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Thursday, 26 March 2020

Answers for Authors: Where can my characters stay as they travel the galaxy?

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Part 1: Stations, bases and habitats....
At least the ISS has toilets and Internet... 

It's hard to imagine Darth Vader couch surfing his way across the galaxy, although I can see Kylo Ren doing that. But everyone needs to get their head down somewhere and, while some spaceships are flying cities with accommodation for thousands, even the La Sirena from Star Trek Picard is bit cramped to live in for months or years of a long interstellar journey.
So what are the options for a weary Starfury or X-wing pilot to put their head down?

Space stations - the kind that are being designed and built for real today:

We’ve had a pretty few of these over the years – Skylab, Almiraz, Salut, Mir, Chenzou, and the ISS. Generally they're classed as 1st, 2nd, or 3rd generation: Originally these were just a habitat module with a single docking port for a capsule to return the crew to Earth, and were abandoned when their supplies ran out (generation 1 stations) . Later models had two reusable docking ports and air locks, allowing multiple crews to stay over time, and conduct spacewalks (generation 2). Since the 1980's bigger space stations have been made of semi independent modules, each with a separate purpose, that are flown into orbit and assembled there (generation 3). Recently people are trying to make staying in a space station more affordable, widen access, and get more people living and working out there. 

It looks like there could be three main types of space station for the 21st century: Hard hulled (like the ISS), inflatables (like the BA330 module Bigelow Aerospace is working on), or a combination of both types. To date they have no kind of artificial gravity, although some experiments on them have centrifuges to supply variable 'gravity'. That means the crew spend a lot of time exercising to stave off the wasting effects of microgravity, and ensure they sleep in an air current to avoid a bubble of CO2 building up around them. They also have at least enough capsules to carry the whole crew back to Earth docked at all times, and each of these will have a survival kit, including a hand gun, aboard (so, yes, there are guns in space right now - and they belong to the Russian crew) .
The basic construction methods are...

Hard hulled space stations:
Above: Mir, the original hard hulled modular space station

Until recently all space stations have been of this type – Mir, Chenzou, ISS - basically a big can in space*. OK, a very strong can designed to survive for years in space and support a continuous crew, run experiments, house space telescopes, launch mini satellites etc etc. But, on some level, a can filled with air. It's a reliable approach to building an orbital home: The ISS, for example, has served as a launch site for miniature space satellites, a destination for space tourists, boasts its own gym, internet connections, viewing cupola, and masses of experiments going on. Spacecraft from across the world dock regularly to bring fresh crew, supplies, and experiments. And it's set to leave more than just a legacy: Private company Axiom Space plan to built an extension to the ISS that will become an Independent station when the ISS is eventually retired.

Inflatable space stations:
These are a new development, but based on an old NASA design called Transhab: They’re bouncy castles in space, albeit bouncy castles made of unbelievably tough material. The support structure of one is filled with gas under pressure to make it rigid, and it’s launched folded up, saving a lot of launch volume. Using inflatable structures this way also saves on the weight of a traditional support structure.
Bigelow Aerospace has launched two prototype inflatable stations – Genesis 1 and Genesis 2, as well as its BEAM module on the ISS. Genesis 1 and 2 performed very well – in fact both are still in orbit and pressurised today. This looks like a real possibility for the next few decades or space exploration.

A combined design:
In theory a prototype of this, using both hard shelled and inflatable modules, already exists in the form of the ISS with BEAM attached – and until the inflatable designs have really proven themselves this is probably how they will be used...

Planetary bases:

ESA is currently trumpeting the idea of a 3D printed Moonbase, made at least partly from the lunar soil. Habitat modules – and you could use the exact same types of module used to build space stations - would be buried beneath meters of lunar dirt to provide radiation protection. The prime site for such a base would be at the lunar poles: That would put it close to places of scientific interest (like the valleys of eternal shadow), and close to mountain tops that get almost nonstop sunlight. That would give the base an abundant power supply, and the ices frozen in the dark valleys would allow the base to experiment with producing their own water, oxygen, and fuel.

Above: An artists impression of ESA's proposed 'Moon Village'. Courtesy of ESA. 

Martian Base:
On Mars ice is abundant near the surface in many areas, but the thin atmosphere is a pain: It’s thick enough to produce global dust storms that can block out the Sun for months (and plummet the surface temperatures waaay below freezing), making solar power unreliable – but it’s too thin to provide much radiation protection, or any real help in landing a spacecraft big enough to carry people. And, because the launch windows to and from Mars are so far apart, a Mars base will have to be built as apart of any attempt to and people there: They will be there for months at least.

Above: Artists impression of a Martian outpost, courtesy of NASA

For a larger base on the Moon or Mars you could look to their networks of tunnel like lava tubes. These tunnels, carved out by ancient lava flows, can be nearly a mile across, and would provide protection for a small city, even from the fiercest solar storms….

