Today, science and manned spaceflight are nearly mutually exclusive at NASA, unfortunately. I expect these initiatives will have the same effect on science that the Space Station had -- largely negative. The following is from http://nightquill.blogspot.com/
I started dissertation work when I was 23.
I knew an astrophysicist was what I longed to be.
I wanted to build satellites that gaze up at the stars,
But Mama, I don't wanna go to Mars.
Oh Mama, I don't wanna go to Mars.
I hear there aren't very many bars.
They won't let you bring cigarettes, or even fine cigars.
Oh Mama, I don't wanna go to Mars.
They said "Your research must support the Exploration Vision,
And if you can't adapt to it, you might as well go fishin' ".
But no one bought my argument that spaceflight would be over
If astronauts encountered an uncharted supernova!
Oh Mama, I don't wanna go to Mars.
Don't want to show those NASA medics my appendix scars.
They force you to relieve yourself in tiny little jars.
Oh Mama, I don't wanna go to Mars.
Now if we beg a thousand times they might just save the Hubble --
And leave the rest of science in a thousand kinds of trouble.
And planetary scientists expecting great largesse
Should think of all the science that gets done on ISS!
Oh Mama, I don't wanna go to Mars.
Don't care if lower gravity helps golfers shoot more pars.
In space no one can hear us when we play on our guitars.
Oh Mama, I don't wanna go to Mars.
I still don't know just how we're gonna pay for it.
But please don't take my little grants away for it.
Look in on any campus and you'll see who will be hurtin'
While all those no-bid moonbase contracts go to Halliburton!
Oh Mama, I don't wanna go to Mars.
Just count me with the "no we're nots" and not the "yes we ares",
Let's keep on sending orbiters and funny little cars,
But Mama, I don't wanna go,
And there's no way I'm gonna go,
Mama...I...don't...want...to...go...to.....
[tune changes to "Rocket Man"]: Mars....ain't the kind of place to raise your kids.....
[back to tempo]: So Mama, I don't wanna go to Mars!
Six.
Five.
Four.
Three.
Two.
One........No funds.
--Anonymous
You can actually get a cheap GPS for ballooning which, instead of being disabled at high altitudes, is disabled at high speeds. We used this for small balloons in Antarctica this year and it works fine. I presume the reason it's OK is that under this restriction, as well, you still couldn't use it for a rogue ICBM.
We once had to hack the flight software at the last minute for a major scientific balloon funded by NASA; the launch was happening in the early hours of January 1, and we found a fencepost error in the navigation software that cropped up when the year turned over. Note that this was not a NASA error, it was my lame-ass grad-student self at a university I will not name who screwed up. But we did get it fixed just a few hours before launch.
If NASA decides to send a version of this to Mars, they will absolutely redesign it to make sure it can operate under Martian conditions, and then test it in a thermal/vacuum chamber at real Martian temperatures and pressures before they let it fly. Also, they will subject it to simulated launch vibrations. Testing for radiation endurance is usually done at the microchip level before assembly rather than with the finished instrument.
This process is somewhat expensive, but an incredible bargain compared to manned spaceflight.
Unless you're a scientist in this field, you just
don't know how much information those scientists have. You certainly won't find out in sufficient
detail from newspaper articles (that would be
impossible) to make your own judgement of how
certain we are of what's causing global warming,
ozone depletion, etc.....
Gravitation is a theory, but
it based on a large enough set of observations
(facts) that we are confident in basing public
policy (i.e. bridge design) on it. So it's not
a question of what's a "theory" or what's a "fact", but of how good a set of observations
a theory is based on. CFCs -> ozone depletion
is based on such a vast and precise set of
observations that no one has seriously questioned
it for years, it influenced public policy, and
those policies have already begun to show
improvements. Global warming due to CO2
is not quite at that level, but clearly
getting there.....
Now here's some interesting atmospheric chemistry
surrounding CFCs and solar flares. The solar
flares produce reactive nitrogen compounds
(called "odd nitrogen") which can destroy ozone
catalytically, just line chlorine does. But
these reactions proceed more slowly, so one
odd nitrogen molecule is not as bad as one
chlorine atom.
However, when the atmosphere is heavily loaded
with chlorine, the odd nitrogen molecule will
readily bind with a chlorine atom, rendering
both of them harmless to ozone. So if we had
never started curbing CFCs, and the chlorine
load was much higher than it actually is, then
the solar flares might actually have helped
*reverse* ozone depletion a bit. Not enough
to fix things, of course.....
