SpaceX and Replacement of Russian module services on the ISS

[Ludus]

https://twitter.com/elonmusk/status/1497370602075734021?s=20&t=Sk3wMCFhHZv_Z7wvBrROxQ

There was an interesting interaction between Elon Musk and Rogozin on Twitter.

After President Joe Biden announced new sanctions Thursday that "will degrade their (Russia's) aerospace industry, including their space program," Roscosmos Director General Dmitry Rogozin said on Twitter that the station's orbit and location in space are controlled by Russian engines.
"If you block cooperation with us, who will save the International Space Station (ISS) from an uncontrolled deorbit and fall into the United States or...Europe?" Rogozin said. "There is also the possibility of a 500-ton structure falling on India and China. Do you want to threaten them with such a prospect? The ISS does not fly over Russia, therefore all the risks are yours. Are you ready for them?"

Elon Musk tweeted the SpaceX logo in response.

There are obvious issues after the Russian invasion of Ukraine with continued cooperation with Russia on the ISS and possible alternatives.

[2megs]

Here's a hardware-centric thread that about how this could work. The idea is to remove the Russian segment, attach an additional IDA to PMA-1 in its place, and semi-permanently dock a Dragon (or Cygnus upgraded to dock instead of berth) there to provide reboosts.

I'd say "sounds crazy", except Chris Bergin and Elon Musk were both giving this thread their thumbs-up on Twitter, so it's worth discussing at least.

(Let's all please direct any talk of Why and Whether to the Space Policy section, and keep this focused on the How.)

https://twitter.com/Space_Pete/status/1497029449455312901

[pier_re]

https://twitter.com/elonmusk/status/1497370602075734021?s=20&t=Sk3wMCFhHZv_Z7wvBrROxQ

There was an interesting interaction between Elon Musk and Rogozin on Twitter.

There are obvious issues after the Russian invasion of Ukraine with continued cooperation with Russia on the ISS and possible alternatives.

Ok. I've been reading stuff on this forum for month. But I registered just to react to this. Has Elon Musk really trolled this guy by suggesting that SpaceX would take on the challenge if needed?!?!
I find hilarious and mind blowing, but not being an English native speaker, I'm afraid I'm reading it wrong 😅

[kevinof]

Here's a hardware-centric thread that about how this could work. The idea is to remove the Russian segment, attach an additional IDA to PMA-1 in its place, and semi-permanently dock a Dragon (or Cygnus upgraded to dock instead of berth) there to provide reboosts.

I'd say "sounds crazy", except Chris Bergin and Elon Musk were both giving this thread their thumbs-up on Twitter, so it's worth discussing at least.

(Let's all please direct any talk of Why and Whether to the Space Policy section, and keep this focused on the How.)

https://twitter.com/Space_Pete/status/1497029449455312901

Do SpaceX still have some Dragon 1s available in storage? Would that do the job?

[Chris Bergin]

Rogozin has been trolling Elon for years and Elon's reaction is based on viable (potential) fact.

[Jim]

Cygnus or MEV type would make a better system.

[webdan]

There was an interesting interaction between Elon Musk and Rogozin on Twitter.

There are obvious issues after the Russian invasion of Ukraine with continued cooperation with Russia on the ISS and possible alternatives.

Ok. I've been reading stuff on this forum for month. But I registered just to react to this. Has Elon Musk really trolled this guy by suggesting that SpaceX would take on the challenge if needed?!?!
I find hilarious and mind blowing, but not being an English native speaker, I'm afraid I'm reading it wrong 😅

Salut Pierre et bienvenue a NSF!
(d'un bilingue en Floride)

You have it right... Elon loves to troll.

(edit: trimmed fat)

[2megs]

Do SpaceX still have some Dragon 1s available in storage? Would that do the job?

Dragon 1 berths with the CBM, as does Cygnus, so they couldn't go in this spot in this scheme. Dragon 2 (both crewed and cargo) use the IDA, as does Starliner.

For this, either you'd want to put additional fuel and thrusters in the Dragon 2 trunk, or you'd want to modify Cygnus to dock with an IDA. Neither is a simple ask.

Note the current Cygnus mission is already planning to do a reboost from the CBM. I am not sure how much of a boost it's expected to give, or what the pros and cons of doing it from that node are, or how long-term viable that would be. https://spaceflightnow.com/2022/02/21/northrop-grumman-delivers-cargo-and-new-reboost-capability-to-space-station/

Edit: There's also the question of what launcher Cygnus would use in this scenario, as Antares has major parts from both Russia and Ukraine. During the Antares stand-down in 2015 it was launched on Atlas V, so it's not excessively tied to Antares. The HALO part of the PPE-HALO launch on Falcon Heavy is Cygnus-derived, so at least some of that qualification work to put a Cygnus on a Falcon may be shared and/or already underway.

[kevinof]

Do SpaceX still have some Dragon 1s available in storage? Would that do the job?

Dragon 1 berths with the CBM, as does Cygnus, so they couldn't go in this spot in this scheme. Dragon 2 (both crewed and cargo) use the IDA, as does Starliner.

For this, either you'd want to put additional fuel and thrusters in the Dragon 2 trunk, or you'd want to modify Cygnus to dock with an IDA. Neither is a simple ask.

Note the current Cygnus mission is already planning to do a reboost from the CBM. I am not sure how much of a boost it's expected to give, or what the pros and cons of doing it from that node are, or how long-term viable that would be. There's also the question of what launcher Cygnus would use in this scenario. https://spaceflightnow.com/2022/02/21/northrop-grumman-delivers-cargo-and-new-reboost-capability-to-space-station/

Cygnus with extra fuel (and a new launcher)

[hektor]

Why not use a Starship instead of a Dragon or a Cygnus.

Like the HLS one which docks nose first for the Lunar mission with Orion.

[Jim]

. The HALO part of the PPE-HALO launch on Falcon Heavy is Cygnus-derived, so at least some of that qualification work to put a Cygnus on a Falcon may be shared and/or already underway.

Not really.  Completely different configuration.

[rubicondsrv]

Why not use a Starship instead of a Dragon or a Cygnus.

Like the HLS one which docks nose first for the Lunar mission with Orion.

because starship is not ready and even if it was is not designed to be a space station module.

starship (or any other spacecraft) is not the solution to every problem.   

[Jim]

Why not use a Starship instead of a Dragon or a Cygnus.

Doesn't use storable propellant and have low power thrusters.

Hammer and nail analogy

[Tomness]

JWhy not use a Starship instead of a Dragon or a Cygnus.

Like the one which docks nose first for the Lunar mission with Orion.

Store able Propellent. Metholox boils off to quickly. You would need 4 or 5 Tanker Flights get Starship to the ISS. Then a dedicated Tanker to refuel the permanent attachment. It really is easier to start over with Axiom Station.

[hektor]

JWhy not use a Starship instead of a Dragon or a Cygnus.

Like the one which docks nose first for the Lunar mission with Orion.

Store able Propellent. Metholox boils off to quickly. You would need 4 or 5 Tanker Flights get Starship to the ISS. Then a dedicated Tanker to refuel the permanent attachment. It really is easier to start over with Axiom Station.

A Starship is 2 millions per flight. With 24 million a year you can have another one every month. With 100 million one each week

If boil off was such an issue how would the Mars landing work after nine month of transit from Earth

[Jim]

A Starship is 2 millions per flight. With 24 million a year you can have another one every month

Too disruptive.   It isn't 2 million right now. Also, no low power thruster

[Jim]

If boil off was such an issue how would the Mars landing work after nine month of transit from Earth

It is venting and burning it for power.  Not feasible around the ISS.

[hektor]

A Starship is 2 millions per flight. With 24 million a year you can have another one every month

Too disruptive.   It isn't 2 million right now. Also, no low power thruster

If there is no low power thruster how can you dock with this thing (Starship to Starship, Starship to Orion). I doubt you control attitude withRaptor…

[Jim]

A Starship is 2 millions per flight. With 24 million a year you can have another one every month

Too disruptive.   It isn't 2 million right now. Also, no low power thruster

If there is no low power thruster how can you dock with this thing (Starship to Starship, Starship to Orion)

Just stop

[2megs]

Dragon XL would be the best candidate for this (more dV than Dragon 2, more thrusters facing away from the docking adapter), but it's been very quiet on that front. It's not (publicly) clear what its current timeline is, or how much that timeline could be accelerated.

Sorry: https://www.nasaspaceflight.com/2020/03/dragon-xl-nasa-spacex-lunar-gateway-supply-contract/

Thread: https://forum.nasaspaceflight.com/index.php?topic=50467.0

[Jim]

Dragon XL would be the best candidate for this

Not really

[2megs]

Dragon XL would be the best candidate for this

Not really

So I said that because to my mind the ideal solution would have:

* IDA
* Thrusters 180° from the IDA
* Ample dV
* Long-term storable propellant
* Fine/gentle control of thrust
* Rated for up to a year on station

Dragon XL (if available on a useful timeline) is the only thing that would check all of those boxes. Am I thinking of the wrong requirements, or is there something else wrong about Dragon XL?

[nacnud]

Its probably defunct but some systems live on in the Orion service model but could a modified ATV be brought back.

[Jim]

Dragon XL would be the best candidate for this

Not really

So I said that because to my mind the ideal solution would have:

* IDA
* Thrusters 180° from the IDA
* Ample dV
* Long-term storable propellant
* Fine/gentle control of thrust
* Rated for up to a year on station

Dragon XL (if available on a useful timeline) is the only thing that would check all of those boxes. Am I thinking of the wrong requirements, or is there something else wrong about Dragon XL?

Cygnus already meets that and doesn't need an IDA

[daveglo]

Cygnus already meets that and doesn't need an IDA

True enough.  Capability being tested on orbit.

Now we just have to get more Cygnus to orbit. . .

Until Elon/NASA build a better system.

[Bananas_on_Mars]

Dragon XL would be the best candidate for this

Not really

So I said that because to my mind the ideal solution would have:

* IDA
* Thrusters 180° from the IDA
* Ample dV
* Long-term storable propellant
* Fine/gentle control of thrust
* Rated for up to a year on station

Dragon XL (if available on a useful timeline) is the only thing that would check all of those boxes. Am I thinking of the wrong requirements, or is there something else wrong about Dragon XL?

Dragon XL is a little bit like Cygnus on steroids…

If the need arises, there‘s a lot of possibilities. Even Rocketlab has quite capable thrusters with their Hypercurie engine… put a stripped down interplanetary photon in the trunk of a Cargo Dragon if you need to or whatever.

[Yggdrasill]

Too disruptive.   It isn't 2 million right now. Also, no low power thruster

It doesn't have it right now, but it will by the time they start doing orbital propellant transfer. They intend on settling the propellant with milli-G acceleration. If we assume Starship will be capable of 0.005G using methalox hot-gas thrusters, that would be around 0.001G when pushing the ISS around.

