Author Topic: Should SpaceX Vehicles Have Androgynous Docking Ports?  (Read 10387 times)

Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #100 on: 04/03/2020 04:07 pm »
There seems to be pages and pages here of people saying the current iterations of Dragon can't dock to each other but really there doesn't seem to be any major technical hurdles if they wanted to move to a fully compliant docking system. All it would take is the time and cost of getting their design with both sets of hooks built and certified. The question then is there a use case where it is desired to have that capability.

Difference between possible and practical.  Possible, maybe.  Practical?  Let's list the things you would need to do to be able to dock two Dragons together:
-Passive hooks (and wiring for contingency equipment)
-Passive Strikers (and mounting brackets)
-Would have to ditch the nosecone (androgynous in this case means flipped about the "Z" or zenith axis), it's not rotated.  So two Dragons docking would have their nosecones hit if they were still attached
-Manual docking (no reflectors or current configuration to transfer docking states between vehicles)
-Also for manual docking, you would need to add a cross in the port for orientation, how does that get attached / mounted
-Oh, also, I don't know if we have had docking where both vehicles had pressure seals?  That's an honest question, I don't know if Apollo Soyuz or Russian systems had that.  Currently all VV have a pressure seal, which mates against a flat IDA surface.  I haven't seen any current testing of two pressure seals coming together. 

And that's actually the easy part.  Certification and analysis for contingencies and what if scenarios, and software to properly handle those and testing of all of that.  As I've said before, likely 2x the effort of just the hardware.

When people say rockets aren't legos, it's really not the hardware, the hardware kinda is like legos.  Its the analysis, certification, etc.  When people were looking at using FH to send Orion around the moon, I said it wasn't reasonable to do it in the timeline they had.  It's not the hardware, it's the analysis and documentation.
Both sides have pressure seals. They do FOD checks before docking both with APAS and IDSS. Dragon-2's would flipped be 180 degrees of each other on docking. Nose cone hinge motor limits could be modified to move flat against the vehicle. Electrical and data connectors are identical all the way around and have tons of unused pins.

Offline jarmumd

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #101 on: 04/03/2020 04:21 pm »
Both sides have pressure seals. They do FOD checks before docking both with APAS and IDSS. Dragon-2's would flipped be 180 degrees of each other on docking. Nose cone hinge motor limits could be modified to move flat against the vehicle. Electrical and data connectors are identical all the way around and have tons of unused pins.

Please show me where the red/orange pressure seal is on the IDA.  (Hint, there isn't one, but it's very clear in the Dragon image)

180 degrees about Z/Zenith/axis which points towards earth.  Not 180 deg about X, or the axis which points into the docking system.

WRT nose cone hinge motor limits.  [zubenelgenubi: snark removal]
« Last Edit: 04/03/2020 07:39 pm by zubenelgenubi »

Online Robotbeat

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #102 on: 04/03/2020 04:29 pm »
There seems to be pages and pages here of people saying the current iterations of Dragon can't dock to each other but really there doesn't seem to be any major technical hurdles if they wanted to move to a fully compliant docking system. All it would take is the time and cost of getting their design with both sets of hooks built and certified. The question then is there a use case where it is desired to have that capability.

Difference between possible and practical.  Possible, maybe.  Practical?  Let's list the things you would need to do to be able to dock two Dragons together:
-Passive hooks (and wiring for contingency equipment)
-Passive Strikers (and mounting brackets)
-Would have to ditch the nosecone (androgynous in this case means flipped about the "Z" or zenith axis), it's not rotated.  So two Dragons docking would have their nosecones hit if they were still attached
-Manual docking (no reflectors or current configuration to transfer docking states between vehicles)
-Also for manual docking, you would need to add a cross in the port for orientation, how does that get attached / mounted
-Oh, also, I don't know if we have had docking where both vehicles had pressure seals?  That's an honest question, I don't know if Apollo Soyuz or Russian systems had that.  Currently all VV have a pressure seal, which mates against a flat IDA surface.  I haven't seen any current testing of two pressure seals coming together. 

