A one way mission skips any return rocket needs, extends the research mission by decades and slowly builds up the infrastructure on the surface.

The longer mission on Mars would require regular supply shipments, though the base will be able to get their needs from Mars and slowly reduce supply needs over time as they build up their self-sustainability.

  • $\begingroup$ A manned mission extended to decades requires a very reliable supply transfer very two years. If a single supply rocket fails before a sucessful and precise soft landing the supply chain should not be brocken or delayed. There is no possibilty for an express emergency supply mission if some spare parts are needed for the martian base. Everything should be available at mars before needed. A redundant supply delivery would be necessary. If all supply missions are sucessful there will be a lot of excess supply. $\endgroup$ – Uwe Dec 22 '18 at 17:09
  • $\begingroup$ If you already have one extra supply shipment there a single failure wouldn't be catastrophic. Then a second though longer taking supply launch can be sent. $\endgroup$ – Brooks Nelson Dec 22 '18 at 19:18
  • $\begingroup$ There is no guarantee that a single failed shipment is followed by a sucessful one. $\endgroup$ – Uwe Dec 22 '18 at 19:56

Current proposed manned Mars mission plans are very diverse and which plan you chose would affect whether to include a return trip. Let's weigh some pros and cons:

Pros (no return trip)

  • Save on fuel transport costs OR

  • Don't require ISRU fuel factory

  • Spaceships used once and can be constructed cheaper

Cons (no return trip)

  • No sample return means heavy lab equipment needs to be sent (Earth labs are very advanced)

  • Habitats need to last forever or for a much longer time

  • Moral/ethical/PR/medical implications of stranding people on Mars forever

Taking these factors into consideration, a short duration mission as frequently proposed by NASA would probably be cheaper with a return trip as designing habitats and equipment to last for a couple months is far easier than designing a habitat to last forever. You could also save tons of mass by bringing little scientific equipment and instead just bringing sample collection equipment.

If you're looking to establish a permanent colony, and have the money to do so, I still think that return trips are worth it. People being away from Earth might be very damaging to the psyche in the long term + the effects of low gravity on the human body are still unknown. Additionally, the costs you save by not including a return trip don't scale that well as the major difference is that you need some sort of ISRU for fuel production on Mars. Throwing away the transport spaceship every trip can't be cheap. Launching from Mars is also easier due to low atmospheric pressure and lower gravity. A Mars economy also needs to make money if you're planning to make it permanent and no return trips removes lots of people from the willing astronaut pool of people and basically kills any Mars tourism.

  • $\begingroup$ The Martian movie & Nat Geo's docu-drama Mars (Season 1&2) would be a great reference to your answer. I like both of it so so so much. $\endgroup$ – Boosted Nub Dec 21 '18 at 0:30

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