Author Topic: Should SpaceX Vehicles Have Androgynous Docking Ports?  (Read 10358 times)

Offline pochimax

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1) Anyone care to speculate/confirm whether a Dragon 2 can dock to a Dragon XL?
maybe, you can have a problem with the nose cap of Crew Dragon. Independently of ports compatiblity.

Edit. Maybe DragonXL has been exactly calculated to avoid this problem?



« Last Edit: 04/02/2020 03:13 am by gongora »

Offline Zed_Noir

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Re: Re: SpaceX Dragon XL
« Reply #1 on: 03/31/2020 10:34 am »
If DragonXL does a slow transfer to NRHO (months), how did SpaceX comply with the unique capability of a fast transfer to Gateway (<30 days)? If NASA request this unique capability.

The standard DragonXL launch and travel is not a fully expendable Falcon Heavy? And the fast transit is a fully expendable?

I' m a little bit lost.

Can you point to the specific requirement for a <30 days transfer to Gateway? I can't seem to find it.

File: Attachment_01_GLS_SOW.pdf
5.0 MISSION UNIQUE CAPABILITIES (SUBCLIN 103) [pages 29-30]

Fast Transit to Gateway: Provide end-to-end cargo delivery services withcargo transit time of 30 days or less. NASA shall have the ability to order this capability within the time defined in the GLS Space System Architecture contract attachment.


Perfect! Thank you. It is sometimes challenging to find specifics when an RFP has a kazillion attachments ;)

It is a mission unique capability. Here is the first paragraph, which basically explains it all:

Quote from: Attachment_01_GLS_SOW
5.0 MISSION UNIQUE CAPABILITIES (SUBCLIN 103)

The contractor shall provide Mission Unique Capabilities for requirements over and above
logistic service requirements obtained under subCLINs 101 and 102.

These capabilities may be added throughout the life of the contract or they may be incorporated in
response to specific task order requirements.


So, these are non-standard capabilities which MAY be - someday - required by NASA. As such, they are not part of the baseline solution offered by SpaceX.
What I think (but I'll have to check with my sources) is that SpaceX is perfectly capable of sending Dragon XL on an expedited trajectory to Gateway, but at the cost of reduced cargo up-mass.

Another solution would probably be to to fly FH in fully expendable mode. Which will result in the launch being more expensive to NASA and thus the total number of launches under the fixed price cost cap decreasing.

If NASA get over their aversion to Earth orbit rendezvous. SpaceX could just assembled and pre-positioned a large vehicle stack in LEO with enough hypergolic propellants for a fast transfer from LEO to the Gateway. The Dragon XL flies up on a Falcon 9 and docked with vehicle stack then head for the Moon.

Maybe the vehicle stack could be a modified Dragon XL variant only carrying hypergolic propellants with a vacuum optimized de-rated SuperDraco in place of the docking port on the bottom and a docking collar on the top.

Offline Zed_Noir

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Re: Re: SpaceX Dragon XL
« Reply #2 on: 03/31/2020 10:59 am »
<snip>
I do wonder how many other customers there would be for this kind of thing.  Surely the creation of a class of small, temporary and private space station(s) in LEO would help SpaceX fund SS/SH development?

1) Anyone care to speculate/confirm whether a Dragon 2 can dock to a Dragon XL?
2) Could it be done autonomously? (e.g. so crew of two could just be payload specialists, or spaceflight participants).
3) Just because Dragon XL is not designed to re-enter the atmosphere need not make it "expendable" if it could be reused by multiple visiting vehicles.
4) If Dragon XL is being designed to host a Canadarm, could it retrieve payloads from the trunk of a visiting Dragon 2?
5) Would it be possible to use the visiting Dragon 2 as an airlock (i.e. shut the hatch between D2 and Dragon XL and open and close the main side hatch)?
....

@jarmumd posted up thread regarding your 1) query
If it is supposed to transfer both pressurized and unpressurized cargo, how could it have docking at both ends?

Also, SpaceX would need to build their own IDSS passive docking port.  Contrary to popular belief, the current system does not have the equipment to act as a passive for other vehicles to dock (ie not androgynous)....
Citation needed. The standard specifies it must be androgynous (at least for active side). If it's not androgynous, it's not IDSS.

For Crew Dragon, androgyny is a safety consideration as well to allow rescue. Doubtful that they'd change the spec for Dragon XL as that'd require more certification.

If you're right, then you should be able to provide a reference. If you're just supposing, then you should say so.

I'm the citation, I work on docking systems.

Also, if you look at any high resolution picture of the SpaceX docking system, there are no passive strikers or hooks, so there is nothing to soft or hard capture to.

Offline rakaydos

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Re: Re: SpaceX Dragon XL
« Reply #3 on: 03/31/2020 11:39 am »
<snip>
I do wonder how many other customers there would be for this kind of thing.  Surely the creation of a class of small, temporary and private space station(s) in LEO would help SpaceX fund SS/SH development?

1) Anyone care to speculate/confirm whether a Dragon 2 can dock to a Dragon XL?
2) Could it be done autonomously? (e.g. so crew of two could just be payload specialists, or spaceflight participants).
3) Just because Dragon XL is not designed to re-enter the atmosphere need not make it "expendable" if it could be reused by multiple visiting vehicles.
4) If Dragon XL is being designed to host a Canadarm, could it retrieve payloads from the trunk of a visiting Dragon 2?
5) Would it be possible to use the visiting Dragon 2 as an airlock (i.e. shut the hatch between D2 and Dragon XL and open and close the main side hatch)?
....

@jarmumd posted up thread regarding your 1) query
If it is supposed to transfer both pressurized and unpressurized cargo, how could it have docking at both ends?

Also, SpaceX would need to build their own IDSS passive docking port.  Contrary to popular belief, the current system does not have the equipment to act as a passive for other vehicles to dock (ie not androgynous)....
Citation needed. The standard specifies it must be androgynous (at least for active side). If it's not androgynous, it's not IDSS.

For Crew Dragon, androgyny is a safety consideration as well to allow rescue. Doubtful that they'd change the spec for Dragon XL as that'd require more certification.

If you're right, then you should be able to provide a reference. If you're just supposing, then you should say so.

I'm the citation, I work on docking systems.

Also, if you look at any high resolution picture of the SpaceX docking system, there are no passive strikers or hooks, so there is nothing to soft or hard capture to.
How hard would it be to retrofit passive elements to an existing design? Is the lack of strikers or hooks a critical design flaw, or is it something that can be rectified if SpaceX actually cared?

Offline pochimax

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Re: Re: SpaceX Dragon XL
« Reply #4 on: 03/31/2020 01:18 pm »
Quote
Also, if you look at any high resolution picture of the SpaceX docking system, there are no passive strikers or hooks, so there is nothing to soft or hard capture to.

Is it true? I thought an APAS can act as active or passive as needed.



« Last Edit: 03/31/2020 01:48 pm by Carl G »

Offline woods170

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Re: Re: SpaceX Dragon XL
« Reply #5 on: 03/31/2020 01:29 pm »
Quote
Also, if you look at any high resolution picture of the SpaceX docking system, there are no passive strikers or hooks, so there is nothing to soft or hard capture to.

Is it true? I thought an APAS can act as active or passive as needed.

<removed image. PLEASE, do NOT embed images. Attach only>


That's the thing: it's not an APAS. It is based on NDS, which is NASA's implementation of the IDSS.

IF the docking system was built to the letter, as specified in IDSS
THAN the docking system is androgynous (Meaning that it can dock to a duplicate of itself)
ELSE it cannot dock to a duplicate of itself.

However:
SpaceX did NOT build their version of the IDSS to the letter. They only included the ACTIVE side latches into the system. The passive latches are missing.
In other words: two SpaceX docking systems can NOT dock to each other, because they are not fully androgynous. The active hooks on one side would find NO passive hooks on the other side to latch onto.


« Last Edit: 03/31/2020 02:03 pm by woods170 »

Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #6 on: 03/31/2020 04:10 pm »
How hard would it be to retrofit passive elements to an existing design? Is the lack of strikers or hooks a critical design flaw, or is it something that can be rectified if SpaceX actually cared?

I think you are missing the point.  Everything is built to the minimum that meets requirements.  Every extra thing, passive docking components, airlocks, it's not just the hardware, it's the money to build it, test it, the documentation to certify it.  I know many people on this forum think it's easy, and sure it's not that hard to get the machinists to build it.  But certifying it is probably more the double the cost and more critically, the time.

Every time you add something, you need to think about "what if".  What if something fails, then something else fails, or combinations of other failures.  Every "what if" is analysis and documentation and meetings.  Now multiply that by every component - the work load becomes exponential.  Minimum Viable Product is the name of the game.

Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #7 on: 03/31/2020 05:30 pm »
How hard would it be to retrofit passive elements to an existing design? Is the lack of strikers or hooks a critical design flaw, or is it something that can be rectified if SpaceX actually cared?

I think you are missing the point.  Everything is built to the minimum that meets requirements.  Every extra thing, passive docking components, airlocks, it's not just the hardware, it's the money to build it, test it, the documentation to certify it.  I know many people on this forum think it's easy, and sure it's not that hard to get the machinists to build it.  But certifying it is probably more the double the cost and more critically, the time.

Every time you add something, you need to think about "what if".  What if something fails, then something else fails, or combinations of other failures.  Every "what if" is analysis and documentation and meetings.  Now multiply that by every component - the work load becomes exponential.  Minimum Viable Product is the name of the game.
It's interesting, because lack of passive capability reduces safety of the IDSS design. One of the main features of an androgynous design (over probe and drogue, for instance) is ability to rescue and overall operational flexibility and contingency.
« Last Edit: 03/31/2020 05:30 pm by Robotbeat »
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Offline Coastal Ron

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Re: Re: SpaceX Dragon XL
« Reply #8 on: 03/31/2020 05:53 pm »
When RFP's are put out for systems that are needed and you've got one, two, or three options you are pretty much stuck with those options.

That is the same no matter if the custom product is for the government or a commercial company. So it has no bearing to this discussion.

Quote
For big contracts engineers are utilized and a better sense of value can be determined. However, when there is limited competion you have to pick from the options available.

I realize you are new to NSF, and it is good you are engaging in discussions. But many of us have seen how the NASA competitive procurement process works on programs like the Commercial Cargo and Commercial Crew programs, so we have seen how NASA evaluated and justified their choices.

For instance, Look at the Selection Statement for the Commercial Crew Integrated Capability (CCiCap) contract award and you'll see how NASA evaluated the bids.

Quote
Even if an option is "overpriced" for what is being done...

When you are talking about something highly technical that has never been done, the term "overpriced" can't be justified or quantified. Instead the government, through the President and Congress, determine what they are willing to pay, and then they solicit quotes to see what the contractors are willing to charge.

If the bids come back within the range the government was expecting, then they can proceed with determining the winning bidder. If the pricing comes in higher than what the government wanted, then they will work with the bidding companies to determine what is driving the prices higher than desired. If they can't work it out the government may cancel the program, or they may restructure it. That didn't happen with this program.

Quote
Also just as a side note, regardless of the capability of the individuals that work for the government they are hindered by the system that moves slow and inefficiently.

That is the same for the private sector too, so again that has no bearing on this discussion.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #9 on: 03/31/2020 05:53 pm »
It's interesting, because lack of passive capability reduces safety of the IDSS design. One of the main features of an androgynous design (over probe and drogue, for instance) is ability to rescue and overall operational flexibility and contingency.

In general, you aren't wrong, but where we are today it doesn't matter.  For instance, to your points on rescue, operational flexibility, contingency....     how?  Rescue what?

What would the scenario have to be to have Orion or CST-100 dock to a Dragon (if it was equipped)?  In any contingency you might be thinking of, the existing spacecraft must have enough redundancies and equipment to make it back to earth safely.  Why design for something that is so far out of the fault space?  There is no reasonable circumstance in which you could launch a rescue spacecraft in time to do anything.  The exception to this is if one is already docked to the ISS.

And if you are already at the ISS, what's the point? 

If a spacecraft is so damaged it cannot return to earth, are you sure it could even be docked to?

