Phoenix Lander Preparing For Martian Touchdown

[FSTargetDrone]

Of course, that is NASA and ESA working on and over Mars.

[FSTargetDrone]

Sorry for the 3rd post in a row, but I had to share what I just found today:

05.27.08

Phoenix Descending with Crater in the Background



Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE) camera acquired this image of Phoenix hanging from its parachute as it descended to the Martian surface. Shown here is a 10 kilometer (6 mile) diameter crater informally called "Heimdall," and an improved full-resolution image of the parachute and lander. Although it appears that Phoenix is descending into the crater, it is actually about 20 kilometers (about 12 miles) in front of the crater.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

NASA/JPL-Caltech/University of Arizona

A larger image is available here.

Do check out the larger image. It's really something.

Oh, and there is a nice animation of the lander's entry and landing at the mission site, but there's a streaming version of it here.

[Junghalli]

I kind of see Commander 598's point: exploring for the sake of exploration is all well and good but if we really want to start establishing a serious presence in space asteroid mining is the way to go.

The two aren't mutually exclusive: this kind of exploration would be a lot cheaper and easier if we didn't have to drag everything out of Earth's gravity well.

[Broomstick]

I believe part of the problem is that we don't feel as though we're doing anything or are doing the wrong thing. In my book Mars is basically useless and it's a waste of time, money, and effort to try and do much of anything with it's a pretty shitty place all around.

Mars may be shitty in one sense, but it's actually much more hospitable that most of the solar system.

Besides which - if we can safely and reliably get to and from Mars than doing so closer to Earth will not be such a problem.

Working out ways to mine near Earth asteroids and/or the moon, perhaps making space a bit more of a profitable venture to invest in, would be a more preferable use of money.

One big problem with long-term living in space is water. If we find water on either the Moon or Mars then the feasibility of living there long term goes up considerably.

[FSTargetDrone]

One big problem with long-term living in space is water. If we find water on either the Moon or Mars then the feasibility of living there long term goes up considerably.

On a slightly-related note, the toilet on the ISS is malfunctioning and I read elsewhere that an eventual upgraded toilet is supposed to be a system that recycles the liquid waste for potable use, evidently.

Toilet breaks at International Space Station

3 hours ago

WASHINGTON (AFP) — It's bad enough when the toilet gets clogged at home; it could be a lot more serious in space, especially with visitors on the way.

NASA said Wednesday that the liquid waste handling function of the toilet at the International Space Station (ISS) had malfunctioned the day before and that the three astronauts aboard had to use the toilet at the Soyuz capsule moored at the station.

Eventually the two Russians and one American at the orbiting station were able to fix up a "urine bypass" on the ISS toilet, located on the Zvezda module, the National Aeronautics and Space Administration said.

NASA spokeswoman Nicole Cloutier told AFP that the space shuttle Discovery, scheduled to arrive at the ISS Monday with seven astronauts aboard, would be carrying toilet parts to help repair the station's prickly plumbing.

"It's not really an emergency, they have many options available if they need," Cloutier said from the Johnson Space Center in Texas.

"There is another toilet ready to fly in the fall, in order to have two toilets on board for when they'll have the expanded crew of six" at the ISS, she said.

"There also other devices if they really need to ...kinds of bags," she added.

Water is heavy! The less they have to carry up, the better.

[Commander 598]

Water is an important factor, and basically the only use I see for Mars since Mars has relatively low gravity and the nearest actual ice moon is around Jupiter, assuming there isn't any ice on our moon or to be found in the asteroids we would be mining or that it wouldn't end up being cheaper to just stop off at Europa when we go/figure out how to mine the Helium out of Jupiter.

[Junghalli]

IIRC there is water on the Moon (frozen in shadowed craters) and probably water (again, frozen) on some of the near-Earth asteroids. NEAs that are burned-out comets are especially interesting in this regard. It would be more practical to get it from there than from Mars.

From an economics viewpoint Mars is pretty much useless except as a tourist trap. The NEAs and the Moon are useful because we can extract resources from them and put them in orbit potentially much more cheaply than we can put stuff from Earth in orbit, which is pretty useful for sattelites and other space-based infrastructure. Mars is farther away and has a deep gravity well; we're very unlikely to be extracting resources from it.

From a scientific viewpoint Mars is pretty interesting, of course, what with having once had liquid water and all.

[Broomstick]

Water is an important factor, and basically the only use I see for Mars since Mars has relatively low gravity

The Moon has even lower gravity, and asteroids have even less. What does gravity have to do with it?

Mars has potential uses as a colony. Granted, that's long way down the road, and terraforming even further, but there are folks who sincerely believe that setting up an independent colony on another planet makes good sense long term for the species.

I don't know what mineral resources Mars has, but if it has significant water to go with its atmosphere (granted, it's not much of an atmosphere by our standards, but it does exist) and additional mineral resources then that's a hell of a lot less we need to bring with us for a colony. That's not minerals we'd mine and send to Earth, that's stuff we don't have to bring from Earth.

There's also the problem that distances in space are vast, and it's not healthy to lock people into confined spaces indefinitely. A Mars colony could be larger than a spaceship or asteroid mining installation and, depending on where you are, might be easier to get to than Earth at times. If people are going to go into space - debatable at this point - then having a way station on Mars might make a lot of sense from a psychological viewpoint. It might have re-supply ability on at least some items, including fresh food if greenhouses of some sort can be set up. Lifting food from Mars will be cheaper than lifting it from Earth because of that weak gravity well.

And, of course, if there is life on Mars, or was, then studying it could be extremely important from a scientific viewpoint. But if we never look we'll never know.

Meanwhile, everything we learn about making remote probes and rovers, and landing things remotely on another planet, can be applied to mining those asteroids you are so fond of. Any mine in space is going to rely heavily on robots and remotes. So maybe Mars isn't terribly sexy or useful to you, but that doesn't mean exploring it won't have positive repercussions for what you want to do.

[Master of Cards]

If you wanted to set up a supply base why not put it in the asterriot belt? Ceres would be more then massive enough for a large base.

[Commander 598]

Water is an important factor, and basically the only use I see for Mars since Mars has relatively low gravity

The Moon has even lower gravity, and asteroids have even less. What does gravity have to do with it?

Money? Less gravity = less fuel to get out of the gravity well = less money. The going rate of getting things off of Earth is rather pricey...

Mars has potential uses as a colony. Granted, that's long way down the road, and terraforming even further, but there are folks who sincerely believe that setting up an independent colony on another planet makes good sense long term for the species.

