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View Full Version : The Mars Landing Approach: Getting Large Payloads to the Surface of the Red Planet



Fraser
2007-Jul-18, 03:04 AM
Some proponents of human missions to Mars say we have the technology today to send people to the Red Planet. But do we? Rob Manning of the Jet Propulsion Laboratory discusses the intricacies of entry, descent and landing and what needs to be done to make humans on Mars a reality. ...

Read the full blog entry (http://www.universetoday.com/2007/07/17/the-mars-landing-approach-getting-large-payloads-to-the-surface-of-the-red-planet/)

Doctor Know
2007-Jul-18, 06:27 AM
Ironic to find that the thin, rarified atmosphere of Mars presents a trickier descent problem than a thick atmosphere or no atmosphere at all. Ironic in that you have nearby Venus which has a plenty thick (and toxic) atmosphere, and no one is currently interested in future manned exploration there for obvious reasons.

thothicabob
2007-Jul-18, 06:59 AM
Yep. I have to admit, it was a bit of a surprise to find out that not a lot of work's been already done on that problem (well, okay...some work has been done, obviously, but - for how many years have we speculated on going to Mars, and that issue's not been taken towards a solution yet?).

Maybe it's easier and more economical to send the ship in with a relatively hard landing, with the astronauts ejecting from the craft just before the final descent stage (but after dropping well below supersonic speed) and drop in with parachutes and jetpacks. :) That sure would be a dramatic entrance!

...and if they could be wearing tuxes on the outside of their spacesuits, just for a touch of flair... :shifty:

antoniseb
2007-Jul-18, 06:08 PM
Mars is probably a better candidate location for the first "Space Elevator" than the Earth is:
- The total gravity well is smaller, meaning that CNT would work there.
- There is less orbital debris to avoid
- There are fewer lightning storms to combust the tether
- There is no free oxygen in the atmosphere to aid combustion
- The planet's rotation rate is about the same as Earths

This won't help with the first mission, but it will help get the masses down to the planet.

KrispE
2007-Jul-18, 08:24 PM
How about a tether from one of the moons?:think:

antoniseb
2007-Jul-19, 11:50 AM
How about a tether from one of the moons?:think:
Hi KrispE, welcome to BAUT. A tether from one of the moons would be problematic since the moons are not stationary over a place on the Martian surface. Getting off the tether would mean landing with a high horizontal velocity.

thothicabob
2007-Jul-19, 04:28 PM
Hi KrispE, welcome to BAUT. A tether from one of the moons would be problematic since the moons are not stationary over a place on the Martian surface. Getting off the tether would mean landing with a high horizontal velocity.

That just makes it all the more exciting; heck, what else is anybody gonna do there on weekends (or any other day, for that matter)?

Space elevator IS one idea though. Perhaps moving one of the smaller ones into a stable geosynchronous orbit to serve as the space anchor would wind up being more efficient/cost-effective than launching sufficient mass for one and building it...? Hmm. At 2.244×10^15 kg and about 12km across...maybe about 500 Saturn V boosters at full thrust for about 20 years may do it...? (just a rough guess...I didn't do the math). :)

KrispE
2007-Jul-19, 04:34 PM
"High horizontal velocity"--how high? How about a moon on one end, and a glider on the other end of the tether skimming through the atmosphere as a starting point of descent. Better yet a pendulum with a stationary touchdown point. Thanks for the welcome to BAUT. I'm a total amature when it comes to astronomy.

antoniseb
2007-Jul-19, 08:02 PM
"High horizontal velocity"--how high?
For Phobos (the inner moon) it would be about 2000 miles per hour. For Deimos (the outer moon it would be about 150 miles an hour, the other way), but Phobos would sometimes get in the way.

Igor
2007-Jul-19, 11:07 PM
I respectfuly believe that rocket powered human space travel has only been
demonstrated as far as the Moon and that this is the limit of its potential period- we have not gotten any further in 35 years and we never will. The
next step, if it were to be possible, is electromagnetic propulsion relying on
rechargable nuclear batteries and the electromagnetic solar sail and while
this does involve moraly new technology which is hard to develop but it
is our only hope for human travel to Mars and the worlds of the Solar System.
I have been trying to push this technology development for years but so far
nobody wants to take me seriously- they think there will be sufficient space
tourism market to Earth orbit and the Moon only. I do not. Any comments,
folks?

Sincerely

Igor Zilist

tsmund
2007-Jul-19, 11:16 PM
It seems that it is an obvious requirement, although not a solution in itself, to break down the payload, or payloads, into smaller masses that are the most easily deliverable to and from the surface. Perhaps each astronaut, or pair of astronauts, and modularized payload components, could be sent separately to the surface from an orbital platform.

Also, payload should be sent and automatically deployed with confirmation before the crew even leaves the earth to eliminate sharing the risk imposed by payload requirements with the risk to the crew. This would also prevent a fatal failure of vital payload deployment from endangering, or worse, dooming the crew members. The crewship should be composed of only that which is required to sustain and deliver them. Another way of looking at it is to put the payload on a longer timeline and the crew on a shorter one.

Yes, this would extend the total timeline and be more expensive, but the expense would be spread out over time also. Leave the brain-busting problem of getting the whole ball of wax to the surface quickly for our ancestors.

Small moves, folks.

thothicabob
2007-Jul-20, 01:59 AM
It seems that it is an obvious requirement, although not a solution in itself, to break down the payload, or payloads, into smaller masses that are the most easily deliverable to and from the surface. Perhaps each astronaut, or pair of astronauts, and modularized payload components, could be sent separately to the surface from an orbital platform.

Well, yeah. That's what I said. ;o)

Thanks for taking it seriously...


Also, payload should be sent and automatically deployed with confirmation before the crew even leaves the earth to eliminate sharing the risk imposed by payload requirements with the risk to the crew. This would also prevent a fatal failure of vital payload deployment from endangering, or worse, dooming the crew members. The crewship should be composed of only that which is required to sustain and deliver them. Another way of looking at it is to put the payload on a longer timeline and the crew on a shorter one.

This is eminently sensible, and not a solution/suggestion I recall seeing associated previously with an expedition to Mars. I'd do some checking first, but if it turns out to BE the case it's not one of the models being considered, I'd suggest recommending it. Seriously.



Yes, this would extend the total timeline and be more expensive, but the expense would be spread out over time also. Leave the brain-busting problem of getting the whole ball of wax to the surface quickly for our ancestors.

I am not so sure the thing would necessarily be more expensive, in the long or short run. It could simplify design considerably, and other factors I've not had to think about could add efficiencies and reduce overall cost.

More time? Sure, but not that much more, and the time would be worth it (well, it may put seeing men step on Mars out of reach for me - it's already going to be close as it is...if it happens, but I'm not quite SO arrogant as to expect them to factor that into their planning). :)


Small moves, folks.

Right...I'll leave that opening be for now. :)

ColonyWorlds
2007-Jul-20, 04:12 AM
From antoniseb

Mars is probably a better candidate location for the first "Space Elevator" than the Earth is:
- The total gravity well is smaller, meaning that CNT would work there.
- There is less orbital debris to avoid
- There are fewer lightning storms to combust the tether
- There is no free oxygen in the atmosphere to aid combustion
- The planet's rotation rate is about the same as Earths

I'd agree with you if it were not for those global dust storms (http://www.space.com/scienceastronomy/solarsystem/mars_storm_update_011011.html) that can happen every three Martian years (http://www.foxnews.com/story/0,2933,288254,00.html).