In case my tone comes across wrong, understand that I do agree with you in principal, but once you go down the rabbit hole, you'll see there just isn't a credible reason now to have this capability, and I haven't seen a reasonable need to have it in the future, specifically for commercial crew or cargo resupply.
« Last Edit: 03/31/2020 05:57 pm by jarmumd »

Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #10 on: 03/31/2020 05:58 pm »
It's interesting, because lack of passive capability reduces safety of the IDSS design. One of the main features of an androgynous design (over probe and drogue, for instance) is ability to rescue and overall operational flexibility and contingency.

In general, you aren't wrong, but where we are today it doesn't matter.  For instance, to your points on rescue, operational flexibility, contingency....     how?  Rescue what?

What would the scenario have to be to have Orion or CST-100 dock to a Dragon (if it was equipped)?  In any contingency you might be thinking of, the existing spacecraft must have enough redundancies and equipment to make it back to earth safely.  Why design for something that is so far out of the fault space?  There is no reasonable circumstance in which you could launch a rescue spacecraft in time to do anything.  The exception to this is if one is already docked to the ISS.

And if you are already at the ISS, what's the point?  And if things were so bad that you needed to go from one spacecraft to the other, wouldn't it make more sense to just open the hatches, throw a line and go across?  Or, why would you be docking two healthy spacecraft in this scenario?  If one is so damaged it cannot return to earth, are you sure it could even be docked to?

In case my tone comes across wrong, understand that I do agree with you in principal, but once you go down the rabbit hole, you'll see there just isn't a credible reason now to have this capability, and I haven't seen a reasonable need to have it in the future, specifically for commercial crew or cargo resupply.

The Russians have docked to spacecraft that were inactive. It's tough, but it can be done. The main argument is to give flexibility where otherwise there'd be none. For instance, imagine a LEO servicing mission gone awry: Heatshield or parachute system damaged.
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Re: Re: SpaceX Dragon XL
« Reply #11 on: 03/31/2020 06:39 pm »
It's like the Shuttle Columbia rescue scenario - fast-track another Shuttle to launch to rescue the crew - but imagine if there had been something like Dragon or Starliner that could have docked to the Shuttle.

And while Starliner and Dragon are currently going to ISS, the ISS will be splashed someday. Or maybe one is flying some independent tourists, or to a private space station.

Missions that find themselves in danger are almost always failures of imagination. Not allowing for the possibility of being able to be docked to in an emergency situation IMO is a failure of imagination as well.
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Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #12 on: 03/31/2020 06:42 pm »
Another one was Dragon autonomously docking to Orion with orion serving as a passive side because its AR&D wasn’t finished, yet. This was one possibility considered for getting a 2020 trip around the Moon with people in orion.
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Re: Re: SpaceX Dragon XL
« Reply #13 on: 03/31/2020 06:46 pm »
It's interesting, because lack of passive capability reduces safety of the IDSS design. One of the main features of an androgynous design (over probe and drogue, for instance) is ability to rescue and overall operational flexibility and contingency.

In general, you aren't wrong, but where we are today it doesn't matter.  For instance, to your points on rescue, operational flexibility, contingency....     how?  Rescue what?

What would the scenario have to be to have Orion or CST-100 dock to a Dragon (if it was equipped)?  In any contingency you might be thinking of, the existing spacecraft must have enough redundancies and equipment to make it back to earth safely.  Why design for something that is so far out of the fault space?  There is no reasonable circumstance in which you could launch a rescue spacecraft in time to do anything.  The exception to this is if one is already docked to the ISS.

And if you are already at the ISS, what's the point? 

If a spacecraft is so damaged it cannot return to earth, are you sure it could even be docked to?

In case my tone comes across wrong, understand that I do agree with you in principal, but once you go down the rabbit hole, you'll see there just isn't a credible reason now to have this capability, and I haven't seen a reasonable need to have it in the future, specifically for commercial crew or cargo resupply.

It's a good point.  The only way I see it working is how they did it with shuttle at the end, with every manned U.S space launch, a secondary option must be ready to launch within a given time frame (48/72 hours?).  With Orion, Starliner and Crew Dragon, we have the options.
« Last Edit: 03/31/2020 06:47 pm by Khadgars »
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Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #14 on: 03/31/2020 07:17 pm »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”
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Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #15 on: 03/31/2020 07:25 pm »
Another one was Dragon autonomously docking to Orion with orion serving as a passive side because its AR&D wasn’t finished, yet. This was one possibility considered for getting a 2020 trip around the Moon with people in orion.

There currently isn't such a thing as autonomous docking between spacecraft.  Only autonomous docking to ISS, and hopefully gateway.  There are no passive reflectors which exist on any spacecraft other than the IDA/ISS.  And some spacecraft use telemetry from the ISS to dock, using reflectors for backup.  As such two spacecraft docking would be a manual process.  An automated process might be years of development.  Again, not the hardware, it's the certification.

Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #16 on: 03/31/2020 07:36 pm »
It's like the Shuttle Columbia rescue scenario - fast-track another Shuttle to launch to rescue the crew - but imagine if there had been something like Dragon or Starliner that could have docked to the Shuttle.

And while Starliner and Dragon are currently going to ISS, the ISS will be splashed someday. Or maybe one is flying some independent tourists, or to a private space station.

Missions that find themselves in danger are almost always failures of imagination. Not allowing for the possibility of being able to be docked to in an emergency situation IMO is a failure of imagination as well.

I don't think there is any credible scenario where a spacecraft is "fast-tracked" to launch a rescue.  For the foreseeable future, all spacecraft are visiting a space station.  Maybe there is a scenario where you can't dock to the station, but another capsule can dock to you?  Maybe.  But what if Shuttle were putting up a satellite or going to Hubble?  There just isn't the fuel for a capsule to go and rescue them, starting at the ISS.  So apply that to anything coming in the future.  I just don't think there is such a thing as a capsule going to rescue another capsule.  Maybe some form of proximity operations at a station, but then you probably also have other options.

I'll caveat that to say that I do think that we would need an androgynous docking system if we had multiple commercial lunar landers.  But even then, weight is so critical to lunar operations, I think you would explore every other option in fault space before taking a large amount of useless mass with you.  If you only have a single lander, then it's the same as the ISS.  And if you were to have an "Active" on an Orion, and a "Passive" on a lander, well then you have contingencies at gateway because you could do Orion->Lander or Orion->Gateway->Lander, so there still isn't a need for androgyny.

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Re: Re: SpaceX Dragon XL
« Reply #17 on: 03/31/2020 08:02 pm »
It's like the Shuttle Columbia rescue scenario - fast-track another Shuttle to launch to rescue the crew - but imagine if there had been something like Dragon or Starliner that could have docked to the Shuttle.

And while Starliner and Dragon are currently going to ISS, the ISS will be splashed someday. Or maybe one is flying some independent tourists, or to a private space station.

Missions that find themselves in danger are almost always failures of imagination. Not allowing for the possibility of being able to be docked to in an emergency situation IMO is a failure of imagination as well.

I don't think there is any credible scenario where a spacecraft is "fast-tracked" to launch a rescue.  For the foreseeable future, all spacecraft are visiting a space station.  Maybe there is a scenario where you can't dock to the station, but another capsule can dock to you?  Maybe.  But what if Shuttle were putting up a satellite or going to Hubble?  There just isn't the fuel for a capsule to go and rescue them, starting at the ISS.  So apply that to anything coming in the future.  I just don't think there is such a thing as a capsule going to rescue another capsule.  Maybe some form of proximity operations at a station, but then you probably also have other options.

I'll caveat that to say that I do think that we would need an androgynous docking system if we had multiple commercial lunar landers.  But even then, weight is so critical to lunar operations, I think you would explore every other option in fault space before taking a large amount of useless mass with you.  If you only have a single lander, then it's the same as the ISS.  And if you were to have an "Active" on an Orion, and a "Passive" on a lander, well then you have contingencies at gateway because you could do Orion->Lander or Orion->Gateway->Lander, so there still isn't a need for androgyny.

Both Starliner and Dragon are largely reusable, so after a couple years of ISS crew rotations they both will have several spacecraft in various states of readiness, probably with long periods where launch-ready (or nearly so) spacecraft are simply waiting on the next mission. Both providers are launching on a more or less steady cadence and so would have LVs available. SpaceX, in particular, would be capable of pulling a launch vehicle out of rotation, or out of its stockpile, on short notice.

Quote
There just isn't the fuel for a capsule to go and rescue them, starting at the ISS.

Start from the ground.

Quote
I just don't think there is such a thing as a capsule going to rescue another capsule.

And there can't be, if they aren't capable of being docked to.

But the IDSS standard was specifically designed with that in mind. It is androgynous, or it's supposed to be.
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Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #18 on: 03/31/2020 08:22 pm »
It's like the Shuttle Columbia rescue scenario - fast-track another Shuttle to launch to rescue the crew - but imagine if there had been something like Dragon or Starliner that could have docked to the Shuttle.

And while Starliner and Dragon are currently going to ISS, the ISS will be splashed someday. Or maybe one is flying some independent tourists, or to a private space station.

Missions that find themselves in danger are almost always failures of imagination. Not allowing for the possibility of being able to be docked to in an emergency situation IMO is a failure of imagination as well.

I don't think there is any credible scenario where a spacecraft is "fast-tracked" to launch a rescue.  For the foreseeable future, all spacecraft are visiting a space station.  Maybe there is a scenario where you can't dock to the station, but another capsule can dock to you?  Maybe.  But what if Shuttle were putting up a satellite or going to Hubble?  There just isn't the fuel for a capsule to go and rescue them, starting at the ISS.  So apply that to anything coming in the future.  I just don't think there is such a thing as a capsule going to rescue another capsule.  Maybe some form of proximity operations at a station, but then you probably also have other options.

I'll caveat that to say that I do think that we would need an androgynous docking system if we had multiple commercial lunar landers.  But even then, weight is so critical to lunar operations, I think you would explore every other option in fault space before taking a large amount of useless mass with you.  If you only have a single lander, then it's the same as the ISS.  And if you were to have an "Active" on an Orion, and a "Passive" on a lander, well then you have contingencies at gateway because you could do Orion->Lander or Orion->Gateway->Lander, so there still isn't a need for androgyny.
This latter sentence seems false. For instance:

Original plan is Gateway goes up first. Both lander and Orion need active systems to dock to the passive gateway. But! Current plan is to skip Gateway and dock directly to each other for the first mission, and then *later* go back to the original plan (so that the lander ascent stage can be docked to Gateway between missions for reuse). So, given NASA's current plans, the lander at least MUST be androgynous if we're to keep its configuration the same.
« Last Edit: 03/31/2020 08:24 pm by Robotbeat »
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Re: Re: SpaceX Dragon XL
« Reply #19 on: 03/31/2020 08:28 pm »
It's interesting, because lack of passive capability reduces safety of the IDSS design. One of the main features of an androgynous design (over probe and drogue, for instance) is ability to rescue and overall operational flexibility and contingency.

In general, you aren't wrong, but where we are today it doesn't matter.  For instance, to your points on rescue, operational flexibility, contingency....     how?  Rescue what?

What would the scenario have to be to have Orion or CST-100 dock to a Dragon (if it was equipped)?  In any contingency you might be thinking of, the existing spacecraft must have enough redundancies and equipment to make it back to earth safely.  Why design for something that is so far out of the fault space?  There is no reasonable circumstance in which you could launch a rescue spacecraft in time to do anything.  The exception to this is if one is already docked to the ISS.

And if you are already at the ISS, what's the point? 

If a spacecraft is so damaged it cannot return to earth, are you sure it could even be docked to?

In case my tone comes across wrong, understand that I do agree with you in principal, but once you go down the rabbit hole, you'll see there just isn't a credible reason now to have this capability, and I haven't seen a reasonable need to have it in the future, specifically for commercial crew or cargo resupply.

It's a good point.  The only way I see it working is how they did it with shuttle at the end, with every manned U.S space launch, a secondary option must be ready to launch within a given time frame (48/72 hours?).  With Orion, Starliner and Crew Dragon, we have the options.

