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90 votes

Is the SpaceX Falcon Heavy payload (a Tesla car) space junk?

No, because it is not in Earth orbit First the payload does have a purpose: it is a boilerplate, and those have a purpose, namely to "test various configurations and basic size, load, and handling ...
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78 votes
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Shouldn't space junk fall back to Earth on its own? How long will take for a ~1 cm piece of junk in LEO to fall back to Earth on its own for example?

It depends on the altitude. Here is a chart from ESA and UNOOSA. Basically, anything under 500 km will fall relatively quickly, maybe 25 years. Everything under 800 km should fall within a century or ...
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75 votes
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Is Nibiru real or totally science fiction?

Nibiru is fiction. Nibiru, a purported large object headed toward Earth, simply put - does not exist. There is no credible evidence - telescopic or otherwise - for this object's existence. There ...
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74 votes
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Why would a box full of 1cm balls released into LEO be so scary to an engineer supporting the ISS? - (Updated)

Well, gee, this question may as well have my name printed directly on it! Spacecraft protection from the orbital debris threat comes in two flavors: Shield and withstand Detect and avoid To start, ...
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63 votes

Is the SpaceX Falcon Heavy payload (a Tesla car) space junk?

Yes, it's space junk: after about 6 hours, the second stage will stop working and there will be no way to change the trajectory of stage and payload. So it's a non-functional satellite, i.e. junk. An ...
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60 votes
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Why haven't more spacecraft/satellites been hit by debris?

They are hit all the time. It just hasn't been critical. So far. Looking at the outside portion of the Hubble WFPC2 camera after it was returned, I saw a huge number of large and small pits in the ...
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51 votes
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Are pictures of Earth' space junk realistic?

No, it's entirely unrealistic. The Earth is very large by the standards of what you deal with in day to day life -- it's about 13 million meters in diameter. Satellites are typically only a few meters ...
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47 votes

BBC: "A rocket launched by Elon Musk's space exploration company is on course to crash into the Moon and explode." Will it really explode?

It depends on how you define "explosion". Most generally, it merely describes something that breaks into pieces violently. Astronomical impact events can generate explosions simply from ...
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44 votes

Is the SpaceX Falcon Heavy payload (a Tesla car) space junk?

Footnotes: ${}^1$ That the term "Space Junk" (as used in this answer and which is probably the right answer) has a different generally agreed meaning in spacecraft lingo than just plain "Junk" has ...
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42 votes
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Is it possible to observe space debris with Binoculars?

Yes, I've done it myself in my backyard in suburban Houston. During a spacewalk in ISS increment 50, an MMOD shield intended for the axial port of Node 3 was lost. It's visible in this video ...
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41 votes

Is Nibiru real or totally science fiction?

The name Nibiru does appear in science fiction. However, the stuff to which you refer is not science fiction. It's just baloney, malarkey, or "fake news." According to Wikipedia's article Nibiru ...
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40 votes
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Why aren't there any active space debris removal systems implemented currently?

Removing debris costs money. Even with many words like "efficient", "low-cost", and so forth, a system capable of removing a significant amount of space debris still involves a budget requirement ...
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38 votes
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Do things get dirty in space?

Spooky This one is subjective. To some, just finding an abandoned spaceship would be spooky. I'll say there's probably not a lot that has to happen to evoke this feeling. Rusted Actually, unless ...
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37 votes
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Why choose to crash the Apollo lunar lander ascent stage after it ascended?

First off, lunar orbits tend to be unstable due to mascons (mass concentrations, which are places of higher density produced by impacts with the moon that cause it to have a non-uniform gravity field)....
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36 votes

Flung debris in lunar landing

Great question. The exhaust velocity from typical landing engines is about 3 km/s. You can imagine good-sized particles being accelerated to a significant fraction of that, say 1 km/s, which is the ...
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36 votes

Are pictures of Earth' space junk realistic?