I think you fail at space colonization. HINT: Colonizing a planet with less than preferable weather conditions that requires terraforming technology that we don't have and won't have for quite some time as well as having noteworthy amounts of gravity is...dumb.

I don't know what mineral resources Mars has, but if it has significant water to go with its atmosphere (granted, it's not much of an atmosphere by our standards, but it does exist) and additional mineral resources then that's a hell of a lot less we need to bring with us for a colony. That's not minerals we'd mine and send to Earth, that's stuff we don't have to bring from Earth.

Who said anything about sending it to Earth? You use the orbitally mined material to construct things in space.

A Mars colony could be larger than a spaceship or asteroid mining installation...

Not necessarily.

And, of course, if there is life on Mars, or was, then studying it could be extremely important from a scientific viewpoint. But if we never look we'll never know.

I think many people have their priorities mixed up... I believe the "searching for life" is more sanely done AFTER you have some sort of infrastructure. It's kind of like exploring the Louisiana Purchase while having never set up any sort of "base" in America.

[Guardsman Bass]

Water is an important factor, and basically the only use I see for Mars since Mars has relatively low gravity

The Moon has even lower gravity, and asteroids have even less. What does gravity have to do with it?

Money? Less gravity = less fuel to get out of the gravity well = less money. The going rate of getting things off of Earth is rather pricey...

What does that have to do with space colonization? If you are setting up a permanent colony on another world, decent gravity can actually be your friend. Low gravity like on an asteroid or the moon is only helpful if you are planning on sending regular shipments of people and material around.

Mars has potential uses as a colony. Granted, that's long way down the road, and terraforming even further, but there are folks who sincerely believe that setting up an independent colony on another planet makes good sense long term for the species.

I think you fail at space colonization. HINT: Colonizing a planet with less than preferable weather conditions that requires terraforming technology that we don't have and won't have for quite some time as well as having noteworthy amounts of gravity is...dumb. [/quote]

Who said anything about terraforming Mars? You don't actually have to - if Mars has water, in ice or liquid form (and it probably does), then you could build a self-sustaining colony on it, without having to import everything (including liquid water) if you colonized the moon or a near earth asteroid.

That said, you could probably do the very basics of terraforming quite easily, if you have some genetic engineering technology - like planting certain kinds of organisms.

I don't know what mineral resources Mars has, but if it has significant water to go with its atmosphere (granted, it's not much of an atmosphere by our standards, but it does exist) and additional mineral resources then that's a hell of a lot less we need to bring with us for a colony. That's not minerals we'd mine and send to Earth, that's stuff we don't have to bring from Earth.

Who said anything about sending it to Earth? You use the orbitally mined material to construct things in space. [/quote]

What does that have to do with setting up a permanent colony?

A Mars colony could be larger than a spaceship or asteroid mining installation...

Not necessarily. [/quote]

I'd love to hear your reasoning on this, especially since on this hypothetical Mars colony, you have access to local supplies of water ice as opposed to bringing it from earth or farther out in the solar system.

And, of course, if there is life on Mars, or was, then studying it could be extremely important from a scientific viewpoint. But if we never look we'll never know.

I think many people have their priorities mixed up... I believe the "searching for life" is more sanely done AFTER you have some sort of infrastructure. It's kind of like exploring the Louisiana Purchase while having never set up any sort of "base" in America.[/quote]

I actually don't disagree on this.

[Junghalli]

Colonies in Earth's orbitals supported by asteroid mines would make much more economic sense than colonies on Mars.

Setting up infrastructure in the orbitals actually makes economic sense, because it's actually useful to investors on Earth. Earth is heavily reliant on sattelites for communications and other good stuff. If we had industry in orbit we could build our sattelites there instead of on Earth, which means we could build them more cheaply, make them bigger, and keep them up a lot longer because we'd be able to supply them with fresh stationkeeping propellant when they ran out much more economically. You could set up giant antenna farms in orbit with much better performance than present communication sattelites, and things like space-based solar power (which is much more reliable than solar power on Earth's surface) would become practical. This would, of course, all be made possible by getting our resources from asteroids and the Moon which have shallow to nonexistant gravity wells and no atmosphere to complicate things, as opposed to Earth which sits at the bottom of a deep gravity well and atmosphere. You could potentially make good money investing in industry in orbit, and asteroid and lunar mines to support it. Colonization would flow naturally from industrialization, especially once we've got a space elevator up, which of course is another potentially very profitable project that will be a lot easier if we already have the orbitals at least somewhat industrialized.

I recommend the PERMANENT website as good reading on this subject.

By contrast, pretty much the only reason to establish a colony on Mars is scientific research and "because it's there". You're not going to be doing resource extraction from Mars because it sits at the bottom of a deep gravity well so it doesn't make much sense. Pretty much the only money-making venture I can think of for Mars is space tourism, and that's not going to happen until we're using more fuel-efficient rockets that can get there in a reasonable space of time (i.e. not for a while).

I know which one I'd be more inclined to sink money into if I was an investor. The one that I'm likely to actually see positive monetary returns from.

Of course, colonizing Mars will also be much easier if we industrialize the orbitals first. It will be much cheaper to build the large Mars exploration and colony ships in space from asteroid material than in space from Earth material.

Once you have decent infrastructure up there's no reason you couldn't support huge colonies in the Earth orbitals and Lagrange points. In fact I expect that to be the solar system's biggest population center, aside from Earth itself, because it's where it would make sense to put colonies.

In terms of economics orbital colonies and asteroid mines do make much more sense than Mars colonies.

[Broomstick]

The Moon has even lower gravity, and asteroids have even less. What does gravity have to do with it?

Money? Less gravity = less fuel to get out of the gravity well = less money. The going rate of getting things off of Earth is rather pricey...

What does that have to do with space colonization? If you are setting up a permanent colony on another world, decent gravity can actually be your friend. Low gravity like on an asteroid or the moon is only helpful if you are planning on sending regular shipments of people and material around.

The other problem is that microgravity is unhealthy for people long-term, at it's questionable how much we can mitigate that. People may need some significant gravity long-term in order to remain fit. If 1/3 g is sufficient then having people recuperate or vacation on Mars might make more sense than shipping them to/from Earth.

