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

[Vettedrmr]

With Soyuz grounded for the foreseeable future, how much slack can SpaceX pick up with cargo Dragon?

[spacenut]

There is still Northrop Grumman who can deliver cargo.  There is also Boeing Starliner that can be stripped out to deliver cargo.  If necessary Space X can launch another's cargo with a F9.  Dragon can probably take up the slack by reuse of a Dragon capsule multiple times. 

[DanClemmensen]

With Soyuz grounded for the foreseeable future, how much slack can SpaceX pick up with cargo Dragon?

I don't know. There are 3 cargo dragons, and they have flown 13 times in the last 72 months. We know NASA intends to stretch the CCP missions, so the SpaceX Dragon refurbishment crews may have some slack. However, if they must continue to provide reboost, they will need longer time in orbit, which in theory reduces the time available for refurbishment.

Starliner is a complication. If it flies crew, the Dragon refurbishment team will have even more slack.

You might want to also ask about Cygnus, especially since they now have the new bigger XL version. Also the JAXA HTV.

[Comga]

It’s not a question of “surging” cargo missions
It is a question of ISS orbit maintenance.
If the Russians can’t reestablish Soyuz launch before their fuel on orbit runs out (How long will that be?) then Dragon (or Cygnus) would have to step in.

At what pace can SpaceX launch Dragons, crew and cargo?
If it’s, say, 4 per year, can the Boost Kit cover, or be expanded to cover, 3 months of reboosting?

At the current density altitude that’s very close to 10 km per quarter or ~3.3 m/sec delta-V.
For a 4,200 ton ISS, that’s ~3400 seconds of 400 N Draco firing time.
With an Isp of 234 sec, where it burns ~0.78 kg/sec/Draco, that’s ~2,650 kg.
Can the Boost Kit carry, or be expanded to carry, that much propellent?
Will that kill the cargo capacity?
Would that be allowed with astronauts?

[zubenelgenubi]

Cross-post; discuss here:

I'm really glad that Dragon has demonstrated the ability to reboost ISS.

Cygnus too.

We know a Dragon at Harmony forward can apply axial force for reboost. I'm less certain about CMG desaturation, which requires applying the right kind of angular acceleration. Does anyone here know? My crude mental model says that a Dragon at harmony zenith can do it if ISS is oriented properly, but I do not trust my mental model.

I suspect NASA will be doing some mathematical modeling very quickly to see what is possible.

I suspect such contingency plans already exist.

[Vettedrmr]

Starliner is a complication. If it flies crew, the Dragon refurbishment team will have even more slack.

I didn't consider Starliner because, IMO, it's still in development, and we don't know when it'll fly next.  And then you'd only want non-essential cargo on that first flight, in case it's not cleared for docking.

You might want to also ask about Cygnus, especially since they now have the new bigger XL version. Also the JAXA HTV.

I didn't consider those because, due to their expendable nature, I assumed that their production would be geared towards their defined schedules.  AFAIK, SpaceX is the only supplier with "surplus" vehicles that could replace Progress in the resupply schedule.  Cygnus can launch on an F9, but HTV can only launch on a JAXA launch vehicle (I think), and again, IDK where those vehicles are in their production cycle.

[Vettedrmr]

It’s not a question of “surging” cargo missions
It is a question of ISS orbit maintenance.
If the Russians can’t reestablish Soyuz launch before their fuel on orbit runs out (How long will that be?) then Dragon (or Cygnus) would have to step in.

At what pace can SpaceX launch Dragons, crew and cargo?
If it’s, say, 4 per year, can the Boost Kit cover, or be expanded to cover, 3 months of reboosting?

At the current density altitude that’s very close to 10 km per quarter or ~3.3 m/sec delta-V.
For a 4,200 ton ISS, that’s ~3400 seconds of 400 N Draco firing time.
With an Isp of 234 sec, where it burns ~0.78 kg/sec/Draco, that’s ~2,650 kg.
Can the Boost Kit carry, or be expanded to carry, that much propellent?
Will that kill the cargo capacity?
Would that be allowed with astronauts?

I think there's a Progress mission that is scheduled for December; to meet that schedule by a cargo Dragon I'd call it a surge.  And I absolutely agree that, probably the key part, is ISS orbit maintenance.  With Progress out of the loop, it's going to fall to SpaceX and Cygnus to do that job for the foreseeable future.

