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Re: Static electricity and space




On Wednesday, Mar 12, 2003, at 13:16 US/Central, William Leijenaar 
wrote:

> Hi AMSATs,
>
> When I am right, with the constant radiation of the sun ,satellites 
> and other space stations/vehicles like ISS space-shuttle etc should be 
> static charged.
>
> When the space shuttle connects to the ISS this would give a huge 
> spark, or they have some kind of protection for it ???

It would, and they do.  EVA is actually fairly hazardous on ISS for 
this very reason, and there are special ion emitters on the station 
they can turn on to cancel out the charge temporarily while they are on 
EVA.  This problem will get progressively worse as the station gets 
larger and more solar panels and trusses are added.

On top of that, vacuum is about the best insulator there is .. if 
you've seen a high voltage vacuum capacitor you know what I mean.  
There's no arcover in space, so when you connect two large bodies with 
a very large voltage differential between them, you don't get a spark 
like you do on earth, you get a HUGE current spike at the point of 
contact.  Enough of these will do significant damage to docking probes, 
etc., so likewise, they kill the charge on the station or at least 
match it to the charge on the shuttle before they dock ..

> Then with physics in mind: when the earth has a static charge, and a 
> satellite on the ground could be give the same charge they will repel 
> each other (in other words the satellite will go up).
> Actually I never seen a satellite launched like this, so why does it 
> not work ???

I think there is some electric field repulsion acting on spacecraft in 
orbit, but it's a *small* force, more of a nuisance orbit perturbation 
than anything else.  Between solar radiation pressure and Yarkovsky 
effect, though, this effect sort of gets lost in the noise .. and it's 
definitely far too small to exert anything like the kind of delta-V 
required to get a sat into orbit ..

----
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