Mars Helicopter Ingenuity test flight altitude graph | Hacker News Reader

Mars Helicopter Ingenuity test flight altitude graph

imgur.com

79 pointswalrus0130 comments

Discussion of the livestream, including links to livestream and the video itself: https://news.ycombinator.com/item?id=26860842

(Maybe these threads should be merged?)

I was watching the NASA live stream, and it was surreal how all they were looking at was a Github repository webpage (presumably on their own GH instance) being refreshed, and text output of some scripts, as the data was rolling in, processed and interpreted. For any computer geek it was very cool, too.

Very different to similar events near Earth, where everything is observed in real time, and there is a lot of cameras pointed at whatever is happening from all angles. :)

Anyway, congrats to the NASA team, and I'm looking forward to Ingenuity's further trips.

To me it looked kind of like they were using the GitHub in a browser page to cover up a CLI script or automation tool that they don't want to show to the whole world... Resolution of the stream wasn't quite high enough to be certain.

They were refreshing the page, and I saw a new line appear every now and then, and later also (I think) a graph too. So I am assuming that it was a repo where their various tools outputted processed results of the incoming data.

Good to know that serious scientists have also been seen to click the refresh button on a browser page, like a lab mouse hitting the button for a food pellet dispenser... Have done it myself in the past, at critical moments with a 1Hz precision snmpget of data from some network monitoring equipment.

Is it so weird, though? Isn't this the kind of workflow that lies behind most serious work as long as the end product isn't supposed to be shipped off to some third party that isn't expected to have internal knowledge?

Of course. :) I did not mean the "surreal" adjective in any negative way, it's just that from all NASA or SpaceX event streams in past several years, we're all used to seeing something more tangible, like camera views, and almost zero delay, since they're usually close enough for that.

Here, all there was to see was the part that they usually do not show at all.

I think they mentioned in the Livestream that telemetry was coming in at 1Hz, presumably precision steps for each data point.

Yep. My guess is that allows them to confirm the flight plan worked and the vehicle was safe at the end, so that they could time box the report in the hour. Presumably the higher resolution data, prettier video (and maybe audio?? ) is flowing through the pipeline as we speak.

My first thought was that they are using an Enterprise Github instance for processing the data. Not much different from a CI pipeline - you get a bunch of sources (in this case, raw data from the helicopter and the rover, packaged and presumably compressed for fast and reliable transfer over the DSN), and you need to take it apart, analyze it, generate various reports and graphs and whatnot... and it looked like the dude who was reporting on the data processing progress was basically reading out the completed jobs from the pipeline progression.

Photo from Ingenuity (looking down at the shadow): https://twitter.com/NASAJPL/status/1384101674650722310

The live-stream also included a short video from the rover. I expect that will be posted any minute now.

Indeed, mentioned at https://news.ycombinator.com/item?id=26861308 and https://news.ycombinator.com/item?id=26861334

That is some fast shutter speed. I was under the impression that these little rotors would be rotoring mighty fast.

It has been a long time since I studied this but I recall something about black and white CCDs having shorter shutter/exposure times required, for a given luminance and aperture... The downward facing cam may also be global shutter and not rolling shutter?

2400 rpm, or about the same speed as the propeller of a prop airplane. A shutter speed of around 1/4000s should be enough to stop the motion quite effectively. The shadow's directly underneath so it seems to be local noon and there should be plenty of light (I guess the "sunny 16" rule of thumb[1] on Mars is more like "sunny 13" or "sunny 11" though :D)

However, I'm curious about the lack of any rolling shutter effect[2]; I wonder if the camera has a proper mechanical shutter rather than an electronic one, or even a global shutter?

[1] https://en.wikipedia.org/wiki/Sunny_16_rule

[2] https://en.wikipedia.org/wiki/Rolling_shutter

Given what was used for a bit of ballast [0] this also means that the wright flyer is the only craft to have parts under powered flight more than 50 million kilometers apart. I feel that means it qualifies for some kind of range record for the foreseeable future. First powered flight vehicle, also paradoxically farthest traveled. Just don't make 'em like they used to.

[0]https://www.reuters.com/lifestyle/science/mars-helicopter-fl...

I keep asking myself the question. How much energy is needed to lift the helicopter? And how is this compared to earth? I know density is 0.1% on mars compared to earth. But air resistance on the blades is also lower on mars. It Requires faster spinning and bigger blades. Curious to know what the energy use is there.

> I know density is 0.1% on mars compared to earth

Actually, about 1%.

Also the helicopter weighs less, when they tested it in a big vacuum chamber they had a tethered line pulling it upwards to compensate for gravity.

I don't have a concrete answer, but the X-Plane flight simulator also simulates the Mars environment (see [1]) and aircraft aerodynamics are also properly simulated, so it should be possible to build a "physically correct" Mars helicopter and find out.

(and of course somebody already seems to have done it [2]).

[1] https://www.x-plane.com/adventures/mars.html

[2] https://forums.x-plane.org/index.php?/files/file/66264-mars-...

1%, but also there's far less gravity too.

I believe they have mentioned in previous interviews that it has a 6S 18650 lithium ion battery pack (Sony cells), and that instantaneous hover wattage is expected to be around 220W. Since the batteries are also used to keep it warm a large portion of total Wh capacity are reserved for heating, each flight can only be brief before sitting and charging from the pv cells for a day or two.

It's designed to consume about 10Wh for 90s flight. I imagine the actual numbers are one thing that the team will be very interested to look at.

So how high did it actually fly? I think they said 3 metres on the webcast, and it looked something like that on the video. But the altimeter graph says 1m.

Edit: I can't read. Ignore me.

It does say 3m on the Y axis though.

Duh, you're correct of course. The 3 on the y-axis looked like a 1 to me on the fuzzy image.

success! Is it within expected performance parameters to get to 3 meters under 1 or 2 seconds? It is a bit difficult to read but it seems it went up there really fast :)

It was a low frame rate initial video, which had the effect of making the helicopter look like it suddenly shot up to the 3 metre point. Apparently proper decent FPS video clips will be downloaded over the next couple of days which should show a smoother (but still quite fast) ascent.

Counting pixels in that image it seems like both the ascend and descend took exactly 5 seconds each. So that's about 2.16 km/h or 1.34 mph.

Or about 60cm ascent or descent per second. For earth based quadcopter type UAS, straight up or down ascent or descent would typically be measured in m/s.

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