I was reading the BA's blog, specifically the article entitled Mars, Congress, and what we're doing when, and I came across the following
So I got to wondering. What are these technical difficulties, exactly? What makes a Mars mission so much (fifty years' worth of research) harder than a Moon mission, or even maintaining a space station? Is it primarily life support issues, or are there additional concerns involving landing, the condition of a craft in space that long, or fuel?

Where there is a problem, what's the state of the art right now, and where does it need to be to make such a mission feasible?

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If the United Sates treated it as a bigger version of Apollo and poured Apollo+ levels of funding into it, no problem. But getting humans to mars in 20 years time when no money is being provided for it, and at a time when the U.S. government going further into debt and the U.S. has a large number of baby boomers on the verge of retirement makes it hard to see it being done within 20 years time. And the money NASA does get could well be wasted on sending humans to the moon with nothing left over for mars. But as far as tech is concerned, we could do it with what we have today, but it would be expensive.

Actually, I think it is quite possible that we don't have the tech to do it, even with almost unlimited funding. I think the big issues are physiology, psychology, and weight. The big difference from the Moon is the time it takes to get to Mars-- about 8 months if I recall correctly. Then you have to wait there until the right launch window, and then come home. All told, you are talking almost 2 years in space. Even Columbus didn't take that long to reach the New World, and he barely made it, despite being on Earth. If you want humans there, you need a lot of weight, especially if you are not going to send someone alone (which is pretty hard to imagine given the psychological issues). You come in much faster than when you reach the Moon, so you need a lot of fuel to slow down. Worse, you need to be able to take off again through Mars' gravity. I don't know if NASA even has a concept for landing something on a rough surface that carries enough explosive fuel to take off again later. Then there's the physiological problems of being in zero or low gravity for 2 years. Even carrying enough food and water for 2 years is a big problem. You probably don't have the luxury of sending animals first, because you can't keep them alive for 2 years in space without people around, so the first humans are nothing less than guinea pigs (I'm sure there would be no shortage of volunteers though). In my opinion, even with unlimited financing, the effort would essentially be murder, like the first efforts to fly from New York to Paris. And although there were many who tried before Lindbergh, the big difference for Mars is that we can't keep sending more after the first few die-- we basically have to get it right the first time or the PR coup turns into a PR disaster.

Realistically, I think the only way it might be possible is if it is planned to be a one-way trip. We would need a terminally ill person who nevertheless is in stable health for up to a year, who would be willing to undergo assisted suicide on the surface of Mars. It seems like a crazy idea, and I have a hard time seeing NASA actually doing that, but any country that pulls it off will be the envy of the rest. Then you would not need to carry as much fuel, and an accidental death would not be viewed as seriously if the person were planning to die anyway. It's the only way I see it happening even within the next 100 years.

There are a lot of problems with a manned Mars mission:

1.) Gravity. We have a fairly good idea of how to reduce bone loss and muscle weakening (vigorous, regular exercise), but even so a round trip to Mars will be (IIRC) the longest time any humans have spent in zero-G. Furthermore, we have no data on how how the human body will respond to 1/3 Martian gravity over a standard 500-day stay on the surface. Then there is the issue of radiation from solar storms, cosmic rays, and the like.

Mars' higher gravity also makes any manned mission much more difficult than it would be for the Moon.

2.) There's a lot we don't know about Mars itself. The nature of the (probable) peroxides on its surface are unknown. How toxic are they? How corrosive? Will the dust cling to suits and gears, gumming up machinery? *Does* Mars have some pathogens that could be deadly to humans? Only a sample-return could answer that last one. Is the atmosphere sufficient protection from solar storms?

3.) Living on the surface. How will we generate power? Nuclear seems to be the only realistic option, though that will greatly increase the mass we need to send to the surface.

4.) Psychology, as someone already said. A Mars mission would probably last two years at least, and possibly as long as three, depending on the profile. We know it can be stressful for astronauts orbiting the Earth on long-term missions, an environment where they at least have instant communication and a ready escape valve if anything goes wrong. But two to three years of Earth being nothing but the proverbial pale blue dot, with a long communication lag, and knowing you're stuck with 4-6 people that entire time?