I think it wouldn't hurt to consider that as a possibility. NASA did indeed make it the regular practice on the last dozen Shuttle flights. It wouldn't be too great of a burden on SpaceX, would be a much greater burden for Starliner.
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Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #20 on: 03/31/2020 08:37 pm »
It’s impossible to use dragon XL as a mission-extending mini-station as supposed here if it doesn’t have an androgynous (or passive) docking capability.
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Re: Re: SpaceX Dragon XL
« Reply #21 on: 03/31/2020 08:44 pm »
And if we were serious about building a foundation for spacefaring and operational flexibility, we’d include standard fuel transfer capability, too. That’s much harder than just including passive capability, though.
« Last Edit: 03/31/2020 08:57 pm by Robotbeat »
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Offline indaco1

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Re: Re: SpaceX Dragon XL
« Reply #22 on: 03/31/2020 08:46 pm »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”


Quote
I just don't think there is such a thing as a capsule going to rescue another capsule.

And there can't be, if they aren't capable of being docked to.


Pretty OT, but is an EVA crew transfer (spacewalk to another veichle) possible for a rescue mission?
« Last Edit: 03/31/2020 08:47 pm by indaco1 »
Non-native English speaker and non-expert, be patient.

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Re: Re: SpaceX Dragon XL
« Reply #23 on: 03/31/2020 08:48 pm »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”


Quote
I just don't think there is such a thing as a capsule going to rescue another capsule.

And there can't be, if they aren't capable of being docked to.


Pretty OT, but is an EVA crew tranfer (spacewalk to another veichle) possible for a rescue mission?
Good idea. Why even put docking ports on the lander, then? Just EVA over to it from Orion! Only need rendezvous, then. ;)
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Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #24 on: 03/31/2020 09:01 pm »
This latter sentence seems false. For instance:

Original plan is Gateway goes up first. Both lander and Orion need active systems to dock to the passive gateway. But! Current plan is to skip Gateway and dock directly to each other for the first mission, and then *later* go back to the original plan (so that the lander ascent stage can be docked to Gateway between missions for reuse). So, given NASA's current plans, the lander at least MUST be androgynous if we're to keep its configuration the same.

I read "HLS_Appendix_H_BAA_2019-10-02c.pdf" page 9, CLIN 009 - Option A: Docking System.  Work on a detachable docking adapter...  As to mean an adapter to make a port on the gateway active instead of passive.  How do you read that?

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Re: Re: SpaceX Dragon XL
« Reply #25 on: 03/31/2020 09:29 pm »
This latter sentence seems false. For instance:

Original plan is Gateway goes up first. Both lander and Orion need active systems to dock to the passive gateway. But! Current plan is to skip Gateway and dock directly to each other for the first mission, and then *later* go back to the original plan (so that the lander ascent stage can be docked to Gateway between missions for reuse). So, given NASA's current plans, the lander at least MUST be androgynous if we're to keep its configuration the same.

I read "HLS_Appendix_H_BAA_2019-10-02c.pdf" page 9, CLIN 009 - Option A: Docking System.  Work on a detachable docking adapter...  As to mean an adapter to make a port on the gateway active instead of passive.  How do you read that?
Ah, you got me.

Looks like NASA is *allowing* HLS offerers to have passive-only on their lander PROVIDED they also build an active-active adapter for the gateway. But I see this as merely allowing the maximum possible options to be considered, whether or not they’re a good idea.

Insane to me that we’re actually talking about building a separate chunk of flight hardware as a kludge to avoid building the adapter fully to the androgynous spec of IDSS.

That means that you have less redundancy as you cannot swap Orion and the lander’s docking ports.

I pray that whatever bean counter you work with that is insisting on doing this kludge instead of building androgynous capability right the first time changes their mind.

Same for SpaceX.

Really, NASA ought to be insisting on androgynous capability at least for everything that needs to be active plus the lander. I means seriously, adding an extra docking adapter just to avoid making the lander or Orion androgynous! Insane.

That’s just my personal opinion, though.
« Last Edit: 03/31/2020 09:31 pm by Robotbeat »
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Offline DigitalMan

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Re: Re: SpaceX Dragon XL
« Reply #26 on: 03/31/2020 09:30 pm »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”

It isn't sane for the contractor to add requirements to NASA contracts.  It will already be an intense and costly development effort. Anything you add will likely spiral into a testing effort you would regret.

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Re: Re: SpaceX Dragon XL
« Reply #27 on: 03/31/2020 09:37 pm »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”

It isn't sane for the contractor to add requirements to NASA contracts.  It will already be an intense and costly development effort. Anything you add will likely spiral into a testing effort you would regret.
Right. NASA as the customer ought to insist on it.
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Re: Re: SpaceX Dragon XL
« Reply #28 on: 03/31/2020 09:41 pm »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”

It isn't sane for the contractor to add requirements to NASA contracts.  It will already be an intense and costly development effort. Anything you add will likely spiral into a testing effort you would regret.
Right. NASA as the customer ought to insist on it.

I know the USA is -particularly- bad about this, but why even have international standards if we're not going to build to them....
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Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #29 on: 03/31/2020 10:05 pm »
Really, NASA ought to be insisting on androgynous capability at least for everything that needs to be active plus the lander. I means seriously, adding an extra docking adapter just to avoid making the lander or Orion androgynous! Insane.

That’s just my personal opinion, though.

Well, just keep in mind that sending an adapter isn't much different from sending the Dragon XL, and you only do it once.

Adding 100 lbm or more for a passive capability that may never be used, for every landing and ascent from the moon represents orders of magnitude more mass at liftoff.  Or that much less capability to land on the moon.

It's not quite this simple, but the docking drogue or cone on the Apollo Lunar Lander weighed 18-20 lbs.  That's it.  A modern docking system can weight several hundred pounds.  Not quite apples to apples, but it gives a sense of scale.

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Re: Re: SpaceX Dragon XL
« Reply #30 on: 03/31/2020 10:28 pm »
Really, NASA ought to be insisting on androgynous capability at least for everything that needs to be active plus the lander. I means seriously, adding an extra docking adapter just to avoid making the lander or Orion androgynous! Insane.

That’s just my personal opinion, though.

Well, just keep in mind that sending an adapter isn't much different from sending the Dragon XL, and you only do it once.

Adding 100 lbm or more for a passive capability that may never be used, for every landing and ascent from the moon represents orders of magnitude more mass at liftoff.  Or that much less capability to land on the moon.

It's not quite this simple, but the docking drogue or cone on the Apollo Lunar Lander weighed 18-20 lbs.  That's it.  A modern docking system can weight several hundred pounds.  Not quite apples to apples, but it gives a sense of scale.
100lb or more for a passive capability? I find that hard to believe, but I’ll take your word for it.

If we’re not using the advantages of a modern docking system, we should go back to a drogue and cone system and save even more weight.
« Last Edit: 03/31/2020 10:29 pm by Robotbeat »
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Offline matthewkantar

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Re: Re: SpaceX Dragon XL
« Reply #31 on: 03/31/2020 10:48 pm »
This is the sort of thing that arises from extreme mass constrictions to orbit and a stubborn refusal to develop on-orbit fuel transfer. If those two things are sorted out, no one would be so silly as to have anything other than androgynous docking gear.

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Re: Re: SpaceX Dragon XL
« Reply #32 on: 03/31/2020 11:12 pm »
Really, NASA ought to be insisting on androgynous capability at least for everything that needs to be active plus the lander. I means seriously, adding an extra docking adapter just to avoid making the lander or Orion androgynous! Insane.

That’s just my personal opinion, though.

Well, just keep in mind that sending an adapter isn't much different from sending the Dragon XL, and you only do it once.

Adding 100 lbm or more for a passive capability that may never be used, for every landing and ascent from the moon represents orders of magnitude more mass at liftoff.  Or that much less capability to land on the moon.

It's not quite this simple, but the docking drogue or cone on the Apollo Lunar Lander weighed 18-20 lbs.  That's it.  A modern docking system can weight several hundred pounds.  Not quite apples to apples, but it gives a sense of scale.
100lb or more for a passive capability? I find that hard to believe, but I’ll take your word for it.

If we’re not using the advantages of a modern docking system, we should go back to a drogue and cone system and save even more weight.

I'm getting really confused here. 

I thought that the difference between an active and a passive IDSS-compliant system is that the active system (of which NDS is an implementation) has the extendable soft-capture system, which has latches that engage with the passive system's petals.  Then, once the soft-capture system retracts, active hooks on the active system engage with passive hooks on the passive system.

I can't see how a passive system would be heavier.  Maybe some of the confusion is that the ISS's IDA is actually an adapter to make APAS IDSS-compliant?  You wouldn't need that if you were to implement an IDSS passive system from scratch.

IDSS allows for active-active systems, doesn't it?  So the real question is whether NDS has implemented active-active, or whether it's only able to be the active component of an active-passive system.  Which is it?

There has to be a plan that makes sense here, because HLS without a Gateway is going to have to dock with Orion (an active NDS system), which would require HLS to be passive if NDS is only active-passive.  But Orion is also going to have to dock with the Gateway, and if it's only active-passive, then the dock at the Gateway would have to be passive.  But then HLS can't dock at the gateway.

So you have two options:

1) You have separate active and passive docking ports on the Gateway, which is just dumb.

2) The HLS has to be able to work in both active-active mode (for docking with Orion) and active-passive mode (for docking with the GW).

I assume that active-active really means that one side decides to be passive and leaves its SCS retracted, and that side is the passive recipient of the active hard-capture hooks.  By that logic, HLS will be and active-active system (i.e., capable of being either active or passive).

All that said, and in a feeble attempt to remain vaguely on-topic, that would mean that the DXL could just have a vanilla-flavored active-passive NDS, to dock with the passive Gateway port.  But if you ever wanted to use a DXL and a D2 in some mated configuration (which is definitely not a NASA requirement, but I think was how we wound up down this particular rabbit hole), SpaceX would have to implement active-active functionality on both vehicles.

How badly have I misunderstood this?

Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #33 on: 03/31/2020 11:54 pm »
100lb or more for a passive capability? I find that hard to believe, but I’ll take your word for it.

If we’re not using the advantages of a modern docking system, we should go back to a drogue and cone system and save even more weight.

It's probably not that much, I dunno probably somewhere around 20-80?  It's passive hooks, thick Bellevue washer springs, back structure to support the hooks, passive hook explosive bolts for contingency release, wiring, strikers mounted somewhere to something and associated back structure, docking alignment cross, reflectors, ship to ship telemetry.... 

Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #34 on: 04/01/2020 12:06 am »
I'm getting really confused here. 

I thought that the difference between an active and a passive IDSS-compliant system is that the active system (of which NDS is an implementation) has the extendable soft-capture system, which has latches that engage with the passive system's petals.  Then, once the soft-capture system retracts, active hooks on the active system engage with passive hooks on the passive system.

generally correct.
Quote

I can't see how a passive system would be heavier.  Maybe some of the confusion is that the ISS's IDA is actually an adapter to make APAS IDSS-compliant?  You wouldn't need that if you were to implement an IDSS passive system from scratch.

To be androgynous, the Active needs additional structure, passive hooks, wiring, strikers, back structure to support docking loads, as well as sensors.  A pure passive would not be heavier.
Quote

IDSS allows for active-active systems, doesn't it?  So the real question is whether NDS has implemented active-active, or whether it's only able to be the active component of an active-passive system.  Which is it?

NDS Block 1 is active-passive (CST-100 to IDA/ISS).  I don't know about Block 2, I think it might be fully androgynous (Orion/Gateway).  Neither has flown yet, B1 will fly on the first CST-100 mission, as far as I know.
Quote

There has to be a plan that makes sense here, because HLS without a Gateway is going to have to dock with Orion (an active NDS system), which would require HLS to be passive if NDS is only active-passive.  But Orion is also going to have to dock with the Gateway, and if it's only active-passive, then the dock at the Gateway would have to be passive.  But then HLS can't dock at the gateway.
See previous posts about HLS appendix and possible gateway adapter (if I understand it right)
Quote

So you have two options:

1) You have separate active and passive docking ports on the Gateway, which is just dumb.
I realize it seems dumb, but if they did do that, it's a question of cost.  Cost of an active is much much greater than a passive.  Also time to actually build.  (as I understand it, I might have that wrong).  If you want to send up the gateway Hab as soon as possible, makes more sense to build passives and send up adapters, than sit on it while an active gets built?  maybe?
Quote


2) The HLS has to be able to work in both active-active mode (for docking with Orion) and active-passive mode (for docking with the GW).

