|
|
Thread Tools | Display Modes |
#41
|
|||
|
|||
Discussion on sci.space.science
|
#42
|
|||
|
|||
Discussion on sci.space.science
"Scott M. Kozel" wrote on Wed, 15 Aug 2018
13:05:30 -0700 (PDT): On Wednesday, August 15, 2018 at 7:16:13 AM UTC-4, Jeff Findley wrote: But, at the same time, terraforming will take hundreds or thousands of years. Not something we're ever going to watch live on YouTube like a rocket launch. One website article I found said more like 100,000 years. It will take sometime between a week and forever. All of us here will no doubt be long gone when the first Kuiper belt object is dropped on Mars. Just how do you go about "dropping a Kuiper belt object on Mars?" The same way you move anything else in space. An object 1/4 mile in diameter would probably be in the billions of tons. Where will the energy be found ... Well, the object is essentially MADE of fuel, so you just send out a tug engine and burn part of the object to get it to Mars. Or you build a mass driver tug and throw part of the object to move the rest of it. Or ... ... to transfer that to a Mars solar orbit perigee, then accelerate it up to Mars solar orbit speed, then decelerate it to Mars surface at a speed that won't create a massive crater on the scale of the one out in Arizona? Why do you care if it makes a crater and what makes you think it would? These things are mostly volatiles. They're going to melt on the way down. Worst case you get something like Tunguska, which made a big blast but left no crater at all that we can find. How many hundreds or thousands of such objects would be needed? Why do you even ask questions like this? -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#43
|
|||
|
|||
Discussion on sci.space.science
On Thursday, August 16, 2018 at 12:08:28 AM UTC-4, JF Mezei wrote:
QUESTION: In theoretical terraforming scenario where lots of CO2 is added, with so much of atmpsphere very thin and very high, would the CO2 reflect the heat back to ground level in a significant way? Or would it trap heat at such a high altitude that ground level would see little change ? One of the articles that I found, said that if the terraforming process went awry, that fixing the issues might make the whole process far more difficult and time consuming than it would be from starting with the virgin planet. |
#44
|
|||
|
|||
Discussion on sci.space.science
On Thursday, August 16, 2018 at 12:08:37 AM UTC-4, Fred J. McCall wrote:
"Scott M. Kozel" wrote on Wed, 15 Aug 2018 One website article I found said more like 100,000 years. It will take sometime between a week and forever. A week is a bit of a stretch. Just how do you go about "dropping a Kuiper belt object on Mars?" The same way you move anything else in space. So it is an engineering problem. Just like if someone proposed increasing the diameter of the orbit of Venus by 10 million miles as part of its terraforming process. An object 1/4 mile in diameter would probably be in the billions of tons. Where will the energy be found ... Well, the object is essentially MADE of fuel, so you just send out a tug engine and burn part of the object to get it to Mars. Or you build a mass driver tug and throw part of the object to move the rest of it. Or ... You need an oxidizer in addition to the fuel (methane, ethane, other hydrocarbons). Why do you care if it makes a crater and what makes you think it would? These things are mostly volatiles. They're going to melt on the way down. Worst case you get something like Tunguska, which made a big blast but left no crater at all that we can find. Depends on the velocity and angle of entry. Presumably the Tunguska object entered the atmosphere and a very high velocity but a very shallow angle. A steep angle might have had the object hit the Earth mostly intact. A cubic mile of ices coming in at 20,000 mph and an angle of 70+ degrees to the ground? |
#45
|
|||
|
|||
Discussion on sci.space.science
JF Mezei wrote on Thu, 16 Aug 2018
