asteroid 2004 MN4

[Harmon Everett]

At the NSS meeting in May, Rusty Schweikert made the case that asteroid
2004 MN4 could hit the earth in 2036 or 2048, due to perturbations
caused by its close encounter with the earth in April 2029. We won't
know until 2029 whether that is more likely to happen and Rusty was
promoting the idea that we should send a mission to asteroid 2004 MN4
sometime in the next couple of years to attempt to gently nudge it away
from its current orbit so that it would never come close to the earth
again. If we wait until 2029 to find out conclusively, it may be too
late to accomplish anything.
The ideas advanced for trying to modify its orbit with a mission sooner
rather than later included the usual suspects - solar sail, ion drive
engine anchored to the asteroid, or chemical or nuclear rocket of some
sort. The theory being that smaller thrust over a longer period of
time would give us a better chance of modifying its orbit sooner.
If such a mission was attempted, how difficult would it be to change
the direction of orbit so that it impacts either Mars or the moon? It
would help us determine lots about the composition of whatever it hit,
and might succeed in heating up the Martian environment and releasing
liquid water in the immediate environment, wouldn't it?
On the other hand, wouldn't the most appropriate place to try to modify
its orbit be at its closest approach in 2029? And if so, how hard
would it be to change its orbit at that point so that it hits either
the moon or Mars?
Harmon

[Ian Stirling]

Harmon Everett > wrote:
> At the NSS meeting in May, Rusty Schweikert made the case that asteroid
> 2004 MN4 could hit the earth in 2036 or 2048, due to perturbations
> caused by its close encounter with the earth in April 2029. We won't
> know until 2029 whether that is more likely to happen and Rusty was
> promoting the idea that we should send a mission to asteroid 2004 MN4

Just brimming over with wrongness.
Further observations (or was it going through archives for old pics)
revealed that it was not going to hit earth.
<snip>
> The ideas advanced for trying to modify its orbit with a mission sooner
> rather than later included the usual suspects - solar sail, ion drive
> engine anchored to the asteroid, or chemical or nuclear rocket of some
> sort. The theory being that smaller thrust over a longer period of
> time would give us a better chance of modifying its orbit sooner.
> If such a mission was attempted, how difficult would it be to change
> the direction of orbit so that it impacts either Mars or the moon? It
> would help us determine lots about the composition of whatever it hit,
> and might succeed in heating up the Martian environment and releasing
> liquid water in the immediate environment, wouldn't it?

Essentially impossible.
To make something miss earth, you generally need to change its speed
by something like 10000Km/time to impact.
10000Km/30 years = 1000Km/3 years = 1Mm/100Ms = 1cm/s.

On the other hand, to make substantial changes in the orbit so that it
impacts a specific body (other than one it's about to miss) within
a few decades tends to mean speed changes of at least a few hundred
thousand times more than this.

If something is dead centered on the earth, and you want it to hit
the moon, then you need to push it some hundred times harder than just
to miss earth.

> On the other hand, wouldn't the most appropriate place to try to modify
> its orbit be at its closest approach in 2029? And if so, how hard

Yes, in theory.
In practice, probably not, as you can't get sufficient thrust in the
5 minutes or so it's close enough to earth to make any difference.
(AIUI, it's going to miss earth by quite a way, so no.)

> would it be to change its orbit at that point so that it hits either
> the moon or Mars?

[John Schilling]

In article . com>, Harmon
Everett says...
>
>At the NSS meeting in May, Rusty Schweikert made the case that asteroid
>2004 MN4 could hit the earth in 2036 or 2048, due to perturbations
>caused by its close encounter with the earth in April 2029. We won't
>know until 2029 whether that is more likely to happen and Rusty was
>promoting the idea that we should send a mission to asteroid 2004 MN4
>sometime in the next couple of years to attempt to gently nudge it away
>from its current orbit so that it would never come close to the earth
>again. If we wait until 2029 to find out conclusively, it may be too
>late to accomplish anything.

The claim that 2029 is "too late to do anything" about a potential 2036
impact by a 400-meter rock, is absurd. Too late to do *some* things,
such as the ones that involve a great deal of space exploration and
technology and infrastructure development, yes, but not too late to
do the little things like just preventing 2004 MN4 from impacting the
Earth.

Add to that the extremely low probability of a 2036 or 2048 impact, and
the case pretty much falls apart. I sympatize with people who want to
explore and develop space and are looking for any excuse to do so, but
excuses like this just destroy the credibility of the people involved.
And the asteroid-impact community doesn't have enough credibility as is.
No fault of theirs, for the most part, but they can't afford to lose any
with nonsense like this.


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