Although a skyhook from Phobos may be more realistic.


From tsmund

It seems that it is an obvious requirement, although not a solution in itself, to break down the payload, or payloads, into smaller masses that are the most easily deliverable to and from the surface. Perhaps each astronaut, or pair of astronauts, and modularized payload components, could be sent separately to the surface from an orbital platform.

That's actually a really good idea! Although I have a feeling that Congress would lack the patience for this endeavor. :cry:

What about skipping Mars for Ganymede? At least we wouldn't have to worry about solar radiation from sun spots. ;)

ndgbrown
2007-Jul-20, 07:52 AM
The question is how do we land on mars with such large weights
Is it possible to lower into the atmosphere a vehicle such as an air ship that while in space and on its journey to Mars is empty of any gases but a vacuum,
I am talking af an air ship the size or up to the size of the Hindenburg that is attached to another vehicle that transports it to the planet and is then lowered not onto the surface of Mars but only into the upper atmosphere, then gas tanks would fill the chambers of the vessel as it is lowered, this would possibly get some heavy equipment to the surface, If your lowering something into the atmosphere you can do away with heat shields.
this may not be so good for retreval

thothicabob
2007-Jul-20, 08:15 AM
The question is how do we land on mars with such large weights
Is it possible to lower into the atmosphere a vehicle such as an air ship that while in space and on its journey to Mars is empty of any gases but a vacuum,
I am talking af an air ship the size or up to the size of the Hindenburg that is attached to another vehicle that transports it to the planet and is then lowered not onto the surface of Mars but only into the upper atmosphere, then gas tanks would fill the chambers of the vessel as it is lowered, this would possibly get some heavy equipment to the surface, If your lowering something into the atmosphere you can do away with heat shields.
this may not be so good for retreval

One problem is slowing it down from about 10,000 mph to about 200 mph within a span about 5-10 minutes, i think. Otherwise...well, Hindenberg does sort of ring bells here... :)

Another one - an airship would likely need to be at least 100 times the volume of the Hindenberg to carry anything like 40 tons in the Martian atmosphere...and probably a lot bigger. The atmosphere, tho it exists, is negligible for such purposes. That's also the problem with parachutes...they have to be VERY big to have much of an effect even to slow something down, let alone land something heavy gently on the ground.

Just my guesses, but I think not bad ones...for starters.

Ronald Brak
2007-Jul-20, 08:24 AM
Sending cargo first and only sending humans when the solar panels, CO2 cracker, dune buggy, ascent module and so on are all on the ground and operational seems like a very good idea. The dune buggy might have to be one of the first items as it will have to travel around and pick up items that will no doubt be spread out over a wide area. Then it can set up the base camp and wait for humans to arrive.

thothicabob
2007-Jul-20, 08:29 AM
I agree. It seems a very reasonable, safe, and efficient idea.

And...it keeps open the possibility for my idea of the astronauts arriving with parachutes and jetpacks. I may have to drop the tuxedo bit, but that was only for flair, anyway. :)

ndgbrown
2007-Jul-20, 10:12 AM
Ok I was referring to slowly lower a Hindenburg size ship into the atmosphere by tether not drop it, and I think we have come a long way in technology since painting the Hindenburg with explosive paint, we don,t need to lower 40 tones at once, that is just a figure that NASA would like to be there eventually, the ship doesnt even have to be maned, we are already using UAV's. all we need is to get equipment safely to the ground and have it assembled ether by robots or by man once there are enough parts, the air ships alone could be used to get accommodation to the surface, look at the high altitude balloons that can carry capsules, obviously we need something bigger than a capsule, but there is no need for it to be heavy ether, its not going to be used in space, astronauts can get there similarly, a lot of equipment will need to be there first, and much of it would be back up equipment for the just in case scenario, I'm sure a light wing aircraft could also be lowered into the atmosphere too, NASA have talked about using UAV's on mars

crosscountry
2007-Jul-20, 10:53 AM
It seems that it is an obvious requirement, although not a solution in itself, to break down the payload, or payloads, into smaller masses that are the most easily deliverable to and from the surface. Perhaps each astronaut, or pair of astronauts, and modularized payload components, could be sent separately to the surface from an orbital platform.

Also, payload should be sent and automatically deployed with confirmation before the crew even leaves the earth to eliminate sharing the risk imposed by payload requirements with the risk to the crew. This would also prevent a fatal failure of vital payload deployment from endangering, or worse, dooming the crew members. The crewship should be composed of only that which is required to sustain and deliver them. Another way of looking at it is to put the payload on a longer timeline and the crew on a shorter one.

Yes, this would extend the total timeline and be more expensive, but the expense would be spread out over time also. Leave the brain-busting problem of getting the whole ball of wax to the surface quickly for our ancestors.

Small moves, folks.


I really think it would be better to send the supplies well in advance. Once we are sure it is there and healthy we can send humans. That saves breaking up the team and it insures that all the supplies are ready when they land - hopefully nearby. Although I doubt we'll have a location problem by the time we get there.

Argos
2007-Jul-20, 01:21 PM
I´d say an orbital mother-ship/landing capsules combo would be the best alternative. But of course they must have thought about that...

GOURDHEAD
2007-Jul-20, 01:59 PM
If we had the wherewithal to add a couple of bars of atmosphere (Venus has more than we would like it to have), even if it were mostly CO2, it would make powered landing with parachute assistance much more likely attainable. Even so, I prefer powered landing in the current atmosphere of Mars. A major problem with powered landings would be the dust stirred up in the atmosphere local to the landing vehicle and suspended in the thin Martian atmosphere. The initial landing site should be on barren rock or the ice fields at one of the poles. I prefer the latter and to support initialization of site setup, I prefer the pole that is in summer. This would provide daylight long enough to set up several photovoltaic panel receiving stations such that at least one would be in sunlight during worst conditions. Also, water and CO2 ice would be available for their appropriate uses. Once we establish "around the clock" power availability, we can expand toward the equator from each pole and add supplemental fission power sources as needed. Melting the ices would provide material for the bioreactors needed for food production and the generation of oxygen. The "surplus" water and CO2 could be piped to new locations in hermetically sealed systems as we move toward the equator to supply additional bioreactors for more food production and water distribution.

My guess is that the Mars lander(s) for humans and heavy equipment would be transported to Mars in several missions and asembled in Martian orbit, or launched from Earth without a load, or with minimal load, and loaded in Martian orbit for the landing. It would be nice to be able to test its landing capability prior to delivering its load to the Martian surface, but I haven't figured out how to do this short of a few unhumanned landings (equipment only) at Mars.

thothicabob
2007-Jul-20, 05:58 PM
If we had the wherewithal to add a couple of bars of atmosphere (Venus has more than we would like it to have), even if it were mostly CO2, it would make powered landing with parachute assistance much more likely attainable.

Although I do like the idea of terraforming Mars at some point in the future, that's a pretty complex and time consuming undertaking - not something I think we'll even seriously begin to consider for at least 2 or 3 generations after we first get there. Personally, I'd be thinking about it now if I ran NASA (in an institutional sense), but then again, they have limited budgets and resources and its priorities are set more by politics and funding rather than the "ideals" of exploration and human habit expansion.

