SpaceX and Replacement of Russian module services on the ISS

[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.