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

bbc.com

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

#41

Post by abecedarius »

bostonpete wrote: post #35
jamesvandyne wrote: post #23

Earlier quoted context omitted.

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.

They work 8 hours a day including exercise? That seems bizarre to me. I know we don't want them burning out, etc., but if we're sending astronauts up there at great expense I'd think we'd want to ask them to put in a little more than 8 hour days. 16 hours a day plus weekends seems like a ridiculous amount of free time given that there's no commuting, family time (other than calls), yard work, social engagements, etc.

Skylab astronauts literally went on strike at one point. NASA must've learned from that.

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

#42

Post by venning »

eeZah7Ux wrote: post #18
gcb0 wrote: 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?

It may also minimize the impact all of that moving air has on everything else in the station. Without gravity, fans blowing your things around could get annoying.

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

#45

Post by wubbfindel »

eeZah7Ux wrote: post #18
gcb0 wrote: 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?

Being able to operate with no atmosphere (e.g. outside of the ISS) would be an advantage I suppose.

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

#46

Post by lawless123 »

venning wrote: post #9
TeMPOraL wrote: post #4

Earlier quoted context omitted.

It seems to be rotating via reaction wheels (via this[0]). I haven't yet figured out how it translates, though. EDIT: if you have gravity available, the video on that site illustrates a clever way to use those reaction wheels to move around by tumbling. EDIT2: "for maneuvering around in space there are twelve electric micro-fans or μFans"[1]. The SE thread has a screenshot of a video which shows the placement of thos…

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

>I'm assuming if you do that precisely enough (and in three dimensions), you can generate linear movement.

You can rotate it. You wouldn't be able push it around that way though.. if you manged that it would be a reactionless drive..

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

#47

Post by dysfunction »

DougWebb wrote: post #32
TeMPOraL wrote: post #4

Earlier quoted context omitted.

It seems to be rotating via reaction wheels (via this[0]). I haven't yet figured out how it translates, though. EDIT: if you have gravity available, the video on that site illustrates a clever way to use those reaction wheels to move around by tumbling. EDIT2: "for maneuvering around in space there are twelve electric micro-fans or μFans"[1]. The SE thread has a screenshot of a video which shows the placement of thos…

The use of fans is disappointing; that means it can't go outside. My first thought when seeing it is that it'd be great for doing external inspections, and could even have its own private little airlock to get in and out. Maybe they could make a version with ionic thrusters, that stays outside all of the time. It could have a 'nest' where it parks and refuels when not in use.

Ion thrusters have tiny acceleration, which is why they're best on deep space missions (slow and steady wins the race). I wouldn't think they'd be practical for this type of thing, which you'd want to go one or a few kilometers per hour over distances of tens of meters.

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

#48

Post by eeZah7Ux »

wubbfindel wrote: post #45
eeZah7Ux wrote: post #18

Earlier quoted context omitted.

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?

Being able to operate with no atmosphere (e.g. outside of the ISS) would be an advantage I suppose.

Yet, the translation movements are done using fans. Perhaps it's a prototype and future version will operate outside.

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

#49

Post by eeZah7Ux »

Retric wrote: post #29
eeZah7Ux wrote: post #18

Earlier quoted context omitted.

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.

The robot is exposed to the station airflow so it has to adjust constantly anyways.

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

#50

Post by e12e »

lawless123 wrote: post #46
venning wrote: 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

>I'm assuming if you do that precisely enough (and in three dimensions), you can generate linear movement. You can rotate it. You wouldn't be able push it around that way though.. if you manged that it would be a reactionless drive..

What if the wheels aren't centered? You could probably not get linear movement - but couldn't you rotate around a point other than the center?

..a...b..

Rotate ~180 degrees around a, then b?

[ed: from other comments I see I may be too used to thinking in a gravity constrained environment..?]

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