A disadvantage of an asteroid colony is that you have to import almost EVERYTHING - Mars has local resources that you won't have to ship from elsewhere, and that saves you money. If you can grow food on Mars (in an enclosed environment for the foreseeable future) it will cost less money to supply more distant outposts from there than from Earth. To some extent, this also depends on just how practical doing the same on the Moon would be, but Mars has a day/night cycle somewhat close to Earth's and the temperatures, although extreme by Earth standards, are not quite so extreme as the Moon. It may be cheaper to grow food on Mars than on the Moon, and cheaper to ship it from Mars to other outposts than to ship it from Earth.

Mars has potential uses as a colony. Granted, that's long way down the road, and terraforming even further, but there are folks who sincerely believe that setting up an independent colony on another planet makes good sense long term for the species.

I think you fail at space colonization. HINT: Colonizing a planet with less than preferable weather conditions that requires terraforming technology that we don't have and won't have for quite some time as well as having noteworthy amounts of gravity is...dumb.

And empty space/asteroids have MORE favorable weather? They don't even have an atmosphere! There would be NO moderation of deep space temperature extremes.

Nor do you have to terraform an entire planet to grow food - you do need an enclosed area with Earthlike conditions but that is doable with our present technology.

Also, there is the problem of radiation in space. On Mars it would be easy to dig down underground to use dirt/soil as shielding. Not so easy on a small asteroid.

And the gravity is ONLY a problem if you need to take something off-world. What would you take from Mars you couldn't get from asteroid mines? Food - IF it's practical to grow food on Mars then resupplying colonies from Mars would be cheaper than from Earth because it has less gravity to overcome. Mars has carbon dioxide, water, and sunlight - with proper soil formation that's all you need for food. As a bonus, you won't have the parasites, diseases, and vermin you do on Earth that reduces crop yields.

Once set up, a Mars colony could be self-sufficient for water, atmosphere, and food - which are three HUGE costs of space habitats. That's stuff you don't have to bring in from anywhere else, and that you can use to manufacture the stuff squishy humans need for fuel.

I don't know what mineral resources Mars has, but if it has significant water to go with its atmosphere (granted, it's not much of an atmosphere by our standards, but it does exist) and additional mineral resources then that's a hell of a lot less we need to bring with us for a colony. That's not minerals we'd mine and send to Earth, that's stuff we don't have to bring from Earth.

Who said anything about sending it to Earth? You use the orbitally mined material to construct things in space.

So... how you going to "construct" food in space, hmm? People gotta eat.

A Mars colony could be larger than a spaceship or asteroid mining installation...

Not necessarily.

That's reaching, dude - city-sized space outposts are quite a ways in the future.

And, of course, if there is life on Mars, or was, then studying it could be extremely important from a scientific viewpoint. But if we never look we'll never know.

I think many people have their priorities mixed up... I believe the "searching for life" is more sanely done AFTER you have some sort of infrastructure. It's kind of like exploring the Louisiana Purchase while having never set up any sort of "base" in America.

You are, of course, entitled to your opinion. I would like to point out, however, that the initial European explorers of the Americas did exactly that - particularly the Spanish who landed ships then went on considerable exploratory expeditions. OK, conquering expeditions, but it is an exploratory style that has worked in the past.

Nevermind that quite a few of the current Mars probes, while solving navigational, descent, telepresence and other problems have combined those with a search for life. It IS possible to have multiple goals and objectives.

Colonies in Earth's orbitals supported by asteroid mines would make much more economic sense than colonies on Mars.

What if the Mars colonies are self-supporting? What if they can supply food, air, and water to outlying installations, thereby cutting down on shipping costs from the Earth-Moon system?

Keep in mind, too, that as things currently stand EVERYTHING must be brought to a Moon colony, AND it has a gravity well -- I've seen arguments that we should bypass the Moon entirely as it has the resource lack of deep space and significant gravity - why not just build in space where you don't have to boost out of 1/6 g?

Colonization would flow naturally from industrialization, especially once we've got a space elevator up, which of course is another potentially very profitable project

Potentially profitable IF it is even possible. What the hell do you build a space elevator out of? Do we even have such a material? Is it practical to manufacture in sufficient quantities to the required standard?

By contrast, pretty much the only reason to establish a colony on Mars is scientific research and "because it's there". You're not going to be doing resource extraction from Mars because it sits at the bottom of a deep gravity well so it doesn't make much sense. Pretty much the only money-making venture I can think of for Mars is space tourism, and that's not going to happen until we're using more fuel-efficient rockets that can get there in a reasonable space of time (i.e. not for a while).

I can actually think of two reasons to colonize Mars that have nothing to do with either mineral extraction or the search for life:

1) Telepresence. I'm really surprised no one else has mentioned this. Right now, there's what, a 10-15 minute time lag between Earth and Mars? With the recent Phoenix probe it went from descent to touchdown before the first signal of "entering atmosphere" even reached Earth. Obviously, we build some autonomy into our machines but the greater the distance the more complicated this becomes, the further you have to think in advance, the more difference dealing with problems becomes... An outpost on Mars is another potential telepresence site, one that may be more convenient to certain far-flung outposts than Earth (there's a complicated stuff happening with orbits, too, but I assume everyone here can figure that out).

2) Food/air/water/etc. Assuming we continue to push further and further out. Assuming a self-sustaining Mars colony can grow surplus food, it may be cheaper/easier/quicker to ship from Mars than from Earth for at least some outposts and circumstances. Air and water might be mined from asteroids, but food has to be grown. In theory we could set up microgravity habitats just to grow food, but in theory we could also farm on Mars. If there is already soil, water, carbon dioxide, and sunlight on Mars the only thing we need to import is seeds and knowhow. If we build a greenhouse in orbit we need to import everything, whether we get it from Earth, the Moon, or asteroids.

Once you have decent infrastructure up there's no reason you couldn't support huge colonies in the Earth orbitals and Lagrange points.

Yes once you have the infrastructure, which includes food, water, and air to keep people alive.

In terms of economics orbital colonies and asteroid mines do make much more sense than Mars colonies.

To begin with I am inclined to agree BUT long term I think we'll find Mars quite useful, despite the gravity issues.

[Junghalli]

What if the Mars colonies are self-supporting? What if they can supply food, air, and water to outlying installations, thereby cutting down on shipping costs from the Earth-Moon system?

Maximal in-situ resource utilization is certainly vital to any kind of serious presence in space. You still have to establish the colony though, which costs money. If I were an investor I'd be more inclined to invest in an asteroid mine, because it's possible I can actually make a profit out of it, as opposed to "well, if we can make it self-supporting it'll stop being a drain on me".

