SpaceX - US Deorbit Vehicle (for ISS)

[ChrisC]

Looking at an Axiom animation of their assembly sequence today, I realized something that hasn't been discussed anywhere and none of the reporters asked about it in the press conference last week: the Axiom station and this new DV are both planning to use the front docking port.

If the DV is going up 18 months before the deorbit, that implies that all of the Axiom modules need to be launched and assembled and then the entire new Axiom station needs to detach from ISS before that launch.  The first module is currently planned to go up in late 2026, but most of that hardware is planned for "late 2020s". That compresses the Axiom timeline, or at least removes 18 months of wiggle room.  Am I missing something?

(There are some recent videos in the Axiom thread, including an interview with Suffredini 10 days ago, and I'll catch up on those tomorrow and see if this topic comes up.)

[woods170]

Looking at an Axiom animation of their assembly sequence today, I realized something that hasn't been discussed anywhere and none of the reporters asked about it in the press conference last week: the Axiom station and this new DV are both planning to use the front docking port.

If the DV is going up 18 months before the deorbit, that implies that all of the Axiom modules need to be launched and assembled and then the entire new Axiom station needs to detach from ISS before that launch.  The first module is currently planned to go up in late 2026, but most of that hardware is planned for "late 2020s". That compresses the Axiom timeline, or at least removes 18 months of wiggle room.  Am I missing something?

(There are some recent videos in the Axiom thread, including an interview with Suffredini 10 days ago, and I'll catch up on those tomorrow and see if this topic comes up.)

Emphasis mine.

You're not missing anything. Axiom is aware of the constraints. So are NASA and SpaceX. Good thing to keep in mind is this: the PMA and IDA now sitting at the "front" end of ISS, will be relocated to an available CBM on the nadir side of USOS, before the first Axiom module is attached. Both PMA-IDA combinations remain available for docking after Axiom starts its build-up, because crew rotation and cargo delivery requirements require the availability of at least two NDS ports. Docking to the Axiom segments becomes possible only after the second Axiom module is delivered-and-berthed to the first one.

After the Axiom orbital segment is detached, the PMA-IDA has to be moved back to the "front" end of the ISS. As with any relocation of the PMA-IDA combination, that requires the assistance of one-or-more EVAs. Meaning that crew still has to be present on the ISS. Only after the PMA-IDA is back on the "front" end of the ISS, can the USDV perform its final docking to the ISS.

[woods170]

Attitude control during the deorbit burns is done solely by the 32 attitude control Dracos (16 on the capsule and 16 on the deorbit section).

Meaning the Russian segment thrusters and ISS CMG's are not used

The control logics of the Russian segment thrusters and the USOS CMGs are NOT coupled to the control logic of the USDV. This could have the unwanted effect of counter-acting the USDV attitude control system if the RS thrusters and/or the USOS CMGs were to be active during the deorbit burns.

Unlike MIR, the ISS can't enter a slow-spin for stabilisation purposes. Due to the massive truss and its flimsy solar arrays, the rotation velocity of ISS in any direction is much more limited than it was for MIR.

[StraumliBlight]

SpaceX just stomped the competition for a new contract—that’s not great

Here's where all of this leaves NASA. The agency would like to move toward an era of commercial space, in which the agency shares development costs with the private industry and benefits from the ideas and nimble development practices of entrepreneurs. Everyone wins.

However, the space agency has encountered serious turbulence in this endeavor.

Based on the experiences of Commercial Crew and now the US Deorbit Vehicle, on a level playing field, it is clear that traditional space providers such as Boeing and Northrop struggle to compete with SpaceX on price and performance.

But so do newer entrants. For some time, the agency has been hoping that other new space companies would step up and similarly thrive like SpaceX in an environment of purely fixed-price contracts. To succeed over the coming decade in low-Earth orbit and on the Moon, the agency is counting on a new generation of companies, such as Axiom Space and Intuitive Machines, to take this next step. But what happens if they don't?