Surface centrifugue for a Mars colony

Tom Kalbfus · 2014-01-03 18:24:43

GW Johnson wrote:

Hi Quaoar:
To answer your questions, (1) I think a small-crew base could answer a lot of the adaptation questions in a lot less than 50 years. Although Tom disagrees, I don't think it would take a 100+ population to do most of that. But in practical reality, the adaptation base would slowly grow with time, anyway.
(2) I have come to think in recent months that we ought to start from orbit with smallish landers, and then also go to the surface and establish an adaptation base, all in that first mission. To do that smartly, with maximum probability of success, means that first mission ought to explore multiple sites to get real "ground truth" before establishing the the adaptation base at the "best" one. Multiple landings requires orbital staging (and a reusable one-stage lander), while you need to land everything and everybody at one site to establish a real base of any kind. So, do both in the one mission, as it is very, very, very unlikely in the extreme that a government agency of any nation, or even a consortium of government agencies, will ever fund more than one mission.
Tom disagrees with me, but I don't really believe the private entities will, in the next century or so, establish on Mars any sort of settlement, colony, or even just a base, until the necessary ground truth has been obtained by government(s) to let them plan their enterprise. That's just the nature of private companies, and it has been true for at least 500 years now. (The flip side is that there will be no continuity in the management of that adaptation base if a government mission actually plants one. They will operate it until it is time to come home, and then abandon it, all in the one mission.)
I doubt even Elon Musk will send anything to Mars until either (1) the government pays him to, or (2) the government has found a suitable site and verified ground truth about what resources are really there to use. Which government do I mean? Take your pick. Any or all of them. Doesn't matter. It was like that 500 years ago, too.
As for making ISRU/ISPP work at making propellants, yes I think so, but how good depends upon which one you are really talking about. I think using the Martian atmosphere to make LOX-LCH4 will work, as long as (1) you bring the hydrogen from Earth, or (2) you have an easy source of water at your landing site, and all the means necessary to extract it. I just think it will take years not weeks to accumulate tons of propellant, with any gear we can afford to take there.
If instead you want to use LOX-LH2, your site has to have lots of easy water, or your ISPP cannot work. But solar-powered electrolysis will generate hydrogen and oxygen faster, I think, as long as you can liquify them. Rapid liquifaction is the "long pole" in that tent. In part, because you must store immense volumes of uncompressed gases before running them through the liquifaction plants. "Plants" plural because the equipment to liquify hydrogen gas is quite different from the equipment to liquify oxygen.
Both propellant combinations ultimately require some amount of water. Until we have actual ground truth, we don't know where the water really is, how much there is, what quality it is, or how to transform that which does exist into a usable form. Remote sensing as it exists today cannot answer any of those crucial questions. Neither can zapping surface rocks with a laser, or scratching mere centimeters down with a sampler. You gotta drill 10's to 1000's of meters to find out for sure.
I think I get viewed as a pessimist because I really am an engineer versed in a lot of this stuff. Actually, I am an optimist. But I am also a realist. It's just that everything (in all aspects of life) is always more complicated, and takes longer, than any of us want.
GW

I think any private entity that establishes a colony on Mars would itself become a government. I get tired of space endeavors living on the whim of Congress, government does a lot of stupid and wasteful things, because the people making the spending decisions aren't spending their own money but that of the taxpayers they imperfectly represent. Much the same can be illustrated by the shuttle program, cost was not really a consideration and cutting development costs took priority over cutting operating costs and it turns out that the operating costs were higher, higher even than the Saturn Vs. And if something is expensive, the government doesn't really care, so long as the public doesn't object and the politicians get reelected, they don't care, and with the shuttle going up and down, this discourages private space operators.

You want an example of a government run base? How about McMurdo, Antarctica? There is very little vitality in the McMurdo economy, everyone there is working for the government or is a guest of the government, private development is discouraged, and therefore the base doesn't really grow, it suffers at the whim of Congress.

