[amsat-bb] Re: 'Zombie-sat' and the clever orbital dance

[Bruce Bostwick]

On May 25, 2010, at 2:27 PM, Luc Leblanc wrote:

>> The BBC are running the video on their website
>>
>> http://news.bbc.co.uk/1/hi/science_and_environment/10150614.stm
>>
>> 73 Trevor M5AKA
>
>
> They will need a space fly swatter... More seriously some kind of  
> solution will have to be found to discard useless space debris and  
> junk.

It's all in the delta-V.  If you can apply enough to put the perigee  
in the upper atmosphere, the orbit will eventually decay to where the  
object deorbits.  Everything in LEO encounters enough drag to end up  
in the atmosphere sooner or later, whether it's within a year, within  
ten years, or within a hundred years, sooner or later it will fall  
out.  HEO and above, you pretty much have to apply external delta-V to  
get the perigee down far enough.

The problem with dead HEO and GEO sats, and a lot of the GTO booster  
stages that got them there, and all the loose bits of shrouds,  
interstage thrust structures, and so on, is that their perigees are  
far enough above the atmosphere that if left completely alone, they'll  
still be there tends of thousands of years from now, because there  
just aren't any forces acting on them that are strong enough to either  
deorbit them or kick them up to escape velocity and out into solar  
orbit, and the immediate problem with *that* is that at $36k-$550k/ 
kilogram, it's still too expensive to launch much more than new  
working sats to GEO.

If the cost comes down to where it's practical to launch a semi- 
autonomous deorbiting "tug" of some sort to grapple junk and push it  
to a low enough perigee, with some kind of propulsion that can supply  
large amounts of delta-V for a relatively small onboard fuel load,  
then a lot can be done about HEO/GEO junk.  But all of those are big  
ifs, and doing anything like that with our current propulsion tech  
just isn't feasible due to diminishing returns.  You're pretty much  
looking at some kind of antimatter rocket to be able to do that kind  
of job.

"A process cannot be understood by stopping it. Understanding must  
move with the flow of the process, must join it and flow with it." --  
the First Law of Mentat