I doubt we'd be using Mars as a resource extraction point. It sits at the bottom of a fairly deep gravity well, and C-type asteroids are probably richer in resources to boot. If you want a resupply depot in the outer system a main belt asteroid or a Jovian moon makes more sense.

Keep in mind, too, that as things currently stand EVERYTHING must be brought to a Moon colony, AND it has a gravity well -- I've seen arguments that we should bypass the Moon entirely as it has the resource lack of deep space and significant gravity - why not just build in space where you don't have to boost out of 1/6 g?

Indeed I think the near-Earth asteroids, not the Moon, are where we'd be getting most of our space resources from. The Moon is mostly dry and mineral-poor, I've read sites that compared its rock to the slag of terrestrial mining operations. Asteroids on the other hand should be quite mineral rich (as they've never experienced the gravitational differentiation that's locked most of the terrestrial planets' metal away in their cores), and at least some of them should have some frozen subsurface volatiles (burned-out comets are especially interesting in this respect).

You're right that in the short-term a Moon colony would not be self-sufficient but if we are to seriously explore space the paradigm of bringing resources from Earth must change. Earth is a spectacularly uneconomical resource base for space colonies (although with a space elevator it may not be so bad).

Potentially profitable IF it is even possible. What the hell do you build a space elevator out of? Do we even have such a material? Is it practical to manufacture in sufficient quantities to the required standard?

A space elevator would probably have to be built of carbon nanotubes. It is not possible to build an Earth-GEO space elevator today, but it should be feasible eventually. Most of the estimates I have read say it may be feasible in 50 years. In the mean time, the fact that everything from Earth has to be dragged out of our deep gravity well with chemical rockets only increases the potential usefulness of an orbit-asteroid based industrial complex.

I can actually think of two reasons to colonize Mars that have nothing to do with either mineral extraction or the search for life:

1) Telepresence. I'm really surprised no one else has mentioned this. Right now, there's what, a 10-15 minute time lag between Earth and Mars? With the recent Phoenix probe it went from descent to touchdown before the first signal of "entering atmosphere" even reached Earth. Obviously, we build some autonomy into our machines but the greater the distance the more complicated this becomes, the further you have to think in advance, the more difference dealing with problems becomes... An outpost on Mars is another potential telepresence site, one that may be more convenient to certain far-flung outposts than Earth (there's a complicated stuff happening with orbits, too, but I assume everyone here can figure that out).

True. One could probably use one of the main belt or Apollo asteroids for this as well, but I can see this.

2) Food/air/water/etc. Assuming we continue to push further and further out. Assuming a self-sustaining Mars colony can grow surplus food, it may be cheaper/easier/quicker to ship from Mars than from Earth for at least some outposts and circumstances. Air and water might be mined from asteroids, but food has to be grown. In theory we could set up microgravity habitats just to grow food, but in theory we could also farm on Mars.

I think it would probably be a better idea for distant outposts to have closed ecologies; shipping food across interplanetary distances is just massively uneconomical. An algae farm is probably easiest, though algae has some problems with high nucleic acids and low vitamin C, but hopefully these could be solved with a little genetic engineering.

Anyway, yes we could grow food on Mars, but we could also do it on the Moon or in orbital habitats using lunar regolith (IIRC NASA did experiments with growing plants in the stuff). Given that most of the space-based population would logically be in Earth orbitals I think having the farms in that area would make more sense. You'd want to have the farms close to the big industrial cities, not on some distant planet half an AU away.

It's true that with orbital habitats you have to import all your construction materials, but a mass driver, scoopship, and rotorvator system should be able to transport quite large quantities of asteroidal and lunar materials into the desired orbits fairly cheaply, so I don't see it as a huge problem. Certainly, once the facility is set up it is in a much more convenient location, with much lower delta Vs required to move the food to where it's needed.

Yes once you have the infrastructure, which includes food, water, and air to keep people alive.

Yes but it would make much more sense to get the resources we need from the near-Earth asteroids and the Moon than from Mars. They're much "closer" in terms of required delta V to Earth orbit.

[Broomstick]

What if the Mars colonies are self-supporting? What if they can supply food, air, and water to outlying installations, thereby cutting down on shipping costs from the Earth-Moon system?

Maximal in-situ resource utilization is certainly vital to any kind of serious presence in space. You still have to establish the colony though, which costs money. If I were an investor I'd be more inclined to invest in an asteroid mine, because it's possible I can actually make a profit out of it, as opposed to "well, if we can make it self-supporting it'll stop being a drain on me".

Except there are a few investors for whom profit is not the only motive. Richard Branson has sunk tens of millions into space without a penny of profit shown yet, and while I don't doubt he'd like to make money on it, that does not seem to be the underlying motivation here. Governments have been known to engage in long-term plans that don't turn a profit near-term - the Louisiana purchase and purchase of Alaska were both leaps into the dark that were mocked as terrible ideas at the time. For that matter, putting a man on the Moon was certainly not a profit-driven adventure, either.

I doubt we'd be using Mars as a resource extraction point. It sits at the bottom of a fairly deep gravity well, and C-type asteroids are probably richer in resources to boot. If you want a resupply depot in the outer system a main belt asteroid or a Jovian moon makes more sense.

But not as deep as Earth. I don't think we'll stop launching from Earth entirely, so a gravity well isn't a complete obstacle.

You're right that in the short-term a Moon colony would not be self-sufficient but if we are to seriously explore space the paradigm of bringing resources from Earth must change. Earth is a spectacularly uneconomical resource base for space colonies (although with a space elevator it may not be so bad).

That's my point about a Mars colony - it is far more likely to become self-sufficient, and to do so sooner, than a Moon colony. That doesn't mean it's the ideal approach, but it is a possible one.

Potentially profitable IF it is even possible. What the hell do you build a space elevator out of? Do we even have such a material? Is it practical to manufacture in sufficient quantities to the required standard?

A space elevator would probably have to be built of carbon nanotubes. It is not possible to build an Earth-GEO space elevator today, but it should be feasible eventually.

"Eventually". Well, I won't say never but right now "carbon nanotubes" are not something we can crank out by the metric ton, and you'd need an amazing quantity of such. Frankly, every "space elevator" scheme I've read so far seems VERY science fiction. OK, there's a lot of stuff we have and use every day now that was science fiction back when I was a kid, but there's a lot of stuff we don't have that was science fiction, too.

When I start seeing golf clubs and cellphones made out of "carbon nanotubes" I'll start believing we can make the quantity needed for a space elevator - I still won't be sure we can glue them together in a strong enough structure to actually make one.