The biggest issue there (terraforming mars) would be, as you suggested, getting the atmosphere a bit more robust so a decent temp and pressure could be maintained to allow for liquid water, and I think that that's doable, perhaps even within a reasonable time frame, given the resources to _really_ take the "Nike approach".

But if you want surface life of any sort, you're going to also have to figure out some way to generate a magnetic field around the planet, too. That may prove to be a bit of a more difficult nut to crack in practical terms.

And in any case, setting the processes in motion to create a sustainable biosphere may not be very easy...it's a pretty complex thing in itself, and likely a lot of counterintuitive suprises could be in store there that probably would make getting an initial payload to the surface seem like a kindergarten exercise (which, in a contextual sense, it IS!). :)

Svemir
2007-Jul-20, 10:57 PM
Shoot a couple (1000) of asteroids (comets for water purposes?) at Mars.
Mars gets mass, gets warmer (magnetic field and tetonics?) with heavier atmosphere.
Spread some bacteria (designed?) and other plants seeds, sit back and wait 50 000 years or so.

thothicabob
2007-Jul-20, 11:52 PM
Well, not far off, except for the magentic field bit, I think - I somehow don't think you'll heat the planet up quite enough to re-melt the core sufficiently to strengthen the magnetic through cometary impacts on the surface. Not really sure what to do about that.

I sorta wonder how many comets it WOULD take to get the atmosphere in better shape - maybe dozen or two fair-to-middlin'-sized ones spaced over a relatively short time frame? There's a lot of water locked just below the surface, too; I don't know that it's been quantified yet - but if you can get enough of it melted (in part through the comet impacts themselves), maybe geting enough greenhouse gas in the atmosphere to warm things up enough, it COULD kick off a warming cycle. Of course, a lot of dust in the atmosphere could wind up being being helpful, too - or counter-productive to the process.

Then, perhaps spinkle some genetically engineered algae in the lakes and seas, some nice aggresive shrubbery on land, and ... heck, maybe you won't need to wait 50k years...! All we want to do is make things a bit more comfy, not get some native martian ecosystem evolving before moving in, right?

The trick will be the comets, but then, come to think of it - if we get to a point where we can move multi-billion/trillion/quadrillion ton comets around the solar system, would landing a few chunks of metal and biomass mars be that big a deal? Anyway, I'm no planetary engineer, and I'll bet it's painfully obvious I'm not likely ever gonna be one; I'm just doing the equivalent of pretending to a rock star through playing an air guitar, I guess... :)

general_fault
2007-Jul-21, 02:46 AM
The best mars landing sequence:
1. Put a pair, make it 2 pair of gps on mars orbit. Map the surface and test a gps beacon locator device.
2. Built the mothership for equipment and crew. Go to mars and orbit it.
3.deploy the equipment using gps beacon and parachutes.
4. Crew go to mars orbit on small space shuttle, collect equipment and built mars settlement.

Tom2Mars
2007-Jul-21, 03:50 AM
With a low enough density lander, anywhere is a good site, the lander will slow down enough and be able to land on a dime. Getting there... no problem, landing... no problem, sustaining life support... well, if you can demonstrate that on Earth, then, no problem on Mars. I've already demonstrated that here on Earth, so that is no problem. You want to go to Mars?? Then, let's go!!!!!!!!!!

thothicabob
2007-Jul-21, 03:59 AM
Oh blah, blah, blah. With a low enough density lander, any where is a good site, the lander will slow down enough and be able to land on a dime. Getting there... no problem, landing... no problem, sustaining life support... well, if you can demonstrate that on Earth, then, no problem on Mars. I've already demonstrated that here on Earth, so that is no problem. Whine, whine, whine, I am so tired of all the whining. You want to go to Mars?? Then, let's go!!!!!!!!!!

"Low enough density lander" implies a pretty large lander in terms of size/volume. Regardless of your approach, there are likely a lot of engineering issues you'll have to deal with to get enough equipment there.

I think chunking the problem up and doing it in parts is likely the easiest, most efficient way to deal with it. Land the equipment first, the fragile people second (there's your reasonable-sized low-density lander).

I agree with the point - Let's just do it!

Tom2Mars
2007-Jul-21, 04:28 AM
Here is an appropriate and interesting article by James Oberg, for the Air & Space Magazine, from 2003,
http://www.jamesoberg.com/112003irv_his.html
It is not too difficult to reduce density. It is not too difficult to reduce density in a vehicle at all. Just increase the diameter of the vehicle by a factor of 2, and the density is reduced by a factor of 4. Simple math.

thothicabob
2007-Jul-21, 04:49 AM
Here is an appropriate and interesting article by James Oberg, for the Air & Space Magazine, from 2003,
http://www.jamesoberg.com/112003irv_his.html
It is not too difficult to reduce density. It is not too difficult to reduce density in a vehicle at all. Just increase the diameter of the vehicle by a factor of 2, and the density is reduced by a factor of 4. Simple math.

Umm, I do get that. It's pretty clear/obvious. But the issue is, getting enough mass to the ground in one go would require a VERY large vehicle. And density is not the only consideration. you DO have to decelerate from orbital speeds, get through an atmosphere dense enough to cause problems, but not enough to support much in the way of controlled aerodynamic flight.

So, in addition to being of low density, it has to be of high strength, heat resistant, able to deal with radiation effectively. you have propulsive systems and their fuel, equipment and supplies for an extended stay...

In short, a lot of things to include in this low-density lander. I do agree - it's a good approach, and it would also make a good shelter. But it's not just a matter of saying "let's make a dirigible-like lander and do it". At least, I don't think it'd be that easy.

Ok, now to read what Dr. Oberg has to say...

thothicabob
2007-Jul-21, 05:03 AM
Just read the Oberg story. Interesting.

One question: with the Martian atmosphere at the surface being at best about 1 percent of the earth's you would need a HUGE 'IMP'-like structure to carry ANY sort of payload successfully to the surface. The Martian surface is not all that bouyant. Also, it's not also very effective for aerobreaking purposes either.

I'll assume you read the story associated with the OP for the thread, so you know the issues presented. Now, I'm not qualified to make any authoritative determinations in this area, so feel free to blow me off (you'll not be the first, so I'm not worried about my feelings getting hurt - I'm pretty thick-skinned (or thick-headed) in that sense), but I think that such an approach would have as many, if not more, engineering problems associated that would need solving, would likely be pretty complex, and subject to huge inherent risk. It is interesting, though - and I DO like the idea of having a large shelter on the ground for a habitat; I just think they'd be better off blowing one up once there. :)

I still think tsmund's idea to be the best and most practical - and something we could do relatively easily with current technology and engineering knowledge; I think each of the issues it addresses are things we can solve separately pretty easily, eg. getting a largish set of payload on the ground and getting people on the ground. It's combining them that makes it harder. Splitting them up makes sense.

crosscountry
2007-Jul-21, 09:32 AM
you guys must be talking about future missions. I've already told you how they are going to do the first one and probably several more.


They will shoot some habitat and supplies from Earth to Mars a year or so in advance. This will contain enough supplies for the astronauts to land and live for some months plus take off again later. Once this habitat and lander (possibly more than one) have been checked by robots and cameras, and only then, will we send people.

Those people will then leave Earth in direction Mars. They will park in orbit some mothership with enough fuel to come home plus the supplies. Then they will take some small shuttle down to Mars to meet up with the supplies previously left there.