...

How badly have I misunderstood this?

Not too bad!

Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #35 on: 04/01/2020 12:15 am »
A problem with the active-active adapter for Gateway is it's going to compromise the rigidity and strength of the whole Gateway/visiting-vehicle stack. There's already a mass limit on Gateway-docking visiting vehicles, and having to use an adapter would theoretically reduce that allowable limit (longer moment arm for an already-long vehicle, additional flex which reduces the fundamental frequency and makes control harder, etc) besides adding more things that can fail and reducing inherent redundancy. I'm not sure that's captured by the requirements fully in a way that allows fair scoring, so that could be one area where the non-androgynous approach ends up penny-wise but pound-foolish.
« Last Edit: 04/01/2020 12:20 am by Robotbeat »
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Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #36 on: 04/01/2020 12:26 am »
A problem with the active-active adapter for Gateway is it's going to compromise the rigidity and strength of the whole Gateway/visiting-vehicle stack. There's already a mass limit on Gateway-docking visiting vehicles, and having to use an adapter would theoretically reduce that allowable limit (longer moment arm for an already-long vehicle, additional flex which reduces the fundamental frequency and makes control harder, etc) besides adding more things that can fail and reducing inherent redundancy. I'm not sure that's captured by the requirements fully in a way that allows fair scoring, so that could be one area where the non-androgynous approach ends up penny-wise but pound-foolish.

why wouldn't it stay attached to the gateway?

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Re: Re: SpaceX Dragon XL
« Reply #37 on: 04/01/2020 12:28 am »
A problem with the active-active adapter for Gateway is it's going to compromise the rigidity and strength of the whole Gateway/visiting-vehicle stack. There's already a mass limit on Gateway-docking visiting vehicles, and having to use an adapter would theoretically reduce that allowable limit (longer moment arm for an already-long vehicle, additional flex which reduces the fundamental frequency and makes control harder, etc) besides adding more things that can fail and reducing inherent redundancy. I'm not sure that's captured by the requirements fully in a way that allows fair scoring, so that could be one area where the non-androgynous approach ends up penny-wise but pound-foolish.

why wouldn't it stay attached to the gateway?
I didn’t say it wouldn’t. It still compromises the Gateway/VV stack.
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Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #38 on: 04/01/2020 12:37 am »
A problem with the active-active adapter for Gateway is it's going to compromise the rigidity and strength of the whole Gateway/visiting-vehicle stack. There's already a mass limit on Gateway-docking visiting vehicles, and having to use an adapter would theoretically reduce that allowable limit (longer moment arm for an already-long vehicle, additional flex which reduces the fundamental frequency and makes control harder, etc) besides adding more things that can fail and reducing inherent redundancy. I'm not sure that's captured by the requirements fully in a way that allows fair scoring, so that could be one area where the non-androgynous approach ends up penny-wise but pound-foolish.

why wouldn't it stay attached to the gateway?
I didn’t say it wouldn’t. It still compromises the Gateway/VV stack.

Wouldn't affect mass limit if it stays attached

bending moment ... nah...  but you couldn't really know that.  Just consider that docking is bounded by shuttle's off center CG, capsules don't put nearly the moment in.

can't be lower than the ISS fundamental frequency, lol

reducing redundancy more than a ISS made up of CBM's and other docking ports?  See also frequency through all those ports.

Just isn't an issue.  You aren't wrong that all those things detract, just not as much as you think.  And in the grand scheme, nothing in comparison to saving mass on a lander.

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Re: Re: SpaceX Dragon XL
« Reply #39 on: 04/01/2020 12:53 am »
A problem with the active-active adapter for Gateway is it's going to compromise the rigidity and strength of the whole Gateway/visiting-vehicle stack. There's already a mass limit on Gateway-docking visiting vehicles, and having to use an adapter would theoretically reduce that allowable limit (longer moment arm for an already-long vehicle, additional flex which reduces the fundamental frequency and makes control harder, etc) besides adding more things that can fail and reducing inherent redundancy. I'm not sure that's captured by the requirements fully in a way that allows fair scoring, so that could be one area where the non-androgynous approach ends up penny-wise but pound-foolish.

why wouldn't it stay attached to the gateway?
I didn’t say it wouldn’t. It still compromises the Gateway/VV stack.

Wouldn't affect mass limit if it stays attached

bending moment ... nah...  but you couldn't really know that.  Just consider that docking is bounded by shuttle's off center CG, capsules don't put nearly the moment in.

can't be lower than the ISS fundamental frequency, lol

reducing redundancy more than a ISS made up of CBM's and other docking ports?  See also frequency through all those ports.

Just isn't an issue.  You aren't wrong that all those things detract, just not as much as you think.  And in the grand scheme, nothing in comparison to saving mass on a lander.
From what I understand, the Gateway’s mass limit is for any visiting vehicle and is driven by PPE’s control authority which is limited (and sure, ISS is worse, but PPE is not designed for torquing ISS around, just the Gateway stack). I’m not talking about lander performance or launch vehicle limits.

And yeah, ISS always has redundant CBMs and NDSes and probe&drogues. It has a lot more redundancy.
« Last Edit: 04/01/2020 01:02 am by Robotbeat »
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Offline kkattula

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Re: Re: SpaceX Dragon XL
« Reply #40 on: 04/01/2020 04:14 am »
So then surely it would make sense for the Gateway modules to have androgynous docking adapters, so they can do both passive with active Orion & Dragon XL, and do active with passive HLS?

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Re: Re: SpaceX Dragon XL
« Reply #41 on: 04/01/2020 05:49 am »
I'm getting really confused here. 

I thought that the difference between an active and a passive IDSS-compliant system is that the active system (of which NDS is an implementation) has the extendable soft-capture system, which has latches that engage with the passive system's petals.  Then, once the soft-capture system retracts, active hooks on the active system engage with passive hooks on the passive system.

generally correct.
Quote

I can't see how a passive system would be heavier.  Maybe some of the confusion is that the ISS's IDA is actually an adapter to make APAS IDSS-compliant?  You wouldn't need that if you were to implement an IDSS passive system from scratch.

To be androgynous, the Active needs additional structure, passive hooks, wiring, strikers, back structure to support docking loads, as well as sensors.  A pure passive would not be heavier.
Quote

IDSS allows for active-active systems, doesn't it?  So the real question is whether NDS has implemented active-active, or whether it's only able to be the active component of an active-passive system.  Which is it?

NDS Block 1 is active-passive (CST-100 to IDA/ISS).  I don't know about Block 2, I think it might be fully androgynous (Orion/Gateway).  Neither has flown yet, B1 will fly on the first CST-100 mission, as far as I know.
Quote

There has to be a plan that makes sense here, because HLS without a Gateway is going to have to dock with Orion (an active NDS system), which would require HLS to be passive if NDS is only active-passive.  But Orion is also going to have to dock with the Gateway, and if it's only active-passive, then the dock at the Gateway would have to be passive.  But then HLS can't dock at the gateway.
See previous posts about HLS appendix and possible gateway adapter (if I understand it right)
Quote

So you have two options:

1) You have separate active and passive docking ports on the Gateway, which is just dumb.
I realize it seems dumb, but if they did do that, it's a question of cost.  Cost of an active is much much greater than a passive.  Also time to actually build.  (as I understand it, I might have that wrong).  If you want to send up the gateway Hab as soon as possible, makes more sense to build passives and send up adapters, than sit on it while an active gets built?  maybe?
Quote


2) The HLS has to be able to work in both active-active mode (for docking with Orion) and active-passive mode (for docking with the GW).

...

How badly have I misunderstood this?

Not too bad!

Thanks for the info.  So passive would be the lightest, active-only would be heavier, and active-active would be heavier still?

Is the D2 docking port not an NDSB1 implementation?

Offline russianhalo117

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Re: Re: SpaceX Dragon XL
« Reply #42 on: 04/01/2020 06:03 am »
So then surely it would make sense for the Gateway modules to have androgynous docking adapters, so they can do both passive with active Orion & Dragon XL, and do active with passive HLS?
Increases mass and cost to have all ports be active. I would only expect the end cone ports to be active as they will be along the velocity vector when initially docking. When moved by arm to their final spot they can be berthed passive mode like a CBM. The IDSS specs did account for active-active and passive-passive configurations however nominal dockings will always have one active side in passive mode.

On ISS only one of the PMA's were active mode capable because of shuttle station interactions and it has only been used by PMA-1 to dock with FGB. APAS-89 both sides were active capable whereas APAS-95 was strengthened for shuttle thus only the shuttle side was active. PMA-1 and FGB Interfaces were designed APAS-89 with modifications.

Reference this thread: https://forum.nasaspaceflight.com/index.php?topic=5863.0
« Last Edit: 04/01/2020 06:32 am by russianhalo117 »

Online TheRadicalModerate

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Re: Re: SpaceX Dragon XL
« Reply #43 on: 04/01/2020 06:22 am »
So then surely it would make sense for the Gateway modules to have androgynous docking adapters, so they can do both passive with active Orion & Dragon XL, and do active with passive HLS?
Increases mass and cost to have all ports be active. I would only expect the end cone ports to be active as they will be along the velocity vector when initially docking. When moved by arm to their final spot they can be berthed passive mode like a CBM. The IDSS specs did account for active-active and passive-passive configurations however nominal dockings will always have one active side in passive mode.

Who has the hard-dock hooks in a passive-passive docking, even if it's berthed?  I can't see how it would work even in an off-nominal emergency.

Offline woods170

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Re: Re: SpaceX Dragon XL
« Reply #44 on: 04/01/2020 07:34 am »
How hard would it be to retrofit passive elements to an existing design? Is the lack of strikers or hooks a critical design flaw, or is it something that can be rectified if SpaceX actually cared?

I think you are missing the point.  Everything is built to the minimum that meets requirements.  Every extra thing, passive docking components, airlocks, it's not just the hardware, it's the money to build it, test it, the documentation to certify it.  I know many people on this forum think it's easy, and sure it's not that hard to get the machinists to build it.  But certifying it is probably more the double the cost and more critically, the time.

Every time you add something, you need to think about "what if".  What if something fails, then something else fails, or combinations of other failures.  Every "what if" is analysis and documentation and meetings.  Now multiply that by every component - the work load becomes exponential.  Minimum Viable Product is the name of the game.
It's interesting, because lack of passive capability reduces safety of the IDSS design. One of the main features of an androgynous design (over probe and drogue, for instance) is ability to rescue and overall operational flexibility and contingency.

Emphasis mine.

Which does not apply to Crew Dragon.

When a Crew Dragon gets into trouble either BEFORE docking to the ISS, or AFTER undocking from the ISS, the prudent thing to do is to de-orbit to the safety of the planet surface.

If however such a "into trouble" scenario strands the crew in orbit, without any possibilty of either de-orbiting or docking with the ISS, than they are a lost cause. You see, in no way would SpaceX, or any other launch provider, be able to launch a rescue vehicle within the five days before the ECLSS consumables run out on Crew Dragon.

When Crew Dragon gets into trouble while docked to the ISS the crew can shelter in place aboard the ISS.

As such, there are no scenarios where the docking system on Crew Dragon is required to be fully androgynous. Which is exactly why it IS NOT fully androgynous.

Offline woods170

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Re: Re: SpaceX Dragon XL
« Reply #45 on: 04/01/2020 07:40 am »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”

Wrong.

When Crew Dragon launches into orbit, there is no second Crew Dragon on stand-by for a fast rescue launch. Neither is a Starliner standing by. Nor an Orion.
And vice versa.

The scenario where a rescue vehicle was standing by for fast rescue launch only existed in the post-Columbia shuttle era.

Both Orion and the CCP vehicles are required to be robust enough to get themselves out of trouble.

