Mars Helicopter Attached to NASA's Perseverance Rover | Hacker News Reader

Mars Helicopter Attached to NASA's Perseverance Rover

nasa.gov

92 pointscaution37 comments

I think it's interesting that it uses a Snapdragon processor running Linux and communicates over commercial Zig-Bee 900 MHz links. Tons of technical details here: https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_A...

Thanks for the link -

The Snapdragon 801 was used in 2014-era flagship smartphones like the LG G3, Nexus 5, and the Samsung Galaxy S5. (The paper is from Jan 2018.)

Publicly available vendor BSPs for msm8974 on CodeAurora topped out at kernel 3.4, but there are some independent people porting the mainline kernel to it.

It's also 28nm and not rad-hardened at all (a separate always-on FPGA is rad-hardened).

I think they should do more "cool" stuff in general. The rovers are great for science but to get the public engaged they also need to do exciting and novel stuff like flying drones on other planets. That's what gets people excited. I can't wait for the submarine under the ice of Europa

The helicopter was very controversial, because it’s a technology demo, and adds mass and risk to the overall mission without addressing its science goals. It was on the edge of being descoped for a long time.

I am glad that they did it. I am pretty big science nerd but even I am getting bored with the nth rover going to the same planet. NASA should be doing science but I think they also have the important role to push the limits of what we think is possible, inspire people and make the next generation interested in science instead of selling ads or creating CDOs. Being too risk-averse is not good for them in the long term.

It's annoying to read "The helicopter, which weighs 4 pounds (1.8 kilograms)", considering all the pedantic people who like to say weight and mass are different two things, here is something that's genuinely ambiguous because they don't bother to say if that's Mars weight or Earth weight. And it's NASA, not some careless pop sci writer!

...I did a Ctrl-F for "mass" too, and nothing.

Kilogram is a unit for mass, not weight. Weight is a force and measured in newton.

A kilogram of steel on earth is still a kilogram of steel on mars.

Ok, so?

Stating the weight of something in pounds and kg is only more confusing if you don't think either are valid units.

It wasn't my idea to measure weight that way.

You missed the point of your respondent. Weight and mass are different things, mass in kilograms usually translates through Earth's gravity into a 2.2 to 1 relationship with weight in pounds. Because 1.8 * 2.2 ~= 4 it's unambiguously referring to Earth weight, on Mars the ratio is 0.83 pounds per 1 kg. The helicopter would weigh 1.5 pounds if you took a load cell calibrated in pounds and measured it on Mars, but it would still have a mass of 1.8 kg.

There's no such thing as "Earth mass" and "Mars mass", they're the same. Calling this helicopter a 1.5 pound Mars weight helicopter seems confusing.

Pound and kilogram are same thing at different scales. The sooner US will abandon Imperial scale, the better.

Gets complicated because rocket thrust is measured in Newtons but often converted to Pounds, 1 Newton = 0.22 Pounds of thrust

Welcome to the confusing short hands of pound-force and kg-force!

It's huge part of why Newtons were used in SI instead of gram-force in CGS.

Still persists in thrust calculations, especially as metric ton-force, due to ease of calculating TWR and related.

I didn't miss the point; the point was "X is not ambiguous if you assume Y to resolve the ambiguity".

If you assume that the writer considered kg to only mean mass you can infer that they were talking about earth weight in lbs.

But I don't think one can reasonably assume that, when they wrote weight and didn't specify where, when Mars weight would be more relevant.

If someone isn't being clear and precise, then you can't resolve meaning by assuming clarity and precision. Interpretation doesn't govern reality.

This is reminding me very strongly of the perennial discussions of undefined behavior handling by compilers.

Oh, you think they took a 4 lbs Martian weight and erroneously divided by 2.2 to get kg? The 'assumption' that kilograms mean mass is a fact, not just personal preference, though I can see how a journalist might miss the distinction and make the error if they only had pounds and their editor said "all units must be reported in metric and imperial".

Regarding compilers, resolving this would be like checking that a size_t result (guaranteed to be unsigned) was greater than zero.

Sure, it's nice when writers make clear their basic assumptions if they expect their readers to have little knowledge of the subject. We're in the unique position of expecting a writer to have little knowledge, expecting them to be self-aware of that, and expecting them to recognize there's a potential distinction to be drawn between Earth weight, Mars weight, and mass.

What was bothering me was the "n miles (x meters)" - which should be either "n miles (x kilometers)" or "n miles (x feet)". I wish everyone would just complete the switch to metrics and be done with this inefficient muddle.

