NASA's Artemis Program Updates and Discussion Thread 5

[clongton]

As a trivial example, you apparently want Dragon to dock with Orion. This will require that one of the two docking adapters be modified to implement active/passive. They are both currently active-only.

Just an aside thought here but in my opinion, ALL spacecraft that have docking adapters should be mandated to ALWAYS be active/passive.
Make everything the same. Less expensive, more adaptable, potentially life-saving. This is a no brainer.

[DanClemmensen]

As a trivial example, you apparently want Dragon to dock with Orion. This will require that one of the two docking adapters be modified to implement active/passive. They are both currently active-only.

Just an aside thought here but in my opinion, ALL spacecraft that have docking adapters should be mandated to ALWAYS be active/passive.
Make everything the same. Less expensive, more adaptable, potentially life-saving. This is a no brainer.

Agreed, but they are not. Currently, a Crew Dragon cannot dock to another Crew Dragon. This is "justified" by the mass penalty and the fact that nobody has come up with a realistic scenario in which such a rescue would be useful. In the Starship era, both of these justifications go away.

Adding active HW to a passive-only dock is a big complicated expensive heavy deal. Adding passive HW to an active-only dock is supposed to be much simpler but does add mass.

[TheRadicalModerate]

The Orion cannot be inside a fairing if it launches with crew: its LAS and fairing are integrated. If launching without a crew the LAS is not needed and a small fairing can be used. I think the fairing-equivalent panels for SCA+ESM are separate units.

I wasn't suggesting that.  But all the aerodynamics and moments of inertia expect things to be no longer than the fairing--and shaped like a fairing.  There's obviously some wiggle room in here, but it seems like a VC is likely to have a bit more wiggle room.

[Negan]

As a trivial example, you apparently want Dragon to dock with Orion. This will require that one of the two docking adapters be modified to implement active/passive. They are both currently active-only.

No. A Dragon 2 would need to replace its current docking hardware (already in development) with HLS's.

Edit: Actually, from the articles below it seems Orion's system is passive.

https://www.space.com/spacex-starship-docking-system-tests-nasa-moon-missions

https://www.nasa.gov/image-article/nasa-spacex-test-starship-lunar-lander-docking-system/

"This dynamic testing demonstrated that the Starship system could perform a “soft capture” while in the active docking role. When two spacecraft dock, one vehicle assumes an active “chaser” role while the other is in a passive “target” role. To perform a soft capture, the soft capture system (SCS) of the active docking system is extended while the passive system on the other spacecraft remains retracted. Latches and other mechanisms on the active docking system SCS attach to the passive system, allowing the two spacecraft to dock."

[DanClemmensen]

As a trivial example, you apparently want Dragon to dock with Orion. This will require that one of the two docking adapters be modified to implement active/passive. They are both currently active-only.

No. A Dragon 2 would need to replace its current docking hardware (already in development) with HLS's.

Dragon is one of the two spacecraft: the other is Orion. Both spacecraft currently implement active-only IDSS.
Please look at
    https://en.wikipedia.org/wiki/International_Docking_System_Standard
You advocate changing the Dragon's active-only IDSS port by "replacing" it. Sure, but it's much simpler to just add the IDSS passive-mode hardware to the existing active-only port to upgrade it to be an active/passive IDSS port. HLS is presumed to have an active/passive IDSS port because it's the easiest way to meet the requirement to dock to Orion and also to Gatweay. Basically, this may be only a semantic difference, since SpaceX is probably adapting the Crew Dragon IDSS port to create the one for HLS anyway.

I note that you want to change the Dragon, not the Orion, even though there is a fleet of four operational Dragons that regularly visit the ISS and need their installed active IDSS capability, while none of the Orions have ever had a docking port installed. While I think the entire idea is ludicrous, if this were to be implemented in a rational world with equal partners and equivalent contracts, Orion should adapt, not Dragon. In the real world I agree with you, but only because SpaceX can add the passive hardware quickly and inexpensively, while a cost-plus modification to Orion's port will take a long time and cost a lot of money.

We also know that Dragon can fly with any of three types of port hardware already: active-only IDSS, Cupola, and SpaceWalker, so presumably SpaceX could choose to create a passive-only IDSS that can be swapped in. But why?

[TheRadicalModerate]

"Latches and other mechanisms on the active docking system SCS attach to the passive system, allowing the two spacecraft to dock."

Soft capture isn't really the problem.  The problem is hard dock, where certain latches and hooks are eliminated from the active side, and only implemented on the passive side.

There are no active/passive systems in use today.  However, the IDSS spec anticipated active/passive use, and it describes how to add the proper latches and hooks to do it, and also how the SCS on the passive side is stowed to keep it out of the way.  The main problem with active/passive is that it's heavy.  That's a big deal for ordinary spacecraft, but it's close to a rounding error on Starship.