That means that for a 1 m/s reboost, Starship would have to burn for around 100 seconds.

I guess the question is really, when will Starship have low power thrusters? I would guess around 2024.

Edt: I guess *maybe* the propellant settling thrusters will still be too powerful. I guess they would actually need to be able to accelerate a fully loaded Starship at several milli-G. At 5 mG that would actually be up to around 70 kN. Which is substantial. I guess it would depend on the arrangement of thrusters and how low they could be throttled. But they should be able to throttle fairly low, to accomodate the full range between empty and full Starships without wasting propellant for propellant settling. So maybe my calculation is fine.

[zodiacchris]

Okay, let’s look at what is available: Cygnus is in production but has a pretty long lead time and if I remember correctly Antares is using Ukrainian components, which will be an issue. But medium term Cygnus could do the job if the launcher issue gets resolved.

Dragon is in production and available on fairly short notice if urgently required, it might need some reshuffling of upcoming missions but it’s eminently doable. Falcons are available off the shelf. So this might be the solution if the situation escalates and the Russian modules become unavailable.

Dragon XL and Starship are not available at this stage, even if Starship flies it will be a long time before that behemoth is allowed anywhere near the ISS. Dragon XL is likely still in design phase, if it ever gets built. Resurrection of discontinued spacecraft is not an option, the supply chains are gone, the facilities re-dedicated and even if possible would take forever.

Just my take on the situation…

[Kiwi53]

Do SpaceX still have some Dragon 1s available in storage? Would that do the job?

Dragon 1 berths with the CBM, as does Cygnus, so they couldn't go in this spot in this scheme. Dragon 2 (both crewed and cargo) use the IDA, as does Starliner.

For this, either you'd want to put additional fuel and thrusters in the Dragon 2 trunk, or you'd want to modify Cygnus to dock with an IDA. Neither is a simple ask.

I would expect that Elon already has a small team looking at "you'd want to put additional fuel and thrusters in the Dragon 2 trunk", with the objective of being able to put an unsolicited proposal to NASA before the end of March. The cost of doing that would be peanuts to SpaceX, so the downside is tiny but the upside is huge.
'SpaceX saves ISS in face of Russian intransigence' would go down very well everywhere except Moscow

[ThomasGadd]

A problem using Dragon 2's most of the Draco's face the wrong way. 
How many are in the clear to fire? 
They would have to be symmetric to minimize torque on the docking ring. 
At 90 lbf each it will be a long burn. 

I'm looking for a description or image of the location of the thrusters ...

[Lar]

A problem using Dragon 2's most of the Draco's face the wrong way. 
How many are in the clear to fire? 
They would have to be symmetric to minimize torque on the docking ring. 
At 90 lbf each it will be a long burn. 

This is an argument for a trunk insert. Proposal by end of March and unit by end of Sept is possible.

[spacenut]

SpaceX can launch Cygnus.  NG could begin to work on new Cygnus craft ASAP.  In the meantime, Space X can put Draco, or Super Draco thrusters in the Trunk of Dragon 2, probably in about the same length of time a new Cygnus can be made.  Gives Two options. 

[Jorge]

SpaceX can launch Cygnus.  NG could begin to work on new Cygnus craft ASAP.  In the meantime, Space X can put Draco, or Super Draco thrusters in the Trunk of Dragon 2, probably in about the same length of time a new Cygnus can be made.  Gives Two options. 

Every time one of you armchair designers suggests using Super Draco for ISS reboost, an ISS structural engineer feels a great disturbance in the Force, as if all the solar array longerons cried out in terror and were suddenly ripped off.

Stop it. Just. Stop. It.

[Jorge]

A problem using Dragon 2's most of the Draco's face the wrong way. 
How many are in the clear to fire? 
They would have to be symmetric to minimize torque on the docking ring. 
At 90 lbf each it will be a long burn. 

Ok, it'll be a long burn.

So?

The space shuttle used vernier RCS thrusters to reboost ISS. Those were 24 lbf each. Required an even longer burn.

Don't optimize your solution on the wrong variable.

[DanClemmensen]

If we are considering spacecraft that do not exist yet, why not look at the Gateway PPE module? It is currently under development and is intended for precisely the function of re-boosting a big space structure. The Artemis programs needs the PPE before it needs Dragon XL, so surely it will be available sooner?

[ThomasGadd]

A problem using Dragon 2's most of the Draco's face the wrong way. 
How many are in the clear to fire? 
They would have to be symmetric to minimize torque on the docking ring. 
At 90 lbf each it will be a long burn. 

Ok, it'll be a long burn.

So?

The space shuttle used vernier RCS thrusters to reboost ISS. Those were 24 lbf each. Required an even longer burn.

Don't optimize your solution on the wrong variable.

I was going look them up and got sidetracked thanks. 
So the existing Dragon 2's should work as long the Draco's are fired symmetrically. 

[russianhalo117]

If we are considering spacecraft that do not exist yet, why not look at the Gateway PPE module? It is currently under development and is intended for precisely the function of re-boosting a big space structure. The Artemis programs needs the PPE before it needs Dragon XL, so surely it will be available sooner?

The current design version of the PPE is undersized for the ISS. An earlier version with the add on European-built Hall Effect Auxiliary Thruster (eHEAT) and the four US Advanced Electric Propulsion System (AEPS) thrusters was more capable. As for the chemical propulsion system I haven't finished my research.

https://rocket.com/space/space-power-propulsion

AR in space propulsion catalog:
https://rocket.com/sites/default/files/documents/In-Space%20Data%20Sheets_7.19.21.pdf

[nacnud]

A problem using Dragon 2's most of the Draco's face the wrong way. 
How many are in the clear to fire? 
They would have to be symmetric to minimize torque on the docking ring. 
At 90 lbf each it will be a long burn. 

This is an argument for a trunk insert. Proposal by end of March and unit by end of Sept is possible.

Thinking about the trunk insert idea it seems it could superficially like the Space Station Freedom Primary Propulsion System. Where a self contained unit is taken up in the trunk mounted to some fixture for use then disposed of on a subsequent flight.

This could give two independent systems for for station reboost, attitude control, and contingency manoeuvres. Namely Cygnus and this trunk insert. It would also give the station control independent of visiting vehicles.

[Lee Jay]

A problem using Dragon 2's most of the Draco's face the wrong way. 
How many are in the clear to fire? 
They would have to be symmetric to minimize torque on the docking ring. 
At 90 lbf each it will be a long burn. 

Ok, it'll be a long burn.

So?

The space shuttle used vernier RCS thrusters to reboost ISS. Those were 24 lbf each. Required an even longer burn.

Don't optimize your solution on the wrong variable.

If a Hohmann transfer uses impulses, is a transfer that uses a substantial fraction of an orbit also named something? Or just spiral?

[FunBobby]

I like the idea of a combination of the near-ish term solutions working for 2-3 years while contracting Axiom or maybe Blue to build one big integrated module that effectively replaces the Russian module with a like amount of Delta V, attitude control, living space etc. 

I still don't like the idea of de-orbiting ISS in 2030, I know how it has soaked up the vast majority of human spaceflight spending for two decades, however perhaps now with better crew delivery and logistics vehicles it can continue to exist and slowly grow without eating everyone's budget.  Yes I know in the long run it is more efficient to just start over even to just not have a permanent LEO station.  However, I think the world loses a valuable cultural symbol about co-operation and persistence.  I would rather just have NASA boost in to 1000KM and seal the hatches to leave it as a museum for another generation to appreciate.  Okay back to the topic - the Cygnus and/or modified Dragon are probably an option by the end of 2022 with a few hundred million thrown at the problem.  Perhaps either HALO/PPE or Dragon XL is a solution for another couple of years.  After that one big (20-30MT) module from Axiom or Blue is the semi-permanent replacement.  Of course I am also hopeful that the ongoing deterioration in International Relations doesn't permanently end the West's co-operation with Russia, so maybe a solution that doesn't involve jettisoning a whole 1/3 of the station is better! 

[fast]

I apologize for the off-topic: the ongoing deterioration of East-West relations has been going on for more than 15 years, my german friend, remarkably some do not notice or do not want to notice it. Only by following the trend it will get worse down the road. If the West value the ISS, there must be an immediate action plan to save it. 

[Baldr]

Cygnus or MEV type would make a better system.

I'm curious as to why (in this thread) you haven't yet claimed that:

A) PMA-1 cannot be undocked from Zarya
B) PMA-1 cannot be unberthed from Unity

In the thread below*, I was attacked by you and others for daring to suggest that A) and B) is possible.

It would seem as if Elon Musk and the International Space Station Editor for @NASASpaceflight believe it's possible, yet you are just posting seemingly crypic messages.

What is this supposed to mean: "Cygnus or MEV type would make a better system"

So, who's right "Jim" or Elon Musk / SpacePete?


* https://forum.nasaspaceflight.com/index.php?topic=55882.0

[Eer]

Cygnus or MEV type would make a better system.

Glad to see MEV mentioned. Seems like a potentially ready to go approach, but I wasn’t sure about how well its exhaust would work in use around the ISS.

[Jorge]

A problem using Dragon 2's most of the Draco's face the wrong way. 
How many are in the clear to fire? 
They would have to be symmetric to minimize torque on the docking ring. 
At 90 lbf each it will be a long burn. 

Ok, it'll be a long burn.

So?

The space shuttle used vernier RCS thrusters to reboost ISS. Those were 24 lbf each. Required an even longer burn.

Don't optimize your solution on the wrong variable.

If a Hohmann transfer uses impulses, is a transfer that uses a substantial fraction of an orbit also named something? Or just spiral?

Depends. A *continuous* multi-orbit low-thrust burn approximates a spiral. But it's also possible to split, say, a 30 minute burn with half the delta-v before and half after the theoretical "impulsive burn" point. This is called a "finite burn". A larger low-thrust reboost can be split into multiple finite burns over multiple orbits, to help shape the final orbit (e.g. burning before and after apogee to raise perigee and circularize the orbit). Whereas if you do a continuous low-thrust "spiral" starting from an elliptical orbit, you'll still be in an elliptical orbit when you finish.

[Patchouli]

Most of Dragon's thrusters face the wrong way and their would be a lot of cosine losses.
The best near term candidate might be the HTV-X.
It can stay on orbit for up to 2 years.

[kevinof]

Most of Dragon's thrusters face the wrong way and their would be a lot of cosine losses.
The best near term candidate might be the HTV-X.
It can stay on orbit for up to 2 years.

Good choice but would need a docking port if it doesn’t already have one.

[Cherokee43v6]

I've seen some twitching around the periphery of this but feel that it should be stated clearly.

If it is decided that something like this is needed, it is going to be a short-term/immediate need.  (I fear a 'take my ball and go home' scenario) There will not be time to design and fabricate something from scratch to fill this role.  That almost certainly eliminates Starship, DragonXL and a revived European ATV.

