7 ms·

Copying earlier comment: Wikipedia seems to say the rover mission duration is 3 months, yet the previous rover traveled for a year and transmitted a bit longer

by A2017U1 8y ago

Copying earlier comment: Wikipedia seems to say the rover mission duration is 3 months, yet the previous rover traveled for a year and transmitted a bit longer. The Chinese seemed quite coy about it failing last time (as with many things) so perhaps underpromising in this case? This all preparation for China's planned permanent radio telescope on the far side which would be a huge boon for astronomers by escaping Earth's EM interference. Also out left field is the 3kg "self sustaining" biosphere of silkworms and plants with a camera inside. Interested to see how long it survives.

taneq 8y ago
> Also out left field is the 3kg "self sustaining" biosphere of silkworms and plants with a camera inside. Interested to see how long it survives. Aw man, that's how you get giant mutant moonworms.
- stcredzero 8y ago
  They should've added those to Iron Sky
- hyperpallium 8y ago
  Where's that? I couldn't fimd it in the linked article. Sounds like Elon Musk's original idea for a greenhouse on Mars, to inspire via realtime cam. Is there any indication they'll have a public cam for it?
  - taneq 8y ago
    It wasn't in TFA, but here's a source: https://www.bbc.com/news/science-environment-46724727 https://www.bbc.com/news/science-environment-46724727 > The lander carries a 3kg (6.6lb) container with potato and arabidopsis plant seeds - as well as silkworm eggs - to perform biological studies. The "lunar mini biosphere" experiment was designed by 28 Chinese universities. (Source for the silkworms, at least. I must confess that giant mutant moonworms are only conjecture... for now...)
    - A2017U1 8y ago
      Not entirely sure about all the ISS tests but most space biology experiments seem to be zero-g. We know a lot about how life survives at 1g and 0g but very little about in between, so hopefully it goes ok, quite a unique experiment.
      - jsjohnst 8y ago
        ISS isn’t 0g, it’s actually about 0.89g. Even the moon is 0.166g. And that’s without getting super pedantic by saying there’s always some gravity anywhere you are in the universe.
        scrumbledober 8y ago
        ISS is in freefall though, which simulates 0G. Yes technically gravity is almost as strong as on the surface where ISS orbits, but there is no normal force opposing gravity.
        jsjohnst 8y ago
        Actually, the ISS isn’t in “freefall” either. Further, there definitely is a normal force (inertia) opposing gravity too, otherwise without that (and the occasional thruster burns needed due to drag from the atmosphere), it wouldn’t “continually fall and then miss the ground” as it’s normally described in layman terms. There’s plenty of sources to back up what I said previously and here, but this provides a great description of why it’s wrong to say the ISS is in freefall: https://www.quora.com/Is-ISS-considered-to-be-in-gravitational-freefall https://www.quora.com/Is-ISS-considered-to-be-in-gravitation...
    - ericye16 8y ago
      Hm, doesn't this violate the prime directive (or planetary protection guidelines)?
      - djsumdog 8y ago
sowbug 8y ago
I'd interpret the stated duration as a criterion for whatever budget they came up with. Building something that'll last 90 days in a harsh environment is a lot less expensive than one that needs to last at least a year. And assuming the folks monitoring the rover aren't working for free, the budget needs to include their cost of employment for a fixed amount of time.
- trothamel 8y ago
  I'll note that the mars exploration rovers Spirit and Opportunity were meant to last 90 sols (Martian days). Spirit lasted 2,210, and (assuming it doesn't reply) Opportunity lasted 5,111. When you have everyone working on the mission trying to make sure their part isn't the one that causes the mission to end before the 90 days are up, you get a long-lived rover.
  - dingaling 8y ago
    The flip side to over-engineering is ever-ballooning budgets, fewer missions and more chance of random events curtailing the few missions that are flown. If the requirements state 90 days, design for 90 days - even if 180 days is achievable 'for free'. Otherwise there is no feedback loop to inform future requirements and 90 becomes an implicit 2000.b If JWST was designed for two years and a hard shutdown it would have flown years ago and we'd be on JWST Gen 3 by now, doing actual science.
    - avar 8y ago
      You're making the false assumption that designing something that last at least 90 days, but ends up lasting 2000 days is more expensive than something intended to last at least 90, and at most 180. Planned obsolescence of hardware operating on another planet can be hard, much harder than over-engineering it. Consider the wheels on the rover as a simple example (Curiosity has had structural issues with those). Next time they can either just say spend an extra 10 kg of payload to make the metal thicker, and be assured that it's "definitely 90, or way more" and move on to the next task. Or, they can consider them lasting beyond 180 a failure. Then they'll need tens of thousands or hundreds of thousands of hours of design and testing to ensure that various types of Martian terrain wear them out at just the right rate, and no more or no less. Easier to just say "this isn't worth micro-optimizing", eat the fixed cost of the extra payload, and move on. There's going to be tens of thousands of components on the rover that are like that, e.g. try finding a camera sturdy enough to operate on Mars but just fragile enough to reliably fall apart in 180 days. In aggregate that's why these rovers are exceeding their life span. If it's truly important that missions are extended for whatever reason that can just be decided as a matter of policy. Stop talking to the rover after 90 days, or hand it over to hobbyists.
brainwipe 8y ago
Regarding underpromising - there might be a little management of expectations but to paraphrase a friend in "the biz": facing away from the Earth means that the stuff you need to be reliable jumps up in complexity and with that complexity comes a foreshortening of life. She then babbled incoherently in a way I enjoyed but didn't understand. Love the idea of a dark side telescope!
- ngcc_hk 8y ago
  Dark side is not really not dark side as the moon is shined by the sun all rounded and hence we have eclipse (by the moon). But I guess the other side would as someone posted no em wave from earth and that help.
  - tabtab 8y ago
    So it's "radio dark", not "sun dark". (At least per human radios.)
    - mLuby 8y ago
      Silent side of the Moon?
rsynnott 8y ago
These sorts of missions are almost always underpromised (or, at least, based on very conservative estimates). See the various Mars rovers.
8bitsrule 8y ago
Not so unusual ... look at the spec'd mission times for many US planetary missions ... they are usually -much- shorter than the expectation values. (Opportunity Rover, e.g.)