I think it's safe to say that even with modern communication, and with their own companionship, the people who first go to Mars will be the loneliest who ever lived. I have too much faith in the human spirit (and psychological screening ) to think that people will go bananas on a Mars mission, but I think the possibility of severe stress reducing the crew's performance is a real one.

5.) General risk. The success figure for unmanned Mars missions is pretty dicey: 50%. I think a manned mission will have better odds, but it will be a tough sell. When an unmanned mission fails, it's something that gets a few laughs on Jay Leno and in political cartoons. When a manned mission fails, it's a National Day of Mourning, there are hearings, finger-pointing, endless bureaucratizing, paralysis by analysis. A failed manned Mars mission would be the sinking of the Titanic next to the Columbia's skiff. If the failure happened on Mars or in transit, we might never know what caused it, making it all the worse.

In short, this is something that could set back manned exploration for decades, if not permanently. They say with great risks come great rewards, but when votes, national prestige, and tax dollars are on the line...people get a little skittish.

For my part, I think R&D in novel propulsion techniques--nuclear thermal especially--would go a long way towards easing some of these problems, by increasing lift capacity and reducing transit time. But given a history of "if it ain't broke, don't fix it"-ism in NASA, I imagine we'll still be taking the slow boat there, if ever.

__________________
"Call me old-fashioned, but I think fire is magic. And it scares me a lot."

--The State

My key issue is that we haven't proven yet that we can keep a crewed space habitat going long enough for a Mars mission without help and supplies from Earth.

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Everything I need to know I learned through Googling.

There are I think 2 different issues here:

1. Do we really need to go to Mars, and if so when?

Instead of, for example, devote more funds to unmanned space probes, or devote more money to solving the problems of humanity on earth

Economic reasoning/and what purpose (just scientific, or prospect of some independend colony)

2. How should we do it?

A sized up Apollo project, or a gradual approach? (first dozens more robotic missions, robotic return missions, robotic missions that build life systems (mainly oxygen, water, food crops, shelter) and only after that attempt some human mission).

As to 1

I don't think it is very feasible and realistic to do it now (let's say within a time frame of 2010-2030), there are huge technical difficulties, it costs astronomous amounts of money.
The science community is not in favour of it. Let's face it: Apollo was for political reasons (prestige of the USA, beating the Soviet Union in the space race as moral prestige), and much less scientific. Those reasons do not exist now to do something similar, so no funds.

If the reasoning is that humanity is better off having settlements on 2 planets, then please realise that the only big threat we have is ourselves, and not some catastrophe from nature we would not survive (at least not on astronomical short scales). If for example our biggest concern were for example astroid impacts (as that is a possible threat to all life on earth), we could built a defense system or built settlements in locations that offer protection (why not built settlements on the ocean floors? relatively safe! If we can not do that, how then could we built stable settlements on Mars??)

So, in this perspective, I think there are no urgent reasons to go to Mars now, or in a small time frame.

And the realistic costs for having a real settlement on Mars (not just a couple of return trips) are enormous, since for a long period that settlement will entirely depend on resources from earth, and the transport costs are enormous. How to built a self subsistent community on a planet like Mars with no eco-system, no fuels, little sun-light, scarce water supplies, etc.?
If you make calculations about this in economic terms, this project will have enormous costs, and no clear indication it can ever break even.
For whatever reason there is to do this, I guess that all alternatives for that are simply much cheaper.

Esp. the reasoning some human-Mars-missions that settling/colonising Mars for the reason of having more living space and resources and to provide a solution to earth/humanity most urgent problems (depletion of various earth resources, like fossil fuels, drinking water, food crops/life stock, different other resources), definitely going to mars offers no solution, instead will worsen the problem since such a colony will be parasitic for a long time. There is not much to start with on Mars to build upon (not an eco system that existed for billions of years, no infrastructure left behind by previous civilisations), you would have infact to start from scratch, except for having a lot of technological knowledge.

So, my conclusion would be that we should not refrain from normal economic reasoning in the context of space settlements, and temper our enthousiasm for going on a human mission (at least in the prospect of some permanent settlement) very soon (i.e. before 2040 or so).

For the sake of the argument that 'some day' we need to have a different location as the sun turns red giant (the one catastrophe foreseeable that not even with future technology would be solvable, except for translocation to Mars or moons of the gas giants), the time frame for that allows a little delay of the Mars mission. If we make a most pessimistic that this events urges for leaving earth in some billion year from now, I guess this leaves us some time to think for a solution.