Once the mission on Mars is complete they will load up in the shuttle now attached to the fuel and rocket sent earlier and meet up with the mother ship in orbit. No one will remain in the ship during the time on Mars due to the length of the mission.


There will be no other way. Mark my words.

Tom2Mars
2007-Jul-21, 03:12 PM
Yes, that would be the safe way to do the mission. However, adventurers, explorers and entrepreneurs don't always do things the safe way. For example, John Wesley Powell, a one-armed Civil War veteran, made headlines by being the first(recorded) white dude to raft down the Colorado River! That amazes me, an unknown river at the time, rapids & whitewater... One-Arm(!) Wow.

There could be some kind of friendly, not-friendly competition between a couple of billionaires that would precipitate a direct approach. One of them might have a terminal illness, and think, "What the heck, might as well make one last push, and do something different by going to Mars." Also, there are some potential scenarios where folks would want to go to Mars, with no intention of coming back, like chaos on Earth, collapsing infrastructure, environmental issues. That could change the Mars mission profile. Plus, the safe, government-backed approach still needs to be funded and supported in order to happen. Failing that, the riskier alternatives may be explored by someone, or some other country/company.


Just read the Oberg story. Interesting.

One question: with the Martian atmosphere at the surface being at best about 1 percent of the earth's you would need a HUGE 'IMP'-like structure to carry ANY sort of payload successfully to the surface. The Martian surface is not all that bouyant. Also, it's not also very effective for aerobreaking purposes either.

edit...
It is interesting, though - and I DO like the idea of having a large shelter on the ground for a habitat; I just think they'd be better off blowing one up once there. :)

I still think tsmund's idea to be the best and most practical - and something we could do relatively easily with current technology and engineering knowledge; I think each of the issues it addresses are things we can solve separately pretty easily, eg. getting a largish set of payload on the ground and getting people on the ground. It's combining them that makes it harder. Splitting them up makes sense.

Well, the most important question would be, what is the payload? If it can be fairly lightweight, so much the better. I was thinking of a large, rigid-skinned, fly-able craft with a multi-cellular interior. After landing, the outermost cells can be filled with Martian soil for radiation protection. That's where the rigid structure will come in handy.

Aerobraking is used at Mars, and most of the recent probes do use an aerobraking shell. And, a very large vehicle, with low density would slow down faster, and at a higher altitude.The Oberg article mentions that most of the aerobraking would be done in the altitude range of 400,000 feet down to 120,000 feet. The Mars atmosphere at datum is equivalent to roughly 100,000 feet at the Earth, plus with the lower gravity, a vehicle can fly with less wing loading, ie, it has better lift properties. Below datum, such as 15,000 feet lower in Coprates Chasma, the air is thicker, better for flying. Also, yes, it would be difficult to have neutrally buoyant vehicle, but even a partial buoyancy could be usefull, to reduce total vehicle mass for the low level flying and maneuvering.

Closed-loop life support, grow the food, recycle the nutrients and waste, add local minerals and water to expand production... that will keep the consumables down. Light-weight, concentrating Photovoltaics for power, electrolyze the water for H2 and O2, use for fuel cell backup, to supplement the Methane(CH4) produced by methane digesters. The methane can also be made into plastics through the ethylene route.

Again, a one-way trip saves on all that pesky return vehicle and fuel stuff. :)

If desired, the strategy of breaking up the payload can still be accomplished by just sending many low-density flying landers.

crosscountry
2007-Jul-21, 04:02 PM
ok, I see you point, but I don't see any "billionare" able to afford this venture - not even with partners.

Ronald Brak
2007-Jul-21, 04:16 PM
ok, I see you point, but I don't see any "billionare" able to afford this venture - not even with partners.

A mars mission might cost around $100 billion if done cheaply. Currently Bill Gates is worth about $56 billion. However he's more interested in such pursuits as fighting malaria so I think we can count him out. But if the world economy grows at 3% a year then there are probably going to be a lot more billionaires with a lot more money. In fifty years time the Bill Gates equivilent might be worth $225 billion in today's money and the cost of a mission should be lower due to technology advances. So to encourage the private exploration of space we should develop the world economy and eliminate diseases such as malaria and AIDS so billionaires will look to different places to spend their money.

thothicabob
2007-Jul-21, 04:33 PM
CrossCountry: the scheme you mention sounds a lot like the one tsmund was suggesting in the begining here. I hadn't previously seen such a plan presented by NASA, but I think the idea is the right way to do it, and that was the first time I'd seen it so expressed. If you know about some plans like that and have a link, it would be interesting to read. I think it's a good idea, regardless of the possible variations on the theme, but one that may be passed on by NASA in favor of other more expensive/difficult ones for some reason or another...unless someone there gets suddenly "inspired".

Tom2Mars: Well, most of the Oberg article spoke about using inflatable entry/re-entry in an earth re-entry context. The martian atmosphere on the ground has a pressure of about 6-7 millibars. the the Earth's is around 1000. That's about 0.6 percent - almost 170 times less dense than ours. And you're right, aerobraking is used on Mars...by unmanned craft, so far.

I am not saying it would not be used to land people, but it's not such a simple problem as it seems on the surface. The atmosphere is thinner - both in terms of density and in terms of how high above the surface the planet it begins to have much use for braking. This means that there's less time for the vessel to slow from orbital speed to a reasonable landing speed, and less help from the atmosphere to do it. You need HUGE parachutes if you use them, and you have to slow significantly somehow first before you can use them - you don't deploy parachutes at 10,000 mph with a lot of hope of them not being ripped to shreds instantly, along with a huge, though brief, g-force affecting lander (and those inside it). Getting the lander from orbital speed to a speed where the parachutes can be deployed within a short time window is a problem there.

Using some form of wing faces similar problems - and there you're talking about just plain size/strength issues. I think, though I may be mistaken, that you'd need about 20 times (at least) the aerodynamic surface area to compensate for the thin atmosphere, even given the lower gravity (which sort of helps, sort of hurts - you still have the same amount of intertia/momentum to deal with with less help from the air, but less gravitational pull - unfortunately, the difference in gravitation doesn't even come close to offsetting the atmospheric differences, as I see it (1/9 vs 1/166, by my simple calculations). There's just a lot of energy to shed, little time to shed it, and little help from the air - and you need to shed quite a bit more to safely land people than you do hardware. Orbital speeds are lower, so that helps too, but the thin atmosphere still poses a problem. No atmosphere would make it a lot easier. So would more.

In any case, there's no doubt we CAN do it using a combination of aerodynamic and powered braking; I'm not saying it's impossible or that the techniques you suggest won't be used in some way. It's just not as easy or straightforward as it is on earth, especially when human cargo is included in the equation.

And like you, I just wish we'd get the $%#& on with it!! :)

One side note about the Oberg article: it seems astounding to me that NASA or DoD haven't taken to the technology written about in the article and helped it along to refine/perfect the techniques...if for no other reason than to HAVE the option and ability at hand if needed. It seems a relatively cheap solution, and while not perhaps ideal for most situations, still a pretty cost-effective one that wouldn't cost all that much to perfect. Hmm. Maybe THAT'S the problem...

Svemir
2007-Jul-21, 05:07 PM
The trick will be the comets, but then, come to think of it - if we get to a point where we can move multi-billion/trillion/quadrillion ton comets around the solar system, would landing a few chunks of metal and biomass mars be that big a deal?
Well, I imagine that moving some asteroids from asteroid belt will be cheaper.
While, you have to use a lot of fuel travelling from Earth then travelling back,
making Mars habitable would be a recipe for a colonisation of the exosolar planets. People, animals and plants would differentiate into real "Martians"!
I imagine transforming an asteroide (comet) into rocket by applying to it 1 or more neutron bombs.
It coould be done in an assembly line :-) .

