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I guess the difference with the moon fear was of the unknown as to whether or not bacterial life was present. We did not know as much about how life was started back them. Lack of an atmosphere should have been enough to put out any though of such a fear. But Mars is a different set of variables for if life could have developed and is very possible to contain such.
But long before man will go we should be able to answer that question. Either with advanced probes sent to the surface with the ability to detect even the smallest of microbes. Or though the sample return in a contamination sealed container to a lab that can deal with the possibility. Whether that lab is in orbit with the ISS or near it or part of some other way station or on the ground it does not matter where the work gets done to analyze the sample so long as it is done.
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I guess the difference with the moon fear was of the unknow as to whether or not bacterial life was present. We did not know as much about how life was started back them. Lack of an atmosphere should have been enough to put out any though of such a fear. But Mars is a different set of variables for if life could have developed and is very possible to contain such.
*Yes, I see your point. It just was too much of a reminder, though, of overinflated fears of yesteryear. There's some legitimate concern in this regard, I suppose, but it seems to smack of fear-mongering sometimes. :-\
Am feeling a bit more impatient and prone to exasperation with the space program (-- ha ha, WHAT space program) today.
--Cindy
We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...
--John Sladek (The New Apocrypha)
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The steerable parachute idea seems to be a good idea to me. It's relatively easy, doesn't add much weight at all, and should provide some benefit.
Using the mars probes as an example the parachute will deploy at 125 km above the surface of mars. Initially it will only slow the landing vehicle but as it begins to right itself pull cords could be exercised on either side to guide the lander in. While it won't be as effective on mars as it would on the earth it should still work.
Also I think part of the reason that NASA probes landing accuracy on mars is inconsistant is because it's not really that important. So what if a probe hits miles away from it's intended spot?
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With new evidence that bacteria could live on Mars, a leading scientist is calling on NASA to improve procedures to prevent astronauts from bringing contamination back to Earth. If necessary, that could mean the astronauts would have to spend the rest of their lives on Mars
Lets say that Mars has native bacteria, and astronauts go to Mars and return, and the decontamination does not kill all of the bacteria. So what? I don't think that there is any realistic chance of any sort of Martian plague developing, and it is unlikely that microbes from Mars could out compete microbes from Earth in most terrestrial environments. I don't see why people are so worried about back contamination.
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The steerable parachute idea seems to be a good idea to me. It's relatively easy, doesn't add much weight at all, and should provide some benefit.
My point is that there will NOT be much bennefit, because the air is too thin to do you much good when you are moving slow enough to swtich to steerable mode.
The astronauts are going to have about two years to find out if there are any Martian hitchhikers, so we should know beyond reasonable doubt if there is somthing to be worried about.
When the astronauts' capsule returns to Earth, keep the hatch closed. Helecopter/Osprey the thing to a bioharzard lab for tests.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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I disagree but most likely we are arguing over a different definition of beneficial. In terms of complexity, cost, and weight I think it would definately be worth it but the real worth is how much of a difference it would make.
If it only gives you half a mile then it's probably a waste but if you can get 10+ I would include it.
Any math wizards who can come up with an estimate as to the maximum amount of steerable distance this parachute would provide? Figure it would be deployed at 125 km above mars, steering would not be used until the craft slows enough to right itself.
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A steerable parachute would be a waste of resources, the astronauts could probably walk the distance that would be gained from "steerability". Especially if the crew is coming down on a sled with the rover, "fogetaboutit."
As has been pointed out earlier, your going to want to make course corrections as high in the atmosphere as possible to shrink your landing elipse. It's a matter of energy conservation; why dilly-dally around hovering over the surface when you can just drive to your destination.
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If we can park the habitats near each other then we can connect them with inflatable tubes to make a base. Each would have it's own solar array and deployed nuclear reactor so there would be a lot of power available. Some of the habs would be living spaces, others would have science equipment, greehouses, machine shops... The problem is how do you move them with their solar arrays and nuclear reactors after they've landed?
I think the point to remember is that the vehicle is travelling at very high speeds, over 7,000 meters a second initially then slows down to 60 m/s. As it descends and slows the atmosphere gets more dense. I know it would not be much but as I said if we can get 10+ miles out of it then go ahead and use it. How much resources (money or weight) is it going to use anyway? It's so darn simple. You're going to need a parachute anyway so a couple of steering lines and a motor to pull them is nothing.
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Your disregarding testing and simulation that must be done both on Earth and on Mars. Heck, the x-38 program was expensive and that was just dropping a tiny craft from a b-52.
These things are easy on Earth because we've been doing them for 30-40 years; the margin for mistakes is much more narrow on Mars (no AAA, no ER).