And that's actually the easy part.  Certification and analysis for contingencies and what if scenarios, and software to properly handle those and testing of all of that.  As I've said before, likely 2x the effort of just the hardware.

When people say rockets aren't legos, it's really not the hardware, the hardware kinda is like legos.  Its the analysis, certification, etc.  When people were looking at using FH to send Orion around the moon, I said it wasn't reasonable to do it in the timeline they had.  It's not the hardware, it's the analysis and documentation.
The whole point of standards is you do a bunch of analysis up-front and make sure the performance meets certain thresholds so you reduce the amount of analysis needed later.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #103 on: 04/03/2020 04:35 pm »
Both sides have pressure seals. They do FOD checks before docking both with APAS and IDSS. Dragon-2's would flipped be 180 degrees of each other on docking. Nose cone hinge motor limits could be modified to move flat against the vehicle. Electrical and data connectors are identical all the way around and have tons of unused pins.
Please show me where the red/orange pressure seal is on the IDA.  (Hint, there isn't one, but it's very clear in the Dragon image)

180 degrees about Z/Zenith/axis which points towards earth.  Not 180 deg about X, or the axis which points into the docking system.

WRT nose cone hinge motor limits.  [zubenelgenubi: snark removal]
Left out APAS at the beginning. Fully compliant IDSS is can have seals on both sides. NDS does not require it. The nose cone has a programmed range of motion. [zubenelgenubi: snark removal]
« Last Edit: 04/03/2020 07:41 pm by zubenelgenubi »

Offline jarmumd

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #104 on: 04/03/2020 04:52 pm »
Both sides have pressure seals. They do FOD checks before docking both with APAS and IDSS. Dragon-2's would flipped be 180 degrees of each other on docking. Nose cone hinge motor limits could be modified to move flat against the vehicle. Electrical and data connectors are identical all the way around and have tons of unused pins.
Please show me where the red/orange pressure seal is on the IDA.  (Hint, there isn't one, but it's very clear in the Dragon image)

180 degrees about Z/Zenith/axis which points towards earth.  Not 180 deg about X, or the axis which points into the docking system.

WRT nose cone hinge motor limits.  [zubenelgenubi: snark removal]
Left out APAS at the beginning. Fully compliant IDSS is can have seals on both sides. NDS does not require it. The nose cone has a programmed range of motion. [zubenelgenubi: snark removal]

Images of APAS-89 and APAS-95.  No seal to be seen in those mechanisms.  I understand there is the IDSS spec, but there is a difference between the spec and reality.

[zubenelgenubi: snark removal]
« Last Edit: 04/03/2020 07:41 pm by zubenelgenubi »

Offline jarmumd

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #105 on: 04/03/2020 04:56 pm »
The whole point of standards is you do a bunch of analysis up-front and make sure the performance meets certain thresholds so you reduce the amount of analysis needed later.

Yes, but standards only apply to interfaces, not to contingency planning.  There is no IDSS standard, in this case, for flight computer design of failure states, or IDSS standard for thruster configuration.  I think your point might have been true had SpaceX used the NDS-B1, since that system was "certified".  I don't really know, but it might have been a trade of cost vs analysis.

Online Robotbeat

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #106 on: 04/03/2020 05:18 pm »
The whole point of standards is you do a bunch of analysis up-front and make sure the performance meets certain thresholds so you reduce the amount of analysis needed later.

