Sitting on top of enough explosive stuff to send a heavy weight into orbit at a high speed is dangerous, and that has cost lives in the space program. Re-entering the earth's atmosphere, effectively imitating a meteor as it burns up owing to the translation of the aforereferenced kinetic energy into heat is also dangerous and has taken lives. But increasingly, just sitting there in a sealed box floating above the air far away from everything is becoming as dangerous as it sounds owing to an increased amount of space litter, and earlier this month another event has contributed what experts say is a "not insignificant amount" of litter to the problem.
The Russians recently launched a large rocket intended to put into orbit a couple of communication satellites, but the rocket stopped working on the way up, floated around for several days, and then exploded, creating an arc of new debris that shares orbital space with lots of satellites and the International Space Station. Apparently, similar events in recent years have led to a situation in which the ISS regularly adjusts its orbit to avoid space junk.
It is important to note that this recent explosion did not produce an imminent threat, but over time the situation becomes worse as more debris is added to the mix.
As of Tuesday evening, there were no orbital debris threats to the space station requiring any action, according to Josh Byerly, a NASA spokesperson.
The 450-ton complex can change its orbit, when necessary, to avoid individual pieces of space debris. The maneuvers have become more common since 2008 after a Chinese anti-satellite test and the high-speed crash of two satellites collectively sent approximately 5,000 chunks of space junk into the paths of spacecraft in low Earth orbit.
The Oct. 16 breakup marked the third explosion since 2007 of a Breeze M stage left with partially-full propellant tanks after a launch failure.
Each of the previous Breeze M breakups in 2007 and 2010 produced about 100 pieces of debris, according to NASA's orbital debris program office.
Tracking equipment is said to be pretty good at finding debris that is "large" (tennis size or more) but most of the debris is small (bug-size). The small stuff acts like an erosive material when hitting things like the ISS, but larger objects would be more of a problem. "Erosion" can be mitigated against with "bumpers" that absorb the effects, but solar panels, antennas, etc. have to be exposed and are thus subject to damage by even small particles.
If a largish object hits something like a satellite or the ISS,
and breaks it apart into bits, then more objects are in orbit to hit other things. There is a thing called the Kessler Syndrome whereby the objects from one collision hit something else, which then breaks up, and so on and so forth until finally there is nothing large left, all the satellites are destroyed, and there is so much debris in space that we have to not bother with that whole satellite thing any more until the debris clears. The lower level debris will clear relatively quickly (decades or centuries) because of drag on the bits of the atmosphere it will encounter, but debris at higher altitudes will take thousands of years to clear.
Which gives me an idea. Dyson spheres are hypothesized structures that we assume (guess) intelligent technological beings would eventually built; they are big giant solar collecting devices surrounding other suns in other lands that would be built to maximally exploit the star's energy. These, it is hypothesized, would be detectable, as they would have a special signature astronomers should be able to see.
But really, if we want to assume that other intelligent beings are like us, then perhaps we should be looking for planets with Kessler Blankets. A Kessler Blanket is what I would call the blanket of debris, much of it metallic or consisting of blobs of space rocket fuel and such, surrounding any planet with human-like (i.e., unimpressive) intelligence. The Kessler Blankets would have been deposited during the early decades of space exploration during which time the Xlings ruin the space into which they are attempting to expand, as per usual.
Kessler Blankets. The new Dyson Spheres.
Look for Kessler Blankets, eh? Dyson spheres have a fairly clear observational signature: size of a red giant or supergiant, but a temperature in the infrared (several hundred K).
It's not obvious (to me, a non-astro physicist) that a planet with a Kessler blanket has a clear signature at all. Maybe one of the astro's can point out what I'm missing below :-)
A populated small rocky planet (found via long-term transit observations) in its star's habitable zone will have an IR temperature around 300 K, just like Earth (i.e. an atmosphere with a moderate enough greenhouse effect to support liquid water).
Add a thin blanket of metallic fragments and organic vapor, and what do you get? Maybe a marginal difference in [Fe/O] or far-IR rovibrational states from the rocket fuel. But will that difference be outside the normal statistical variation of our full sample of such planets? Will the [Fe/O] signal even be above instrumental noise?
@Michael: Metallic debris would sporadically reflect radio waves in certain frequency ranges that a naturally occurring ionosphere would not. It's the same physics that prevents wi-fi signals from propagating through metal walls. You'd need a very sensitive telescope covering a wide enough frequency range to see it (and I'm not sure any such telescope or suite of telescopes exists on Earth), but the net effect would be a certain fuzziness of the object in certain wavelength bands.
@Eric: Thank you! That's why I'm not an astrophysicist :-) It makes good sense, and is a potentially measurable signal: different apparent diameters as a function of wavelength. It might even be something the EHT would (in principle) have the resolution to detect.
Stanislaw Lem's satirical "The Star Diaries" mentiones that all systems with advanced civilizations will have suns with lots of cybernetic junk orbiting them after being dumped in graveyard orbits, loudly complaining about their plight in the radio band.
The time window seems awfully small. Artifacts/features lasting only a few thousand years aren't really very useful for ETI hunting.
I'm assuming that there is a relatively effective and efficient technology for dealing with orbiting junk which we haven't yet come up with yet.
BTW: I also agree with an Asimov story (can't remember which one) with respect to looking for radio transmissions. Pretty much pointless since the time between discovering radio and deciding that high-power omni-directional broadcasts are a stupid way of communicating is almost certainly quite short.
And I'm ignoring attenuation.
The thing is, I assume that "intelligent beings" that develolp space travel will almost always develop space junk, and eventually a Kessler blanket. So, although they may last only a few thousand years, they will be very common. Most "intelligent being's" will wipe themselves out before they get Dyson spheres. It's a numbers game. I'm betting on the idiots. Hard to lose that way!