Spacecraft/EVA question


Ned Land

Midfield
If a spacecraft is travelling at a rapid speed between 2 objects in space, and a smaller vehicle exits the spacecraft without being connected, how does the small vehicle stay at the same speed as its ‘parent’ spacecraft?

I’m reading 2001: A Space Odyssey and a pod has exited Discovery while it travels between Jupiter and Saturn.

The pod would have to travel as fast as Discovery? But according to the book it only has enough acceleration to “hover on the moon”.
 
If a spacecraft is travelling at a rapid speed between 2 objects in space, and a smaller vehicle exits the spacecraft without being connected, how does the small vehicle stay at the same speed as its ‘parent’ spacecraft?

I’m reading 2001: A Space Odyssey and a pod has exited Discovery while it travels between Jupiter and Saturn.

The pod would have to travel as fast as Discovery? But according to the book it only has enough acceleration to “hover on the moon”.

All motion is relative. There's no friction/air resistance in space, so when the smaller vehicle exits, it velocity relative to the larger craft is minimal, whereas relative to the two objects in your OP it is "rapid" to use your phrasing.
 
Ok thank you I still think that it’s all made up.

Think how fast the surface of the Earth is spinning, and how fast the Earth travels around the sun, and how fast the whole solar system is travelling around the galaxy, and how fast the galaxy is travelling relative to other galaxies.

Now, with all that in mind, why is it that you can jump straight up in the air and land in the same spot? Why don't you go zooming off the planet at a million miles an hour as soon as your feet leave the ground?
 
Think how fast the surface of the Earth is spinning, and how fast the Earth travels around the sun, and how fast the whole solar system is travelling around the galaxy, and how fast the galaxy is travelling relative to other galaxies.

Now, with all that in mind, why is it that you can jump straight up in the air and land in the same spot? Why don't you go zooming off the planet at a million miles an hour as soon as your feet leave the ground?
Gravitational pull?
 
Gravitational pull?

No. If the gravity of the Earth prevented lateral movement, we wouldn't have long-jump in the Olympics, and planes wouldn't be able to take off.

It's because all motion is relative.

If you toss a coin while standing still, it comes straight back down.
If you toss a coin while sitting in the passenger seat of a car travelling 70mph down a motorway, the coin comes straight back down.
If you toss a coin while standing in a train carriage that's travelling at 200mph, the coin still comes straight back down.

Exactly the same thing with the EVA from a space ship that's moving.
 
No. If the gravity of the Earth prevented lateral movement, we wouldn't have long-jump in the Olympics, and planes wouldn't be able to take off.

It's because all motion is relative.

If you toss a coin while standing still, it comes straight back down.
If you toss a coin while sitting in the passenger seat of a car travelling 70mph down a motorway, the coin comes straight back down.
If you toss a coin while standing in a train carriage that's travelling at 200mph, the coin still comes straight back down.

Exactly the same thing with the EVA from a space ship that's moving.
Thanks for the examples, but the EVA pod is outside of the spacecraft. Using your examples of coins within a vehicle, my question relates to throwing a coin out of a moving train window. It wouldn’t travel alongside the train.
 
The space station for example is travelling canny rapid around the earth, when the astronauts do a space walk they still travel at the same speed as the space station
 
Think how fast the surface of the Earth is spinning, and how fast the Earth travels around the sun, and how fast the whole solar system is travelling around the galaxy, and how fast the galaxy is travelling relative to other galaxies.

Now, with all that in mind, why is it that you can jump straight up in the air and land in the same spot? Why don't you go zooming off the planet at a million miles an hour as soon as your feet leave the ground?

The surface of the Earth is travelling at about 800 mph and you are travelling at the same speed thus when you jump you land in the same place. If the Earth stopped spinning everything not firmly anchored to it would suddenly be travelling at 800 mph , including you.
Everything orbiting the Earth is travelling at 18000 mph so if you exited a spacecraft and a screw was heading towards you it would be supercooled and would pass through you at 18000 mph.
 
Thanks for the examples, but the EVA pod is outside of the spacecraft. Using your examples of coins within a vehicle, my question relates to throwing a coin out of a moving train window. It wouldn’t travel alongside the train.

The difference is that outside the train there's air to slow the coin down (air that isn't travelling at 200mph that is), whereas inside the train there isn't (as in, the air inside the train is travelling at the same speed as the train).

In space there's no air, so there's nothing to slow the EVA pod down.
 
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