Last edited by Tom Kalbfus (2014-01-03 18:39:49)

GW Johnson · 2014-01-04 10:56:36

Hi Tom:

Actually I quite agree with you about inefficient government and about the example of the McMurdo base. The inefficient government that is indifferent to costs (except to be penny-wise and pound-foolish for political grandstanding) is exactly why I do not support an SLS done by NASA (it'll never be cheap to fly). As for McMurdo, Mars is much tougher to reach than Antarctica. The problem with McMurdo is that it's too easy to reach: you don't have to abandon it and go home. Any base NASA might establish and then abandon on Mars would be an inviting target for the likes of an Elon Musk. But only if there was some real prospecting done at that base while people were there.

I really do believe that, (1) if NASA ever does go to Mars (and currently they quite evidently do not want to, because none of the necessary things have been happening), and (2) if they actually establish a temporary base there (a really big if, because their entire orientation is toward flag-and-footprints stunts), they will abandon it, precisely because it would be too much expense to support a continuing presence there. There will be one, and only one government-funded mission to Mars, if any at all.

I fear that without a government exploratory mission, private interests will take a very long time indeed going to Mars on their own speculative dollar. Visionaries like Musk and Branson are rare, and would rather be paid to explore than fund it themselves. Exploration has little profit to it. That behavior has been true for centuries, even with visionaries, who are rare indeed. Most of the seriously-monied powerful interests are actually quite brain-dead, as far as progress goes. They got rich and powerful by cheating and picking others' pockets, not by actual speculative investing. Different from, but just as bad as, governments.

The problem is, that if there ever is a government-funded exploration trip, they most likely won't do it right. It'll be a stupid flag-and-footprints stunt, not real exploration. Which is what happened with Apollo on the moon. What we've learned about the moon has come from probes other than the landings, excepting for some few returns from the last 3 landings with the rover cars. But you don't learn a lot about buried resources just scratching around in the surface dust. No drill rig.

GW

SpaceNut · 2014-01-04 21:06:31

The design that I was thinking of is simular to this image

Pictured as soyuz capsule but these could easily be the landers for mars.

RECOMMENDED RESEARCH ON ARTIFICIAL GRAVITY

Tom Kalbfus · 2014-01-05 00:12:57

GW Johnson wrote:

Hi Tom:
Actually I quite agree with you about inefficient government and about the example of the McMurdo base. The inefficient government that is indifferent to costs (except to be penny-wise and pound-foolish for political grandstanding) is exactly why I do not support an SLS done by NASA (it'll never be cheap to fly). As for McMurdo, Mars is much tougher to reach than Antarctica. The problem with McMurdo is that it's too easy to reach: you don't have to abandon it and go home. Any base NASA might establish and then abandon on Mars would be an inviting target for the likes of an Elon Musk. But only if there was some real prospecting done at that base while people were there.
I really do believe that, (1) if NASA ever does go to Mars (and currently they quite evidently do not want to, because none of the necessary things have been happening), and (2) if they actually establish a temporary base there (a really big if, because their entire orientation is toward flag-and-footprints stunts), they will abandon it, precisely because it would be too much expense to support a continuing presence there. There will be one, and only one government-funded mission to Mars, if any at all.
I fear that without a government exploratory mission, private interests will take a very long time indeed going to Mars on their own speculative dollar. Visionaries like Musk and Branson are rare, and would rather be paid to explore than fund it themselves. Exploration has little profit to it.

How did the New World profit the people that explored it, as compared to the people that did not, but could have such as the Chinese for instance?

That behavior has been true for centuries, even with visionaries, who are rare indeed. Most of the seriously-monied powerful interests are actually quite brain-dead, as far as progress goes. They got rich and powerful by cheating and picking others' pockets, not by actual speculative investing. Different from, but just as bad as, governments.

Can you name a billionaire who got rich by picking someone's pocket? I think one can spend all day picking people's pockets and not getting caught and still you will likely not steal enough to send a mission to Mars, as people don't typically carry that much cash in their pockets. You could pick Putin's pocket if you wanted, and I bet you wouldn't get a billion dollars or rubles even from him. You could pick Bill Gates pockets, but I'm pretty sure that the contents of his pocket won't make you a billionaire either, even though he is a billionaire.