Sometimes, no matter how badly you want to do it, you can't do some nifty thing.

Most of the estimates I have read say it may be feasible in 50 years. In the mean time, the fact that everything from Earth has to be dragged out of our deep gravity well with chemical rockets only increases the potential usefulness of an orbit-asteroid based industrial complex.

You'll still need to be able to lift people from Earth occasionally. You'll still need to push things around up there, and that means you'll need some sort of propellent/fuel. Just how available is that, really, in NEO? How easy to extract/refine? At least the initial stages WILL require stuff to be lifted up from Earth until we can build the tools to build the tools to do it all in space.

I can actually think of two reasons to colonize Mars that have nothing to do with either mineral extraction or the search for life:

1) Telepresence. I'm really surprised no one else has mentioned this. Right now, there's what, a 10-15 minute time lag between Earth and Mars? With the recent Phoenix probe it went from descent to touchdown before the first signal of "entering atmosphere" even reached Earth. Obviously, we build some autonomy into our machines but the greater the distance the more complicated this becomes, the further you have to think in advance, the more difference dealing with problems becomes... An outpost on Mars is another potential telepresence site, one that may be more convenient to certain far-flung outposts than Earth (there's a complicated stuff happening with orbits, too, but I assume everyone here can figure that out).

True. One could probably use one of the main belt or Apollo asteroids for this as well, but I can see this.

Sure - arguably, Earth, Moon, Mars, and several dozen asteroids could be used with some outposts always under control of just one of them, and others that are moving being handed off from one to another.

2) Food/air/water/etc. Assuming we continue to push further and further out. Assuming a self-sustaining Mars colony can grow surplus food, it may be cheaper/easier/quicker to ship from Mars than from Earth for at least some outposts and circumstances. Air and water might be mined from asteroids, but food has to be grown. In theory we could set up microgravity habitats just to grow food, but in theory we could also farm on Mars.

I think it would probably be a better idea for distant outposts to have closed ecologies; shipping food across interplanetary distances is just massively uneconomical. An algae farm is probably easiest, though algae has some problems with high nucleic acids and low vitamin C, but hopefully these could be solved with a little genetic engineering.

I'm always amazed at space enthusiasts who neglect the importance of cuisine. We have ample data - some of it from past ocean voyages in the days of sail, others from modern studies in undersea habits, Antarctica, and even the military - that for long term tours of duty under stressful, isolating situations food has a psychological role as well as a pure nutritional one.

Algae farms are a shitty idea. You can't live on just algae, and if you did force someone to do so they would get REALLY pissy and depressed. This will not make for efficient space workers. Would YOU live on just algae? Don't get me wrong - I eat algae myself (mmm.... nori.... dulse....nom, nom, nom) but not as a sole diet. But have you ever tasted spirulina? I think vomit is more appetizing, frankly, it tastes GROSS. It tastes exactly like you think fetid pond scum would taste. If I was doomed to eat nothing but spirulina for the rest of my life I'm not sure I'd want to live.

We're evolved as omnivores. We seek changes in taste, texture, etc. Despite the cost of lifting anything into space, food requests are accorded space on the rockets of both the US and USSR going to orbit. It was one thing to force men to eat crap for a week during Apollo - quite another for weeks or months at a time. And then there was the bit where the Skylab guys shoved the chilli out the airlock... but I digress. The point is you're going to need more than algae to keep people healthy both physically AND mentally.

Not to mention there isn't enough fiber in algae to keeps one's digestion moving along. Constipation sucks, alright? And the older you are the more prone you are to it, and since the average age of an astronaut is up in the low 40's, hey, you'll be shipping a LOT of Metamucil. Or feeding them sawdust. Or something. The fact is that we are NOT adapted to living in space. We require elaborate support systems. Including at least a somewhat varied diet.

(And then there is the problem of gout with a spirulina-dependent diet. And where do you get your vitamin C from.)

Dogs will happily live their whole lives on kibble and biscuits. People can not, even on nutritionally complete kibble and biscuits. Food is not purely nutrition - it is also social bonding, celebrations, and a comfort in difficult times. Ignore the psychological dimension at your peril.

Anyway, yes we could grow food on Mars, but we could also do it on the Moon or in orbital habitats using lunar regolith (IIRC NASA did experiments with growing plants in the stuff). Given that most of the space-based population would logically be in Earth orbitals I think having the farms in that area would make more sense. You'd want to have the farms close to the big industrial cities, not on some distant planet half an AU away.

Yes, we could do it other places, but those other places require stuff to be shipped in that is available locally on Mars.

And yes, it makes some sense to have the resupply near the people who need it, but why do you think these space habitats will remain restricted to NEO? For those outposts where Mars is closer Mars starts to make sense as a source of food.

It's true that with orbital habitats you have to import all your construction materials, but a mass driver, scoopship, and rotorvator system should be able to transport quite large quantities of asteroidal and lunar materials into the desired orbits fairly cheaply, so I don't see it as a huge problem.

I see the fact you have to somehow built the first mass driver before you can use it for other construction projects as an issue - where do the resources come from to build that first one?

For the "rotorvator" - the fact that the strength requirements exceed that of any known material is a huge problem. Even for carbon nanotubes there is only a possibility they could be made sufficiently strong in a large structure.

Yes once you have the infrastructure, which includes food, water, and air to keep people alive.

Yes but it would make much more sense to get the resources we need from the near-Earth asteroids and the Moon than from Mars. They're much "closer" in terms of required delta V to Earth orbit.

Maybe the difference between you and me is that I don't expect us to stay in NEO for the rest of eternity.

[Commander 598]

...but why do you think these space habitats will remain restricted to NEO?

Uhh, they won't. The reason why we say NEO is because it's kind of, you know, close, but there's nothing restricting a proper orbital habitat's location except available sunlight.

[Junghalli]

Except there are a few investors for whom profit is not the only motive.

Quite true, but I think ultimately profit-oriented space projects would do better than nonprofit ones. That's just a basic fact of human nature; people will be much more likely to sink money into a project if they can get more money back.

But not as deep as Earth. I don't think we'll stop launching from Earth entirely, so a gravity well isn't a complete obstacle.

No, but it is a great inconvenience. We'll keep launching stuff from Earth because we don't have a choice. Generally, you do want your resource mine to be in as shallow a gravity well as possible.

That's my point about a Mars colony - it is far more likely to become self-sufficient, and to do so sooner, than a Moon colony.

Possibly.

