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Comment by anvandare | Hacker News Reader

Pretty sure SpaceX's first deliveries to Mars (orbit) will include just that. I think they could probably use Starlink satellites without much modification (most important one I can think of would be more panels to cope with the reduced solar irradiance)?

The GPS constellation has 32 satellites. A GPS satellite weighs ~2000kg. Starship should get 100-150 tons to Mars - the math checks out! (Disclosure: I got all my rocket science from sending Kerbals to their doom.)

So, MPS for Mars, LPS for Luna? Just imagine the amount and quality of rover footage we could get if each of them had (constant!) 1Gbps uplink to Earth...

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> satellites without much modification (most important one I can think of would be more panels to cope with the reduced solar irradiance)?

atomic clocks

Are those actually necessary?

Not an expert, but the whole network is on communication (with perfect understanding of the satellites locations no less), shouldn't they be able to run an ntpd like protocol to stay in sync, and just sync ground clocks to "starling consensus time" instead of "real time".

There is a pretty decent description of the problem here: https://physicscentral.com/explore/writers/will.cfm

I'm also not an expert so I don't know if you can solve it with syncing. Maybe you can. But that doesn't sound like a "just" concept to me - any solution to this is going to be complicated.

This got me interested so I brushed off my notes from grad school--GPS predecessors like the US Navy's Timation first used quartz oscillators, then graduated to atomic clocks in orbit. However, even now ground station atomic clocks issue periodic time corrections to satellites in orbit. Since we can get accurate time of flight to Mars, I imagine satellites without atomic clocks could be used, albeit with less stable pseudo-range estimates. This could be overcome by using more satellites, giving more favorable pseudo-range variances.

It's funny/amazing to me how we lived without GPS for thousands of years, but it's become so integral to our society that it's one of the first things we're setting up there before visiting.

> The first and most moral responsibility of Freeland will be establishing a decent brewery on the new planet. (Civilization: Beyond Earth - Hutama)

Sure, our ancestors (who could make their way and thrive in the wild) would probably consider me (who gets lost the moment I make a wrong right turn and depends on the local supermarket) a complete idiot, especially since I couldn't recreate any of the technology my daily life so depends on... But I've got central heating and clean tap-water, so I'm happy with the exchange.

The higher we climb the ladder of technological dependency, the more calamitous it becomes should we ever fall off. Best not to look down. (I think I'm supposed to bang rocks together to make fire, right?)

>(I think I'm supposed to bang rocks together to make fire, right?)

Won't work very well unless you have flint specifically :-) Even if you know the techniques, starting fire without any manufactured tools or manufactured tools to make the devices is really really hard.

Its possible to just spin a dry stick against another dry stick with your hands. takes < 5 minutes to get a fire going.

As someone who did this sort of things in Boy Scouts, this is not super-simple just using natural materials. Maybe you're superman but starting fires with just natural materials was actually very difficult for our ancestors for a very long time. And is difficult today.

I'd invite you to watch the show Alone, where many survival experts have had to give up in the first day or two because they opted not to bring a fire steel and don't want to freeze.

You're right that it's possible, but how long it takes, and whether or not you can do it, are dependent on skill and environment. Wrong kind of wood? Screwed. Been raining for a day? Screwed. Sometimes this can be overcome, but you have to know what you're doing, and it can still take hours to generate enough heat to dry the wood until it's possible to friction combust it. Try it sometime, just bring a lighter with you.

A fire steel is probably the simplest low-tech way to start a fire. You still need some expertise like finding a mouse nest or other flammable material even if it's been reasonably dry.

But friction methods are tough, even if you have a well-made spindle and fireboard--which of course require tools. You're not easily creating those without tools to make those tools. And, even then, it's not super easy especially in a non-optimum environment.

GPS is also “easy” to setup if you’re already coming in from space.

I wonder what the “useful minimum” for satellites would be if you wanted, say, relatively accurate positioning once every orbit or each day.

I get the humor, but if you think about it:

Almost all of the technologies that we would need for survival and productivity on Mars are recently-invented.

One of the main risks for early explorers was simply getting lost.

The problem of determining position (specifically the longitude part; latitude is relatively easy) has been one of the most pressing technical problems in human history. See https://en.wikipedia.org/wiki/Longitude_rewards .

No kingdoms offered huge prizes for the first electric light, or the first antibiotic, the first radio, or the first computer. But geolocation has always been considered a big deal, and it arguably wasn't well and truly solved until the advent of satellite navigation. It'd be surprising if it weren't being planned for the next generation of Mars orbiters.

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