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Messenger Spacecraft Prepared for Mercury
An anonymous reader writes "NASA's first orbiter to the planet Mercury is shown today in cut-away, revealing the parasol design that will protect it from intense heat. Twenty layers of aluminized Kapton will be its sunshade. Curiously since the innermost planet is so close to the Sun, the Mercury mission itself will look for (cometary) water-ice preserved on the less baked north pole."
"My future's so bright, I've got to wear shades."
The outside of this 6-foot solar umbrella will rise to 680F (360C), while its special insulating properties will keep its inside surface below 212F (100C) - and the spacecraft operating at room temperature.
How can you keep the spacecraft at room temperature if everything around it is at least 212F? I need to get some of those fans for my computer.
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Being the closest planet to the Sun you would expect Mercury to be the hottest but this is not true. Mercurys maximum temperature falls 50C short of that of Venus. The reason for this is that Mercury has very little atmosphere so there is no 'greenhouse' effect on the environment. The 430C daytime temperature is dictated purely by the Suns radiation. The Mercurian day is 176 terrestrial days long, the night is 88 terrestrial days long with a minimum temperature of -180C.
Be very, very careful what you put into that head, because you will never, ever get it out. -Thomas Cardinal Wolsey
Sure there are lotsa other places to look too but this is a tidally-locked object not far from where many inner-system comets end up, ie the Sun. It'd be curiouser if Mercury hadn't intercepted a few comets over the eons and there weren't some traces of those collisions left on the benign parts of the planet.
I don't read ACs: If a post isn't worth so much as a nom de plume to its author then I wont bother either.
Dubya's new space initiative to look for extraterrestrial oil hasn't filtered through to the mission planners yet...
(Just proof that any dumb @$$ can get elected in America...ooooh, pretty shiney!)
Is it just my observation, or are there way too many stupid people in the world?
This image beautifully illustrates the multilayered approach the team devised to fend off the excess heat while the spacecraft is near Mercury
Are we looking a the same picture?
This is not an informative image.
It could just as well be Fruit Fucker Prime with a tarp over it.
Impressive technology. Abysmal photography.
You're thinking of a solar sail. Ion drives derive thrust directly from the force of the escaping gas (lightweight but high energy), generally xenon.
Trying to ride the 'wind' from your own ion drive is very similar to trying to windsurf by blowing into your own sail -- or, to use a more familiar analogy, pulling one's self up by one's own bootstraps.
They should send a rover on over.
Mercury must have some interesting elements collected from solar winds.
A good landing site would be on the dark side obviously to avoid overheating.
However, if I remember correctly, Mercury also sports the coldest temps in the solar system due to its rapid evaporation.
Kind of like the cooling effect one gets when a wind blows on wet skin.
But I somehow doubt those rumors with it being so close to the sun.
So how about playing on the transitional areas of light and dark areas.
This planet was thought to be like our moon in that the same face points towards the Sun, leaving a perpetual dark and light side. However, it was shown to have a strange rotation of three rotations every two of its years.
What I would like to see from a rover is a video showing the sunsets and sunrises.
Its suppose to be really bizarre.
The sun rises and picks up speed as it grows in size! Then it pauses at the top and reverses the process.
If they did find ice water on the planet, do you think huddling some poor humans in a crater there would be beneficial or sacrificial?
Just some musings.
when I was about 3 years old, I took my matchbox cars, and mounted a magnet on the front of one. Then I took a metal beam from my erector set, taped it to the top of my car, and put one end way out in front, on which I taped another magnet, opposite poles facing each other. It took me a couple of seconds to realize why it wasn't going to work :-) It sounds pretty similer to an ion drive pushing it's own sail.
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Kapton is a polyamide film duPont product that's been around for some 30 years . . .
I wonder if its the same metalized film used in some automobile window heat shields (or might that be metalized biaxially oriented nylon film)?
For comparison purposes the best Isp from a chemical rocket system in use is pretty much Lox/H2 which gives you an Ispvac in the 460s range.
More info here: http://nmp.jpl.nasa.gov/ds1/tech/ionpropfaq.html
And yes, I am a rocket scientist.
Let me define a few things real quick
It=total Impulse=Thrust*Time [N-s]
F=Thrust [N]
t= time [s]
Mp=Propellant Mass [kg]
dMp/dt=Propllant mass flow rate [kg/s]
Wp=Propellant weight [N]
Isp=It/Wp=F*t/(Mp*g)
which if you solve for F in terms of Isp you get:
F=Isp*Mp*g/t
Then, you have Newton's law: F=dP/dt=d(mv)/dt which for a constat exit velocity you get:
F=Ve*dMp/dt
which for a constant mass flow can be written as:
F=Ve*Mp/t
Setting the two equations for thrust together you get:
F=Isp*Mp*g/t=Ve*Mp/t
which if you cancel out the Mp/t on both sides of the equation you get that:
Ve=Isp*g.
One of the real nice things about using Isp is that it's one of the few things that is the same in both EE and metric because it's units are seconds. For more info on this I recomend Chapter 2 from 'Rocket Propulsion Elements' by George Sutton and for a more advanced look at this stuff check out 'Space Propulsion Analysis and Design' By Humble, Henry and Larson. Both books can be purchased through Amazon or other large book sellers.