It also eliminates designing and building an IDA for PMA-1.  PMA-1's docking port is not the same as the others since it mates to a Russian designed and built module.  Thus, in any separation of the two sides, it makes more sense to separate PMA-1 from Node1 and then use the CBM port there for the mounting (Cygnus, HTV or a Dragon1) giving thrust on the long axis.

And Axiom can't help either, because the last item in their launch plan is their PPE, which means they need ISS (and particularly Canadarm2) for their assembly worksite.  Loss of ISS puts their whole project in jeopardy. 

[spacenut]

Well if Super Draco's are too powerful, the smaller Dracos could be used with an inserted tankage with Draco's in Dragon's trunk.  Why can't that work?  Also why not put several VASMR thrusters on the ISS with propellant and keep it stabilized.  This has already been tried with success.  With enough of these strategically placed on the ISS, that too should work slowly and not tear off the Solar panels. 

There are a lot of good ideas and solutions.  Just mobilize and get this going before Russia does something drastic. 

[DanClemmensen]

I've seen some twitching around the periphery of this but feel that it should be stated clearly.

If it is decided that something like this is needed, it is going to be a short-term/immediate need.  (I fear a 'take my ball and go home' scenario) There will not be time to design and fabricate something from scratch to fill this role.  That almost certainly eliminates Starship, DragonXL and a revived European ATV.

It also eliminates designing and building an IDA for PMA-1.  PMA-1's docking port is not the same as the others since it mates to a Russian designed and built module.  Thus, in any separation of the two sides, it makes more sense to separate PMA-1 from Node1 and then use the CBM port there for the mounting (Cygnus, HTV or a Dragon1) giving thrust on the long axis.

And Axiom can't help either, because the last item in their launch plan is their PPE, which means they need ISS (and particularly Canadarm2) for their assembly worksite.  Loss of ISS puts their whole project in jeopardy.

Yep. There is a short(?) window in which the priority must be to delay the catastrophic loss of ISS by slowing or stopping orbital decay and enabling any required evasive maneuvering. The vehicles and procedures to do this do not need to be optimal, cheap, or long-lasting. They just need to work before it's too late. If this involves expending one or more Dragon 2s or whatever, then so be it. This kludged-up method only needs to work long enough to put a longer-term solution in place to either maintain or replace ISS.

[ThomasGadd]

Dragon 2 has 16 Dracos.  if line up enough (4?) to reboost ISS even with cosine losses. 

We don't want to invent something new. 

[Jim]

Cygnus or MEV type would make a better system.

I'm curious as to why (in this thread) you haven't yet claimed that:

A) PMA-1 cannot be undocked from Zarya
B) PMA-1 cannot be unberthed from Unity

In the thread below*, I was attacked by you and others for daring to suggest that A) and B) is possible.

It would seem as if Elon Musk and the International Space Station Editor for @NASASpaceflight believe it's possible, yet you are just posting seemingly crypic messages.

What is this supposed to mean: "Cygnus or MEV type would make a better system"

So, who's right "Jim" or Elon Musk / SpacePete?

Just too tired of dealing with the nonsense on multiple threads. 

And Musk is not an ISS expert.

And fighting that everything is a nail and SpaceX hardware is the hammer.

[alugobi]

There's definitely a lot of that.

But the solution is simple.

[Jim]

There's definitely a lot of that.

But the solution is simple.

No, it isn't

[jdon759]

Is the ICM still around?

If it actually becomes necessary to replace the ROS, could that do it?  It is almost exactly what it was designed for.

[Jorge]

There's definitely a lot of that.

But the solution is simple.

No, it isn't

Most of these guys are fixated on reboost and that isn't even the hardest problem (though it is plenty hard). CMG desat is. It's harder because it has to be more tightly integrated into ISS GNC.

ISS is many months away from decaying to the "no-return" altitude. But at any given time, if the CMGs saturate and there are no thrusters to desat, ISS loses attitude control and from that point its power/thermal lifetime is measured in days, if not hours.

[Jorge]

Is the ICM still around?

If it actually becomes necessary to replace the ROS, could that do it?  It is exactly what it was designed for.

ICM was designed to control ISS up to stage 7A.1. ISS is way too big for that now.

[jdon759]

Is the ICM still around?

If it actually becomes necessary to replace the ROS, could that do it?  It is exactly what it was designed for.

ICM was designed to control ISS up to stage 7A.1. ISS is way too big for that now.

Ok, good to know.
If you were to redesign the ICM for the ISS's international segment as it is now, how would you do it?

[AllenB]

Just too tired of dealing with the nonsense on multiple threads. 

And Musk is not an ISS expert.

And fighting that everything is a nail and SpaceX hardware is the hammer.

Assuming no "off the shelf" solution exists to stabilize ISS absent Russian involvement (and I think we all agree on that), some improvisation will be required.

Right now, in 2022, is there any organization with the right combination of assets (human and machine) more qualified to tackle this than SpaceX? I can't think of one.

Not trying to fan-boy here (seriously!) but nobody else seems to have both reached the stage of having significant capability while also not yet having lost their appetite for risk due to time and bureaucracy.

[spacenut]

The reason SpaceX is mentioned so much for any solutions is they are the only reliable launcher with plenty of rockets to get things to the ISS.  They also have a lot of different equipment.  Dragon I's, Dragon II's, Draco's, Super Draco's, empty trunks, reusable supply of boosters.  They can make plenty of second stages.  They can hold back on Starlink launches if ISS needs something launched.  They also have Falcon Heavy.  They are more than capable to help with ISS.  They can launch for other competitors with maybe very little adaption. 

Antares is hurt because of Ukraine for a launcher.

BE-4 is late, thus Vulcan and New Glenn. 

All Atlas V's are contracted for launches.

No more Delta IV's to be launched.  Even in production can resume, what about RS-68, can it be resumed? 

Neutron is not ready. 

No one else right now has the capability to get something done quickly with ISS, except SpaceX. 

[whitelancer64]

Cygnus or MEV type would make a better system.

I'm curious as to why (in this thread) you haven't yet claimed that:

A) PMA-1 cannot be undocked from Zarya
B) PMA-1 cannot be unberthed from Unity

In the thread below*, I was attacked by you and others for daring to suggest that A) and B) is possible.

*snip*

A. The motor drivers that drove the 16 bolts that connect PMA-1 to Zarya were externally controlled via cables that ran to the Shuttle (STS-88, December 1998). These cables were removed during the second ISS assembly spacewalk, and probably no longer exist. There is no way to control these bolts from within the ISS, so effectively, PMA-1 and Zarya are permanently joined together.

"The last task for today will be to disconnect and stow cables that were used by Endeavour's crew to control the docking mechanism, called the Androgynous Peripheral Attach System (APAS), that docked Zarya to Unity earlier in the mission. With that system never again to be opened, the cable used by Endeavour to control it, which runs along Pressurized Mating Adapter 2 (PMA 2), will be disconnected on this spacewalk"

https://science.ksc.nasa.gov/shuttle/missions/sts-88/sts-88-day-07-highlights.html

B. PMA-1 was installed on Unity / Node 1 on the ground, before launch on STS-88. It was never meant to be removed from Unity, so I presume it also was permanently installed with no reasonable way to remove it from Unity via a spacewalk. However, I don't know the details of its installation. Perhaps someone else can chime in with details.

[Comga]

Cygnus or MEV type would make a better system.

So might HTV-X.
And since we are discussing systems not currently flying, we could include the SNC Shooting Star.

Assertions like the one above with no criteria or other information are "references to authority".
No matter how much we respect Jim for his proven insight and insider information, just throwing that out doesn't add to the discussion.
This is not saying "wrong!"
It's asking how either of those could be produced as  a "better" comprehensive solution in a reasonable time for a reasonable cost.
Can you explain how and why Cygnus or MEV would be better?

But....
"Better is the enemy of good enough"

"Better" is also why many things stagnated for decades.  Trying to make perfect systems always fails.
Atlas-V is "better" than Falcon 9 by many metrics, but it misses on several including cost and now availability
SLS is "better" than Falcon Heavy in throw weight and other metrics, but it will have taken 2 to 5 times as long between announcement and first flight, be more than ten times as expensive, and have no flexibility of production.

"Better" should be a global metric.
It includes a supplier who comes up with creative and effective solutions quickly.

What examples do we have of quick and effective developments for spacecraft requirements?

[Jorge]

Ok, good to know.
If you were to redesign the ICM for the ISS's international segment as it is now, how would you do it?

Can't

Can't is a pretty strong statement. But I agree it's not really practical (or maybe even practicable).

First, groundrules: ICM was originally meant to attach to the aft end of FGB (the probe on the aft end of FGB would have to be replaced with a passive APAS first). Detaching the Russian modules isn't going to happen. So it needs to attach to Node 2 Forward, and ISS would have to yaw 180 degrees for each reboost (no big deal, it did so for space shuttle reboosts).

So, list of mods off the top of my head:
1) Gut the interior to accommodate a pressurized tunnel with hatches, so that Dragon and Starliner can dock to ICM Forward and the crew can pass through to the rest of the station. This will require rebuilding the propellant tanks, of course, since they're currently in the way. The module will also get bigger if you want to keep the same propellant capacity (and you will, if not more).
2) Replace the APAS docking hardware with NDS (but even then, you need mods, if you're serious about ICM being anything other than "interim", as I'll get to later).
3) Upgrade the ICM GNC software to accommodate desat commanding from ISS via the NDS 1553 bus (ICM was originally designed for purely propulsive attitude control, which will deplete the tanks quickly trying to control today's much larger ISS).
4) The ICM roll thrusters don't have enough control authority considering ISS's colossal roll moment of inertia. Consider lengthening the deployable booms the thrusters are mounted on, to increase the control moment.
Saving possibly the biggest two for last,
5) The ICM propellant tanks aren't refillable, and the current NDS docking interface doesn't support fluid transfer. The US as a whole has never demonstrated in-space hypergolic propellant transfer, so this is a fairly sizable R&D item. Again, this is only if you expect ICM to be anything other than "interim".
6) You need a way to get ICM to ISS. Originally ICM would have ridden up in the shuttle payload bay, be berthed to the ODS by the RMS, then docked to the FGB. So it didn't need any active rendezvous/prox ops/docking capability. Whether you have ICM deliver itself, or have another vehicle (e.g. Dragon or Starliner) do it, you'll need active rendezvous sensors on the ICM active NDS side, and passive docking aids on the passive NDS side. If ICM delivers itself, the ICM GNC system needs to be upgraded to be capable of rendezvous/prox ops/docking, otherwise it needs a 1553 pass-through to get the data from the ICM rendezvous sensors to whatever vehicle is delivering it (and that vehicle's rendezvous GNC system has to be upgraded to accept sensor data from an external source, and be able to control itself with the ICM mounted on front).

Not impossible, but I'm hard pressed to state what, if any, original ICM hardware would remain after all these upgrades. Better to start with a clean sheet.