The problem is, that if there ever is a government-funded exploration trip, they most likely won't do it right. It'll be a stupid flag-and-footprints stunt, not real exploration. Which is what happened with Apollo on the moon. What we've learned about the moon has come from probes other than the landings, excepting for some few returns from the last 3 landings with the rover cars. But you don't learn a lot about buried resources just scratching around in the surface dust. No drill rig.
GW

GW Johnson · 2014-01-05 10:10:04

"Can you name a billionaire who got rich by picking someone's pocket?" -- how about the several "robber-baron" capitalists of 1860-1910? Might not be "billions", but equivalently-large sums when inflation-corrected. Another single example: tell me the big pharma corporations aren't doing exactly the same thing today, when drug prices in the US are factor-10 higher than in Canada, for exactly the same drugs made by the same companies, on the same production lines? Why? Because they can (money talks very loudly in government). Happens all the time. Has been happening for many, many centuries.

"The design that I was thinking of is simular to this image" -- a wheel station would have been the more useful one to build, although also harder to build. The one pictured appears to have a stationary docking core, requiring a moving joint. If you look at an on-axis enclosed docking bay instead, you need not use a joint. You just match spin to enter and dock, as in the movie 2001 "A Space Odyssey". That does require a larger design to make the gradients in the bay practically nil, but it also provides very low radial gradients out at the inhabited rim. Wheels make great space stations, but not such great ship designs: we need a lot more propellant mass and volume than we do inhabitable mass and volume.

GW

Quaoar · 2014-01-05 12:03:36

GW Johnson wrote:

If instead you want to use LOX-LH2, your site has to have lots of easy water, or your ISPP cannot work. But solar-powered electrolysis will generate hydrogen and oxygen faster, I think, as long as you can liquify them. Rapid liquifaction is the "long pole" in that tent. In part, because you must store immense volumes of uncompressed gases before running them through the liquifaction plants. "Plants" plural because the equipment to liquify hydrogen gas is quite different from the equipment to liquify oxygen.

GW

LOX-LH2 looks particulary actractive for the higher specific impulse(I've seen your modular spaceship uses this kind of propellant, even for the landers).
I've seen NASA has performed a lot of study on Brayton clicle active refrigeration devicies for LH2 (350 ton NTR spaceship Copernicus used only a 920 Kg 9 KW Brayton cooler for her enormous amount of LH2). With this kind of hardware, it may be possible to store LH2 on Mars surface for all the 500 days of the mission?

If so, land on a site like Ice Lake and use LOX-LH2 may be the best choiche for ISPP, even if we limit the in situ production to only liquind oxygen, that is almost 4/5 of the total propellant mass, and bring hydrogen from Earth.

Last edited by Quaoar (2014-01-05 12:06:29)

Tom Kalbfus · 2014-01-06 13:47:21

GW Johnson wrote:

"Can you name a billionaire who got rich by picking someone's pocket?" -- how about the several "robber-baron" capitalists of 1860-1910? Might not be "billions", but equivalently-large sums when inflation-corrected. Another single example: tell me the big pharma corporations aren't doing exactly the same thing today, when drug prices in the US are factor-10 higher than in Canada, for exactly the same drugs made by the same companies, on the same production lines? Why? Because they can (money talks very loudly in government). Happens all the time. Has been happening for many, many centuries.
"The design that I was thinking of is simular to this image" -- a wheel station would have been the more useful one to build, although also harder to build. The one pictured appears to have a stationary docking core, requiring a moving joint. If you look at an on-axis enclosed docking bay instead, you need not use a joint. You just match spin to enter and dock, as in the movie 2001 "A Space Odyssey". That does require a larger design to make the gradients in the bay practically nil, but it also provides very low radial gradients out at the inhabited rim. Wheels make great space stations, but not such great ship designs: we need a lot more propellant mass and volume than we do inhabitable mass and volume.
GW

I don't think every rich person is a criminal, this is a rather unfortunate attitude to have. A rich person could also be one that makes things happen Thomas Edison put light bulbs into everyone's home, Henry Ford put cars in people's driveways, Alexander Graham Bell put phones on desks, they didn't steal, they created markets that didn't exist before and profited from them. We need a similar "Henry Ford" to get us into space.

The main problem with the docking bay of the station of 2001 A Space Odyssey was that is was rectangular, I think a circular docking bay would serve better, and you can have a vehicle that fits neatly into this docking port at the center of the wheel.

