SpaceX and Replacement of Russian module services on the ISS

[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?