SpaceX and Replacement of Russian module services on the ISS

[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

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[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.

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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.

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.