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Docking/Berthing Q&A
by
Pipcard
on 22 Jul, 2013 21:37
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What's stopping a docking port passageway from being larger than around 0.8 meters? I heard that it was because docking ports were less rigid than berthing ports (so larger diameters would be harder to keep airtight), but I need more reasons why we can't have a passage that's 1 or even 1.3 meters in diameter.
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#1
by
DMeader
on 22 Jul, 2013 23:28
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From "Wings In Orbit: Scientific And Engineering Legacies Of The Space Shuttle 1971-2010" I quote and paraphrase a bit:
"Docking and berthing are conceptually similar methods of connecting a pressurized tunnel between two objects in space. Due to the large thermal differences between sun-facing metal and deep-space-facing metal- the thermal expansion of large metal surfaces can quickly make the precise alignment of structural mating hooks or bolts problematic unless the metal surfaces have have substantial time to reach the same temperature. Hence docking mechanisms were forced to be small due to the need to rapidly align in the presence of large thermal differences."
The gist of it is that due to the need to get on with it and rigidize the connection so that active attitude control can resume, docking has to be completed relatively quickly. With robotically-controlled berthing it is possible to take more time, the parts in question can be larger with plenty of time to equalize temps and allow for precise alignment of mating hooks and latches.
The book I'm quoting from goes into much more detail, and is to be highly recommended.
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#2
by
Jim
on 23 Jul, 2013 04:21
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What's stopping a docking port passageway from being larger than around 0.8 meters? I heard that it was because docking ports were less rigid than berthing ports (so larger diameters would be harder to keep airtight), but I need more reasons why we can't have a passage that's 1 or even 1.3 meters in diameter.
There are limited numbers of configurations that can provide needed L/D and fit within the launch vehicle diameter and have the required docking tunnel diameter
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#3
by
TyMoore
on 28 Jul, 2013 04:06
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So if other considerations were removed (such as practical lifting body return vehicles) a pressurized docking or berthing mechanism could be considerably larger if solar thermal gradients were reduced or removed?
Installing electrical strip heaters, for instance, to bring the pressurized mating surfaces up to uniform temperatures prior to docking/berthing could minimize thermal gradients prior to mating?
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#4
by
Pipcard
on 15 Jul, 2014 17:32
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#5
by
A_M_Swallow
on 16 Jul, 2014 18:11
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Can the NDS act as the space side of an air lock?
It may need a door.
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#6
by
manboy
on 17 Jul, 2014 04:56
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Can the NDS act as the space side of an air lock?
It may need a door.
I think it could but you would need handrails and there may be some concern about causing damage.
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#7
by
baldusi
on 17 Jul, 2014 17:46
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Can the NDS act as the space side of an air lock?
It may need a door.
What's the inner diameter? AIUI, astros prefer a big door with little chance of entangling.
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#8
by
A_M_Swallow
on 18 Jul, 2014 04:56
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Can the NDS act as the space side of an air lock?
It may need a door.
What's the inner diameter? AIUI, astros prefer a big door with little chance of entangling.
NDS - The NASA Docking System has a passage for crew and cargo with a diameter of 800 mm (31.5 in).
https://en.wikipedia.org/wiki/NASA_Docking_SystemCBM - The Common Berthing Mechanism has a passage for crew and cargo transfer with a diameter of 1270 mm of (50 inch).
https://en.wikipedia.org/wiki/Common_berthing_mechanismedit:NDS passage size updated to the Revision C figures provided by Manboy.
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#9
by
Burninate
on 18 Jul, 2014 05:41
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Do CBMs aboard the ISS use some sort of sub-aperture square-with-rounded-corners internal gateway (not pressure-tight) so that people passing through don't snag the utility lines? If so, what are its dimensions?
If not, then what exactly is behind this shape:
http://www.russianspaceweb.com/images/spacecraft/docking/iss_cbm_base_2.jpg ? Is the square bit the only pressurized part?
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#10
by
Jim
on 18 Jul, 2014 12:56
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Do CBMs aboard the ISS use some sort of sub-aperture square-with-rounded-corners internal gateway (not pressure-tight) so that people passing through don't snag the utility lines? If so, what are its dimensions?
There are no utility lines that pass through the CBM hatchway. Utilities are connected on the peripheral of the hatch and pass through the pressure vessel. There is a vestibule that is accessible from the interior where jumpers are installed.
