Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Compasses don't work on Mars, so how do you navigate?

kottke.org

Post reply on HN
Print view View original

51–60 of 87 posts

Re: Compasses don't work on Mars, so how do you navigate?

#51

Post by creshal »

gliese1337 wrote: post #34

I am surprised that no one has yet mentioned the Gyrocompass: https://en.wikipedia.org/wiki/Gyrocompass The post mentions manually-set directional gyroscopes, but gyrocompasses are a step ahead of that; on any sufficiently-quickly-rotating planet, a gyrocompass will point you towards the geographic poles by noting the axis of precession of a gyroscope with arbitrary orientation. That's even better than a magnetic com…

How maintenance intensive are they, though? Moving parts in or near vacuum tend to be a bit iffy (e.g. lubrication), especially for multi-year (or multi-decade) robotic missions.

Re: Compasses don't work on Mars, so how do you navigate?

#54

Post by davewasthere »

creshal wrote: post #51
gliese1337 wrote: post #34

I am surprised that no one has yet mentioned the Gyrocompass: https://en.wikipedia.org/wiki/Gyrocompass The post mentions manually-set directional gyroscopes, but gyrocompasses are a step ahead of that; on any sufficiently-quickly-rotating planet, a gyrocompass will point you towards the geographic poles by noting the axis of precession of a gyroscope with arbitrary orientation. That's even better than a magnetic com…

How maintenance intensive are they, though? Moving parts in or near vacuum tend to be a bit iffy (e.g. lubrication), especially for multi-year (or multi-decade) robotic missions.

There are non-moving part designs that utilise fibre-optics or laser rings. I've only seen either the physical or laser ring gyros. Not sure about which ones they'd use in space though.

Re: Compasses don't work on Mars, so how do you navigate?

#56

Post by avian »

davewasthere wrote: post #54
creshal wrote: post #51

Earlier quoted context omitted.

How maintenance intensive are they, though? Moving parts in or near vacuum tend to be a bit iffy (e.g. lubrication), especially for multi-year (or multi-decade) robotic missions.

There are non-moving part designs that utilise fibre-optics or laser rings. I've only seen either the physical or laser ring gyros. Not sure about which ones they'd use in space though.

Grandparent is talking about gyrocompasses, not ordinary gryoscopes though. I haven't heard of a laser-ring gyrocompass. Not sure it if that is even possible.

Re: Compasses don't work on Mars, so how do you navigate?

#57

Post by rprospero »

avian wrote: post #56
davewasthere wrote: post #54

Earlier quoted context omitted.

There are non-moving part designs that utilise fibre-optics or laser rings. I've only seen either the physical or laser ring gyros. Not sure about which ones they'd use in space though.

Grandparent is talking about gyrocompasses, not ordinary gryoscopes though. I haven't heard of a laser-ring gyrocompass. Not sure it if that is even possible.

The laser gyroscopes do exist. They use lasers, plus the Sagnac effect, to measure rotations around on axis by interferometry.

https://en.wikipedia.org/wiki/Sagnac_effect

Re: Compasses don't work on Mars, so how do you navigate?

#58

Post by kefka »

gliese1337 wrote: post #34

I am surprised that no one has yet mentioned the Gyrocompass: https://en.wikipedia.org/wiki/Gyrocompass The post mentions manually-set directional gyroscopes, but gyrocompasses are a step ahead of that; on any sufficiently-quickly-rotating planet, a gyrocompass will point you towards the geographic poles by noting the axis of precession of a gyroscope with arbitrary orientation. That's even better than a magnetic com…

Maybe you would know, but are MEMS gyroscopes of accurate quality to output true north data?

Specifically referring to Invensense 9150 9dof (3 accel, 3 magnetometer, 3 gyro)

Re: Compasses don't work on Mars, so how do you navigate?

#59

Post by darkmighty »

avian wrote: post #56
davewasthere wrote: post #54

Earlier quoted context omitted.

There are non-moving part designs that utilise fibre-optics or laser rings. I've only seen either the physical or laser ring gyros. Not sure about which ones they'd use in space though.

Grandparent is talking about gyrocompasses, not ordinary gryoscopes though. I haven't heard of a laser-ring gyrocompass. Not sure it if that is even possible.

The gyrocompass orientation should, in principle, be obtainable by properly integrating gyroscope readings (and accelerometer? not sure if required).

Re: Compasses don't work on Mars, so how do you navigate?

#60

Post by kefka »

batou wrote: post #53
hacker234 wrote: post #33

Does having "no strong magnetic field" mean no Ionosphere and thus no Shortwave Radio?

Interesting thought. Never considered that you have planet specific propagation.

Well, depending on frequency you would still have some traversable effects regarding radio. You would have ground wave propagation at the minimum. unfortunately, most radio would be line of sight because of no atmosphere. Limited atmospherics would provide very restricted use on a multitude of frequencies mainly lower than 6 meter. If you wanted to communicate with the other side of the body, you would have to rely on a third entity like we do on here with the moon to bounce and receive. Aside from that option you would have little/no multi bounce
Post reply on HN