How does a space suit on Mars work? Show me how it is pressurized, and how it is cooled
Why would you need spacesuit cooling on Mars? It's not space, where the side facing the sun heats up and it is difficult to radiate heat, there is an atmosphere that is quite chilly. I would think that you would need spacesuit heating on Mars, not cooling. However, I'm not a rocket scientist, is there anyone who has definitive knowledge on this topic?
At 6 millibar pressure, you are very close to a vacuum spacesuit environment; the atmosphere is not going to cool or heat you significantly*. Of course, the Sun is less intense on Mars, but if you are working and generating heat, I am sure you will need cooling.
* This is how the surface temperature in the Sun can be 25 C, while 1 meter up it's -25 C. If you were standing there, the heat from the surface would be much more important than the cooling from the atmosphere.
We would have seen them via gravitational microlensing. This provides a graph of the limits on dark matter, and the planetary mass range is excluded.
Also, planets (unlike condensed dark matter) would not evade the Big Bang Nucleosynthesis limits on baryonic matter, which rule this out for any mass range.
No. The dark matter is in a Halo (not quite spherical), which extends out from (roughly) maybe 2000 light years to 100,000.
It has to be more or less uniform to give the disk it's more or less flat rotation curve. If it was all on the edge, the mass inside wouldn't really feel it, and that wouldn't work.
The various limits on dark matter actually limit the ratio of the scattering cross section and the mass of whatever is making up the dark matter (this obviously does not apply to MOND type theories, which are different).
So, there are two ways to have a more-or-less non-interacting dark matter - have a small mass, and a very, very small cross section (as in WIMPs), or have a large mass, and a high density (as in quark matter DM theories). The large mass means that the scattering cross section can be more or less anything, and, specifically, can be what you would expect for regular matter.
Well, dead-reckoning between updates helps a lot too, as does having a good local map. But, yes, my cell phone GPS uses cell tower navigation more often than it uses actual GPS.
- GPS was designed as a mixed civilian / military system. That's why there WAS selective availability (AKA SA - fuzzing of civilian accuracy). SA was designed to give 30 meter accuracy, and lots of civilian needs could still be met with that accuracy. - Lots of us wondered why KAL 007 didn't have GPS - a 30 meter error was tiny compared to their actual error. - There was intense commercial interest in GPS in 1983. - Use of GPS has always been free - even under SA, you either had the keys to decrypt it, or not. - The real big push for commercial development came during the first Gulf War, when we didn't have nearly enough military units, and so Charley Trimble (Trimble Navigation - and others) got a huge order to send outdoor units to the Persian Gulf ASAP - AND they turned off Selective Availability (globally, for the duration).
The part about Clinton and SA was accurate. However, by the 90's. a lot of people were working on work-arounds for SA. SA implemented by making each satellite's clock go fast and slow deliberately, so you could fix it by having a ground station with a good clock looking at the same satellite, and sending corrections, so removing SA wasn't as big a deal as it would have been in 1985.
Term limits are massively stupid, and result in decision making being totally handed over to lobbyists. If you think it's too hard to vote people out, support the reform of apportionment.
These are attempts by corporations to obtain by stealth what they never could obtain from open political processes (you know, quaint things like votes in Congress or Parliament). Of course they don't want a public debate on it, which is why it is an "agreement," not a "treaty," even though they routinely and unconstitutionally try and give them the powers of treaties.
These agreements should be opposed as the fruit of an undemocratic and corrupt process, regardless of the actual content of the agreements. Of course, given the way they are negotiated, there is no shortage of substantiative things to oppose as well.
In galaxies, yes. In interacting galaxy clusters, like the Bullet Cluster, it has problems. (If you are interested, you should look at the papers that cite this one - there has been a long argument on the Bullet Cluster and MOND, and Milgrom certainly isn't convinced, but my opinion is MOND is in trouble or is incomplete on these large scales.
I believe that there are three possibilities here :
1.) A particle that interacts with normal matter via only the strong force, but evades the mass / cross section ratio limits on dark matter in some fashion.
2.) Matter that interacts with normal matter via all the usual forces, but evades the mass / cross section ratio limits on dark matter in some fashion. (Quark nuggets and primordial black holes fall into this category.)
3.) A particle that "strongly" interacts only with similar particles, by not the strong force, but by some new force.
I believe the present SIMPs are case number 3, that case number 2 aren't generally called "SIMPs", but case number 1 definitely has been so called; case number 1 particles have been significantly constrained in the past.
Well, then, you should check out MOND, which is a gravitational model, which fits really well most (but not all) of the observations, and is still hanging in there by the skin of its teeth (due to the other observations).
