Kaos

Isn't the reason for half the suggestions forum "What would you like to see added to KSP"? I mean besides development discussions. What I would like: More flexible game modes; life support; better system for planetary bases.

A part that can firmly connect to planet and moon ground and that connects to all of these parts that are not further away than 20m. So you can build a colony without complicated interconnections that are not fun to place but only need time. And cause bugs with bigger colonies. Life support parts

This effect is especially low, if you are fast relative to the distance.

Orbiters cannot drill to see what is beneath the surface. A series of few hoppers would also work, but need more time. Regardless of which, they would help to see where are better locations for resource gathering, hence where could the base reduce the necessary material input as easy as possible. I do not see where the cheaper approach is dead, considering the growing numbers of cubesats. And indeed: For a landing the preceding rovers are not necessary. But they would increase the chance to stay, at least if it is possible to stay, which is admittedly disputed.

If you drill oil and trade it for your supplies, I would not count if self sustainable. It might be economical lucrative, yes, but it does not supply itself with the required ressources. And every equippment you bring to antarctica has to be unburried once in a while and capable to survive the long arctic nights. Unless you count the very most northern parts of antarctica, these are much simpler anyway. The point of cheap trade is precisely why these kind of colonies do not happen on earth: Trade is cheaper. Even where selfsufficient colonies were possible, we go there for drilling or digging and bring the ressources back and supply from the home base. Trying to build a self-sustained colony on earth first would be a useful preparation step. We could reuse Biosphere 2 for example. But this time we should try to live self-sustained there and not try to cultivate 6 different biozones there with 8 people

Alone aerocapture of such a big object will take ages (mass is cubed with radius, area, hence braking is only squared with radius). Hence, you will have only very little control over where it will finally go down. Also will a 1 km chunk have apocalyptic impact even if it goes down in Antarctica.

Indeed I was not precise: By surviving I meant surviving and producing most of your supplies at the location. Of course surviving in Antarctica is easier as long as you plan to import nearly all of your supplies. Water can be found on Mars and the water recycling system of the ISS should be able to purify it (splits the water to hydrogen and oxygen, recombines it to pure water). The minerals can be imported in the first years from earth, later produced locally on Mars. As the water supply chain is one of the most crucial parts, every thing of it should be there multiple times and a large storage should be in the base, too. I would consider water for 10 earth years (= 100 t per crew member, based on 27 l consumption per astronaut from a NASA measurement) a reasonable amount, which can also double as 5 m radiation shield over an area of 20 m^2 per astronaut and as algae tank for food production. The main problem with the sand storms is the reduction of sunlight. But on the other hand the wind speed in sand storms is at least 20 m/s (otherwise the particles would fall down). Wind energy scales cubed with the speed, hence 20 m/s of the 0,4% Mars atmosphere deliver the same as 5 m/s in earth atmosphere. 5 m/s is not a great speed for wind power on earth, but still ok. So for backup power it would help. Of course a bigger variety of power sources would be better (power storage, geothermal (or how this is called on Mars), nuclear, ...) and in times with no dust storm solar is the dominant supply or at least it dwarfs wind energy then. Allow me an additional question: Do you consider it doable (in current NASA budget or another "reasonable"* budget) to supply 3 people on Mars only with supplies from Earth? Because this plan would fail completely if that is not possible, as it is build on reducing supplies slowly instead of magically putting a self-sustaining colony on Mars. * I have put the "reasonable" in quotes, as it is of course only reasonable if such kind of Mars base is a goal. I would for example prefer a fleet of rovers for pure scientific reasons before. And some autonomous infrastructure to test some of the resource gathering. Afterwards I think a Mars base and ultimately a Mars colony should be a goal but regardless whether it should be a goal we can discuss whether it is feasible.

I did not write 100 spirit rovers, I wrote Spirit sized rovers. The costs of Spirit were that high because of dense analyzing components, development and extra high quality control, because a single rover may simply not fail. I belief that with restricting to base functionality (driving and scanning for resources) the costs per rover can be lowered to 10 million per rover with 500 million development cost for the program. And 50 of the 400 million for the launch convert to 4 million per rover in the Delta IV Heavy case or to 3 million per rover in the Falcon Heavy case. And if 10 rovers fail because of reduced quality control it will be still more rovers for less money, hence worth it.