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The idea of using clusters of HAB modules to make a "Base" or somthing... I don't think so.
First off, they are pretty small, and they aren't designed to be moved. On early missions, they will probobly be the heaviest object we bring, and trying to get them to move when your rovers have so much less traction (less gravity) will be no easy feat. The HAB still has the same inertia as it does here.
Second, the nuclear reactor won't last forever. Since mass is at a premium, the reactor will probobly not have enough Uranium to operate more then 5-6 years or so before its output begins to drop off, which isn't very long when you have to wait a ~2 years between landings.
Plus, you can't move the reactor around near the base for about a year after it has been shut down because of the intense decay radiation. Most likly, the reactor will just be driven into a crater or a ring of dirt piled up around it for shielding.
LSS systems will also be getting pretty old after 2.5yrs of continuous use.
And we won't be landing HABs close together anyway, they will be spread out to explore as much of the planet as possible.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Parachute design in complicated because there are so many variables and design requirments. Air density, drag coeficent, and velocity all change throught the deployment. And you have to design around not only these variables but also the mass (duh) and amount G-Force you can safely inflict upon your cargo.
Anyway here is the relevent equation:
F=1/2*d*C*A*V^2
F = force of drag (Newtons)
d = air density (variable with altitude, .015kg/m^3 at the datum)
C = Drag Coefficent (variable with parchute design and conditions .5~2)
A = Area of parachute (m^2)
V = Velocity (m/s)
This is compared with the force of gravity (3.7N/kg) to determine it's effect.
Because mars's atmosphere is a lot thinner than earth's, a parachute still has to be alot bigger than a terrestial one to get the same effect. Let's consider what would be necessary for a parachute assited soft landing using optimal conditions.
M*G=1/2*d*C*A*V^2
we want the drag equal (if not greater) than gravity for a soft landing
G = 3.7m/s^2 on mars
d = .015kg/m^3 (really alot less at high altitudes)
C = 1.5 (typical for a circuler chute)
V = 3m/s (speed you want to land at)
This works out to an 986m^2/kg. For the 25 ton hab module, that is going to be one big chute! Nearly 25 square kilometer of chute would be necessary. Clearly impracticle. And this is for a simple circle chute, in optimal conditions. For a steerable chute (which has a smaller drag co-efficent) in more realistic conditions the situation is even worse.
A parachute might be usefull at high altitudes to shed some speed (I didn't know spirt used one like that) especialy since martian terminal velocity is going to be alot given the thin-air, probably >250m/s but for the final decent it is impossible.
BTW, could someone check my math on this? I was expecting the parachute to be big, but not THAT big.
He who refuses to do arithmetic is doomed to talk nonsense.
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First off, they are pretty small, and they aren't designed to be moved. On early missions, they will probobly be the heaviest object we bring, and trying to get them to move when your rovers have so much less traction (less gravity) will be no easy feat. The HAB still has the same inertia as it does here.
The habs are pretty small, which is why you would want to re-use them if possible, to increase your living space. As for moving them, it would certianly be tough, but the utility of it certianly makes giving it a try worth-while. At 25 tons the hab certianly isn't light, but this isn't an impossible sum to try and move. Towing it certianly would be tricky, but that's now how I would go about it. I would design one of the light rovers to fit-underneath and then carry the hab module. A pretty beefy engine would still be needed, but not nearly so bad as if you were trying to tow the thing, and you wouldn't have to add mass to your tractor to give it more traction.
In any case, powerful earth-moving equipment is going to be a necessity at any Mars base. Buldozers, dumptrucks, cranes, ect. These sorts of vehicles could all be modified for doing the task.
Second, the nuclear reactor won't last forever. Since mass is at a premium, the reactor will probobly not have enough Uranium to operate more then 5-6 years or so before its output begins to drop off, which isn't very long when you have to wait a ~2 years between landings.
True, but with landings coming in every 2 years or so that gives you a 1-2 reactor margin, which you can elimnate on a mission to save mass. Furthermore, the reactors could be designed to be refuled, greatly lengthing there lifespan. Also since there should be little reason to run more than one reactor at a time, the un-used one can be shut off, pro-longing their life. A more heavy-duty reactor should be a high priority though.
Plus, you can't move the reactor around near the base for about a year after it has been shut down because of the intense decay radiation. Most likly, the reactor will just be driven into a crater or a ring of dirt piled up around it for shielding.
Care of spent fuel/reactors is certianly a tricky issue. But since the reactors don't weigh an huge amount it is not unreasonable to assume that an un-manned rover might be able to handle disposal tasks.
LSS systems will also be getting pretty old after 2.5yrs of continuous use.
