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https://www.nasa.gov/mission_pages/station/research/benefits/cubesat https://www.nasa.gov/mission_pages/station/research/benefits... Sounds like in most cases

https://www.nasa.gov/mission_pages/station/research/benefits/cubesat https://www.nasa.gov/mission_pages/station/research/benefits... Sounds like in most cases the satellites don't have any propulsion of their own, and are "ejected" onto their orbit from the ISS. Put simply, they get thrown out. I'm sure some checks are done of the orbital mechanics to avoid any risk of a later collission, but keep in mind that the ISS makes frequent course corrections to stay in orbit, and at this low of an orbit drag is also a factor, so simply being a smaller craft will cause different forces to push you onto a different path. Obviously this means you have very little choice in your orbit, but for many small satellites this isn't a concern. EDIT: To answer your "use it as a garage" point, the answer is that it's way too impractical. In orbital mechanics, drifting apart from something is far easier than getting closer to it, and space is really, really big. Plus keep in mind that you need to not only be in the same place at the same time, but you also need to be moving at the same speed (relative velocities in LEO can quickly reach the order of kilometers per second).

filereaper 6y ago
I imagined deploying a net of some sort to get close but not extremely close. But I guess the high velocities mean you need a really strong and light net and the rapid deceleration might damage the satellite anyway.
- jiofih 6y ago
  The ISS orbits at 400km altitude and 27000km/h, while many small satellites will orbit lower - I suppose this is what makes it possible to “drop” a non-propulsive satellite from the ISS like the one in the article. As their orbit decays, they would actually need tons of fuel to accelerate and raise their orbit to reach the station, it’s totally impractical. EDIT: not geostationary
  - viklove 6y ago
    That doesn't make any sense. If you want to orbit at a lower speed, you need to increase your altitude. Geostationary orbit is at 35,000+ km, while the ISS orbits at ~400 km.
  - madpata 6y ago
    Don't you mean much higher? Like at 36MM/36,000km?
  - hnuser123456 6y ago
    Geostationary orbits are much higher altitude to achieve lower orbit speeds. Gravity is stronger closer to the surface. But they'd still need a lot of fuel to slow down, to drop lower to the ISS' orbit, and then they'd be on an elliptical, and need even more to circularize and rendezvous. edit: I'm the third one to say this in a span of a minute, sorry.
  - gpav 6y ago
    Instead of geostationary, I think you mean low earth orbit (LEO). There is a link to the Wikipedia article on LEO in an adjacent comment. A circular geostationary orbit is at an altitude of 22,236 miles/35,786 kilometers. https://en.m.wikipedia.org/wiki/Geostationary_orbit https://en.m.wikipedia.org/wiki/Geostationary_orbit
  - deleted 6y ago
    [deleted]
- simonh 6y ago
  Rifle bullet speed is a relatively small delta for orbiting craft, it goes up quite a few orders of magnitude from that. Pretty much anything you encounter that you didn't specifically try very hard to match orbits with is going to blast right through a net. There were studies on using the Shuttle to repair satellites, but aside from the maintenance mission on Hubble those plans were shelved. The cost of a new satellite was generally a lot less than the cost of a shuttle mission dedicated to repairing it, and it would often need to be dedicated due to the requirement to match orbits. Even if the ISS released a smallsat, which it does from time to time, that doesn't help you. By the time you need to do maintenance on it, the cubesat will have dropped into a much lower orbit due to upper atmosphere effects. The safest, and practically perhaps the only viable way for the ISS to do maintenance on orbital instruments is if they stay attached to the ISS.