As always the question is with Mars rovers, does it have a microphone, that we can finally hear the winds of Mars?

Perseverance is bringing two microphones [0] with it, one of which has the secondary purpose of recording minutes of ambient sound including rover and wind noise.

[0] https://mars.nasa.gov/mars2020/spacecraft/rover/microphones/

It's great to know that this mission wasn't pushed due to COVID or anything - the next launch window is 3 years from now.

Veritasium episode covering this: https://www.youtube.com/watch?v=GhsZUZmJvaM

A video of it : https://youtu.be/oOMQOqKRWjU

Is there a particular challenge about flying a drone on Mars? Why not an already existing consumer drone?

It has to survive the trip there, be mostly autonomous, and most importantly operate in the low atmosphere and harsh environment of Mars. All things no off the shelf design will get you.

Here are some highlights: https://solarsystem.nasa.gov/news/472/10-things-mars-helicop...

Veritasium did a great vid as well -https://www.youtube.com/watch?v=GhsZUZmJvaM

The atmosphere is much, much thinner on Mars. And the difference in gravity is not as significant.

I see people have already told you that the atmosphere is thinner. But they've not really said just how much thinner.

The atmosphere on Mars is about one hundred times thinner than on Earth. That means that between "Earth atmosphere" and "vacuum", it's 99% of the way to being a vacuum.

This means that the blades need to spin really REALLY fast. Like "oh no, we'll start having transonic effects on the blades" fast. It's really tricky to build a craft where the propellers move faster than the atmosphere can "move aside". It was a really big deal to go supersonic back in 1947 or whatever, and that was with planes and did not use propellers. Transonic effects is why modern airplanes have swept wings.

But yes, gravity is like a third, so it's got that going for it.

So this is really cool, and I even found it unrealistic in the Mars TV series that they had drones, because how could that possibly be effective? Shows what I know.

I saw some videos on this drone on youtube. It can't really fly on Earth. So no, a drone off the shelf really can't fly on Mars.

It also needs to be built in an environment designed to minimize the risk of transporting any microbes from Earth.

Titan is much easier, just a little cold: https://en.wikipedia.org/wiki/Dragonfly_(spacecraft)

The X-Plane flight simulator features a realistically simulated Mars to fly on, and includes one or two fixed-wing aircraft designed for its atmosphere. No rotary-wing as far as I remember, but I suppose one could be built with the bundled Plane Maker. https://www.x-plane.com/adventures/mars.html

Because it has to work 100% reliably. (And the thinner atmosphere.)

Besides the thin atmosphere I would assume the radiation would fry a consumer drone

The thinner atmosphere also gives a cooling concern. Drone motors and electronics give off lots of heat, and the motors normally cool themselves with air blown through them with the fan blades.

Too much human intelligence is spent on space missions. Imagine what we could achieve if this intelligence was spent on useful things which affect regular people in our society.

The costs vs benefits of space exploration are not balanced at all.

Quite the other way around: Many if not most progresses in human tech history came from such endeavours.

Space travel was helped/made possible by military research (beginning with the Nazi regime), and then over the decades each r&d helped the other side to advance. Internet? Military origin. Some forms of long range comms? Space.

Or, when we want to generalize to all forms of r&d deemed "wasteful", much research in the car space was being done in the Formula 1 and later trickled down to consumer cars - the only case in which trickle down politics actually work. Many antibiotics and other medical agents came from researching rare animals in remote countries.

This argument is highly speculative and very likely misleading too. Common sense would say that the best way to hit a target is to be aiming at it. If you're aiming all over the place, it's possible that you could end up with a few bullseyes but how many shots have you wasted? How many bullseyes would have been achieved if you had been aiming right at the target?

My point still stands that it's a wasteful way to reach those targets.

By concentrating you risk getting over focused and boxed into some small branch. Having many, many directions with cooperation across them means you get significant interdisciplinary benefits, from just "someone looked at it the other way" to (quite common!) "we need some fancy material, fortunately space R&D already prototyped one that fits!"

Your premise is flawed: you assume we already know what the targets are.

Quite often in science we do not know the targets beforehand. Quite often we just happen to study/research something and out falls something else with very practical use (after minor adjustments and a little bit of out of the box thinking) we did not imagine was there.

Since the other commentor has already tried to address the benefits, I would like to point out that the costs are far from infinite: eg, NASA budget is 0.5% of total US budget (not GDP!). That is arguably a good investment, even if the only return is increased motivation to study STEM.

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