Landing in Mars' atmosphere (Viking, Pathfinder)
Offline I've got a question. According to Wikipedia:
The atmosphere of Mars is relatively thin, and the atmospheric pressure on the surface varies from around 30 Pa (0.03 kPa) on Olympus Mons's peak to over 1155 Pa (1.155 kPa) in the depths of Hellas Planitia, with a mean surface level pressure of 600 Pa (0.6 kPa, or about 7-10 millibars, or 0.13 psi), compared to Earth's 101.3 kPa, and a total mass of 25 teratonnes, compared to Earth's 5148 teratonnes. However, the scale height of the atmosphere is about 11 km, somewhat higher than Earth's 7 km.
Mars surface gravity - 0.376 g
Weight:
3527 kg - Viking
264 kg - Pathfinder
Now, we see that Mars reputedly has 0.59% atmospheric pressure (0.0059) and 0.48% (0.0048) atmospheric mass compared to Earth. Even if we multiply the above mentioned probe's weight by the Mars' g ratio, it's still a lot. I don't understand how the scientists could even think of landing the probes with parachutes. That could work in Earth atmosphere, but hardly in 0.5 % of it, which is reputedly present on Mars. It had to be a nice thud when the probes landed, or better said, crashed. What exactly did the parachutes decelerate on? They wouldn't even open in that pressure! Effectivity of rocket propulsion is also doubtful.
However, we did receive some nice data and pictures. Is it possible, that the atmosphere of Mars is much more dense than it is still claimed? If yes, who's responsible severed head should we hang above the university gates?
Beings who deserve worship don't demand it. Beings who demand worship don't deserve it.
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I found the problem
(are we gonna have a "Mars Rover" conspiracy sprout up, Lumy? )
What Would Kharn Do?
Beings who deserve worship don't demand it. Beings who demand worship don't deserve it.
First, neither of the Viking Landers was landed used just parachutes to land. They were largely decelerated and landed using powerful thrusters.
Pathfinder, however, is notable for how it entered, descended and landed in several stages ...one of them using a 24' parachute designed to slow the decent of the probe in the Martian atmosphere to 65m/s from 400m/s. The Martian atmosphere, when compared to Earth's is slight, but it's still a fucking lot of gas and it slowed the probe from 7.5Km/s to 400m/s all on its own. Pathfinder used rockets after the airbags inflated to further slow the decent and finally it bounced for about 12m from 100-200m above the surface. Because of the low atmospheric pressure, the bags were only inflated to about 1psi.
I'll now give you a star. ...I'm sorry, there's no star emoticon.
Nasa's Page on Mars Pathfinder Entry, Descent and Landing
Trust me, it's easy to find the pages if you know how to google.
BigUniverse wrote,
"Well the things that happen less often are more likely to be the result of the supper natural. A thing like loosing my keys in the morning is not likely supper natural, but finding a thousand dollars or meeting a celebrity might be."
Thomathy, gold stars are easy to find if you know how to google them. Here you go:
In any case, you get one for the info but I took the question to be one of engineering. Basically, Lumy is looking to know if such can be done.
In this case, yes, I would see that it is possible to use a parachute to land a payload on Mars without other assistance. As lumy pointed out, the atmosphere is quite thin, so any heat shielding requirement would be small. Also, I would note that the terminal velocity of a parachute will be proportional to the area of the parachute and the weight of the payload.
Here we need to consider the fact that the area of a parachute scales with the square of the radius of same. Also, the weight will be proportional to the surface gravitation of the planet (which in this case is just under 1/3 of that of the earth) and thus the payload weight will be reduced by that amount.
Further, NASA routinely uses parachutes as part of the landing system to get stuff back to Earth. So honestly, if NASA wanted to do that, I don't really see a huge problem here. The only thing being that small rocket motors produce a fairly large thrust for a given weight, so it would probably be cheaper to launch from earth with deceleration thrusters that with the mass of a large parachute.
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I have seen photographs of the Mars Rover landing modules. It had yellow cables. And on another set of photographs, this time from Mars, there was red terrain, red sky, and orange cables of the module. (about a meter from the camera) It looked like the photographs' hue was artificially shifted to red, including the color of the cables. Without that, the atmosphere on Mars would be blue. A blue atmosphere would be something entirely different, than we're taught about the red planet.
Some interesting photographs can be found here: http://www.marsanomalyresearch.com/ Namely, plants, trees, liquid water, fields, monuments, and NASA's crude image tampering.
Beings who deserve worship don't demand it. Beings who demand worship don't deserve it.
I KNEW IT! FUCKER! GODDAMNIT! WHY SHOULD ANYONE BOTHER TO ANSWER YOU AT ALL!!!!!!? ARGH!!!! You make me ...annoyed. Damn you and your damned conspiracy nonsense.
And another thing. Look at the goddamned planet in the night sky. The fucking thing's red. There's no need to lie about it. The planet is covered by iron rust! Further, the atmosphere is largely CO2. I don't know what colour that should make the sky on Mars, but there is so much dust in the atmosphere that if it appears red, I shouldn't be surprised. Also, if you've ever looked at the large inventory of photos of Mars from the missions, you'll notice that the planet doesn't appear to be nearly as red as it looks from Earth. In fact, it's a rather bland, slightly red tinted beige.
If you're wondering how a parachute could operate in a CO2 atmosphere that is not very dense, but is 11Km tall, with 1/3 of Earth's gravity acting on the object tethered to it, perform the bloody calculations yourself. It's not as though you trust any science anyway. Which leads me to question your motivation here. No one is going to validate your crackpot idea that somehow NASA is lying about the composition of the Martian atmosphere and how it landed rovers there (or if it did, if you're thinking that too) and whether it intentionally renders the images with a redder hue than what would be seen by your human eye were you on the planet. Honestly, fuck off. Aren't you tired of your intellectual dishonesty yet?
