Mach number is not just the speed of sound in air at sea level. It is used by mechanical engineers all the time because it applies to ALL fluids. Every fluid (yes, air is a fluid) has a Mach number. Mach numbers are useful in many types of calculations other than "the speed when you hear the boom"
I have to give the European's credit for aestetics if nothing else. The pictures coming back from Mars Express are gorgeous. I don't know how much more science you get out of something like that instead of the not-quite-so-stunning pictures that NASA's probes have yielded, but if you're looking for a neat backgroud and your tired of what's on Digital Blasphemy, ESA has it.
I'm not saying I don't like what the MERs have sent back, but some of the ESA stuff is pretty sweet looking
Space probes don't send back jpegs or gifs. The images have to be assembled and processed to remove compression artifacts and "hot spots" where an errant gamma ray or ion hit a CCD and caused a big bright spot.
There will always be a delay between the raw data is recieved through the Deep Space Network and when it will show up on a computer screen at JPL because it has to be properly assembled. Not tin foil (I hate that term...it's actually aluminum foil) hat stuff, just the nature of the game.
These scientists are too much for me with all there fancy-sounding units of measurement. I want measurements in hogsheads and cubits like any other normal person
Before you start jumping up and down here, think about a few of the facts first.
wouldnt we get better performance long-term from a larger number of smaller probes?
Most of the cost goes into getting to these very far away places and holding enough propellent that you can slow down enough to be captured into orbit after you've been going very fast for a few years. It's not feasible to launch probes to outer planets all the time because you lose the ability to "sling shot" past other planets as a cheap way to pick up a lot of speed. These gravity assist (or more accuratley, angular momentum assist) moves make a little ship go whole heck of a lot faster which means you don't need as much propellent to get you somewhere. You have to go really fast to someplace that several billion miles away in a few years.
and hence would have more up-to-date sensors. For example, the CCD on the Cassini camera is only 1 megapixel!
The way to get better quality pics is NOT to have more pixels but to have better optics. The cameras in the "eyes" of the Mars Exploration Rovers (the pancam) are only about 1 megapixel and they have returned VERY high resolution pics that look great if you have to blow them up 10 times their size. That's because NASA spends a lot of money to use phenomonally good optics. In addition, more megapixels means larger files which requires higher data transfer rates which requires more power to your antenna which means less electricity to do other stuff. (whew)
I have heard it suggested that most of the useful function of the JIMO $10 billion orbiter could be done with a simpler $1 billion direct-to-europa mission.. And look at New Horizons, with a mission cost less $1 billion, or SMART-1 less than $100 million..
Dude, compare apples to apples here. SMART-1 is a test of new technology (ion drive) that is meant to see how well it works and if it useable in other missions. It was meant to be a cheap way to get to the moon. You don't need a whole lot of force to get the moon and orbit it if you're willing to wait a few years...like SMART is. To get to Jupiter and then ORBIT it, you have to go very fast to get there, then be strong enough to slow down to be captured into orbit. Then maybe you'd want a few kilos of propellent left to actually move around near Jupiter for a few year. That is a completely different scope than crusing along to the moon for several years or flying by Pluto-Charon before the atmosphere freezes out.
You don't necessarily need sunspots to make auroras. Sunsposts themselves don't cause auroras anyway. Auroras are caused by charged particles slamming into Earth's magnetic field, not by tanlged messes near the sun. It's just that sometimes these tangled messes collape and a whole bunch of sun-stuff (read: plasma) spits out in what is called a Corona Mass Ejection. If one of these CMEs hits Earth, it's aurora time.
Charged particles stream off the sun all the time anyway, the solar wind. This causes auroras all year round, it you're far enough North (or South for you Aussies). You can sometimes get CMEs when things called solar filaments collape (sort of like sun spots, but not) or when there are holes in the corona of the sun that let more solar wind squirt out.
I don't think it was a case of overly padding their estimates, but some condervative assumptions turned out to be way off.
Originally, they thought dusk accumulation on the solar panels would be a much larger problem. They estimated that the panels would be sufficiently covered to not produce enough juice about 100 days in. It turns out, the panels just aren't getting all that dirty and the terrain is hilly enough that you can park the rover on a North-facing slope to increase power.
As for the other components, they spend so much time making them small and light that they invariabley are forced to use high quality components that go way past their L10 (the time at which 10% of a lot of parts will fail)
Overall, it's probably more good luck and proper planning than a tin-foil hat consipriacy to make NASA look good
If anyone deserves to be a little whimsical from time to time, it's the guys who sit around and figure out why the Universe is the way it is. I wasn't saying that the names aren't technical or serious enough, there's enough complexity in the name Quantum Chromodynamics to make most undergrads head's spin, they don't need the names of the elementry particles to be alpha, beta, gamma, etc.
I just find it funny that in trying to discover a theory of everything, we use a phrase from Finnegan's Wake
As much as I'd love to have a "Theory of Everything" I think the scientific community needs to do something about the names given to the different "flavors" of quarks before we move any further with this theory.
For those of you who don't know, there are six flavors of quarks that we know of, their names are (and I swear I am not making this up) Up, Down, Charm, Strange, Top and Bottom. Charm and Strange? Do you ever think this was a joke among physicists that just got out of hand
Actually, the method SpaceShipOne uses to re-enter the atmosphere is pretty robust and safe.