Yes, but that applies to the cosmological mass densities. The galaxy is much more dense than the cosmological average, and it is by no means clear how much of the galactic dark matter (which is what's relevant here) is baryonic. Some of it is, for sure (as there are nomadic planets, black holes, etc.), but how much is not well determined.
A slightly different question is, to what extent have physicists attempting to explain dark matter incorporated rogue planets into their calculations? The more that can be explained as rouge planets, the less needs to be explained as something else. Also, here is another point. The linked article indicates that M-class stars have 1/250 the mass of O-class stars, but are 250 times as common. So, imagine a planet 1/250 the mass of an M-class star --it should be 250 times as common as the M-class star. The Earth is about 1/330,000 the mass of our G-class sun, so Earth-size rogue planets should be 330,000 times as common as G-class stars. And so on. How does the total mass of all those different-sized smaller objects add up? THAT'S the result I've never seen get compared to the magnitude of dark matter. I'm not trying to say it will account for all of it, but it ought to take a decent bite out.
Gravitational microlensing and stellar and substellar number counts indicate that stars have roughly a power number relation between mass and number such that the total mass is more or less evenly spread over the various stellar masses (as you say), while there is a lot less mass in brown dwarfs, and their mass is dominated by the most massive objects. For nomadic planets (a term I much prefer to "rogue") it is not clear if the largest (Jupiter size and a little bigger) dominate the numbers, but it does seem clear that they dominate the total mass of the nomads.
Gravitational microlensing limits the number density of planets (roughly in the range from the mass of the Moon to the mass of Jupiter) to be significantly less than amount needed to explain the galactic dark matter.
Not only are they inventing a new particle, but a new force as well ? Which is needed to explain how the new particles behave ?
Really this seems to be nothing more than an attempt to create an explanation that doesn't make predictions and is as removed from testability as possible.
No one has yet lost any money betting against solutions for dark matter, so I am not going to get very excited about SIMPs (which, of course, are not really that new an idea anyway). Wait for it to get poked and prodded for a while, and then we'll see.
And the NASA HEMD guys say that to do that, you first need to have a deep space flight "with training wheels," i.e., one to something like high retrograde lunar orbit (far away to be serious, and actually test the deep space parts of the mission, but close enough you can meaningfully abort) and that, in practice, to both get the money for the test AND to make the test more realistic, the astronauts need some goal for spending 2 weeks orbiting outside the Moon, and the ARM provides that.
If the Earth had a well placed "mini-Moon" at the present, we could go to that, but as of right now, we don't appear to.
He seems to be looking at money spent on an asteroid project as money that could have been spent on HIS asteroid project. Meanwhile the money that is being spent is ultimately being spent to reduce further expenses on future space projects, maybe even his if he considered the potential merits of this mission he's seeking to squash.
I am not 100% sure that he is, but you are correct, he gives that impression. What is (IMHO) much more likely is that, if his ideas carry the day, ARM will be canceled and nothing will take its place and (with all due respect to Elon Musk) we will be set back another decade on going to Mars.
Note, however, that the asteroid survey mission could not be finished in time to provide a target for the first stage of ARM (or, to put it the other way, the ARM timetable does not allow for starting and running a survey mission from scratch). That means that HEMD (human space flight) is lukewarm on the survey mission and is not going to pay for it. Now, I regard that as a mistake, but I understand it.
Also, note that $ 200 million will not pay for a survey mission. That would be more like discovery class, i.e., $ 500 million or more.
He has been saying this for a while, most recently (to my knowledge) at the recent Small Bodies Assessment Group (SBAG) meeting in DC. I was there and have to say that the community (at least, the sample of the community in that room) did not come to even rough consensus on his proposal, and was in fact split roughly 50-50. There is, however, a pretty strong consensus on the funding of a asteroid survey mission, an infrared telescope on an interior orbit to the Earth to find most of the possible "city-buster" NEA. This is pretty much what the B612 foundation is proposing, but they haven't raised the money yet, nor is on any NASA funding plans.
My own personal opinion, FWIW, is that Binzel is wrong and that the ARM mission is a first good step to Mars.
You know that's kind of old school. There is this new technology called "digital communications" which means that they can read the instruments from miles away, removing the need for the bunker since the mid 1960's or so. There were no bunkers for the Saturn V (I believe the first Saturn I flights still had them) or the Shuttle - everything was monitored from ~ 3 miles away. At the Cape the Range Safety Officer looks at computer screens at the Range Operations Control Center at Cape Canaveral Air Force Station (probably 10 or 15 miles from the NASA launch sites on Merritt Island), and I am pretty sure similar practices are followed at Wallops.
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How does a space suit on Mars work? Show me how it is pressurized, and how it is cooled
Why would you need spacesuit cooling on Mars? It's not space, where the side facing the sun heats up and it is difficult to radiate heat, there is an atmosphere that is quite chilly. I would think that you would need spacesuit heating on Mars, not cooling. However, I'm not a rocket scientist, is there anyone who has definitive knowledge on this topic?