BigUniverse wrote,
"Well the things that happen less often are more likely to be the result of the supper natural. A thing like loosing my keys in the morning is not likely supper natural, but finding a thousand dollars or meeting a celebrity might be."
Plus, wouldn't yellow cables that had been covered with a light dusting of red soil from lots of travelling around appear - I dunno - orange?
Forget Jesus, the stars died so that you could be here
- Lawrence Krauss
I know what this is about. It's the Martians. They made the face at Cydonia. They've got mystery mind control devices, and programmed the U.S. government to start the H.A.A.R.P project, which is really an effort to perfect mind control so that the Illuminati (and the Free Masons) can institute their three thousand year old plan to enslave 80% of the human race so that the Elite Ones can rise to the next level of Human Evolution.
Atheism isn't a lot like religion at all. Unless by "religion" you mean "not religion". --Ciarin
http://hambydammit.wordpress.com/
Books about atheism
Oh, that's why!!!.....
Lol.
Our revels now are ended. These our actors, | As I foretold you, were all spirits, and | Are melted into air, into thin air; | And, like the baseless fabric of this vision, | The cloud-capped towers, the gorgeous palaces, | The solemn temples, the great globe itself, - Yea, all which it inherit, shall dissolve, | And, like this insubstantial pageant faded, | Leave not a rack behind. We are such stuff | As dreams are made on, and our little life | Is rounded with a sleep. - Shakespeare
You speak about it as if it was a stupid idea!
Btw, I don't question that the probes landed on Mars. Whatever the atmosphere is, it's certainly not an obstacle to landing.
The cables on the photograph I mean were bright yellow on Earth, and bright orange, when photographed on Mars. The rest of the Pathfinder landing module also didn't seem dirty at all. It really looked like the 'shift hue' graphical effect, not a dust cover.
Of course, there were other photographs, like the Mars photographed from within a segmented cockpit of sorts, and outside seemed to be a red martian day. But one of these segments didn't show a red sky, but blue.
Beings who deserve worship don't demand it. Beings who demand worship don't deserve it.
And you're talking to an expert in chemical colour, so...
What are the particle sizes of the rust particles? What's the particle size of the martian dust? Could a light smattering of brown dust particles, which may be smaller than rust particles, cause an orange colouration on anything they coated? If you're curious the answer is yes.
On that side - colour is never only about the colour absorbed/emitted by the material in question. It is heavily affected by the type of light coming through the atmosphere from the sun - specifically affected by a rust infused atmosphere for example. Explain to me why you think it's a computer shop, and give a credible reason.
Forget Jesus, the stars died so that you could be here
- Lawrence Krauss
Ok, so I just wasted precious moments of my life reading some of this conspiracy theory crap. I want my moments back!
Have this to give it back...
Forget Jesus, the stars died so that you could be here
- Lawrence Krauss
God Dammit Hamby, SHUT UP!
***Nothing to see here people, move along, this guy doesn't know anything, everything he says is wrong.***
When you say it like that you make it sound so Sinister...
Actually, I think you are onto something with the light passing through the atmosphere. Remember that the atmosphere if Mars is mostly CO2 with only trace amounts of other chemicals. Now I am not sure how the gas pressure affects matters but the atmosphere is going to pass reddish light preferentially and block other colors. As far as the dust in the atmosphere goes, here I am thinking that the gas pressure works against that as it will not be able to support all but the tiniest of dust particles for a substantial length of time.
Now it would take a good bit of googling to confirm what I can just barely call a hypothesis but the real cause could be that the light spectrum at the surface is altering the perception of color. For example, you could get one of those yellow lamps that are supposed to repel bug from your porch in the summer and use it to light your living room. With the altered spectrum in the room, everything that you own would look strange colors.
That alone could throw off one's perception of the wires on the Mars probes. Although, to give partial credit to luminon, it is also possible that NASA/JPL has color corrected those pictures to make them a bit more like what the public expects. That of course would throw the colors off as well.
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Viking Landing I - When the parachutes were deployed, it's speed was 250 m/s at an altitude of 6km. Even in the thin atsmophere the chutes slowed the Lander to a speed of 60 m/s within 45 seconds. Also the weight was reduced 8 seconds after the chutes deployed when the aeroshell was jetisoned. At 1.5 km altitude, retro-rockets were fired until landing 40 seconds later at about 2.4 m/s. The landing rockets used an 18 nozzle design to spread the upward thrust evenly.
BTW the 3 parachutes were 16 m diameter, which scoped up alot of thin air.
The parachutes worked because the Lander was traveling at a high rate of speed and they were huge.
Look up Viking II and Pathfinder yourself.
People who think there is something they refer to as god don't ask enough questions.
It's all about terminal velocity. When I skydive I reach about 120 mph but on Mars it would be about 600 mph.
The probes would be travelling very fast. They still need a heat shield to avoid burning up. Even with such a thin atmosphere, there is still enough to deploy a parachute and slow the fall. (Especially several large ones.)
(Odd, sometimes I miss the metallic taste of hexavalent chromium in the air mixed with the oddly sweet smell of solvents.)
BigUniverse wrote,
"Well the things that happen less often are more likely to be the result of the supper natural. A thing like loosing my keys in the morning is not likely supper natural, but finding a thousand dollars or meeting a celebrity might be."
I like this kid. He's the personification of bong residue. I say, "Rant on, young man!"
"Tis better to rule in Hell than to serve in Heaven." -Lucifer