taneq 8y ago

> Also out left field is the 3kg "self sustaining" biosphere of silkworms and plants with a camera inside. Interested to see how long it survives. Aw man, that's how you get giant mutant moonworms.

stcredzero 8y ago
They should've added those to Iron Sky
hyperpallium 8y ago
Where's that? I couldn't fimd it in the linked article. Sounds like Elon Musk's original idea for a greenhouse on Mars, to inspire via realtime cam. Is there any indication they'll have a public cam for it?
- taneq 8y ago
  It wasn't in TFA, but here's a source: https://www.bbc.com/news/science-environment-46724727 https://www.bbc.com/news/science-environment-46724727 > The lander carries a 3kg (6.6lb) container with potato and arabidopsis plant seeds - as well as silkworm eggs - to perform biological studies. The "lunar mini biosphere" experiment was designed by 28 Chinese universities. (Source for the silkworms, at least. I must confess that giant mutant moonworms are only conjecture... for now...)
  - A2017U1 8y ago
    Not entirely sure about all the ISS tests but most space biology experiments seem to be zero-g. We know a lot about how life survives at 1g and 0g but very little about in between, so hopefully it goes ok, quite a unique experiment.
    - jsjohnst 8y ago
      ISS isn’t 0g, it’s actually about 0.89g. Even the moon is 0.166g. And that’s without getting super pedantic by saying there’s always some gravity anywhere you are in the universe.
      - scrumbledober 8y ago
        ISS is in freefall though, which simulates 0G. Yes technically gravity is almost as strong as on the surface where ISS orbits, but there is no normal force opposing gravity.
        jsjohnst 8y ago
        Actually, the ISS isn’t in “freefall” either. Further, there definitely is a normal force (inertia) opposing gravity too, otherwise without that (and the occasional thruster burns needed due to drag from the atmosphere), it wouldn’t “continually fall and then miss the ground” as it’s normally described in layman terms. There’s plenty of sources to back up what I said previously and here, but this provides a great description of why it’s wrong to say the ISS is in freefall: https://www.quora.com/Is-ISS-considered-to-be-in-gravitational-freefall https://www.quora.com/Is-ISS-considered-to-be-in-gravitation...
  - ericye16 8y ago
    Hm, doesn't this violate the prime directive (or planetary protection guidelines)?
    - djsumdog 8y ago

