[HN Gopher] NASA's helicopter survives first freezing night on Mars
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NASA's helicopter survives first freezing night on Mars
Author : imagine99
Score : 86 points
Date : 2021-04-05 20:16 UTC (2 hours ago)
(HTM) web link (edition.cnn.com)
(TXT) w3m dump (edition.cnn.com)
| BitwiseFool wrote:
| Does anyone know if Perseverance is capable of recording video? I
| know it has several cameras but I can't figure out if it can
| actually record footage of Ingenuity taking flight.
| [deleted]
| pohl wrote:
| Yes, it is
|
| https://mars.nasa.gov/mars2020/spacecraft/instruments/mastca...
| BitwiseFool wrote:
| Thank you, for some reason I had a lot of trouble with Google
| when trying to find this answer. It kept returning results
| about the video taken by the skycrane, not the rover itself.
| mlyle wrote:
| Note that most of that video is taken by the rover itself,
| watching the skycrane fly off etc.
|
| Indeed, we don't have any video from the skycrane after
| touchdown, because I believe that data was fed over an
| umbilical to the rover before being sent to the low orbit
| (I'd typed LEO, but I guess I mean "LMO") satellites and
| back to Earth.
| aeternum wrote:
| Have they posted any videos yet? Somewhat disappointing that
| so far it's only been images with really poor UI/UX via the
| NASA site. That's not how you capture the public's
| imagination.
|
| I also don't see why they are waiting so long to do the
| flight, why risk even waiting until nightfall for the
| batteries to get too cold or for dust to get into the
| electronics/mechanics?
| mlyle wrote:
| > Have they posted any videos yet?
|
| An amazing one. Most of driving along at 1MPH on a barren
| landscape is incredibly boring, but...
|
| https://youtu.be/4czjS9h4Fpg?t=10
|
| > I also don't see why they are waiting so long to do the
| flight
|
| Because there's a couple dozen steps that are each
| irrevocable involved in uncovering, unfolding, deploying,
| and then flying this thing... and that they want to make
| sure everything is perfect between each one and that comms
| still worked before cutting umbilicals, etc, because you
| can't just plug it back in.
| ghaff wrote:
| >I also don't see
|
| Maybe, just maybe, the domain experts involved know
| something you don't. Just a theory.
| BitwiseFool wrote:
| To be fair, maybe the OP was hoping they'd provide an
| explanation as to why.
| lgrebe wrote:
| AFAIK it's possible and will save to an on-rover disk. The
| current limit to seeing that footage here on earth is the
| downlink bandwidth limit. So far it's been used for more
| ,,interesting" data and still images.
| [deleted]
| londons_explore wrote:
| Making electronics work at a very high or low temperature is a
| challenge. You normally have to decide between custom-designing
| all components to work at the extreme temperature, or to figure
| out how to use off the shelf stuff, yet insulate them from the
| environmental temperature.
|
| More and more designs are choosing the latter, although notable
| exceptions are LED light bulbs (which use special components
| rated to operate for years at ~150 Celcuis)
| maxwoj wrote:
| "130 degrees Fahrenheit" - seriously? What else, pounds and feet?
| js2 wrote:
| The article is written for an American audience. We use
| Fahrenheit here. That said, -130degF is so beyond what any
| American can relate to, I agree the article should use C and
| provide the -130degF in a parenthetical. Amusingly, the article
| does just that later on:
|
| > During the first flight, the helicopter will attempt to rise
| about 10 feet (3 meters) in the air from the middle of its flat
| 33-by-33-foot (10-by-10-meter) airfield...
|
| p.s. -90degC
| narrator wrote:
| One way to relate to it is that -128.6F is the lowest
| recorded temperature ever on earth.
|
| https://en.wikipedia.org/wiki/Lowest_temperature_recorded_on.
| ..
| aksss wrote:
| I think Americans would relate to -90C even less. Many
| Americans are used to thinking about sub-zero temperatures,
| it seems less of a burden to conceptualize a really low
| temperature on the scale you're used to than to conceptualize
| a really low temperature on a completely different measuring
| system. The first question most Americans would ask is
| "What's the equiv of -90 in F?".
| Sharlin wrote:
| Incidentally, -90degC/-130degF happens to be almost exactly
| the lowest natural temperature measured on Earth
| (-89.2degC, in Antarctica in 1982).
| sleavey wrote:
| Out of curiosity, what do Americans mean when they say
| "sub-zero"? 0degC or 0degF?
| AnimalMuppet wrote:
| 0degF.
| ceejayoz wrote:
| 0degF. "Below freezing" would be below 0degC/32degF.
| js2 wrote:
| I've never lived anywhere in the U.S. that gets that
| cold, but in my experience, I don't think Americans say
| that much, but rather "below freezing" to mean below
| 0degC/32degF.