[DanClemmensen]

In addition to Cargo Dragon, we also have spare upmass capacity on Crew Dragon that might be usable. We know this because Crew Dragon usually flies with a booster RTLS. The problem here is that CRS missions must also take out the trash and dispose of it. I don't know what the logistics would look like to put the trash in some sort of container or net, put it out an airlock, and secure it inside the Dragon's trunk for disposal.

[Comga]

Not Dragon but….

This is where Boeing and Starliner could shine as a cargo vehicle beyond the next flight.  Probably not, but it's good PR potential for them.

I posted above some calculation results for reboosting the ISS with Boost Kits in Dragon Trunks

While Starliner has many sub-optimal characteristics for the ISS cargo role, and we don’t need to rehash the Boeing development fiasco (Please don’t!), it may be adaptable and advantageous for the reboost role.
Its disposable OMAC LES engines are pointed axially.
There are six Atlas V rockets reserved for it.
There are six Service Modules waiting.
As originally planned, it would be “Dissimilar Redundancy” for Dragon reboosting, and could be used in addition to them.

Can someone please post the total impulse of Starliner’s LES (in Newton-Seconds)?
Edit 2 with frame counting of the pad abort: 4.24E+6 N-sec over 5.30 seconds

Can someone compare the thrust of an OMAC engine to the Progress or Zvezda engine groups?
Zvezda’s 2 S5.79 engines generate 3.09 kN each
Starliner’s 4 OMAC engines generate 1.5 kN each
So 3% less in total theoretically, essentially equal

We could then calculate how long each Starliner flight could cover the reboosting role.
Edit calculated with above value for 420 ton ISS:
49 days of reboosting, not very much

[Jim]

roll control is the issue and not reboost

[russianhalo117]

Soyuz and Progress's KD engine is an S5.92 model.

Zvezda
The Zvezda service module's KD engines (equivalent to TKS modules DKS engines) are two orbit-correction engines (designated S5.79) used for orbital maneuvering and attitude control, along with 32 smaller thrusters (DMT, designated 11D428A-10). The KD engines provide a thrust of 300 kilograms each and are part of the module's integrated propulsion system.

KD engines: These are the primary engines for orbital corrections and maneuvering. There are two KD engines, also designated S5.79. They have a thrust of 300 kilograms each.

DMT thrusters: In addition to the KD engines, the Zvezda module uses 32 smaller reaction control thrusters (DMT) for attitude control, yaw, and roll movements. These thrusters are designated 11D428A-10. Each has a thrust of 12.5 kilograms.
The TKS module family's DU propulsion system has a pair of KRD-442 (11D442) main orbit-correction engines, DKS, developed at the Isaev KBKhM design bureau in Korolev. They are also known as DKS-1 and DKS-2. Each engine produces 417 kilograms of thrust. In addition there are 32 smaller thrusters, (DPS (11D458) and DTS (17D58E)) and, specific to Nauka, 12 MDDK thrusters (S5.144 originating from the Ikar upper stage) with a thrust of 300 kilograms. Note that the DKS, DPS, and DTS and inhibited on Nauka and Zarya.

Manufacturer:
https://en.wikipedia.org/wiki/A.M._Isayev_Chemical_Engineering_Design_Bureau

[sdsds]

Is the prop load on a crew dragon sized for an ascent abort? If so, is there "excess" propulsion for ISS reboost available once the crew dragon is at e.g. Harmony FWD?

[DanClemmensen]

Is the prop load on a crew dragon sized for an ascent abort? If so, is there "excess" propulsion for ISS reboost available once the crew dragon is at e.g. Harmony FWD?

I don't know. but here's a related question. I think the Crew Dragon trunk is usually empty. Would NASA certify the boost kit to be used on a Crew Dragon? It is already having its "uncrewed demo" on CRS-33.

One big problem with Progress replacement it that Progress apparently carries propellant for the Russian RCS thrusters on the station that were supposed to handle attitude control and CMG desaturation, for normal operation and eventually for de-orbit.  But I cannot find the references for this so maybe I'm wrong.

[russianhalo117]

Is the prop load on a crew dragon sized for an ascent abort? If so, is there "excess" propulsion for ISS reboost available once the crew dragon is at e.g. Harmony FWD?

Yes the entire onboard prop load is depleted for a pad/ascent abort/emergency deorbit (when primary thrusters are unavailable or fail/timer deorbit for abandoned vehicle reentry)/and non parachute contingency mode splashdown. The same prop load is used for mission flight operations when there is a nominal launch.

