Author Topic: Should SpaceX Vehicles Have Androgynous Docking Ports?  (Read 10380 times)

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 »

Online 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.

Online Robotbeat

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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. 👍
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Negan

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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.

Online 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.

Online 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 »

Online Robotbeat

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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.

Online 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 »

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