Last edited by Tom Kalbfus (2014-01-06 13:52:46)

GW Johnson · 2014-01-09 12:06:32

Hi Tom:

"I don't think every rich person is a criminal, this is a rather unfortunate attitude to have." -- I never said they were. But observation over decades does show that every significant pirate (word choice? those who achieve by depriving others) is rich. That's exactly how they got rich. There are many other rich folks who are not pirates. We have one or two right here in Waco. Good folks, they are.

"The main problem with the docking bay of the station of 2001 A Space Odyssey was that is was rectangular," -- this kind of docking bay mentioned as a concept, not a specification of shape for actual design. Many shapes could serve, and circular is quite probably the easiest to build. Circular would not be the easiest to close, if the bay were to be pressurizable. If not, that one design problem goes away.

GW

Tom Kalbfus · 2014-01-09 12:24:03

The rich, includes those who have managed to avoid market competition, in other words they made a deal with the government so they get a monopoly on whatever is sold. Another way is through patent protection, somebody invents something and files a patent application so that only he has the right to sell something for a given number of years, this is how Thomas Edison made his fortune, the question is do you want modern conveniences or do you just want to prevent people from getting rich. I don't know who the light bulb would have been invented without a lot of entrepreneurs trying to get rich, I don't think a government program could have invented it. A thief is just that, he steals your money while giving you nothing in return, there are many ways to do that, most of them are illegal, this includes printing money as counterfeiting is an indirect form of theft.
A circular opening could be closed wit a hatch or it could simply be a docking port. I think a small space station would more likely have a docking port than a pressurized hangar. Also pressurized hangars tend to waste gas when you depressurize them.

Terraformer · 2014-01-09 16:07:09

Lolwut? You're seriously holding Thomas Edison up as someone who earned his money fairly and never stole anyone's ideas?

There are plenty of people who are rich because the state distorts the market for them...

SpaceNut · 2014-01-09 22:45:04

Lets get back to gravity please....

Only time that we are spinning is when people are onboard and have already done the burn to leave earth orbit and we stop as we approach so as to allow a slowing burn to enter mars orbit.

GW Johnson · 2014-01-10 12:22:29

Spacenut -- my sentiments exactly!

A manned vehicle on a long voyage would have 3, maybe 4, intervals where burns are conducted during the one-way transit. You are not spinning during these burns, you have to eat "astronaut food", and use "zero-gee toilets", and accumulate wastes in a zero-gee holding tank, for those brief intervals of hours to maybe a day.

During the long coast intervals in between, you spin up and enjoy normal Earth food and normal Earth toilets. You do normal Earth cooking. Your waste treatment equipment can be Earth-normal, which is one whale of a lot easier to design and therefore far more reliable.

Antenna pointing problems from a spinning ship can easily be avoided, by a small fly-along antenna module that does not spin, but has a short range omni repeater that you can easily receive in your spinning ship.

The astronaut hab module(s) can be like the Bigelow illustrations we have seen, just with the decks inside rearranged. Because the propellant mass and volume so far exceeds the crew volume, I doubt we are looking at a wheel-shaped hab. That puts us into the baton that spins end-over-end, with the hab at one end. You just use multiple Bigelow-type modules, and trick them out inside differently, to be what they need to be.

If you do it that way (spinning Baton), the decks will be cross section planes inside the cylindrical modules. You size spin rate and radius-from-cg to put 1 full gee at the farthest deck, and make that the day shift work space. There will be a gee gradient radially inward. Make the innermost decks your supplies storage, and the decks just below that sleeping quarters, since sleeping prone confers no gee benefits to health. That might be in the neighborhood of half a gee at the sleeping quarters deck. And that's just fine.

Even untrained civilians can tolerate 3 to 4 rpm long-term. At 4 rpm, the radius to 1 gee is only 56 meters. Given crew sizes of 2 to 6, your ship will likely size out near 150 m long at reasonable baton L/D ratios for a Mars mission. And by "reasonable", I mean structurally-sound: too skinny is too flexible, too weak.

It all works out just fine for a very reasonable rough-out design, actually. We're talking vehicles in the 300-600 ton class for a crew of 6 to Mars, chemical propulsion. Most of that by far is propellant.