My KSP rockets also burn often continuously until the orbit is circular. Especially when the upper stage has a low TWR for full reusable interplanetary missions.

I think it is cheaper to go to Antarctica than to Mars, but it is easier to survive on Mars than on Antarctica. Whatever you build on Antarctica must be temperature isolated against a thick cold atmosphere, while the atmosphere on Mars is very cold but much thinner, hence you loose much less heat there. On most locations you have the problem that you have to dig yourself out once in a while, that simply does not happen on Mars. On Mars you have sunlight every day, but in the huge sandstorms. But then you have wind. So a combination of solar and wind will always give you power. Solar will go down up to 20% if you let sit the solar cells around and do not care, but at least you get the 20% year round. Then collecting resources from the ground is simpler on Mars, unless for water, but that is still not difficult on Mars. On the other hand I agree with you that some Mars colonization plans are far too optimistic. A Mars colony has to be well prepared and there will be problems and not everyone on Earth will want to go there. Mass migration is also something I do not expect to happen soon, even if a colony on Mars would be a flawless success. While I am unsure whether we manage to construct a Mars colony I belief it is possible: Starting with a big amount of Spirit sized rovers to search for resources on various locations on Mars (some 20 per launch of a Delta IV Heavy or 40 per Falcon Heavy) we should send about 100 of them. Then one should construct the settlement more like a base than like a colony: Fix an amount of people you can safely supply from earth and bring back in case of problems. 3 will suffice in my opinion and is doable within 20% of current NASA budget. The base will set up stuff (witch itself is at first imported from earth) to supply more colonists on Mars. If you can get all your water locally you will reduce your mass requirement per crew member by 90%. Together with food and oxygen even by 95%. So the first couple of years your growth will be mainly restricted by the constraint to have enough return capabilities there. Over some years you can build up a base of 30-60 people with that technique. From there you can start bootstrapping industry. I have also some idea about the order which might be useful, but that would be quite lengthy and contribute only very little to the topic, so I skip that for the moment. Of course this plan is vulnerable to vanishing funding in the meantime, hence I am unsure whether we manage while I am sure it is possible. And of course not everybody will like to live in that kind of base/colony. But I am sure we will at least find some 1000 who do. Compared to worlds population that is by far not many, but still enough. This plan has a sure supply at every time and a return plan in case of emergencies. In case of some fancy cheaper transport possibilities for Mars to appear (rockets just tanked and reflown, high thrust high Isp propulsion systems, teleportation, ...) I would stick to essentially the same plan, just a little bit upscaled. For the discussion itself: I prefer not thinking of you being pessimistic but to point out possible problems and warn in case of too optimistic plans. A role I consider to be very important in every discussion and which is in my opinion often not honored enough. So if you or someone else see any shortcomings in my plan I would really like you to point them out, so I can go into more detail, fix it or realize that the plan is flawed. As we all do not know "the truth" I try to be open to all that possibilities.

The highlighted things do not coexist, which is my point. There were two possibilities under discussion: Low energy transfers -- utilizing gravity assistance on complicated flight path Low thrust propulsion with a vast amount of orbits only using short burns in each orbit for not having to pay the factor of 1.5 for the Delta-v requirements Low energy transfers are faster and more efficient than the vast amount of orbits to compensate low thrust. Hence, I would prefer the low energy transfers.

I would prefer the faster and more efficient low energy transfers over a vast amount of orbits. Trajectories which are faster and more efficient should always be preferred. Even if time would not matter at all, the better efficiency makes it worth.

I like to see the Feynman-Stueckelberg-interpretation https://en.wikipedia.org/wiki/Antiparticle#Feynman.E2.80.93Stueckelberg_interpretation as reason: Positrons are electrons moving backwards in time. Hence their interaction is time-reversed, but otherwise the same. It is disputed in how far this relates to reality and in how far it is just a mathematical feasable description, but if it is so, it is a quite good reason.

On a free return trajectory you can get back to earth without fuel. That is why I would prefer this kind of trajectory.

I was speaking about low thrust systems, not about high Isp systems. I would not consider NERVA a typical low thrust system. Indeed can the technique of multiple orbits compensate a little too small TWR. But it has its limits.