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ToSeek
2003-Jun-09, 05:11 PM
Why is Mars so hard? (http://www.thespacereview.com/article/23/1)

Interesting article about the technology behind the Mars missions and why so many have failed. The site's been "slashdotted," so it may be hard to get to it today.

QuagmaPhage
2003-Jun-09, 06:01 PM
The story on Slashdot has a lot of interesting commentaries and the text of the document.
http://science.slashdot.org/science/03/06/09/1222201.shtml?tid=134&tid=160
Sometimes someone makes post a copy or makes a mirror of an article to prevent the "slashdotting".

Argos
2003-Jun-09, 06:39 PM
This makes me wonder if we’ll ever put humans on Mars. The Aerospace Corporation Complexity Index dooms the mission to failure. It would be a genocide case we should attempt today. When I consider the mass to be conveyed to Mars in a manned mission - a couple of tons I imagine – I also think of the means available: machines that were conceived centuries ago and which were little improved in the last 70 years. I suspect that I will never see a man walking on Mars. Alackaday!

BigJim
2003-Jun-10, 12:18 AM
Argos, I disagree with you in every way possible. Could you please list some specific reasons as to why you think so?

Chip
2003-Jun-10, 12:48 AM
Mars is difficult to reach. However, I can remember when the moon was considered next to impossible to land on. People made it there with technology that is now in some ways antiquated. About 20 years ago, the human race reached the level of technology wherein a one-way Mars mission is conceivable. Since that time, even without a concerted effort to place explorers on Mars, we presently have, in theory and in fact, all the components necessary to place a small team of explorers on Mars. It would be a long trip, short stay, and long return trip.

However, the Mars Society has plans based on living off of Martian resources (including producing water, return trip fuel,) that would greatly lengthen a Martian exploration.

See also other projects by the true believers at Robert Zubrin's Mars Society (http://www.marssociety.org/) They have some very interesting ideas.

And finally, despite the difficulty in reaching the red planet, we have in fact already landed there, with robots. Avaition history has many more errors and disasters than the lost Mars probes, yet aviation is also a success. So will be robotic and eventually human Mars missions. :wink:

daver
2003-Jun-10, 01:26 AM
Argos, I disagree with you in every way possible. Could you please list some specific reasons as to why you think so?

I tend to agree with Argos. I don't see a manned Mars mission unless it goes nuclear, i don't think that will happen in my lifetime.

I'd think a manned Mars mission is going to require on the rough order of 100 tons to be landed on Mars.

I don't know what the complexity index is.

I don't see how genocide enters into it, unless the antinuke protestors claim genocide for the launch. If he means suicide, i disagree.

I'd say rockets improved dramatically over the last 80 years, less dramatically over the last 30.

So, that's one agree (no manned landing in my lifetime) one agree in intent but not in actuality (he thinks only a couple tons to Mars, i think a lot more), one don't know, two disagree.

BigJim
2003-Jun-10, 01:50 AM
If one small (Prometheus-class) nuclear reactor is available, a complete human Mars mission becomes available with two Saturn V-class boosters. The book The Case for Mars fully explains this, as does this website (http://www.nw.net/mars), but I will summarize the main concepts of the Mars Direct plan here.

First, a Saturn-V class booster launches a 40-tonne unmanned payload to the surface of Mars on a 258-day Hohmann transfer. This craft, called the Earth Return Vehicle, or ERV, lands at the future landing site of the human Mars mission. It is an unfueled methane/oxygen propellant two stage ascent and Earth return vehicle. It lands with a 100 kWe nuclear reactor, a light truck, a set of compressors, and a chemical processing unit. The truck is telerobotically driven a few hundred meters away, and it deploys the nuclear reactor which will power the chemical processing unit. Six tonnes of hydrogen are brought from Earth, and it is reacted with Martian carbon dioxide to produce methane and water. The water is electrolysed to provide oxygen, both as air for the crew and as propellant, and the hydrogen is recycled into the system. This produces 48 tonnes of methane and 24 tonnes of oxygen. Martian carbon dioxide is disassociated to provide 36 more tonnes of oxygen. 108 tonnes of methane/oxygen propellant is now available, as is nine tonnes of water. 96 tonnes of propellant will be used to fuel the ERV, and the remaining 12 tonnes are available for internal combustion engine rovers. Now, from one Saturn-V class booster, we have a fully fueled Earth Return Vehicle, complete with water and air, waiting for the crew on Mars, one which has survived a landing.