|
| I happen to easily remember that 20degC = 68degF and
| usually use that when mapping the temperatures back and
| forth which works for the usual ranges where I've had to
| do so by just adding/subtracting 5/9 on each side.
|
| I once translated literally on the run (running the
| Boston marathon) for a foreigner who asked about the
| temperature and got a Fahrenheit response.
|
| When I've been in other countries that use C, I've always
| had to translate from C back to F in my head to make
| sense of the temperature. The longest I've ever been any
| place outside the US is 10 days, and that hasn't been
| enough time for me to get a feel of what temps are in C.
| JoeAltmaier wrote:
| 0F of course. We get pretty cold here.
|
| When some youtuber is camping out in 'sub-zero' temps, I
| smile. We call it 'warm' in Iowa when it gets above
| freezing in winter.
| js2 wrote:
| I was hiking on the A.T. one time and it was just a bit
| above freezing and rainy. My group (all from Florida) was
| bundled up inside a cabin to get out of the rain. In
| wandered some other college kids in shorts and tees,
| soaking wet. They were from Minnesota. I really don't
| know how they didn't have hypothermia, but I guess you
| can acclimate to quite a range of temperatures... for a
| while.
| kshacker wrote:
| "Survives first freezing night" == Is this just sensationalism?
| Should NASA not have a good estimate of what the chances of
| survival are? Maybe it is the media, maybe it is the need to fill
| columns (like the old days) but I would probably make a list of
| milestones and track "time to first flight" or something similar.
| [deleted]
| qchris wrote:
| This is a technology demonstration of a novel robotics system
| build using many off-the-shelf parts, on a planet with night-
| time temperatures as low as -130F [1].
|
| _Ingenuity_ survived, literally, a first freezing night. That
| is an accomplishment by itself, and is hardly sensationalist.
|
| [1] As linked in the article:
| https://mars.nasa.gov/technology/helicopter/status/288/its-c...
| mseepgood wrote:
| > on a planet with night-time temperatures as low as -130F
|
| For anyone reading this: -130F is -90degC
| galacticaactual wrote:
| It is literally a milestone on a list of milestones.
|
| https://www.jpl.nasa.gov/news/press_kits/mars_2020/launch/mi...
| amelius wrote:
| I find the order of milestones a little surprising.
|
| Why didn't they test the survival of the freezing cold
| _after_ testing the rotor blades, lift-off and perhaps a
| short flight in the vicinity of the rover?
| ceejayoz wrote:
| They fully expect it to survive the night - it'll have
| survived identical conditions in pre-launch testing - and
| thus there's no need to rush through the other steps.
| thelean12 wrote:
| It's probably as simple as: they didn't have time. You have
| to move slowly and carefully on Mars. One rushed mistake
| and it's over.
| amelius wrote:
| Yes, but chances of getting useful data out of the
| helicopter are much greater if you test the thing before
| subjecting it to harsh conditions.
|
| For example: if you know that lift-off works, then that's
| a huge datapoint.
| thelean12 wrote:
| I bet they'd move faster if they could. I'm guessing for
| takeoff there's a good amount of analysis to do
| beforehand. Terrain, weather, system checks, whatever.
|
| I don't know the actual list, but it's not hard to guess
| why they couldn't do everything, including ejecting it
| from the main rover and getting the main rover out of the
| way, in the ~12-14 hours a day that they have to do
| stuff.
| jacobreg wrote:
| They don't want to fly it with the rover nearby. It needs
| to get to a safe distance before they can fly it.
| whimsicalism wrote:
| Wow, reading the first comment I would think that this was
| planned. It literally is the third thing on a list of
| "milestones."
| ortusdux wrote:
| 2/3rds of Ingenuity's stored energy goes towards keeping its
| batteries and critical components warm each night. Only 1/3rd
| is available for powered flight. It literally takes more energy
| for this helicopter to survive the night than it takes to fly
| on mars.
| arrosenberg wrote:
| That's pretty interesting. Maybe the next rover needs an
| excavator tool so we can build an underground hidey-hole for
| storing sensitive equipment at night.
| namrog84 wrote:
| I'm not sure how to really internalize this.
|
| Does it take a ton of power to heat. Or does it take very
| little power to fly?
|
| I'd assume there is a ton of effort put into passive
| insulation? Since my non intuitive gut seem like it should be
| able to better insulate heat loss. I can't help but feel like
| there is probably a ton of effort and science to insulate.
| And this is even only possible because of that work. But is
| it just a much harder problem than I probably realize?
| danaliv wrote:
| On the aerodynamic side, this aircraft has a mass of 1.8 kg
| / 4 lbs, which is an equivalent weight of 0.7 kg / 1.5 lbs
| on Mars. That is also the force required to maintain
| altitude. Imagine picking up four or five apples; that's
| what we're talking about as a minimum to stay in the air.
