Alternative Capabilities to send Cargo to ISS while Baikonur Site 31/6 is down

[Jim]

Still have the roll control problem.

[woods170]

Still have the roll control problem.

You refer to desaturation of the CMGs, which is usually done by firing the thrusters on Progress?

[DaveS]

Still have the roll control problem.

You refer to desaturation of the CMGs, which is usually done by firing the thrusters on Progress?

No, roll control of the station itself. The CMGs can only provide pitch and yaw control not roll control hence the need of the roll control thrusters on the MLM.

[Brigantine]

Why?

I heard progress was launcher-agnostic, so was thinking about it as 'just a payload'. JiuQuan is the home of the Soyuz-derived Shenzhou capsule, so I wrongly presumed it would be fine.

My point in picking the knock-off-F9 over CZ-2F was just that American launchers are not the 1st place Russia would go looking for a commercial launch, so F9 seems unlikely. It seems we can now narrow it down to launchers present at Baikonur

[Yellowstone10]

No, roll control of the station itself. The CMGs can only provide pitch and yaw control not roll control hence the need of the roll control thrusters on the MLM.

Is there a reference for that, by any chance? I had assumed CMGs give you 3-axis control (until they're saturated, of course), and my Google-fu is not turning up anything about roll control being different from pitch/yaw.

[Jim]

No, roll control of the station itself. The CMGs can only provide pitch and yaw control not roll control hence the need of the roll control thrusters on the MLM.

Is there a reference for that, by any chance? I had assumed CMGs give you 3-axis control (until they're saturated, of course), and my Google-fu is not turning up anything about roll control being different from pitch/yaw.

Desaturation is required on all axis.  Due to the length of the truss and the short lever arms of thrusters on the SM or Progress docked axially to the SM, it takes a lot of propellant to desaturate roll.  Progress and other modules with thrusters that are docked orthogonally to the SM can provide more effective roll desaturation.

[DanClemmensen]

No, roll control of the station itself. The CMGs can only provide pitch and yaw control not roll control hence the need of the roll control thrusters on the MLM.

Is there a reference for that, by any chance? I had assumed CMGs give you 3-axis control (until they're saturated, of course), and my Google-fu is not turning up anything about roll control being different from pitch/yaw.

Desaturation is required on all axis.  Due to the length of the truss and the short lever arms of thrusters on the SM or Progress docked axially to the SM, it takes a lot of propellant to desaturate roll.  Progress and other modules with thrusters that are docked orthogonally to the SM can provide more effective roll desaturation.

From a pure physics standpoint, you would have tiny little thrusters at the extreme ends of the truss for roll control? Another set out there would work well for yaw, but handling yaw while doing boost works well so yaw control from the truss is not needed.

[Jim]

From a pure physics standpoint, you would have tiny little thrusters at the extreme ends of the truss for roll control? Another set out there would work well for yaw, but handling yaw while doing boost works well so yaw control from the truss is not needed.

And who is going to design, build and qualify them?

[DanClemmensen]

From a pure physics standpoint, you would have tiny little thrusters at the extreme ends of the truss for roll control? Another set out there would work well for yaw, but handling yaw while doing boost works well so yaw control from the truss is not needed.

And who is going to design, build and qualify them?

Yep, that's why I said "from a pure physics standpoint". It's almost certainly not practical to add them at this point. I only posted this to see if I understood the physics correctly. It's easy to say that they could just strap a Starlink Ion thruster and a COPV full of Argon onto the truss ends . It's a heck of a lot harder to actually do the design/build/qualify/install, not to mention the massive contract, program, and project management.

[Comga]

No, roll control of the station itself. The CMGs can only provide pitch and yaw control not roll control hence the need of the roll control thrusters on the MLM.

Is there a reference for that, by any chance? I had assumed CMGs give you 3-axis control (until they're saturated, of course), and my Google-fu is not turning up anything about roll control being different from pitch/yaw.

Desaturation is required on all axis.  Due to the length of the truss and the short lever arms of thrusters on the SM or Progress docked axially to the SM, it takes a lot of propellant to desaturate roll.  Progress and other modules with thrusters that are docked orthogonally to the SM can provide more effective roll desaturation.

Jim!
That’s an excellent and clear explanation.

Of course, Crew Dragons are sometimes docked radially, and not having used their LES, have “a lot of propellant”.  Are they plumbed to also feed it to the ACS Dracos?

PS: Dan, “from a pure physics standpoint” such hardware does not exist.

[Nicolas PILLET]

A Dragon variant will deorbit the ISS when the time comes.

The Dragon-derived vehicle will give about one half of the dV needed to deorbit the ISS. The other half should be given by Russian Segment (Progress engines and Zvezda engines burning Progress-delivered propellant).