At 6 millibar pressure, you are very close to a vacuum spacesuit environment; the atmosphere is not going to cool or heat you significantly*. Of course, the Sun is less intense on Mars, but if you are working and generating heat, I am sure you will need cooling.
* This is how the surface temperature in the Sun can be 25 C, while 1 meter up it's -25 C. If you were standing there, the heat from the surface would be much more important than the cooling from the atmosphere.
We would have seen them via gravitational microlensing. This provides a graph of the limits on dark matter, and the planetary mass range is excluded.
Also, planets (unlike condensed dark matter) would not evade the Big Bang Nucleosynthesis limits on baryonic matter, which rule this out for any mass range.
No. The dark matter is in a Halo (not quite spherical), which extends out from (roughly) maybe 2000 light years to 100,000.
It has to be more or less uniform to give the disk it's more or less flat rotation curve. If it was all on the edge, the mass inside wouldn't really feel it, and that wouldn't work.
The various limits on dark matter actually limit the ratio of the scattering cross section and the mass of whatever is making up the dark matter (this obviously does not apply to MOND type theories, which are different).
So, there are two ways to have a more-or-less non-interacting dark matter - have a small mass, and a very, very small cross section (as in WIMPs), or have a large mass, and a high density (as in quark matter DM theories). The large mass means that the scattering cross section can be more or less anything, and, specifically, can be what you would expect for regular matter.
What I wonder is, did he get laid ? (After all, that was the root cause in that crash.)
Well, dead-reckoning between updates helps a lot too, as does having a good local map. But, yes, my cell phone GPS uses cell tower navigation more often than it uses actual GPS.
If you hit the ground, it's a crash.
And I was there.
Reagan may have sped up this or that, but
- GPS was designed as a mixed civilian / military system. That's why there WAS selective availability (AKA SA - fuzzing of civilian accuracy). SA was designed to give 30 meter accuracy, and lots of civilian needs could still be met with that accuracy.
- Lots of us wondered why KAL 007 didn't have GPS - a 30 meter error was tiny compared to their actual error.
- There was intense commercial interest in GPS in 1983.
- Use of GPS has always been free - even under SA, you either had the keys to decrypt it, or not.
- The real big push for commercial development came during the first Gulf War, when we didn't have nearly enough military units, and so Charley Trimble (Trimble Navigation - and others) got a huge order to send outdoor units to the Persian Gulf ASAP - AND they turned off Selective Availability (globally, for the duration).
The part about Clinton and SA was accurate. However, by the 90's. a lot of people were working on work-arounds for SA. SA implemented by making each satellite's clock go fast and slow deliberately, so you could fix it by having a ground station with a good clock looking at the same satellite, and sending corrections, so removing SA wasn't as big a deal as it would have been in 1985.
Term limits are massively stupid, and result in decision making being totally handed over to lobbyists. If you think it's too hard to vote people out, support the reform of apportionment.
These are not trade agreements.
These are attempts by corporations to obtain by stealth what they never could obtain from open political processes (you know, quaint things like votes in Congress or Parliament). Of course they don't want a public debate on it, which is why it is an "agreement," not a "treaty," even though they routinely and unconstitutionally try and give them the powers of treaties.
These agreements should be opposed as the fruit of an undemocratic and corrupt process, regardless of the actual content of the agreements. Of course, given the way they are negotiated, there is no shortage of substantiative things to oppose as well.
Modified Newtonian Dynamics explains it all.
In galaxies, yes. In interacting galaxy clusters, like the Bullet Cluster, it has problems. (If you are interested, you should look at the papers that cite this one - there has been a long argument on the Bullet Cluster and MOND, and Milgrom certainly isn't convinced, but my opinion is MOND is in trouble or is incomplete on these large scales.
I believe that there are three possibilities here :
1.) A particle that interacts with normal matter via only the strong force, but evades the mass / cross section ratio limits on dark matter in some fashion.
2.) Matter that interacts with normal matter via all the usual forces, but evades the mass / cross section ratio limits on dark matter in some fashion. (Quark nuggets and primordial black holes fall into this category.)
3.) A particle that "strongly" interacts only with similar particles, by not the strong force, but by some new force.
I believe the present SIMPs are case number 3, that case number 2 aren't generally called "SIMPs", but case number 1 definitely has been so called; case number 1 particles have been significantly constrained in the past.
Well, then, you should check out MOND, which is a gravitational model, which fits really well most (but not all) of the observations, and is still hanging in there by the skin of its teeth (due to the other observations).