| For comparison, a DJI Phantom weighs 3 lbs, and a Mavic
| comes in at 2 lbs.
|
| I can't find numbers on the power system or materials so I
| can't speak to the thermal side or how much flight time
| that affords.
|
| EDIT: Apparently there's enough energy to fly for 90
| seconds (!) per sol.
| HPsquared wrote:
| Mars is very cold, things like the battery can't handle
| these temperatures. It's been thoroughly analysed, here is
| a quote from the white paper [0]:
|
| """H. Thermal System
|
| The helicopter must survive the cold of the night on Mars
| where temperatures can drop to -100 C or lower. The most
| critical component is the battery which is kept above -15 C
| through the night as it powers Kapton film heaters attached
| to the battery cells. The avionics boards in the ECM
| surround the battery and are also kept at an elevated
| temperature by virtue of their proximity to the warm
| battery assembly. Insulation around the avionics boards is
| provided by a carbon-dioxide gap of 3 cm width. Additional
| insulation can be provided by replacing the carbon-dioxide
| gas with an Aerogel formulation. The outermost fuselage
| thermal coating is from Sheldahl with Solar absorptivity a
| = 0.8 and infra-red (IR) emissivity = 0.1.
|
| In addition to thermal losses through the gas gap (or
| aerogel), additional losses occur due to conduction in the
| mast as well as through the copper wiring that penetrate
| the ECM from the mast. To minimize the latter, the wire
| gauges are selected to be of the thinnest gauges that can
| still support the current draw during operations without
| overheating. Prior to flight, under the control of the
| FPGA, the thermal system powers on heaters in the motor
| control boards that have been exposed to the ambient
| temperatures. The internal battery temperature is brought
| up to 5 C to allow hi-power energy extraction from the
| cells. During operation the ECM and battery warm up as a
| result of avionics operations and battery self-heating.
| However, the thermal inertia of the elements is such that
| for the short flights of the helicopter, there is no
| overheating."""
|
| [0] "Mars Helicopter Technology Demonstrator" https://rotor
| craft.arc.nasa.gov/Publications/files/Balaram_A...
|
| EDIT: some detail on the battery capacity from section G:
|
| "A de-rated end-of-life battery capacity of 35.75 Wh is
| available for use. Of this capacity, 10.73 Wh (30%) is kept
| as reserve, night-time survival energy usage is estimated
| at 21 Wh for typical operation in the northern latitudes in
| the spring season, and approximately 10 Wh is available for
| flight. Assuming that 20% of the power is at the peak load
| of 510 W and 80% is at a continuous load of 360 W,
| approximately 90 sec of flight is possible. These energy
| projections represent conservative worst-case end-of-
| mission battery performance at 0 C initial temperature.
| More moderate power loads will extend the flight time."
| ortusdux wrote:
| On top of what others have said, we need advancement it
| batteries that can withstand low temperatures. Lithium ion
| batteries generally need to be kept above freezing temps.
| There have been some advances in capacitors that operate
| down to -100C, but their energy density makes them a non-
| ideal option for weight limited applications.
|
| This video from Veritasium does a good job of covering the
| helicopter power system:
| https://www.youtube.com/watch?v=GhsZUZmJvaM&t=613s
| InitialLastName wrote:
| -130F/-90C is VERY cold, and this system is VERY weight-
| sensitive. Presumably adding more insulation that always
| needed to be carried was more weight than adding power
| capacity that can serve a dual-use.
|
| The power capacity metric isn't necessarily concurrent; one
| could imagine the chopper using its power to fly (which
| will generate heat as a byproduct) for a third of the
| sunlight time, and then using the rest of the day to charge
| for the night-time cold.
| p1mrx wrote:
| > one could imagine the chopper using its power to fly
| (which will generate heat as a byproduct) for a third of
| the sunlight time
|
| This is impossible; the flight duration is ~ 90 seconds.
| spuz wrote:
| No it's not - firstly, you can go to JPL's version of the story
| here and see how they lead with the same headline:
|
| https://www.jpl.nasa.gov/news/nasas-mars-helicopter-survives...
|
| But I prefer to hear it directly from the engineers involved:
|
| > "What was it like seeing that first image of Ingenuity on
| mars?"
|
| > "Oh it was a dream come true. To see the culmination of the
| entire team's hard work really pay off. Being dropped - that's
| one huge milestone, but the _massive_ one for us over the last
| few days has been realising not only did we drop, but we
| actually survived the first night. That is huge. That was one
| of the huge huge achievements that we 've been looking forward
| to and now we can look forward to the rest of the mission. But
| being able to drop under our own energy, sustain ourselves,
| keep ourselves warm through the whole night and then wake up
| and talk with Perseverance and say "yep we're here alive and
| healthy" the team couldn't be happier."
|
| https://youtu.be/PcpI8-S5ZE8?t=108
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(page generated 2021-04-05 23:00 UTC)