Moon

[Amadeus]

Does anyone else think that slamming satellites which have reached the end of their useful life into the moon is nothing less than pollution? I'm disgusted that we (mankind) seem to believe that pollution is acceptable.

[Fallout]

hehehehehehe. I don't know you, but I know you have to be joking! I too felt sorry for the moon people, but apparently their scrap metal business is doing well, and the cheese the ground is made from tastes better with silicon circuitry mix in. :D

[tigersaw]

Its not like we can bring them home and recycle them

[savage86]

Hey at the end of the day the cheapest and easiest way will win.

[EssexDave]

Surely letting them crash into the Earth and burn up in the atmosphere would be a more favourable?

Incineration has always been better than land dumps :p

[Sir Trev]

You're talking about the Ebb and Flow satellites that were orbiting the moon? I can see the argument for deliberately crashing them into a specific place instead of them possibly contaminating somewhere like the Apollo sites. It makes even less sense to have them loaded with extra fuel to bring them quarter of a million miles back to earth for a burn-up re-entry in our atmosphere. Not ideal but seems reasonable as long as it does not start to happen every day.

[Wideboy]

The Apollo sites are in Hollywood though?

[daveyrach]

Could they not have had them just float off into the great abyss that is space?

[MisterTommyH]

Would need to carry extra fuel to escape the moons gravity once it's settled into orbit.

[Spank86]

Surely letting them crash into the Earth and burn up in the atmosphere would be a more favourable?

Incineration has always been better than land dumps :p

I think it's what the bits hit on landing that concerns people with that method.

[Owenski]

I thought those things in orbit are not orbiting in a perfectly parallel fashion to the earth's surface, they are all falling very slowly losing altitude as they orbit when they'll eventually loose enough momentum and gravity will win.
When salilites orbiting earth loose power they burn up on re-entry but the ones going around the moon don't have to penetrate an atmosphere and thus crash down.

I don't think its as much of a choice as it is an inevitability.

[MisterTommyH]

Yeah, man-made satellites are generally on a decaying orbit. Lots of them fall out of their orbit and get burned up due to the earths atmosphere, although larger objection sometimes make it through (there was something not too long ago I think).

It will be the same for the moon except there is no atmosphere for it to burn up in... therefore it will reach the surface... This is just NASA deciding where it hits rather than letting physics decide.

[Spank86]

Mir wasnt it?

[LankyIanB]

Satellites around the earth are slowed by the drag of passing through the outer limits of the earth's atmosphere. Where the earth's atmosphere ends depends on solar conditions, the atmosphere expands and contracts by up to 100km.

The idea is that as satellites run out of energy they should burn up on re-entry but not all do... If it's a decent size, the descent will attempt to be controlled and planned to aim for a big uninhabited area (pacific ocean). Some satellites are in very stable orbits and are expected to stay up for another couple of centuries.

The moon is about 250,000 miles from earth so there's no atmospheric drag. According to measurements the moon is getting further away from earth, it's "stealing" energy from earth and gaining energy in its orbit.

As to the two satellites. Getting them out of moon orbit would require extra fuel, fuel is weight, you don't want it. The more mass you have, the more inertia you have to deal with, which means more fuel is required to change direction or acceleration. You end up having to carry more fuel because of the extra fuel, which then needs more fuel..... and don't forget you need to launch the whole thing into orbit from earth. Big satellites need big launchers which cost more....

Leaving them in Moon Orbit, just gives an extra hazard to the next mission(s) to go there. So we're back to big uninhabited areas again!

Anyway, the iron chicken probably needs a few spares by now....

[keith_d]

While satellites in a stable orbit around the moon are not affected significantly by atmospheric drag. Their orbits still gradually wander because of small variations in gravitational forces acting upon them. When they run out of fuel the satellites cannot correct for these small variations and become a hazard for future missions. So they either need to go up or down.

It costs around $10,000 to lift every pound into orbit, so adding a rocket motor to lift the satellite out of the moon's gravitational field isn't going to be a real winner.

It's much cheaper to use the last of the maneuvering fuel to push it into an orbit that ends with a bang. That doesn't mean driving it straight down onto the lunar surface. Just choosing an orbit which becomes more and more eccentric until it intersects the lunar surface.

[widepants]

The Apollo sites are in Hollywood though?
bugger! I thought they were in area 51