Rigid baton vs cable-connected: baton is far more dynamically stable, and easier to control, during spin-up/spin-down operations. The rigid baton encourages modular design, especially with a reconfigurable stack of propellant tank modules. After each burn, you stage-off some empties, and just redock the remaining tank modules to maintain an acceptable baton length at an acceptable L/D and an acceptable spin rate.

A safety consideration: if your baton takes a meteor hit, it doesn't come apart. You just de-spin and patch the hole before you lose all the propellant in the struck tank. If you are cable-connected, and the cable takes a meteor hit, it breaks and you are unrecoverably dead, lost in deep space without propulsion. Also, tanks (and your hab modules) can be covered with foam-and-foil layered meteor "armor" that also doubles as very good insulation. It's hard to imagine how to add meteor armor to a cable.

All those things conspire together to tell me that the spinning baton is the right way to do artificial gravity without building "battlestar galacticas" no one can afford.

To get that same benefit on the surface of Mars, different constraints apply. I haven't thought my way through that problem, but a rotating deck, shaped to a conical angle matched to the spin rate, might be something one could build and operate within some sort of stationary pressurized building. Sort of like a big, slanted, circular moving sidewalk.

The same spin rate limits (3 to 4 rpm max) and gee requirements (one full gee because we know no better) do apply. But for a slanted "moving sidewalk" design, the vector geometry is conical. You get to add the centripetal acceleration to Mars's gravity vectorially. That vector sum should be the one full gee. That vector diagram gives you the right slant angle, too.

GW

Tom Kalbfus · 2014-01-11 15:55:44

SpaceNut wrote:

Lets get back to gravity please....
Only time that we are spinning is when people are on board and have already done the burn to leave earth orbit and we stop as we approach so as to allow a slowing burn to enter mars orbit.

Why enter Mars orbit. The returning Apollo Capsules didn't enter Earth orbit before the splashed down on the Pacific. If there is a Mars Colony, we don't really need to leave a mothership in orbit, we can have unmanned satellites to do all the communications and provide GPS and weather information. I figure that the individual habs simply separate from the wheel the form and each enters the atmosphere and lands separately.

SpaceNut · 2014-01-11 17:53:20

The not so large MAV is not capable to go from mars to earth so we need to leave a return ship in orbit.

Quaoar · 2014-01-12 04:49:10

SpaceNut wrote:

The not so large MAV is not capable to go from mars to earth so we need to leave a return ship in orbit.

When ISPP will be a mature technology, NMHO it will be better to land the whoole ship on Mars, refuel she with local propellant, so she can take-off and came back, saving a lot of mass.
By now we need an almost big orbiting ERV and one or more landers: how suggest GW Johnson in the first mission it may be safer to bring all the propellant for the take-off: ISPP will be only an experiment that can be used to extend exploration via suborbital hoppings, if it will work.

RobertDyck · 2014-01-12 09:58:09

Quaoar wrote:

how suggest GW Johnson in the first mission it may be safer to bring all the propellant for the take-off: ISPP will be only an experiment that can be used to extend exploration via suborbital hoppings

You realize that increases the cost to the point that Congress won't pay for it. The only way Congress will approve any human mission to Mars is if cost is low and controlled. The 90-Day Report was priced at $450 billion in 1989. Congress loudly said "NO!" Constellation is an attempt to resurrect the full 90-Day Report. Robert G Clark has been arguing to go back to the Moon, for everything described in Constellation. But that means everything in the 90-Day Report. When you deduct money for ISS, which is now finished, then apply inflation to today, the 90-Day Report means $750 billion of new money. That 3/4 of a trillion! There's no way Congress would ever approve that!

Mars Direct was an attempt to send humans to Mars on an affordable budget. The price was $20 billion for the first mission, plus $2 billion per mission there after. Or if NASA commits to 7 missions up front, $30 billion. Buy 6 missions, get one free. (Yes it really does work out that way.) One mission every 26 months because that's when orbits around the Sun bring the planets into alignment. So $1 billion per year. That was in 1990 dollars, but still that's a lot better. In fact, since technology has advanced and we now have "New Space" companies, the price may end up the same. But when NASA was finally convinced to take Mars Direct seriously, they decided to re-invent it. They bulked it up from 4 crew to 6, and brought propellant for return all the way from Earth. It only uses ISPP for the Mars Assent Vehicle, to go from Mars surface to Mars orbit. That was the NASA Design Reference Mission (DRM). It was priced at $55 billion for 7 missions. Congress noticed the price jumped from $20 billion to $55 billion already, and they haven't even finished designing the thing. That convinced them NASA would end up demanding the full 90-Day Report, with it's gigantic price tag, so they said "No".