I believe x-rays of these energies (a couple of hundred keV) can go
through many meters of air (tens to hundreds) -- at least enough of
them to register on the detector. Some luck involved, of course, but
they looked long enough to get it.
Second thing, although you are
absolutely right that bremsstrahlung gets more efficient with higher Z
(and with higher energy), it will never be more than about 10 to 20%
of the energy loss for electrons of these energies (about an MeV, give
or take a factor of a few). Most of the loss will still be by
ionization and excitation of air. So bremsstrahlung won't suddenly
take over and start dominating the physics, I think, for this reason
and because there will be just a lot more air around than evaporated
wire. If I were a real lightning physicist I could address your idea that
there is heating due to pinching by the magnetic field, but I won't try.
As for the x-ray intensity, I get the impression that it's much less
than a chest x-ray, and lasts much less time as well.
In fact,
Joe Dwyer at Florida Tech studies x-rays from lightning seen on the ground (the source only
meters away), and he saw *one*
event where there were MeV gamma-rays too, which he thinks were coming from about 6 km up. The total dose, though, from that high-up event, was really tiny. Much, much less than other kinds of natural radioactivity. There's a somewhat more substantial x-ray dose from being within a few meters of a lightning strike, but then you have bigger problems.
-David Smith (1st author of the Science paper)
A little elaboration beyond what went into the Science paper.....
Well, they're both above thunderstorms and both
require high E-fields, but.....a TGF will happen
within about a millisecond of the related lightning stroke, while sprites can be delayed for up to hundreds of milliseconds. Also, the sprites last much longer than a TGF. There's another paper just submitted to another journal, which I shouldn't comment on the details of yet because I'm not the first author, but from what we're seeing from radio data I'm guessing that most TGFs will not turn out to be accompanied by a sprite. There may be a different optical signature associated with them, but it probably wouldn't be as spectacular as a sprite (which look like giant red jellyfish). -David Smith (the first author of the Science paper)
Actually it's bremsstrahlung, but you have the
right point -- you don't need any baryons
accelerated or nuclei altered, just have the electrons bounce off some nuclei and you'll
get the gammas.
-David Smith (the author)
[how cool that the article got here:) ]
Slashdot Mirror
Today, science and manned spaceflight are nearly mutually exclusive at NASA, unfortunately. I expect these initiatives will have the same effect on science that the Space Station had -- largely negative. The following is from http://nightquill.blogspot.com/ I started dissertation work when I was 23. I knew an astrophysicist was what I longed to be. I wanted to build satellites that gaze up at the stars, But Mama, I don't wanna go to Mars. Oh Mama, I don't wanna go to Mars. I hear there aren't very many bars. They won't let you bring cigarettes, or even fine cigars. Oh Mama, I don't wanna go to Mars. They said "Your research must support the Exploration Vision, And if you can't adapt to it, you might as well go fishin' ". But no one bought my argument that spaceflight would be over If astronauts encountered an uncharted supernova! Oh Mama, I don't wanna go to Mars. Don't want to show those NASA medics my appendix scars. They force you to relieve yourself in tiny little jars. Oh Mama, I don't wanna go to Mars. Now if we beg a thousand times they might just save the Hubble -- And leave the rest of science in a thousand kinds of trouble. And planetary scientists expecting great largesse Should think of all the science that gets done on ISS! Oh Mama, I don't wanna go to Mars. Don't care if lower gravity helps golfers shoot more pars. In space no one can hear us when we play on our guitars. Oh Mama, I don't wanna go to Mars. I still don't know just how we're gonna pay for it. But please don't take my little grants away for it. Look in on any campus and you'll see who will be hurtin' While all those no-bid moonbase contracts go to Halliburton! Oh Mama, I don't wanna go to Mars. Just count me with the "no we're nots" and not the "yes we ares", Let's keep on sending orbiters and funny little cars, But Mama, I don't wanna go, And there's no way I'm gonna go, Mama...I...don't...want...to...go...to..... [tune changes to "Rocket Man"]: Mars....ain't the kind of place to raise your kids..... [back to tempo]: So Mama, I don't wanna go to Mars! Six. Five. Four. Three. Two. One........No funds. --Anonymous
You can actually get a cheap GPS for ballooning which, instead of being disabled at high altitudes, is disabled at high speeds. We used this for small balloons in Antarctica this year and it works fine. I presume the reason it's OK is that under this restriction, as well, you still couldn't use it for a rogue ICBM.
