Actually you could do a one way trip to the Moon and it requires less technology than a two way trip in some ways, as you only need the technology to get there, not to get back.
Indeed, if someone was really keen to get to the Moon as quickly as possible with the minimum of development time and initial cost - though probably much higher overall cost, they could do just that.
They had this idea, very early on, had an idea to just send a single astronaut there, who would live on the Moon for some time, resupplied from Earth, very like the Mars one idea for Mars.
"Another approach was the proposal to send a spacecraft on a one-way trip to the moon. In this concept, the astronaut would be deliberately stranded on the lunar surface and resupplied by rockets shot at him for, conceivably, several years until the space agency developed the capability to bring him back!"
That is very like the "Mars One" approach for Mars. Requires less technology to get to the point where you have your first human to the Moon - so - you might get them faster - at an earlier stage in the program.
Though it's more dangerous - any time spent on the Moon is risky, so the longer you spend there, the more chance of dying from space suit failure, damage to your landing module etc. And in the case of the Moon it also means you have to design your landing module to survive the harsh lunar night. I very much doubt it anyone would do this for the Moon especially given how easy it is to escape from the lunar surface to lunar orbit. But it could be done.
For more on this and other early ideas see Chariots For Apollo, ch3-2
The lunar orbit rendezvous one which they eventually used was originally one of the lowest ranked of their mission plans
Lunar Orbit Rendezvous and the Apollo Program
They had already soft landed the lunar Surveyor 1 so certainly had the capability to soft land a supply depot for the astronauts next to their proposed landing site.
The whole thing was a case of balancing risks.
With Mars, you can do a two way trip easily if you go to orbit around Mars and then return. Your astronauts get to orbit Mars much as they orbit Earth in the ISS.
In terms of fuel needed, and if you go to an elliptical Mars capture orbit going close to the Mars surface perhaps twice a day, then it's about equivalent to landing on the Moon - though of course with many challenges for sending a human there.
This is a video I did to show the spectacular Mars capture orbit they could use in the HERRO plan for one way to do this.
Speeded up 100 times, this is a 12 hour orbit. Every day it approaches the middle side of the sunny side of Mars twice, so you get to see both sides of Mars in sunlight up close every 24 hours. That's also when you do most of your surface science and driving things around on the surface, anything that requires fine control. Then as it goes out away from Mars on its long orbit that's when you get to sleep or relax, write up, communicate home, etc. Though you'd still have much tighter control of the surface rovers than anyone on Earth throughout the orbit. The spacecraft shown here is a futuristic one, the "delta flier" from the program Orbiter, not an actual proposed Mars spacecraft.
It's only if you land that it gets hard. The thing is that because of the rocket equation, a small increase in escape velocity means a huge increase in the size of rocket needed to escape from the planet. To send people into orbit from Earth needs massive rockets as we know. To do it from the Moon you just need the lunar ascent module. Mars has 40% of the mass of Earth. So needs large rockets to get back, not quite as large as the Saturn V but much larger than the lunar ascent module which was just the size of a car. And most of the mass needed to get back is the fuel itself.
This makes it much harder to get back from Mars surface to Earth than to get back from the Moon, because you can't just take off from Mars in the equivalent of the lunar module.
One solution, suggested in the "Case for Mars" is to make most of the fuel on Mars, so you end up taking only 6 tons of fuel there. You still need a return rocket large enough to carry the hundred tons of return fuel. Our Final Hour
However I don't think we are going to send humans to the surface of Mars any time soon for planetary protection reasons. Especially when you take account of the global dusts storms, the way all of Mars surface is interconnected as a single system, and the high chance of a hard landing which would end up spilling contents of a human occupied spacecraft over the Mars surface and in case of a targetting error possibly directly hitting a region of special interest.
When the time comes that international COSPAR committee of astrobiologists have to pass the NASA plans for a human landing, I can't see them answering "yes it's fine" - surely as they have done before they will need to say "more research needed".
The very last thing we want to happen is to go to Mars just to discover the life we brought there ourselves - that would be a huge anticlimax to all the searches for life there.
What we can do, right away - is to continue robotic exploration of the surface, controlled from Earth - and also if it makes scientific and economic sense and we sort out the many technical and human challenges - we can send humans to orbit around Mars. They could control robotic avatars on the surface via telepresence, and this would greatly speed up exploration of Mars and science return. Whether you'd find out more that way than you would by a stepped up robotic exploration from Earth is hard to say, given the huge expense of it. But might be more effective. It's probably a lot more effective than sending humans to the surface, because they can control robots anywhere on the surface of Mars from orbit, not just limited to one spot - and you don't need to design a lander for Mars. But as well as that it's also far safer, for humans, and it is far safer for Mars also.
Then leave decisions about whether humans should go to the surface until later when we know more about Mars.
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