I haven't read all posts in "Space & exploration" forum, but I believe that someone had come up with the idea of colonising exo-solar planets by robots, where Earth-like planets will be seeded with microorganisms and gradually with multicellar life (humans, incl.) to speed up the process.
Again, that technology could be tested on Mars. (or Venus,Europa, Titan?)
In that sence more warmer Martian atmosphere together with gaseous and liquid water (again, due higher pressure and higher temperture avoiding certain evaporation point of water) would be a better place to colonise with microorganisms, then dry and pressureless Mars.

Jerry
2007-Jul-23, 01:53 PM
I don't see anything in this article that indicates that it can not be accomplished, only that a manned mission to Mars would/will be extremely expensive.

crosscountry
2007-Jul-23, 03:09 PM
and time consuming, with plenty of dangers.

thothicabob
2007-Jul-23, 06:00 PM
I don't see anything in this article that indicates that it can not be accomplished, only that a manned mission to Mars would/will be extremely expensive.

Actually, my take from the article was that they don't yet have a clue as to how they will engineer the landing yet. That's not to say it can't be done, and surely implies it could be expensive. But they haven't worked out 'how' to go about it yet, and mention many problems that seem to be, in sum, nearly insurmountable in some ways.

tsmund provided a simple solution that seems to be being overlooked (as seems to often be the case with NASA (check side discussion about IMP/inflatible entry/re-entry technologies)). This idea may or may not be perfect, but it seems as close as you can get, and seems pretty practical and cost-effective, too.

crosscountry
2007-Jul-23, 07:59 PM
we'll land with rockets just like on the moon. It's expensive but relatively save and it works.


The equipment may even already be parked in orbit, although I suspect not due to the difficulty of matching up with it.

Jerry
2007-Jul-24, 03:36 AM
we'll land with rockets just like on the moon. It's expensive but relatively save and it works.


The equipment may even already be parked in orbit, although I suspect not due to the difficulty of matching up with it.

Yes, It might take a lot of hardware launched and shuttled to Mar's orbit - perhaps assembled in low Earth orbit, then given a very very big gentile push. Hey, wouldn't that make a great final mission for the ISS?

thothicabob
2007-Jul-24, 03:47 AM
Yes, It might take a lot of hardware launched and shuttled to Mar's orbit - perhaps assembled in low Earth orbit, then given a very very big gentile push. Hey, wouldn't that make a great final mission for the ISS?

Why not 'recycle' it and push it to martian orbit? :)

Only half-joking...

crosscountry
2007-Jul-24, 08:46 AM
Yes, It might take a lot of hardware launched and shuttled to Mar's orbit - perhaps assembled in low Earth orbit, then given a very very big gentile push. Hey, wouldn't that make a great final mission for the ISS?



In the Conspiracy Theory section I put it out that once we abandon the ISS the Russians could modify it enough to land at least part on the moon.


In that way they would have a permanent human base well before we could.

cope
2007-Jul-24, 02:20 PM
Igor,

I agree with you. Some of the replies to the original post include remarkable quantities of groundless speculation, almost as if the posters didn't actually read the linked article.

I will go so far as to add that even the relatively benign business of sub-orbital space "tourism" will fall like a house of cards when the first space tourist casualties happen.

Assuming we can solve our current problems here on Earth, I can't even imagine human space travel beyond the moon in less than several hundred years when technologies undreamed of today become common.

I am not discounting the value of human imagination but I do like to emphasize the need to pay attention to realistic capabilities.

(cope ducks to dodge thrown brickbats)

thothicabob
2007-Jul-24, 05:01 PM
If we wait until we 'solve our problems here on Earth', we'll likely NEVER get very far into space. Of course, I'm not sure which problems you mean, but if you're talking about us learning how to live together in peace and create a global economic situation where wealth is distributed even a little bit more equitably, etc., I don't think I see that happening 'soon'.

That said, I feel that actively pursuing things LIKE space travel can have a complementary and beneficial effect, both in direct and indirect ways. Nothing pulled the USA together in a way with a sense of unity and pride like the space program of the 60's and early 70's did, and I think by extension, an international effort to get to Mars could do the same thing on an international scale.

The social, technological, political, and scientific benefits are, in my view, more than worth the cost and effort. I'm not saying it's going to inspire world peace and plenty all by itself, but it can be a positive contributing factor in many ways.

We have the resources to both address our terrestrial based problems AND pursue space exploration aggressively; it's really a matter of will when it comes to BOTH the latter and the former, and I personally think lowering the priority of space exploration in favor of 'solving other problems' would be counter-productive, at best.

I do agree with the space tourism bit; we're not at all "there" yet, at least for any large-scale industry. But there will always be people who have the money to spend and will spend any amount for realizing their own personal dreams or getting their moment of glory; it's a cocktail party conversation that's pretty hard to top. There's more than a little irony there, however, but this isn't the place to get into those side issues.

I bet we'll be on Mars before the end of this century, though, and perhaps within the next 20-30 years.

At least I hope so.

JonClarke
2007-Jul-25, 02:35 AM
There is a lot of chicken little in the original article and a succession of straw men. Yes, landing on any payload on Mars is challenging. Large ones needed for human missions especially so.

To say "Nobody knows how to do it" is false. A lot of studies have been done. The most detailed was probably the Rckwell MEM study of the late 60's. Other studies were done in support of the ISU Mars mission porject in 1991. There were a number of Russian studies in the 180's and 90's. In the 90's modelling of large payloads was carried out for the NASA DRMs. Curiously none of these other studies are mentioned in this story. The problems mentioned in the article are well known and a range of solutions are known. They are even mentioned, but curiously, never actually strung together. This is tabloid journalism, not analysis.

Some aspects of the article are complete red herrings. Nobody has suggested airbags as a means for landing human mission sized payloads. To devote a whole section to this is an irrelevancy, pure and simple. A straw man argument.

Mass entry velocities are much lower than Earth – less than 8 km/s for direct entry, 5 km/s for descending from orbit. By contrast even coming down from LEO requires about 8 km/s. The lower velocity change for Mars landing makes the problem easier. Funny that this is not mentioned. I guess it would spoil the chicken little approach.

Mars's atmosphere is much less dense than Earth's. But it is in fact deeper. Furthermore most atmospheric braking during Earth entry occurs in regions where the atmospheric density is very similar to that of Mars. As the article says, a high lift vehicle would be able to slow down to mach 2. Probably not winged though, a winged vehicle does not generate high lift at hypersonic velocities, and is wasteful of mass. Either a bent biconic or a lifting body would be suitable.

Nobody has suggested parachutes as the main form of braking on Mars in the last 40 years, so it is another straw man. Talking about landing like the CEV is wrong. The parachute is not for soft landing, just for braking. The parachute’s role would be to brake the spacecraft from the supersonic regime to the subsonic regime. Current parachute technology will do this. If you need a large parachute area you cluster them, not rely on a single large one. No need for single parachutes 100 m in diameter.

Nobody has ever suggested that rocket braking be the main method of landing. To say otherwise is deliberate misrepresentation. Straw man 3. The main descent engines would not fire until the parachutes had slowed the spacecraft to subsonic velocities.