00:08:27 -0400: On 2018-08-15 20:16, Jeff Findley wrote: Nuclear fission or nuclear fusion powered rocket engine using some of the volatiles from the Kuiper belt object as reaction mass. You'd almost surely combine that with some gravity assist flybys and the like. But, as you said before, this would be a very long process. Woopty do. Dipty ****. When you consider the low gravity of Mars, and that to increase PSI are ground level, you will need to add a HUGE amount of atmpsophere most of which will be so high as to be useless, it becomes far more efficient to just build pressurized shelters (which you need to build anyways) and just add the atmosphere needed to pressurize the shelters and energy to heat them. Except then you're having to work in a high-radiation low-pressure environment, which is much more difficult and dangerous. Estimates say if you could melt all the CO2 at the poles it would get you halfway there without having to dump in anything from outside. And since such a colony would have limited O2 supply, it is more likely that the CO2 would get recycled into Carbon and O2 as part of ECLSS of the habitable volumes. aka: they aren't going to dump CO2 into outside atmosphere. Why not? You can always get it back when you want it. QUESTION: In theoretical terraforming scenario where lots of CO2 is added, with so much of atmpsphere very thin and very high, would the CO2 reflect the heat back to ground level in a significant way? Or would it trap heat at such a high altitude that ground level would see little change ? If there is no overcast in the atmosphere you will likely get warmish days and cold nights (think Denver on a clear winter day). -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#46
|
|||
|
|||
Discussion on sci.space.science
"Scott M. Kozel" wrote on Wed, 15 Aug 2018
21:24:54 -0700 (PDT): On Thursday, August 16, 2018 at 12:08:37 AM UTC-4, Fred J. McCall wrote: "Scott M. Kozel" wrote on Wed, 15 Aug 2018 One website article I found said more like 100,000 years. It will take sometime between a week and forever. A week is a bit of a stretch. Just how do you go about "dropping a Kuiper belt object on Mars?" The same way you move anything else in space. So it is an engineering problem. Just like if someone proposed increasing the diameter of the orbit of Venus by 10 million miles as part of its terraforming process. True, although changing the orbital velocity of something the size of a planet is just a BIT harder than moving a bunch of comet stuff. An object 1/4 mile in diameter would probably be in the billions of tons. Where will the energy be found ... Well, the object is essentially MADE of fuel, so you just send out a tug engine and burn part of the object to get it to Mars. Or you build a mass driver tug and throw part of the object to move the rest of it. Or ... You need an oxidizer in addition to the fuel (methane, ethane, other hydrocarbons). Part of these things IS water-ice. Plus you can always use something like nuclear thermal that doesn't 'combust' the fuel in the usual sense. Why do you care if it makes a crater and what makes you think it would? These things are mostly volatiles. They're going to melt on the way down. Worst case you get something like Tunguska, which made a big blast but left no crater at all that we can find. Depends on the velocity and angle of entry. Presumably the Tunguska object entered the atmosphere and a very high velocity but a very shallow angle. A steep angle might have had the object hit the Earth mostly intact. Unlikely. The Tunguska object was believed to be something more like a comet than an asteroid (exactly what you'd be throwing at Mars) and if there was any significant rocky core we'd have found impact indications. A cubic mile of ices coming in at 20,000 mph and an angle of 70+ degrees to the ground? Remember, comet-stuff starts disintegrating from solar pressure... -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#47
|
|||
|
|||
Discussion on sci.space.science
On Thursday, August 16, 2018 at 7:00:55 AM UTC-4, Fred J. McCall wrote:
"Scott M. Kozel" wrote on Wed, 15 Aug 2018 So it is an engineering problem. Just like if someone proposed increasing the diameter of the orbit of Venus by 10 million miles as part of its terraforming process. True, although changing the orbital velocity of something the size of a planet is just a BIT harder than moving a bunch of comet stuff. You need an oxidizer in addition to the fuel (methane, ethane, other hydrocarbons). Part of these things IS water-ice. Plus you can always use something like nuclear thermal that doesn't 'combust' the fuel in the usual sense. I was somewhat tongue-in-cheek about mentioning Venus, as its mass is millions of times more massive than a comet-like object. But comets themselves are massive and would take fantastic amounts of energy to redirect -- "However, what is most likely being asked here is what is the mass of a typical comet. And the answer to that is: it varies. Cometary