  - bzbarsky 6y ago
    > it goes up quite a few orders of magnitude from that Sorry to be pedantic, but modern rifle muzzle velocities are in the 1.2km/s range. Escape velocity in LEO is 11.2km/s, so your maximal closing speed is ~22.4kms. Which is maybe 1.3 orders of magnitude difference, not "quite a few". Orders of magnitude are big. For the rest, you are right of course: we're talking closing speeds that can easily be one order of magnitude higher than rifle bullets (or armor-piercing tank projectiles, for that matter; those are at 1.7km/s or so).
    - dheera 6y ago
      I guess it depends if you operate in base 2 or base 10.
      - hinoki 6y ago
        Naturally, you should use base e, which gives about 3 orders of magnitude.
    - db48x 6y ago
      What matters in a collision isn't velocity, it's momentum. Momentum is ½mv². There's a lot of orders of magnitude just in the mass, but the velocities add up a lot faster than you'd think too. I'd say there's around 10 orders of magnitude between the momentum of a rifle bullet and the momentum of a communications satellite at escape velocity.
- LASR 6y ago
  It would be like trying to catch a hypervelocity meteor with a net. It would go right through any kind of reasonable(or even extreme) net material. Keep in mind that when the atmosphere is used to "catch" a returning spacecraft, it takes several minutes of sustained deceleration over thousands of miles, and in the process the craft gets extremely hot due to compressive heating and friction with air. When you have satellites on different orbital planes, it can be twice as hard due to relative velocities.
baby 6y ago
Leo?
- filereaper 6y ago
  Low Earth Orbit https://en.m.wikipedia.org/wiki/Low_Earth_orbit https://en.m.wikipedia.org/wiki/Low_Earth_orbit
- deleted 6y ago
  [deleted]
ryandrake 6y ago
Yea a few Kerbal Space Program sessions were enough to convince me that it's totally impractical to have a "collector" spacecraft that just goes around collecting old satellites and space trash in different orbits.
- TeMPOraL 6y ago
  KSP gave me the exact same impression, but there's one thing I wonder about: with sufficiently smart global optimization algorithm, maybe a collector craft could approach and collect several targets on a low Δv budget? It's not something you could do manually, but space has also this nice property that you can predict trajectories accurately far in advance, so it may be amendable to optimization. Wonder if there's a paper somewhere that computed possible Δv requirements for a collector if you squeeze your flight plan very tight. (Also in-orbit refueling will change this equation a lot. You could keep a bunch of such collectors continuously in space, and wait for the trash to align right. There's no hurry.)
  - gmueckl 6y ago
    Assuming you manage to grab a hold of debris without ripping off even tiny parts, how would you dispose of it? You'd need to deorbit it and you need a working engine for that. So a reusable collector doesn't seem like a plausible concept to me.
    - tomc1985 6y ago
      Could an astronaut grab a smaller satellite and simply chuck it towards the sun? Would it have enough velocity break out of earth orbit or would it just get stuck in some really large, wide, graveyard orbit? If not the sun then maybe the earth? That would be a fun spacewalk.
      - DavidSJ 6y ago
        The ∆v to escape Earth orbit is generally quite large, and it's far, far greater still to collide with the Sun (though this wouldn't normally be considered necessary). In comparison, a deorbit burn is usually relatively inexpensive.