[Jim]

Not impossible, but I'm hard pressed to state what, if any, original ICM hardware would remain after all these upgrades. Better to start with a clean sheet.

That is why I say "can't".  It isn't an ICM anymore. 

[Jim]

Right now, in 2022, is there any organization with the right combination of assets (human and machine) more qualified to tackle this than SpaceX? I can't think of one.

Yes, NG, Maxar, or LM.  Not going to say Boeing.

NG has Cygnus and MEV.  Maxar has its electric buses. 

LM has SSB.

[JayWee]

It might not be either/or. But a collaborative effort.

[JayWee]

The reason SpaceX is mentioned so much for any solutions is they are the only reliable launcher with plenty of rockets to get things to the ISS.  They also have a lot of different equipment.  Dragon I's, Dragon II's, Draco's, Super Draco's, empty trunks, reusable supply of boosters.  They can make plenty of second stages.  They can hold back on Starlink launches if ISS needs something launched.  They also have Falcon Heavy.  They are more than capable to help with ISS.  They can launch for other competitors with maybe very little adaption. 

Antares is hurt because of Ukraine for a launcher.

BE-4 is late, thus Vulcan and New Glenn. 

All Atlas V's are contracted for launches.

No more Delta IV's to be launched.  Even in production can resume, what about RS-68, can it be resumed? 

Neutron is not ready. 

No one else right now has the capability to get something done quickly with ISS, except SpaceX. 

I'd say it could be theoretically be possible to exchange some Amazon Atlas V's for delay in the constellation deployment time limit.

But even then - how long does it take from order to launch for Atlas V ? Swapping Starlink launch scheduled few weeks away for something, I guess, is a matter of a phone call.

[Jeff Lerner]

Things seem to moving at breakneck speed…all the proposed solutions here seem to require weeks, months, etc…what happens if Putin decides within days to shut the RUssian segments of ISS down ?

I know the Astronauts and cosmonauts and support centres are all consummate professionals but does anyone have any idea what the current state of ISS Crew relations are ?..must be very difficult to float by a crew member without saying something about what’s going on ..

[Surfdaddy]

If Starliner had not been pathetically late, perhaps it could have helped reboosts.
Alas.

[Baldr]

Cygnus or MEV type would make a better system.

I'm curious as to why (in this thread) you haven't yet claimed that:

A) PMA-1 cannot be undocked from Zarya
B) PMA-1 cannot be unberthed from Unity

In the thread below*, I was attacked by you and others for daring to suggest that A) and B) is possible.

*snip*

A. The motor drivers that drove the 16 bolts that connect PMA-1 to Zarya were externally controlled via cables that ran to the Shuttle (STS-88). These cables were removed during the second ISS assembly spacewalk, and probably no longer exist. There is no way to control these bolts from within the ISS, so effectively, PMA-1 and Zarya are permanently joined together.

"The last task for today will be to disconnect and stow cables that were used by Endeavour's crew to control the docking mechanism, called the Androgynous Peripheral Attach System (APAS), that docked Zarya to Unity earlier in the mission. With that system never again to be opened, the cable used by Endeavour to control it, which runs along Pressurized Mating Adapter 2 (PMA 2), will be disconnected on this spacewalk"

https://science.ksc.nasa.gov/shuttle/missions/sts-88/sts-88-day-07-highlights.html

B. PMA-1 was installed on Unity / Node 1 on the ground, before launch on STS-88. It was never meant to be removed from Unity, so I presume it also was permanently installed with no reasonable way to remove it from Unity via a spacewalk. However, I don't know the details of its installation. Perhaps someone else can chime in with details.

The cables went from the APAS on PMA-2 to the APAS on PMA-1. When the APAS on PMA-2 was docked to the APAS on the ODS, Unity could receive power from Endeavour (through APAS) and the APAS on PMA-1 could be controlled from the cockpit (cabling signal transmitted through the two docked APAS systems on ODS/PMA-2).

Full Quote: The last task for today will be to disconnect and stow cables that were used by Endeavour's crew to control the docking mechanism, called the Androgynous Peripheral Attach System (APAS), that docked Zarya to Unity earlier in the mission. With that system never again to be opened, the cable used by Endeavour to control it, which runs along Pressurized Mating Adapter 2 (PMA 2), will be disconnected on this spacewalk as a "get-ahead task" for future assembly missions when PMA 2, currently the adapter to which Endeavour is docked, will be moved.

-

Now, I can't see why it's not possible to route new cables -- for which I assume the blueprints still exists -- to the APAS on PMA-1 and with the cabling routed through, say, a docked cargo vehicle and into the interior of the ISS where the undocking would be controlled from.

Quite a few of the components on the HST were also not designed to be replaced, yet several spacewalks were undertaken that were originally not planned for.

[Baldr]

Things seem to moving at breakneck speed…all the proposed solutions here seem to require weeks, months, etc…what happens if Putin decides within days to shut the RUssian segments of ISS down ?

I know the Astronauts and cosmonauts and support centres are all consummate professionals but does anyone have any idea what the current state of ISS Crew relations are ?..must be very difficult to float by a crew member without saying something about what’s going on ..

Yesterday, I suggested to use the Artemis 1 spacecraft (Orion capsule and service module) to replace, at least, the attitude control and desaturation maneuvers (CMG) of the Russian Segment. What's important would be to get the Artemis 1 docked to the ISS ASAP. What is valuable is the Service Module and not the Orion capsule.

https://forum.nasaspaceflight.com/index.php?topic=55882.0

[Brovane]

Right now, in 2022, is there any organization with the right combination of assets (human and machine) more qualified to tackle this than SpaceX? I can't think of one.

Yes, NG, Maxar, or LM.  Not going to say Boeing.

NG has Cygnus and MEV.  Maxar has its electric buses. 

LM has SSB.

I think in this instance the interests of all the parties involved would be best served by SpaceX just being the launch provider. 

[butters]

No one else right now has the capability to get something done quickly with ISS, except SpaceX.

Perhaps no one else right now has the capability to launch something (other than Starliner) to the ISS, but others have spacecraft that could be launched on Falcon 9, and one or more of them are closer to filling the capability gaps than SpaceX is with Dragon. Northrop Grumman, for example, is not going to turn down a NASA contract for ISS propulsion / attitude control just because they might have to launch their spacecraft on Falcon 9. We haven't somehow transitioned into an era where only complete vertical solutions need apply.

[nacnud]

There's definitely a lot of that.

But the solution is simple.

No, it isn't

Most of these guys are fixated on reboost and that isn't even the hardest problem (though it is plenty hard). CMG desat is. It's harder because it has to be more tightly integrated into ISS GNC.

ISS is many months away from decaying to the "no-return" altitude. But at any given time, if the CMGs saturate and there are no thrusters to desat, ISS loses attitude control and from that point its power/thermal lifetime is measured in days, if not hours.

I believe that atmo drag (maybe light pressure, whichever) can be used to achieve CMG desat, cunning orientation of the station is required. Cygnus can then be used for reboot.

That should give time for someone to build something.

[Lee Jay]

There's definitely a lot of that.

But the solution is simple.

No, it isn't

Most of these guys are fixated on reboost and that isn't even the hardest problem (though it is plenty hard). CMG desat is. It's harder because it has to be more tightly integrated into ISS GNC.

Thanks for answering my previous question, Jorge. I have another.

How often do desats typically have to happen or is that heavily dependent on atmosphere and orientation?

[Jim]

Right now, in 2022, is there any organization with the right combination of assets (human and machine) more qualified to tackle this than SpaceX? I can't think of one.

Yes, NG, Maxar, or LM.  Not going to say Boeing.

NG has Cygnus and MEV.  Maxar has its electric buses. 

LM has SSB.

I think in this instance the interests of all the parties involved would be best served by SpaceX just being the launch provider.

Not true either.

[Jim]

Things seem to moving at breakneck speed…all the proposed solutions here seem to require weeks, months, etc…what happens if Putin decides within days to shut the RUssian segments of ISS down ?

I know the Astronauts and cosmonauts and support centres are all consummate professionals but does anyone have any idea what the current state of ISS Crew relations are ?..must be very difficult to float by a crew member without saying something about what’s going on ..

Yesterday, I suggested to use the Artemis 1 spacecraft (Orion capsule and service module) to replace, at least, the attitude control and desaturation maneuvers (CMG) of the Russian Segment. What's important would be to get the Artemis 1 docked to the ISS ASAP. What is valuable is the Service Module and not the Orion capsule.

https://forum.nasaspaceflight.com/index.php?topic=55882.0

No, the Service module doesn’t [have] the thrusters to do Desat

[Jim]

No one else right now has the capability to get something done quickly with ISS, except SpaceX.

Perhaps no one else right now has the capability to launch something (other than Starliner) to the ISS, but others have spacecraft that could be launched on Falcon 9, and one or more of them are closer to filling the capability gaps than SpaceX is with Dragon. Northrop Grumman, for example, is not going to turn down a NASA contract for ISS propulsion / attitude control just because they might have to launch their spacecraft on Falcon 9. We haven't somehow transitioned into an era where only complete vertical solutions need apply.

Atlas is available inf needed.

[butters]

Atlas is available inf needed.

I should hope Bezos would be so accommodating as to trade one of Kuiper's Atlases for a Vulcan if it's necessary to keep the ISS in orbit. It would be a real heel turn if he made a fuss about that.

[zubenelgenubi]

I'm curious as to why (in this thread) you haven't yet claimed that:

A) PMA-1 cannot be undocked from Zarya
B) PMA-1 cannot be unberthed from Unity

In the thread below*, I was attacked by you and others for daring to suggest that A) and B) is possible.
<snip>
* https://forum.nasaspaceflight.com/index.php?topic=55882.0

Moderator:
No, you were corrected, and you refused to listen.

Yesterday, I suggested to use the Artemis 1 spacecraft (Orion capsule and service module) to replace, at least, the attitude control and desaturation maneuvers (CMG) of the Russian Segment. What's important would be to get the Artemis 1 docked to the ISS ASAP. What is valuable is the Service Module and not the Orion capsule.

https://forum.nasaspaceflight.com/index.php?topic=55882.0

Moderator:
Yes, and you wouldn't listen to the reasons as to why your inkling of a proposal wouldn't work in that thread.

And, you insulted other members, including one who actually has decades of spaceflight engineering experience, resulting in moderator actions against you in that thread.

Just as moderators have taken similar actions against you in this thread.

Bravo. 👏

[zubenelgenubi]

Atlas is available if needed.

I should hope Bezos would be so accommodating as to trade one of Kuiper's Atlases for a Vulcan if it's necessary to keep the ISS in orbit. It would be a real heel turn if he made a fuss about that.

My hypothesis: There is contract language allowing ULA to re-purpose launch vehicle(s) in case of an emergency.

Experts, what say you?

[zubenelgenubi]

LM has SSB.