"Eventually". Well, I won't say never but right now "carbon nanotubes" are not something we can crank out by the metric ton, and you'd need an amazing quantity of such.

Yes, true. A space elevator is a far-term project, not a near-term one. I doubt one will be built in our lifetimes. Of course, this only makes orbital infrastructure more useful, as it means everything that comes from Earth has to be dragged up by a hideously inefficient chemical rocket with a towering mass ratio.

Interestingly though, a lunar space elevator could be constructed with present-day materials.

You'll still need to be able to lift people from Earth occasionally. You'll still need to push things around up there, and that means you'll need some sort of propellent/fuel. Just how available is that, really, in NEO? How easy to extract/refine?

This site suggests some C-type asteroids may be as much as 10% water ice (which can, of course, be turned into rocket fuel by simple electrolyses). Even if it's .1% on a 2 billion ton asteroid that's 2 million tons of fuel on just one rock, and there are probably at least several hundred C-type NEAs that size. Extraction should be fairly easy, you just drill down to a pocket of ice and use a mirror to shine sunlight in it, then trap the vapor. Burned-out comets should be especially good sources of volatiles. There should be plenty of volatiles in the NEAs. Similarly, there are estimated to be many thousands of tons of water frozen as permafrost in shadowed polar craters on the moon. It's unlikely that we'll have to go to Mars for volatiles.

At least the initial stages WILL require stuff to be lifted up from Earth until we can build the tools to build the tools to do it all in space.

Of course. Though even the most rudimentary utilization of NEA or lunar resources (like using NEA or lunar derived propellants to lift LEO sattelites to GEO) will be boons to the sattelite launching industry. Pretty much anything is better than having to blast everything up from Earth's surface.

I'm always amazed at space enthusiasts who neglect the importance of cuisine.

Oh I quite realize we'll have to do better than a steady diet of pond slime for our astronauts and space workers.

You could probably put some flavorings in it to disguise the taste and appearance, maybe even use genetic engineering to make the flavor and texture less repulsive. Or you could use some alternate system like conventional hydroponics. My point is some sort of in situ food production would be more economic than dragging tons of food across interplanetary distances. Pretty much ANYTHING is more economical than that.

Yes, we could do it other places, but those other places require stuff to be shipped in that is available locally on Mars.

The Moon and the NEAs should have all the same stuff as Mars has. A farm on the Moon probably wouldn't be all that much harder, and the required delta V to get the food to the industrial cities would be much lower.

And yes, it makes some sense to have the resupply near the people who need it, but why do you think these space habitats will remain restricted to NEO? For those outposts where Mars is closer Mars starts to make sense as a source of food.

Yes but that is a farther future proposition. And honestly, I suspect it would be easier to just grow the food on site, using grow lights if necessary (if you're too far from the sun). You really do want to keep the amount of interplanetary logistical support your colony needs to a minimum, having something as basic and mass-intensive as food be shipped in is very uneconomic.

I see the fact you have to somehow built the first mass driver before you can use it for other construction projects as an issue - where do the resources come from to build that first one?

As a matter of fact an experimental version was constructed in 1976.

For the "rotorvator" - the fact that the strength requirements exceed that of any known material is a huge problem. Even for carbon nanotubes there is only a possibility they could be made sufficiently strong in a large structure.

Fair enough. Until we can build one we'd be stuck with scoopships which would catch them as they enter HEO from their lunar assist captures, probably propelled by electric rockets. You should still be able to move around enough material to build a few greenhouses. The rotorvator is just a convenience, it isn't necessary.

And it's not like using Mars as a resource extraction point wouldn't require its share of as yet on the drawing board technology as well. Such as the big fuel-efficient spacecraft you need to make shipping stuff between planets practical.

Maybe the difference between you and me is that I don't expect us to stay in NEO for the rest of eternity.

Oh, I think we'll move beyond NEO eventually, but it's almost certainly going to be the initial center of development, and I think it's probably going to stay the major center of population and industry for a long time..

[Junghalli]

I really should have checked this beforehand, but I've been taking a look at the Atomic Rocket Mission Table. Delta V for a Mars surface to Earth orbit mission is 9.25 km/s (3.502 km/s to reach Mars orbit and 5.748 km/s for a Hohmann transfer). In other words, for a colony in Earth orbit the Martian surface is basically just as "far away" in terms of delta V as Earth's surface.

I'm really not seeing Mars as a promising source of materials for colonies in orbit. Martian materials in Earth orbit would probably be almost as expensive as Earth materials in Earth orbit; whatever savings you get out of using Martian materials would probably hardly be worth the massive investment of setting up a farm or a mine on Mars.

For growing food, it would make vastly more sense to call the asteroid mine and tell them you want a couple of hundred more tons of iron to build your greenhouse and some bags of volatile-rich dirt.

Mars might make more sense as a resupply base for the outer system but even that doesn't really make sense. The main asteroid belt should be quite rich in minerals and volatiles and you wouldn't have to deal with an inconvenient gravity well.

[Broomstick]

Interestingly though, a lunar space elevator could be constructed with present-day materials.

What about the practicality of a Martian one?

I'm always amazed at space enthusiasts who neglect the importance of cuisine.

Oh I quite realize we'll have to do better than a steady diet of pond slime for our astronauts and space workers.

You could probably put some flavorings in it to disguise the taste and appearance

So, where do those flavorings come from? Of course, spices can be low in bulk (relatively speaking) and last a long time, so lifting them out of a gravity well might make sense.

maybe even use genetic engineering to make the flavor and texture less repulsive.

Maybe... but is our genetic engineering really up to that?

Or you could use some alternate system like conventional hydroponics.

My dad had a hydroponic set up for years. It's quite labor intensive, and you have to guard against contamination. I know they had a mold problem on Mir - you don't want mold in your hydroponics. I'm assuming keeping water circulating and under control in zero g is a problem that either has been or quickly would be solved. However, in the 1970's I know there was some question about whether or not plants would grow properly in microgravity. I can't find anything on line about what was discovered about that issue. I can state, though, that not all plants are suited to hydroponic growth - root crops in particular because hydroponic growing usually results in less root development. Then, too, many plants are inefficient from our viewpoint, growing lots of useless foliage to produce an edible whatever.

If you get stuff growing in a space outpost I'd expect the first plants to be stuff like spinach, which grows rapidly, a large portion of which is edible, is nutritious, provides fiber, and requires minimal processing to eat. And, oh yes, can provide some vitamin C. I don't see anyone growing, say, wheat up in space until we get something large enough for tens of hectares of growing space -- and it still wouldn't be terribly efficient. Well, people can learn to live without bread I suppose, but the diet in space will be different than on the ground, that's for sure.