Yes, but that applies to the cosmological mass densities. The galaxy is much more dense than the cosmological average, and it is by no means clear how much of the galactic dark matter (which is what's relevant here) is baryonic. Some of it is, for sure (as there are nomadic planets, black holes, etc.), but how much is not well determined.
A slightly different question is, to what extent have physicists attempting to explain dark matter incorporated rogue planets into their calculations? The more that can be explained as rouge planets, the less needs to be explained as something else. Also, here is another point. The linked article indicates that M-class stars have 1/250 the mass of O-class stars, but are 250 times as common. So, imagine a planet 1/250 the mass of an M-class star --it should be 250 times as common as the M-class star. The Earth is about 1/330,000 the mass of our G-class sun, so Earth-size rogue planets should be 330,000 times as common as G-class stars. And so on. How does the total mass of all those different-sized smaller objects add up? THAT'S the result I've never seen get compared to the magnitude of dark matter. I'm not trying to say it will account for all of it, but it ought to take a decent bite out.
Gravitational microlensing and stellar and substellar number counts indicate that stars have roughly a power number relation between mass and number such that the total mass is more or less evenly spread over the various stellar masses (as you say), while there is a lot less mass in brown dwarfs, and their mass is dominated by the most massive objects. For nomadic planets (a term I much prefer to "rogue") it is not clear if the largest (Jupiter size and a little bigger) dominate the numbers, but it does seem clear that they dominate the total mass of the nomads.
Gravitational microlensing limits the number density of planets (roughly in the range from the mass of the Moon to the mass of Jupiter) to be significantly less than amount needed to explain the galactic dark matter.
Not only are they inventing a new particle, but a new force as well ? Which is needed to explain how the new particles behave ?
Really this seems to be nothing more than an attempt to create an explanation that doesn't make predictions and is as removed from testability as possible.
No, that would be sterile neutrinos.
Then you will be relived that there is still just a little breathing room for MACHOS.
No one has yet lost any money betting against solutions for dark matter, so I am not going to get very excited about SIMPs (which, of course, are not really that new an idea anyway). Wait for it to get poked and prodded for a while, and then we'll see.
And the NASA HEMD guys say that to do that, you first need to have a deep space flight "with training wheels," i.e., one to something like high retrograde lunar orbit (far away to be serious, and actually test the deep space parts of the mission, but close enough you can meaningfully abort) and that, in practice, to both get the money for the test AND to make the test more realistic, the astronauts need some goal for spending 2 weeks orbiting outside the Moon, and the ARM provides that.
If the Earth had a well placed "mini-Moon" at the present, we could go to that, but as of right now, we don't appear to.
He seems to be looking at money spent on an asteroid project as money that could have been spent on HIS asteroid project. Meanwhile the money that is being spent is ultimately being spent to reduce further expenses on future space projects, maybe even his if he considered the potential merits of this mission he's seeking to squash.
I am not 100% sure that he is, but you are correct, he gives that impression. What is (IMHO) much more likely is that, if his ideas carry the day, ARM will be canceled and nothing will take its place and (with all due respect to Elon Musk) we will be set back another decade on going to Mars.
Note, however, that the asteroid survey mission could not be finished in time to provide a target for the first stage of ARM (or, to put it the other way, the ARM timetable does not allow for starting and running a survey mission from scratch). That means that HEMD (human space flight) is lukewarm on the survey mission and is not going to pay for it. Now, I regard that as a mistake, but I understand it.
Also, note that $ 200 million will not pay for a survey mission. That would be more like discovery class, i.e., $ 500 million or more.
He has been saying this for a while, most recently (to my knowledge) at the recent Small Bodies Assessment Group (SBAG) meeting in DC. I was there and have to say that the community (at least, the sample of the community in that room) did not come to even rough consensus on his proposal, and was in fact split roughly 50-50. There is, however, a pretty strong consensus on the funding of a asteroid survey mission, an infrared telescope on an interior orbit to the Earth to find most of the possible "city-buster" NEA. This is pretty much what the B612 foundation is proposing, but they haven't raised the money yet, nor is on any NASA funding plans.
My own personal opinion, FWIW, is that Binzel is wrong and that the ARM mission is a first good step to Mars.
You know that's kind of old school. There is this new technology called "digital communications" which means that they can read the instruments from miles away, removing the need for the bunker since the mid 1960's or so. There were no bunkers for the Saturn V (I believe the first Saturn I flights still had them) or the Shuttle - everything was monitored from ~ 3 miles away. At the Cape the Range Safety Officer looks at computer screens at the Range Operations Control Center at Cape Canaveral Air Force Station (probably 10 or 15 miles from the NASA launch sites on Merritt Island), and I am pretty sure similar practices are followed at Wallops.
Thanks for clearing that up.
I heard on twitter that this was not the crowdfunding satellite, but an early test, so your investment may be OK.