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I have an extremely limited understanding on how many people have been "in space" (at least in orbit around Earth) and how many people go there every year/month/week(?). It could be 1 per year or 100 per week and I would not be shocked by either number.

When some GPS or any other kind of satellite stops working, do they actually send up somebody, sync the ship with the orbit of the satellite and then have the astronaut take a space walk to repair/replace parts?

Somehow, that sounds like a childish, cartoony way of thinking about current space technology. For all I know, they never fix satellites, but just "bite the bullet" of the lost money and launch another similar one to replace it, allowing the old, dead satellite to just fly around until its corpse eventually comes crashing down to Earth?

I have no idea how much it costs to send up one person, or how it's even done practically.

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  • $\begingroup$ space.stackexchange.com/questions/16850/… $\endgroup$ – BowlOfRed Dec 19 '19 at 19:02
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    $\begingroup$ A very large satellite - the International Space Station - has a crew of people living in it who spend much of their time maintaining it. Sometimes they do space walks for this purpose. $\endgroup$ – Organic Marble Dec 19 '19 at 19:24
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Part of what makes satellites expensive is all the R&D, careful manufacture, and extensive testing that goes into them before launch. The end goal is to make them as reliable as possible, so things don't go wrong and require fixing (or at least the probability is minimized). Satellites are typically built with a predetermined lifespan; part of that is represented in the amount of propellant they are provisioned with for on-orbit maneuvering. Life span is also determined by elements that degrade over time or wear out; solar panels are one example of a component that has a finite life due to inevitable degradation. Once a satellite has reached the end of its useful life, it is typically decommissioned and a new satellite takes over.

The issue of servicing a satellite is economics and personal risk. As reliable as spacecraft and launch systems have become, space workers still assume numerous risks the moment they board a spacecraft. Note that with the exception of the Apollo program, no human has traveled beyond low-Earth orbit; most satellites that might be worthy of a servicing mission (communication, weather, navigation) operate in far higher orbits; getting there is significantly more expensive and hazardous than going to LEO. Servicing has to factor in a justification for the risks involved. Beyond that is economics; it works out cheaper to build for a finite lifespan and then launch a replacement than it is to launch a servicing mission (which would, by the way, involve lots of expendable space hardware). There is also the matter of obsolescence. It makes more sense to replace an old satellite with a newer, better model than to maintain one that has become technologically outdated.

There has been one notable exception to this (if you don't count crewed satellites i.e. space stations) - the Hubble space telescope. It was built in the Shuttle age and had a degree of on-orbit serviceability designed in because it could be reached by a re-usable space vehicle (the Shuttle). Even so, servicing missions were still very expensive.

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    $\begingroup$ Informative answer, but maybe worth adding that since Apollo no humans have gone beyond LEO, while communication sats are mainly in much higher — unreachable, unserviceable — orbits. $\endgroup$ – Russell Borogove Dec 19 '19 at 19:18
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    $\begingroup$ A major reason the Hubble was designed to be serviced is that the mirror it used was practically priceless. It was extremely difficult to manufacture, and then had to be carefully transported to the launch site. So carefully in fact, they had to design a special tractor trailer for it, and that trailer had to go well below the speed limit; 5 mph if I remember correctly. It was designed to be serviced because replacing it would be extremely expensive and likely to fail. $\endgroup$ – Ryan_L Dec 20 '19 at 3:59
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    $\begingroup$ Does that mean that the Hubble was the only non-manned spacecraft to ever have been repaired/maintained via spacewalk? $\endgroup$ – vsz Dec 20 '19 at 5:42
  • $\begingroup$ @vsz Not quite. A few other spacecraft have been captured and worked on (generally, returned to Earth) by the Shuttle. $\endgroup$ – ikrase Dec 21 '19 at 7:42
  • $\begingroup$ @ikrase I think the point here is that the Shuttle was the only space launch system which could offer satellite retrieval or on-orbit servicing, but it was very expensive to operate and limited to LEO, which left only a limited number of candidate missions. One notable retrieval mission was in fact an experiment on orbital micro-meteorite impacts which had to be returned to Earth for analysis. $\endgroup$ – Anthony X Dec 21 '19 at 15:46
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With everything in space the answer is complicated. Yes they have sent humans to space to fix or capture satellites but it's usually cheaper to build and launch a new one than fix it in orbit. Though that's not always the case.

For example the Hubble Space Telescope was serviced 5 times in space (1993/4, 1997, 1999, 2002, and 2009). Another time Space Shuttle Discovery recovered two Canadian communications satellites because they had a faulty kick stage that did get them into the right orbit. They were then sold and relaunched. To my knowledge the Space Shuttle was the only vehicle that had the ability to capture and repair/recover satellites in orbit.

I'll try to help with your confusion a little with how many people are launched to space each year. Currently as of writing this there are only two rockets in the world capable of launches humans into Space. Russia's Soyuz and China's Shenzhou. India is currently in development of human spaceflight program and NASA currently rents seats on the Soyuz rocket (for about $81 million per seat) to send it's Astronauts to the International Space Station (ISS). That will change when Boeing's and SpaceX's crew programs come online with in the next year. Usually there are 4 Soyuz launches a year, each carrying 3, but sometimes 2, astronauts each. The number of Astronauts on the ISS fluctuates but we have had a constant human presence on the ISS for 19 years.

Speaking about the ISS, the ISS is pretty much just a really big satellite and over the years it's been upgraded and repaired many times sense it was created. There are many spacewalks each year out of the ISS to either upgrade, repair, or research activities. Sense 1998 there has been 225 space walks.

So in conclusion, yes there are several spacewalk a year but they have in the recent years been focused on the ISS. If a satellite operator wants to pay for a crew of astronauts to fix a satellite they could, it would be hard sense the only vehicle that could do something like that (the Space Shuttle) was retired back in 2011. So usually they are deemed a loss and a new one is built and launched.

If you're looking for some resources about space exploration than for me the best at breaking complex topics down is Everyday Astronaut on Youtube, another channel that is good is Scott Manley who will talk about more current events. If you have any questions just reach out.

Scott Manley YouTube

Everyday Astronaut YouTube

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  • $\begingroup$ "Space Shuttle was the only vehicle that had the ability to capture and repair/recover satellites in orbit" - this statement is not entirely true. Buran was designed with this particular feature in mind, thus it had that ability as well; but it actually never flew manned. $\endgroup$ – Sergiy Lenzion Dec 19 '19 at 21:35
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    $\begingroup$ @LeoS a fully operational Buran never flew. $\endgroup$ – Organic Marble Dec 19 '19 at 22:48
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    $\begingroup$ @LeoS true, but sense it never made it out of testing and only flew once I didn't include it. It would technically it would be better than the Shuttle sense it wouldn't need cosmonauts on board for a recovery sense it could be flown remotely. $\endgroup$ – SCLA Seth Kurkowski Dec 20 '19 at 3:48

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