Venus Base:

An artist's impression of a Venusian base, courtesy of Xmadedx

This idea was floated*** decades ago: Although the surface of Venus is much like one of the less salubrious suburbs of hell, there is a layer in the atmosphere, about seventy kilometers up, where the temperature and air pressure are compatible with liquid water and human life. Radiation levels there are tolerable, and the gravity is 90% of Earth-normal.
In the Venusian atmosphere breathable air is a lifting gas, so a light weight dwelling full of Earth-normal air will simply… hang there. In fact, this layer of Venus atmosphere is actually the friendliest spot for humans in the whole solar system: It holds fewer challenges to overcome than even Mars.
If this sounds a little like something from Star Wars that’s because it’s exactly like Bespin city from Empire Strikes Back – but it could really be built, no sci-fi antigravity needed.
There would still be the teensy problem of all the acid clouds to overcome, but humankind has been protecting our structures from corrosion for centuries. And probes sent to hover on balloons through the Venusian clouds have held up pretty well.
The inhabitants of such a place would probably be scientists studying the planet below – from an aerostat home they could remote control robots on the surface, trying to unlock Venus’s mysteries. There’re also plenty of unusual chemical phenomena in the acid rain clouds. So, if you’d like to drift off to the sound of (battery acid strength) rain on you window, head for Venus.

Space habitats:

But all those are small fry. There are designs for much more impressive living spaces that, although we probably won't be building them anytime in the future, might be built by future generations. These are true space habitats, not stations, in that they provide a fairly Earth-like environment - including gravity, or a reasonable imitation of it. To keep thing manageable I’ve divided them into three broad category's:

Space bases we could build today - if we had the money:
In many ways this is the most interesting category, because the engineering and maths for these ideas checks out… it's just the maths associated with construction costs that don't close. And by ‘don’t close’ I mean you'd probably have to mortgage Earth itself to pay for just one.

I'm not sure who you'd mortgage it to, either... 

As such they make a cool look at the kind of in-space megastructures we might build if we really do expand into our solar system in a big way - to make them work monetarily we’d have to have a thriving off world economy, and the means to transport many thousands of residents off Earth and onto the new colony. As we’d need to get tons of building material, and power from in-space sources, to make these ideas work some of the concepts that companies like Planetary Resources and SpaceX are working on (asteroid mining, space based solar power, and mass space transportation) may one day feed into these concepts...

Bernal Sphere:
A steel and concrete globe about a third of a mile in diameter, floating in space, the Bernal sphere wold be a teeny, inside out, planet. Residents would live inside and it would rotate once every thirty seconds to provide Earth like gravity along its equator. Since this artificial gravity would peter out near the poles, and the poleward surfaces would appear to be sloped, it would be like living near the bottom of a really weird valley, wrapped around itself. A valley with one added bonus: If you climbed the walls high enough you could fly!
10,000 people could live in one, their buildings lining the curve and appearing overhead. Although it’s a perfectly good design, I like to look at the stars at night, so the Bernal Sphere’s not my personal favourite – although I could always just dig ‘down’ until I found them…

Stanford Torus:

Above: The Stanford Torus from the movie Elysium. 

Have you seen the movie ‘Elysium’? That space station is a Stanford Torus: A donut-shaped tube 130 meters thick with a diameter just over a mile. It also spins to produce its gravity. The original, 2 km wide, Stanford design would need to be enclosed, but bigger versions - with a radius of 100km or more - could have side walls deep enough (50km plus - similar in height to the seriously proposed Thoth Technology tower) to keep most of the atmosphere in with 
only spin-gravity protecting the top. So, in combination with a low pressure, oxygen rich, atmosphere a habitable environment could be maintained open to space, as long as it got topped up regularly.  
The basic, 2km, torus would house a similar number of residents to the sphere. I prefer the torus as, looking up, you’d see both the far side of the torus, and the stars beyond. Spokes could connect the habitat ring to a central hub where spacecraft can dock, so when you visit your first sight will be the whole ring stretching around you. Weighing in at 10 million tons, you’d need an asteroid mining industry already in place to build this beast, but it could certainly done using materials like steel and concrete.

The O'Neill Cylinder:

Above: The Babylon 5 space station, the adventures of which crew I watched on a Sunday as a kid.

If you’re old like me**** you probably remember a Sci Fi show called Babylon 5. If you don’t: The show was about the crew of an O'Neill cylinder, christened Babylon 5. As the name suggests, it’s a cylinder the main body of which is about 5 miles wide and 20 miles long. Once again, a gentle spin of one revolution every minute and a half would be enough for terrestrial gravity. O'Neill’s original design had two cylinders built in counter-rotating pairs to offset destabilising, gyroscopic effects that would cause the cylinders to stray from their intended, Sun-facing angles.

While any of these space colonies would be far more vast than the International Space Station, their engineering challenges could be met. "From an engineering standpoint, the structure is very easy—the engineering calculations are totally valid," says Anders Sandberg, a research fellow at Oxford University who has studied megastructure concepts.

Ideas that might be built using the strongest conceivable materials:

These are space habitat concepts where the engineering numbers close... just barely, and only if you use things like carbon nanotubes, or mass manufactured diamond. To build these structures you’d need massive amounts of such super-strong building materials – and, since these materials are usually only available in tiny quantities, these ideas will almost certainly stay fictional for a long time. But, that said, the numbers do close in theory...

