Meme Thread... no politics

NickD said:

Some of you rocket scientist types are going to have to explain this to me, it it is, in fact, the truth.  Gravity...  Does it somehow take more horsepower to launch towards Venus than Mars?

In reply to Streetwiseguy :

I'm not rocket scientist, but I'd think it's due to orbital mechanics.

There isn't zero gravity when you are orbiting the Earth.  You are going so fast that the ground is rolling away from you as fast as you are falling towards it.  (This is easy to picture if you think about how far a bullet drops when it is fired.... Now make the bullet so fast that the curvature of the Earth matches its drop rate)

To get OUT of orbit, and fall back down to Earth, you have to slow down.  Current spacecraft slow down just enough to get into the atmosphere, then get the rest by aerobraking. 

Now.... the Earth is orbiting the Sun.  It's going really, REALLY fast.  If you launched something off of Earth, and you want to go down to the Sun, you would have to "stop" it from Earth's speed, aka speed it up to the same speed as the Earth is going, relative to the Earth.  Which is really, really fast.

Going outwards is relatively simple: just go faster than Earth.

In reply to Pete. (l33t FS) :

Yep. Want to make that tight apex in autocross? Better slow down to the appropriate speed. Want to wind up in the weeds? Keep your speed, or increase it just a bit...

Spotted on my walk this morning.

Edit: got the meme thread and the hotlink thread mixed up.

In reply to 914Driver :

that's beautiful on all the levels

In reply to Pete. (l33t FS) :

I'm good with your explanation, and I agree with it all.  I'm just having trouble with the math.  If I want to break Earths orbit, I have to accelerate enough to stop falling towards the Earth.  That, I understand.  My problem is why I can't just leave orbit aimed in a different direction.  Most of the gravity I have to deal with is Earths, so if I break free headed towards the sun instead of towards Pluto, I should just go that way.  Once I'm headed in that general direction, the suns gravity should pull me in, or into orbit.

Unless I have to slow down to fall towards the sun, because I'm still orbiting the sun.  Ahh.  It's the deceleration that takes the fuel.  I still think I should be able to do a Star Trek time travel deal, and just hit it instead of slingshotting around.

Didn't take orbital mechanics in school.

In reply to 914Driver :

Personally, I'd rather have the carrots and ranch dip.  Those donuts are way too sweet and lacking actual flavor for me.