Twenty-six months later, in the next launch window, two more Saturn-V class boosters are sent towards Mars. One carries another ERV for the next landing site, and the other is a "Hab", the crew's vehicle. It carries a crew of four, an internal combustion pressurized rover, two light rovers, and 500 kilograms of scientific equipment (500 more are on the ERV, making for a total of one thousand kilograms of scientific equipment).
Provisions for three years are carried. After launch, a cable is extended between the Hab and the upper stage of the booster, providing artifical gravity. The total mass of the Hab is 28 tonnes and it can be sent on a 180-day trajectory.

This is an extremely safe plan. The crew has a rover with a one-way range of 1,000 kilometers if they do not land right next to the ERV. Even if they land on the other side of the planet, the second ERV can be targeted to land near it. Even if both of them miss, the crew has provisions for thee years and can just wait until another ERV can be sent out. The plant is extremely robust.

The crew stays on the surface for 1 1/2 years, and there is ebough rover fuel available for about 22,000 kilometers of traverses. Thus, each mission can explore about 800,000 square kilometers during their stay. The Mars Direct harware can be easily modified to accomplish lunar missions, also.

So, we have a complete Mars exploration mission with nothing more than two Saturn Vs, some chemical engineering that has been around for over a century, and some present-day technology. No fantastical schemes are required for a Mars mission. We can do this, now.

So what was it that you were saying? :wink:

wedgebert
2003-Jun-10, 02:21 AM
I think you miscounted, I see three Saturn-V boosters in that proposal. Three boosters is too many and your plan will FAIL!

Secondly, I gotta say why go to Mars and do research when you can go to the moon and build things? A fission powered lunar colony would have all the waste heat and energy it needs to turn lunar regolith into valuable materials such as calcium, aluminum, titanium, silicon and oxygen.

At first, unmanned "probes" could be sent. These probes would be like little automated factories. Some would be designed to gather regolith and bring it to refining probes that would turn it into useful materials.

Along with that, a landing area could be cleared off and leveled off. Around the area would be storage area for the refined materials. That way when manned missions follow, they have a place to land and replenish most of their fuel. Unfortunately, unless a source of lunar water ice is nearby, there would be no hydrogen. Luckily hydrogen is very light, especially compared to oxygen. The Space Shuttle's External tank carries over six times as much oxygen as hydrogen in terms of mass.

Once humans arrive, they can set up more complicated factories that could produce all sorts of useful materials for space exploration from solar panels to fuel tanks to spacecraft hulls.

This would help cheapen the cost of space exploration and possibly even start to turn a profit if other markets are found for lunar products.

The key to space exploration, at least with our government, is to make it cheaper and safer. Martian colony equipment could also be tested on the moon. If it can survive there, Mars will be no problem, and the moon is a safe 3 days away.

pmcolt
2003-Jun-10, 07:48 AM
In The Case for Mars, Zubrin argues that lunar bases would be both uncessary for and harmful to a manned Mars program.

To attempt to sum up his argument in one paragraph: It takes less fuel to go from LEO to Mars than it does to go from LEO to the lunar surface, so the Moon would make a poor refueling base. Lunar and Martian environments are too dissimilar to test Martian hardware at Lunar bases. Funding to support lunar missions would cut into funding to support Mars missions.

I know it would never happen, but I'd like to see active lunar and Martian missions. The same boosters and launch infrastructures could be designed and built for both, and maybe we'd build enough boosters to see economies of scale start to kick in. The moon will be a good base of operations for miners, lunar researchers, and radio astronomers. Mars will be a good place to try to set up a self-sufficient base, experiment with farming on other worlds, and search for evidence of life. Plus it would prove to the world that Americans are perfectly capable of doing two things at once.

Argos
2003-Jun-10, 01:44 PM
Argos, I disagree with you in every way possible. Could you please list some specific reasons as to why you think so?

Bigjim, I was referring to the article ToSeek linked. The so-called Complexity Index.

This makes me wonder if we’ll ever put humans on Mars. The Aerospace Corporation Complexity Index dooms the mission to failure. It would be a genocide case we should attempt today.