It’s worth noting that although firing a rocket through a shock front is challenging, the thrusters of the Shuttle do this every entry, so did those on Apollo. There is no reason to suspect that we can’t do this on Mars. Given Even Shuttle and Apollo experience, we could do this if required. Straw man number 4.

Rocket landing on Mars will require more propellant than a similar exercise on the Moon. But is a hardly is fatal problem. It simply means that there will be no helicopter like flying across the landscape, you just get down as quickly as possible. The rockets are there for final braking and attitude control only, as the spacecraft homes in on a preselected target. It does not have to be an accurate landing, within a few km is that is required. Straw man number 5.

Yes, Mars has wind. But, as the article already has pointed out, the atmosphere is not very dense. In such an atmosphere, a 40 tonne vehicle is going to be far less sensitive to gusts that a 250 kg one like a MER. You would also pick your time and place for landing so as not to be too windy. We are starting tpo do this now, by the time we land crews we will be much better at it. A 6th sixth straw man.

Let me repeat, landing a large payload – 40-50 tonnes – on Mars will be a challenging exercise. It will require a lot of test and development work. But the succession of approaches needed to achieve it are known and understood, at least in outline, and have been for 40 years. These are: high lift hypersonic braking, parachute supersonic braking, and rocket braking for the subsonic phase. Other technologies may emerge and prove useful, like the hypercone mentioned, or the ellipsled, which is not.

Jon

thothicabob
2007-Jul-25, 03:16 AM
And that's what ya get for relying on a single article, however 'authoritatively' presented, for factual information... :whistle:

[blush]

Thanks for the insight, Jon - but even so, doesn't a 'two stage' solution seem reasonable/practical for any such attempt at a Mars landing?

Even with what you say, if the need is to land a 40-60 ton payload on the surface, it seems it would be easier to land the bulk of it without people; a landing with humans would seem to need to be done a bit more 'gently' than without, hence added difficulty and expense, so at least on the surface instead of landing all 50 tons or so as gently as needed for humans, it would seem to make sense to split it up into a cargo/supply drop and a 'gentle' human/sensitive equipment landing.

Thoughts?

cope
2007-Jul-25, 03:44 AM
JonClarke,

"To say 'Nobody knows how to do it' is false."

Are you saying that Robert Manning, the Chief Engineer for the Mars Exploration Directorate and presently the only person who has led teams to land three robotic spacecraft successfully on the surface of Mars, doesn't know what he is talking about? Or are you one of the people who failed to actually read the linked article?

"A lot of studies have been done. The most detailed was probably the Rckwell (sic) MEM study of the late 60's."

A study (http://www.astronautix.com/craft/mem.htm) that was basically a proposal for a jacked-up Apollo mission without any hard data on Mars landings?

"Other studies were done in support of the ISU Mars mission porject (sic) in 1991."

My reading of their summary report (http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/DOCS/EIC036.HTML) fails to see any technical particulars of landing on Mars.

"There were a number of Russian studies in the 180's (sic) and 90's. In the 90's modelling(sic) of large payloads was carried out for the NASA DRMs."

I did my best searching online for the results of these many studies and came up empty-handed. Perhaps you could provide some links?

"Curiously none of these other studies are mentioned in this story. The problems mentioned in the article are well known and a range of solutions are known."

Again, perhaps you could elucidate some of these know solutions that are apparently unknown to Dr. Manning.


Look, nobody wants to see human exploration of the universe continue and expand more than I do. However, the tendancy of people to ignore the technical and logistical hurdles to such missions cheapens the efforts of those who recognize the actual problems to overcome them.

This is actually a case where you need to be a rocket/ballistics/aerodynamics scientist to grapple with the problems. Wishing alone won't make it come to pass. Show me the numbers, the calculations, the computer models that describe the solutions and I will become a believer.

Van Rijn
2007-Jul-25, 05:22 AM
The biggest issue there (terraforming mars) would be, as you suggested, getting the atmosphere a bit more robust so a decent temp and pressure could be maintained to allow for liquid water, and I think that that's doable, perhaps even within a reasonable time frame, given the resources to _really_ take the "Nike approach".


A decent atmosphere is a very big issue, another is maintaining a decent temperature.



But if you want surface life of any sort, you're going to also have to figure out some way to generate a magnetic field around the planet, too. That may prove to be a bit of a more difficult nut to crack in practical terms.


But life could do just fine without a magnetic field, assuming there is a decent atmosphere, water, etc. The atmosphere would provide excellent particle protection.




And in any case, setting the processes in motion to create a sustainable biosphere may not be very easy...it's a pretty complex thing in itself, and likely a lot of counterintuitive suprises could be in store there that probably would make getting an initial payload to the surface seem like a kindergarten exercise (which, in a contextual sense, it IS!). :)

And getting life going isn't the same as making it livable outside for humans. A real terraforming project could easily take thousands of years.

Van Rijn
2007-Jul-25, 05:27 AM
JonClarke,

"To say 'Nobody knows how to do it' is false."

Are you saying that Robert Manning, the Chief Engineer for the Mars Exploration Directorate and presently the only person who has led teams to land three robotic spacecraft successfully on the surface of Mars, doesn't know what he is talking about? Or are you one of the people who failed to actually read the linked article?

I'd say it depends on what you mean by "nobody knows how to do it." If you mean that we don't have existing hardware, and that would take real work with some R&D, I'd agree. If you mean that we have no concept of how we could do it, I'd disagree.

thothicabob
2007-Jul-25, 05:42 AM
Van, you're right - it could easily take 1000's of years. It could take less, but I would doubt it. I think it could be possible to make it "less hostile" in a pretty short period, but that's a pretty subjective comment, I'll agree.

Is it worth the effort, is maybe the first question to ask, and I'd say 'yes', but I don't know that many others would agree, and in practice, I really don't know that we're able to seriously consider starting and maintaining a project on that sort of scale, even assuming the technology was there. Socially, I think we're still too "volatile"; no one can predict, I think, with any degree of certainty, what our society will look like even 50 years hence. I think we're overdue for some pretty serious changes.

JonClarke
2007-Jul-25, 06:03 AM
Are you saying that Robert Manning, the Chief Engineer for the Mars Exploration Directorate and presently the only person who has led teams to land three robotic spacecraft successfully on the surface of Mars, doesn't know what he is talking about? Or are you one of the people who failed to actually read the linked article?

I read read the article. It is not by Bernard Manning, but by a journalist, Nancy Atkinson, who interviewed him.


"A lot of studies have been done. The most detailed was probably the Rockwell MEM study of the late 60's."

A study (http://www.astronautix.com/craft/mem.htm) that was basically a proposal for a jacked-up Apollo mission without any hard data on Mars landings?

That's the one. It used the proven cone shaped of Apollo, but cannot be considered a jacked up Apollo, or even Apollo on steroids. The article you link to shows these differences very clearly.

As for there being no hard data for this study, the data available was from Mariner IV, 6 & 7. It was the same data that allowed the successful mission of Viking, susbequent data has defined out knowledge of the atmospheric structure, but not changed it substantially.


"Other studies were done in support of the ISU Mars mission project in 1991."

My reading of their summary report (http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/DOCS/EIC036.HTML) fails to see any technical particulars of landing on Mars.

You need to read the whole report for this, which is 500-600 pages in length. Try interlibrary loans, or ordering direct from ISU.

