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Not only are there average daily temperature fluctuations from -80 °C to 20 °C - night to day depending on time of year and latitude to contend with. They can go much lower depending on the season. There is also the cosmic radiation on man and machine, both on the journey and on the surface. The only current solutions are to add mass to a shield or go underground.

Recent research, however, throws up newer problems - the loss of bone density in the astronauts and cardio issues. On a six month trip to the space station they lose an average of 2.1% density in their leg bone, the tibia, and 1.3% reduced bone strength. This is a permanent change even when back on Earth. It will be even worse on Mars where the gravity is only 40% that of Earth. A round trip - touch down and come back - will take about 14 months. A short stay, a few months, makes things worse.

There is also the issue that micro-gravity has on the cardiovascular system. On Earth gravity pulls blood towards our feet to then be pumped back around our bodies. We are built to cope with that. In space we do not have that so blood pools in our upper bodies, which effects blood pressure and vision. Some astronauts might not be able to come back.

These are all issues which have to be dealt with.

Lots of thinking has gone into them and one concept, Mars cyclers, is likely to win out


Mars cyclers accelerate the ship once to Mars velocity and then can be used thereafter with minimal thrust. This means you can build truly large ships with multiple gravity zones through rotation and with heavy and efficient radiation protection.

We are going to Mars and the solutions will follow the people.

When Elon Musk presented the trip to Mars and what the crew would find, he was blunt.

You may not survive the journey, even if you do survive the journey you may be permanently damage. If you make it to the surface to Mars it is likely you will die there and if you do make it back you will probably die shortly after.

SpaceX was inundated with offers to be crew.

We have known about cyclers for donkey's years - they are not new and they do not alleviate the medical problems.

We might... at some point... maybe...perhaps, overcome the technical problems of building big ships in space rather than in Coventry, but we cannot modify the human body any time soon to cope with the radiation and micro gravity of space.

If people want to die for St Elon's ego that's their choice. At least he's up front in that is what they will be doing.

Erm,

The point about the cyclers was that once accelerated they could be "spun up" to give gravity. Making them large enough would allow different levels of gravity.

Microgravity is only an issue in the ISS because it is little more than a science shack in space and cannot be spun up.

You also ignored the part about how a cycler, with a one time acceleration cost for many journeys, could carry sufficient shielding to protect humans in interplanetary flight.

So far we are constrained to get to orbit. When that constraint lifts and we are able to lift millions of tons to orbit, our entire approach will change.

Eh? The only way to get more gravity is to increase one or both mases. F = G (constant) m1 x m2 / r2. Acceleration does not increase gravity.

I ignored nothing about cyclers. They have nothing to do with getting sufficient shielding (mass) into space to protect from radiation. That has to be done with brute force in lifting it from somewhere. There would be no effect on the human conditions of bone loss or cardio complications regarding micro gravity as everything in space is in freefall. See Einstein for details.

They do allow for using the slingshot principle using the gravity of a large object, a planet, to deflect or manoeuvre / accelerate a small object, a spacecraft, from its original trajectory to get from A to B using less fuel - see Voyager 1 & 2 missions.

Artificial gravity is the creation of an inertial force that mimics the effects of a gravitational force, usually by rotation.[1] Artificial gravity, or rotational gravity, is thus the appearance of a centrifugal force in a rotating frame of reference (the transmission of centripetal acceleration via normal force in the non-rotating frame of reference), as opposed to the force experienced in linear acceleration, which by the equivalence principle is indistinguishable from gravity

See the wiki page. That indistinguishable bit means the human body reacts to spin gravity in exactly the same way as it does to natural gravity.

By using a cycler you accelerate the entire transfer mass once and you spin the mass once plus any additional force required over time.

The ascent vehicles and cargo tugs accelerate people and cargo to the cycler then return to earth. But they are light and relatively unshielded. Simply tenders for the cycler ships.

Yes, the cycler takes a lot of effort to lift the material, accelerate to its track and then spin it up. But these are one time efforts. Space vehicles do not need the same construction as ascent/descent vehicles and they last correspondingly longer. Allowing for significantly more mass for protection.

This is an incredibly simple concept, it should not be difficult to understand.

You forgot part two;

Rotational simulated gravity has been used in simulations to help astronauts train for extreme conditions.[2] Rotational simulated gravity has been proposed as a solution in human spaceflight to the adverse health effects caused by prolonged weightlessness. However, there are no current practical outer space applications of artificial gravity for humans due to concerns about the size and cost of a spacecraft necessary to produce a useful centripetal force comparable to the gravitational field strength on Earth (g).[3] Scientists are concerned about the effect of such a system on the inner ear of the occupants. The concern is that using centripetal force to create artificial gravity will cause disturbances in the inner ear leading to nausea and disorientation. The adverse effects may prove intolerable for the occupants.

You are comparing apples and pears as well as living in a Star Trek dreamscape.

I'm what?

Just because you have a vision of a slim rocket going to Mars and I have a vision of a massive rotating cylinder going to Mars. Does not mean I am in science fiction. In reality a cycler could be the size of a warehouse or the size of the Pentagon, it doesn't matter, all it needs to be able to do is resist the gravitational forces of the planets it skips around and as it will not get very close to them, that is not much.

The size and shape of a ship designed for space has absolutely no point of contact with a ship designed for ascent and landing within a gravity well.

In order to create your force that is 'indistinguishable from gravity' in order to make something 'stick' to the 'floor' requires a certain velocity at the periphery. You can either spin-up something with a small radius very quickly or have a larger radius spinning more slowly.

Take hose fairground rides where you stand against the wall and as the spin becomes faster the floor you were standing on falls away and you stick to the wall. That's the principle except that on Earth it is assisted by gravity at 9.81 m/s².

In space it is not going to happen with a warehouse or Pentagon sized object, they would be spinning so fast as to be intolerable. No, the circumference would have to be huge... as is stated by the part of your link you 'forgot' to mention. How big? Nobody knows.

My vision of a pointy rocket to Mars is only for things like rovers and other hardware, and they can still use the cycler slingshot principle - and do. I don't have one for humans because we do not have the means to build one, whatever it might look like.

Actually axiom is already working on a space station which will be spun up to gain artificial gravity.

[url]spincalc[/url] gives you the details.

Whilst 1g requires quite a lot of spin and a lot of size, Mars gravity is much easier.

The concept is there. The rest is simply engineering scale. Even Mars gravity dramatically reduces the effects on the body seen in microgravity.