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Mars Rover Perseverance Discussion Thread


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4 hours ago, kerbiloid said:

The last shot from Mars.

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river?version=4911097&width=1340

Any drone has an auto-return function if communication is lost.

Auto-Return, eh?

 

So... can we use that to get people back from Mars if we build one large enough?

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4 hours ago, JoeSchmuckatelli said:

Auto-Return, eh?

 

So... can we use that to get people back from Mars if we build one large enough?

You might have been joking, but would it possible to build a spacecraft capable of landing *somewhere* on Mars (purposely not choosing an exact location), identify its position on the planet, and then calculate how to, at the very least, return to the Earth-Moon system (landing back on Earth might be too tricky)? It would be a technology demonstrator, with no science objectives.

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5 minutes ago, SunlitZelkova said:

You might have been joking, but would it possible to build a spacecraft capable of landing *somewhere* on Mars (purposely not choosing an exact location), identify its position on the planet, and then calculate how to, at the very least, return to the Earth-Moon system (landing back on Earth might be too tricky)? It would be a technology demonstrator, with no science objectives.

Sure, that sounds pretty reasonable. You could use stellar navigation or something, ping MRO or whatever...You can find your exact location using a clock and a table of preset information about star positions. Then you find Earth and figure out your best return window - a feat many KSP modders have already worked on.

I think it's perfectly possible for a spacecraft to navigate all the way back home on its own - probably even simpler than what Perseverance did to set itself down in Jezero.

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7 hours ago, JoeSchmuckatelli said:

Auto-Return, eh?

Return to home, or how else is it called.

2 hours ago, cubinator said:

. You could use stellar navigation or something, ping MRO or whatever...

Locally they hope to use TriDAR.

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3 minutes ago, Gargamel said:

What's live?   The video has been removed. 

It was a NASA link to their "live from mission control" of the first copter flight.

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Seeing its dusty top before it has even flown (on the removed video title), let's hope that its solar panels will stay non-buried three days more.

Edited by kerbiloid
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33 minutes ago, kerbiloid said:

Seeing its dusty top before it has even flown (on the removed video title), let's hope that its solar panels will stay non-buried three days more.

It does have batteries

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4 hours ago, linuxgurugamer said:

It does have batteries

i think that typical procedure for storing lithium ion batteries is to store them near their nominal voltage, usually 3.7v, which is about the half way full point. storing batteries low means they could degrade below their minimum safe voltage after a year or so. this greatly reduces capacity and safety. storing them full increases the chance of fire by having more energy stored than is necessary to keep the battery healthy.  self discharge rates on lithium ion are miniscule. i usually get my stored cells out every 6-8 months and top them off just above nominal to keep them alive. batteries that drop below 2.4 can be trickle charged to save them, but i usually dispose of batteries that are below 2v. 

storing for the earth-mars transfer may have dropped them into the recoverable range, which usually requires a slow trickle charge. this would explain the delay. active battery management may have been a feature, periodically refreshing the battery. though keeping it cycling for the whole flight could reduce its life. its possible that the space environment did something to the batteries. or that the motor test stressed the cells more than they should have. several mid power (a bit below minimal flight power) test runs might be needed to break the system in for its first run. 

Edited by Nuke
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30 minutes ago, Nuke said:

i think that typical procedure for storing lithium ion batteries is to store them near their nominal voltage, usually 3.7v, which is about the half way full point. storing batteries low means they could degrade below their minimum safe voltage after a year or so. this greatly reduces capacity and safety. storing them full increases the chance of fire by having more energy stored than is necessary to keep the battery healthy.  self discharge rates on lithium ion are miniscule. i usually get my stored cells out every 6-8 months and top them off just above nominal to keep them alive. batteries that drop below 2.4 can be trickle charged to save them, but i usually dispose of batteries that are below 2v. 

storing for the earth-mars transfer may have dropped them into the recoverable range, which usually requires a slow trickle charge. this would explain the delay. active battery management may have been a feature, periodically refreshing the battery. though keeping it cycling for the whole flight could reduce its life. its possible that the space environment did something to the batteries. or that the motor test stressed the cells more than they should have. several mid power (a bit below minimal flight power) test runs might be needed to break the system in for its first run. 

You are assuming, of course,  that they are lipo batteries.

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1 hour ago, linuxgurugamer said:

You are assuming, of course,  that they are lipo batteries.

It say's they're Li-ion batteries here, and I'm not too well versed in battery chemistry, but did Nuke make some assumption that would distinguish the batteries they're talking about from the Li-ion ones they say they are?

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im pretty sure they were lithium ion or one of their derivatives. the batteries are pretty much the same as far as their safety concerns and operating voltage range go though, its just the poly cells tend to be a tradeoff between a robust packaging and weight. its this that enabled the drone boom in the first place so it makes sense they would have gone with that. 

and yes i am making a ton of assumptions, so take them with a grain of salt. most of what i know was designing battery systems for my pi tablet, none of which were spectacular. it has been infinity days since my last non-intentional battery fire. 

Edited by Nuke
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On 4/4/2021 at 11:43 PM, tater said:

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I think Percy thought it was a lawnmower, or perhaps channeling it's inner Zamboni for a bit... look at those tracks.

 

 

ingenuity.png

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Spoiler

Mock at farmer, put on field.

Not completely got, what the battery scene was about?

"When it gets broken, use its battery in the saw.
And when they get burnt due to different voltage, you can use the broken battery as an on-table pad for the office drill?"

 

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3 hours ago, tater said:

 

If this is the first controlled flight on Mars, then I take it that EDL was done via a wing and a prayer. :wink:

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