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Japan's zero-gravity space drone sends first pictures from ISS

bbc.com

21–30 of 89 posts

Re: Japan's zero-gravity space drone sends first pictures from ISS

#21
Love the robot, but I'm uncomfortable at what I see as an implication in the article that now the astronauts should stop taking pictures and do more productive things instead.

I'm pretty sure there's values to that activity beyond having photographic registrations to show afterwards. (I'm also not convinced the little ball of cuteness is anywhere close to matching their choice of scenes yet)

Re: Japan's zero-gravity space drone sends first pictures from ISS

#22
post #19
post #9

Earlier quoted context omitted.

From a related video: the reaction wheels spin up while keeping total angular momentum at zero, then apply a rapid (magnetic) brake to transfer the momentum to the body (from the wheels). I'm assuming if you do that precisely enough (and in three dimensions), you can generate linear movement. EDIT: I'm probably very wrong about the movement. EDIT: The video: https://youtu.be/n_6p-1J551Y

The system in the (cool) video is in contact with a table. The table exerts a "normal" force on the cube, allowing a change in vertical momentum. If the system in question is the cube alone, this is an external force. This method could be used if the drone were cubic and near a wall of the space-station, by kicking off of the wall. That could get it moving, but until it hit the opposite wall, there's nothing it could…

You're right. I was thinking about that, but I really don't know. This is pretty far out of my expertise. averagewall made a good point [1].

[1] https://news.ycombinator.com/item?id=14796338

Re: Japan's zero-gravity space drone sends first pictures from ISS

#23
post #21

Love the robot, but I'm uncomfortable at what I see as an implication in the article that now the astronauts should stop taking pictures and do more productive things instead. I'm pretty sure there's values to that activity beyond having photographic registrations to show afterwards. (I'm also not convinced the little ball of cuteness is anywhere close to matching their choice of scenes yet)

They'll should still have plenty of time for taking photos. Astronauts usually work a regular 8-ish hour work day up in the ISS and have weekends etc...

2 of those working hours each day are blocked out for exercise, too, so this should be a real boon.

Re: Japan's zero-gravity space drone sends first pictures from ISS

#28
post #17
post #11

Earlier quoted context omitted.

Imagine holding up a bicycle in the air from the midpoint. Now spin both wheels in opposite directions. No movement. Now apply one brake. Now you have movement. Now do that in three dimensions with precision and you have this thing. Conservation of momentum applies when there are "no external forces", which wouldn't be the case here when you apply the brake. EDIT: Yeah, my apologies. I didn't mean to write "momentum"…

though less technical, "movement" implies "momentum", no? In the person + bike system, the brake action would result in internal forces. I don't see how this system could translate.

Not sure about the movement-momentum question.

Thinking about it, the bicycle would only rotate about the center unless it had something to react against, as was pointed out by others.

Re: Japan's zero-gravity space drone sends first pictures from ISS

#29
post #2

and no word on how it moves. even bbc is going downhill :(

Forgive the stupid question: what makes the use of reaction wheels and fans preferred over fans installed at different angles? Energy efficiency or fan reliability perhaps?

Precision and speed, reaction wheels can go from start, rotate you one degree and then stop all motion. With fans your going to end up constantly correcting because you never hit zero rotation.
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