Some very rough calculation, let us divide this gigantic enterprise in some smaller steps:

Step 1: Be able to land on mars and return (robottic mission)
Step 2: Be able to land on mars and return (human mission)
Step 3: Be able to permanently settle and be self-sustanained on Mars
Step 4: Be able to translocate large portion of humanity to Mars
Step 5: Be able to land on an extra solar planet (robotic mission)
Step 6: Be able to land on an extra solar planet and return (robotic mission)
Step 7: Be able to land a human mission to an extra solar planet and return
Step 8: Be able to permanently settle on an extra solar planet and be self-sustained
Step 9: Be able to translocate large portion of humanity to an extra solar planet

Let us make some estimates here, by estimating how much more difficult each step would be as the previous, and so how much longer it would cost to accomplish as the previous step.

Amount of time necessary compared to previous step:
For step 2: around 2-5 times
For step 3: around 10-100 times
For step 4: around 100-1000 times

This reads like: if we can have a return robotic mission to mars in 10 years, then we can be all on mars in like 20.000-5.000.000 years from now.

For step 5: around 2-10 times
For step 6: around 2 times
For step 7: around 2-5 times
For step 8: around 10-100 times
For step 9: around 100-1000 times

The lower estimate then for translocation to an extra-solar planet is:
16 million years to 5 billion years

Of course these are very wild guesses, and are based at the assumption that scientific progress advances steadily, and the technological barriers (most importantly the rocket technology that can deliver speeds nearing at least10% of lightspeed, else we can't get nowhere) can be overcome.

Some wild assumption in this is that rocket science progress allows for 10 times faster traveling in a time frame of 100 years (this rule will not apply when relativistic effects have to be taken into account, so above 1-10% of light speed the technological impact on increase of speed will become less). In this scenario a one-way robotic mission to Proxima would be possible at speeds of:
In 40.000 years: 10000 km/s (0,33 % of light speed; single trip Proxima would cost approx. 2600 years)
In 5.000.000 years: 100000 km/s (3,3 % of light speed: single trip Proxima would cost approx. 260 years)

So, I guess in this timeframe it is possible to "save" all of humanity from excarnation before the sun is red-giant (even in the pessimistic scenario, since we will have different places in the solar system already were humanity can live before the effects of the run becoming red giant become a serious threat to humanity (which will perhaps start in 500 million to 1 billion years from now).
Even slower time frames would make it possible for humanity to survive, if we can translocate to cooler places in the solar system (moons of Jupiter), but for best survival conditions, a suitable planet in an exa solar system (and probably different planets for most survival probability) would be much better of course.

So, this kind of scenario is the only thing we seriously need to consider in planning for human mars missions. It shows that there is no urgent need to hurry, but neither can we delay it too long.
So, a human mission to mars within 50 years seams a reasonable time frame.

As to 2

What would be the clever way to do it?

I don't think a scaled-up Apollo mission will get us there. We need to think in smaller steps:
First some more robotic missions, to have some more detailed info on Mars, thereafter robotic return missions. Both for developing the return stage techniques and for more closer examination of Mars samples.

Second, we can first develop robottic missions that can built life support systems, so that oxygen, water and food crops can be available for long mars missions.

The third stage is to built a permanent station in Mars orbit (like the ISS). First components can be brought by automatic missions. Thereafter (optionally) permantly manned by a crew of 4-8 people, and resupplied at least 4 times a year. The station should be able to function automatically for several years.

Then we can start a series of trips to Mars. First for doing some more exploration, but then also to built equipment for later missions and in preparing for a permanent Mars ground base.

The most difficult parts in this are the landing and return stages (Mars has far more gravity then the Moon) and landing is also exceptionally difficult with a thin atmosphere, and how humans can accomodate for such long trips for a large part in low gravity, radiation risk, etc.

Of course, if space elevators were develop and in operation around that time, the expensive trips from earth orbit would become much more economical. If the concept of space elevators is possible, perhaps such ventures should wait for the realisation of space elevators first.

"Thereafter (optionally) permantly manned by a crew of 4-8 people, and resupplied at least 4 times a year. The station should be able to function automatically for several years."