The "actual data" is that for every one of their dots, there is probably a real debris fragment, the mix of satellites/rocket bodies etc is probably broadly right, and so on. However, the ...
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35 votes

India just shot down a satellite from the ground. At what altitude range is the resulting debris field?

The apogee/ perigee of 2019-006A, the object likely shot down, was 260- 282 km, pretty low. Some of that debris could be quite a bit higher, but most of it will be lower, and all of it will have a new ...
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35 votes
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Should man-made satellites feature an intelligent inverted "cow catcher"?

...adjust the angle of the cow catcher to deflect earthward The catcher could be coupled in a way that would allow it to absorb impact gradually by continuous springs. The problem with this is that ...
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34 votes
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What would be the first noticeable consequences to the general public of widespread satellite destruction?

What would you notice first? Satellite navigation: immediately (depending on how often you use satnav) TV: immediately (depending on how often you use TV). Even if you don't use satellite TV ...
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31 votes

Why would a box full of 1cm balls released into LEO be so scary to an engineer supporting the ISS? - (Updated)

There's a few pieces of information that are needed to explain why one might be wary of 1 cm objects: Objects as small as 4 inches (about 10 cm) can be seen by radars or optical telescopes on Earth ...
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30 votes

BBC: "A rocket launched by Elon Musk's space exploration company is on course to crash into the Moon and explode." Will it really explode?

I think it's worth looking at how much energy that rocket is going to be carrying. Plugging the 4 tonnes and 5000 mph figures into an Online calculator we find that the impact will carry close to 10 ...
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29 votes
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Why is the ribbon of decommissioned geosynchronous satellites skewed?

The apparent source of the data (as it is linked in the source linked in the description of the author of this map) is http://apps.agi.com/SatelliteViewer/ In this animated view you can see that ...
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28 votes

Shouldn't space junk fall back to Earth on its own? How long will take for a ~1 cm piece of junk in LEO to fall back to Earth on its own for example?

Space debris poses a real risk for spacecraft in LEO. From the Technical Report on Space Debris UN Committee on the Peaceful uses of Outer Space (Table 5), a satellite in orbit can expect to collide ...
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28 votes
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Did any Columbia debris continue orbiting Earth?

No. Even the highest ballistic coefficient debris (engine turbopumps, etc) only made it to Louisiana. Heavier objects with higher ballistic coefficients, a measure of how far objects will travel in ...
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27 votes
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What is the largest piece of space debris volumetrically?

Initial and Bonus Answer: With a volume of 609.31 M^3 and an empty mass of 15,500kg (13,500 kg empty weight plus 2,000kg for the attached Instrument Unit), J002E3 is Apollo 12's S-IVB stage (...
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26 votes
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What is the biggest piece of space junk?

The UCS has a list of satellites which can be sorted by launch mass. The top 10 is mostly spy satellites for which it's difficult to determine if they're active or defunct. The heaviest satellite ...
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25 votes

How would blockchain be integrated into spaceflight? Have any methods been proposed yet?

Blockchain is a very poor solution to a specific problem: achieving ledger consensus among a large number of agents when there is substantial incentive to corrupt the record, and the entries in the ...
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24 votes

Are most Earth polar satellites launched to the South or to the North? And why?

There's no real distinction once you're in orbit; a northbound LEO orbit at a given longitude at a given time is a southbound orbit at nearly the opposite longitude 45 minutes later. The rotation of ...
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23 votes

Is there a lot of space trash at the Earth-Moon Lagrange points?

The Lagrange points L1, L2 and L3 are stable in prograde- and retrograde direction, but unstable on the radial axis. That means any object on these points will drift away in radial direction unless it ...
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23 votes
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How does a spacecraft such as Soyuz detect when it's on collision course with an object?

Spacecraft rely on information from earth to avoid space debris, they don't have instruments for scanning and detecting debris. There's a few reasons for this: Power: most spacecraft don't have ...
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