My biggest concern with Starship-to-Starship docking is that the bending moments on two ships that long and heavy are huge.  IDSS has various use cases outlined, some of which involve high-thrust, high-lateral-vibration cases. These also haven't ever been deployed, but have been anticipated.  Still, I'm not sure that even the high-thrust cases are conservative enough to deal with two at-least-half-fueled Starships.

[JohnFornaro]

You can get to EML-1 several days before you can get to LLO or NRHO.  IMO, travel time is an important part of the equation...

It takes longer to get from LEO to LLO thru EML-1, than to go directly to LLO, Apollo style. Both scenarios below use chemical propulsion and Hohmann transfer trajectories.

No doubt, but I'm suggesting a different architecture, if that's the right word.  I envision a reusable vehicle from Earth to EML-1 and back, and a second reusable vehicle from EML-1 to the lunar surface and back.  In my mind there would be a third reusable vehicle for the Mars leg, but this would depend upon the tradwe between EML-1 to Mars surface and back, and EML-1 to a martian transfer station, thought by me to also be a ring station.

Direct Distance: LEO to LLO: ...

From LEO to EML-1, then from EML-1 to LLO: ...

From LEO to LLO: ...

The difference is that there is no “direct route” to either destination from LEO . Both scenarios follow separate Hohmann transfer orbits. Therefore it takes longer to go thru EML-1. It is a similar timeframe for NHRO as it is for EML-1. The fastest route to LLO is straight thru from LEO.

Thanks for the straight up explanation in plain English.  I sit corrected!

Keep in mind that in my conception, the EML-1 rign station is dual use, as a way station for both lunar and martian missions.  And don't forget Venus!

The terrestrial analogy would be how we use airports as hubs, not necessarily the shortest distance between two cities.

[JohnFornaro]

Just an aside thought here but in my opinion, ALL spacecraft that have docking adapters should be mandated to ALWAYS be active/passive.
Make everything the same. Less expensive, more adaptable, potentially life-saving. This is a no brainer.

I've been saying this for years. I would require the Russians, Chinese, and whoever else, follow the same adaptor specifications.  The thinking is that space is for all mankind:

Outer space will be used solely for the benefit of all mankind.

Addressing the UN on 09-02-58.  From: Christol, "The Modern International Law of Outer Space", p.251

[Negan]

My biggest concern with Starship-to-Starship docking is that the bending moments on two ships that long and heavy are huge.

I don't understand this concern. Two Starships are set to dock together next year.

[dglow]

My biggest concern with Starship-to-Starship docking is that the bending moments on two ships that long and heavy are huge.

I don't understand this concern. Two Starships are set to dock together next year.

For the purpose of transferring propellant, not forming a pressurized tunnel through which humans and cargo can pass.

[Negan]

My biggest concern with Starship-to-Starship docking is that the bending moments on two ships that long and heavy are huge.

I don't understand this concern. Two Starships are set to dock together next year.

For the purpose of transferring propellant, not forming a pressurized tunnel through which humans and cargo can pass.

Of course, but when used in addition to IDSS, would the "bending moments" be a concern?

[Negan]

In the real world I agree with you, but only because SpaceX can add the passive hardware quickly and inexpensively, while a cost-plus modification to Orion's port will take a long time and cost a lot of money.

Why does the modification have to be cost-plus?

[DanClemmensen]

In the real world I agree with you, but only because SpaceX can add the passive hardware quickly and inexpensively, while a cost-plus modification to Orion's port will take a long time and cost a lot of money.

Why does the modification have to be cost-plus?

Orion is owned  by NASA, not the contractor. All Orion contracts thus far are cost-plus. There might be some mechanism to do an Orion modification some other way, but the usual way would be a new task order against the existing cost-plus contract.

[DanClemmensen]

My biggest concern with Starship-to-Starship docking is that the bending moments on two ships that long and heavy are huge.

I don't understand this concern. Two Starships are set to dock together next year.

For the purpose of transferring propellant, not forming a pressurized tunnel through which humans and cargo can pass.

Of course, but when used in addition to IDSS, would the "bending moments" would be a concern?

So far, the renders, etc, have shown the IDSS port in the nose, so nose-to-nose docking. The fuel transfer has been depicted as back-to-back, using an unspecified docking and transfer mechanism.

Bending moments would appear to be a bigger concern for the IDSS port, which may require some additional type of bracing. I would be more concerned abut docking HLS to Gateway, which is an actual contractual requirement and which may be a bigger problem because the Gateway design is not under SpaceX control. Starship HLS buddy docking has both Ships designed by SpaceX, so additional bracing can be added.

You can determine the moments that IDSS must handle by reading the IDSS spec. There are several categories of increasing robustness. I tried to understand those numbers but failed. I cannot figure out whether Starship HLS would end up ripping the Gateway port out. Gateway was orignially envisioned to dock with a much lighter HLS, more like the Apollo LM.