We once had to hack the flight software at the last minute for a major scientific balloon funded by NASA; the launch was happening in the early hours of January 1, and we found a fencepost error in the navigation software that cropped up when the year turned over. Note that this was not a NASA error, it was my lame-ass grad-student self at a university I will not name who screwed up. But we did get it fixed just a few hours before launch.
This process is somewhat expensive, but an incredible bargain compared to manned spaceflight.
...so it's much more reliable to assume that the truth is whatever you wish it were, of course.
Unless you're a scientist in this field, you just don't know how much information those scientists have. You certainly won't find out in sufficient detail from newspaper articles (that would be impossible) to make your own judgement of how certain we are of what's causing global warming, ozone depletion, etc..... Gravitation is a theory, but it based on a large enough set of observations (facts) that we are confident in basing public policy (i.e. bridge design) on it. So it's not a question of what's a "theory" or what's a "fact", but of how good a set of observations a theory is based on. CFCs -> ozone depletion is based on such a vast and precise set of observations that no one has seriously questioned it for years, it influenced public policy, and those policies have already begun to show improvements. Global warming due to CO2 is not quite at that level, but clearly getting there..... Now here's some interesting atmospheric chemistry surrounding CFCs and solar flares. The solar flares produce reactive nitrogen compounds (called "odd nitrogen") which can destroy ozone catalytically, just line chlorine does. But these reactions proceed more slowly, so one odd nitrogen molecule is not as bad as one chlorine atom. However, when the atmosphere is heavily loaded with chlorine, the odd nitrogen molecule will readily bind with a chlorine atom, rendering both of them harmless to ozone. So if we had never started curbing CFCs, and the chlorine load was much higher than it actually is, then the solar flares might actually have helped *reverse* ozone depletion a bit. Not enough to fix things, of course.....
I believe x-rays of these energies (a couple of hundred keV) can go through many meters of air (tens to hundreds) -- at least enough of them to register on the detector. Some luck involved, of course, but they looked long enough to get it.
Second thing, although you are absolutely right that bremsstrahlung gets more efficient with higher Z (and with higher energy), it will never be more than about 10 to 20% of the energy loss for electrons of these energies (about an MeV, give or take a factor of a few). Most of the loss will still be by ionization and excitation of air. So bremsstrahlung won't suddenly take over and start dominating the physics, I think, for this reason and because there will be just a lot more air around than evaporated wire. If I were a real lightning physicist I could address your idea that there is heating due to pinching by the magnetic field, but I won't try.
As for the x-ray intensity, I get the impression that it's much less than a chest x-ray, and lasts much less time as well.
One more cool thing in closing: there are groups trying to trigger lightning with a laser (of a suitable wavelength to cause ionization, I presume), and apparently the Japanese have already done so a couple of times: http://www.spie.org/app/publications/magazines/oer archive/july/jul99/laserlight.html
Cheers,
--David
Hmph, that's right, out me to the Nerds of the World :)
-David
In fact, Joe Dwyer at Florida Tech studies x-rays from lightning seen on the ground (the source only meters away), and he saw *one* event where there were MeV gamma-rays too, which he thinks were coming from about 6 km up. The total dose, though, from that high-up event, was really tiny. Much, much less than other kinds of natural radioactivity. There's a somewhat more substantial x-ray dose from being within a few meters of a lightning strike, but then you have bigger problems. -David Smith (1st author of the Science paper)
A little elaboration beyond what went into the Science paper..... Well, they're both above thunderstorms and both require high E-fields, but.....a TGF will happen within about a millisecond of the related lightning stroke, while sprites can be delayed for up to hundreds of milliseconds. Also, the sprites last much longer than a TGF. There's another paper just submitted to another journal, which I shouldn't comment on the details of yet because I'm not the first author, but from what we're seeing from radio data I'm guessing that most TGFs will not turn out to be accompanied by a sprite. There may be a different optical signature associated with them, but it probably wouldn't be as spectacular as a sprite (which look like giant red jellyfish). -David Smith (the first author of the Science paper)
Yes, exactly..... -David Smith (the author)
Actually it's bremsstrahlung, but you have the right point -- you don't need any baryons accelerated or nuclei altered, just have the electrons bounce off some nuclei and you'll get the gammas. -David Smith (the author) [how cool that the article got here :) ]