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The Last POWER1 CPU on Mars Is Dead

talospace.com

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Re: The Last POWER1 CPU on Mars Is Dead

#131

Post by daddylonglegs »

yingw787 wrote: post #5

Might be O/T, but I found it really interesting how they mention "5,352 Martian solar days". Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? Something that is a little more useful than "seconds since UNIX epoch" but something a little less terrestrial than UTC? Or is time going to be based wherever we land or travel (e.g. divide up Mars into time zones upon colonizati…

Well, the Martian solar day is a directly relevant measure for a mission that depends on charging batteries each day by solar power. I could see that being used for a lot of planning and operations.

UTC (and international atomic time - TAI) is an average measure of elapsed time that already needs adjusting for relativistic time dilation. None of the accurate clocks used for TAI are at sea level but TAI is reported as though you had all your caesium atoms ringing away at sea level [0].

Everyone else adjusts their clocks with reference to this, making allowance for propagation delays where needed. This includes things like navigation satellites (GPS, Galileo, Glonass, BeiDou etc) which have accurate clocks and significant (for their operation) relativistic dilation.

Since we already have to deal with relativity and propagation delay here on earth I suppose that, if your mission can still ping mission control here on Earth, then you can still set the system clock to UTC or TAI [1]. You will need a look up table for local sunrise times and the like but that seems quite simple compared to the mess that tzdata has to allow for back home.

[0] As I write this I realise that I don't know if TAI will be adjusted for sea level changes or not. Anyone know?

[1] Using TAI might save you from leap second problems while landing on an alien planet.

Re: The Last POWER1 CPU on Mars Is Dead

#132

Post by blattimwind »

wlesieutre wrote: post #18
dahfizz wrote: post #8

Earlier quoted context omitted.

I don't really see the problem with standardizing on 'seconds since the epoch' for any interplanetary communication and having clients convert to something more meaningful to humans. Any other "universal" time format will be just as meaningless when days and seasons are all different lengths.

At a certain point of accuracy you run into issues with this - seconds don't pass at the same rate due to relativistic effects (both speed and gravitational). An example we already deal with is GPS satellites orbiting Earth. Their clocks tick a little bit slower on account of how fast they're orbiting, and tick a bit faster on account of being further up Earth's gravity well. The gravitational effect is stronger, and…

Note that GPS compensates for relativistic effects to allow GPS receivers to act as very accurate clocks (GPS time receivers are considered stratum 0 clocks). If you didn't care about using GPS time receivers you wouldn't have to care about relativistic effects with GPS at all (because all satellites are more-or-less exposed to the same relativistic effects), because a 3D/4D fix already synchronizes the receiver to the satellite's clocks.

Relativity compensation in GPS satellites does not increase spatial accuracy.

Re: The Last POWER1 CPU on Mars Is Dead

#133

Post by benj111 »

yingw787 wrote: post #5

Might be O/T, but I found it really interesting how they mention "5,352 Martian solar days". Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? Something that is a little more useful than "seconds since UNIX epoch" but something a little less terrestrial than UTC? Or is time going to be based wherever we land or travel (e.g. divide up Mars into time zones upon colonizati…

The problem you are always going to have is that the inhabitants of each planet will want their 'days' to line up with their day/night cycles. So even without relativity, you aren't going to get a unified date system that works for everyone.

If that's the case Unix time then becomes a decent option, because it's equally human unreadable to everyone. Each planet can then have their own calendar based on that, and computers can deal with the nitty gritty

Re: The Last POWER1 CPU on Mars Is Dead

#134

Post by oso2k »

planteen wrote: post #113
justinclift wrote: post #103

Earlier quoted context omitted.

Fairly off topic ;), but any idea if SQLite is used on any of the rovers, spacecraft, etc? Mostly from idle curiosity. Was wondering a few days ago and guessing "probably yes", but no idea who to ask. So, taking the opportunity (heh) now. :)

Not a Mars spacecraft, but SQLite has definitely been used on some CubeSat missions in LEO. I know because I'm the one who did it. :-)

Was it a commercial or government CubeSat?

