1) Anyone care to speculate/confirm whether a Dragon 2 can dock to a Dragon XL?
Quote from: pochimax on 03/30/2020 08:56 pmQuote from: woods170 on 03/30/2020 02:06 pmQuote from: pochimax on 03/30/2020 12:52 pmIf 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.pdf5.0 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_SOW5.0 MISSION UNIQUE CAPABILITIES (SUBCLIN 103)The contractor shall provide Mission Unique Capabilities for requirements over and abovelogistic service requirements obtained under subCLINs 101 and 102.These capabilities may be added throughout the life of the contract or they may be incorporated inresponse 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.
Quote from: woods170 on 03/30/2020 02:06 pmQuote from: pochimax on 03/30/2020 12:52 pmIf 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.pdf5.0 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.
Quote from: pochimax on 03/30/2020 12:52 pmIf 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.
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.
5.0 MISSION UNIQUE CAPABILITIES (SUBCLIN 103)The contractor shall provide Mission Unique Capabilities for requirements over and abovelogistic service requirements obtained under subCLINs 101 and 102.These capabilities may be added throughout the life of the contract or they may be incorporated inresponse to specific task order requirements.
<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)?....
Quote from: Robotbeat on 03/28/2020 05:08 pmQuote from: jarmumd on 03/28/2020 01:46 pmQuote from: dgmckenzie on 03/28/2020 11:37 amIf 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.
Quote from: jarmumd on 03/28/2020 01:46 pmQuote from: dgmckenzie on 03/28/2020 11:37 amIf 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.
Quote from: dgmckenzie on 03/28/2020 11:37 amIf 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)....
If it is supposed to transfer both pressurized and unpressurized cargo, how could it have docking at both ends?
Quote from: mikelepage on 03/31/2020 06:51 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) queryQuote from: jarmumd on 03/28/2020 05:24 pmQuote from: Robotbeat on 03/28/2020 05:08 pmQuote from: jarmumd on 03/28/2020 01:46 pmQuote from: dgmckenzie on 03/28/2020 11:37 amIf 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.
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.
QuoteAlso, 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>
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?
Quote from: rakaydos on 03/31/2020 11:39 amHow 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.
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.
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.
Even if an option is "overpriced" for what is being done...
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.
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.
Quote from: Robotbeat on 03/31/2020 05:30 pmIt'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.
Quote from: Robotbeat on 03/31/2020 05:30 pmIt'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.
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.
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.
Quote from: whitelancer64 on 03/31/2020 06:39 pmIt'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.
There just isn't the fuel for a capsule to go and rescue them, starting at the ISS.
I just don't think there is such a thing as a capsule going to rescue another capsule.
Quote from: jarmumd on 03/31/2020 05:53 pmQuote from: Robotbeat on 03/31/2020 05:30 pmIt'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.
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...”
QuoteI 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.
Quote from: Robotbeat on 03/31/2020 07:17 pmImagine 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 from: whitelancer64 on 03/31/2020 08:02 pmQuoteI 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?
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.
Quote from: Robotbeat on 03/31/2020 08:22 pmThis 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?
Quote from: Robotbeat on 03/31/2020 07:17 pmImagine 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.
Quote from: DigitalMan on 03/31/2020 09:30 pmQuote from: Robotbeat on 03/31/2020 07:17 pmImagine 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.
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.
Quote from: Robotbeat on 03/31/2020 09:29 pmReally, 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.
Quote from: jarmumd on 03/31/2020 10:05 pmQuote from: Robotbeat on 03/31/2020 09:29 pmReally, 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.
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)....How badly have I misunderstood this?
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.
Quote from: Robotbeat on 04/01/2020 12:15 amA 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?
Quote from: jarmumd on 04/01/2020 12:26 amQuote from: Robotbeat on 04/01/2020 12:15 amA 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.
Quote from: Robotbeat on 04/01/2020 12:28 amQuote from: jarmumd on 04/01/2020 12:26 amQuote from: Robotbeat on 04/01/2020 12:15 amA 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 attachedbending 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, lolreducing 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.
Quote from: TheRadicalModerate on 03/31/2020 11:12 pmI'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.QuoteI 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.QuoteIDSS 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.QuoteThere 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)QuoteSo 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?Quote2) 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!
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?
Quote from: kkattula on 04/01/2020 04:14 amSo 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.
Quote from: jarmumd on 03/31/2020 04:10 pmQuote from: rakaydos on 03/31/2020 11:39 amHow 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.
Quote from: jarmumd on 03/31/2020 09:01 pmQuote from: Robotbeat on 03/31/2020 08:22 pmThis 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.
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.
Quote from: Robotbeat on 03/31/2020 08:37 pmIt’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.
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.Quote from: woods170 on 04/01/2020 07:57 amQuote from: Robotbeat on 03/31/2020 08:37 pmIt’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.
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 It looks like that's not happening, so I guess SpaceX is planning on going to resupply the Gateway instead.