= Satellite Support Bus for the KH-11 reconnaissance satellites

[zubenelgenubi]

Incredible necrothreading!
See ICM - (International Space Station) Interim Control Module

Is the ICM still around?

If it actually becomes necessary to replace the ROS, could that do it?  It is almost exactly what it was designed for.

Yea it exists but was returned to the DoD as no longer needed. Last I heard several years ago it was slated for modifications for permanent display and transfer to a museum or face scrapping. The surplus hardware inventory is gradually being cleared out over time to cut down on mothballed and clean room storage costs.

[Jorge]

There's definitely a lot of that.

But the solution is simple.

No, it isn't

Most of these guys are fixated on reboost and that isn't even the hardest problem (though it is plenty hard). CMG desat is. It's harder because it has to be more tightly integrated into ISS GNC.

Thanks for answering my previous question, Jorge. I have another.

How often do desats typically have to happen or is that heavily dependent on atmosphere and orientation?

Heavily dependent on both of those, plus disturbances (visiting vehicle approaches/departures, EVAs, robotic arm ops).

[Baldr]

Things seem to moving at breakneck speed…all the proposed solutions here seem to require weeks, months, etc…what happens if Putin decides within days to shut the RUssian segments of ISS down ?

I know the Astronauts and cosmonauts and support centres are all consummate professionals but does anyone have any idea what the current state of ISS Crew relations are ?..must be very difficult to float by a crew member without saying something about what’s going on ..

Yesterday, I suggested to use the Artemis 1 spacecraft (Orion capsule and service module) to replace, at least, the attitude control and desaturation maneuvers (CMG) of the Russian Segment. What's important would be to get the Artemis 1 docked to the ISS ASAP. What is valuable is the Service Module and not the Orion capsule.

https://forum.nasaspaceflight.com/index.php?topic=55882.0

No, the Service module doesn’t [have] the thrusters to do Desat

Orion's Service Module has got 24 x 220 N vernier thrusters.

The Zvezda SM on the ISS has got 32 x (∼129 N) vernier thrusters.

The Progress spacecraft has got 14 x (∼129 N) vernier thrusters and 12 thrusters with a lower thrust of 26 N


Again, can you explain why an Orion Service Module can't perform desaturation maneuvers for the ISS instead of just saying it hasn't got the thrusters to do it.

[Brovane]

Right now, in 2022, is there any organization with the right combination of assets (human and machine) more qualified to tackle this than SpaceX? I can't think of one.

Yes, NG, Maxar, or LM.  Not going to say Boeing.

NG has Cygnus and MEV.  Maxar has its electric buses. 

LM has SSB.

I think in this instance the interests of all the parties involved would be best served by SpaceX just being the launch provider.

Not true either.

Why? 

[Brovane]

Atlas is available if needed.

I should hope Bezos would be so accommodating as to trade one of Kuiper's Atlases for a Vulcan if it's necessary to keep the ISS in orbit. It would be a real heel turn if he made a fuss about that.

My hypothesis: There is contract language allowing ULA to re-purpose launch vehicle(s) in case of an emergency.

Experts, what say you?

What specific need in this scenario is the Atlas-V filling that the F9 cannot?  The only thing I can think of is VI and it isn't a SpaceX LV.  Is there something else? 

[rubicondsrv]

What specific need in this scenario is the Atlas-V filling that the F9 cannot?  The only thing I can think of is VI and it isn't a SpaceX LV.  Is there something else? 

cygnus has already launched on atlas.  would be faster than qualifying it for falcon. 

[Jim]

[Re: undocking Zarya from PMA-1]

Because the cables and controllers that are gone were Russian made.

[Jim]

[deleted]

By making nonsensical claims such a partially fulled ICPS or Orion service module being able to desat CMGs

[Robotbeat]

Cygnus or MEV type would make a better system.

agreed. That is suggested in the thread. But Antares is no longer an option, all the Atlas Vs are spoken for, and Vulcan isn’t yet ready. So the logical choice would be Falcon 9, in that thread. So SpaceX would still be a critical part of it.

SpaceX does have Dragon XL under some level of development. Could be expedited and modified to be better suited for this purpose.

[Jim]

all the Atlas Vs are spoken for,

Can't say that in this case.

[Robotbeat]

Are you sure? I mean, ISS is really important for NASA, but theoretically, we could be at a state of increased tension that would mean any available Atlas Vs would be needed for launching satellites in case Russia destroys US military satellites.

Even if they don’t do it, I would think preserving those Atlas Vs for military launch would be higher priority than ISS.

[Robotbeat]

There's definitely a lot of that.

But the solution is simple.

No, it isn't

Most of these guys are fixated on reboost and that isn't even the hardest problem (though it is plenty hard). CMG desat is. It's harder because it has to be more tightly integrated into ISS GNC.

ISS is many months away from decaying to the "no-return" altitude. But at any given time, if the CMGs saturate and there are no thrusters to desat, ISS loses attitude control and from that point its power/thermal lifetime is measured in days, if not hours.

I believe that atmo drag (maybe light pressure, whichever) can be used to achieve CMG desat, cunning orientation of the station is required. Cygnus can then be used for reboot.

That should give time for someone to build something.

This was my exact question.

I saw a report that showed the solar arrays can be used for desat.

This may be a function of altitude. Maybe at high altitude, it’s not sufficient. I’ll have to pull it up.

[Brovane]

What specific need in this scenario is the Atlas-V filling that the F9 cannot?  The only thing I can think of is VI and it isn't a SpaceX LV.  Is there something else? 

cygnus has already launched on atlas.  would be faster than qualifying it for falcon.

What was required to qualify the Cygnus to fly on the Atlas-V? 

[Baldr]

Because the cables and controllers that are gone were Russian made.

So, the options are:

A) Purchase new cables and controllers from the Russians (even if they are no longer in production, I'm quite sure the blueprints are available somewhere -- for the right amount of $$$, of course).

B) Reverse engineer the cables and controllers.

[rubicondsrv]

So, the options are:

A) Purchase new cables and controllers from the Russians (even if they are no longer in production, I'm quite sure the blueprints are available somewhere -- for the right amount of $$$, of course).

B) Reverse engineer the cables and controllers.

or C

leave the dead Russian modules in place and control the station from new modules and dont bother with separating the Russian bits.

why bother with detachment if alternate means exist.

 

[Jim]

A) Purchase new cables and controllers from the Russians (even if they are no longer in production, I'm quite sure the blueprints are available somewhere -- for the right amount of $$$, of course).

B) Reverse engineer the cables and controllers.

A is not going to happen.  That is why we are this situation.  If they nice enough to help us, we don't need to do the separation.

b.  We don't know enough to do that.

[Reynold]

A) Purchase new cables and controllers from the Russians (even if they are no longer in production, I'm quite sure the blueprints are available somewhere -- for the right amount of $$$, of course).

B) Reverse engineer the cables and controllers.

A is not going to happen.  That is why we are this situation.  If they nice enough to help us, we don't need to do the separation.

b.  We don't know enough to do that.

Yeah, I agree with Jim for B, I've had some involvement with reverse engineering, and it is really hard, verging on impossible, if you don't have the widgets you are trying to reverse engineer available.  In this case one end of the system is up on the ISS, and the other end is either in a warehouse in Russia or thrown away if they didn't bother to keep it somewhere. 

[zubenelgenubi]

Moderator:
Civil, on-topic discourse, with no general politics, or lose your post.  Space policy posts go in the appropriate Space Policy thread.

It's that simple.

[FunBobby]

Sorry if I missed this further up in the thread but as a guide to discussion of options:  Lets say that NASA has found a series of short term solutions be docking vehicles to assist with attitude control and orbital boost and would dock to the current configuration.  Since the RUS modules remain property of the RUS Federation, would it be desirable and practical for them to actually disconnect the whole thing?  Or is it more likely they would flip off the circuit breakers and just lock the doors on their way into the Soyuz?  Detaching it all and sending it into the atmosphere is pretty permanent and perhaps in several months or a few years relations will improve?

Also, potentially wacky idea, but would it be possible or desirable to perform attitude control with a vehicle that isn't docked up attached via CANADARM?  Maybe that gives a little leverage and room for thrusters to fire in the appropriate direction without burning stuff.

[Jim]

Also, potentially wacky idea, but would it be possible or desirable to perform attitude control with a vehicle that isn't docked up attached via CANADARM?  Maybe that gives a little leverage and room for thrusters to fire in the appropriate direction without burning stuff.

no

[zubenelgenubi]

Also, potentially wacky idea, but would it be possible or desirable to perform attitude control with a vehicle that isn't docked up attached via CANADARM?  Maybe that gives a little leverage and room for thrusters to fire in the appropriate direction without burning stuff.

no

Sweet Jesus, Mary, and Joseph!

Canadarm is not designed or manufactured to withstand the necessary forces or torques.

Think of the moment arm that you are hypothesizing.

It would be like Beowulf ripping Grendel's arm off.

That's no Fun, Bobby.

[Barley]

Also, potentially wacky idea, but would it be possible or desirable to perform attitude control with a vehicle that isn't docked up attached via CANADARM?  Maybe that gives a little leverage and room for thrusters to fire in the appropriate direction without burning stuff.

no

Sweet Jesus, Mary, and Joseph!

Canadarm is not designed or manufactured to withstand the necessary forces or torques.

Think of the moment arm that you are hypothesizing.

It would be like Beowulf ripping Grendel's arm off.

That's no Fun, Bobby.

Lets think about this using numbers.

The thrusters are at most few hundred newtons.  If that will rip Canadaarm off, it is in severe danger anchoring an astronaut.

[matthewkantar]

A) Purchase new cables and controllers from the Russians (even if they are no longer in production, I'm quite sure the blueprints are available somewhere -- for the right amount of $$$, of course).

B) Reverse engineer the cables and controllers.

A is not going to happen.  That is why we are this situation.  If they nice enough to help us, we don't need to do the separation.

b.  We don't know enough to do that.

This is hilarious to me. Calls for a classic "We can put a man on the moon, but cant kludge up some wiring?"

[Lee Jay]

A) Purchase new cables and controllers from the Russians (even if they are no longer in production, I'm quite sure the blueprints are available somewhere -- for the right amount of $$$, of course).

B) Reverse engineer the cables and controllers.

A is not going to happen.  That is why we are this situation.  If they nice enough to help us, we don't need to do the separation.

b.  We don't know enough to do that.

This is hilarious to me. Calls for a classic "We can put a man on the moon, but cant kludge up some wiring?"

If you don't have the interface spec, which pins do what, communication protocols, voltages and currents required, and so on, how would you do it?  If you have all that stuff, it's relatively trivial to build a cable. If you don't, it's almost impossible.

[FunBobby]

Also, potentially wacky idea, but would it be possible or desirable to perform attitude control with a vehicle that isn't docked up attached via CANADARM?  Maybe that gives a little leverage and room for thrusters to fire in the appropriate direction without burning stuff.

no

Sweet Jesus, Mary, and Joseph!