What IŽm trying to say here is that a manned Mars mission is far more complex than the sending of probes. The probability of failure is directly proportional to the CI and inversely proportional to the budget available, according to the study of the AC. The combination of high complexity and low budget, typical of the current days, paves the way for a resounding failure. A whole lot of money must be inverted to keep the hazard close to something acceptable. ThatŽs what I meant with “genocide” (a rather strong word, I agree). If you sent men to Mars now, youŽd probably be sending them to death. Remember that the CI puts the Mars Rovers – considered of high complexity - in the failure zone. They are practically failed by anticipation.

When I consider the mass to be conveyed to Mars in a manned mission - a couple of tons I imagine – I also think of the means available: machines that were conceived centuries ago and which were little improved in the last 70 years.

Rockets changed little since Goddard times. The proof is the struggle to send the small Beagle 2. If you were to send a four-people crew, with each astronaut weighing 80 kilos, youŽd have 320 kilos. Supposing that each one will modestly consume 1 kilo of nutrients (food + water) per day during a 3-year trip, weŽd have 1 ton of mass to be conveyed for each astronaut, making up 4 tons, only for basic life support. All this mass would have to be conveyed even if we intended to use local resources after arriving there. IŽm not considering safety margins. If you add fuel and miscellaneous material, youŽll end up with several tons. I really canŽt see how to make it. The plans that include combos like two or three Saturn V only increase the complexity, therefore the risk.

We have reached the limit of physical displacement of humans. Men canŽt go farther than 1 million km from Earth with the means available. WeŽd better roll up the sleeves and start working on relevant technology.

daver
2003-Jun-10, 04:52 PM
ISo what was it that you were saying? :wink:

Hmm, i guess i'm still a curmudgeon. A chemical-powered Mars trip is possible, but i think unlikely. So far NASA has taken no steps towards such a goal. I figure it would take ten-fifteen years of research before we could launch. The first and most obvious step is to build a simulation of the Earth-Mars-Earth vehicle--a rotating tether with a reasonably robust life support system--something that could run for five years or so without resupply (arguably you could get oxygen from the Martian atmosphere, but pretty much everything else you're going to have to carry with you). NASA has little dinky projects on a closed life support system, but so far as i know (which isn't very) nothing that would work for anywhere near the mission duration.

A rotating space station seems a pretty obvious step--we need to know just how big it has to be for the astronauts to be able to function well, we need to know if there are any problems encountered in prolonged exposure to Mars gravity, we need to know what design constraints are important in rotating structures.

It would be nice to put a rotating structure in high earth orbit, so we could see how well the radiation shelter designs work.

Anyway, there are tons more details to be thrashed out. To do so would require setting a long term goal, and sticking to it. I don't see NASA or congress (put the blame where you like it) being able accomplish this without a better reason than we have now. Even the discovery of simple life might not be sufficient. On the other hand, if Hoagland's fantasies had some basis in reality, that would almost certainly provide sufficient motivation.

Anyway, i don't see the US (or any other country, with the possible exception of China) having the foresight and stamina to go for a chemical-powered Mars program with no more motivation than we have now. Nuclear propulsion (particularly high thrust high Isp nuclear propulsion) could change the picture completely.

SollyLama
2003-Jun-11, 05:08 PM
You'll have to add much more weight just in auxillery systems. Like the food and air issue. We can't rely on the prospect of using mars materials too much because it means doom if those systems fail. So I imagine they'll need to take more food and air than those basic minimums.
I think Daver was dead on about a long term committment and the current lack thereof. NASA gets new priorities with every new administration, even every fiscal year.
I'm not yet convinced a manned mission to Mars is going to produce the scientific results that probes will, and we can launch a lot more probes for the cost of a single manned mission- alot quicker too.
Although Apollo was a great achievement, was it really the most efficient way to explore the moon? Not really. I doubt we'll ever see the day where NASA gets such a huge budget or congressional support again, so bang for the buck is more important than footprints in the sand.
I do disagree with China having the foresight to go to Mars, or even the moon for that matter. China is driven by military paranoia at the executive level. Space is a military platform for them, and little else.

daver
2003-Jun-11, 08:31 PM
You'll have to add much more weight just in auxillery systems. Like the food and air issue. We can't rely on the prospect of using mars materials too much because it means doom if those systems fail.
The cheap Mars missions are two-part missions--land the reactor and fuel processor first, don't send the manned mission until your processor has been running for a while. You could run the atmosphere extraction the same way--have one system on the first mission, make sure it's working before launching the manned mission, and bring along a spare just in case.



