Reasons why LCROSS is a safe mission

[MajorHarrison]

Hi everyone. I'm looking for some help explaining why the LCROSS mission is perfectly safe. If you don't know what I'm talking about you can find an article http://www.siliconvalley.com/ci_12590357" helpful (post #11). What I am basically looking for is a way to explain to a person who doesn't know that much about physics why there is nothing to worry about for this mission.
If any of this is wrong, please correct me.

PS. This is my first post here so be nice.

 

[Nabeshin]

Hello, and welcome to PF!

You are correct, there is no chance of the moon crashing into the Earth or anything like that. Without going into the details of orbital mechanics, momentum, and energy, you can just concoct some analogy (a fly running into a house, or something) to demonstrate that the moon is so much terribly more massive than a puny rocket. If analogies aren't your bag, explain that countless asteroids have bombarded the Moon's surface, many much more massive and traveling much faster than this rocket will. Mind you this happened billions of years ago, and as far as I know, the moon is still there.

Somewhat akin to the argument against the LHC creating mini black holes, because much higher energy cosmic rays have been bombarding the earth, and so if the creation of mini black holes was possible (and dangerous) we wouldn't be here right now.

 

[D H]

you can just concoct some analogy (a fly running into a house, or something)

That's a bit better than the BB versus a bowling ball analogy, but not much. LCROSS masses 1664 lb. A house fly: 12 mg, or about 1/63000 of the mass of the LCROSS. Scaling the Moon's mass by the same amount yields a better analogy: A house fly running into a *big* brick that weighs 1.3×10¹⁵ tons. That doesn't say much yet. The Empire State Building has a mass of 365,000 tons. That brick is equivalent to 3.5 billion Empire State buildings. A fly flying at 5,600 mph into a pile of 3.5 billion Empire State buildings is not going to move the pile at all.

 

[mgb_phys]

Nasa is going to crash a spacecraft into the moon!
What about the clangers ?

 

[ideasrule]

"I am on another forum (not a physics focused forum) and this article was posted. Many of the users there started saying that they think this is a dangerous mission and the moon will "crash into the earth"."

Tell them to watch the video that's embedded in the article. It explicitly says that the LCROSS is schoolbus-sized, and that schoolbus-sized objects crash into the Moon every month. To use an analogy, launching LCROSS at the Moon is like crashing a truck into the Earth. Earth will not notice at all.

 

[MajorHarrison]

Ok, thank you all for your responses. I am sure this will convince them its safe.

 

[D H]

No, it won't. It is rather difficult to win an argument against woo-woos. They are completely immune to logic and evidence.

 

[sas3]

Get your telescopes out if you are west of the Mississippi (Dam, my scope is in Upper Michigan).
The LCROSS impact plume should be visible in a 10 inch and larger scope.

Someone please take some pictures and post them here.

October 9
4:30 am PDT

http://science.nasa.gov/headlines/y2009/05oct_lcrossvg.htm?list1032821"

 

[Wallace]

There's plenty of readers of this forum 'west of the Mississppi' who won't be able to see this impact.

 

[sas3]

There's plenty of readers of this forum 'west of the Mississippi' who won't be able to see this impact.

I am a bit confused, why won't they be able to see it?
Or was that a typo.

 

[Wallace]

Because the Moon will be on the other side of the Earth at that time. I am, for instance, west of the Mississippi (I'm also east of it) but it will be broad daylight for me when this impact happens.

The world, and this forum, exists far beyond one continent!

 

[sas3]

I guess East and West have no meaning what so ever then in that sense.
I should have just said if someone is in the right place at the right time please take some pictures.

We have about 20 minutes until impact NASA TV has it live if anyone wants to watch.

 

[Glennage]

Special Feed Here also:

http://www.slooh.com/special_feed.php

 

[Wallace]

Sorry to appear pedantic, but my east-west thing may have obscured my point. Think of how usefull it would be, and how silly it would sound, to you if I posted that something could be seen if you 'are west of the Nile' or by anyone 'east of the Rhine'.

 

[Glennage]

Somebody from NASA could have told us how boring that was.

 

[Saladsamurai]

This might be a silly question, but are the images located http://www.telegraph.co.uk/science/space/6275279/Nasa-Moon-bombing-LCROSS-mission-crashes-into-Moon.html#" real?

Are these images that the 'lagging' spacecraft took?

 

[pixel01]

Anyone has a picture of the plume?

 

[George Jones]

Anyone has a picture of the plume?

I'm not sure that even NASA saw much of a plume visually. I watched with an 8" Schmidt-Cassegrain (at 8:31 am my time), and I didn't see anything.

My little girl woke me up at 5:00 am to go pee. After taking her to the bathroom and getting her back to sleep, I carried my gear down two flights of stairs and locked it in our car (parked on the street) to cool down. At 7:30, the sky was almost completely cloudy. Started to clear at about 8:00, so I went out and set everything up. Still clear at 8:31 and the Moon was high in the sky. The seeing was fairly steady, and I had a clear view of the area at my highest magnification, 254x. Saw nothing, but I'm not a great observer, and, by 8:31, the features were somewhat washed out by daylight.

 

[Equate]

NASA confirms water on the moon:

http://www.nasa.gov/mission_pages/LCROSS/main/prelim_water_results.html