So, you have a plane on a conveyor belt...

[Mad Rocket Scientist]

3 hours ago, DAL59 said:

If the treadmill is frictionless, and has no legs, the treadmill will slam into the back of the plane.

But what if the treadmill is spherical and in a vacuum?

[razark]

1 hour ago, Mad Rocket Scientist said:

But what if the treadmill is spherical and in a vacuum?

Then it's a cow.

[magnemoe]

12 minutes ago, razark said:

Then it's a cow.

And the tread will be closed for animal cruelty. 

[p1t1o]

What if the conveyor belt is the societal conveyor belt of crime, education and social welfare?

[Gargamel]

Oddly enough.... while trying to figure out where I have heard of Spherical frictionless cows in a vacuum, I discovered they do make vacuums for cows. 

 

[magnemoe]

24 minutes ago, Gargamel said:

Oddly enough.... while trying to figure out where I have heard of Spherical frictionless cows in a vacuum, I discovered they do make vacuums for cows. 

 

Milking machines uses vacuum as in under pressure like an vacuum cleaner its also used to pump the milk. 
You can even get robotic milking machines who the cows initiates, this require non spherical cows with legs. 

[Gargamel]

20 hours ago, magnemoe said:

Milking machines uses vacuum as in under pressure like an vacuum cleaner its also used to pump the milk. 
You can even get robotic milking machines who the cows initiates, this require non spherical cows with legs. 

No, no, I understand milking.... this is literally, a cow in a vacuum.   They push the cow down a chute and into a box that sucks any flies or other pests off the cow, and then kicks the cow out. 

So I guess the cow could be on a treadmill. 

[FireKerb]

A treadmill is a treadmill, you can't say its a runway.

[peadar1987]

On 6/23/2018 at 7:26 AM, SpaceMouse said:

It's probably been said before, but all a aircraft needs is enough airflow over it's wings to get it off the ground. There are a few ultralights that can essentially take off with virtually no speed into a strong enough headwind.

I've always kinda wanted to stick a massive fan on top of a building and use it to land a conventional plane 'vertically'. I'd need a plane though, and a building, and a giant fan, and money.

None of which I have. 

This happened quite a lot on older aircraft carriers (back when planes had lower stall speeds). An aircraft carrier steaming at 25 knots into a 40 knot headwind could have a plane land pretty much vertically, level with the deck (although I've read some pretty hairy accounts of the effects of waves on this equation!)