My point is some sort of in situ food production would be more economic than dragging tons of food across interplanetary distances. Pretty much ANYTHING is more economical than that.

There is the issue of constructing and maintaining the volume of closed environment necessary to grow all that stuff. Choosing plants that produce a high proportion of edible food to overall biomass will help, as well as developing varieties that do well in such places. At least during initial construction of any outpost, though, you will have to import food from someplace else. In some cases there just won't be room to grow food and do everything else that needs to be done.

Yes, we could do it other places, but those other places require stuff to be shipped in that is available locally on Mars.

The Moon and the NEAs should have all the same stuff as Mars has. A farm on the Moon probably wouldn't be all that much harder, and the required delta V to get the food to the industrial cities would be much lower.

Should have all the same stuff is not the same as does have all the same stuff. The Moon's water is very minimal and there is the cost of extracting it. Recycling will be very important, but it may also make more sense to bring in water from elsewhere (gravity is not a problem as long as you don't intend to lift the water back up) once the easily accessible water sources are used up. Anything obtained from asteroids may need processing prior to use in agricultural - too acid, too base, or too many heavy metals would all be problematic. That would also be a problem on Mars, of course. The truth is we can make guesses but we don't really know how to make all this work. We have theory but almost no practice.

And yes, it makes some sense to have the resupply near the people who need it, but why do you think these space habitats will remain restricted to NEO? For those outposts where Mars is closer Mars starts to make sense as a source of food.

Yes but that is a farther future proposition. And honestly, I suspect it would be easier to just grow the food on site, using grow lights if necessary (if you're too far from the sun). You really do want to keep the amount of interplanetary logistical support your colony needs to a minimum, having something as basic and mass-intensive as food be shipped in is very uneconomic.

Again, there is the issue of devoting space/volume, energy, and resources to growing food on a space outpost. Even with the maximum use of automation (already prominent in current commercial hydroponic operations) you still need room for the plants and the machinery. Room is limited in space habitats.

Obviously, we're going to have differences between outposts, and eventually I would expect some to have food production as a major enterprise. In other instances, though, it might make more sense to bring in preserved supplies and use on-site grown plants as a supplement rather than trying to make everything self-supporting. We'll have to discover a lot of this by trial and error and see what works best in reality.

And it's not like using Mars as a resource extraction point wouldn't require its share of as yet on the drawing board technology as well. Such as the big fuel-efficient spacecraft you need to make shipping stuff between planets practical.

I'm not saying we ship stuff between Mars and Earth. Growing food on Mars for Earth is stupid, as everything we have is MUCH more adapted to Earth, nevermind the cost of transport. Growing food on Mars for outposts closer to Mars than Earth is a different matter. Particularly if/when we push out to the asteroid belt and beyond, Mars will become a more economically sensible source of supply and as a waystation.

Of course, some argue that once we leap into space why bother with planets at all? Well, some people might just stay in deep space. I don't think we'll totally divorce ourselves from planets for some time to come.

[Commander 598]

Room is limited in space habitats.

Room is only as limited as the size of your space habitat. If you actually are capable of orbital production size should only be an issue of time...and my definition of "space habitat" is reserved for rather large objects regardless of how far down the road they would be because I doubt anyone would want to permanently inhabit a cramped "station".



Also, if room is that big of an issue build more "habitats" and space out the population.

[Broomstick]

Yeah. Nice idea. But we are nowhere near building anything like that. "Cramped stations" is what we have, and what we will continue to have probably for our lifetimes.

There are people who prefer small, enclosed spaces - the opposite of claustrophobia. While such a mental state is considered an illness on Earth it might be an advantage in space

Also, people do live for extended periods of time in submarines - a great deal of what we've learned about keeping people healthy and functional in cramped quarters they can't leave comes from that experience. Food, recreational opportunities, and morale can be vitally important in such an environment, as can the need for a small but very real amount of privacy. You may have to share a bunk with two other people, in shifts, but you do have personal effects, as an example, which you can secure.

Submarines, of course, can be powered by small nuclear reactions and those that are manufacture their own breathing gas from the surrounding water - an example of how progress in one area can assist in others. If a small body in space has water the technology to utilize it in combination with a small reactor is already well developed. I suppose you can use solar power, too - it's all a matter of utilizing tech and resources in efficient ways for the given locality.

[Junghalli]

Yeah. Nice idea. But we are nowhere near building anything like that. "Cramped stations" is what we have, and what we will continue to have probably for our lifetimes.

First I want to point out that the reason we can't build large space structures is because of the high cost of lifting stuff up from Earth's surface. A big space station would be astronomically expensive because every kilogram of building material must be dragged out of our gravity well with inefficient chemical rockets. With asteroid mining this will change. You only need a fraction of that delta V to move stuff from an asteroid to Earth orbit, and much of it can be done with highly efficient fuel-less propulsion involving mass drivers and lunar gravity assist captures, and where fueled propulsion is required (for the transfer from the HEO capture orbit to the desired orbit - probably GEO) you can use much more efficient low-thrust electrical rockets instead of chemical ones. Asteroid mined material in orbit will be much cheaper than Earth material in orbit and large structures will become much more feasible.

With sufficient material (provided by asteroid mining) there's no reason you couldn't build a space habitat as large or larger than a comparable habitat on a place like Mars. Indeed constructing large structures in space is much easier than constructing them on a planet's surface, since you don't have gravity to worry about.

What about the practicality of a Martian one?

I haven't been able to find any definite statements on what sort of materials would be needed, though it would certainly be easier than an Earth elevator in terms of material strength. One big problem though is Phobos, which orbits below Mars GEO and would collide with the elevator. You might be able to put an active avoidance system on the elevator, or more ambitiously use a mass driver to shift Phobos's orbit so it's out of the way (perhaps use it as the elevator's counterweight).

So, where do those flavorings come from? Of course, spices can be low in bulk (relatively speaking) and last a long time, so lifting them out of a gravity well might make sense.

Yeah, I figure some flavorings would probably be much easier to bring from Earth than the food itself.

Maybe... but is our genetic engineering really up to that?

Not now, but then realistically the beginning of serious solar system colonization is going to be at least a couple of decades away.

There is the issue of constructing and maintaining the volume of closed environment necessary to grow all that stuff.

