We are talking about hundreds of CubeSats launched into space in low orbits. But we think about space junk?
It would be sad if we are think in good for humanity and in the end we produce a bad. Seems essential to think about how to recover down CubeSats and add this to the budget.
sorry, I’m a curious man
my hungry are questions
my food responses.
Why does this keep coming up? The whole “space junk” thing is a myth. Orbits are decided upon by the ICU, and the cubesats are less than a foot square in an orbit an order of magnitude larger than the Earth’s equator. We could put up a thousand of them in the same orbit, and there still be miles of space between each one.
A myth? that’s a irresponsible mindset, many years ago people thought that put jump in the ocean it was a good idea, thought the ocean is so big that can withstand all, now it’s too late for that, but it’s not too late to prevent grandchildren have the problem of our space shit.
International treaties place CubeSats in low orbits that naturally decay in a few years. Sadly, my child’s children will never see my CubeSat.
The space junk myth isn’t comparable to the great Pacific Swirl. As I said, we could put up thousands and never make a dent in the space available. And as Snyder pointed out, sats in LEO tend to degrade their orbit and burn up upon reentry in less than 30 years. In fact, eventually pretty much everything humanity has put into orbit will eventually degrade and reenter, because we really aren’t good enough to establish a perfect orbit. Those in GEO will take 10K+ years, but eventually there will be no trace of them either.
If all objects were in different positions on the same precise orbital track, they would not interact. Over time, they will drift into different orbits, because they will be perturbed at different times by lunar and solar tides. Still, while they may gain enough relative velocity to disable each other during a (rare) collision, they probably won’t produce hypervelocity shrapnel.
The problem is that all satellites aren’t in the same orbit, they have different radii and arguments of perigee and ascending nodes; an orbit is described with six parameters, which are shifted by tides and the equatorial bulge and drag. Soon enough, a constellation of satellites all in different and highly inclined orbits to provide approximately complete coverage (perhaps between 60N and 60S) will shift - without stationkeeping thrust those orbits will eventually overlap. Sooner or later, a satellite orbiting northwards will encounter another satellite orbiting southwards, making a spray of shrapnel that can damage other satellites. Look at the wikipedia page about the 2009 Iridium Cosmos collision for the most prominent example of such a collision.
No satellite should be launched if it cannot actively change its orbit, if only slightly to avoid a collision. If a satellite is due to lose that capability, it should be deorbited or recycled. After it smashes into a thousand fragments, those fragments are a thousand times as expensive to collect and deorbit. Without that, in a few centuries the exponentially increasing fragment cloud will form a Saturn-like ring, and space becomes inaccessable.
If centuries seem like a long time, imagine some careless twit doing something a millenium ago that makes your own life impossible. The tenure of earth life in the universe may span billions of years - or we may turn it into a pool of maximum entropy in a thousand. I would rather see the lazy entropy maximizers subject themselves to the treatment first.
BTW, the Iridium Cosmos collision is prominent only because Iridium 33 was in active use at the time. Far more collisions between derelicts go unnoticed, and dozens of pressurized upper stages have exploded and created debris fields. When a solid motor apogee circularization stage completes its burn, combustion stops by exploding a hole in the side of the chamber. That process also creates dozens of small untrackable objects, which can collide with other satellites with far more energy than a rifle bullet.
Yes, space is very very big, but the collision rate is proportional to the velocity and the square of the object density. A collision increases the object density, increasing collision rate, etc. There are tens of thousands of tons of mass up there, going in all directions (though mostly eastward) with 100 times the kinetic energy per gram of a rifle bullet. Google for “Kessler syndrome”. Better yet, read Donald Kessler’s papers.
If all the objects can maneuver, be precisely tracked (within meters) and predicted, and can survive small penetrators, then debris is not a major problem. A much higher density of objects travels down the freeway every day, but they are under control, going at the same speed in the same direction. If any of those restructions are relaxed, problems, if they all relax, carnage. Would you drive on such a freeway if even one of the other drivers had an opaque windshield or lacked a steering wheel and brakes?
The CubeSats do not orbit forever. They eventually get pulled back into the atmosphere and burn up as they fall. This space junk talk is irrelevant.
(First, apologies for reviving an old thread, but I felt I needed to give input.)
Regarding space junk:
All satellites have a limited life.Large satellites generally last 10-20 years; smaller satellites such as cube sats generally last 3-10 years. Calling space junk “irrelevant” because it has a generally accepted practice is not really responsible not accurate.
When a launch license is issued for a satellite, the company launching is contractually obligated to “deorbit” the satellite when it gets down to a certain amount of remaining life, generally about a month. So in a best case scenario, the satellite will run properly for it’s estimated life minus a month, the commands will be sent to deorbit the satellite, and the deorbit will happen successfully. (For Low Earth Satellites they crash the satellite into the ocean after it mostly burns up in the atmosphere. For geostationary satellites the satellite is moved to a “graveyard” orbit about 24000 miles above the earth.)
The thing to note though is THIS IS A BEST CASE SCENARIO. There are 3 general things can cause this not to happen: Equipment failure, collisions, and loss of telemetry.
Equipment failure. Many satellites fail. About 1 in 7 never get operational to start with, either because of launch failures or equipment failures during startup. Of the remaining ones, a tangible percentage fail sometime during their lifespan.
Collisions. Low earth orbit satellites especially can collide with other objects in space. Not only other human made objects in orbit, but rocks and ice as well.
Loss of telemetry. LEO satellites generally need to be sent commands at least a couple times a day, or they will go into “coast” mode. An extended failure of a ground station can cause a situation where they are no longer able to receive commands. This can also be caused by the satellite facing “tits up” where the telemetry receive equipment gets flopped towards space rather than the earth.
In any of these 3 situations, it can become impossible to send the commands necessary to deorbit the spacecraft, and it can become “space junk”.
$.02.