# Could an orbital photoelectric generator work?

First I'm going to expand on what I mean by this generator: the photo-electric effect means that metal spaceships will slowly become positively charged as they fly across space, but for the purposes of this question, I plan to have six geostationary stations in orbit around Earth, equidistant from each other such that on the X, Y and Z axes you will have one station every 1/4 of a rotation around Earth. Between these stations on the X, Y and Z axes there are needle-like magnesium pods in orbit between the stations and becoming positively charged, so by the time they reach the next station they should have become sufficiently charged (if they are in view of the Sun) to be able to produce a few thousand volts (or more).

EDIT: I know that the pods themselves do not need to move in order to be able to generate electricity, but as they travel they have time to charge between stations, which effectively has a larger area, but without building more permanent structures.

My question is not whether this is practical or not, but whether this is possible and whether the physics checks out?

• @Aify the photovoltaic effect is NOT the photoelectric effect, the fist is how solar panels work and is to do with semiconductors, the second is entirely different Jan 5, 2017 at 17:18
• the photovoltaic effect's first step is the photoelectric effect.
– Aify
Jan 5, 2017 at 17:22
• By the way: science-based and reality-check are often considered to be disjunct tags. It would be clearer if you could decide for one of them. Jan 5, 2017 at 20:00
• Forget about the electric part: your orbits just aren't going to work. Taking Z as the axis of rotation, you can get 4 stations equally spaced in an equatorial orbit (the XY plane), but your 2 Z stations are going to be in polar orbits with changing distances to the XY stations. Or conversely, you could put 4 equidistant stations in polar orbits, but then the 2 in equatorial orbits would vary their distance to others. Best you could do is something like the GPS constellation: gps.gov/systems/gps/space Jan 9, 2017 at 5:44
• @Buldelu It may be conventional wisdom that science-based and reality-check overlap and/or are disjunctive, but conventional wisdom in this instance, like many other instances of conventional wisdom, is a load of dingo's kidneys. The combination can be checking the reality of a question's science content. Jul 23, 2017 at 10:54

For a short time this works. But in the long run you need to deal with the following:

You lose electrons to space and can use this potential difference to make an electric current at the stations. But your system in space will lose electrons over time making it harder to emit electrons by sunlight.

So you need something to replace these electrons. I would recommend a permanent connection to Earth, because the discharge of spaceships flying to the stations could be hard to handle. So you need geostationary orbits and some type of cable connecting your stations to Earth.

This cable could be a problem now. I do not know any material that would work for that, so you might need some investigation here.

• Not sure about the mechanical properties, but carbon nanotubes might be the trick - or some composite using them. Nanotubes have excellent electrical properties along the longitudial axis. Jan 9, 2017 at 13:59

You misunderstand how the photo-electric effect works. Movement is not required, instead you need a panel to face the sun. They're called solar panels, and they already exist, and have been generating power for us for quite a while now.

You don't need a ship to fly across space, you want a station that orbits the Earth in a fashion that allows it to stay facing the sun while the Earth orbits around the sun.

• Sometimes the simple answers are best. This didn't get the love it deserved, it definitely should get more. Plus one for commonsense and what should be the right answer. Jul 23, 2017 at 10:56
• @a4android Thanks. Seriously, I really appreciate it when people have common sense :)
– Aify
Jul 23, 2017 at 17:51
• Me too! Solar panels will do the job without elaborate contrivances. What more is needed? Nix! Jul 24, 2017 at 2:22

In principle, I think, it can work. But there are problems to consider:

1.) If the stations have exactly the same orbits than the collecting pods, they either can't have relative velocity, as they meet, or have to be on the exact opposite orbit. (retrograde) So they either can not move away, or do station encounter at several km/s, which would make the extraction of the charge difficult. Of course, it's possible to have intersecting orbits, but this way, the pods won't meet four stations, and not always (but periodically) would have station encounter.

2.) As Buldelu pointed out, the system have limited supply of electrons, so it would become drained.

3.) The Moon, the Sun, and other bodies would slowly perturbate the orbits of the collecting pods, making them to miss stations, collide with them, have irregular orbits, or even deorbit. To prevent this you would need stationkeeping engines, which probably would mean to much trouble for the whole system.

4.) The stations have to have high work function hull, or spend significant fraction of their time in shadow, otherwise they would build up the same negative charge as the collecting pods. But a shadowy, low orbit would make them exposed to atmospheric drag, or even the away-conduction of the pod's charge.

5.) You would need high voltage systems on the stations (huge capacitors, accumulators, their insulation to protect the other systems.) to convert the sudden shock, which comes from the discharge of one collection pod, into usable, stable DC power supply.

I think, that the semiconductor based photovoltaics (solar panels) would do far better job than this photoelectric system, since they are 'closed cycle' with the electrons, (circulating them, not ejecting them out). Spaceborne photovoltaic farms were imagined decades ago, and even with their problems with the beaming home of the energy, they mean a far more viable option.

I think there are a couple of things which don't check out in your orbiting mechanics

• First, what you want are heliosynchronous orbits (not geostationary) - as you want your captors to receive as much sunlight exposure as possible.

• Secondly, how do your captor probes intersect with the stations? They will be either on exactly the same orbit (meaning that they'll either never meet up at all, or fly in formation all the time) or on different orbits. In the latter case you'll have to deal with intersect velocities in the km/s range, which doesn't seem very feasible for any kind of interaction that doesn't involve pulverising your stations and/or captor probes.