# Solar panels on rotating wheel space stations

What would be the best configuration of solar panels on a rotating wheel space station? I am thinking about Space Station V design and dimensions.

Space Station V comes from 2001: A Space Odyssey.

Space Station V was the largest orbital structure ever built as of 2001. It is a large, international, rotating wheel space station, used as a transfer point from Earth orbit to the moon and other planets. It featured an orbital hotel, run by Hilton Hotels; a Howard Johnson's restaurant; lounge areas; and picturephone booths.

The spinning of the station generates artificial gravity, equal to about that of the moon's gravity. This gave travelers from Earth a chance to acclimatize to the low gravity.

Space Station V has two docking bays on either side of the rotational axis of the station. By 2001, the station is still under construction. The first wheel has been completed, and a second wheel is being constructed.

Dr. Heywood Floyd visited Space Station V in 2001 on his way to Clavius Base.

• Diameter: ~300 m (984 ft)
• Height: ~150 m (495 ft) (along rotational axis)
• Average speed: ~17,500 mph (5 miles/ second or 7823 metres/ second)
• Orbital Period: 91 minutes
• Rotational Period: 61 seconds
• Altitude: ~210 miles

(Source)

• The more often it can face the sun the better. I think you can get a less generic answer if you provided us with more details. E.g. What does the spaceship look like and what is it orbiting. – Shadowzee May 23 at 2:28
• What are the outer and inner radii of the station? How much power is required? What efficiency to the panels enjoy? Are we assuming current tech levels, or something else? These details are important because one small panel is much more easily placed than an hundred large panels - especially when the support structures must be considered. – JBH May 23 at 2:30
• In addition to @JBH's questions - what is the design of the space station? One rotating ring? 2 counter-rotating rings? Rotating ring with static counterweight? – Chronocidal May 23 at 12:07
• @Bob516, I added the pertinent data to your post. You are expected to bring these details into your questions rather than make visitors go hunt for the data. Failing to provide this data often results in votes of "low quality" (which this question had been flagged). – JBH May 23 at 17:17
• @JBH Thank you! – Bob516 May 23 at 17:18

Well, obvious answer: have a non-rotating section. If you look at artwork of classic space station designs like the 70s Bernal Sphere, you'll see they have a nice rounded rotating section, and also a thin spindle with various boxy bits and panels attached. That spindle does not rotate, so all your zero-g infrastructure can be attached to it.

This could include your docking facilities by the way... cool as the rotating docking bays in many of these rotating designs are, they sound like a safety and engineering nightmare.

Similarly, you've got a 90s fictional design based more on the O'Neill cylinder in the form of Babylon 5 which has a more obvious division between rotating and non-rotating. Although I don't think the series ever showed this, you could probably turn the solar panels on their long axes to better catch sunlight, if necessary (something that the Bernal sphere in the image above couldn't do... I'll bet the artist wasn't a space engineer!). If you look at timelapse videos of the ISS, you can see the big solar arrays doing just that.

If you put the station in orbit around the sun, or in a sun synchronous orbit around a planet or at a planetary Lagrangian point (preferably $$L_4$$ or $$L_5$$, as they're the stable-ish ones) you could set things up so that you could ensure that your solar panels were always pointed the right way and you'll never get shaded by a planet.

The designs work just as well with a wheel as with a (possibly rounded) cylinder. Mount the whole thing on some vacuum-safe and robust mechanism, like a magnetic bearing, and you're good to go.

Remember also that real space stations don't just need power... they need heat rejection, too. Having parts of the station that permanently face away from the sun means you've got an excellent place to put your radiators.

If it's a wheel then it has a top and bottom.

So just have the wheel rotate in a way that the flat side faces the sun, and have all the panels on that side. You get 100% coverage all the time like this.

Your only real issue is your station will frequently be 50% of the time blocked by whatever planet it is orbiting.

If you are asking for a space station looking simply as a wheel rotating around nothing to stimulate the gravity, then you could have almost any symetrical configuration ( symetrical because it has to rotate around the middle), the wheel should be facing sun and the solar panels could be covering the whole wheel for maximal efficiency while keeping the shape.

• Welcome to the site Vít Hanika, when you have a few minutes, please take the tour and read up in our help center about how we work: How to Ask. Very succinct answer, answers the question just fine in my view. – Confounded by beige fish. May 23 at 12:30
• But in an orbit isn't the largest surface area of the station facing the Sun for only part of the time it is in sunlight? Wouldn't a substantial part of the time only the edge of the wheel be facing the sun and so limit the amount of surface area that could be generating power? – Bob516 May 23 at 12:35
• Orbital attitude could be optimized for solar cells, and not tidally locked to the planet. (I of course meant to write How to Answer ;)) – Confounded by beige fish. May 23 at 12:38

Add a third very thin wheel - and put it in the right place

The most efficient solution I can think of, although it might have stability problems, is the following:

• The space station must have a sun synchronous orbit. Any other type of orbit demands more solar panels, increasing cost and decreasing mean time between failure (MTBF).

Sun synchronous orbits (SSO) are walking orbits whose orbital plane precesses with the same period as the planet's solar orbit period. In such an orbit, a satellite crosses periapsis at about the same local time every orbit. This is useful if a satellite is carrying instruments which depend on a certain angle of solar illumination on the planet's surface. In order to maintain an exact synchronous timing, it may be necessary to conduct occasional propulsive maneuvers to adjust the orbit.

• One of the two bases (flat sides of the cylinder describing the station) must always face the sun. This might require near constant thruster usage because it's not what the gravitational ebb and flow wants the station to do. However, as I'm about to explain, there's plenty of power to do this.

Having done that, you can create a "third wheel" to the station. Not a full wheel as shown in the diagram, but a "fan" or very thin wheel1 upon which is mounted solar panels. Enough surface area exists (and enough technology exists as described by the station) that the "panel wheel" could come short of the habitat ring so as to not block the view (of the sun, which might need to be blocked anyway — but maybe your people have excellent tinted glass).

Assuming the habitat ring thickness is approx 10% of the radius of the entire wheel, and that the docking core also represents 10% of the radius of the entire wheel. The surface area of the "panel wheel" is 12,016.6 m2

Using only today's efficiencies, that's at best 200 W/m2 for 24 hours (perfect sunlight exposure yo!) or 11,536 mWh daily, which is enough to power the station and the Mars-busting death ray attached to it. To give you a comparison, Hoover Dam generates about 12,000 mWh daily and serves the needs of some 8 million people.

1If you cover the spokes of a bicycle tire with tinfoil, I'm talking about the tinfoil.

• u probably wish to replace mWh to MWh – MolbOrg May 26 at 13:51