Russians have been doing expedited four-orbit rendezvous with the International Space Station (ISS) for quite a while now, and when it works, its benefits are apparent; You get there before you'd even have to relieve bladder again, which, in a crowded Soyuz spacecraft, should be a lot more important than anyone riding it is ready to publicly admit. But there are other benefits, too. Including for live cargo on Progress, any other time-sensitive or urgently needed equipment and goods, less time to fret any risk management nightmare or otherwise things going wrong on orbit, and it doesn't hurt that mission controllers get to go home sooner either, have everyone rested and avoid human error.

In the meantime, all the past and current US cargo and human crew providers, including NASA's Space Shuttle Orbiter, SpaceX's Dragon, Orbital ATK's Orion,... did/do the standard, about two and a half days, or roughly 40 orbits long rendezvous, just like when Soyuz or Progress spacecraft fail to insert into their ISS chasing orbit precisely enough, or something else needed to accomplish it fails (like failing to deploy KURS antennas or alike). So to my question;

Does NASA require in any version of their COTS (Commercial Orbital Transportation Services) contracts that some, or all providers have to reach capability of expedited rendezvous? Or, if that isn't the case, did any of the current providers, or future contract competitors announce such capability?

I realize that doing expedited rendezvous might require phase corrections of ISS' orbit, but that's what Russians have been doing so far without any problems that I'm aware of. Could US do the same?

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    $\begingroup$ As far as I'm aware of, the answer to this is "no". Dragon 2 will however use the same 6 hour rendezvous procedure Soyuz uses though. $\endgroup$ Jul 26, 2015 at 19:47

1 Answer 1


The reason current cargo providers have not been doing expedited rendezvous is because cargo can take the wait. The rapid rendezvous trajectory requires the ISS to be in a precise point in its orbit and requires exact timing on launch. It also requires precisely timed burns by the craft in orbit which leave little room for delays. All of this restricts the number and frequency of launch windows.

The reason Russia and Soyuz started doing expedited rendezvous is because the Soyuz is particularly cramped for 3 people, and getting the astronauts to the ISS faster keeps them happy and makes the adjustment to zero-g easier.

As EchoLogic has mentioned Dragon 2 will perform the fast rendezvous with crew like the Soyuz.

Update: Hans Koenigsmann, Director of Mission Assurance, said that short rendezvous profiles are possible for current Dragon 1 and future Dragon 2 missions

CRS-4 Mission Brief, Relevant part at 35:20

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    $\begingroup$ T.J. I kinda already describe nearly all of this in my question, and I'm aware of what expedited rendezvous entails, from precision orbital insertion to phase synchronizing ISS' orbit with the launch site's location. I also mention what this is good for, even why it's good also for cargo delivery missions. Your last paragraph would be helpful tho, since it potentially answers the second part of my question, if any current or future providers will be able to do expedited rendezvous with ISS. But I'd require a credible source of that information. Would you have a link confirming it? $\endgroup$
    – TildalWave
    Jul 27, 2015 at 22:47
  • $\begingroup$ @TidablWave I found this pre-flight interview of CRS-4 talking about the potential for short rendezvous space-multimedia.nl.eu.org/… Relevant part at 35:20 I also thought it was mentioned in the Dragon V2 reveal but no news sources recorded it and I haven't had time to rewatch the 30+ minute Q&A $\endgroup$ Jul 28, 2015 at 0:05
  • $\begingroup$ OK I found a YouTube video of this which can be embedded into your answer if you'll want (just copy this link and paste as a new line in your answer), where Irene Klotz (journalist) asks Hans Koenigsmann (SpaceX vice president for Mission Assurance) if they can do shorter than a 2-day rendezvous for crew and cargo and later specifically mentions expedited rendezvous that Russians have been doing. Koenigsmann replies that it's basically a phasing issue, and that they could do it, but doesn't specifically say if they will. Anyway, +1 ;) $\endgroup$
    – TildalWave
    Jul 28, 2015 at 9:18
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    $\begingroup$ regarding "exact timing on launch": the SpaceX CRS flights already use an instantaneous launch window, so any delay means a scrub and retry in 24h. $\endgroup$
    – Hobbes
    Jul 28, 2015 at 18:02
  • $\begingroup$ @hobbes True, however there is a grey area where they could launch ~5 seconds before or after that point since Falcon 9 has extra margin. For pretty much any delay however, they'll scrub. Expedited rendezvous requires not only precise launch timing but because of phase angles, the number of potential launch windows is greatly reduced. $\endgroup$ Jul 28, 2015 at 18:10

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