

dicktice · 2007-12-29 18:56:38

Well, I should've thought of the Earth-Sun Lagrange points myself. But having approached the delimma intuitively as an objection to treating LEO and (solar orbiting) asteroid access to construction materials similarly, I got carried away. Still, if one is willing to actively control the hypothetical asteroid colony in order to maintain a distance roughly a week or two away from Earth, and by inclining and elongating the orbit around the Sun to match our period of one year, wouldn't this be handy expedient during the construction phase?

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