That is the reason Congress continues to refuse to allow any humans beyond Low Earth Orbit. They're afraid that any attempt to do so would result in the full price tag of the 90-Day Report. They are not ever, ever, EVER going to authorize that much money. Not anywhere near that much money.

Go cheap or go home.

Quaoar · 2014-01-12 11:29:37

RobertDyck wrote:

Mars Direct was an attempt to send humans to Mars on an affordable budget. The price was $20 billion for the first mission, plus $2 billion per mission there after. Or if NASA commits to 7 missions up front, $30 billion. Buy 6 missions, get one free. (Yes it really does work out that way.) One mission every 26 months because that's when orbits around the Sun bring the planets into alignment. So $1 billion per year. That was in 1990 dollars, but still that's a lot better. In fact, since technology has advanced and we now have "New Space" companies, the price may end up the same. But when NASA was finally convinced to take Mars Direct seriously, they decided to re-invent it. They bulked it up from 4 crew to 6, and brought propellant for return all the way from Earth. It only uses ISPP for the Mars Assent Vehicle, to go from Mars surface to Mars orbit. That was the NASA Design Reference Mission (DRM). It was priced at $55 billion for 7 missions. Congress noticed the price jumped from $20 billion to $55 billion already, and they haven't even finished designing the thing. That convinced them NASA would end up demanding the full 90-Day Report, with it's gigantic price tag, so they said "No".
That is the reason Congress continues to refuse to allow any humans beyond Low Earth Orbit. They're afraid that any attempt to do so would result in the full price tag of the 90-Day Report. They are not ever, ever, EVER going to authorize that much money. Not anywhere near that much money.
Go cheap or go home.

If we want to go direct, we have to realy on a working technology so we have to build a Sabatier-reverse gas shift prototipe, run it in facility replicating the atmosphere of Mars and try to reach 10 metric ton of LOX-LCH4 in 30 days, with a power supply similar of spaceship PV array.

When all the problems will be fixed and the ISPP machine will work perfectly and we are sure we can realy on it, we can send an unmanned 20 ton ERV on Mars: if the ISPP machine will be able to produce 80 ton of LOX-LCH4 almost a year, we will send the crew.

The only way to be sure ISPP machine will work is to test it on Earth in an environment similar of Mars.

An alternative may be to use a LOX-LH2 ERV, and use a well known ice pack, like Ice Lake Crater, to get the water for the ISPP. Ice melting and water electrolysis are simpler technologies, LOX-LH2 has the highest Isp and LH2 can be stored for long times with an active cooling system (if producing LH2 is too difficolut, we can bring LH2 from Earth and use alectrolysis to make only LOX).

I

Last edited by Quaoar (2014-01-12 11:32:24)

RobertDyck · 2014-01-12 12:06:16

It has already been tested with a small unit at Pionerr Astronautix. This is called a "brass board" because the plumbing is brass, and it's small. It was tested with a bottle of gas that has the exact same composition as the atmosphere of Mars. It worked. The next test would be to scale it up to the size needed for Mars; as you suggest.

Mars Direct was designed to use the SP-100 nuclear reactor. This was already designed by the US military, as part of Ronald Regan's SDI program (Star Wars). A full-size prototype had already been built, it was proven. So the reactor was ready in 1989.

Mars Direct had the ERV delivered unmanned to the surface of Mars. It would produce propellant, when the tanks were full it would send a radio signal to Earth. Only then, only when the ride home was secure, would astronauts leave Earth.

Quaoar · 2014-01-12 12:32:12

RobertDyck wrote:

It has already been tested with a small unit at Pionerr Astronautix. This is called a "brass board" because the plumbing is brass, and it's small. It was tested with a bottle of gas that has the exact same composition as the atmosphere of Mars. It worked. The next test would be to scale it up to the size needed for Mars; as you suggest.

Zubrin's demostrator used a CO2 cilinder: before sending the ERV, we need a working, reliable and fully developed ISPP machine, able to get CO2 from a thin atmosphere like on Mars and produce almost 250 kg/day of LOX-LCH4, working continously for almost 300 days, without failure.

