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Friday, 27 May 2016

Homes in space, part 1: Space stations...

Apologies if you notice some issues with formatting ad spacing - I'm loosing to my own html at the moment, but I'm working on it!

It’s an exciting time for fans of expanding human presence into the soar system: Orbital ATK, who build cargo ships for the ISS, have announced preliminary plans to build a deep space station. Bigelow aerospace have their groundbreaking inflatable space habitat attached to the ISS undergoing testing. The ISS itself is no longer a half built techno turkey but a scrumptious techno roast dinner with all the trimmings: It has served as a launch site for miniature space satellites, a destination for space tourists, boasting its own gym, internet connections, cupola, and masses of experiments going on. Spacecraft from across the world dock regularly to bring fresh crew, supplies, and experiments.

Above: The International Space Station. Tastes great with gravy, mm-mmm.

But what about the future of humans in space? There’re no guarantees the spectacular visions folks like Robert Bigelow and Elon Musk have – of a solar system full of human presence - will come to pass… but they’re certainly hard at work trying to make it that way.

Let’s assume they succeed, and in the late 21st century/ early 22nd century an interplanetary traveller needs a place to rest their weary, space suited, head. What are the options likely to be?

Types of space stations:

We’ve had a pretty few of these over the years – Skylab, Almiraz, Salut, Mir, Chenzou, and the ISS. Recently people are trying to make them 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.

Hard- hulled space stations:

Until recently all space stations have been of this type – Mir, Chenzou, ISS - basically a big tin can in space*. OK, a very strong tin 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.

Soft hulled/ inflatable space stations:
Above: The BEAM module, depicted fully nflated. Which they haven't managed yet.

A new development, but based on an old NASA design called Transhab: These’re bouncy castles in space, albeit bouncy castles made of unbelievably tough material. The air pressure inside one keeps it inflated and rigid, and it’s launched folded up, saving a lot of launch volume. Using air pressure 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.

Above: Bigelow's Genesis 1 space habitat.

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...

That’s the technology available – what about the all important location? 

Above: The inside of a Genesis module, fully inflated, with people's photo's (and trinkets they sent into space) floating about.

Possible Locations:

Earth orbit: 

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 ly increase a persons risk of cancer. Earth’s magnetic bubble diverts the worst of this.

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 satellits and pieces of satellites, whizzing along at 11 km/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 probaby caused Tim Peake to change his sace underwear.

    Space stations between the Earth and Moon:

    Above: A Cygnus freight ship, the proposed base unitfor Orbital ATK's space station.

    An idea that is being seriously looked at, and might well get built. The two most often proposed sites are 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 sited 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 befpre. Protecting such a station 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 a real storm.

    Space stations around other 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...

    Next: Bases on other worlds...

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

    ** This has happened- link here
    *** I couldn’t resist, sorry.


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