Offline woods170

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Re: Re: SpaceX Dragon XL
« Reply #46 on: 04/01/2020 07:54 am »
This latter sentence seems false. For instance:

Original plan is Gateway goes up first. Both lander and Orion need active systems to dock to the passive gateway. But! Current plan is to skip Gateway and dock directly to each other for the first mission, and then *later* go back to the original plan (so that the lander ascent stage can be docked to Gateway between missions for reuse). So, given NASA's current plans, the lander at least MUST be androgynous if we're to keep its configuration the same.

I read "HLS_Appendix_H_BAA_2019-10-02c.pdf" page 9, CLIN 009 - Option A: Docking System.  Work on a detachable docking adapter...  As to mean an adapter to make a port on the gateway active instead of passive.  How do you read that?
Ah, you got me.

Looks like NASA is *allowing* HLS offerers to have passive-only on their lander PROVIDED they also build an active-active adapter for the gateway. But I see this as merely allowing the maximum possible options to be considered, whether or not they’re a good idea.

Insane to me that we’re actually talking about building a separate chunk of flight hardware as a kludge to avoid building the adapter fully to the androgynous spec of IDSS.

That means that you have less redundancy as you cannot swap Orion and the lander’s docking ports.

I pray that whatever bean counter you work with that is insisting on doing this kludge instead of building androgynous capability right the first time changes their mind.

Same for SpaceX.

Really, NASA ought to be insisting on androgynous capability at least for everything that needs to be active plus the lander. I means seriously, adding an extra docking adapter just to avoid making the lander or Orion androgynous! Insane.

That’s just my personal opinion, though.

Jarmund's original point was about the current CCP vehicles not having fully androgynous docking systems.

That says exactly NOTHING about the nature of the docking system that will be on Dragon XL.

What DOES have influence on the docking system on Dragon XL is the requirements laid down by NASA. And currently NASA only requires Dragon XL to have an active docking system. Because Gateway, like the ISS, is designated the passive vehicle in a docking. Gateway, like ISS, wil have fully androgynous IDSS compliant docking systems. But the visiting vehicles are not required to have those as well. Only the active part.

If you find fault in that, than it is not the right thing to "hope" that SpaceX will come to its senses. You should complain to NASA for laying down "incomplete" requirements.

Remember, SpaceX builds this stuff exclusively for NASA, to fit NASA requirements. Adding extras, which are not required by NASA, is usually not done in the aerospace industry. Not even by SpaceX. The one exception being the port-a-potty on Crew Dragon.

Offline woods170

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Re: Re: SpaceX Dragon XL
« Reply #47 on: 04/01/2020 07:57 am »
It’s impossible to use dragon XL as a mission-extending mini-station as supposed here if it doesn’t have an androgynous (or passive) docking capability.

You said it: "as supposed here".

SpaceX is not seriously considering using Dragon XL as a mission-extending mini-station. That is just an idea floated here by NSF members. Not rooted in reality.

Online kevinof

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Re: Re: SpaceX Dragon XL
« Reply #48 on: 04/01/2020 08:15 am »
Yeah I think we tend to get carried away here on NSF with "oh you could do this or that and this also". Dragon XL is an interim , stop-gap offering to Nasa. It's not on the long term path for SpaceX and as soon as Starship is viable, they would dump Dragon XL and go just with SS.

This is a minimum viable product for SpaceX. It's doing a little as necessary to fulfill the needs of Nasa while keeping costs down and not distracting from SS. Adding bells and whistles to DragonXL is great for us here on NSF but does not make sense to SpaceX given the requirements and also the direction they want to go in.


It’s impossible to use dragon XL as a mission-extending mini-station as supposed here if it doesn’t have an androgynous (or passive) docking capability.

You said it: "as supposed here".

SpaceX is not seriously considering using Dragon XL as a mission-extending mini-station. That is just an idea floated here by NSF members. Not rooted in reality.

Offline tyrred

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Re: Re: SpaceX Dragon XL
« Reply #49 on: 04/01/2020 09:05 am »
I think some of the younger people also may succumb to KSP syndrome, where every module with a docking port can dock to every other module with a docking port of the same size.  Rockets aren't LEGO Elements. 

Why can't my Yaris dock with Dragon XL?  Oh, yeah nobody wants to launch my Yaris into orbit except for me  8)

It looks like that's not happening, so I guess SpaceX is planning on going to resupply the Gateway instead.

Offline baldusi

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Re: Re: SpaceX Dragon XL
« Reply #50 on: 04/01/2020 09:09 am »
Do not want to beat a dead horse, but Revision E of the IDSS standard also adds the retroreflectors to the passive side for final navigation and alignment. So that's another set of things that you would have to add if you wanted fully androgynous interface. Just saying that it's not that easy to do.
« Last Edit: 04/01/2020 09:09 am by baldusi »

Offline mikelepage

Re: Re: SpaceX Dragon XL
« Reply #51 on: 04/01/2020 09:20 am »
Fully agreed btw.  The format of my post floating the idea was simply:
1) Can it be done? (D2 to DXL docking)
2) if so, potential revenue opportunity in the form of LEO operations.

I'm optimistic about Starship/Superheavy being ready for cargo in near future.  Human-rating it seems like it has ample opportunity to take considerably longer and be considerably more expensive than projected.

Dragon XL to Gateway is one way to use proven hardware/processes to generate revenue in that eventuality.  It seemed like a natural progression to use that hardware to do other revenue-generating activities as well. 

Yeah I think we tend to get carried away here on NSF with "oh you could do this or that and this also". Dragon XL is an interim , stop-gap offering to Nasa. It's not on the long term path for SpaceX and as soon as Starship is viable, they would dump Dragon XL and go just with SS.

This is a minimum viable product for SpaceX. It's doing a little as necessary to fulfill the needs of Nasa while keeping costs down and not distracting from SS. Adding bells and whistles to DragonXL is great for us here on NSF but does not make sense to SpaceX given the requirements and also the direction they want to go in.


It’s impossible to use dragon XL as a mission-extending mini-station as supposed here if it doesn’t have an androgynous (or passive) docking capability.

You said it: "as supposed here".

SpaceX is not seriously considering using Dragon XL as a mission-extending mini-station. That is just an idea floated here by NSF members. Not rooted in reality.
« Last Edit: 04/01/2020 09:21 am by mikelepage »

Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #52 on: 04/01/2020 10:31 am »
It’s impossible to use dragon XL as a mission-extending mini-station as supposed here if it doesn’t have an androgynous (or passive) docking capability.

You said it: "as supposed here".

SpaceX is not seriously considering using Dragon XL as a mission-extending mini-station. That is just an idea floated here by NSF members. Not rooted in reality.
Welcome to NSF! Always glad to have new members. 😂
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Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #53 on: 04/01/2020 10:32 am »
I think some of the younger people also may succumb to KSP syndrome, where every module with a docking port can dock to every other module with a docking port of the same size.  Rockets aren't LEGO Elements. 

Why can't my Yaris dock with Dragon XL?  Oh, yeah nobody wants to launch my Yaris into orbit except for me  8)

It looks like that's not happening, so I guess SpaceX is planning on going to resupply the Gateway instead.
Spacecraft aren’t LEGOs when they’re specifically engineered not to be.
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Re: Re: SpaceX Dragon XL
« Reply #54 on: 04/01/2020 10:32 am »
Do not want to beat a dead horse, but Revision E of the IDSS standard also adds the retroreflectors to the passive side for final navigation and alignment. So that's another set of things that you would have to add if you wanted fully androgynous interface. Just saying that it's not that easy to do.
Well understood by all.
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Re: Re: SpaceX Dragon XL
« Reply #55 on: 04/01/2020 10:35 am »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”

Wrong.

When Crew Dragon launches into orbit, there is no second Crew Dragon on stand-by for a fast rescue launch. Neither is a Starliner standing by. Nor an Orion.
And vice versa.

The scenario where a rescue vehicle was standing by for fast rescue launch only existed in the post-Columbia shuttle era.

Both Orion and the CCP vehicles are required to be robust enough to get themselves out of trouble.
If Dragon or Starliner has a problem detected with their landing system when near ISS but cannot dock, another visiting vehicle could dock with them.
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Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #56 on: 04/01/2020 10:37 am »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”

Wrong.

When Crew Dragon launches into orbit, there is no second Crew Dragon on stand-by for a fast rescue launch. Neither is a Starliner standing by. Nor an Orion.
And vice versa.

The scenario where a rescue vehicle was standing by for fast rescue launch only existed in the post-Columbia shuttle era.

Both Orion and the CCP vehicles are required to be robust enough to get themselves out of trouble.
If Dragon or Starliner has a problem detected with their landing system when near ISS but cannot dock, another visiting vehicle could dock with them if there was true androgynous capability.

Of course I understand rockets aren’t Legos. But these aren’t rockets, they’re spacecraft with standard interfaces, interfaces explicitly standardized (originally) with the idea of the possibility of rescue by different vehicles in mind. So incompatibility is a design decision by the customer (NASA).
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Offline soltasto

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Re: Re: SpaceX Dragon XL
« Reply #57 on: 04/01/2020 10:38 am »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”

Wrong.

When Crew Dragon launches into orbit, there is no second Crew Dragon on stand-by for a fast rescue launch. Neither is a Starliner standing by. Nor an Orion.
And vice versa.

The scenario where a rescue vehicle was standing by for fast rescue launch only existed in the post-Columbia shuttle era.

Both Orion and the CCP vehicles are required to be robust enough to get themselves out of trouble.
If Dragon or Starliner has a problem detected with their landing system when near ISS but cannot dock, another visiting vehicle could dock with them.
Ehm, it doesn't make any sense.  Either your are able to or you are not.

Offline danneely

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Re: Re: SpaceX Dragon XL
« Reply #58 on: 04/01/2020 11:14 am »
It's interesting, because lack of passive capability reduces safety of the IDSS design. One of the main features of an androgynous design (over probe and drogue, for instance) is ability to rescue and overall operational flexibility and contingency.

In general, you aren't wrong, but where we are today it doesn't matter.  For instance, to your points on rescue, operational flexibility, contingency....     how?  Rescue what?

What would the scenario have to be to have Orion or CST-100 dock to a Dragon (if it was equipped)?  In any contingency you might be thinking of, the existing spacecraft must have enough redundancies and equipment to make it back to earth safely.  Why design for something that is so far out of the fault space?  There is no reasonable circumstance in which you could launch a rescue spacecraft in time to do anything.  The exception to this is if one is already docked to the ISS.

And if you are already at the ISS, what's the point? 

If a spacecraft is so damaged it cannot return to earth, are you sure it could even be docked to?

In case my tone comes across wrong, understand that I do agree with you in principal, but once you go down the rabbit hole, you'll see there just isn't a credible reason now to have this capability, and I haven't seen a reasonable need to have it in the future, specifically for commercial crew or cargo resupply.

It's a good point.  The only way I see it working is how they did it with shuttle at the end, with every manned U.S space launch, a secondary option must be ready to launch within a given time frame (48/72 hours?).  With Orion, Starliner and Crew Dragon, we have the options.

I think it wouldn't hurt to consider that as a possibility. NASA did indeed make it the regular practice on the last dozen Shuttle flights. It wouldn't be too great of a burden on SpaceX, would be a much greater burden for Starliner.

Only the hubble repair mission had a second shuttle ready to go for an emergency.  Everything else was an ISS flight, and the emergency plan was to hang out there for a few months if the shuttle broke.

Offline rakaydos

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Re: Re: SpaceX Dragon XL
« Reply #59 on: 04/01/2020 11:37 am »
There's no rescue mission set up for crewed flights to the ISS, because in a crisis the iss itself functions as the rescue vehical. And other than the last few shuttle missions, there hasnt been any crewed flights that were NOT to the ISS, not since the second shuttle exploded.

But with Artemis, Gateway, and Mars all on the horizon, that will shortly no longer be the case.


Offline woods170

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Re: Re: SpaceX Dragon XL
« Reply #60 on: 04/01/2020 11:40 am »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”

Wrong.

When Crew Dragon launches into orbit, there is no second Crew Dragon on stand-by for a fast rescue launch. Neither is a Starliner standing by. Nor an Orion.
And vice versa.