"There were a number of Russian studies in the 180's (sic) and 90's. In the 90's modelling(sic) of large payloads was carried out for the NASA DRMs."

I did my best searching online for the results of these many studies and came up empty-handed. Perhaps you could provide some links?[/QUOTE]

Try the Energia pages. There are few details but a number of different configurations were evaluated.

For the DRM see section 13.3.3 http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/docs/MarsRef/addendum/A3.htm Few detailsd are given, but clearly modelling was carried out.


"Curiously none of these other studies are mentioned in this story. The problems mentioned in the article are well known and a range of solutions are known."

Again, perhaps you could elucidate some of these know solutions that are apparently unknown to Dr. Manning..

Again, I hope they are known. Maybe he chose not to mention them, maybe the journalist thought it would make a more exciting story if she didn't.


Look, nobody wants to see human exploration of the universe continue and expand more than I do. However, the tendancy of people to ignore the technical and logistical hurdles to such missions cheapens the efforts of those who recognize the actual problems to overcome them.

Indeed the hurdles must be addressed. Having done several independent Mars misison studies I am aware of these although I make no claim to be an expert. But equally hurdles should not be exaggerated, as in this article.


This is actually a case where you need to be a rocket/ballistics/aerodynamics scientist to grapple with the problems. Wishing alone won't make it come to pass. Show me the numbers, the calculations, the computer models that describe the solutions and I will become a believer.

Unfortunately the detailed studies almost certainly involved a whole range of classified information. People like us can only get information from the crumbs. There is a lot of interesting stuff available through AIAA, but unfortunately it is subscription only.

I prefer the approach of this presentation http://www.nianet.org/salectureseries/pdfs/Braun_101706.pdf which illustreates the state of the art, the limits to which it can be extended, and a range of promising avenues for future research. A much better approach than "nothing we know works and we have no idea what will" of the original article.

Given some of the flight simulation programs available that model the Martian atmsopher it is possible for anyone to develop their own approach, for example this one http://www.freewebs.com/markpaton/Landing300307.pdf

Jon

JonClarke
2007-Jul-25, 09:00 AM
Thanks for the insight, Jon - but even so, doesn't a 'two stage' solution seem reasonable/practical for any such attempt at a Mars landing?

Even with what you say, if the need is to land a 40-60 ton payload on the surface, it seems it would be easier to land the bulk of it without people; a landing with humans would seem to need to be done a bit more 'gently' than without, hence added difficulty and expense, so at least on the surface instead of landing all 50 tons or so as gently as needed for humans, it would seem to make sense to split it up into a cargo/supply drop and a 'gentle' human/sensitive equipment landing.

Thoughts?

Split mission archiectures certainly are a very good way to reduce the mass of individual units landed on the Martian surface through several landings. It also minises mass in LEO by allowing cargo to be sent on ahead in high efficiency slow trajectories.

Jon

cope
2007-Jul-25, 10:48 AM
Jon,

Thanks for your quick and thorough reply. I will continue looking into all of this information.

cope

Stuart van Onselen
2007-Jul-25, 12:09 PM
I somehow don't think you'll heat the planet up quite enough to re-melt the core sufficiently to strengthen the magnetic through cometary impacts on the surface. Not really sure what to do about that.

Oh that! That's easy! Send a small group of good-looking scientists down in an Unobtainium-shelled burrowing machine armed with a cargo of fission bombs. Detonate the bombs near the core. Exit rapidly.

Don't you watch movies? ;)

adamsoltan
2007-Jul-25, 12:15 PM
The way I read the article a lander á la moon lander would be appreciated
but plumes in the direction of motion inside an atmosphere are notoriously
unpredictable. How about starting to break while still in the vacuum, say
a couple of hundreds of kilometers from the surface of Mars? If performed
in such a way that the lander is brought to more or less a standstill at a point
where the atmosphere is starting to become significant you could then unfurl
the parachutes and drop gently to the surface. Could this work? It sounds
simple but no one seems to have mentioned this solution in this thread.
I'm not an expert so perhaps I'm missing something significant. I don't
know...

Stuart van Onselen
2007-Jul-25, 12:23 PM
How about starting to break while still in the vacuum, say a couple of hundreds of kilometers from the surface of Mars? If performed in such a way that the lander is brought to more or less a standstill at a point where the atmosphere is starting to become significant you could then unfurl the parachutes and drop gently to the surface.

I think the problem is that, even at "standstill" you're still going to have to dissipate all the potential energy you have from being 100's of K's up a gravity-well.

Plus, stationary relative to what? The upper atmosphere? Then the lower atmosphere will be whipping by you at a high rate. And the reverse if you aim for "motionless" relative to the lower atmosphere.

But I'm sure a better explanation will be coming in 5...4...3...2...

adamsoltan
2007-Jul-25, 12:47 PM
you're still going to have to dissipate all the potential energy you have from being 100's of K's up a gravity-well.

True, but you're not going thousands of km/h, not even supersonic. This
should make things manageable.


Plus, stationary relative to what? Well, the surface of Mars. Besides, "standstill" is more of a figure of speech.
The idea is to get the speed down enough for using parachutes.

samkent
2007-Jul-25, 03:33 PM
1. Slowing 50 tons form several thousands k/hr to a standstill requires a lot of fuel. That is why we have used aerodynamic braking now.
2. Building up the atmosphere requires the planet to have a magnetic field.
Without it the solar wind would strip the atmosphere away as fast as we added to it.

djellison
2007-Jul-25, 04:16 PM
The idea is to get the speed down enough for using parachutes.

Parachutes wont get you to the surface safely though.

Under a parachute, a typical lander will fall at something like 150-200 mph.

The air is there - use it for what it can do ( get you to Mach 2 from entry speed ) and then figure out the complex part from there to touchdown.

Doug

selden
2007-Jul-25, 05:36 PM
Also, payload should be sent and automatically deployed with confirmation before the crew even leaves the earth to eliminate sharing the risk imposed by payload requirements with the risk to the crew. This would also prevent a fatal failure of vital payload deployment from endangering, or worse, dooming the crew members. The crewship should be composed of only that which is required to sustain and deliver them. Another way of looking at it is to put the payload on a longer timeline and the crew on a shorter one.

I'm a little surprised that nobody has pointed out that this, along with biconic landers, is exactly the plan put forth in NASA's "Mars Reference Mission" studies, which were published during the '90s.

The 1997 version is available at
ftp://nssdcftp.gsfc.nasa.gov/miscellaneous/planetary/mars_future/mars_ref_mission_sp6107.pdf
(237 ppg, 7.5MB)

JonClarke
2007-Jul-25, 09:39 PM
I'm a little surprised that nobody has pointed out that this, along with biconic landers, is exactly the plan put forth in NASA's "Mars Reference Mission" studies, which were published during the '90s.

The 1997 version is available at
ftp://nssdcftp.gsfc.nasa.gov/miscellaneous/planetary/mars_future/mars_ref_mission_sp6107.pdf
(237 ppg, 7.5MB)


That's probably the most detailed realisation of the split mission archiecture to date. But the idea has been round since the 80's. It's been used by most mission proposals since the early 90's

Jon

thothicabob
2007-Jul-25, 10:09 PM
it's a good one, too, at least in general terms. details can be debated, but much of such debate would be due to the datedness of the report. the core of it seems solid, though, and sensible. and good to see that, despite the impressions one would get from article in the OP of this thread, there has been serious AND detailed consideration of such an expedition.

it seems that the major holdback has been the political will to expend the economic resources such a project would consume, not that such a mission is technologically beyond our reach; many, if not all, of the obstacles remaining could likely be surmounted with sufficient impetus driving such a project.

of course, one must deal with economic realities, but i think even in here in the states, there are many areas that have been 'overfunded' and which have taken more than enough resources to cover these requirements. the same is likely true of other nations as well.