[Coastal Ron]

My biggest concern with Starship-to-Starship docking is that the bending moments on two ships that long and heavy are huge.

I don't understand this concern. Two Starships are set to dock together next year.

For the purpose of transferring propellant, not forming a pressurized tunnel through which humans and cargo can pass.

Of course, but when used in addition to IDSS, would the "bending moments" would be a concern?

So far, the renders, etc, have shown the IDSS port in the nose, so nose-to-nose docking. The fuel transfer has been depicted as back-to-back, using an unspecified docking and transfer mechanism.

Bending moments would appear to be a bigger concern for the IDSS port, which may require some additional type of bracing.

For the Starship HLS and any other much smaller crew vehicle, if they are docked while in space there shouldn't be any "wiggle" issues. The smaller crew vehicle won't have a resonate frequency for vibration (i.e. "wiggle"), and I can't think of any forces that would create such vibration.

I would be more concerned abut docking HLS to Gateway, which is an actual contractual requirement and which may be a bigger problem because the Gateway design is not under SpaceX control.

Yes, this would be of concern, as would docking a Starship at the ISS. We've had lots of discussion on the rotating space station threads about how to dock large ships with large stations (essentially two large masses, with one that moves), and at least on those threads we never came up with an elegant solution that didn't require lots of extra mass specifically for docking purposes.

You can determine the moments that IDSS must handle by reading the IDSS spec. There are several categories of increasing robustness. I tried to understand those numbers but failed. I cannot figure out whether Starship HLS would end up ripping the Gateway port out. Gateway was orignially envisioned to dock with a much lighter HLS, more like the Apollo LM.

Maybe add two extra Canadarm3 units that would be built specifically for bracing a visiting Starship HLS against the Gateway?

[DanClemmensen]

You can determine the moments that IDSS must handle by reading the IDSS spec. There are several categories of increasing robustness. I tried to understand those numbers but failed. I cannot figure out whether Starship HLS would end up ripping the Gateway port out. Gateway was orignially envisioned to dock with a much lighter HLS, more like the Apollo LM.

Maybe add two extra Canadarm3 units that would be built specifically for bracing a visiting Starship HLS against the Gateway?

That's a simple and flexible solution. It does require an extension to the Gateway docking spec and perhaps that extension can be generalized to become a formalized extension to IDSS. One party has arms, and the other party needs well-specified robust grab points for those arms. Basically we are almost back to berthing instead of docking. This could all be tested on ISS, except that ISS is nearing EOL.

In the case of HLS-to-HLS, One of the two (or both) will need to carry arms and will need to be able to deploy them after launch. Probably no big deal: carry it in the garage and let them deploy themselves.

[Negan]

In the case of HLS-to-HLS, One of the two (or both) will need to carry arms and will need to be able to deploy them after launch. Probably no big deal: carry it in the garage and let them deploy themselves.

This solution means only a 4-person crew would be able to transfer to HLS unless you involved multiple spacecraft. Adding a side crew transfer solution would allow a crew Starship to transfer far more. It would also allow Starship to transfer cargo to HLS.

Edit: It would also be needed for your Mars ferries suggestion.

[DanClemmensen]

In the case of HLS-to-HLS, One of the two (or both) will need to carry arms and will need to be able to deploy them after launch. Probably no big deal: carry it in the garage and let them deploy themselves.

This solution means only a 4-person crew would be able to transfer to HLS unless you involved multiple spacecraft. Adding a side crew transfer solution would allow a crew Starship to transfer far more. It would also allow Starship to transfer cargo to HLS.

Edit: It would also be needed for your Mars ferries suggestion.

I was thinking only about the short term Artemis III problem. HLS-class Ships can easily accommodate much larger crew and that dinky little IDSS tunnel is still about as wide as the doors in your house. Nose-to-nose is the model for using another HLS as an OTV to replace SLS/Orion in 2026.

If you are thinking about a tourist EDL version of a Starship docking with the CLD version, then sure, speculate about something more tourist-friendly. But this is not the correct thread for that.

[Negan]

I was thinking only about the short term Artemis III problem.

So you're lucking insisting on your short term solution that will eventually become obsolete. The title of the thread really doesn't indicate that. My mistake. 

[DanClemmensen]

I was thinking only about the short term Artemis III problem.

So you're lucking for a short term solution that will eventually become obsolete. The title of the thread really doesn't indicate that. My mistake. 

Actually, the entire Artemis POR calls for using Orion for all crew voyages at four crew per mission. Other uses of Starship would be changes to Artemis and belong in an alternative thread such as
    https://forum.nasaspaceflight.com/index.php?topic=62009.msg2648338#msg2648338
or the SLS/Orion replacement thread
https://forum.nasaspaceflight.com/index.php?topic=59662.0