RobertDyck wrote:

Mars Direct was designed to use the SP-100 nuclear reactor. This was already designed by the US military, as part of Ronald Regan's SDI program (Star Wars). A full-size prototype had already been built, it was proven. So the reactor was ready in 1989.

It would be the best solution, but how to explain it to politicians, afraid to lose the votes of ecologiests?
If we will ever go on Mars, we will realy only on solar panels.

RobertDyck wrote:

Mars Direct had the ERV delivered unmanned to the surface of Mars. It would produce propellant, when the tanks were full it would send a radio signal to Earth. Only then, only when the ride home was secure, would astronauts leave Earth.

This is safe, but if something brokes there is nobody to fix it, even is a very stupid failure like an obstructed filter. This is the drawback. So an unmanned spaceship needs a very very reliable propellant production plant.

I'm not an expert, but why not to get LOX-LH2 from ice?

Last edited by Quaoar (2014-01-12 13:40:28)

RobertDyck · 2014-01-12 16:37:57

Quaoar wrote:

Zubrin's demostrator used a CO2 cilinder

His Sabatier used a CO2 cylinder. He also got a Small Business contract with NASA for MACDOF: Mars Atmosphere Carbon Dioxide Freezer. It started with the same mixture as Mars atmosphere, isolating CO2.

Quaoar wrote:

It would be the best solution, but how to explain it to politicians, afraid to lose the votes of ecologiests?
If we will ever go on Mars, we will realy only on solar panels.

Old argument. A few years ago Congress was beginning to realize no nuclear = no space.

Quaoar wrote:

This is safe, but if something brokes there is nobody to fix it, even is a very stupid failure like an obstructed filter. This is the drawback. So an unmanned spaceship needs a very very reliable propellant production plant.

Don't send humans unless you get the radio signal that everything with the ERV is working perfectly. And Mars Direct includes a second ERV, following the crew and their habitat. If anything goes wrong, the second ERV will land beside the crew. If all is Ok, then land the second ERV where your next mission will go. That starts the second mission. I could describe my mission plan, but this is Mars Direct.

Quaoar wrote:

I'm not an expert, but why not to get LOX-LH2 from ice?

No proven ice deposit anywhere we would send humans. Even GW Johnson says we can't rely on ice for the very first human mission. But you can rely on atmosphere. Using Zubrin's ISPP is far better than trying to bring return propellant from Earth.

There is ice at Vastitas Borealis Crater, but that's 70° north. Mars Direct has the crew stay 14 months on the surface (about 425 days), waiting for the planets to align for the return home. That's so much time that winter will fall. Mars gets very cold at night, but winter near the pole? Temperature will get so cold that you have to worry about material embrittlement. Much better to stay near the equator, where it's cold, but not that extreme. In other discussion threads we have discussed the spot on Elysium Planitia called "Frozen Sea" or "Pack Ice". It looks good, and radar from orbiters confirm layers, but have not confirmed ice. SHARAD on MRO confirms layers, but does not say what the layers are. Results from MARSIS on Mars Express do not have the dielectric expected for water ice. That could mean all the ice has evaporated/sublimated, or it could mean remaining ice is too shallow for that. They did confirm the dielectric for the south polar ice cap, but that is 3.7km thick! The "Frozen Sea" was 45 metres deep, but at least some has evaporated/sublimated. Is it all gone, or just too shallow for MARSIS? We'll have to drill to find out. Only 5° north of the equator (warm), low altitude (lots of atmosphere for radiation shielding), and flat/smooth (safe to land), so it's a really great spot; but you don't want to bet your life on ice just to find it's all gone.

Last edited by RobertDyck (2014-01-12 16:38:45)

Quaoar · 2014-01-13 03:21:39

RobertDyck wrote:

Old argument. A few years ago Congress was beginning to realize no nuclear = no space.
.

In this case, the game will change. With an affidable nuclear reactor and a reliable working ISPP machine we can produce tons of LOX-LCH4, enought to fill the tanks of an ERV of the right size to support a 4-6 crew for six month.

http://spaceref.com/nuclear-propulsion/ … otype.html

This new version utilizes sterling generators instead of termionic conversion of SP-100 and reach 500 Kw. It may be able to fill the tanks of a very comfortable ERV. But we have to start now in building a full scale prototype of ISPP machine and develop it

But I remember the protests for the RTG of Cassini...

