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OT How Do You Stop a Hypothetical Asteroid From Hitting Earth?NASA's On It.



 
 
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Old May 4th 19, 12:26 AM posted to alt.astronomy
herbert glazier
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Default OT How Do You Stop a Hypothetical Asteroid From Hitting Earth?NASA's On It.

On Thursday, May 2, 2019 at 6:47:09 PM UTC-7, a425couple wrote:
from
https://www.space.com/asteroid-threa...tion-idea.html

How Do You Stop a Hypothetical Asteroid From Hitting Earth?
NASA's On It.
By Meghan Bartels 15 hours ago Spaceflight

(Or read Arthur Clarke's "The Hammer of God" or lots of
other books.)

We'll have to deflect a space rock someday. It's just a question of when.

An artist's depiction of how nuclear detonations could edge a
hazardous asteroid out of Earth's path.An artist's depiction of how
nuclear detonations could edge a hazardous asteroid out of Earth's
path.(Image: © NASA)
COLLEGE PARK, Md. — Imagine humans get eight years of warning that a
large asteroid might be on a collision course with Earth. Could we do
anything about it?

Right now, scientists don't know of any space rocks on track to cause
serious damage to Earth in the foreseeable future. But if they spot one,
they'd rather have a headstart in protecting people — so they're
practicing by designing missions to a hypothetical threatening asteroid.
The exercise is part of the International Academy of Astronautics'
Planetary Defense Conference being held here this week.

For the exercise, NASA experts have designed a scenario in which
scientists in March 2019 discover an asteroid that could impact Earth in
April 2027. It's a fictional but realistic scenario, fully fleshed out
so that scientists, engineers, policymakers and emergency-management
experts can work through questions and concerns that might arise if
scientists ever do identify such a threat.

Related: How a 2017 Asteroid Flyby Is Helping NASA Defend Earth

CLOSE
And of course, a vital component of any response to such a situation is
spacecraft. Space agencies would want to put together two different
types of missions: first, reconnaissance projects that would get experts
the data they need to evaluate the situation as confidently as possible;
and second, mitigation projects that could avert a disaster if it
becomes clear such an action is necessary.

When it comes to the hypothetical scenario that planetary defense
experts are playing out this week with simulation data, decisionmakers
concluded pretty quickly that they wanted to start planning mitigation
missions right away, even if these projects might later be scrapped if
additional data clarifying the hypothetical asteroid's path concluded
that Earth would be safe.

They also scrambled to send a reconnaissance mission out to get that
data, and, as of the end of yesterday (May 1) in the conference — which
simulates December 30, 2021, in the exercise — that mission had sent
back enough data for scientists to be confident that the asteroid would
impact Earth around Denver, Colorado. (Again, no need to panic about a
fictional scenario.)

Needless to say, the world would prefer not to lose the Mile High City,
so this reconnaissance data would mean humans have a little more than
five years to execute missions to avert (hypothetical) catastrophe. It
turns out that it's very difficult to knock an asteroid onto an entirely
new trajectory; instead, the key is to slow a space rock down or speed
it up enough that it reaches the trouble point in its orbit before or
after Earth has already been there.

On the timeline the scenario is investigating, with eight years between
discovery and impact, planetary defense experts have two potential
approaches. A kinetic impactor basically acts as a stumbling block: Put
a large spacecraft in the asteroid's path; the asteroid hits it and
slows down just a little. If your impactor is large enough and catches
the asteroid with lots of time to spare, you can delay the asteroid
enough that it misses the disastrous 2027 collision with Earth.

But there's a hitch: given the details of the hypothetical scenario,
humans would need to slow down the asteroid much, much more to save
themselves than if they tried to speed it up instead. They aren't sure
of the asteroid's mass yet, but its size — on the scale of 850 by 460
feet (260 by 140 meters) — suggests humans would need three separate
stumbling blocks, and would likely want to send six in case of glitches.

Those spacecraft would need to launch around 2023 in order for Earth to
emerge unscathed (and remember, in this scenario, that's just a year and
a half away, and before scientists know the precise details of the
object). Another cause for concern: If engineers go overboard on such
devices, they could accidentally break the hypothetical asteroid into
pieces, making Earth's risk much more difficult to understand.

There's a second type of mitigation mission — detonating a nuclear
explosion above the surface of the asteroid, causing part of its surface
to vaporize and the remainder of the space rock to recoil. This approach
is also more adaptable to the many questions scientists still have about
the hypothetical asteroid, like its mass and structure. The effect of a
specific explosive device can be tuned, so to speak — detonate closer to
the asteroid and the blast is stronger, detonate farther away and the
effect is more gentle.

Fortunately, the NASA team working on the simulation exercise has an
elegant solution — if at a staggering scale — to offer. First, build and
launch (within just six months) two complex spacecraft that could fly
out to the hypothetical asteroid and orbit it for several years. These
probes would gather the information planetary defense experts need to
modulate their attack of the space rock. Then, build and launch six
missions to block the asteroid's path and slow it down, with the
orbiting spacecraft monitoring that process. As a safety precaution, the
team recommends, those two spacecraft could also be armed with nuclear
devices: If, once scientists know all the details of the hypothetical
space rock and its adjusted trajectory, they still aren't comforted,
those explosive devices could polish off the job, should a global
consensus to go nuclear arise.

Of course, no one wants to see this scenario unfold in real life. But by
running the numbers and calculating the trajectories, planetary defense
experts can be more confident that, if they do detect a real asteroid
that poses a real risk, they can put together a plan.

Humanity Will Slam a Spacecraft into an Asteroid in a Few Years to Help
Save Us All
Photos: Asteroids in Deep Space
Wow! Asteroid Ryugu's Rubbly Surface Pops in Best-Ever Photo
Email Meghan Bartels at or follow her @meghanbartels.
Follow us on Twitter @Spacedotcom and on Facebook.


A good nudge at the right time can create a miss.Bert
 




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