Source: Nasa astronauts stuck in space after spacecraft problems to return to Earth | US news | The Guardian . . . Butch Wilmore and Suni Williams have to wait until their replacements arrive at the International Space Station next week before they can check out later this month. They’ll be joined on their SpaceX ride home by two astronauts who launched by themselves in September alongside two empty seats. . . . This makes sense. Rather than spend a bunch of money to expedite their return, fit them into normal rotation. This keeps the consumables at the planned rate without extra mouths to feed, air to breath, and things to do. Sad to say, the two bumped astronauts will have to wait on another ride. Bob Wilson
Consumables for ISS use is a fascinating topic, and I found a few things. Water is 90% recycled on ISS including physiological outputs But O2 is an even more prompt need and it goes up as H2O for electrolysis in situ. Water upgoing appears to cost abut $10 million/yr and would scale linearly to occupancy. Food etc. went up at a cost of about $80,000/kilogram, and may be less now by SpaceX Dragon. Poop and nitrogen in general are not recycled, but this may be worth exploring before sending people to Mars. A CO2 to methane (Sabatier) experiment might be done on ISS. That is essential for doing Mars in coming decades. No doubt space folk have considered it.
