This is a question I have regarding the design of space habitats. Basically, a lot of the designs I've seen end up having transparent roofs that are open to space, like this:
Or this (technically a floor):
And many other examples like these.
My question is would large open windows to space like this be viable? My gut says that there would be severe problems with radiation shielding, but I'm not sure. Are designs like these viable?
Thanks!
Many of these artistic works are old - this changes a number of assumptions made by the people commissioning the work and the artist/s themselves in terms of what is possible, and what risks matter. Also relevant is that they are visually striking - other more sensible designs with short sight lines and smaller windows make for rather more forgettable art, so are copied and remembered less.
The big spinning designs have a myriad of engineering issues, so hand waving radiation shielding is a quite minor additional detail.
In the case of the second illustration, it is an O'niell cylinder which orbit end on to the sun (so cylinder cap is the bit getting solar radiation), with the angled reflectors bouncing light in but allowing harder radiation to pass through, with a substantial atmosphere depth adding a layer of shielding akin to earth. It is however notable that it appears the updated 2007 design deletes the windows because of the radiation challenges.
They could have, but the odds are that such windows will be relatively rare features reserved for, for example, an observation deck, as opposed to for letting in sunlight to grow plants.
Since this question is about viability, let's start by considering the most economically viable space settlement.
Al Globus made a pretty good case that the most economically viable space settlement should be built in a low equatorial earth orbit because then it would be close to Earth and relatively well shielded from space radiation by Earth's magnetic field. Inside such a habitat, we will need to create a 24-hour day-night cycle. Windows in a rotating habitat located in low earth orbit are not going to do that.
An approach that might make more sense would be to place solar panels on the outside of the habitat and use them to power LEDs on the inside of the habitat. I do recall a presenter at a conference that I attended some time ago saying that you can deliver more useful light to plants with solar panels and LEDs than you can by placing them in direct sunlight - even after factoring in the energy conversion losses.
For people (who do appreciate windows) a possible alternative might be to install large displays that create the illusion of a large window. At the rate we are progressing with developing display technology, by the time we build a space station the view we experience from an artificial window might very well be better than glass.
Another alternative to real windows might be to use advanced augmented reality headsets that simply render windows with beautiful views in the wearer's field of vision.
Other requirements influence the hull design for a space station. Good strength-to-weigh is important if you want to spin the station to create artificial gravity. The hull should help protect its occupants from meteorites and space debris (see Whipple shielding). Finally, there may be a need to provide some additional radiation shielding beyond what the Earth's magnetic field provides naturally. These requirements are not particularly compatible with a desire to include large transparent windows.
Conclusion
The primary reasons for large windows are: a) to provide "light food" for plants, and b) so that humans can see outside. Both of these requirements can be satisfied in other, potentially better, ways. Other requirements include the need for impact resistance, radiation shielding, and high specific strength. When considering all of the requirements together, large windows made from a transparent material will be far from ideal from an architectural or engineering perspective. For the time being - at least until our technology becomes a lot more advanced - every design choice will need to be pretty optimal for a space habitat to be viable.
First of all, is radiation really an issue?
I think it's a pretty safe bet to say that cancer will be "cured" within the next 50-100 years, or at absolute minimum, reach a point where handling it is nothing more than an over-the-counter pill or something similar. More optimistically, we might be able to simply genetically modify people to simply be more adapted to life in space and be nearly unaffected by radiation.
Basically, by the time we are considering constructing megastructures such as these, the issue of radiation will have become significantly less of an issue.
Beyond that though, there is no reason we can't construct radiation shielding which is only translucent specific parts of the electromagnetic spectrum. For example, sunglasses are commonly already designed to not let UV light through or the door of a microwave is designed to let you look through it while still blocking the high-powered microwave radiation.
The materials science of of a material that's supposed to be transparent to human vision (and perhaps let through some UV for plants too) while being opaque to all other space radiation would be tricky and possibly expensive, but not impossible.