Canadarm is not designed or manufactured to withstand the necessary forces or torques.

Think of the moment arm that you are hypothesizing.

It would be like Beowulf ripping Grendel's arm off.

That's no Fun, Bobby.

So Hence my qualification as a potentially wacky idea.  I know full well that CANADARM wasn't designed to do something like that, just wondering if there was a potential that it could.  If the required forces are far too great then of course the answer is no.  I couldn't help but jump down the Apollo 13 fitting a square peg into a round hole with just using this stuff kind of rabbit hole.  So if M = f x d and the CANADARM stretched out is about 20 Meters long, then a  5lb thruster firing perpendicular puts almost 400 lb/ft of Torque on the arm?  Anyways, all of this falls more into what if NASA needed a solution in days or hours and had to kludge something together that MIGHT work.

[Robotbeat]

In the trunk is better because it doesn’t require modifying or interfacing with the cargo Dragon systems.

It could even be supplied by some other company, like NG.

[AstroWare]

In the trunk is better because it doesn’t require modifying or interfacing with the cargo Dragon systems.

It could even be supplied by some other company, like NG.

The propulsion module of Cygnus looks like already fits..

Don't have a good source for the exact dimensions of the new dragon trunk, nor the service module section of Cygnus...

But from what I can find:
Cygnus = 6.4m (L) x 3.1m (Dia)
Cygnus SM ~ 1/4 total length = 1.6m (L)
Dragon Trunk = 37m^3 @ 3.6m (Dia) =  3.6m (L)
 
So Room to spare...

Cygnus SM = 1800kg, which is within the total payload of Dragon.

It could be simplified too:
just the main engine (no smaller thrusters)
No solar arrays

If you retain the communication equipment, it could operate independent on dragon so no interface issues across the sep plane...

And heritage should make approving it to operate it on the ISS simpler

Sent from my Pixel 5a using Tapatalk

[rakaydos]

In the trunk is better because it doesn’t require modifying or interfacing with the cargo Dragon systems.

It could even be supplied by some other company, like NG.

The propulsion module of Cygnus looks like already fits..

Don't have a good source for the exact dimensions of the new dragon trunk, nor the service module section of Cygnus...

But from what I can find:
Cygnus = 6.4m (L) x 3.1m (Dia)
Cygnus SM ~ 1/4 total length = 1.6m (L)
Dragon Trunk = 37m^3 @ 3.6m (Dia) =  3.6m (L)
 
So Room to spare...

Cygnus SM = 1800kg, which is within the total payload of Dragon.

It could be simplified too:
just the main engine (no smaller thrusters)
No solar arrays

If you retain the communication equipment, it could operate independent on dragon so no interface issues across the sep plane...

And heritage should make approving it to operate it on the ISS simpler

Sent from my Pixel 5a using Tapatalk

At what point does a "heritage equipment" kludge become "rockets are not legos"?

[rubicondsrv]

In the trunk is better because it doesn’t require modifying or interfacing with the cargo Dragon systems.

It could even be supplied by some other company, like NG.

The propulsion module of Cygnus looks like already fits..

Don't have a good source for the exact dimensions of the new dragon trunk, nor the service module section of Cygnus...

But from what I can find:
Cygnus = 6.4m (L) x 3.1m (Dia)
Cygnus SM ~ 1/4 total length = 1.6m (L)
Dragon Trunk = 37m^3 @ 3.6m (Dia) =  3.6m (L)
 
So Room to spare...

Cygnus SM = 1800kg, which is within the total payload of Dragon.

It could be simplified too:
just the main engine (no smaller thrusters)
No solar arrays

If you retain the communication equipment, it could operate independent on dragon so no interface issues across the sep plane...

And heritage should make approving it to operate it on the ISS simpler

Sent from my Pixel 5a using Tapatalk

why not just use cygnus then?   

[AstroWare]

In the trunk is better because it doesn’t require modifying or interfacing with the cargo Dragon systems.

It could even be supplied by some other company, like NG.

The propulsion module of Cygnus looks like already fits..

Don't have a good source for the exact dimensions of the new dragon trunk, nor the service module section of Cygnus...

But from what I can find:
Cygnus = 6.4m (L) x 3.1m (Dia)
Cygnus SM ~ 1/4 total length = 1.6m (L)
Dragon Trunk = 37m^3 @ 3.6m (Dia) =  3.6m (L)
 
So Room to spare...

Cygnus SM = 1800kg, which is within the total payload of Dragon.

It could be simplified too:
just the main engine (no smaller thrusters)
No solar arrays

If you retain the communication equipment, it could operate independent on dragon so no interface issues across the sep plane...

And heritage should make approving it to operate it on the ISS simpler

Sent from my Pixel 5a using Tapatalk

At what point does a "heritage equipment" kludge become "rockets are not legos"?

Adapting heritage hardware takes engineering, just like building new hardware. No reasonable person would claim otherwise. That doesn't make it a kludge.

SpaceX and Northrop (and other aerospace companies) don't kludge. They don't play legos. They engineer.

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[AstroWare]

In the trunk is better because it doesn’t require modifying or interfacing with the cargo Dragon systems.

It could even be supplied by some other company, like NG.

The propulsion module of Cygnus looks like already fits..

Don't have a good source for the exact dimensions of the new dragon trunk, nor the service module section of Cygnus...

But from what I can find:
Cygnus = 6.4m (L) x 3.1m (Dia)
Cygnus SM ~ 1/4 total length = 1.6m (L)
Dragon Trunk = 37m^3 @ 3.6m (Dia) =  3.6m (L)
 
So Room to spare...

Cygnus SM = 1800kg, which is within the total payload of Dragon.

It could be simplified too:
just the main engine (no smaller thrusters)
No solar arrays

If you retain the communication equipment, it could operate independent on dragon so no interface issues across the sep plane...

And heritage should make approving it to operate it on the ISS simpler

Sent from my Pixel 5a using Tapatalk

why not just use cygnus then?

... It's going to take more than one spacecraft to maintain the ISS ... (!)

Progress vehicles provide reboosts/refuel currently at a rate of up to 4 per year. Haven't done the math to figure out the rate of Cygnus vehicles which would be needed. But the refueling module of progress carries 1700kg of prop. The whole SM of Cygnus wet is 1800kg. Logic would say that greater than 4 Cygnus SMs would therefore be needed per year for maintainable ISS orbit

Cygnus can only perform reboosts from Node1 Nadir. Dragon could then also perform reboosts from Node2 Forward.

This allows direct handover between missions. I.e. dragon takes over before Cygnus leaves. Then a new Cygnus takes over before dragon leaves.

It also adds redundancy in case a Cygnus (or dragon) is lost.

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[Asteroza]

In the trunk is better because it doesn’t require modifying or interfacing with the cargo Dragon systems.

It could even be supplied by some other company, like NG.

The propulsion module of Cygnus looks like already fits..

Don't have a good source for the exact dimensions of the new dragon trunk, nor the service module section of Cygnus...

But from what I can find:
Cygnus = 6.4m (L) x 3.1m (Dia)
Cygnus SM ~ 1/4 total length = 1.6m (L)
Dragon Trunk = 37m^3 @ 3.6m (Dia) =  3.6m (L)
 
So Room to spare...

Cygnus SM = 1800kg, which is within the total payload of Dragon.

It could be simplified too:
just the main engine (no smaller thrusters)
No solar arrays

If you retain the communication equipment, it could operate independent on dragon so no interface issues across the sep plane...

And heritage should make approving it to operate it on the ISS simpler

Sent from my Pixel 5a using Tapatalk

why not just use cygnus then?

... It's going to take more than one spacecraft to maintain the ISS ... (!)

Progress vehicles provide reboosts/refuel currently at a rate of up to 4 per year. Haven't done the math to figure out the rate of Cygnus vehicles which would be needed. But the refueling module of progress carries 1700kg of prop. The whole SM of Cygnus wet is 1800kg. Logic would say that greater than 4 Cygnus SMs would therefore be needed per year for maintainable ISS orbit

Cygnus can only perform reboosts from Node1 Nadir. Dragon could then also perform reboosts from Node2 Forward.

This allows direct handover between missions. I.e. dragon takes over before Cygnus leaves. Then a new Cygnus takes over before dragon leaves.

It also adds redundancy in case a Cygnus (or dragon) is lost.

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Note this is current 3 ring Cygnus. I think Jim was mentioning there's a 4 ring design to increase tankage. If Cygnus was being reevaluated for launch on Falcon 9, that may provide an opportunity for the 4 ring version to be built.

[AstroWare]

In the trunk is better because it doesn’t require modifying or interfacing with the cargo Dragon systems.

It could even be supplied by some other company, like NG.

The propulsion module of Cygnus looks like already fits..

Don't have a good source for the exact dimensions of the new dragon trunk, nor the service module section of Cygnus...

But from what I can find:
Cygnus = 6.4m (L) x 3.1m (Dia)
Cygnus SM ~ 1/4 total length = 1.6m (L)
Dragon Trunk = 37m^3 @ 3.6m (Dia) =  3.6m (L)
 
So Room to spare...

Cygnus SM = 1800kg, which is within the total payload of Dragon.

It could be simplified too:
just the main engine (no smaller thrusters)
No solar arrays

If you retain the communication equipment, it could operate independent on dragon so no interface issues across the sep plane...

And heritage should make approving it to operate it on the ISS simpler

Sent from my Pixel 5a using Tapatalk

why not just use cygnus then?

... It's going to take more than one spacecraft to maintain the ISS ... (!)

Progress vehicles provide reboosts/refuel currently at a rate of up to 4 per year. Haven't done the math to figure out the rate of Cygnus vehicles which would be needed. But the refueling module of progress carries 1700kg of prop. The whole SM of Cygnus wet is 1800kg. Logic would say that greater than 4 Cygnus SMs would therefore be needed per year for maintainable ISS orbit

Cygnus can only perform reboosts from Node1 Nadir. Dragon could then also perform reboosts from Node2 Forward.

This allows direct handover between missions. I.e. dragon takes over before Cygnus leaves. Then a new Cygnus takes over before dragon leaves.

It also adds redundancy in case a Cygnus (or dragon) is lost.

Sent from my Pixel 5a using Tapatalk

Note this is current 3 ring Cygnus. I think Jim was mentioning there's a 4 ring design to increase tankage. If Cygnus was being reevaluated for launch on Falcon 9, that may provide an opportunity for the 4 ring version to be built.

The service section (main engine and propellant tanks) is the same on the 3 ring and proposed 4 ring variants. So it doesn't really matter...

https://www.spaceflightinsider.com/missions/commercial/orbital-proposes-future-deep-space-applications-cygnus/

The undeveloped variant potentially applicable to this discussion is the version of cygnus with an unpressurized cargo section that carried extra tanks. Like ATV used to have. I don't remember if they were intended to just carry consumables like air and water, or if they could also hold propellant, but I think only the former. (There would have been no use for large propellant cargo deliveries for NASA...)