Yes, but standards only apply to interfaces, not to contingency planning.  There is no IDSS standard, in this case, for flight computer design of failure states, or IDSS standard for thruster configuration.  I think your point might have been true had SpaceX used the NDS-B1, since that system was "certified".  I don't really know, but it might have been a trade of cost vs analysis.
It's always a trade, and I trust that anyone who has docked to ISS will have had good reasons for the choices they made. I just hope we go toward more standardization in such interfaces. Standardization is one of the few levers we can pull to reduce the huge manpower needed for space missions.
« Last Edit: 04/03/2020 07:38 pm by Robotbeat »
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Negan

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #107 on: 04/03/2020 05:24 pm »
-Would have to ditch the nosecone

I always assumed this was possible for Dragon 2 incase they couldn't get the nosecone open or closed in orbit. Was I mistaken?

Offline Negan

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #108 on: 04/03/2020 05:53 pm »
Oh, also, I don't know if we have had docking where both vehicles had pressure seals?  That's an honest question, I don't know if Apollo Soyuz or Russian systems had that.  Currently all VV have a pressure seal, which mates against a flat IDA surface.  I haven't seen any current testing of two pressure seals coming together.

Wouldn't it likely be good enough? I thought manned spacecraft were already designed to handle a certain amount of pressure loss.

Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #109 on: 04/03/2020 05:55 pm »
I will concede in that my memory seems to be out of date and am misremembering certain things.
-Would have to ditch the nosecone

I always assumed this was possible for Dragon 2 incase they couldn't get the nosecone open or closed in orbit. Was I mistaken?
It was discussed in another thread on the run up to DM1. I don't remember what was said.

Offline MarkW

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #110 on: 04/03/2020 08:13 pm »
It was discussed in another thread on the run up to DM1. I don't remember what was said.





This might be the image, although not from the exact discussion you remember.

I’m going to say, based on the image that the ‘jettison nose cone’ command would be sufficient to remove the nose cone.
« Last Edit: 04/03/2020 08:18 pm by MarkW »

Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #111 on: 04/03/2020 09:59 pm »
It was discussed in another thread on the run up to DM1. I don't remember what was said.





This might be the image, although not from the exact discussion you remember.

I’m going to say, based on the image that the ‘jettison nose cone’ command would be sufficient to remove the nose cone.
Yes that is one of the images.

Offline mikelepage

-Would have to ditch the nosecone (androgynous in this case means flipped about the "Z" or zenith axis), it's not rotated.  So two Dragons docking would have their nosecones hit if they were still attached.

Could you expand on this a bit more? I thought the standard was rotationally symmetrical (and would therefore allow a 180 degree rotation to allow the Dragons to offset their nosecones).

Quote
-Oh, also, I don't know if we have had docking where both vehicles had pressure seals?  That's an honest question, I don't know if Apollo Soyuz or Russian systems had that.  Currently all VV have a pressure seal, which mates against a flat IDA surface.  I haven't seen any current testing of two pressure seals coming together.

That sounds like a deal-breaker to the whole concept unless you can get o-rings to mash up against each other consistently.  Kind of begs the question if it's actually possible to have a truly androgynous docking port at all?  Or would it just be better to say that all docking operations are intrinsically male/female by nature - regardless of which side is the active side.

Online Robotbeat

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #113 on: 04/04/2020 06:10 am »
-Would have to ditch the nosecone (androgynous in this case means flipped about the "Z" or zenith axis), it's not rotated.  So two Dragons docking would have their nosecones hit if they were still attached.

Could you expand on this a bit more? I thought the standard was rotationally symmetrical (and would therefore allow a 180 degree rotation to allow the Dragons to offset their nosecones).

Quote
-Oh, also, I don't know if we have had docking where both vehicles had pressure seals?  That's an honest question, I don't know if Apollo Soyuz or Russian systems had that.  Currently all VV have a pressure seal, which mates against a flat IDA surface.  I haven't seen any current testing of two pressure seals coming together.

That sounds like a deal-breaker to the whole concept unless you can get o-rings to mash up against each other consistently.  Kind of begs the question if it's actually possible to have a truly androgynous docking port at all?  Or would it just be better to say that all docking operations are intrinsically male/female by nature - regardless of which side is the active side.
It's possible.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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