bodies large enough to be detected (i.e. to have both a head and a discernible tail) can range from less than 6.5 x 10^13 (65 trillion) kilograms, on up to the mass of Comet Hale-Bopp, which has been conservatively estimated at 1.3 x 10^16 (13 quadrillion) kilograms, or what would be more than 28.6 quadrillion pounds if the comet were to sit somehow on the surface of the Earth." https://www.quora.com/How-much-does-a-comet-weigh Depends on the velocity and angle of entry. Presumably the Tunguska object entered the atmosphere and a very high velocity but a very shallow angle. A steep angle might have had the object hit the Earth mostly intact. Unlikely. The Tunguska object was believed to be something more like a comet than an asteroid (exactly what you'd be throwing at Mars) and if there was any significant rocky core we'd have found impact indications. The Tunguska object is a mystery. As you suggested a comet-like body melts and outgasses as it comes closer to the Sun. Usually well underway within 2 astronomical units from the Sun (Mars being within that). So the questions outstanding are how did a comet get that close to the Earth without being sighted, how did it stay intact enough to cause a massive explosion in the atmosphere. One theory is that it was a rocky object that came into the atmosphere at a nearly flat angle and at extremely high velocity (70,000 mph or more) and traveled several miles in the atmosphere and completely disintegrated in a multi-megaton explosion to where no significant meteorite remained. That scenario probably passes the physics test. Like I said it is still a mystery among scientists that have studied it. Several good theories but no conclusion. |
#48
|
|||
|
|||
Discussion on sci.space.science
JF Mezei wrote on Thu, 16 Aug 2018
11:55:47 -0400: On 2018-08-16 06:53, Fred J. McCall wrote: If there is no overcast in the atmosphere you will likely get warmish days and cold nights (think Denver on a clear winter day). The second you need a pressurized scuba suit when going outdoors, does it really make a big difference if it is cold or really cold outside? You appear to have forgotten the whole "increased atmospheric pressure" thing, Mayfly. At that point you don't need a "pressurized scuba suit" (which is sort of a conflicting statement in itself, there being no such thing as a 'scuba suit', much less a pressurized one). You just need a breathing mask. The minute your habitats need to be pressurized and insulated, does it really make such a big difference if it is cold or really cold outside? If you never go outside, why bother to go at all? Futhermore, what is the weather impact to increasing air density and temporature on Mars? could this mean more peaceful weather or stronger/more frequency wind/sand storms ? It makes it rain magic pixie dust. Hey, you asked a stupid question... -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#49
|
|||
|
|||
Discussion on sci.space.science
"Scott M. Kozel" wrote on Thu, 16 Aug 2018
10:01:05 -0700 (PDT): On Thursday, August 16, 2018 at 7:00:55 AM UTC-4, Fred J. McCall wrote: "Scott M. Kozel" wrote on Wed, 15 Aug 2018 So it is an engineering problem. Just like if someone proposed increasing the diameter of the orbit of Venus by 10 million miles as part of its terraforming process. True, although changing the orbital velocity of something the size of a planet is just a BIT harder than moving a bunch of comet stuff. You need an oxidizer in addition to the fuel (methane, ethane, other hydrocarbons). Part of these things IS water-ice. Plus you can always use something like nuclear thermal that doesn't 'combust' the fuel in the usual sense. I was somewhat tongue-in-cheek about mentioning Venus, as its mass is millions of times more massive than a comet-like object. But comets themselves are massive and would take fantastic amounts of energy to redirect -- "However, what is most likely being asked here is what is the mass of a typical comet. And the answer to that is: it varies. Cometary bodies large enough to be detected (i.e. to have both a head and a discernible tail) can range from less than 6.5 x 10^13 (65 trillion) kilograms, on up to the mass of Comet Hale-Bopp, which has been conservatively estimated at 1.3 x 10^16 (13 quadrillion) kilograms, or what would be more than 28.6 quadrillion pounds if the comet were to sit somehow on the surface of the Earth." https://www.quora.com/How-much-does-a-comet-weigh Still microscopic when compared to a