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[DreamyPickle]

The biggest obstacle to using Dragon is that thrusters are in the wrong position.

Is there any reason why SpaceX can't just mount a secondary set of thrusters on the trunk? A new set of fuel tanks can be added inside the trunk in order to avoid plumbing around the heat shield to get to internal fuel storage.

Yes, using Cygnus is probably easier. But modifying Dragon isn't actually difficult.

And having dissimilar redundancy for ISS reboost would be good.

[tyrred]

The biggest obstacle to using Dragon is that thrusters are in the wrong position.

Is there any reason why SpaceX can't just mount a secondary set of thrusters on the trunk? A new set of fuel tanks can be added inside the trunk in order to avoid plumbing around the heat shield to get to internal fuel storage.

Yes, using Cygnus is probably easier. But modifying Dragon isn't actually difficult.

And having dissimilar redundancy for ISS reboost would be good.

Time. How long do you think it would actually take to kludge together what you are proposing?

Every time I see someone talking about adding propellant and thrusters to Dragon trunk, it makes me think of just adding another engine and transmission to a car's trunk... And then getting it certified to be highway operable.

Not trying to rain on your parade, but it's just not happening.

[John Santos]

The biggest obstacle to using Dragon is that thrusters are in the wrong position.

Is there any reason why SpaceX can't just mount a secondary set of thrusters on the trunk? A new set of fuel tanks can be added inside the trunk in order to avoid plumbing around the heat shield to get to internal fuel storage.

Yes, using Cygnus is probably easier. But modifying Dragon isn't actually difficult.

And having dissimilar redundancy for ISS reboost would be good.

I think it is just a matter of money.  Lots of money.  It's almost like developing a new rocket stage.  Integrating tanks, pipes and engines isn't trivial.  Modifying the guidance and control software is probably also non-trivial.  The trunk might need some structural reinforcement, but if the use Dracos (which are low thrust and already in use on Dragon), the forces won't be excessive.  At least, using existing engines should be easier then starting entirely from scratch.  They would certainly want to test the system in space before using it while attached to the ISS.  I wonder if they could launch a cargo Dragon with it in the trunk, leave it inert until after the Dragon departs, then test it before discarding the trunk and re-entry?  Or maybe they would need a dedicated, non-ISS test flight?

I think a Dragon (or other vehicle) docked to PMA2 with aft pointing thrusters  would be better for orbital boosts than a craft docked to one of the nadir CBMs, but perhaps not for desaturating the CMGs.  They would have to pitch or yaw the entire station 180 degrees to boost because the forward port is pointing the wrong way, but they've done that in the past (accidentally when Nauka docked!)

They really need more docking ports if they want to keep a Dragon or other vehicle more or less permanently docked for re-boosts and collision avoidance, though.  Would the Axiom modules solve this problem?

[Jim]

I think a Dragon (or other vehicle) docked to PMA2 with aft pointing thrusters

Those already exist, it is called Cygnus or MEV

[nacnud]

Seeing as everyone is scraping the barrel with wacky ideas (and Jim has had to resort to answering in nearly full sentences) has anyone brought up the VASIMR test that was supped to be conducted on the ISS.

It's probably not enough to take over reboost completely but perhaps it could help stop the ISS falling quite so fast. I've no idea how far along they were with flight hardware.

Ok back to doomscrolling twitter

[DanClemmensen]

I think a Dragon (or other vehicle) docked to PMA2 with aft pointing thrusters

Those already exist, it is called Cygnus or MEV

Cygnus already exists. If it is possible to use an unmodfied Cygnus, then simply expending several of them will be cheaper than attempting to kludge up some alternative. This raises three questions:
--Can an unmodified Cygnus do a useful reboost of ISS?
--How many unmodified Cygni (Cygnuses, whatever) will be needed?
--How can these Cygni be launched?

There are two remaining Anteries LVs. If the two cargo missions cannot be combined with reboost, then NASA could choose to use Cargo Dragon for the cargo missions and free up the Cygnus missions for reboost, but NG will need an alternative LV by next year in any event if Cygnus is to continue flying.

If ISS somehow morphs into a successor station that includes ISS pieces, then presumably some rebooster architecture will be included. What year will this happen in, if at all? The expended Cygni reboosters would be needed until then.

[DreamyPickle]

It's true that Cygnus is an easier option. The biggest obstacle is Antares running out of engines but launching on Falcon 9 would be a very easy fix.

However this is a SpaceX thread in the SpaceX section so it should be more about how SpaceX could solve this problem.

Adding Dracos to the trunk might take many months but probably not years.

* It's a simple pressure-fed thruster
* It doesn't even need to be integrated with the rest of the Dragon attitude control system. Unless it's reboosting the ISS it can be treated as "cargo".
* Mass isn't much of a concern either, I remember Dragon Cargo being volume limited.
* SpaceX is working on Dragon XL anyway so these systems are not being obsoleted.

One difficulty would be integrating this reboost system with the rest of the ISS but that shouldn't be much different from what it would take to use Cygnus.

They might consider using something derived from Starlink but the additional efficiency is not required and continuous low thrust might required additional adaptation from the ISS side.

[nacnud]

There are 9 project kuiper Atlas 9 launches scheduled, and two more Anteries. If they can build a flock of cygnusses fast enough that gives a few years to get Vulcan up and running so long as NASA doesn't mind annoying compensating Amazon.

There is also time for Ariane 6 or Falcon 9 to get involved.

Long pole is cygnus production rate?

[DanClemmensen]

Seeing as everyone is scraping the barrel with wacky ideas  [...]

OK truly wacky time. What about Orion? It surely has the propellant and the docking capability, but it may not have the ability to use a low enough thrust.  It's horrifically expensive, but it exists and is supposed to be in series production. It would likely get (ahem) congressional approval as an emergency measure.

[DanClemmensen]

There are 9 project kuiper Atlas 9 launches scheduled, and two more Anteries. If they can build a flock of cygnusses fast enough that gives a few years to get Vulcan up and running so long as NASA doesn't mind annoying compensating Amazon.

There is also time for Ariane 6 or Falcon 9 to get involved.

Long pole is cygnus production rate?

NG has been producing and flying two Cygnus missions per year, so if two reboosts suffice, there will be enough Cygni. If reboosts cannot also serve as cargo missions, NASA can back-fill the cargo missions using Crew Dragon (obligatory SpaceX reference since this is a SpaceX thread). NG will need a new LV after the two remaining Antares in any event and they might choose to use F9 (second obligatory SpaceX ref).

[russianhalo117]

The biggest obstacle to using Dragon is that thrusters are in the wrong position.

Is there any reason why SpaceX can't just mount a secondary set of thrusters on the trunk? A new set of fuel tanks can be added inside the trunk in order to avoid plumbing around the heat shield to get to internal fuel storage.

Yes, using Cygnus is probably easier. But modifying Dragon isn't actually difficult.

And having dissimilar redundancy for ISS reboost would be good.

Dragon-XL has thruster pods on end you want that are identical Dracos to the 4 Dracos on the docking port side. Four of them (one on each pod) are pointing in the  correct direction for attitude control and re-boosts.

[captainoverboard]

I haven't seen this in the thread, so apologies if it's already in there.

https://www.nasa.gov/feature/glenn/2021/we-are-fired-up-gateway-propulsion-system-passes-first-test

It's already supposed to launch on spacex.

It's already even tested.

I realize it might not have enough thrust all the time, but perhaps it could help reduce reboost times

[alugobi]

This section of the forum needs a new subforum for all the fan mods that are popping up all the time, here and in the Starship subforum. 

Call it Ricer SX or something.

[Lee Jay]

There are 9 project kuiper Atlas 9 launches scheduled, and two more Anteries. If they can build a flock of cygnusses fast enough that gives a few years to get Vulcan up and running so long as NASA doesn't mind annoying compensating Amazon.

There is also time for Ariane 6 or Falcon 9 to get involved.

Long pole is cygnus production rate?

NG has been producing and flying two Cygnus missions per year, so if two reboosts suffice, there will be enough Cygni.

How does that solve this problem?

https://forum.nasaspaceflight.com/index.php?topic=55890.msg2345743#msg2345743

[Nomadd]

I haven't seen this in the thread, so apologies if it's already in there.

https://www.nasa.gov/feature/glenn/2021/we-are-fired-up-gateway-propulsion-system-passes-first-test

It's already supposed to launch on spacex.

It's already even tested.

I realize it might not have enough thrust all the time, but perhaps it could help reduce reboost times

I kind of wondered about that. They should have quite a bit of surplus power if they're not delivering it to the Russian side anymore.
 Somewhere, years ago, someone came up with a number for constant station keeping thrust. I think I used 24kw/Newton as a base number to figure electrical, but can't find it now.

 They could always install about 1200 Starlink thrusters over the entire station.

[nacnud]

There are 9 project kuiper Atlas 9 launches scheduled, and two more Anteries. If they can build a flock of cygnusses fast enough that gives a few years to get Vulcan up and running so long as NASA doesn't mind annoying compensating Amazon.

There is also time for Ariane 6 or Falcon 9 to get involved.

Long pole is cygnus production rate?

NG has been producing and flying two Cygnus missions per year, so if two reboosts suffice, there will be enough Cygni.

How does that solve this problem?

https://forum.nasaspaceflight.com/index.php?topic=55890.msg2345743#msg2345743

Desaturation can be done via careful orientation of the ISS against the drag of the atmosphere. I can't find specific details though.

Edit, I found a paper! Its actually done via the gravity gradient though I'm sure atmosphere drag and light pressure would have some effect though I'm not sure if it would be large enough to be useful.

ZERO PROPELLANT MANEUVERTM FLIGHT RESULTS FOR 180° ISS ROTATION

[DanClemmensen]

There are 9 project kuiper Atlas 9 launches scheduled, and two more Anteries. If they can build a flock of cygnusses fast enough that gives a few years to get Vulcan up and running so long as NASA doesn't mind annoying compensating Amazon.

There is also time for Ariane 6 or Falcon 9 to get involved.

Long pole is cygnus production rate?

NG has been producing and flying two Cygnus missions per year, so if two reboosts suffice, there will be enough Cygni.

How does that solve this problem?

https://forum.nasaspaceflight.com/index.php?topic=55890.msg2345743#msg2345743

I was responding only to "If they can build a flock of cygnusses fast enough" and "Long pole is cygnus production rate?" in the message I quoted. I cannot solve all the world's problems 

[Lee Jay]

I haven't seen this in the thread, so apologies if it's already in there.

https://www.nasa.gov/feature/glenn/2021/we-are-fired-up-gateway-propulsion-system-passes-first-test

It's already supposed to launch on spacex.

It's already even tested.

I realize it might not have enough thrust all the time, but perhaps it could help reduce reboost times

I kind of wondered about that. They should have quite a bit of surplus power if they're not delivering it to the Russian side anymore.
 Somewhere, years ago, someone came up with a number for constant station keeping thrust.