Van Rijn
2007-Jul-25, 10:52 PM
1. Slowing 50 tons form several thousands k/hr to a standstill requires a lot of fuel. That is why we have used aerodynamic braking now.


True.



2. Building up the atmosphere requires the planet to have a magnetic field.
Without it the solar wind would strip the atmosphere away as fast as we added to it.

Not true. Atmospheric loss is only an issue on geological scales. Even then, the loss would not be as bad in the current era as it was when the sun was young, and had a stronger solar wind.

thothicabob
2007-Jul-25, 11:33 PM
Atmospheric loss is only an issue on geological scales. Even then, the loss would not be as bad in the current era as it was when the sun was young, and had a stronger solar wind.

That's maybe true. But, I think lack of a magnetic field would still allow too much radiation to reach the surface; even a relatively dense atmosphere would not be enough protection, and it's unlikely Mars could support one (or we could induce one) at the surface of much more than a perhaps 1/2 that of Earth's, and even that guess is probably optimistic (hmm. it would be interesting to calculate just how many comets would be needed for that. :) ). That would require that humans on the surface would need to wear protection even if the atmosphere was breathably 'ok'.

Further, ionization of the atmosphere would also have an effect on how any induced atmosphere would develop, to my understanding.

Mars has a magnetic field, but it's very weak, and would have little of the protective effect even close to the scale that Earth's provides in these contexts, I think. I'm no planetary physicist, so the above points could be wrong, but I suspect not very wrong.

GOURDHEAD
2007-Jul-26, 02:49 AM
2. Building up the atmosphere requires the planet to have a magnetic field. Without it the solar wind would strip the atmosphere away as fast as we added to it. The losses won't be immediate. A 2 bar atmosphere will probably last several million years. By then we can add more as needed from the giants if Venus has been terraformed. The losses will more likely be from the larger mean velocity due to larger browian motion kenetic energy due to the higher temperatures than from the solar wind.

Van Rijn
2007-Jul-26, 07:12 AM
That's maybe true. But, I think lack of a magnetic field would still allow too much radiation to reach the surface; even a relatively dense atmosphere would not be enough protection,


Actually a relatively dense atmosphere would provide excellent particle radiation protection (UV is a separate issue, which partly depends on the atmosphere's constituents).



and it's unlikely Mars could support one (or we could induce one) at the surface of much more than a perhaps 1/2 that of Earth's, and even that guess is probably optimistic (hmm. it would be interesting to calculate just how many comets would be needed for that. :) ). That would require that humans on the surface would need to wear protection even if the atmosphere was breathably 'ok'.


I agree that producing the atmosphere is a key (and extraordinary) challenge. However, atmospheric pressure drops off more slowly on Mars than on Earth, so the total atmosphere for a zero elevation pressure equal to air pressure at Earth sea level would be substantially greater. Assuming we could put the atmosphere there, there is nothing limiting zero elevation pressure to half or even equal that of Earth's sea level pressure. Also, whether we could breath it or not would depend on the constituents as well as pressure: Lower total pressure would be acceptable with a higher oxygen partial pressure, unless, for example, it included a large amount of carbon dioxide.




Further, ionization of the atmosphere would also have an effect on how any induced atmosphere would develop, to my understanding.


It would only cause some stripping of the very outer layers of the atmosphere, a very, very slow process.

A magnetic field is not necessary to terraform Mars. That doesn't mean we have the technology to do it, but the lack of a magnetic field just isn't that significant.

Jerry
2007-Jul-26, 08:26 PM
The losses won't be immediate. A 2 bar atmosphere will probably last several million years. By then we can add more as needed from the giants if Venus has been terraformed. The losses will more likely be from the larger mean velocity due to larger browian motion kenetic energy due to the higher temperatures than from the solar wind.

I question this hypothesis: What about Venus?

thothicabob
2007-Jul-26, 08:40 PM
I question this hypothesis: What about Venus?

Ugh. Terraforming Venus? Sounds like the name for a wierd romance novel. :)

I would suspect that any attempt in that direction would be orders of magnitude more difficult; best we leave Venus as is and use it as a penal colony for interplanetary drug dealers, terrorists, tv talkshow hosts, and politicians.

That's my proposal.

Van Rijn
2007-Jul-26, 08:56 PM
Terraforming Venus would be more difficult (not that Mars would be easy). Here's a recent thread on it:

http://www.bautforum.com/life-space/59971-making-venus-livable.html

If you want to discuss it, I'd suggest taking it there, so we don't take this thread any further off-topic.

Jerry
2007-Jul-27, 01:59 PM
Ugh. Terraforming Venus? Sounds like the name for a wierd romance novel. :)

I would suspect that any attempt in that direction would be orders of magnitude more difficult; best we leave Venus as is and use it as a penal colony for interplanetary drug dealers, terrorists, tv talkshow hosts, and politicians.

That's my proposal.

No! Why hasn't the solar wind blown away the atomosphere of Venus! It doesn't have a magnetic pole to spit at.

antoniseb
2007-Jul-27, 02:30 PM
No! Why hasn't the solar wind blown away the atomosphere of Venus! It doesn't have a magnetic pole to spit at.
I'm not sure what you're getting at here, but...

the Hydrogen/Deuterium ratio in the Venusian atmosphere strongly suggests that the solar wind has been blowing away the atmosphere of Venus pretty vigorously, and so Venus started with a very large atmosphere, and has a much larger surface gravity than Mars. No mystery there.

thothicabob
2007-Jul-27, 02:51 PM
No! Why hasn't the solar wind blown away the atomosphere of Venus! It doesn't have a magnetic pole to spit at.

Hmm. Maybe it's the planetary atmospheric equivalent of those pain-in-the-keister birthday candles....

Jerry
2007-Jul-29, 08:54 PM
I'm not sure what you're getting at here, but...

the Hydrogen/Deuterium ratio in the Venusian atmosphere strongly suggests that the solar wind has been blowing away the atmosphere of Venus pretty vigorously, and so Venus started with a very large atmosphere, and has a much larger surface gravity than Mars. No mystery there.
That is a good answer, thank you. It brings up another good question though: why was the atmosphere of Venus >>> denser than the earth's?

Jon Matlick
2007-Aug-07, 12:48 PM
To answer this question, I just checked with JPL....Ranges from -67 Farenheit in summer to -197 F in winter. Can anyone tell me how terraforming can be done between 100 degrees below freezing and 200 degrees?

Jon Matlick

Ronald Brak
2007-Aug-07, 01:13 PM
Terraforming mars has been discussed quite a bit in other threads. If you use the search function you might be able to find some answers.

And welcome to BAUT!

Jerry
2007-Aug-07, 01:46 PM
To answer this question, I just checked with JPL....Ranges from -67 Farenheit in summer to -197 F in winter. Can anyone tell me how terraforming can be done between 100 degrees below freezing and 200 degrees?

Jon Matlick
I know some cannabis growers in Alaska who can probably answer that question...