The scenario where a rescue vehicle was standing by for fast rescue launch only existed in the post-Columbia shuttle era.

Both Orion and the CCP vehicles are required to be robust enough to get themselves out of trouble.
If Dragon or Starliner has a problem detected with their landing system when near ISS but cannot dock, another visiting vehicle could dock with them.

A problem with the landing system will - in fact - be detected even before the vehicle undocks from ISS. The CCP vehicles are thoroughly checked out BEFORE undocking. That is why there is an URR (Undocking Readiness Review). Same was done with shuttle.

Problems with the landing system don't crop up two seconds after undock. Most likely time for an undetected problem with the landing system manifesting itself is when the landing system is activated. And in case of the CCP vehicles that is far past the point that any rescue docking could be performed.

Also, under the scenario you picture there would actually have to be another IDSS compliant vehicle present at the station. Which, in many cases, there won't be. Crew rotation to and from ISS in the CCP era is a mix of CCP vehicles and Soyuz. Needless to say, Soyuz doesn't carry an IDSS compliant docking system. And Starliner being present at the ISS when a Crew Dragon arrives or leaves is not a given (and vice versa).

Offline DistantTemple

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Re: Re: SpaceX Dragon XL
« Reply #61 on: 04/01/2020 11:56 am »
SpaceX looks as if "emergency launch capability" IS something they could offer in the near future. They have a stock of used boosters, and a production line of second stages.

It is something I imagine the military would be interested in. It certainly appears to be an additional protection for HSF, and even communications satellite operators may benefit from it!

I bet even now SX could launch within a week, if they could "steal" components lined up for less critical customers. In many cases this would not even delay such bumped customers much if the boosters and second stages are thoughtfully shuffled/reassigned.

Further if it was a paid for service for NASA and/or USGOV/military/Spaceforce then an additional hanger containing a couple of F9's and a couple of 2nd stages, some standard docking adaptors, and one D2 including an androgynous port, would cover the preparation.  The facility would not need to be dedicated, just additional space, with deliberate "extra stock" to guarantee the "contingency programme".

With a bit of forethought I bet SX could put up an emergency crew rescue within 3 days! Therefore planing to have an androgynous docking capability should not be ruled out. (It would require a spare and ready crew vehicle.)

There is also berthing. I thought I read that in the DXL documents. ( This is off topic but related: And there is also the possibility of spacewalking to the other vehicle, however without airlocks, that means bringing the vehicles to vacuum, and everyone having to be suited up - apart from anyone who can retreat to another connected module and close the hatch there.)

I have just read jarmund's, and other posts and replies just written above. But I will still post this. "If its too damaged to return, will it be too damaged to dock?" That needs more thought than a one-liner assumption! 

Edit: I am avidly reading all woods170's input (and the others discussing it). I am not arguing against what he knows and says is happening now, or the info he has from SX sources. But ISTM the general argument against SX having an emergency launch, and even astronaut rescue capability is not over, and becomes more compelling as their developments continue.
« Last Edit: 04/01/2020 02:26 pm by DistantTemple »
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Online Robotbeat

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Re: Re: SpaceX Dragon XL
« Reply #62 on: 04/01/2020 01:33 pm »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”

Wrong.

When Crew Dragon launches into orbit, there is no second Crew Dragon on stand-by for a fast rescue launch. Neither is a Starliner standing by. Nor an Orion.
And vice versa.

The scenario where a rescue vehicle was standing by for fast rescue launch only existed in the post-Columbia shuttle era.

Both Orion and the CCP vehicles are required to be robust enough to get themselves out of trouble.
If Dragon or Starliner has a problem detected with their landing system when near ISS but cannot dock, another visiting vehicle could dock with them.
Ehm, it doesn't make any sense.  Either your are able to or you are not.
RCS failure, but attitude control remains. Also, failure of the instruments for docking.
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Offline woods170

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Re: Re: SpaceX Dragon XL
« Reply #63 on: 04/01/2020 03:08 pm »
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t.

“I thought you said the port was androgynous?”
“Well, see the thing is...”

Wrong.

When Crew Dragon launches into orbit, there is no second Crew Dragon on stand-by for a fast rescue launch. Neither is a Starliner standing by. Nor an Orion.
And vice versa.

The scenario where a rescue vehicle was standing by for fast rescue launch only existed in the post-Columbia shuttle era.

Both Orion and the CCP vehicles are required to be robust enough to get themselves out of trouble.
If Dragon or Starliner has a problem detected with their landing system when near ISS but cannot dock, another visiting vehicle could dock with them.
Ehm, it doesn't make any sense.  Either your are able to or you are not.
RCS failure, but attitude control remains. Also, failure of the instruments for docking.

You are now talking multiple failures. Not only a failure of the landing system, but failure of RCS or docking instruments as well. Your failure scenario to justify androgynous docking system on CCP vehicles is becoming more-and-more unlikely.

RCS failure would be detected before undocking, due to earlier mentioned checkout of the vehicle prior to undocking. Same for docking instruments.

Besides, the CCP vehicles have back-ups for failure of the automated docking instruments. Like boresight camera's, handheld laser range finders, etc.

RCS is multiple redundant on both CCP vehicles. No way to lose ALL of the RCS yet still have attitude control.

You're grasping for straws here.

Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #64 on: 04/01/2020 04:34 pm »
Who has the hard-dock hooks in a passive-passive docking, even if it's berthed?  I can't see how it would work even in an off-nominal emergency.

So there several things here.  If you used an arm to berth a docking system, one of the systems would still need to drive their "active hooks" - just maybe not their active soft capture system.  So it's probably never completely true to have passive-passive docking, one side has to do something!  Technically either side could drive hooks*.

* SpaceX Docking System must be the active because it doesn't have passive hooks, only active hooks; NDS-B1/B2, IDA have both sets.

Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #65 on: 04/01/2020 04:40 pm »
Is the D2 docking port not an NDSB1 implementation?
Nope. Some parts are similar or exact, others are different.

Minor nit, The SpaceX Docking System is an implementation of the Nasa Docking System (NDS), which is a derivative of the IDSS.  NDS-B1/B2 is a specific mechanism, built by Boeing for NASA.  It's a bit confusing.

Offline russianhalo117

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Re: Re: SpaceX Dragon XL
« Reply #66 on: 04/01/2020 07:02 pm »
So then surely it would make sense for the Gateway modules to have androgynous docking adapters, so they can do both passive with active Orion & Dragon XL, and do active with passive HLS?
Increases mass and cost to have all ports be active. I would only expect the end cone ports to be active as they will be along the velocity vector when initially docking. When moved by arm to their final spot they can be berthed passive mode like a CBM. The IDSS specs did account for active-active and passive-passive configurations however nominal dockings will always have one active side in passive mode.

Who has the hard-dock hooks in a passive-passive docking, even if it's berthed?  I can't see how it would work even in an off-nominal emergency.
Both sides have both a passive set of hooks and an active set of hooks. For example this is the case the PMA's, IDA's and the Russian hybrid SSVP-M8000 and successor SSPA-GM docking ports (SSPA-GM is used on MLM-U and all future RS modules and visiting spacecraft. It supports both Drogue and Cone as well as APAS passive SCS petals which can be removed from there storage position and installed in their docking position either via IVA or while a spacecraft is docked). The SSPA-GM docking ports are also IDSS ready and only require an outfitting EVA to install the retroreflector system and other components. The Soft Capture System/Magnetic Capture System is not required to be deployed when an arm is used depending upon the size and mass of the object being moved and installed. For permanently installed modules both sets of HCS latches are driven closed. Per the standard for VV's it is at the discretion of the entity whether drive and engage both sets.
« Last Edit: 04/01/2020 07:08 pm by russianhalo117 »

Offline Negan

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Re: Re: SpaceX Dragon XL
« Reply #67 on: 04/01/2020 07:14 pm »
My guess would be whatever pressurized docking system Starship will use to dock to another Starship will also be an option for its other spacecraft. They won't be sending multiple crewed Starships to Mars without this ability.
« Last Edit: 04/02/2020 02:58 pm by Negan »

Offline gemmy0I

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Re: Re: SpaceX Dragon XL
« Reply #68 on: 04/01/2020 08:58 pm »
Both sides have both a passive set of hooks and an active set of hooks. For example this is the case the PMA's, IDA's and the Russian hybrid SSVP-M8000 and successor SSPA-GM docking ports (SSPA-GM is used on MLM-U and all future RS modules and visiting spacecraft. It supports both Drogue and Cone as well as APAS passive SCS petals which can be removed from there storage position and installed in their docking position either via IVA or while a spacecraft is docked). The SSPA-GM docking ports are also IDSS ready and only require an outfitting EVA to install the retroreflector system and other components. The Soft Capture System/Magnetic Capture System is not required to be deployed when an arm is used depending upon the size and mass of the object being moved and installed. For permanently installed modules both sets of HCS latches are driven closed. Per the standard for VV's it is at the discretion of the entity whether drive and engage both sets.
Fascinating info here, thanks for sharing!

At the risk of taking this thread (hopefully not too far) off-topic, just so I'm understanding what you're saying here: are you saying that all the Russian docking ports currently on the station are hybrids capable of being converted to APAS with a relatively simple EVA to install a few pieces of hardware already on-station? And that Nauka's new docking port will come pre-configured able to support either probe-and-drogue or IDSS dockings, so long as some simple reflectors and other components are installed on EVA?

Does this apply to visiting Soyuz and Progress vehicles' docking ports as well, i.e. are the ones currently in use "ready" to be converted to dock at an IDSS port with the addition of a few simple pieces of hardware during pre-launch outfitting?

Does this mean that the Shuttle could hypothetically have docked to Zvezda in a contingency situation, requiring only an IVA (or simply internal work while a Soyuz/Progress was docked) to install the APAS compatibility petals?

Offline russianhalo117

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Re: Re: SpaceX Dragon XL
« Reply #69 on: 04/01/2020 10:53 pm »
Both sides have both a passive set of hooks and an active set of hooks. For example this is the case the PMA's, IDA's and the Russian hybrid SSVP-M8000 and successor SSPA-GM docking ports (SSPA-GM is used on MLM-U and all future RS modules and visiting spacecraft. It supports both Drogue and Cone as well as APAS passive SCS petals which can be removed from there storage position and installed in their docking position either via IVA or while a spacecraft is docked). The SSPA-GM docking ports are also IDSS ready and only require an outfitting EVA to install the retroreflector system and other components. The Soft Capture System/Magnetic Capture System is not required to be deployed when an arm is used depending upon the size and mass of the object being moved and installed. For permanently installed modules both sets of HCS latches are driven closed. Per the standard for VV's it is at the discretion of the entity whether drive and engage both sets.
Fascinating info here, thanks for sharing!

At the risk of taking this thread (hopefully not too far) off-topic, just so I'm understanding what you're saying here: are you saying that all the Russian docking ports currently on the station are hybrids capable of being converted to APAS with a relatively simple EVA to install a few pieces of hardware already on-station? And that Nauka's new docking port will come pre-configured able to support either probe-and-drogue or IDSS dockings, so long as some simple reflectors and other components are installed on EVA?

Does this apply to visiting Soyuz and Progress vehicles' docking ports as well, i.e. are the ones currently in use "ready" to be converted to dock at an IDSS port with the addition of a few simple pieces of hardware during pre-launch outfitting?

Does this mean that the Shuttle could hypothetically have docked to Zvezda in a contingency situation, requiring only an IVA (or simply internal work while a Soyuz/Progress was docked) to install the APAS compatibility petals?
Sort of yes. Only the intermodule ports are compatible. The SSVP-G4000 ports where Soyuz, Progress and ATV dock are a flavour of the the original docking system on Almaz and Salyut and most ports on Mir. FGB's aft port was designed during early station operations to be converted to APAS to accept the never flown ICM in the event of SM failing to launch or indefinitely delayed due to Proton-K failures. The other SSVP-M8000 ports could not accept petals in flight but in all other respects are compatible in regards to its HCS.