I disagree with this. If the LSS system is designed to last 3-5 years (it has to provide for tansit in as well, and possible an extended stay if something goes wrong), it mean time to failure is going to be alot longer than 3-5 years to ensure it's safety. The things is going to have to be pretty bullet proof, it's going to be designed to last. And any repair/maintness equipment is bound to weigh alot less than a complete system in any case.
He who refuses to do arithmetic is doomed to talk nonsense.
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BTW, could someone check my math on this? I was expecting the parachute to be big, but not THAT big.
Uding your equation, I get a value of 36.5 m^2/kg, or 1/27 as large as your parachute. The hab would therefor need a parachute of "only" about 1 km^2.
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The hab would therefor need a parachute of "only" about 1 km^2.
Oh thats all. ???
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I didn't mean for the parachute to be the only landing system, just the initial device like the mars probes. The mars probes were still travelling about 60 m/s when the rockets fire to further slow them. The parachute is then cut away.
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Even if the parachute could save significant fuel there is the risk of the parachute not opening. A crash landing could damage key life support systems and the rover needed to make it to the safe haven of the hab. Although I do wonder if less fuel was needed for landing if more fuel could then be devoted to low velocity course corrections. How soon can we get read of the heat shield (altitude and velocity)? I ask this because as GCNRevenger pointed out the earlier the course correction the better. I think there may be another option her to. If the rocket could fire exhaust in several different angles some steering would be possible even while a standard parachute was deployed.
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You don't have to move a 25-tonne hab. You could move the following separately: consumables (7 tonnes), spares and margin (3.5 tonnes), rovers (2.2 tonnes), equipment and furniture (2 tonnes), crew and suits (0.8 tonnes). The hab, life support, and other necessities mass 10 tonnes at most. If an inflatable hab were used instead, it might be designed to be moved on its own trailer.
-- RobS
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There is a risk of the parachute not opening. There is risk of the rockets not firing as well, or one malfunctioning and the others throwing the ship way off course.
As far as moving from one habitat to another, each is the same so why move from one to the other? I can only see it if one develops a serious leak or malfunction.
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Energizer bunny
The MSL's landing ellipse -- the zone in which a spacecraft attempts to land within -- is some 6 miles by 3 miles (10 kilometers by 5 kilometers). That is nearly a factor of ten better than the target zones in which the Spirit and Opportunity exploration rovers came to rest.
http://www.space.com/businesstechnology … .html]Next Generation Rover The Mars Science Labotory
Also see discussion:
http://www.newmars.com/forums/viewtopic.php?t=1588]Next Generation Rover The Mars Science Labotory
Hang time
After diving through the martian atmosphere and then under blossomed parachute, the Skycrane/MSL hardware would be set free to maneuver over Mars.
The Skycrane frame carries propellant tanks topped-off with hydrazine propellant, as well as two "outriggers" - each outrigger equipped with a set of 700-pound thrust rocket motors. This suite of controllable engines first run hot and heavy to slow the structure down. By reducing motor thrusting, the Skycrane eases on down toward Mars.
Using guidance and navigation gear, the Mars-bound hardware enters hover mode for a nominal five seconds. In a steady-as-she-goes manner, it hangs in mid-air a mere 15 feet (5 meters) above a pre-determined slice of martian real-estate
No fuss. No muss. No miles of bouncing. MSL's touchdown speed would be modest: one meter per second. "That's like falling from three inches on Earth," Muirhead told SPACE.com . "We're six wheels on Mars instantly," he explained
The Skycrane frame carries propellant tanks topped-off with hydrazine propellant, as well as two "outriggers" - each outrigger equipped with a set of 700-pound thrust rocket motors.
The mobile lab is five times larger than the current wheeled robot design now busily at work on Mars. That class of rover is around 400 pounds (180 kilograms). The heftier MSL could tip the scale at 1,980 pounds (900 kilograms).
Well we are using parachutes to assist land something nearly one metric ton and land it very softly. It is not a 25 ton hab but it is a start and the landing accuracy is very good. Indecently if we use a wheeled landing then we have a mobile hap. Perhaps have a small cockpit with life-support and inflatable hap on the back part of the vehicle. It couldn't be packed with too much science equipment or furniture but these tings could be moved in once it rendezvous with extra supplies at the MAV. Moreover it should have no trouble getting to the MAV because it is landing within 6 miles. That is walking distance. Surely the drive won't be a problem.
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Another thought if you have a mobile hab maybe there are two many problems with powering it by a nuclear reactor but what about an RTG or latest radio isotope batteries. These batteries naturally recharge and will be considered for laptops in the future. The recharging could possible be speed up with solar panels.
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