[russianhalo117]

Is the prop load on a crew dragon sized for an ascent abort? If so, is there "excess" propulsion for ISS reboost available once the crew dragon is at e.g. Harmony FWD?

I don't know. but here's a related question. I think the Crew Dragon trunk is usually empty. Would NASA certify the boost kit to be used on a Crew Dragon? It is already having its "uncrewed demo" on CRS-33.

One big problem with Progress replacement it that Progress apparently carries propellant for the Russian RCS thrusters on the station that were supposed to handle attitude control and CMG desaturation, for normal operation and eventually for de-orbit.  But I cannot find the references for this so maybe I'm wrong.

It would require certification and would change the flight profile to account for the additional mass plus changed abort mode escape conditions from the additional mass.

[sdsds]

[...] I think the Crew Dragon trunk is usually empty. Would NASA certify the boost kit to be used on a Crew Dragon?

I think during an ascent abort Crew Dragon takes the trunk along for the ride, maybe for aerodynamic reasons. So the added mass of boost kit propellant counts against the total allowable mass of Dragon in the abort scenario. (Unless somehow the boost kit were tied into the abort mode logic so its thrusters could help Dragon get away from the launch vehicle. I'm sure they could introduce that change without inadvertently adding any other new behavior, but....)

[Comga]

[...] I think the Crew Dragon trunk is usually empty. Would NASA certify the boost kit to be used on a Crew Dragon?

I think during an ascent abort Crew Dragon takes the trunk along for the ride, maybe for aerodynamic reasons. So the added mass of boost kit propellant counts against the total allowable mass of Dragon in the abort scenario. (Unless somehow the boost kit were tied into the abort mode logic so its thrusters could help Dragon get away from the launch vehicle. I'm sure they could introduce that change without inadvertently adding any other new behavior, but....)

The Trunk carries the conformal solar arrays and Dragon’s thermal radiator.

Burning the abort propellents with the Boost Kit would require plumbing them through the actuated “Claw” that reaches around Dragon’s heat shield to carry the coolant and electrical power to and from the Trunk.  This would be difficult, to say the least, as it was sized for its current role.

Edit: I misread the quoted post
sdsds wants to use the Boost Pack to aid the LES to compensate for its added mass, not burn the abort propellants on orbit. “Never mind!”
But the first part stands.

[DanClemmensen]

[...] I think the Crew Dragon trunk is usually empty. Would NASA certify the boost kit to be used on a Crew Dragon?

I think during an ascent abort Crew Dragon takes the trunk along for the ride, maybe for aerodynamic reasons. So the added mass of boost kit propellant counts against the total allowable mass of Dragon in the abort scenario. (Unless somehow the boost kit were tied into the abort mode logic so its thrusters could help Dragon get away from the launch vehicle. I'm sure they could introduce that change without inadvertently adding any other new behavior, but....)

The Trunk carries the conformal solar arrays and Dragon’s thermal radiator.

Burning the abort propellants with the Boost Kit would require plumbing them through the actuated “Claw” that reaches around Dragon’s heat shield to carry the coolant and electrical power to and from the Trunk.  This would be difficult, to say the least, as it was sized for its current role.

Don't burn the abort props. Just use the boost kit. The boost kit on CRS-33 is apparently modular and there is room for additional propellant tanks.

[Comga]

roll control is the issue and not reboost

The OP discussed cargo in the absence of Progress
My concern was boosting for maintaining the orbit.
Jim argues that the main issue is roll


AFAIK the only “cargo” on Progress of concern to the USOS is propellant.
Without Soyuz, no cosmonauts are going to the ISS. 
Russia isn’t going to buy seats on Dragon, and probably can’t because of sanctions, and have nothing to trade for them. 
Without cosmonauts there is no need for cargo on their side.

Both Dragon and Starliner have engines pointed sideways for wheel desaturation.
Also the USOS has demonstrated “Zero Net Momentum” attitude control, so desaturation shouldn’t be needed (very much)
So I don’t know why Jim says that.

I still believe reboosting is the biggest challenge without Progress.
And neither Dragon with the demonstrated Boost Kit or Starliner with its Service Module LES has enough impulse.

[Helodriver]

Absence of Progress and its fuel seems to be a more pressing issue than crew rotation. F9 could easily fit a fully loaded Progress in its fairing. The problems to adapt it for US launch would seem to be more political than technical. More likely though if the service platform cannot be fixed easily, Progress flies from the Soyuz carrier rocket pads at Plesetsk or Vostochny with GSE modifications. Crew Soyuz waits until the 31/6 pad is repaired.