See: http://russianspaceweb.com/docking.html for an explanation of docking ring types (not updated to reflect the new Russian implementation of IDSS).
« Last Edit: 04/01/2020 11:13 pm by russianhalo117 »

Offline baldusi

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Re: Re: SpaceX Dragon XL
« Reply #70 on: 04/02/2020 12:39 am »
I know NDS B1 has fixed petals. But does anything on the IDSS Rev E standard precludes the use of removable petals?

Offline jarmumd

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Re: Re: SpaceX Dragon XL
« Reply #71 on: 04/02/2020 01:33 am »
I know NDS B1 has fixed petals. But does anything on the IDSS Rev E standard precludes the use of removable petals?

Not to my knowledge, I think if you had a reason to have removable petals, you could.  It would be an operations thing though, since the astronauts would need to be trained in removing and attaching them.  And it would have to be on both sides, otherwise what's the point.

Offline baldusi

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #72 on: 04/02/2020 06:39 am »
The difference is 800mm vs 1100mm passage width. It's more than double the area. At least for the node ports, keeping the capability might be important. Unless they keep a CBM port.

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #73 on: 04/02/2020 02:38 pm »
The difference is 800mm vs 1100mm passage width. It's more than double the area. At least for the node ports, keeping the capability might be important. Unless they keep a CBM port.
Right. The docking port is the replacement for the CBM port in deep space and would be effectively permanent, so in some cases you might as well remove the petals.
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Offline Negan

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #74 on: 04/02/2020 03:33 pm »
Should Dragon 2's  for the private flights be androgynous?

Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #75 on: 04/02/2020 03:36 pm »
Should Dragon 2's  for the private flights be androgynous?
Yes. The Docking system is a permanently installed on each Dragon 2.

Offline jarmumd

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #76 on: 04/02/2020 04:02 pm »
The difference is 800mm vs 1100mm passage width. It's more than double the area. At least for the node ports, keeping the capability might be important. Unless they keep a CBM port.
Right. The docking port is the replacement for the CBM port in deep space and would be effectively permanent, so in some cases you might as well remove the petals.

There is a quote I love:  He who sets the requirements first, wins. 

It's probably the way of things to design anything you need to transfer, to be able to fit through the existing docking port.  Rather than to design the docking port for things that you don't know you need to transfer yet.

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #77 on: 04/02/2020 04:06 pm »
The difference is 800mm vs 1100mm passage width. It's more than double the area. At least for the node ports, keeping the capability might be important. Unless they keep a CBM port.
Right. The docking port is the replacement for the CBM port in deep space and would be effectively permanent, so in some cases you might as well remove the petals.

There is a quote I love:  He who sets the requirements first, wins. 

It's probably the way of things to design anything you need to transfer, to be able to fit through the existing docking port.  Rather than to design the docking port for things that you don't know you need to transfer yet.
I'm going to steal that quote.

It does tend to limit use of ISS spares and legacy hardware.
« Last Edit: 04/02/2020 04:07 pm by Robotbeat »
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Offline Negan

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #78 on: 04/02/2020 04:20 pm »
Should Dragon 2's  for the private flights be androgynous?
Yes. The Docking system is a permanently installed on each Dragon 2.

I meant fully androgynous.

In other words: two SpaceX docking systems can NOT dock to each other, because they are not fully androgynous. The active hooks on one side would find NO passive hooks on the other side to latch onto.

Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #79 on: 04/02/2020 06:56 pm »
Who has the hard-dock hooks in a passive-passive docking, even if it's berthed?  I can't see how it would work even in an off-nominal emergency.

So there several things here.  If you used an arm to berth a docking system, one of the systems would still need to drive their "active hooks" - just maybe not their active soft capture system.  So it's probably never completely true to have passive-passive docking, one side has to do something!  Technically either side could drive hooks*.

* SpaceX Docking System must be the active because it doesn't have passive hooks, only active hooks; NDS-B1/B2, IDA have both sets.
As with Rassvet installation on ISS docking system power, data and momentum required to engage the probe locking mechanism in the cone was done via the arm.

Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #80 on: 04/02/2020 07:02 pm »
Should Dragon 2's  for the private flights be androgynous?
Yes. The Docking system is a permanently installed on each Dragon 2.

I meant fully androgynous.

In other words: two SpaceX docking systems can NOT dock to each other, because they are not fully androgynous. The active hooks on one side would find NO passive hooks on the other side to latch onto.
Your docking logic is incorrect. Both sides each have a set 12 passive hooks and 12 active hooks. When both sets of active hooks are driven closed 24 active hooks engage 24 passive hooks which is 12 on the active HCS and 12 on the passive HCS. Read the IDSS Rev E document and view the relevant graphics to understand.

Offline Negan

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #81 on: 04/02/2020 07:15 pm »
Should Dragon 2's  for the private flights be androgynous?
Yes. The Docking system is a permanently installed on each Dragon 2.

I meant fully androgynous.

In other words: two SpaceX docking systems can NOT dock to each other, because they are not fully androgynous. The active hooks on one side would find NO passive hooks on the other side to latch onto.
Your docking logic is incorrect. Both sides each have a set 12 passive hooks and 12 active hooks. When both sets of active hooks are driven closed 24 active hooks engage 24 passive hooks which is 12 on the active HCS and 12 on the passive HCS. Read the IDSS Rev E document and view the relevant graphics to understand.

I'm going to believe woods170 logic on this.

Edit: As far as I know the private Dragon missions are not going to the ISS so the only option would be docking with another spacecraft.
« Last Edit: 04/02/2020 07:19 pm by Negan »

Offline jarmumd

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #82 on: 04/02/2020 07:23 pm »
Your docking logic is incorrect. Both sides each have a set 12 passive hooks and 12 active hooks. When both sets of active hooks are driven closed 24 active hooks engage 24 passive hooks which is 12 on the active HCS and 12 on the passive HCS. Read the IDSS Rev E document and view the relevant graphics to understand.


Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #83 on: 04/02/2020 07:34 pm »
Should Dragon 2's  for the private flights be androgynous?
Yes. The Docking system is a permanently installed on each Dragon 2.

I meant fully androgynous.

In other words: two SpaceX docking systems can NOT dock to each other, because they are not fully androgynous. The active hooks on one side would find NO passive hooks on the other side to latch onto.
Your docking logic is incorrect. Both sides each have a set 12 passive hooks and 12 active hooks. When both sets of active hooks are driven closed 24 active hooks engage 24 passive hooks which is 12 on the active HCS and 12 on the passive HCS. Read the IDSS Rev E document and view the relevant graphics to understand.

I'm going to believe woods170 logic on this.

Edit: As far as I know the private Dragon missions are not going to the ISS so the only option would be docking with another spacecraft.
They would still fly with it because the docking ring on Dragon 2 is the primary latching mechanism for the nose cone. It is not optional to remove because dragon is built around it. The tunnel hatch is also used for cargo loading into the deck storage lockers before the seats are placed in launch position.

Even if it did dock to some thing like a v2 version of Dragon Lab or Dagon XL only one vehicles Soft Capture System rings containing either/both a Mechanical or Magnetic Capture System would be extended in active mode. All Hard Capture System rings are always active as both sides have active hook latches to drive closed.

Offline baldusi

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #84 on: 04/02/2020 07:39 pm »
Should Dragon 2's  for the private flights be androgynous?
Yes. The Docking system is a permanently installed on each Dragon 2.

I meant fully androgynous.

In other words: two SpaceX docking systems can NOT dock to each other, because they are not fully androgynous. The active hooks on one side would find NO passive hooks on the other side to latch onto.
Your docking logic is incorrect. Both sides each have a set 12 passive hooks and 12 active hooks. When both sets of active hooks are driven closed 24 active hooks engage 24 passive hooks which is 12 on the active HCS and 12 on the passive HCS. Read the IDSS Rev E document and view the relevant graphics to understand.

Actually, the standard says it's optional to have both sets:

Quote
IDSS IDD Revision E
October 2016
3-23
3.2.3.4 HARD CAPTURE HOOKS

The HCS shall incorporate 12 pairs of active and passive hooks, located as shown in Figure 3.2.3-1. To carry nominal loads, 12 active hooks on one docking system shall engage 12 passive hooks on an opposing docking system interface. On a fully androgynous system, the 12 active hooks on each side of the interface may be engaged with the 12 passive hooks on the opposing interface for a total of 24 active hook engagements. Although engaging 24 hooks is not a requirement, this capability can be used to carry additional mated interface loads. The HCS implements a passively compliant passive hook. The hooks shall conform to the definition as shown in the HCS Hooks – Side Views [Figures 3.2.3.4-1, Ready to Dock Configuration, 3.2.3.4-2, Ready to Hook Configuration, and 3.2.3.4-3, Fully Mated Configuration], Figure 3.2.3.4-4, HCS Active Hook, and the HCS Passive Hook [Figures 3.2.3.4-5, Passive Hook, and 3.2.3.4-6, Passive Hook Detail View]. The motion of the active hook shall be bounded by the envelope shown in Figure 3.2.3.4-7, HCS Active Hook Motion Envelope.

Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #85 on: 04/02/2020 07:42 pm »
Your docking logic is incorrect. Both sides each have a set 12 passive hooks and 12 active hooks. When both sets of active hooks are driven closed 24 active hooks engage 24 passive hooks which is 12 on the active HCS and 12 on the passive HCS. Read the IDSS Rev E document and view the relevant graphics to understand.



Graphic showing the 12 active and 12 passive latches in the engaged position. IBDM is the ESA version of IDSS they will use on Gateway for their VV's.

Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #86 on: 04/02/2020 07:44 pm »
Should Dragon 2's  for the private flights be androgynous?
Yes. The Docking system is a permanently installed on each Dragon 2.

I meant fully androgynous.

In other words: two SpaceX docking systems can NOT dock to each other, because they are not fully androgynous. The active hooks on one side would find NO passive hooks on the other side to latch onto.
Your docking logic is incorrect. Both sides each have a set 12 passive hooks and 12 active hooks. When both sets of active hooks are driven closed 24 active hooks engage 24 passive hooks which is 12 on the active HCS and 12 on the passive HCS. Read the IDSS Rev E document and view the relevant graphics to understand.

Actually, the standard says it's optional to have both sets:

Quote
IDSS IDD Revision E
October 2016
3-23
3.2.3.4 HARD CAPTURE HOOKS

The HCS shall incorporate 12 pairs of active and passive hooks, located as shown in Figure 3.2.3-1. To carry nominal loads, 12 active hooks on one docking system shall engage 12 passive hooks on an opposing docking system interface. On a fully androgynous system, the 12 active hooks on each side of the interface may be engaged with the 12 passive hooks on the opposing interface for a total of 24 active hook engagements. Although engaging 24 hooks is not a requirement, this capability can be used to carry additional mated interface loads. The HCS implements a passively compliant passive hook. The hooks shall conform to the definition as shown in the HCS Hooks – Side Views [Figures 3.2.3.4-1, Ready to Dock Configuration, 3.2.3.4-2, Ready to Hook Configuration, and 3.2.3.4-3, Fully Mated Configuration], Figure 3.2.3.4-4, HCS Active Hook, and the HCS Passive Hook [Figures 3.2.3.4-5, Passive Hook, and 3.2.3.4-6, Passive Hook Detail View]. The motion of the active hook shall be bounded by the envelope shown in Figure 3.2.3.4-7, HCS Active Hook Motion Envelope.
That is correct however for permanently attached modules like on ISS both sets are used.

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #87 on: 04/02/2020 08:30 pm »
This is one of the best discussions we’ve had recently on NSF. Deep technical dive. 👍
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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #88 on: 04/02/2020 08:56 pm »
Hooks can be passive or active so 12 hooks in active mode on a Dragon 2 can hook to 12 hooks in passive mode on a Dragon 2 allowing docking.

Offline jarmumd

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #89 on: 04/02/2020 09:15 pm »
Hooks can be passive or active so 12 hooks in active mode on a Dragon 2 can hook to 12 hooks in passive mode on a Dragon 2 allowing docking.

Sorry, that's not correct.  A typical hook "assembly" has an active and a passive hook.  There are 12 assemblies, 24 hooks total.  As can be seen in the picture in my previous post, SpaceX only has active hooks, they don't have passive hooks, so they only have 12 hooks.  Nothing can "hook" to Dragon, since it doesn't have passive hooks.  Dragon can only hook to an IDA or other IDSS compliant docking system which has passive hooks, which Dragon doesn't have.