Although Apollo was a great achievement, was it really the most efficient way to explore the moon?

At the time, yes. Even now, maybe. The moon isn't that far away, the cost penalties of carrying a life support system for a few days are surpassed by the extra flexibility of having a crew on board. Look at how limited Sojourner was, 25 years after Apollo.

Now, if you're just going on a cost basis, the rational thing to do is to stop exploring for a few more centuries until we've developed truly advanced robotics, and maybe some advanced power systems. I'm unwilling to accept that option.



I do disagree with China having the foresight to go to Mars, or even the moon for that matter. China is driven by military paranoia at the executive level. Space is a military platform for them, and little else.

Foresight in the sense of being able to reliably commit to the long-range planning and financing necessary. There's no economic justification for going to Mars, there's a fair amount of scientific justification, there may be an enormous political justification. China may decide that the politcal advantages and their military spinoffs outweigh the economic problems associated with such a program. I don't think any other country has the willpower and the resources to undertake the mission. It also helps that China wouldn't have to sell the program to its people.

BigJim
2003-Jun-11, 09:04 PM
There's no economic justification for going to Mars

The deuterium abundance is five times that of Earth. Even at present launch rates that would be a profitable business. Also, Mars has undergone the same hydrological and volcanic processes that we have, so it undoubtedly has large untouched reserves of gold, platinum, copper, silver - all the metals that are important to civilization and industry. Also, in the long run, the Martians will probably develop many technological advances, which will be driven by need, like the situation in America in the 1700s.


there's a fair amount of scientific justification,

There is a gigantic amount of scientific justification. Mars is a fascinating world, with canyons, gullies, channels, tremendous volcanoes. It certainly had and may still have water. An amazing world with almost unlimited scientific possibilities.


You'll have to add much more weight just in auxillery systems. Like the food and air issue. We can't rely on the prospect of using mars materials too much because it means doom if those systems fail. So I imagine they'll need to take more food and air than those basic minimums.

As daver said, the Mars resources are the beauty of the plan. Before you leave Earth, you have a fully fueled ERV with several tonnes of water and air waiting for you on the surface. If there is a failure, you don't have to go. And there is a backup ERV if the first one fails or you land too far away from it.


(arguably you could get oxygen from the Martian atmosphere, but pretty much everything else you're going to have to carry with you).

With a functioning reactor and chemical plant, it is possible to produce 50 times the amount of oxygen necessary for breathing for all four crew members.




I don't see NASA or congress (put the blame where you like it) being able accomplish this without a better reason than we have now.

Congress.




Even the discovery of simple life might not be sufficient.

On the contrary, that would be more than worth it. By discovering life on Mars, besides knowing that we are not alone and that Mars had an environment conducive to life in the past (or may still have one), it will let us know the differences between what Earth life is and what life is. This would cause revolutions in biology and probably aid in finding cures to disease.


I figure it would take ten-fifteen years of research before we could launch.

A reasonable amount of time.



I'm not yet convinced a manned mission to Mars is going to produce the scientific results that probes will, and we can launch a lot more probes for the cost of a single manned mission- alot quicker too.

Totally disagree. The limitations of Mars robotic exploration have to be placed in context. Robots are fine on Mars for photographic surveys, seismology, meterology, and limited geochemical science. But searching for fossils, let alone extant life, requires intelligence and versality of an entirely different type. Fossil hunting requires heavy work - to do it for real, digging trenches and hammering rocks is required. So is fine work- splitting layers of shale to look for life between layers. It also requires complex perception. Sojourner and Athena have no manipulative capablities. Athena cannot travel over 100 meters a day. Both types of rovers, indeed, most any type of robot would be stopped dead by a boulder field or slope that would easy for a five year old.

Rovers and robots of other types are no substitute for real live scientists. You could parachute thousands of MER-type rovers onto Earth, and it is a fair bet that they might not find any fossils, at least not before the arrival of the next ice age, when they would be crushed by the glaciers which they would not be able to outrun.