sowbug 8y ago

I'd interpret the stated duration as a criterion for whatever budget they came up with. Building something that'll last 90 days in a harsh environment is a lot less expensive than one that needs to last at least a year. And assuming the folks monitoring the rover aren't working for free, the budget needs to include their cost of employment for a fixed amount of time.

trothamel 8y ago
I'll note that the mars exploration rovers Spirit and Opportunity were meant to last 90 sols (Martian days). Spirit lasted 2,210, and (assuming it doesn't reply) Opportunity lasted 5,111. When you have everyone working on the mission trying to make sure their part isn't the one that causes the mission to end before the 90 days are up, you get a long-lived rover.
- dingaling 8y ago
  The flip side to over-engineering is ever-ballooning budgets, fewer missions and more chance of random events curtailing the few missions that are flown. If the requirements state 90 days, design for 90 days - even if 180 days is achievable 'for free'. Otherwise there is no feedback loop to inform future requirements and 90 becomes an implicit 2000.b If JWST was designed for two years and a hard shutdown it would have flown years ago and we'd be on JWST Gen 3 by now, doing actual science.
  - avar 8y ago
    You're making the false assumption that designing something that last at least 90 days, but ends up lasting 2000 days is more expensive than something intended to last at least 90, and at most 180. Planned obsolescence of hardware operating on another planet can be hard, much harder than over-engineering it. Consider the wheels on the rover as a simple example (Curiosity has had structural issues with those). Next time they can either just say spend an extra 10 kg of payload to make the metal thicker, and be assured that it's "definitely 90, or way more" and move on to the next task. Or, they can consider them lasting beyond 180 a failure. Then they'll need tens of thousands or hundreds of thousands of hours of design and testing to ensure that various types of Martian terrain wear them out at just the right rate, and no more or no less. Easier to just say "this isn't worth micro-optimizing", eat the fixed cost of the extra payload, and move on. There's going to be tens of thousands of components on the rover that are like that, e.g. try finding a camera sturdy enough to operate on Mars but just fragile enough to reliably fall apart in 180 days. In aggregate that's why these rovers are exceeding their life span. If it's truly important that missions are extended for whatever reason that can just be decided as a matter of policy. Stop talking to the rover after 90 days, or hand it over to hobbyists.

brainwipe 8y ago

Regarding underpromising - there might be a little management of expectations but to paraphrase a friend in "the biz": facing away from the Earth means that the stuff you need to be reliable jumps up in complexity and with that complexity comes a foreshortening of life. She then babbled incoherently in a way I enjoyed but didn't understand. Love the idea of a dark side telescope!

ngcc_hk 8y ago
Dark side is not really not dark side as the moon is shined by the sun all rounded and hence we have eclipse (by the moon). But I guess the other side would as someone posted no em wave from earth and that help.
- tabtab 8y ago
  So it's "radio dark", not "sun dark". (At least per human radios.)
  - mLuby 8y ago
    Silent side of the Moon?

rsynnott 8y ago

These sorts of missions are almost always underpromised (or, at least, based on very conservative estimates). See the various Mars rovers.

8bitsrule 8y ago

Not so unusual ... look at the spec'd mission times for many US planetary missions ... they are usually -much- shorter than the expectation values. (Opportunity Rover, e.g.)