I don't know if that was me, but I did do it once and, while it's quite variable, it was on the order of 1 Newton.

[Nomadd]

I haven't seen this in the thread, so apologies if it's already in there.

https://www.nasa.gov/feature/glenn/2021/we-are-fired-up-gateway-propulsion-system-passes-first-test

It's already supposed to launch on spacex.

It's already even tested.

I realize it might not have enough thrust all the time, but perhaps it could help reduce reboost times

I kind of wondered about that. They should have quite a bit of surplus power if they're not delivering it to the Russian side anymore.
 Somewhere, years ago, someone came up with a number for constant station keeping thrust.

I don't know if that was me, but I did do it once and, while it's quite variable, it was on the order of 1 Newton.

If they did go with constant thrust ion, I assume it would get parked as high up as practical. It seems like an advantage of barely counteracting drag would be better perfect zero g sweet spots.

[AS_501]

If the Russians leave the ISS, the station's operating altitude no longer has to be accessible to Soyuz.  As such, could it be re-boosted to a higher altitude that can still be reached by Dragon, Starliner, Dreamchaser, etc.?  Higher altitude translates into fewer re-boosts.  All this assumes Soyuz cannot reach orbits as high as the other vehicles.

?
Thx

[JayWee]

If the Russians leave the ISS, the station's operating altitude no longer has to be accessible to Soyuz.  As such, could it be re-boosted to a higher altitude that can still be reached by Dragon, Starliner, Dreamchaser, etc.?  Higher altitude translates into fewer re-boosts.  All this assumes Soyuz cannot reach orbits as high as the other vehicles.

?
Thx

We know that Dragon2 can go much higher. How do Starliner and Cygnus fare in this regard?

[russianhalo117]

If the Russians leave the ISS, the station's operating altitude no longer has to be accessible to Soyuz.  As such, could it be re-boosted to a higher altitude that can still be reached by Dragon, Starliner, Dreamchaser, etc.?  Higher altitude translates into fewer re-boosts.  All this assumes Soyuz cannot reach orbits as high as the other vehicles.

?
Thx

The switch Soyuz-2.1B negates this to a point. Soyuz-2.1B allows Soyuz MS-M/Progress MS-M to reach ROSS in ~SSO insertion orbit from Vostochny.

[russianhalo117]

If the Russians leave the ISS, the station's operating altitude no longer has to be accessible to Soyuz.  As such, could it be re-boosted to a higher altitude that can still be reached by Dragon, Starliner, Dreamchaser, etc.?  Higher altitude translates into fewer re-boosts.  All this assumes Soyuz cannot reach orbits as high as the other vehicles.

?
Thx

We know that Dragon2 can go much higher. How do Starliner and Cygnus fare in this regard?

Cygnus sometimes raises its orbit significantly after ISS separation to deploy its external payloads.

[Lee Jay]

Could mag bars like on Hubble do desat on ISS or is it too big and/or is the rotation of the station a problem?

[Jim]

Could mag bars like on Hubble do desat on ISS or is it too big and/or is the rotation of the station a problem?

Too big and drag is an issue

[Asteroza]

I haven't seen this in the thread, so apologies if it's already in there.

https://www.nasa.gov/feature/glenn/2021/we-are-fired-up-gateway-propulsion-system-passes-first-test

It's already supposed to launch on spacex.

It's already even tested.

I realize it might not have enough thrust all the time, but perhaps it could help reduce reboost times

I kind of wondered about that. They should have quite a bit of surplus power if they're not delivering it to the Russian side anymore.
 Somewhere, years ago, someone came up with a number for constant station keeping thrust.

I don't know if that was me, but I did do it once and, while it's quite variable, it was on the order of 1 Newton.

If they did go with constant thrust ion, I assume it would get parked as high up as practical. It seems like an advantage of barely counteracting drag would be better perfect zero g sweet spots.

Slight segue, but here's Jim ripping into that...

By now boost servicing shouldn't even be necessary.  The station should have been outfitted with electric thrusters and requisite power sources ages ago.

Wrong for many reasons.
A.  The existing thrusters would still be needed for CMG desat
B.  Electric thrusters still need propellant servicing
C.  Electric thrusters would ruin the micro gravity environment negating the major reason the ISS exists
D.  power sources were not available ages ago
E.  Electric thrusters can't make collision avoidance maneuvers

Meanwhile the Chinese station has electric propulsion systems flying and operational.

a meaningless point.  The above points still apply.

There is an argument to be made that despite having a variable drag profile, having only periodic and well defined reboosts allows for correcting experimental error in microgravity experiments in theory. Qualitatively though, ISS experiences variable atmospheric drag, thus non-zero-g all the time, so how is that being recorded for experiment filtering?

How would that be functionally different from an electric thruster firing at 1 newton all the time through the ISS CoG for drag counteraction? I suppose pure air drag deviations means the error direction is one way, rather than a constant reboost thruster that can be both stronger and weaker than instantaneous air drag, meaning the direction of error goes both ways. But if the raw goal is extreme microgravity generally, wouldn't running a constant reboost thruster quantitatively get you closer to that goal?

[Barley]

The biggest obstacle to using Dragon is that thrusters are in the wrong position.

Could somebody explain this.

For any boost the thrust vector should go through the center of mass of the station.

The Nader and Forward docking ports are at right angles.  The direction of thrust relative to the docked vehicle will also be at a large angle (somewhere between 45 and 90 degrees depending on the exact location of the station CoM).  Therefore at least one of these ports you do not need, and may not be able to use, aft pointing thrusters.  In other words, at one of these ports you need to boost sideways.  Yet it appears that the conventional wisdom is that the thrust direction (relative to the docked vehicle) is the same at all ports.

Alternatively, if the docking ports can only handle axial thrust, how do you boost using the Nader and Zenith ports?

[AS_501]

The biggest obstacle to using Dragon is that thrusters are in the wrong position.

Could somebody explain this.

For any boost the thrust vector should go through the center of mass of the station.

The Nader and Forward docking ports are at right angles.  The direction of thrust relative to the docked vehicle will also be at a large angle (somewhere between 45 and 90 degrees depending on the exact location of the station CoM).  Therefore at least one of these ports you do not need, and may not be able to use, aft pointing thrusters.  In other words, at one of these ports you need to boost sideways.  Yet it appears that the conventional wisdom is that the thrust direction (relative to the docked vehicle) is the same at all ports.

Alternatively, if the docking ports can only handle axial thrust, how do you boost using the Nader and Zenith ports?

Barley:  It may have to do with how the station is oriented relative to its velocity vector.  (I was wondering something similar with the docking of Nauka.  I thought the Russian module would dock at right angles to the VV.  Instead, the entire station was rotated 90 deg. so that Nauka docked along the VV.)  I defer to one of our celestial mechanics on your question.

[Jim]

The biggest obstacle to using Dragon is that thrusters are in the wrong position.

Could somebody explain this.

For any boost the thrust vector should go through the center of mass of the station.

The thrusters for deorbit and primary axial are forward facing.

[vp.]

The plan is to launch the Axiom modules in 2024 to attach them to the ISS. Then the Axiom modules will become an autonomous station.
Therefore, the solution to replace the Russian modules is Axiom.
Well, maybe NASA needs to help accelerate this program.

[Comga]

By now boost servicing shouldn't even be necessary.  The station should have been outfitted with electric thrusters and requisite power sources ages ago.

Wrong for many reasons.
A.  The existing thrusters would still be needed for CMG desat
B.  Electric thrusters still need propellant servicing
C.  Electric thrusters would ruin the micro gravity environment negating the major reason the ISS exists
D.  power sources were not available ages ago
E.  Electric thrusters can't make collision avoidance maneuvers

Rather than poking the bear by responding “Wrong” each of these points can be discussed.

A. CMG desat can be done without thrusters if planned in advance.
Other thrusters could be used.

B. With their order-of-magnitude higher Isp, electric thrusters can get by with an order of magnitude less propellant. However, systems for refueling them are not developed, so the systems might be disposable.

C. Drag compensation would improve the microgravity. Electric thrusters could be modulated to compensate for variations in exoatmospheric density and drag.

D. History says how we got here, but it’s still history. That said, whether there is sufficient electric power available for routine drag compensation is a good question.

E. Not wrong 😊 For example the MEV has what, 0.4 N thrust?  However emergency collision avoidance can be done by thrusting in directions other than prograde with systems not mounted in the rear. It would just not accomplish the dual purpose of reboosting at the same time.

[Lee Jay]

B. With their order-of-magnitude higher Isp, electric thrusters can get by with an order of magnitude less propellant. However, systems for refueling them are not developed, so the systems might be disposable.

I'm dropping way back into my memory now, but I thought ISS produced an excess of hydrogen as a result of the ECLSS.  That hydrogen, if memory serves, is currently dumped overboard using a zero thrust port of some sort.  While hydrogen is far from ideal as an ion thruster propellant, maybe that hydrogen stream could be diverted for that purpose simply because it's available "for free"?

[Comga]

The biggest obstacle to using Dragon is that thrusters are in the wrong position.

Could somebody explain this?

For any boost the thrust vector should go through the center of mass of the station.

The thrusters for deorbit and primary axial are forward facing.

But what about the non-primary axial thrusters in the sidewalls?
If the station was turned around, those would fire away from the ISS while suffering some cosine loss, probably around 40% in terms of propellant usage.
However, with the shared, unexpended abort propellant in a Dragon 2, crew or cargo, there should still be enough for months of reboosting.
(This can be calculated by someone who has more information than I do. Anyone volunteering?)

This thread is predicated on an emergency condition. 
Systems that will be available a year or more from now are not applicable to the question of the survival of the ISS.
Systems, including having available launchers, that are less than optimal, are what you go with in an emergency.

[Asteroza]

B. With their order-of-magnitude higher Isp, electric thrusters can get by with an order of magnitude less propellant. However, systems for refueling them are not developed, so the systems might be disposable.

I'm dropping way back into my memory now, but I thought ISS produced an excess of hydrogen as a result of the ECLSS.  That hydrogen, if memory serves, is currently dumped overboard using a zero thrust port of some sort.  While hydrogen is far from ideal as an ion thruster propellant, maybe that hydrogen stream could be diverted for that purpose simply because it's available "for free"?

one of the early plans for the ISS VASIMR demo was planning on using that hydrogen, but for some reason the VASIMR was going to be pointed sideways, thus being poorly positioned for continuous reboost (but the demo was power constrained, using burst power from an accumulator battery pack, so I guess doesn't qualify as continuous...)

[Asteroza]

It's a shame that some of the ideas around electric thrusters on a pallet held by the existing robot arm aren't applicable here, as the thrust load is small and the arm could adjust the thrust direction for CoG matching. It seems to me that the big issue would be supplying power via a cable, as the arm itself probably can't supply enough natively.