Re: The Last POWER1 CPU on Mars Is Dead

#135

Post by [deleted] »

omeid2 wrote: post #125
hinkley wrote: post #108

Earlier quoted context omitted.

Leap days are caused by one revolution not being a whole number of rotations. The weird thing with Mars would be that if you contact someone at 5pm local today it might not be okay to call them at the same time tomorrow, because they would clock in 37 minutes later.

> Leap days are caused by one revolution not being a whole number of rotations. Right, a whole 24 hours ;) > if you contact someone at 5pm local today it might not be okay to call them at the same time tomorrow, because they would clock in 37 minutes later. That is assuming that people on mars will have 24hr and 37 min clocks instead of 24hr. The only thing that will be different on Mars would be that the sunrise wil…

[deleted]

Re: The Last POWER1 CPU on Mars Is Dead

#136

Post by timerol »

gonehome wrote: post #54
JumpCrisscross wrote: post #9

Earlier quoted context omitted.

> Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? This fundamentally cannot exist. Any "universal" system would drift for observers on different planets. Having different times in New York and New Delhi isn't the worst right now; doing a calendar look-up for the time on Mars isn't as neat. But given we won't have real-time communication, it isn't as big of a problem e…

Somewhat comically J.C.R Licklider's first proposal for what became the internet was titled the Intergalactic Computer Network. He later said he did this because when the project is inevitably downsized it would at least cover the earth. Interplanetary internet designs and peering are interesting problems to think about though. https://en.wikipedia.org/wiki/Intergalactic_Computer_Network

A more recent protocol based on similar thinking is IPFS: https://en.wikipedia.org/wiki/InterPlanetary_File_System

Re: The Last POWER1 CPU on Mars Is Dead

#137

Post by CydeWeys »

CydeWeys wrote: post #101
hopler wrote: post #98

Earlier quoted context omitted.

Consistently defined time is less useful when events at time 12:04 cause events at time 12:02

Can you give a concrete example of how that might happen?

The only thing I can think of involves truly relativistic speeds, which just isn't going to happen for human travel anytime soon, if ever, and certainly not within the solar system.

Re: The Last POWER1 CPU on Mars Is Dead

#138

Post by planteen »

oso2k wrote: post #134
planteen wrote: post #113

Earlier quoted context omitted.

Not a Mars spacecraft, but SQLite has definitely been used on some CubeSat missions in LEO. I know because I'm the one who did it. :-)

Was it a commercial or government CubeSat?

As far as I know, it has flown on two government (civil space) missions. I'm not longer at the company so I don't know what else it has or will go into.

Re: The Last POWER1 CPU on Mars Is Dead

#139

Post by snvzz »

ajdlinux wrote: post #112
djsumdog wrote: post #111

Earlier quoted context omitted.

There are newer PPCs as well, like the Talon motherboards.

Indeed - the Talos machines are the first new PPC desktops in quite a while. The IBM POWER CPU series is far from dead, just post-Macintosh / PS3/Wii/XB360 consoles, it's not really something you see in the consumer space any more - apart from Talos, which I'm pretty excited about. (Disclosure: I work for IBM.)

Sadly too expensive for anybody to bother.

Re: The Last POWER1 CPU on Mars Is Dead

#140

Post by kharms »

jerf wrote: post #36
kharms wrote: post #10

Earlier quoted context omitted.

How would such a standard handle time dilation?

Most likely by declaring a standard reference frame and encoding standards for indicating amount of drift from it, tolerance of drift, and standards for how to update against it. A particularly forward-looking standard would encode information about the standard frame used within it, so we could switch from Sol-standard to galactic standard to cluster standard. Universal time is, of course, impossible in a relativist…

An interesting challenge might be the computational cost of conversion to the "standard" reference given a speed near c. If a single CPU tick takes a "standard year" to compute how do you do you account for all ticks in your calculation?Is it possible to get to a sub-year standard time resolution in that scenario?
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