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Congrats to the SpaceX team, always inspiring. The correction made in the article (5000 tons => 5000 lbs) shows the importance of having mental visualizations

Congrats to the SpaceX team, always inspiring. The correction made in the article (5000 tons => 5000 lbs) shows the importance of having mental visualizations for basic numerical concepts. 5000 lbs of cargo is about an SUV. I can imagine a rocket carrying that up. 5000 tons of cargo is... a giant Wal-mart parking lot full of SUVs (2000 of them). Stacked, they'd make a tower of metal a few miles high. (How? Figure 6 feet tall x 2000 = 12000+ feet.) Can you imagine a rocket carrying that up and dropping it off at the space station? Nope. When numbers are just symbols, mistakes like this are easy to make.

est 12y ago
> Can you imagine a rocket carrying that up and dropping it off at the space station? Nope. Yes! https://www.youtube.com/watch?v=8Ia2N4vpaEo&t=284 https://www.youtube.com/watch?v=8Ia2N4vpaEo&t=284
- grinich 12y ago
  I was hoping this thread would have a KSP link ;)
mikeash 12y ago
I tutored physics for a while in college, and I always tried to emphasize this sort of sanity check. It was always amusing when a student would crank through the calculations, make a mistake somewhere, and come up with the answer that their hypothetical frictionless roller coaster was fourteen light years tall, and not even realize that the number that came out was clearly wrong.
- asafira 12y ago
  I stress this, too, when I privately tutor. One interesting problem (albeit not directly relevant problem) that came up was "How would you determine the average radius of a hair given the number of hairs on your head?". This actually wasn't obvious to me, but my student figured it out right away! Put your hair in a pony tail, and measure the diameter of the ponytail, figure out that area, and divide by the number of hairs. Brilliant!
  - jmgao 12y ago
    Strictly speaking, you'd be off by ~10%, because circles don't tile the plane, and you'd be counting the area between the hairs.
  - theorique 12y ago
    Good answer, but how do you know the number of hairs? If you can estimate that within a factor of 2x, you're golden.
JshWright 12y ago
Another, far more picky, correction in the headline... Dragon is berthed, it does not dock (the article itself uses the correct term, but the headline is wrong).
- niels_olson 12y ago
  > Dragon is berthed, it does not dock Strictly, any man-made vessel that can maneuver independently can be docked, one only needs a larger vessel or facility that can receive it. That any man-made vessel can be docked follows from the fact that it is man-made: some sort of contraption was used to hold it during manufacture, and then it was removed. So long as I can make a vessel big enough to reproduce that environment, I can dock the smaller vessel. The need for the ability to independently maneuver comes from the legal nature of the issue. At some point, legal responsibility for the vessel transfers from the captain or pilot to the dockmaster. In conventional shipping, that point is when the bow crosses the plane of the dock's gate. When a vessel is berthed, some mechanism bridges the gap between the facility and the vessel, like ropes, or, in the case of the Dragon Cargo, a robotic arm manipulated from the station.
  - JshWright 12y ago
    That's not the definition used in space... Docking = A coupling device that actively 'grabs' the other vessel and allows passage between them. Berthing = A passive process where the vessel is maneuvered into place and bolted onto the other vessel. The advantage of berthing is that it allows for a larger opening between the two vessels (since the port doesn't need to have all the mechanics necessary to do the 'grabbing' bit).
deleted 12y ago
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est 12y ago

> Can you imagine a rocket carrying that up and dropping it off at the space station? Nope. Yes! https://www.youtube.com/watch?v=8Ia2N4vpaEo&t=284 https://www.youtube.com/watch?v=8Ia2N4vpaEo&t=284

grinich 12y ago
I was hoping this thread would have a KSP link ;)

mikeash 12y ago

I tutored physics for a while in college, and I always tried to emphasize this sort of sanity check. It was always amusing when a student would crank through the calculations, make a mistake somewhere, and come up with the answer that their hypothetical frictionless roller coaster was fourteen light years tall, and not even realize that the number that came out was clearly wrong.

asafira 12y ago
I stress this, too, when I privately tutor. One interesting problem (albeit not directly relevant problem) that came up was "How would you determine the average radius of a hair given the number of hairs on your head?". This actually wasn't obvious to me, but my student figured it out right away! Put your hair in a pony tail, and measure the diameter of the ponytail, figure out that area, and divide by the number of hairs. Brilliant!
- jmgao 12y ago
  Strictly speaking, you'd be off by ~10%, because circles don't tile the plane, and you'd be counting the area between the hairs.
- theorique 12y ago
  Good answer, but how do you know the number of hairs? If you can estimate that within a factor of 2x, you're golden.

JshWright 12y ago

Another, far more picky, correction in the headline... Dragon is berthed, it does not dock (the article itself uses the correct term, but the headline is wrong).

niels_olson 12y ago
> Dragon is berthed, it does not dock Strictly, any man-made vessel that can maneuver independently can be docked, one only needs a larger vessel or facility that can receive it. That any man-made vessel can be docked follows from the fact that it is man-made: some sort of contraption was used to hold it during manufacture, and then it was removed. So long as I can make a vessel big enough to reproduce that environment, I can dock the smaller vessel. The need for the ability to independently maneuver comes from the legal nature of the issue. At some point, legal responsibility for the vessel transfers from the captain or pilot to the dockmaster. In conventional shipping, that point is when the bow crosses the plane of the dock's gate. When a vessel is berthed, some mechanism bridges the gap between the facility and the vessel, like ropes, or, in the case of the Dragon Cargo, a robotic arm manipulated from the station.
- JshWright 12y ago
  That's not the definition used in space... Docking = A coupling device that actively 'grabs' the other vessel and allows passage between them. Berthing = A passive process where the vessel is maneuvered into place and bolted onto the other vessel. The advantage of berthing is that it allows for a larger opening between the two vessels (since the port doesn't need to have all the mechanics necessary to do the 'grabbing' bit).

deleted 12y ago

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