Unfortunately, that's not possible. Trajectorys to fly to mars are only available for about a month, every 26 months or so.

Doug

Yeah, forgot about that one.
That then underlines the need of a station that can work automatically for several years, since it can only be supplied once every 26 months.

Don't know if having a permanent (robotic or optionally manned) station is a necessary part of a mission, but I guess for permanent inspection of Mars weather and such, and for relaying data to ground stations and robot explorers and the human crew on ground, this might be needed.

There is of course also the possibility to make a settlement on Phobos or Deimos.
(they could be the object on which to attach the space elevator perhaps).

Maybe it would be possible-- but you'd have to "cache" the supplies in space well in advance of the actual manned mission.

__________________
Logic is the grammar of truth.

Meaning and absolute certainty are incompatible, and profound meaning and absolute certainty are profoundly incompatible.

The only thing intelligence is capable of is recognizing itself.

I think the biggest problems are psychology & money, with physiology maybe not as big a deal as one might think.

As for technology, I think that given the enormous amounts of money required, we could build & launch a mission to Mars right now. We know how to build big fat rockets. All we have to do is figure out the operational engineering of building big fat rockets in orbit. Once we have done that, we build them, light the fuse and stand back. We can pre-position provisions in orbit around Mars for years before sending people. We know how to do all of that.

I say psychology is the real problem because once the ships start moving, they are literally and explicitly on their own for three years minimum, period. If anything goes wrong, there is little or nothing the rest of us can do about it except watch. We can compare this kind of isolation to the voyages of exploration back in the 1400's & 1500's. But Magellan's round-the-world voyage lost over 50% of its crew, including Magellan. Loses like that were not unusual, if I am not mistaken. But our psychological approach to space flight can hardly stand the loss of a single person. If we lost even one astronaut, it would be the first & last trip to Mars for decades at least. Even the people who winter over at the south pole know that they can get out if it is a really big deal, as in the case of the doctor who had to be removed a few years ago when she was diagnosed with cancer. Even the people going to the moon know they can pull an Apollo 13 swing around the moon if need be. But once the Mars bound folks take off, there is no "rescue" and no "return". So just imagine some number of people locked up together in a small volume for years, no going outside, no conversations with Earth (absent long delays). The mental possibilities are impressive.

And consider this. If you are a conservative Republican President, do you launch unmarried couples into space?

The other big deal is money. To do it right will be a few trillion dollars, which is really hard to come by these days.

I don't think people will go to Mars on any government sponsored mission before the year 2100. There may be ambitious private missions, but I don't anticipate success.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

HI,
It would seem that the success of a manned mars mission would depend on
sending the required material ahead, landing some of it on the surface where we intend to land our mission, as well as landing enough SRB components to aid in launching a vehicle from Mars' surface and rendezvous with a Mars orbiter,
and refueling THAT in orbit as well.
You still have to beat your extended low gravity problem as well as
the extended exposure to radiation.
Advanced vehicles to orbit helps to solve many problems....extra parts,
filters, fresh water, food, medical, etc.
No one said it would be cheap, convenient or without risk.
Sure is the most expensive gravel in memory, but....it gets you into the
great book of records.
Toseek is right ! You need to have a perfect handle on Men in LEO before you ponder Mars. No question.

Best regards, Dan

I'll tell you why we're not ready.

The heaviest thing we've landed on Mars is about half a ton. With MSL, that will go up to about 750 kg.

We do not know how to land anything heavier on Mars. Period.

We can wave our hands in the air, say words like balute, biconic, apollo derivative, mars direct...but we don't actually know how to do it.

Doug

If I was going to mars I couldn't in good conscious go on a mission where they were going to bring me back. It simply would not be worth it. The money it would cost to bring me back could save many lives on earth. If we define "saving a life" as giving five or more extra years of life to someone who would otherwise die, then I would estimate that used properly the money saved from not returning me from mars could save a vast number of lives hear on earth. More than thousands. Judgeing from my actions so far, I value my own life as worth more than the lives of 500 complete strangers, and I'm quite comfortable with that figure, but more than thousands of compete strangers? Nah, leave me on mars.

