This is waterfall method propaganda! It never works out this smoothly. They probably forgot important requirements like: the astronauts need to be alive on Mars.
2 years later: It's now up to the lawyers to figure out if it's the rocket that doesn't meet agreed requirements or if it's on the customer for not giving proper requirements.
One that is being built under waterfall methodology. It has been being built for several years. That's the Blue Origin New Glen heavy lift reusable rocket
One that is being developed under an agile methodology, it flew as a subscale lander to test their engine and flight control, it has flown four full test flights, improving on each. That's SpaceX's Starship
We are yet to see either launch a payload to orbit
All the projects that have shittier outcomes in my experience is always waterfall. This is mainly because the stakeholders usually have this bright idea to be added in the middle of development that's really need to be added at all costs and then got angry when the timeline got pushed because of their fucking request breaking a lot of shit.
At least scrum has a lead time of around 2 weeks so that when someone has a idea we can tell them we'll add it to the backlog and hope they forgot about it during the next sprint planning.
I'm sure, doth the Astrumants should survive the landing, there should be a way to return, and they need a shitter as part of the missed requirements. As it's a waterfall, that will come in the second, third, and fourth trips.