Hayabusa 2’s target asteroid, 1999 JU3, is about 900 meters (3,000 feet) in diameter and generally circles the Sun between the orbits of Earth and Mars, rotating with a period of about seven and a half hours. - See more at: http://www.skyandtelescope.com/astronomy-news/hayabusa-2-asteroid-bound-12032014/#sthash.mzSaf6fO.dpuf
(162173) 1999 JU3: C-type asteroid
Size: about 900 meters (3,000 feet)
a = 1.1896212 AU
Period (around sun) = 1.30 years
Period (around itself) = 7.6 hours
Discovered 1999-May-10 by LINEAR at Socorro (704)
The German Aerospace Center built a small lander called MASCOT (Mobile Asteroid Surface Scout) for the mission in a cooperation with the French space agency CNES. The MASCOT carries an infrared spectrometer, a magnetometer, a radiometer and a camera, and is capable of lifting off of the asteroid to reposition itself for further measurements.
Xenon is a chemical element with symbol Xe and atomic number 54. It is a colorless, dense, odorless noble gas, that occurs in the Earth's atmosphere in trace amounts.
The Small Carry-on Impactor (SCI) is a small drop-off explosively formed penetrator, consisting of a 2.5 kilogram (5.5 lb) copper projectile and a 4.5 kilogram (10 lb) shaped charge. It will be dropped off Hayabusa 2; the low gravity leaves the spacecraft enough time to maneuver to the opposite side of the asteroid.
Ion thrusters are currently used for stationkeeping on communication satellites and for main propulsion on deep space probes. Ion thrusters expel ions to create thrust and can provide higher spacecraft top speeds than any other rocket currently available.
What Is an Ion?
An ion is simply an atom or molecule that is electrically charged. Ionization is the process of electrically charging an atom or molecule by adding or removing electrons. Ions can be positive (when they lose one or more electrons) or negative (when they gain one or more electrons). A gas is considered ionized when some or all the atoms or molecules contained in it are converted into ions.
Plasma is an electrically neutral gas in which all positive and negative charges--from neutral atoms, negatively charged electrons, and positively charged ions--add up to zero.
Plasma exists everywhere in nature; it is designated as the fourth state of matter (the others are solid, liquid, and gas). It has some of the properties of a gas but is affected by electric and magnetic fields and is a good conductor of electricity.
Plasma is the building block for all types of electric propulsion, where electric and/or magnetic fields are used to push on the electrically charged ions and electrons to provide thrust. Examples of plasmas seen every day are lightning and fluorescent light bulbs.
The conventional method for ionizing the propellant atoms in an ion thruster is called electron bombardment.
The majority of NASA's research consists of electron bombardment ion thrusters. When a high-energy electron (negative charge) collides with a propellant atom (neutral charge), a second electron is released, yielding two negative electrons and one positive ion.
An alternative method of ionization called electron cyclotron resonance (ECR) is also being researched at NASA.
This method uses high-frequency radiation (usually microwaves), coupled with a high magnetic field to heat the electrons in the propellant atoms, causing them to break free of the propellant atoms, creating plasma. Ions can then be extracted from this plasma.
Modern ion thrusters are capable of propelling a spacecraft up to 90,000 meters per second (over 200,000 miles per hour), 324 000 Km/h.
To put that into perspective, the space shuttle is capable of a top speed of around 18,000 mph.