Offline russianhalo117

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #90 on: 04/02/2020 09:24 pm »
Hooks can be passive or active so 12 hooks in active mode on a Dragon 2 can hook to 12 hooks in passive mode on a Dragon 2 allowing docking.

Sorry, that's not correct.  A typical hook "assembly" has an active and a passive hook.  There are 12 assemblies, 24 hooks total.  As can be seen in the picture in my previous post, SpaceX only has active hooks, they don't have passive hooks, so they only have 12 hooks.  Nothing can "hook" to Dragon, since it doesn't have passive hooks.  Dragon can only hook to an IDA or other IDSS compliant docking system which has passive hooks, which Dragon doesn't have.
No both sides do. your picture shows the active hooks fully retracted. The passive hooks are permanently visible.

Offline jarmumd

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #91 on: 04/02/2020 09:36 pm »
Hooks can be passive or active so 12 hooks in active mode on a Dragon 2 can hook to 12 hooks in passive mode on a Dragon 2 allowing docking.

Sorry, that's not correct.  A typical hook "assembly" has an active and a passive hook.  There are 12 assemblies, 24 hooks total.  As can be seen in the picture in my previous post, SpaceX only has active hooks, they don't have passive hooks, so they only have 12 hooks.  Nothing can "hook" to Dragon, since it doesn't have passive hooks.  Dragon can only hook to an IDA or other IDSS compliant docking system which has passive hooks, which Dragon doesn't have.
No both sides do. your picture shows the active hooks fully retracted. The passive hooks are permanently visible.

I'm sorry, that's just not correct.  The active hooks move, but even fully rotated, they are still visible.  Also, they are near the center of the hook assembly.  See attached figure from IDSS revE.
« Last Edit: 04/02/2020 09:37 pm by jarmumd »

Offline mikelepage

A typical hook "assembly" has an active and a passive hook.  There are 12 assemblies, 24 hooks total.  As can be seen in the picture in my previous post, SpaceX only has active hooks, they don't have passive hooks, so they only have 12 hooks.  Nothing can "hook" to Dragon, since it doesn't have passive hooks.  Dragon can only hook to an IDA or other IDSS compliant docking system which has passive hooks, which Dragon doesn't have.
No both sides do. your picture shows the active hooks fully retracted. The passive hooks are permanently visible.

I'm sorry, that's just not correct.  The active hooks move, but even fully rotated, they are still visible.  Also, they are near the center of the hook assembly.  See attached figure from IDSS revE.

Note to russianhalo117, seems like you missed woods170 post (who apparently has inside info on SpaceX), which said the following earlier.  Also, I only see one set of hooks per assembly in the picture Jarmumd posted.

In other words: two SpaceX docking systems can NOT dock to each other, because they are not fully androgynous. The active hooks on one side would find NO passive hooks on the other side to latch onto.

If I understand russianhalo117 - you're also pointing out that the spec is only stating that the engagement of all hooks not being necessary, and is silent on whether they need to be present or not.  You appear to be assuming that they are present, per the spec, but contrary to what woods170 stated, and apparently confirmed by Jarmumd's image.

Quote
IDSS IDD Revision E
October 2016
3-23
3.2.3.4 HARD CAPTURE HOOKS
The HCS shall incorporate 12 pairs of active and passive hooks, located as shown in Figure 3.2.3-1. To carry nominal loads, 12 active hooks on one docking system shall engage 12 passive hooks on an opposing docking system interface. On a fully androgynous system, the 12 active hooks on each side of the interface may be engaged with the 12 passive hooks on the opposing interface for a total of 24 active hook engagements. Although engaging 24 hooks is not a requirement, this capability can be used to carry additional mated interface loads. The HCS implements a passively compliant passive hook. The hooks shall conform to the definition as shown in the HCS Hooks – Side Views [Figures 3.2.3.4-1, Ready to Dock Configuration, 3.2.3.4-2, Ready to Hook Configuration, and 3.2.3.4-3, Fully Mated Configuration], Figure 3.2.3.4-4, HCS Active Hook, and the HCS Passive Hook [Figures 3.2.3.4-5, Passive Hook, and 3.2.3.4-6, Passive Hook Detail View]. The motion of the active hook shall be bounded by the envelope shown in Figure 3.2.3.4-7, HCS Active Hook Motion Envelope.

Reattaching the diagram below - can I just make sure I understand this correctly.  If this diagram represents the docking ports of two modules, let's call them module A (above), and B (below).

From left to right, the hooks are:
1) Module B, passive hook.
2) Module A, active hook (would move right to left to latch).
3) Module B, active hook (would move left to right to latch).
4) not depicted is a passive hook for Module A. And the absence of this passive hook is what Woods170 is saying is the situation with Dragon 2.

If so, that brings me to my question - is it seriously that hard to add 12 passive hooks to all Dragon 2 / Dragon XL hatches to make them fully androgynous going forward?  I find it hard to believe that this would add much mass.  It may not be necessary for ISS missions but seems like an even more minor modification than I was expecting, and an important safety feature for any craft leaving LEO.  (EDIT or in LEO but not visiting ISS)
« Last Edit: 04/03/2020 07:23 am by mikelepage »

Offline woods170

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #93 on: 04/03/2020 07:34 am »
Should Dragon 2's  for the private flights be androgynous?
Yes. The Docking system is a permanently installed on each Dragon 2.

I meant fully androgynous.

In other words: two SpaceX docking systems can NOT dock to each other, because they are not fully androgynous. The active hooks on one side would find NO passive hooks on the other side to latch onto.
Your docking logic is incorrect. Both sides each have a set 12 passive hooks and 12 active hooks. When both sets of active hooks are driven closed 24 active hooks engage 24 passive hooks which is 12 on the active HCS and 12 on the passive HCS. Read the IDSS Rev E document and view the relevant graphics to understand.

First principle of IDSS Rev E to remember: the ACTIVE hooks on one side engage the PASSIVE hooks on the other side.

ACTIVE does NOT engage ACTIVE
PASSIVE does NOT engage PASSIVE


OK, having said that:
The docking system mounted on Crew Dragon is not fully IDSS Rev E compliant. It is missing the set of 12 passive hooks. It only has the set of 12 active hooks.

And that is fine. Because the IDAs (on the ISS side) have a fully IDSS Rev E compliant setup; they have both the set of 12 passive hooks as well as the set of 12 active hooks.

So, when Crew Dragon docks to the IDA, the 12 active hooks on Crew Dragon's side engage the 12 passive hooks on the IDA's side.
The 12 active hooks on the IDA's side do NOT engage, because they don't find their passive hook counterparts on Crew Dragon's side.

And that is all fine by the IDSS Rev E:

Quote from: IDSS_IDD_Revision_E
3.2.3.4 HARD CAPTURE HOOKS

The HCS shall incorporate 12 pairs of active and passive hooks, located as shown in Figure 3.2.3-1. To carry nominal loads, 12 active hooks on one docking system shall engage 12 passive hooks on an opposing docking system interface. On a fully androgynous system, the 12 active hooks on each side of the interface may be engaged with the 12 passive hooks on the opposing interface for a total of 24 active hook engagements. Although engaging 24 hooks is not a requirement, this capability can be used to carry additional mated interface loads.

But this also means that two Crew Dragons can NOT dock nose-to-nose. Both would only have the set of 12 active hooks and no passive hooks.
So, the set of 12 active hooks on one Crew Dragon would find NOTHING to latch onto on the side of the other Crew Dragon.

To make nose-to-nose docking of two Crew Dragons possible you need one of the following setups:
- One Crew Dragon has the active set while the other Crew Dragon has the passive set
OR
- Both Crew Dragons are fully androgynous (in other words: fully IDSS Rev E compliant) and have both the active and passive hook sets.


Additional note: @russianhalo117: I strongly advice you NOT to continue to argue with jarmumd about what hooks are or are not on Crew Dragon. Jarmumd actually works with NDSS-compliant docking systems. You don't. Continueing your discussion with Jarmumd will only serve to make you look silly.
« Last Edit: 04/03/2020 07:51 am by woods170 »

Offline woods170

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #94 on: 04/03/2020 07:55 am »
Quote
IDSS IDD Revision E
October 2016
3-23
3.2.3.4 HARD CAPTURE HOOKS
The HCS shall incorporate 12 pairs of active and passive hooks, located as shown in Figure 3.2.3-1. To carry nominal loads, 12 active hooks on one docking system shall engage 12 passive hooks on an opposing docking system interface. On a fully androgynous system, the 12 active hooks on each side of the interface may be engaged with the 12 passive hooks on the opposing interface for a total of 24 active hook engagements. Although engaging 24 hooks is not a requirement, this capability can be used to carry additional mated interface loads. The HCS implements a passively compliant passive hook. The hooks shall conform to the definition as shown in the HCS Hooks – Side Views [Figures 3.2.3.4-1, Ready to Dock Configuration, 3.2.3.4-2, Ready to Hook Configuration, and 3.2.3.4-3, Fully Mated Configuration], Figure 3.2.3.4-4, HCS Active Hook, and the HCS Passive Hook [Figures 3.2.3.4-5, Passive Hook, and 3.2.3.4-6, Passive Hook Detail View]. The motion of the active hook shall be bounded by the envelope shown in Figure 3.2.3.4-7, HCS Active Hook Motion Envelope.

Reattaching the diagram below - can I just make sure I understand this correctly.  If this diagram represents the docking ports of two modules, let's call them module A (above), and B (below).

From left to right, the hooks are:
1) Module B, passive hook.
2) Module A, active hook (would move right to left to latch).
3) Module B, active hook (would move left to right to latch).
4) not depicted is a passive hook for Module A. And the absence of this passive hook is what Woods170 is saying is the situation with Dragon 2.

Emphasis mine: Exactly! Spot on!

In this example Module A represents the Crew Dragon while Module B represents the IDA on ISS.
« Last Edit: 04/03/2020 08:04 am by woods170 »

Offline OnWithTheShow

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #95 on: 04/03/2020 01:28 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.

Offline woods170

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #96 on: 04/03/2020 02:11 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.

That use case isn't there. At least not for the currently envisioned usage of Crew Dragon. Which is transporting crew up to the ISS.

Had the use case been there, the docking system on Crew Dragon would be fully androgynous. But here's the thing. No matter how powerful F9 is, you don't throw mass into a docking system when that mass is not needed. In this case that unneeded mass consists of the passive hooks.

Is it difficult to make the docking system fully androgynous?

No, it isn't. No more difficult than making the active side of the system. It just takes some time and money. But it is not a major problem.
Having said that, for Crew Dragon the system being fully androgynous is also not needed. Which explains why it isn't.
« Last Edit: 04/03/2020 02:20 pm by woods170 »

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #97 on: 04/03/2020 02:32 pm »
The whole point of a standardized system is to allow reconfigurations not originally developed or even intended. Literally the reason Legos are Legos is they have a standard interface to one another (although not androgynous!) and can be easily reconfigured as the (play) mission changes.

Suppose a stretched-tank Dragon XL existed back when they were talking of shooting crewed Orion around the Moon before SLS was ready. If it had full androgynous capability, would’ve allowed launch around the Moon on the short schedule they had envisioned. Not every use can be foreseen, so a standard interface is hugely beneficial. Sure, from a tactical standpoint, “there’s no rationale in doing anything one bit better than the requirements dictate.” From a strategic point of view, there’s EVERY reason to have standardized interfaces.

However... If it’s not a big deal to add passive hooks to a new Dragon or Dragon XL, then the lack of them here isn’t a big deal.
« Last Edit: 04/03/2020 03:18 pm by Robotbeat »
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Offline Negan

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #98 on: 04/03/2020 03:27 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.

There could be a desire with the Space Adventures free flyer mission.

Offline jarmumd

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Re: Should SpaceX Vehicles Have Androgynous Docking Ports?
« Reply #99 on: 04/03/2020 03:39 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.
« Last Edit: 04/03/2020 03:41 pm by jarmumd »

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.
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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.

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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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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?

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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.

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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.
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