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#11
by
Darren_Hensley
on 18 Jul, 2014 19:43
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Do CBMs aboard the ISS use some sort of sub-aperture square-with-rounded-corners internal gateway (not pressure-tight) so that people passing through don't snag the utility lines? If so, what are its dimensions?
There are no utility lines that pass through the CBM hatchway. Utilities are connected on the peripheral of the hatch and pass through the pressure vessel. There is a vestibule that is accessible from the interior where jumpers are installed.
There is also a velcro attached vestibule cover. This makes the vestibule virtually smooth and conforming to the hatchway opening. It does not obstruct the closing of the hatch if needed or practiced. The hatchway is approx 50" x 50" with 6" radiused corner. Just large enough to permit the passage of an ISPR.
More can be found here:
http://spacecraft.ssl.umd.edu/design_lib/ICES01-2435.ISS_CBM.pdf 
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#12
by
manboy
on 19 Jul, 2014 01:55
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Can the NDS act as the space side of an air lock?
It may need a door.
What's the inner diameter? AIUI, astros prefer a big door with little chance of entangling.
NDS - The NASA Docking System has a passage for crew and cargo with a diameter of 685 millimetres (27.0 in), which can be increased to 813 millimetres (32.0 in) by removing the petals of the capture mechanism after mating. IMHO An outer door will probably have the petals present.
https://en.wikipedia.org/wiki/NASA_Docking_System
That's outdated info. The passthrough diameter is now 800 mm (31.5 in), the petals are no longer removable.
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#13
by
A_M_Swallow
on 19 Jul, 2014 22:03
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That's outdated info. The passthrough diameter is now 800 mm (31.5 in), the petals are no longer removable.
Wikipedia article updated. Other changes may be needed.
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#14
by
Lar
on 20 Jul, 2014 13:52
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Seems to me there is little likelyhood that astros would want to go through a 31 inch diameter opening suited up... way too much snagability... I could be wrong but...
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#15
by
A_M_Swallow
on 20 Jul, 2014 16:30
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Seems to me there is little likelyhood that astros would want to go through a 31 inch diameter opening suited up... way too much snagability... I could be wrong but...
Then the astronauts will have to play a game of hunt the bigger hatch on Orion, Dragonrider, CST-100, DreamChaser and BA-330.
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#16
by
manboy
on 21 Jul, 2014 08:57
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Seems to me there is little likelyhood that astros would want to go through a 31 inch diameter opening suited up... way too much snagability... I could be wrong but...
Then the astronauts will have to play a game of hunt the bigger hatch on Orion, Dragonrider, CST-100, DreamChaser and BA-330.
Orion has a side hatch.
Dragonrider, CST-100 and Dream Chaser don't have or need a EVA capability in their current role.
And last I heard Bigelow stations would use a BEAM-derived airlock. EVA-capability shouldn't be an assumed feature, it carries a high cost and Bigelow may decide it's just not worth it.
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#17
by
Burninate
on 21 Mar, 2015 02:06
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Can the NDS act as the space side of an air lock?
It may need a door.
What's the inner diameter? AIUI, astros prefer a big door with little chance of entangling.
NDS - The NASA Docking System has a passage for crew and cargo with a diameter of 685 millimetres (27.0 in), which can be increased to 813 millimetres (32.0 in) by removing the petals of the capture mechanism after mating. IMHO An outer door will probably have the petals present.
https://en.wikipedia.org/wiki/NASA_Docking_System
That's outdated info. The passthrough diameter is now 800 mm (31.5 in), the petals are no longer removable.
Is it the case that 3 petals in a mated pair are no longer removeable, or 6 petals in a mated pair are no longer removeable?
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#18
by
Danderman
on 21 Mar, 2015 11:11
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What's stopping a docking port passageway from being larger than around 0.8 meters? I heard that it was because docking ports were less rigid than berthing ports (so larger diameters would be harder to keep airtight), but I need more reasons why we can't have a passage that's 1 or even 1.3 meters in diameter.
The Russian hybrid docking system has a passage that is 1100 mm in diameter.
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#19
by
Lars-J
on 22 Mar, 2015 07:30
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What's stopping a docking port passageway from being larger than around 0.8 meters? I heard that it was because docking ports were less rigid than berthing ports (so larger diameters would be harder to keep airtight), but I need more reasons why we can't have a passage that's 1 or even 1.3 meters in diameter.
The Russian hybrid docking system has a passage that is 1100 mm in diameter.
... before ventilation air ducts and various pass-through cables are added.
