Space debris question

Most of it is jettisoned before it reaches orbital speed, so will fall back to earth, the faster parts will burn up, slower parts fall all the way back to the surface.
Debris in low earth orbit will have their orbits slowly decaying and eventually re-enter the atmosphere and burn up, larger and more hardy parts reaching the surface. This also happens to satellites in low orbits once their maneuvering fuel is expended.

That leaves debris, including dead satellites, in medium and high orbits. These orbits are affected by tidal forces. Over time they are forced into orbits with periods that resonate with the Moon orbit. (Saturn's rings are similar affected by the moons, leaving gaps.)

All in all, it has become quite tricky to launch satellites. Especially into geosynchronous orbits, as they have to pass through most of the debris out there.

With the Apollo missions, little to no debris was left in space.


1st Stage was jettisoned and crashed into ocean.

2nd Stage was jettisoned while still suborbital and mostly burned up in atmosphere and what was left crashed into ocean.

3rd Stage set them on a trajectory to crash into moon. (a minor course correction burn after the CSM/LM stack separated sent them around the moon instead of into it.

The only things left in space are a couple of the Lunar Module Ascent sections and one Lunar Module Descent section.

Apollo 10 took the Lunar module down to about 15km, discarded the descent section and came back up to the 60km lunar parking orbit. It was a dress rehearsal for to following Apollo 11 lunar landing. That descent stage would still be in a 60x14 km elliptical orbit.

A few of the early ascent modules were sent off out of the Earth/Moon system into a Heliocentric orbit for disposal. All the later ones were deliberately crashed into the Moon so that seismic experiments left behind on previous missions could record the impacts for scientific data.


Everything else was either left on the moon, crashed into the moon, or crashed/landed/burned up in Earth's atmosphere.

That's as far as the Apollo moon missions go.


As far as everything else goes... yeah, there is a LOT of junk up there.

Many earlier satellites were brought fully into orbit by the final launch vehicle stage, meaning that after payload separation this final upper stage also remained in orbit. Many of these stages had cryogenic fuels. Whatever fuel remained in these tanks would eventually boil off and rupture the tanks from overpressurization. This created even more debris.

Modern launch vehicles will have retro firing engines to reduce the upper stage to suborbital on payload separation, or vent off remaining fuel to prevent rupture if it must be left in orbit. Some will separate their payload while still suborbital and the payload itself will have some small engine to complete the final orbital insertion burn.

Most of the stuff in Low Earth Orbit (LEO) will eventually be brought back into Earth's atmosphere by drag forces. Even the ISS needs regular altitude reboosts or it too will eventually reenter the atmosohere. Even space is not a perfect vacuum and even at the altitude of ISS, Hubble and others which you think of as being "in space" is still actually in what is the very upper tenuous reaches of the atmosphere, called the Thermosphere.

How long it takes for this junk to be slowed enough to reenter depends on its orbital height, eccentricity of orbit, and Solar activity (which heats the atmosphere and expands it causing greater drag at greater heights) times vary from a few months, to decades or longer.



I joined the Navy to see the world, only to discover the world is 2/3 water!

I found this to be interesting in relation to the conversation. A piece of what's thought to be the Apollo 12 rocket is still in orbit.

https://en.wikipedia.org/wiki/J002E3

Vanguard 1, launched in 1958, is also still in orbit according to Heavens Above's website.