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!
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?
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: 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.
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?
Imagine how dumb you’d look if you had one of these scenarios happen where the crew could’ve been rescued but they can’t. “I thought you said the port was androgynous?”“Well, see the thing is...”
Quote 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.
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?
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.
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: 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.
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.
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.