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I was surprised to read NASA's statement that

This (27 May 2020) mission marks the first time since the retirement of the space shuttle in 2011 that humans will fly to the space station from U.S. soil.

I was a little surprised - I was under the impression that this happened much more frequently. E.g. ~ quarterly.

Question

How often do other space vehicles visit the ISS (and what proportion of those visiting shuttles contain humans)?

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    $\begingroup$ What other space shuttles? Only the US ever had manned space shuttles, and that program ended in 2011. $\endgroup$ – Organic Marble May 27 at 20:58
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    $\begingroup$ Space shuttles haven't flown in years. Other (manned towards ISS) rockets were launched primarily from Kazakhstan and not from the USA. $\endgroup$ – Mast May 27 at 21:03
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    $\begingroup$ Space shuttles? Yes. SpaceX rockets? Possibly. But none of the SpaceX rockets towards the ISS were manned before. And that's exactly what you're asking, humans flying to the space station. $\endgroup$ – Mast May 27 at 21:06
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    $\begingroup$ Re, "I considered rockets ≈ space shuttles," Might be reasonable, but I think you'll find that most other people consider "Space Shuttle" to be the name of a specific class of space vehicle. en.wikipedia.org/wiki/Space_Shuttle $\endgroup$ – Solomon Slow May 27 at 21:08
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    $\begingroup$ @HorusKol IMO, it'd be accurate to call Crew Dragon "a shuttle" or "space shuttle", but not "a Shuttle" or "Space Shuttle". I'd probably still avoid it because of this sort of confusion. $\endgroup$ – ceejayoz May 28 at 16:00
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Since the retirement of the US Space Transportation System (aka space shuttle) in 2011, the only crewed transportation to ISS has been in Russian-operated Soyuz spacecraft -- even for American astronauts.

Since then, uncrewed resupply ships to ISS of several types (Dragon, Cygnus, HTV, Progress, ATV) have flown regularly, a few times a year.

SpaceX's Crew Dragon is a newer design. The crewed demo that was scheduled to launch on May 27, 2020 (and will try again on the 30th) was the first time since 2011 that a live crew tried to launch from the US.

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    $\begingroup$ Although technically correct, "failed to launch" might better be worded as a postponement due to weather restrictions to better reflect that it wasn't any issue or problem with the spacecraft itself, but rather external circumstances not related to any failures. $\endgroup$ – Milwrdfan May 28 at 14:00
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    $\begingroup$ Technically correct is the best kind of correct. $\endgroup$ – Organic Marble May 28 at 14:12
  • $\begingroup$ I'm frankly shocked that American astronauts fly on Russian vessels launching on Russian soil, considering the political situation. $\endgroup$ – xjcl May 30 at 15:41
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    $\begingroup$ Technically launching from Kazakh soil, but yeah, it's interesting. It started when things were a little more friendly -- NASA astronauts went to Mir on Soyuz starting in 1995, to ISS on Soyuz starting in 2000, and exclusively on Soyuz after 2011. Regardless of the tension between the US and Russia in other realms, maintaining the ISS requires their cooperation. The Commercial Crew program (of which Crew Dragon is part) will eliminate the reliance on Russian launches, but it's been very slow going. $\endgroup$ – Russell Borogove May 30 at 16:26
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The Space Station has two distinct halves, the Russian Operating Segment (ROS), and the US Operating Segement (USOS).

Here is a picture I love of when the ISS had 6 vehicles attached all at once.

Six visiting vehicles at the ISS in 2011

The ROS has 4 docking ports, that have accepted:

  • Soyuz (Manned crew)
  • Progress (Cargo, unmanned)
  • ATV (European Cargo vehicle unmanned) - retired

The USOS has two docking ports and two berthing ports.

Using the berthing ports (CanadArm2 grabs them, and positions it on the port) we have:

  • HTV - (Japanese cargo vehicle) retired, will be replaced by HTV-X
  • Dragon V1 (Cargo, unmanned, retiring soon in favour of Dragon V2 cargo which will dock not berth)
  • Cyngus (Cargo unmanned)

Using the docking ports where the vehicle handles docking on its own, and can leave on its own we have:

  • Space Shuttle (Retired)
  • Dragon Crew (Demo launched, first man flight May 2020)
  • CST-100 Starliner
  • Dragon Cargo V2 - Will replace Dragon Cargo and dock not berth.
  • Dream Chaser Cargo (in the future)

So quite the selection of vehicles have docked at the ISS and more coming in the future. I ignore Starship since it is practically bigger than the ISS on its own, so who docks to whom in that one?

Going back to the picture at the top the HTV-2, berthing port, now has a PMA/IDA combo for docking. The PMA the Space Shuttle is docked to has an IDA added and can be used for docking.