Ron, The purpose in going is to bring back a bit of gravel and a little bit of atmosphere and experience. Some say that this can not be done by robots.
So.....a manned mission is supposedly the only we can satisfy this esoteric
curiousity. This is supposed to transcend the great things we could do
with the money.....ie send several thousands of kids to college and make quality taxpayers or ressurect the energy research and development administration or something else that would be immediately usefull . It's all about imagination.

Best regards, Dan

Wrong logic, for two reasons:

First: If they should not bring you back, they should not have put you there in the first place.

Second: Not bringing you back, or better stated, not spending that money on such a mission, would in no way guarantee that that money be spent on saving other people's life. Instead, it could have also gone to warfare, and thereby even killing more people.

But, using some economic reasoning would surely be very wise before a lot of money goes into such projects.
It disfavours manned missions strongly, as the scientific data we could get by using only a fraction of that money using robotic missions are many times more.

If people are set on sending people to mars then making it a one way trip would save costs. The cost of getting me to go on a one way trip would be to save many lives on earth.

Tust me, I wouldn't be agreeing to a one way trip without lives saved in advance.

How, exactly? One way you've then got to launch and land an entire life-times quantity of supplies, spares and so on - dozens of extra missions. How are you going to do that cheaper than flying home?

There's this thing called dying that renders resupply unneccessary.

Sir: The reason a man will go is in order for him to "do" what only he can do
and then to return that individual or crew.....back to earth.

There is really no point in sending man on a one-way junket at exhorbitant expense to the martian surface and that's it. It is far cheaper to set him down in death valley and let him enjoy the experience there.
The point of going into space is to accomplish something tangible .

Of course,......such scrutiny begs the whole question of ' going to mars '
in the first place .

But the OP is the difficulties involved in that endeavour. It's discussion is purely acedemic, which I enjoy.
When you finally see the entire scheme laid out end to end, it will be far more
complex and expensive than you have imagined thus far.
At which point it will be left to question: "Is it worth it? "

Best regards, Dan

People will go to Mars for the same reason they sailed into uncharted oceans, hiked to the south pole, and my cousin bungee-jumped from a hot air balloon. They will go there for no other reason than that they can. It's just a matter of time. Any argument over whether or not they should seems pointless to me, if only because we all know that sooner or later they will.

I don't think it is a grand idea to try doing so now, or anytime soon, for reasons already stated. But I have no problem with the idea of starting to climb the ladder to mars now, learning to do the things we need to do (and in some cases have already done & forgotten) to get there.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

Big difference between sailing the ocean and traversing the planets.
A primitive person can build a raft and do the oceans. No question.
Travel and return to the planets with no expectation other than a record is less than presumptuous. It is in a word...."noncompelling".

Completely apart from the fact that I consider any current intention of flying a human to Mars about as necessary as donating to a "throw Paris Hilton a party" fund-raiser or as beneficial to humanity as driving an SUV, there is one aspect that intrigues me and which I have never seen mentioned in any of the television documentaries which are so enthusiastically commentated by human space travel advocates, e.g. Jesco von Puttkamer.

Coping with zero, resp. low gravity in space or on the surface are one aspect, but what do the astronauts do when they land. i.e. in the first days/weeks?

The long time Mir/ISS inhabitants need extensive assistance upon returing to Earth after ~6 months in orbit. They are given intensive medical attention and need weeks before they can walk freely.

When a group of astronauts lands on Mars, its members will have lots of work to do in a very short time. How are they supposed to do anything at all if they can barely crawl around? Could they really land in a vehicle that would allow them weeks to recoup before putting that first, all important footprint on Mar's surface? Without outside help, having just spent ~8 months in a space hull with the added psychological hardships?

Saying "it's a feeble creep for man, but a giant crawl for mankind" would be anticlimatic.

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Ach, mein Sinn, wo willst du endlich hin, wo soll ich mich erquicken? Bleib' ich hier, oder wünsch' ich mir Berg und Hügel auf den Rücken?
Bei der Welt ist gar kein Rat, und im Herzen steh'n die Schmerzen meiner Missetat, weil der Knecht den Herrn verleugnet hat.

Funny

But they´ll have to cope with something less demanding than Earth´s gravity.