filereaper 6y ago

I imagined deploying a net of some sort to get close but not extremely close. But I guess the high velocities mean you need a really strong and light net and the rapid deceleration might damage the satellite anyway.

jiofih 6y ago
The ISS orbits at 400km altitude and 27000km/h, while many small satellites will orbit lower - I suppose this is what makes it possible to “drop” a non-propulsive satellite from the ISS like the one in the article. As their orbit decays, they would actually need tons of fuel to accelerate and raise their orbit to reach the station, it’s totally impractical. EDIT: not geostationary
- viklove 6y ago
  That doesn't make any sense. If you want to orbit at a lower speed, you need to increase your altitude. Geostationary orbit is at 35,000+ km, while the ISS orbits at ~400 km.
- madpata 6y ago
  Don't you mean much higher? Like at 36MM/36,000km?
- hnuser123456 6y ago
  Geostationary orbits are much higher altitude to achieve lower orbit speeds. Gravity is stronger closer to the surface. But they'd still need a lot of fuel to slow down, to drop lower to the ISS' orbit, and then they'd be on an elliptical, and need even more to circularize and rendezvous. edit: I'm the third one to say this in a span of a minute, sorry.
- gpav 6y ago
  Instead of geostationary, I think you mean low earth orbit (LEO). There is a link to the Wikipedia article on LEO in an adjacent comment. A circular geostationary orbit is at an altitude of 22,236 miles/35,786 kilometers. https://en.m.wikipedia.org/wiki/Geostationary_orbit https://en.m.wikipedia.org/wiki/Geostationary_orbit
- deleted 6y ago
  [deleted]
simonh 6y ago
Rifle bullet speed is a relatively small delta for orbiting craft, it goes up quite a few orders of magnitude from that. Pretty much anything you encounter that you didn't specifically try very hard to match orbits with is going to blast right through a net. There were studies on using the Shuttle to repair satellites, but aside from the maintenance mission on Hubble those plans were shelved. The cost of a new satellite was generally a lot less than the cost of a shuttle mission dedicated to repairing it, and it would often need to be dedicated due to the requirement to match orbits. Even if the ISS released a smallsat, which it does from time to time, that doesn't help you. By the time you need to do maintenance on it, the cubesat will have dropped into a much lower orbit due to upper atmosphere effects. The safest, and practically perhaps the only viable way for the ISS to do maintenance on orbital instruments is if they stay attached to the ISS.
- bzbarsky 6y ago
  > it goes up quite a few orders of magnitude from that Sorry to be pedantic, but modern rifle muzzle velocities are in the 1.2km/s range. Escape velocity in LEO is 11.2km/s, so your maximal closing speed is ~22.4kms. Which is maybe 1.3 orders of magnitude difference, not "quite a few". Orders of magnitude are big. For the rest, you are right of course: we're talking closing speeds that can easily be one order of magnitude higher than rifle bullets (or armor-piercing tank projectiles, for that matter; those are at 1.7km/s or so).
  - dheera 6y ago
    I guess it depends if you operate in base 2 or base 10.
    - hinoki 6y ago
      Naturally, you should use base e, which gives about 3 orders of magnitude.
  - db48x 6y ago
    What matters in a collision isn't velocity, it's momentum. Momentum is ½mv². There's a lot of orders of magnitude just in the mass, but the velocities add up a lot faster than you'd think too. I'd say there's around 10 orders of magnitude between the momentum of a rifle bullet and the momentum of a communications satellite at escape velocity.
LASR 6y ago
It would be like trying to catch a hypervelocity meteor with a net. It would go right through any kind of reasonable(or even extreme) net material. Keep in mind that when the atmosphere is used to "catch" a returning spacecraft, it takes several minutes of sustained deceleration over thousands of miles, and in the process the craft gets extremely hot due to compressive heating and friction with air. When you have satellites on different orbital planes, it can be twice as hard due to relative velocities.

baby 6y ago

Leo?

filereaper 6y ago
Low Earth Orbit https://en.m.wikipedia.org/wiki/Low_Earth_orbit https://en.m.wikipedia.org/wiki/Low_Earth_orbit
deleted 6y ago
[deleted]

ryandrake 6y ago

Yea a few Kerbal Space Program sessions were enough to convince me that it's totally impractical to have a "collector" spacecraft that just goes around collecting old satellites and space trash in different orbits.

TeMPOraL 6y ago
KSP gave me the exact same impression, but there's one thing I wonder about: with sufficiently smart global optimization algorithm, maybe a collector craft could approach and collect several targets on a low Δv budget? It's not something you could do manually, but space has also this nice property that you can predict trajectories accurately far in advance, so it may be amendable to optimization. Wonder if there's a paper somewhere that computed possible Δv requirements for a collector if you squeeze your flight plan very tight. (Also in-orbit refueling will change this equation a lot. You could keep a bunch of such collectors continuously in space, and wait for the trash to align right. There's no hurry.)
- gmueckl 6y ago
  Assuming you manage to grab a hold of debris without ripping off even tiny parts, how would you dispose of it? You'd need to deorbit it and you need a working engine for that. So a reusable collector doesn't seem like a plausible concept to me.
  - tomc1985 6y ago
    Could an astronaut grab a smaller satellite and simply chuck it towards the sun? Would it have enough velocity break out of earth orbit or would it just get stuck in some really large, wide, graveyard orbit? If not the sun then maybe the earth? That would be a fun spacewalk.
    - DavidSJ 6y ago
      The ∆v to escape Earth orbit is generally quite large, and it's far, far greater still to collide with the Sun (though this wouldn't normally be considered necessary). In comparison, a deorbit burn is usually relatively inexpensive.