

Manhole cover thought to be propelled into space - prawn
http://en.wikipedia.org/wiki/Manhole_cover#Propelled_into_space

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randywaterhouse
One would think at a speed that great (on the order of escape velocity, ~11
km/s) there'd be some serious deformation of the plate due to the frictional
heat from the air on the plate.

Another piece of space junk? A lost relic to be found in Andromeda by friendly
aliens? Only time will tell. Or maybe it basically disintegrated/melted off.
But let's hope for a cooler story: it ends up beating Voyager.

~~~
ars
> there'd be some serious deformation of the plate due to the frictional heat
> from the air on the plate.

How could it deform? For it to deform the force on one part has to be
different from the force on a different part. But the entire thing was
accelerated, and the air resistance is applied to the whole thing at once.

Perhaps there are some edge effects? Not sure.

~~~
PeterWhittaker
Forces would be different all over the surface. Assume for a moment that it
launches straight up and does not translate, that is, remains "flat",
perfectly parallel with the plane of its launch point.

There would be reduced force on the bottom and considerable force on the top,
just from air pressure. Hold your hand out the window at 100km/h to learn what
I mean: The forward side of your hand faces increased air pressure, the
backward side has reduced air pressure.

So far, so good. Now add the vortices curling around the edges of this flat
object - there will be force differentials.

Now add the vortices on the forward surface: Unless this object is optically
flat, it will have sufficient surface features to create all manner of weird
fluid dynamics, if traveling at the suggested speed.

Will it deform? Hmm, good question. First thing that will happen is wicked
random translation (pitch and roll) due to the differences in force described
above.

If it doesn't make orbit, it might deform under heat stress on the way down.
The way up it would probably travel like a knuckleball, but on the way down it
might start to stabilize.

I'm not what the odds are, but my guess is the two most probable descent
motions are, one, knife edge descent, in which case the leading edge heats up,
and it starts to soften and deform, and two, spin about a lateral axis
parallel to the earth. In this latter case, I don't know if there would be
enough heat on the two "leading edges" to cause deformation (think of it
coming out of clock, spinning clockwise: as each edge passes noon, it hits
"harder air" as it passes down to 6).

If it continues in knuckleball descent, I should think heat buildup would be
evenly dispersed.

Deformation would occur if sufficient heat builds up to soften the metal.

Note: if the object isn't metal, or is mixed metal and other material, it's
likely that it would break apart due to either or both of uneven heat
distribution and uneven resistance to force differences. Or combust.

Objects behave weirdly when traveling that fast in dense fluids.

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PeterWhittaker
I've been musing about this since posting a comment yesterday and I'm leaning
to a call of "No, not really", based on the "blur" in the image.

If this object was launched at escape velocity, it was doing at least 11km/s.
If the camera had a shutter speed of 1/500 of a second, the object would have
traveled at least ~22m during exposure. We don't know the ISO of the film, but
something covering that much distance leaving a blur? Would it even leave a
smudge? And with imperfect lighting, no less.

The slower the shutter speed, the less likely there is to be an image. Would a
camera expert care to comment?

If you follow the links in the original article, you find more information at
[1], [2], and [3]. It seems dubious....

[1]
[http://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_o...](http://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_of_steel_plate_cap)

[2]
[http://nuclearweaponarchive.org/Usa/Tests/Plumbob.html#Pasca...](http://nuclearweaponarchive.org/Usa/Tests/Plumbob.html#PascalB)

[3]
[http://nuclearweaponarchive.org/Usa/Tests/Brownlee.html](http://nuclearweaponarchive.org/Usa/Tests/Brownlee.html)

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ck2
A million years from now, the only thing left of earth, floating through
space, discovered by an alien race...

------
McDermot
I think MythBusters might have done something on this? Would be interesting to
see how the aerodynamics of the cover impacted what sort of force was
necessary to get it to escape velocity.

~~~
jared314
They did try one myth involving a methane sewer gas explosion.

[http://dsc.discovery.com/tv-
shows/mythbusters/videos/manhole...](http://dsc.discovery.com/tv-
shows/mythbusters/videos/manhole-missiles.htm)