The port directly below the HTV-2 is where Dragon/Cygnus usually berth, with a second port freed up when the moved the grey module sticking down out of the way to free up the second berthing port.

The schedule for visiting vehicles is complex. There is always a crew vehicle that can return the crew it brought. From the end of the Shuttle, that has been Soyuz (crew of three), soon to be supplemented by Dragon Crew (Crew of 4) or CST-100 Starliner (Crew of 4) on station.

There were 5 ATVs, 8 HTV's, and many many Progress, Soyuz, and Shuttle missions, as well as 22 Dragon, and 14 Cygnus missions over the life of the station.

There are usually 3 vehicles at any time (1 Soyuz, 1 Progress, and often a second Progress or Soyuz) and sometimes more. There is no real fixed interval between visiting vehicles but it is a complex dance of scheduling managed by the team that runs the ISS.

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  • $\begingroup$ Dragon v1 has been retired since the splashdown of CRS-20 in April 2020. It will not fly again. $\endgroup$ – pericynthion May 27 at 23:15
  • $\begingroup$ Does China have any dock-compatible capsules? $\endgroup$ – David Tonhofer May 28 at 9:51
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    $\begingroup$ @DavidTonhofer China is not allowed to the ISS. $\endgroup$ – Alice May 28 at 15:20
  • $\begingroup$ @Alice While politically unviable, engineering wise it seems possible as the design was based on a Russian one. $\endgroup$ – Barry Jenekuns May 29 at 3:15
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    $\begingroup$ @Hug While it is possible, it is an additional requirement, which is always an increase in cost/complexity, for no benefit. If such a requirement arose in the future, they could always use docking adapters instead, like those used on the ISS for APAS-95. $\endgroup$ – Alice May 29 at 22:04
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Semi answer because I think you misread a critical part of that quote:

I was a little surprised - I was under the impression that this happened much more frequently. E.g. ~ quarterly.

What exactly is your "this" here? Is it Spacecraft docking to the ISS (which I got the first read as well)? That happens about quarterly indeed. However, that is not what the quote above it actually says.

Because what you probably read there is:

This (27 May 2020) mission marks the first time since the retirement of the space shuttle in 2011 that humans will fly to the space station [...].

However what is being said there is this:

This (27 May 2020) mission marks the first time since the retirement of the space shuttle in 2011 that humans will fly to the space station from U.S. soil.

That last part is grammatically not necessary for the sentence, and if you read it out loud it kinda falls of, which is why it's easy to skip, BUT its the actually most important part of the sentence.

Since the cancellation of the Space shuttle program it has been the Russian space program that has transported Astronauts to and from the station. Supplying is done by pretty much all participating space organisations.

[Below it is a nitpicky part because of your wording, but IF you are actually thinking about shuttles indeed it might clarify some stuff for you]

and what proportion of those visiting shuttles contain humans?

None. No human has been transported to the ISS via a shuttle in the last (almost) 10 years. I know that this is a bit nitpicky, but there currently are no space shuttles in operation or planned (maybe if you count some of SpaceXs larger designs as shuttles). It's all just more capsules/"regular" rockets. Notably most passenger-carrying from the Soyiuz Program (yes, the designs are ancient, which is why this SpaceX mission is such a big one)

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    $\begingroup$ I want to upvote this because I think this is the correct answer to the question posed, but the snark makes this a lot harder to read/understand. It would be a lot more readable if you just included the relevant snippets with the details highlighted (US soil, shuttles) and a brief, simple explanation that launches in recent years have been from other places and using rockets, not shuttles. $\endgroup$ – user3067860 May 28 at 13:32
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    $\begingroup$ Russian rockets have indeed been used for crew and cargo since the retirement of the Space Shuttle fleet in 2011, but cargo (supplies and experiments) have also been delivered to the ISS by ESA (European) ATV and JAXA (Japanese) HTV cargo vehicles, as well as US commercial launch providers such as ULA and SpaceX. $\endgroup$ – Xano May 28 at 15:29
  • $\begingroup$ @user3067860 hey there, I really was in a bad mood earlier, I rephrased it to a more informational style :) $\endgroup$ – Hobbamok May 28 at 17:41
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    $\begingroup$ @Hobbamok Russia is indeed the only ISS crew ferry (perhaps until Saturday, May 30, if the DM-2 mission is not scrubbed again). As far as I know, only China has crew launch capabilities at this moment, with India trailing not far behind (scheduled for 2021), but neither flies to the ISS. $\endgroup$ – Xano May 29 at 8:28
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    $\begingroup$ I was just browsing Wikipedia and stumbled upon en.wikipedia.org/wiki/Comparison_of_crewed_space_vehicles, which provides a good starting point for some of the answers given in this thread. $\endgroup$ – Xano May 29 at 20:36

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