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.
Quote from: Robotbeat on 03/31/2020 07:17 pmImagine 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.
Quote from: woods170 on 04/01/2020 07:40 amQuote from: Robotbeat on 03/31/2020 07:17 pmImagine 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.
Quote from: Khadgars on 03/31/2020 06:46 pmQuote from: jarmumd on 03/31/2020 05:53 pmQuote from: Robotbeat on 03/31/2020 05:30 pmIt'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.
Quote from: Robotbeat on 04/01/2020 10:35 amQuote from: woods170 on 04/01/2020 07:40 amQuote from: Robotbeat on 03/31/2020 07:17 pmImagine 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.
Quote from: soltasto on 04/01/2020 10:38 amQuote from: Robotbeat on 04/01/2020 10:35 amQuote from: woods170 on 04/01/2020 07:40 amQuote from: Robotbeat on 03/31/2020 07:17 pmImagine 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.
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.
Is the D2 docking port not an NDSB1 implementation?
Quote from: russianhalo117 on 04/01/2020 06:03 amQuote from: kkattula on 04/01/2020 04:14 amSo 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.
Quote from: russianhalo117 on 04/01/2020 07:02 pmBoth 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?
I know NDS B1 has fixed petals. But does anything on the IDSS Rev E standard precludes the use of removable petals?
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.
Should Dragon 2's for the private flights be androgynous?
Quote from: baldusi on 04/02/2020 06:39 amThe 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.
Quote from: Robotbeat on 04/02/2020 02:38 pmQuote from: baldusi on 04/02/2020 06:39 amThe 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.
Quote from: Negan on 04/02/2020 03:33 pmShould Dragon 2's for the private flights be androgynous?Yes. The Docking system is a permanently installed on each Dragon 2.
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.
Quote from: TheRadicalModerate on 04/01/2020 06:22 amWho 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.
Quote from: russianhalo117 on 04/02/2020 03:36 pmQuote from: Negan on 04/02/2020 03:33 pmShould 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.Quote from: woods170 on 03/31/2020 01:29 pmIn 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.
Quote from: Negan on 04/02/2020 04:20 pmQuote from: russianhalo117 on 04/02/2020 03:36 pmQuote from: Negan on 04/02/2020 03:33 pmShould 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.Quote from: woods170 on 03/31/2020 01:29 pmIn 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.
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.
Quote from: russianhalo117 on 04/02/2020 07:02 pmQuote from: Negan on 04/02/2020 04:20 pmQuote from: russianhalo117 on 04/02/2020 03:36 pmQuote from: Negan on 04/02/2020 03:33 pmShould 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.Quote from: woods170 on 03/31/2020 01:29 pmIn 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.
IDSS IDD Revision EOctober 20163-233.2.3.4 HARD CAPTURE HOOKSThe 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.
Quote from: russianhalo117 on 04/02/2020 07:02 pmYour 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.
Quote from: russianhalo117 on 04/02/2020 07:02 pmQuote from: Negan on 04/02/2020 04:20 pmQuote from: russianhalo117 on 04/02/2020 03:36 pmQuote from: Negan on 04/02/2020 03:33 pmShould 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.Quote from: woods170 on 03/31/2020 01:29 pmIn 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:QuoteIDSS IDD Revision EOctober 20163-233.2.3.4 HARD CAPTURE HOOKSThe 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.
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.
Quote from: Negan on 04/02/2020 08:56 pmHooks 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.
Quote from: jarmumd on 04/02/2020 09:15 pmQuote from: Negan on 04/02/2020 08:56 pmHooks 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.
Quote from: russianhalo117 on 04/02/2020 09:24 pmQuote from: jarmumd on 04/02/2020 09:15 pmA 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.
Quote from: jarmumd on 04/02/2020 09:15 pmA 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.
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.
3.2.3.4 HARD CAPTURE HOOKSThe 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.
QuoteIDSS IDD Revision EOctober 20163-233.2.3.4 HARD CAPTURE HOOKSThe 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.
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.
Quote from: OnWithTheShow on 04/03/2020 01:28 pmThere 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.
Quote from: russianhalo117 on 04/03/2020 04:07 pmBoth 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]
Quote from: jarmumd on 04/03/2020 04:21 pmQuote from: russianhalo117 on 04/03/2020 04:07 pmBoth 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]
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.
Quote from: Robotbeat on 04/03/2020 04:29 pmThe 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.
-Would have to ditch the nosecone
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.
Quote from: jarmumd on 04/03/2020 03:39 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?
It was discussed in another thread on the run up to DM1. I don't remember what was said.
Quote from: russianhalo117 on 04/03/2020 05:55 pmIt was discussed in another thread on the run up to DM1. I don't remember what was said.Quote from: Nehkara on 01/17/2020 08:57 pmThis 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.
-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.
-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.
Quote from: jarmumd on 04/03/2020 03:39 pm-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.