Certainly, though I imagine as much of the necessary materials as possible would be produced from local resources (such as "lunarcrete" formed by melting regolith in a solar oven). For a permanent installation producing food on site should ultimately be more economic than importing it, even if it increases the start-up costs a bit.

In some cases there just won't be room to grow food and do everything else that needs to be done.

Oh, there's always plenty of room in space. The issue is building materials. Thankfully, using lunarcrete/astercrete large structures should be practical to build from local materials in most places. A bigger issue would be specialized equipment which couldn't be manufactured on site.

Should have all the same stuff is not the same as does have all the same stuff. The Moon's water is very minimal and there is the cost of extracting it.

True, although I think it's far more convenient location compared to Mars should make up for that.

And yes, it makes some sense to have the resupply near the people who need it, but why do you think these space habitats will remain restricted to NEO? For those outposts where Mars is closer Mars starts to make sense as a source of food.

I think most space habitats would be in NEO because that's where it makes economic sense to put space industry (they're probably going to start out as space hotels and industrial stations to service and build sattelites), plus it's the easiest place to reach. People will probably eventually establish habitats beyond NEO, but for that I think the main asteroid belt or the Apollo asteroids would probably make more sense as a source of supplies than Mars. The main belt and Apollos should be quite rich in resources and you don't have Mars's gravity to worry about.

Even with the maximum use of automation (already prominent in current commercial hydroponic operations) you still need room for the plants and the machinery. Room is limited in space habitats.

Room is limited if everything has to be dragged in from Earth or somewhere similarly inconvenient. With asteroid mining to supply Earth's orbitals and use of local materials in construction for distant outposts this should change. A bigger problem is specialized equipment that the food production facilities would require, which couldn't be produced on site in the outpost. Still, unless the outpost is temporary or sporadically inhabited spending extra to take along the necessary materials will usually make more sense. The initial ship you have to send is a little heavier, but then you save yourself from having to ship many tons of stuff later.

[Broomstick]

Yeah. Nice idea. But we are nowhere near building anything like that. "Cramped stations" is what we have, and what we will continue to have probably for our lifetimes.

First I want to point out that the reason we can't build large space structures is because of the high cost of lifting stuff up from Earth's surface.

There is also the issue of experience and personnel. We have theory on how to build big in space, and certainly the current space station is giving us some small experience, but I am certain that as we scale up we'll encounter problems time and again. Additionally, personnel will be needed for those things we can't automate, which means lifting them and their life support to orbit.

Once we get the first sizable habitat up and running subsequent ones should be easier in at least some respects.

There is the issue of constructing and maintaining the volume of closed environment necessary to grow all that stuff.

Certainly, though I imagine as much of the necessary materials as possible would be produced from local resources (such as "lunarcrete" formed by melting regolith in a solar oven). For a permanent installation producing food on site should ultimately be more economic than importing it, even if it increases the start-up costs a bit.

Biosphere II here on Earth ran into problems with concrete as it continued to "cure" over time. Granted, Biosphere II is considered to be a failure by many but part of the point was to discover problems here on Earth, where they wouldn't kill people. That's an example of the sort of unanticipated problems that are likely to come up over and over again. I don't know if "lunarcrete" would have similar problems or not, or if it would react if it came in contact with a human-compatible atmosphere. Do you?

In some cases there just won't be room to grow food and do everything else that needs to be done.

Oh, there's always plenty of room in space. The issue is building materials. Thankfully, using lunarcrete/astercrete large structures should be practical to build from local materials in most places. A bigger issue would be specialized equipment which couldn't be manufactured on site.

True. And that gets into automation vs. people again. You can have very successful low-tech hydroponics (my dad used such a set-up) but they require human labor. It's not intensive but it IS required on a daily basis. But humans require life support, and they are expensive to transport. Machinery might have a high initial cost, but it doesn't consume food, oxygen, and water and for boring stuff (like growing things) more reliable.

People will probably eventually establish habitats beyond NEO, but for that I think the main asteroid belt or the Apollo asteroids would probably make more sense as a source of supplies than Mars. The main belt and Apollos should be quite rich in resources and you don't have Mars's gravity to worry about.

Why is gravity all bad? We don't know if humans can live long-term in microgravity, we don't know if we can reproduce in it, if such children would be healthy. Obviously, if we go into space at some point that "experiment" will occur, but if the answer is "no, microgravity is not compatible with normal lifespans or human reproduction" then Mars starts to look a LOT more attractive. There might be other reasons we'd want to conduct business at the bottom of a gravity well.

[Junghalli]

There is also the issue of experience and personnel. We have theory on how to build big in space, and certainly the current space station is giving us some small experience, but I am certain that as we scale up we'll encounter problems time and again. Additionally, personnel will be needed for those things we can't automate, which means lifting them and their life support to orbit.

Yes, but the same is true for a large planet-side base. We don't have much experience building large airtight structures in uninhabitable environments either.

I don't know if "lunarcrete" would have similar problems or not, or if it would react if it came in contact with a human-compatible atmosphere. Do you?

PERMANENT's descriptions don't really say, but it doesn't mention anything about it reacting negatively to non-vacuum conditions. Curing shouldn't be a problem as lunar or asteroid "cretes" would be ahydrous; they're melted or vitrified dirt, not true concrete. If lunarcrete is problematic for some reason we can always use glass-ceramics instead (produced by a similar process), which have been successfully used to make pipes and tiles on Earth.

Why is gravity all bad? We don't know if humans can live long-term in microgravity, we don't know if we can reproduce in it, if such children would be healthy. Obviously, if we go into space at some point that "experiment" will occur, but if the answer is "no, microgravity is not compatible with normal lifespans or human reproduction" then Mars starts to look a LOT more attractive. There might be other reasons we'd want to conduct business at the bottom of a gravity well.

If you want gravity in space you can just use centrifugal gravity. Just build a big ring and mount your habitat modules on it and spin it, or arrange your habitat modules at the end of a long tumbling pole or tether. You don't need to put yourself at the bottom of a gravity well to have gravity. In fact centrifugal gravity is arguably better as you can vary it to your choosing: you could have zero gee facilities in the middle and varying levels of gravity as you move out, optimized to whatever your needs are.

[Commander 598]

Yeah. Nice idea. But we are nowhere near building anything like that. "Cramped stations" is what we have, and what we will continue to have probably for our lifetimes.

It should be pointed out that while the original Bernal Sphere was supposed to be 16km in diameter, the O'Neill Island 1 variant was only 500m in diameter. That's not exactly a megastructure...