Most times, entry vehicles use a blunt end - think the bottom of the Apollo capsule - to slow down through a process called 'aerobraking'. If a vehicle starts to spin rapidly during that time, bad things happen. SSO can enter the atmosphere in any orientation - nose down, nose up, sideways - and it will be OK because of it's back wing surface. In an orientation the Scaled guys call "feathering" the back end flips up 90 degrees in a high drag configuration. This forces the nose into the atmosphere at the right angle, so spinning isn't a vehicle loss issue
Still, you go a lot slower re-entering from a suborbital flight than an orbital speed re-entry a la Columbia circa 2003
Slashdot Mirror
That's why the guys who design props on subs get paid the big bucks.
Mach number is not just the speed of sound in air at sea level. It is used by mechanical engineers all the time because it applies to ALL fluids. Every fluid (yes, air is a fluid) has a Mach number. Mach numbers are useful in many types of calculations other than "the speed when you hear the boom"
I'm not saying I don't like what the MERs have sent back, but some of the ESA stuff is pretty sweet looking
ESA's Mars Express
There will always be a delay between the raw data is recieved through the Deep Space Network and when it will show up on a computer screen at JPL because it has to be properly assembled. Not tin foil (I hate that term...it's actually aluminum foil) hat stuff, just the nature of the game.
Me: Nevermind
These scientists are too much for me with all there fancy-sounding units of measurement. I want measurements in hogsheads and cubits like any other normal person
wouldnt we get better performance long-term from a larger number of smaller probes?
Most of the cost goes into getting to these very far away places and holding enough propellent that you can slow down enough to be captured into orbit after you've been going very fast for a few years. It's not feasible to launch probes to outer planets all the time because you lose the ability to "sling shot" past other planets as a cheap way to pick up a lot of speed. These gravity assist (or more accuratley, angular momentum assist) moves make a little ship go whole heck of a lot faster which means you don't need as much propellent to get you somewhere. You have to go really fast to someplace that several billion miles away in a few years.
and hence would have more up-to-date sensors. For example, the CCD on the Cassini camera is only 1 megapixel!
The way to get better quality pics is NOT to have more pixels but to have better optics. The cameras in the "eyes" of the Mars Exploration Rovers (the pancam) are only about 1 megapixel and they have returned VERY high resolution pics that look great if you have to blow them up 10 times their size. That's because NASA spends a lot of money to use phenomonally good optics. In addition, more megapixels means larger files which requires higher data transfer rates which requires more power to your antenna which means less electricity to do other stuff. (whew)
I have heard it suggested that most of the useful function of the JIMO $10 billion orbiter could be done with a simpler $1 billion direct-to-europa mission.. And look at New Horizons, with a mission cost less $1 billion, or SMART-1 less than $100 million..
Dude, compare apples to apples here. SMART-1 is a test of new technology (ion drive) that is meant to see how well it works and if it useable in other missions. It was meant to be a cheap way to get to the moon. You don't need a whole lot of force to get the moon and orbit it if you're willing to wait a few years...like SMART is. To get to Jupiter and then ORBIT it, you have to go very fast to get there, then be strong enough to slow down to be captured into orbit. Then maybe you'd want a few kilos of propellent left to actually move around near Jupiter for a few year. That is a completely different scope than crusing along to the moon for several years or flying by Pluto-Charon before the atmosphere freezes out.
Charged particles stream off the sun all the time anyway, the solar wind. This causes auroras all year round, it you're far enough North (or South for you Aussies). You can sometimes get CMEs when things called solar filaments collape (sort of like sun spots, but not) or when there are holes in the corona of the sun that let more solar wind squirt out.
Originally, they thought dusk accumulation on the solar panels would be a much larger problem. They estimated that the panels would be sufficiently covered to not produce enough juice about 100 days in. It turns out, the panels just aren't getting all that dirty and the terrain is hilly enough that you can park the rover on a North-facing slope to increase power.
As for the other components, they spend so much time making them small and light that they invariabley are forced to use high quality components that go way past their L10 (the time at which 10% of a lot of parts will fail)
Overall, it's probably more good luck and proper planning than a tin-foil hat consipriacy to make NASA look good
If anyone deserves to be a little whimsical from time to time, it's the guys who sit around and figure out why the Universe is the way it is. I wasn't saying that the names aren't technical or serious enough, there's enough complexity in the name Quantum Chromodynamics to make most undergrads head's spin, they don't need the names of the elementry particles to be alpha, beta, gamma, etc.
I just find it funny that in trying to discover a theory of everything, we use a phrase from Finnegan's Wake
As much as I'd love to have a "Theory of Everything" I think the scientific community needs to do something about the names given to the different "flavors" of quarks before we move any further with this theory. For those of you who don't know, there are six flavors of quarks that we know of, their names are (and I swear I am not making this up) Up, Down, Charm, Strange, Top and Bottom. Charm and Strange? Do you ever think this was a joke among physicists that just got out of hand
Actually, the method SpaceShipOne uses to re-enter the atmosphere is pretty robust and safe. Most times, entry vehicles use a blunt end - think the bottom of the Apollo capsule - to slow down through a process called 'aerobraking'. If a vehicle starts to spin rapidly during that time, bad things happen. SSO can enter the atmosphere in any orientation - nose down, nose up, sideways - and it will be OK because of it's back wing surface. In an orientation the Scaled guys call "feathering" the back end flips up 90 degrees in a high drag configuration. This forces the nose into the atmosphere at the right angle, so spinning isn't a vehicle loss issue Still, you go a lot slower re-entering from a suborbital flight than an orbital speed re-entry a la Columbia circa 2003