A Deep Dive on How to Save the ISS

That's this morning's post from Eric Berger at Ars Technica, reprising what we all talked about last week.  In the big picture sense, it's not as completely done as I thought last week, but it's not desperately different, either.  It needs some attention to detail that all seems to be achievable.  

To begin with, last Wednesday my summary was:

Consequently, we have three options that are capable of maintaining the ISS in its desired orbit: Cygnus, Cargo Dragon and Crew Dragon. 

Of these, the two SpaceX solutions have a bit of a problem.  To begin with, although it has never successfully flown and therefore never successfully docked with the ISS, he includes Boeing's Starliner capsule.  From Eric:

Both Cygnus and Starliner can perform altitude boosts because they have robust, aft-oriented thrusters in their "service modules." SpaceX's Cargo and Crew Dragon vehicles, by contrast, eschewed a traditional service module in favor of a mostly empty "trunk" in order to maximize the amount of a Dragon spacecraft that could be reused. (Typically, a service module is jettisoned before a capsule reenters Earth's atmosphere.) However, NASA has said SpaceX is working on potential modifications to Dragon that might be capable of station re-boosts.

The larger service module of the Cygnus comes at the price of being a disposable, not reusable vehicle. They get loaded up with garbage from the ISS and burn up on the way down. 

NASA shows this rendering of the configuration of the ISS now (well, February 21st):

The Cygnus-17 module is almost dead center of the rendering, surrounded by the Russian Soyuz MS-19, Progress 80,  and Progress 79 a bit farther away.  The Crew Dragon, used by the Crew-3 mission is opposite the Progress 79.  

I hadn't heard that an earlier model of the Cygnus had been tested at maneuvering the station in the past, and that another test was planned before the end of the current Cygnus-17 mission in May.  

This Cygnus mission is the first to feature enhanced capabilities that will allow the spacecraft to perform a reboost, using its engines to adjust the space station’s orbit as a standard service for NASA. The agency has one reboost is planned while Cygnus is connected to the orbiting laboratory. A test of the maneuver was performed in 2018 during Cygnus’ ninth resupply mission. 

This doesn't change the fact that Northrup Grumman only has boosters for two more Cygnus missions because their Antares booster uses Russian engines that are forbidden now.  Don't forget that Boeing's Starliner launches on an Atlas V and that vehicle's days are numbered as well, due to its use of Russian engines.  Both companies, Boeing and Northrup Grumman, really need to address that.  Boeing is in a slightly better position because their missions are included in the stock of Russian engines that ULA bought for the rest of the life of the Atlas V, where as Northrup has a smaller number of flights available. 

Eric Berger points out that Cygnus has previously launched on an Atlas V rocket, so the hardware to mount a Cygnus on that booster has already been designed and proven.  While all of the remaining missions of the Atlas V are booked, one solution may be for Amazon to give back some of the nine Atlas V launches it has reserved for its Project Kuiper satellite constellation.  Another scenario involves launching Cygnus on a Falcon 9 rocket, something Northrop and SpaceX could probably agree upon in an emergency situation.

The looming elephant in the misty distance is that the ISS is "aging out" and while the current arrangements with Russia only last until '24, there's persistent talk of keeping the station going longer - perhaps until 2030.  NASA has been talking up privatized space stations, and has given awards of between $125 million and $160 million to four companies for this work: Axiom, Blue Origin, Nanoracks, and Northrop Grumman.  That's far from being the most viable option, though, and reality is that we might spend a couple/few years without a space station.