The Solar
Probe is a proposed
satellite mission to
investigate the outer layer of the
Sun at close quarters (within 2 million kilometres/3 solar radii of the
surface). Tentatively planned for a launch in 2007,
NASA hope this probe will aid their understanding several questions about the Sun and its
structure, such as:
What heats the Corona so that it exceeds the surface temperature (ie that at the chromosphere) of the Sun ?
Where does the solar wind originate, and what force accelerates it to the fantastic speeds it can reach ?
What processes transport energetic particles in the Corona?
How are the magnetic fields arranged at the Suns magnetic poles?
It is planned to send the probe around the Sun by 'slingshotting' the unit around Jupiter, so as to place it in a highly elliptical orbit.Suggestions are now coming in for the proposed payload, including such measuring devices as magnetometers, spectrographs and particle detectors. Scientists are even proposing plans to catch some of the so-called stardust, the charged particles in the Suns corona.
One of the major design problems has been how to make sure the probe can get close enough to the Sun to take readings without melting, as the unit is exposed to 3000 times more solar energy than we recieve here on Earth, which gives rise to temperature of around 2400 Kelvin. One of the solutions proposed is to shield the scientific instruments with a specially treated carbon mask, that places the instuments in a protective umbra. This mask is made from carbon fibre, which is soaked in an epoxy resin, before being placed in a furnace to reduce the expoy to cabon, essentially giving you a carbon fibre held together with carbon cross links (very similar to the substance that the nose cones of nuclear missiles are made from). This substance is then sprayed with liquid methane, which supposedly fills in any pores in the heat shield. Scientists are at a loss as to why this process helps the unit stand more heat, but according to the rigorous testing that the shield has been put through, it does. The shield is also going to be rigged to act as the radio antennae to transmit signals back to us here on Earth.
Information taken from:
http://www.newscientist.com/features/features.jsp?id=ns22741
http://www.jpl.nasa.gov/ice_fire//sprobe.htm
http://outerplanets.larc.nasa.gov/outerplanets/Radiation_Environ2.pdf
http://www.tayloru.edu/upland/departments/physics/whatsnew/sol.htm