eclipse help, need help with the science Options

[jerusalem7227]

Was sitting around dreaming up stuff for campaigns and runs for the group and wondered if it was 'possible' to create a man-made solar eclipse?

Well, it would be possible of course, but what size would the object have to be to have noticable effect and how high up in the atmosphere would it have to be?

Obviously, the effects would depend on how long the area stayed in the umbra(shadow) of the object...but would there be any other reasons to use it?
How would having an object like that in low earth orbit effect satellites looking down?

any help with the science would be much appreciated.

[tarbrush]

How big a shadow do you want to cast?

[DuctShuiTengu]

Well, given that what you've requested is an eclipse, let's start with looking at the moon.

The moon has an average diameter of 3,474 km and is 384,403 above the earth. In order to cause a total eclipse for an equally large portion of the planet's surface, we'd need to maintain this ratio: 0.00903739 km of diameter per km of altitude. To have as large a portion of the planet's surface experience a partial eclipse, we'd also need to maintain the same distance from the earth to this satellite as from the earth to the moon (lower altitude means a smaller area with a partial eclipse).

So, with that being established, let's look at orbit heights:

Low Earth Orbit is anywhere from 160 to 2000 km up. This would require a satellite somewhere between 1.45 and 18.07 km in diameter. However, to maintain that orbit, it needs to be moving 8 km/second

Going out to Geosynchronous Orbit puts us 35,786 km above the earth. A satellite placed here would need a diameter of 323.41 km. This would, however, get the necessary velocity down to 3 km/second.

Altitudes between LEO and GEO will result in sizes and velocities in between the above values, while moving further from the plannet will result in larger and larger satellites being needed. Likewise, changes in our standards of what's enough of an eclipse will cause corresponding changes in the size needed.

[jerusalem7227]

thank you, that was exactly what I was looking for

[Wacky]

Low Earth Orbit is anywhere from 160 to 2000 km up. This would require a satellite somewhere between 1.45 and 18.07 km in diameter. However, to maintain that orbit, it needs to be moving 8 km/second

The nice thing about this scenario is that the object can be simply a dense, but thin material folded up in a small area that gets up to this speed before expanding to the desired size.

Since you're not having to deal with wind drag, the folding should be less of a problem (assuming your equipment works right, doesn't hit another satellite, or gets hit by a bit of space debris).

Sign--

Wacky

[Khyron]

The giant space umbrella.

[Draco18s]

Since you're not having to deal with wind drag, the folding should be less of a problem (assuming your equipment works right, doesn't hit another satellite, or gets hit by a bit of space debris).

You would in LEO.

Objects in LEO encounter atmospheric drag in the form of gases in the thermosphere (approximately 80-500 km up) or exosphere (approximately 500 km and up), depending on orbit height. LEO is an orbit around Earth between the atmosphere and below the inner Van Allen radiation belt. The altitude is usually not less than 300 km because that would be impractical due to the larger atmospheric drag.