Originally posted by isyeye
If you have ever seen a video of whale harpooning and the whale dragging the boat around the ocean like it's not even there.............you would think this isn't the greatest idea.

I would think there would be a high probability of the harpoon getting caught on the comet and dragging the spacecraft around space like a whale can a boat.

edit on 14-12-2011 by isyeye because: (no reason given)

You thought that, i thought that - my daughter looked at me like..wtf. so why are NASA thinking harpooning an object that could be traveling over 20,000mph over 2km wide,weighs over so many tones, from a space ship thats about 30f long and weighs as much as a stone on the object their harpooning, would be a good idea?

Like you said, its like harpooning the whale from Pinocchio whilst sat in a dingy made out of a4 paper

They have that budget, and come up with ideas like this. .

Originally posted by isyeye
They are using it as an anchor....slight difference in use.

Like I said, the difference is that it won't use the harpoon to collect any samples. The proposal is for a mission that would use a harpoon as an anchor anyway.

There are potentials in the technology, but it would definately need safety features to release the craft from the comet in an emergency.

Devising a mechanism to release or cut the cable would be far easier than the engineering of actually retreiving a sample with it. Besides, unmanned missions naturally have a much higher risk tolerance.

These comets and asteroids rotate, do they not? How does NASA plan for this? It's fine to have the probe and the asteroid at the same speed but if the comet rotates too quickly it won't be good?

Originally posted by ngchunter
They menion later on how the ESA Rosetta probe is actually already going to grapple itself to comet 67P/Churyumov-Gerasimenko in 2014, but the difference is that it won't use the harpoon to collect any samples.

Aye, there's the rub, matey!

How can one ensure the sample collecting harpoon doesn't accidentally become a grappling harpoon instead? The OP article points out some of the variables:

"We're not sure what we'll encounter on the comet - the surface could be soft and fluffy, mostly made up of dust, or it could be ice mixed with pebbles, or even solid rock.

"Most likely, there will be areas with different compositions, so we need to design a harpoon that's capable of penetrating a reasonable range of materials."

It sounds like they haven't finalized a design yet so I imagine that's one of the criteria for their design, is how to ensure it doesn't become a grappling hook instead of a sample collector. If they launch it into a soft and fluffy material, collecting the sample should be easy.

But launching into solid rock with a higher charge and making sure it won't become a grappling harpoon may be easier said than done.

I found it interesting the lab is using a launcher that looks like quite ancient but reliable technology, the bow shape of the ancient and arrow. But it's not clear from the article if the launcher they plan to use on the mission will look like that or more like the harpoon launcher on a whaling boat.

Originally posted by Arbitrageur
But launching into solid rock with a higher charge and making sure it won't become a grappling harpoon may be easier said than done.

All you need is a mechanism for releasing the grapple at the spacecraft end of things in case it gets stuck.

Originally posted by star in a jar
These comets and asteroids rotate, do they not? How does NASA plan for this? It's fine to have the probe and the asteroid at the same speed but if the comet rotates too quickly it won't be good?

They would naturally select a comet with a rotation period that is managable, which shouldn't be too hard. Tempel 1, for instance, has a rotational period of 40.7 hours. It might be best to go for a comet whose rotational period puts a stationary orbit only a mile or so above the surface. Tempel 1's rotation is so slow that a stationary orbit would be about 4 miles above the surface.

Originally posted by ngchunter

Originally posted by Arbitrageur
But launching into solid rock with a higher charge and making sure it won't become a grappling harpoon may be easier said than done.

All you need is a mechanism for releasing the grapple at the spacecraft end of things in case it gets stuck.

How do you retrieve the sample after disconnecting the cable?

Originally posted by Arbitrageur

Originally posted by ngchunter

Originally posted by Arbitrageur
But launching into solid rock with a higher charge and making sure it won't become a grappling harpoon may be easier said than done.

All you need is a mechanism for releasing the grapple at the spacecraft end of things in case it gets stuck.

How do you retrieve the sample after disconnecting the cable?

If it had to come to that you'd have to sacrifice that particular sample. Hopefully you'd have already retrieved at least one sample with another harpoon, or have another one handy to make a new attempt at a new location on the comet.

---

---