Bishop ring:

Above: An artists impression of a Bishop ring 

A Bishop Ring, originally proposed in 1997 by Forrest Bishop, is the Staford Torus’s big brother. Like Stanford's design, the Bishop Ring would spin to produce artificial gravity, but differs that it would use carbon nanotubes instead of steel. That would allow it to be approximately 1,000 km in radius and 500 km in width, containing 3 million square kilometers of living space – about the same size as India.
The habitat could either have an arrangement of mirrors to reflect sunlight onto the inner rim or an artificial light source in the middle, powered by a combination of solar panels on the outer rim and solar power satellites.

Mckendree cylinder:

Above: Artists impression of the inside of a McKendree cylinder, courtesy of Eburacum 45. 

The Stanford Torus has a big brother, and the O’neill cylinder has one too: A McKendree cylinder is a space habitat originally proposed at 'NASA's Turning Goals into Reality' conference by NASA engineer Tom McKendree. As with other space habitat designs, the cylinder would spin to produce artificial gravity by way of centrifugal force. It differs from the classical designs by using carbon nanotubes instead of steel, allowing the habitat to be built much, much, larger. In the original proposal, the habitat would be 460 km in radius and 4600 km in length, containing 13 million square kilometers of living space… nearly as much land area as Russia.
McKendree proposed dedicating half of the surface of the colony to windows, allowing direct illumination of the interior. The habitat would be composed of a pair of counter-rotating cylinders which would function like momentum wheels to control the habitat's orientation.
Complete flights of sci-fi gibberish? But then, what would the people of the Roman empire thought of the geostationary satellite ring that encircles our planet, 36,000 km wide? Or the Three Gorges dam?

Those are the building methods available – what about the all important location?

Possible Locations:

Orbit of Earth (or the local habitable planet):
Being sited near Earth has it’s advantage… and it’s perils. On the pro side:

  • A station in Earth orbit can be powered by solar panels.
  • Should anything bad happen it’s short journey back to the safety of Earth – the ISS and most other stations have at least one man rated space craft docked at all times, to act as a life boat should aliens attack, someone crash into the station**, or a storm of space debris threaten to tear the place to splinters.
  • Being close to Earth also means that the station can take advantage of the Earth’s magnetic field. Cosmic radiation can seriously increase a persons risk of cancer. Earth’s magnetic bubble diverts the worst of this, so staying within it makes sense.
On the con side…
  • Have you seen that movie about the storm of space debris that chews up everything in orbit? Well, that’s not the far fetched nightmare scenario you might hope it is, although such a chain reaction wouldn’t happen that fast: Near Earth space is pretty crowded these days, and what it’s crowded with dead satellites and pieces of satellites, whizzing along at 7 or 8km/sec. Satellites have been blown apart by it, the ISS has had it’s reinforced windows damaged.
  • Space agencies track the larger pieces, and space stations often have to manoeuvre to avoid anything that’s going to come too close
  • Above: The cracked ISS window that probably caused Tim Peake to change his space underwear
Between the Earth and Moon:
Above: A Cygnus freight ship, the proposed base unit for Orbital ATK's space station

An idea that is being seriously looked at, and might well get built. The most often proposed site is at a Lagrange point between Earth and the Moon, and in orbit about the Moon. A Lagrange point is a place where the gravitational pull of two objects cancel out, creating a zone where objects can sit without needing to orbit anything. That makes navigating and docking to a station there a lot simpler, and also makes the station a convenient point to store fuel and other supplies for missions deeper into space. Orbital ATK is proposing to build such a station from two of it’s Cygnus freighters, which would be loaded with goods as they left Earth. Such a space station could also be used to conduct better microgravity experiments, and as a safe refuge if a Lunar mission ran into trouble a-la Apollo 13.

A graphic of Orbitals proposed lunar station. Courtesy of Orbital ATK

But the big question mark over a Lagrange point or lunar orbit space station is the cosmic radiation problem we mentioned earlier. Protecting such a station has never been tried before, and while there are a few potential technologies that could do it – from simply lining the walls with water tanks to a magnetic field around the station that would imitate Earth's - none of them has ever been tested against background space radiation, never mind the type of radiation storms our Sun can put out.

Orbits around non-Earth-like planets:
If we look a bit further ahead, at space stations around Mars, Venus or other worlds, we need to deal with all of the above and new kinds of challenges: A station orbiting Venus or Mercury would need a beefed up thermal regulation system, to shed the heat from the intensified sunlight. Go much further out than Mars and your station can no longer collect enough sunlight without an unrealistically huge set of solar panels, so you’ll need a nuclear generator, or other more complex power source... but it will probably be a very long time before we have manned stations that far out.

*Let me be clear: It is definitely lot more complicated than that – lest some ESA engineer come to my house tonight and slap me

** This has happened- link here:

*** I couldn’t resist, sorry.

**** I saw my first home computer at age 10. My 3 year old son has to have his tablet time rationed.

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