RobertDyck wrote:

No proven ice deposit anywhere we would send humans. Even GW Johnson says we can't rely on ice for the very first human mission. But you can rely on atmosphere. Using Zubrin's ISPP is far better than trying to bring return propellant from Earth.
There is ice at Vastitas Borealis Crater, but that's 70° north. Mars Direct has the crew stay 14 months on the surface (about 425 days), waiting for the planets to align for the return home. That's so much time that winter will fall. Mars gets very cold at night, but winter near the pole? Temperature will get so cold that you have to worry about material embrittlement. Much better to stay near the equator, where it's cold, but not that extreme. In other discussion threads we have discussed the spot on Elysium Planitia called "Frozen Sea" or "Pack Ice". It looks good, and radar from orbiters confirm layers, but have not confirmed ice. SHARAD on MRO confirms layers, but does not say what the layers are. Results from MARSIS on Mars Express do not have the dielectric expected for water ice. That could mean all the ice has evaporated/sublimated, or it could mean remaining ice is too shallow for that. They did confirm the dielectric for the south polar ice cap, but that is 3.7km thick! The "Frozen Sea" was 45 metres deep, but at least some has evaporated/sublimated. Is it all gone, or just too shallow for MARSIS? We'll have to drill to find out. Only 5° north of the equator (warm), low altitude (lots of atmosphere for radiation shielding), and flat/smooth (safe to land), so it's a really great spot; but you don't want to bet your life on ice just to find it's all gone..

First mission may land in Elysium Planetia with enough hydrogen to produce the return propellant and drill to find water: if they find they can use it to produce more fuel for the rover fuel cell and extend exploration. If they don't find, they can still came back, but they cannot build a reliable base in that place.

Supponing the worst case there are not reliable water sources in low latitudes, we will be forced to reconsider the whoole colonization program.
Without a reliable source of water in low latitudes, we are forced to put our base in higher latitude and learn how to deal with martian winter (with a 500 Kw nuclear reactor, heating the habitat would not be a big problem).

Last edited by Quaoar (2014-01-13 16:58:02)

SpaceNut · 2014-01-13 12:49:13

Quaoar wrote:

SpaceNut wrote:
The not so large MAV is not capable to go from mars to earth so we need to leave a return ship in orbit.
When ISPP will be a mature technology, NMHO it will be better to land the whoole ship on Mars, refuel she with local propellant, so she can take-off and came back, saving a lot of mass.
By now we need an almost big orbiting ERV and one or more landers: how suggest GW Johnson in the first mission it may be safer to bring all the propellant for the take-off: ISPP will be only an experiment that can be used to extend exploration via suborbital hoppings, if it will work.

The Mav is a tiny capsule unfit for a six month journey to earth, it has no Earth entry heats shield as it would be heavy and not needed to be landed on mars, no parachutes for earth entry as the ones needed for mars entry have already been used. Then the stage to push the mav to Earth from mars orbit just made it not possible to land on mars. We do have size limitation of mass and diameters to work with.

Quaoar · 2014-01-13 16:26:22

SpaceNut wrote:

The Mav is a tiny capsule unfit for a six month journey to earth, it has no Earth entry heats shield as it would be heavy and not needed to be landed on mars, no parachutes for earth entry as the ones needed for mars entry have already been used. Then the stage to push the mav to Earth from mars orbit just made it not possible to land on mars. We do have size limitation of mass and diameters to work with.

You can build it as a two stage vehicle: the landing stage with thermal shield and retrorocket, and a small capsule with a couple of rocket as ascent stage. If the orbiting ship use LOX-LH2 plus aerocapture on Mars insecrction and aerocapture and/or aerobrake on Earth return, the total mission delta-V is less than 7 km/s in the worst case scenario (Erath perielium - Mars aphelium) and the propellant mass is not so prohibitve: a 20 mT ERV can perform the whoole mission with less than 80 mT of propellant. We can also save a lot of money making the ERV fully reusable.

Last edited by Quaoar (2014-01-13 16:27:46)

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