24 Nov 2021, 09:00

NASA launches spacecraft to kick an asteroid off course

  WASHINGTON, Nov 24, 2021 (BSS/AFP) - NASA is preparing a mission to
deliberately smash a spacecraft into an asteroid -- a test run should
humanity ever need to stop a giant space rock from wiping out life on Earth.

  It may sound like science fiction, but the DART (Double Asteroid
Redirection Test) is a real proof-of-concept experiment, blasting off at
10:21 pm Pacific Time Tuesday (0621 GMT Wednesday) aboard a SpaceX rocket
from Vandenberg Space Force Base in California.

  The goal is to slightly alter the trajectory of Dimorphos, a "moonlet"
around 525 feet (160 meters, or two Statues of Liberty) wide that circles a
much larger asteroid called Didymos (2,500 feet in diameter). The pair orbit
the Sun together.

  Impact should take place in the fall of 2022, when the binary asteroid
system is 6.8 million miles (11 million kilometers) from Earth, almost the
nearest point they ever get.

  "What we're trying to learn is how to deflect a threat," NASA's top
scientist Thomas Zuburchen said of the $330 million project, the first of its

  To be clear, the asteroids in question pose no threat to our planet.

  But they belong to a class of bodies known as Near-Earth Objects (NEOs),
which approach within 30 million miles.

  NASA's Planetary Defense Coordination Office is most interested in those
larger than 460 feet in size, which have the potential to level entire cities
or regions with many times the energy of average nuclear bombs.

  There are 10,000 known near-Earth asteroids 460 feet in size or greater,
but none has a significant chance to hit in the next 100 years. One major
caveat: scientists think there are still 15,000 more such objects waiting to
be discovered.

  - 15,000 mph kick -

  Planetary scientists can create miniature impacts in labs and use the
results to create sophisticated models about how to divert an asteroid -- but
models are always inferior to real world tests.

  Scientists say the Didymos-Dimorphos system is an "ideal natural
laboratory," because Earth-based telescopes can easily measure the brightness
variation of the pair and judge the time it takes the moonlet to orbit its
big brother.

  Since the current orbit period is known, the change will reveal the effect
of the impact, scheduled to occur between September 26 and October 1, 2022.

  What's more, since the asteroids' orbit never intersects our planet, they
are thought safer to study.

  The DART probe, which is a box the size of a large fridge with limousine-
sized solar panels on either side, will slam into Dimorphos at just over
15,000 miles an hour.

  Andy Rivkin, DART investigation team lead, said that the current orbital
period is 11 hours and 55 minutes, and the team expects the kick will shave
around 10 minutes off that time.

  There is some uncertainty about how much energy will be transferred by the
impact, because the moonlet's internal composition and porosity are not

  The more debris that's generated, the more push will be imparted on

  "Every time we show up at an asteroid, we find stuff we don't expect," said

  The DART spacecraft also contains sophisticated instruments for navigation
and imaging, including the Italian Space Agency's Light Italian CubeSat for
Imaging of Asteroids (LICIACube) to watch the crash and its after-effects.

  "The CubeSat is going to give us, we hope, the shot, the most spectacular
image of DART's impact and the ejecta plume coming off the asteroid. That
will be a truly historic, spectacular image," said Tom Statler, DART program

  - Nuclear blasts -

  The so-called "kinetic impactor" method isn't the only way to divert an
asteroid, but it is the only technique ready to deploy with current

  Others that have been hypothesized include flying a spacecraft close by to
impart a small gravitational force.

  Another is detonating a nuclear blast close by -- but not on the object
itself, as in the films Armageddon and Deep Impact -- which would probably
create many more perilous objects.

  Scientists estimate 460-foot asteroids strike once every 20,000 years.

  Asteroids that are six miles or wider -- such as the one that struck 66
million years ago and led to the extinction of most life on Earth, including
the dinosaurs -- occur around every 100-200 million years.


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