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Beyond Our Worlds
In 1957, man put a satellite into Earth's orbit. In 1969, Neil Armstrong and Buzz Aldrin walked on the Moon. Over the last four decades, we've studied almost all of our Solar System's planets with probes.

Now, the next big step: Mankind prepares to journey beyond our solar system.

NASA's Interstellar Probe will be the first mission designed to travel into the deep black space known as the interstellar medium, over 18 billion miles from home.

Artist conception of a solar sail in flight. Just as Columbus guided his ships using strong ocean winds, Interstellar Probe may hurtle into the unknown under the power of a sail.

An artist's depiction of a spacecraft under the power of solar sail. NASA is exploring the use of such alternatives to traditional rocket propulsion for cleaner, more efficient methods of reaching deep space.

Solar sailing is a new propulsion technology being examined for longer distance space exploration. Laboratories on Earth have developed and tested solar sail demonstrations, but the technology has never propelled a spacecraft and remains highly experimental. The basic concept involves using the light energy of the Sun to slowly accelerate the sail to tremendous speeds; in the case of Interstellar Probe, up to 41 miles a second. Shortly after passing through the Asteroid Belt, Interstellar Probe would discard its sail and coast past the orbits of the outer planets.

Another possible method of propulsion would involve a nuclear electric engine developed under Project Prometheus, NASA's program to design more powerful propulsion technologies for future exploration missions. Heat from an onboard nuclear reaction would be converted into electrical energy and propel the spacecraft at a higher acceleration than what is predicted possible from current solar sail technologies. Both solar sail and nuclear electric propulsion systems are being seriously considered for the Interstellar Probe mission, which is designed take about 15 years to reach interstellar space.

Far past Pluto, around seven billion miles from the Sun, Interstellar Probe will near the termination shock, the area where the solar wind dies down greatly as it reaches interstellar space. The actual distance of the termination shock is unknown, and researchers hope to learn a great deal about its location as Interstellar Probe passes through.

A graphic representing the boundaries of our Solar System. Several billion miles later, Interstellar Probe will reach the heliopause, where the solar wind ends and the rest of the universe begins. It's here that the probe will begin its main work: studying interstellar space.

The distance to the termination shock and heliopause are unknown because of the limited exploration of this outer region. Interstellar Probe will provide specific data about this area and give researchers a better understanding of where these solar boundaries are.

Things we can actually see, such as stars, planets and comets, only make up a small percentage of our universe. The rest is made of dark matter and energy that scientists know very little about. Direct study of this material by Interstellar Probe will provide the first real look at what our universe is made of.

A launch date for the probe has not yet been set, as key technologies for the mission are still under development. However, scientists involved in the project from research institutions around the world are hopeful that Interstellar Probe will soon be headed for the stars.
NASA's John F. Kennedy Space Center and Jet Propulsion Laboratory