planet. Depends on the velocity and angle of entry. Presumably the Tunguska object entered the atmosphere and a very high velocity but a very shallow angle. A steep angle might have had the object hit the Earth mostly intact. Unlikely. The Tunguska object was believed to be something more like a comet than an asteroid (exactly what you'd be throwing at Mars) and if there was any significant rocky core we'd have found impact indications. The Tunguska object is a mystery. As you suggested a comet-like body melts and outgasses as it comes closer to the Sun. Usually well underway within 2 astronomical units from the Sun (Mars being within that). So the questions outstanding are how did a comet get that close to the Earth without being sighted, how did it stay intact enough to cause a massive explosion in the atmosphere. Visibility varies based on comet composition. It got so deep because it didn't soak up enough heat to reach critical temperature until it was so deep. One theory is that it was a rocky object that came into the atmosphere at a nearly flat angle and at extremely high velocity (70,000 mph or more) and traveled several miles in the atmosphere and completely disintegrated in a multi-megaton explosion to where no significant meteorite remained. That scenario probably passes the physics test. Like I said it is still a mystery among scientists that have studied it. Several good theories but no conclusion. "No one knows for sure" doesn't equate to "my niche hypothesis is correct". -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
#50
|
|||
|
|||
Discussion on sci.space.science
On Thursday, August 16, 2018 at 4:03:53 PM UTC-4, Fred J. McCall wrote:
"Scott M. Kozel" wrote on Thu, 16 Aug 2018 The Tunguska object is a mystery. As you suggested a comet-like body melts and outgasses as it comes closer to the Sun. Usually well underway within 2 astronomical units from the Sun (Mars being within that). So the questions outstanding are how did a comet get that close to the Earth without being sighted, how did it stay intact enough to cause a massive explosion in the atmosphere. Visibility varies based on comet composition. It got so deep because it didn't soak up enough heat to reach critical temperature until it was so deep. One theory is that it was a rocky object that came into the atmosphere at a nearly flat angle and at extremely high velocity (70,000 mph or more) and traveled several miles in the atmosphere and completely disintegrated in a multi-megaton explosion to where no significant meteorite remained. That scenario probably passes the physics test. Like I said it is still a mystery among scientists that have studied it. Several good theories but no conclusion. "No one knows for sure" doesn't equate to "my niche hypothesis is correct". No, but that is one of the theories. …. https://science.nasa.gov/science-new...30jun_tunguska Quote: "A century later some still debate the cause and come up with different scenarios that could have caused the explosion," said Yeomans. "But the generally agreed upon theory is that on the morning of June 30, 1908, a large space rock, about 120 feet across, entered the atmosphere of Siberia and then detonated in the sky." It is estimated the asteroid entered Earth's atmosphere traveling at a speed of about 33,500 miles per hour. During its quick plunge, the 220-million-pound space rock heated the air surrounding it to 44,500 degrees Fahrenheit. At 7:17 a.m. (local Siberia time), at a height of about 28,000 feet, the combination of pressure and heat caused the asteroid to fragment and annihilate itself, producing a fireball and releasing energy equivalent to about 185 Hiroshima bombs. "That is why there is no impact crater," said Yeomans. "The great majority of the asteroid is consumed in the explosion." |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
I am stunned theres so little discussion here about the space suit malfunction | bob haller | Policy | 2 | December 25th 13 04:12 AM |
Great Griffin/ESAS Discussion At Space Politics | Rand Simberg[_1_] | Policy | 24 | May 23rd 07 07:21 PM |
sci.space.tech and sci.space.science Frequently Asked Questions (FAQ) | s.s.t moderator | Policy | 0 | April 18th 04 11:59 AM |
sci.space.tech and sci.space.science Frequently Asked Questions (FAQ) | s.s.t moderator | Policy | 0 | February 29th 04 12:00 PM |
sci.space.tech and sci.space.science Frequently Asked Questions (FAQ) | s.s.t moderator | Policy | 0 | February 22nd 04 12:00 PM |