__________________
What brings us together is stronger than what pulls us apart

One of the best threads yet... "CONGRATULATIONS" to all. Obviously some thought has been evident here.
From all this I gleam... We are not ready yet.
The list of reasons just keeps getting bigger and more complex.
We want to do this, but can not.
As our technical ability advances so will the problems fall away. I imagine a maned mars mission will be a fact before the year 2030. but by who?
I suspect a different approach as yet not possible.
Build the interplanetary craft in space, in Earth orbit. Yes. I know thats a big step. Way beyond us today. But venturing to mars from a orbiting mother ship might be a easy way to supply the needs better. Time is not the enemy yet. We have no need to rush before a failsafe method is a reality. Keep the interesting stuff coming.

So present boosters have marginal thrust to get one human to Mars alive. We can build boosters with several times more thrust, but we haven't done that yet, so we don't know the number of tries needed to get it highly reliable and safe. With bad management and/or not enough funds, it could take 20 years. Then we need to design the 2nd and third stage rockets. The return rocket might be thought of as a 4th stage. Lots of tests are needed to be sure these 4 stages work well and safely together, perhaps 20 more years. We can increase the safety, comfort, number of crew members, redundecy, options when a component failure occurs, and shorten the number of months in near zero gravity. We likely can rotate for artificial gravity, but each of these add mass at lift off, and increase the amount of testing needed. In theory, we could assemble the Mars craft at the ISS = international space station, but that compromises most of the uses of the ISS, and creates significant hazards for the assembly workers, and other ISS crew. It is doubtful that we could get all our parteners in the ISS to agree. Even with enthusiam, 40 years is optimistic and it is doubtfull the ISS will be safe 40 years from now, even with extensive renovations.
Ten billion dollars per year might not get us to Mars in 40 years. There is considerable uncertainty about hundreds of details. If we wait a few more years, we may have a space elevator, or other technology that reduces the mass, shortens the travel time, and we will surely have a better handle on some of the many details. Neil

The surface gravity of Mars is only about 0.38 of Earth (Mars Fact Sheet). I don't think they will have such a hard time at Mars if they work at keeping in shape on the voyage. But once they return to Earth, and a full gravity, after a few years at zero or small gravity, that is likely to be a big deal.

But the really big deal is that people will go to Mars and people will stay on Mars. Just as people crossed the seas to find a new place and a new life, they will do the same with Mars. They will go there and they will stay there. They will be hard pressed ever to return to Earth, and they will have offspring who will be literally unable ever to return to Earth. I think the eventual inevitable colonization of Mars will be a speciation event. By going to Mars we will eventually create a new species of human who can never return to the home world.

I don't think people will be going to Mars in any organized fashion for a long time. But when they do, it will be the beginning of a new human species.

__________________
The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

*******************
Sir: It is a near certainty that a manned mission to mars will require a
ship assembled in space, and most certainly will NOT "Blast Off" from Earth.
It is also a near certainty that a Manned Mission to Mars will require the advanced staging of fuel, both on the martian surface and in orbit, as well as fresh water, parts and food etc.
Sending a mother ship in advance to orbit mars will facilitate recieving fuel
and readying the return vessel, which will bring the return astronauts to LEO where a shuttle will return them safely to earth. Independent mission vehicles
are the key to any success for such an enterprise. The biggest chore, by far is both martian re-entry and martian lift off and successfull return to orbit
to dock with the return vehicle. Easier said than done.
A spining vehicle may be the answer to the required gravity, and solves many problems.
Is it possible? Just maybe. Costs? Probably 30 times what most people think. Even that number is conservative.
But the concept of multiple vehicles doing the job they do best in concert with mission objectives may, in fact, breathe sense into the design debate before us.
There is a distinct adage for engineers which states "Divide and conquer".
Understanding this opens doors to parallel thinking.

Best regards, Dan

So you want to spend a few hundred billion dollars to send a man to mars, to watch him die....don't bring him back alive of give him supplies to survive - oh, no - because THAT would be a waste of money.

Sorry - I don't get it.

Sending a person to mars costs a lot of money. Bringing them back also costs a lot of money. Sending a person on a one way trip would be much cheaper than sending someone on a return trip.

But maybe you're asking why send someone to mars at all? Well that's a matter for another thread. This one is about technical difficulties of a mars trip and eliminating the return leg eliminates a lot of the technical difficulties.

Not really. Landing on Mars is the hard part. Flying back is actually comparatively easy - certainly little more of a technical challenge that launching from the moon.

Doug