Looking for extant life has much greater demands. No robot that will available in the next fifty years will be able to find groundwater or do any serious subsurface studies of Mars, where the life or paast life is likely to be found. First, a spot must be chosen with radar. Then a drilling rig must be set up - and the complex operations required to set one up totally rule out the robots which will be available for at least the next 25 years. And even if a robot could do this, it is doubtful that it could then analyze the life and the context of where it was found. But a human can easily do all of these, and more. A trained geologist's eyes are orders of magnitude beyond what a rover could tell us. Take the Mini-TES instrument on MER. It tells us of the composition of rocks. Now, a trained geologist could operate such an instrument (of far more complexity, owing to the 500 kilogram margin for scientific equipment) and tell us exactly what it was we are looking at. No robot could do that, because robots cannot think.

As a final example, take an Apollo mission, Apollo 15. The entire ALSEP would probably be too complex for modern robots to set up. Could these same robots than explore the region? It is doubtful that such finds as the Genesis rock or things like removing stuck drills from the surface could be done by robots. On Mars, humans will simply be so much better than robots that comparisons become useless. Even collecting samples and core samples on Mars (hundreds of pounds at least) would be far beyond the ability of robots. And could these robots also explore the region, take thousands of pictures, and generally perform all of the scientific functions that humans can?

In a word, no.


Supposing that each one will modestly consume 1 kilo of nutrients (food + water) per day during a 3-year trip, weŽd have 1 ton of mass to be conveyed for each astronaut, making up 4 tons, only for basic life support. All this mass would have to be conveyed even if we intended to use local resources after arriving there. IŽm not considering safety margins. If you add fuel and miscellaneous material, youŽll end up with several tons. I really canŽt see how to make it. The plans that include combos like two or three Saturn V only increase the complexity, therefore the risk.

The Mars Direct plan which I have been talking about allows 7.7 metric tonnes of supplies. The multiple Saturn Vs may add complexity but decrease the risk greatly. If there is not a fully funcitoning, fueled EArth Return Vehicle on the surface of Mars waiting for you, you don't have to go anywhere. Plus there is one following you in case of trouble. The simply work out. Hard to believe, but true. The Hab carries about 3 years of supplies for the entire crew, enough time for a third ERV to be sent out even if both ERVs end up too far away from the Hab. Plus it carries a combustion-power pressurized rover that has a one-way range of 1,000 kilometers, and two open rovers. The scientific potential is tremendous. The fuel, as I explained, is made by the ERV. It's already there, on Mars. No need to haul it out with you. The total weight of the Hab, including the supplies, equipment, and crew, is about 28 tonnes. Within the range of a Saturn V-class vehicle to send out on a 180-day trajectory to Mars.

daver
2003-Jun-11, 10:19 PM
There's no economic justification for going to Mars

The deuterium abundance is five times that of Earth. Even at present launch rates that would be a profitable business. Also, Mars has undergone the same hydrological and volcanic processes that we have, so it undoubtedly has large untouched reserves of gold, platinum, copper, silver - all the metals that are important to civilization and industry. Also, in the long run, the Martians will probably develop many technological advances, which will be driven by need, like the situation in America in the 1700s.


Right now i don't see deuterium mining as providing an economic incentive to go to Mars. I haven't looked into the situation, but the UN is making lots of noise about water shortages. Nuclear desalinators ought do drastically reduce the price of deuterium.

I have some doubts about the availability of minerals on Mars as well. This could be settled relatively cheaply--perhaps it already has and i didn't see the results. It might turn out that the asteroid belt would be a cheaper source of minerals than Mars--if so, it would be cheaper to ship them to Earth directly from the belt rather than to use Mars as a staging or processing area.

BigJim
2003-Jun-11, 10:24 PM
It might turn out that the asteroid belt would be a cheaper source of minerals than Mars--if so, it would be cheaper to ship them to Earth directly from the belt rather than to use Mars as a staging or processing area.

True. Although precious metals and indutrial metals probably are available on Mars, the real mining action will be in the asteroid belt. A "triangle trade" is often discussed between Earth, Mars, and the asteroid belt, in which Earth ships high-tech manufactured goods to Mars, Mars ships low-tech staples of life like food, water, and organic materials to the asteroid belt, and the asteroid belt sends precious metals back to Earth.