Astrophysicists: Does this article make sense?

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Ichinisan

Lifer
Oct 9, 2002
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http://www.engadget.com/2014/04/18/nasa-ladee-crashes-into-moon-on-purpose/

NASA just crashed a satellite into the moon on purpose

You might remember NASA's LADEE as the satellite where the administration tested a new broadband-fast laser communication system for sending data back to Earth. Now, however, the Lunar Atmosphere and Dust Environment Explorer is no more, since NASA just crashed the craft into the surface of the Moon. Unfortunately, the vehicle didn't have the power to maintain its orbit, so the bods in Florida decided to send the hardware on a one-way trip. On the upside, the satellite managed to grab some super-detailed scans of the lunar surface before burning up, and it probably looked really cool when it exploded, which probably justifies the wanton destruction of a multi-million dollar spacecraft.

This article confuses me.

It "didn't have enough power to maintain orbit?" Sounds like there was a miscalculation then. Since the moon has no atmosphere (so there's no friction), it should have been able to orbit practically forever (barring unexpected debris impacts). The only fuel needed would be for a few initial corrections to get a stable orbit...then it could go on for hundreds / thousands / millions of years (technically not "forever" because nothing is perfect and even the moon itself acquires mass gradually over time).

The other part that bothers me:
Why would it "burn up" with no atmospheric friction? It would be obliterated on impact with the surface, but it shouldn't "burn up" in any sense...right?
 

JManInPhoenix

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Sep 25, 2013
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I know jackshit about astrononomy; but I would assume the moon's gravity (much less than the Earths) was probably sufficient to pull it down over a long period of time.
 

mnewsham

Lifer
Oct 2, 2010
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Not an astrophysicist, but my dad has his PhD in astrophysics so I'm slightly more qualified than some people by proxy.

The gravity from earth and the gravity from the sun and the gravity of the moon itself would all be interacting on the satellite, though they would likely cancel each other out in some instances, however it's fairly easily corrected if you have maneuvering power, without this though it becomes difficult to keep in orbit and to avoid it potentially causing issues later once it runs completely out of power they decided to crash it into the surface. You are correct in that it wouldn't burn up though, just slam into the surface.
 

Markbnj

Elite Member <br>Moderator Emeritus
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Sep 16, 2005
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Even in space there is energy loss in a system. Satellites in earth orbit carry fuel supplies for orbital adjustments as well.
 

Brian Stirling

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Feb 7, 2010
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More likely it was out of fuel for the reaction jets needed to maintain attitude and they used the remaining booster propellant to deorbit. In the absence of an atmosphere the satellite should have been able to remain in orbit for a very long time, but without attitude control thrusters it would not be able to point properly and would therefore be useless.

So they converted a useless satellite into an impact experiment -- good for them.


Brian
 

techs

Lifer
Sep 26, 2000
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I only pretend to be an astrophysicist sometimes, but definitely it should not "burn up"
 

gorobei

Diamond Member
Jan 7, 2007
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if you read the actual nasa statement in the article source link, it becomes obvious that the engadget writer is less technically versed in astronomy than one would hope for, hence "burned up"

based on the nasa release, it seems like they sent the ladee sat thru some lower orbits during the main mission and it didnt have enough fuel to push it back out to a stable long term lunar orbit. the release also states there is a lunar atmosphere, just very minimal. however nowhere do they ever mention burn up.
 

Fritzo

Lifer
Jan 3, 2001
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Terrible article. It looks like they tried to be cute while transcribing it. The actual story indicated the vehicle didn't have enough fuel to make orbital corrections, so it was impacted on the surface. There would not have been any flames or burning due to the lack of oxygen.
 

Hayabusa Rider

Admin Emeritus & Elite Member
Jan 26, 2000
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Terrible article. It looks like they tried to be cute while transcribing it. The actual story indicated the vehicle didn't have enough fuel to make orbital corrections, so it was impacted on the surface. There would not have been any flames or burning due to the lack of oxygen.

Reminds me of a recent announcement regarding the most earth like planet found to date. It's in the constellation "Cygnu". Nope.
 
Mar 10, 2005
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re-entry heating is due to compression, not friction. and, nasa has been deliberately crashing things into the moon since the 60's.
 

Jeff7

Lifer
Jan 4, 2001
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More likely it was out of fuel for the reaction jets needed to maintain attitude and they used the remaining booster propellant to deorbit. In the absence of an atmosphere the satellite should have been able to remain in orbit for a very long time, but without attitude control thrusters it would not be able to point properly and would therefore be useless.

So they converted a useless satellite into an impact experiment -- good for them.


Brian
And kept a piece of space junk from staying in low lunar orbit, until finally crashing anyway at an unknown future date.




The Moon's not a friendly place for low, stable orbits.
And then tidal forces from Earth don't help either, though perhaps to a lesser degree. (These low-lunar orbits are low.)
So fuel is needed to keep it in orbit, and scientifically-illiterate people are needed to attempt to write articles about it.
 
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