[Nicolas PILLET]

From a pure physics standpoint, you would have tiny little thrusters at the extreme ends of the truss for roll control? Another set out there would work well for yaw, but handling yaw while doing boost works well so yaw control from the truss is not needed.

And who is going to design, build and qualify them?

This is, of course, a dream. But since 2021 there are small roll control engines at the end of Nauka, using its length to increase moment.

[Jim]

Yep, that's why I said "from a pure physics standpoint". It's almost certainly not practical to add them at this point. I only posted this to see if I understood the physics correctly. It's easy to say that they could just strap a Starlink Ion thruster and a COPV full of Argon onto the truss ends

Need more thrust than that

[Jim]

Of course, Crew Dragons are sometimes docked radially, and not having used their LES, have “a lot of propellant”.  Are they plumbed to also feed it to the ACS Dracos?

Their thruster alignments are not proper for that role

[DanClemmensen]

Yep, that's why I said "from a pure physics standpoint". It's almost certainly not practical to add them at this point. I only posted this to see if I understood the physics correctly. It's easy to say that they could just strap a Starlink Ion thruster and a COPV full of Argon onto the truss ends

Need more thrust than that

Sure. If NASA decided to add roll control thrusters, they would would use real engineers to do a real study and design a real system, and I agree with your point that this is not cost-effective given the remaining lifetime of ISS.

[robertross]

Here's a question: Is there any way to refuel the current Progress on orbit via external methods?
I doubt Dextre can reach with Canadarm 2, but perhaps there are alternative methods that can be considered?

[Comga]

A Dragon variant will deorbit the ISS when the time comes.

The Dragon-derived vehicle will give about one half of the dV needed to deorbit the ISS. The other half should be given by Russian Segment (Progress engines and Zvezda engines burning Progress-delivered propellant).

“should”
If needed, the ISS can drift down.
But the point was what Dragon could do in the absence of Progress launches.

Of course, Crew Dragons are sometimes docked radially, and not having used their LES, have “a lot of propellant”.  Are they plumbed to also feed it to the ACS Dracos?

Their thruster alignments are not proper for that role

“proper”?
Ah
Not properly aligned
That’s visible in images of Dragon docked to the zenith port. 
But the question was if the plumbing accommodates sub-optimal roll torque thrust
Even with the lousy lever arm for Dragon on the axial Node 2 Forward, it’s a lot of propellant.

But again, you and Nicolas and others have poked at nits in front of the big main issue.
(You should refrain, you Nattering Nabobs of Negativity.)

While there is a hiatus in Progress and Soyuz launches, be it 4 months, a year, or the remaining life of the ISS, NASA and its “western” partners can maintain the ISS themselves, using what they have, which is mostly from SpaceX.

No NASA logoed Progress on Chinese launchers 
No Rube Goldberg
No Lego Rockets
No fantasy hardware needed

[russianhalo117]

Here's a question: Is there any way to refuel the current Progress on orbit via external methods?
I doubt Dextre can reach with Canadarm 2, but perhaps there are alternative methods that can be considered?

I don't know if their tanks and their pressure fed backfill system allows that but the rest of the ships plumbing allows Soyuz and Progress to receive propellant system transfer from the entire RS and its VV's.

[AmigaClone]

While there is a hiatus in Progress and Soyuz launches, be it 4 months, a year, or the remaining life of the ISS, NASA and its “western” partners can maintain the ISS themselves, using what they have, which is mostly from SpaceX.

No NASA logoed Progress on Chinese launchers 
No Rube Goldberg
No Lego Rockets
No fantasy hardware needed

Using purely existing or equipment in development before 1 November 2025 the long-term crew for the ISS would be reduced to 4 when the newest Soyuz has to return.

Avoiding that situation was the primary reason I suggested perhaps investigating what it would take to modify a Dragon to dock on the Russian side.

Using certain docking ports on the Russian side would also make the idea of trying to use a Dragon to control the roll slightly less difficult.

[DanClemmensen]

While there is a hiatus in Progress and Soyuz launches, be it 4 months, a year, or the remaining life of the ISS, NASA and its “western” partners can maintain the ISS themselves, using what they have, which is mostly from SpaceX.

No NASA logoed Progress on Chinese launchers 
No Rube Goldberg
No Lego Rockets
No fantasy hardware needed

Using purely existing or equipment in development before 1 November 2025 the long-term crew for the ISS would be reduced to 4 when the newest Soyuz has to return.

Avoiding that situation was the primary reason I suggested perhaps investigating what it would take to modify a Dragon to dock on the Russian side.

Using certain docking ports on the Russian side would also make the idea of trying to use a Dragon to control the roll slightly less difficult.

Are the Russian ports APAS-95?  If so, NASA has an existing design for the IDA, which can be attached to an APAS-95 port to turn it into an IDS port. The two US IDSS docks use IDAs. There are a number of major issues to resolve to actually use this approach, so it is probably infeasible.