Comment by BelenusMordred | Hacker News Reader

Comment by BelenusMordred | Hacker News Reader

Another pic: https://imgur.com/Vct0PXV

It's an interesting design, in someways the ramp is a deceptively simple concept but I'm not sure if it's safer than the US approach.

Some other neat things are:

Solar panels, they are a specially designed to electrically repel Martian dust, in theory there should be a decent power gain from this and it will likely be used in future missions. While other rovers fortuitously found solar was self cleaning on Mars, power is still a knife-edge engineering problem for rovers.

Ground penetrating radar, can see down 100m, a lot further than anyone else has ever investigated, should yield some interesting data. Like most other missions they are very interested in prior and current water on the planet.

Coverage, they are planning a few hundred metres over 3 months, the rover itself can do 200m in a day though if needed, very unlikely that will happen but it is in a flat area of Mars. The landing zone was so huge that there'll be some tough choices about what is the most productive area to explore for planetary science.

The speed of entry, Zhurong came in at about half the speed of Perseverance, this makes life a lot easier. It takes a lot longer to bleed off that velocity in orbit but seems like other nations attempting a landing will follow this path.

I'd be interested to know about their uplink, remember hearing they might be using an ESA orbiter but not sure about that, the orbiter they have is not that great for a connection due to it's altitude.

Technical info is surprisingly hard to find, even in publications like nature or science mags normally focused more on the details.

> It's an interesting design, in som eways the ramp is a deceptively simple concept but I'm not sure if it's safer than the US approach.

It's the 'standard' way as far as I know (see Path Finder/Sojourner for instance).

The 'sky crane' system used by the US is fairly new and, I guess, much more complex to pull off and more expensive. I think it was developed partly because the payload had become too big/heavy for the previous airbag system.

The rocket backpack seems like it would allow you to land more weight than the lander an ramp method because you don't have a much superfluous structure on the rocket lander section of the craft. Zhurong is only about as big as Spirit and Opportunity that the US landed back in 2003 using big airbags, larger rovers can't do that so you get into more complex things like the sky crane.

The main problem with Zhurong is they brought their orbiter along with them. Since they can only launch 6000kg to trans-martian orbit, packaging the rover and orbiter together limits your rover.

NASA launched its orbiters on separate missions, which means both the Orbiter and Rovers can be bigger without needing a ginormous launcher.

I was mostly thinking about the amount of weight that the Zhurong style lander would be able to land vs the Curiosity/Perseverance skycrane style of lander used by NASA. It's quite complex but it seems like it allows more of the mass to be in the rover vs the rover just because the Zhurong lander needs to carry the weight of the rover on top of it where the skycrane doesn't.

Do you have a reference for the electrically-repelling solar panels? They sound fascinating.

Not original commenter, but here are some relevant papers that should have publicly available pdfs if you search for them on Google Scholar:

Landis, G. A. (1998). Mars dust-removal technology. Journal of Propulsion and Power, 14(1), 126-128.

Kawamoto, H., & Shibata, T. (2015). Electrostatic cleaning system for removal of sand from solar panels. Journal of Electrostatics, 73, 65-70.

Saravanan, V. S., & Darvekar, S. K. (2018). Solar Photovoltaic panels cleaning methods: A Review. Int. J. Pure Appl. Math, 118, 1-17.

Reading the last names of the authors of these publications is refreshing, particularly in contrast to the often nationalistic comments that have peppered discussion of this rover.

Maybe the future is brighter than we think!

Care to elaborate why you think the comments on this rover are nationalistic? Or, do you feel the same way about comments regarding NASA or JAXA achievements?

Disclaimer: I'm a China/Chinese national.

I think they were referring to earlier nationalistic dismissals/unfounded skepticism.

I haven't been able to find any evidence supporting this claim.

https://www.nytimes.com/2021/05/14/science/china-mars.html says, for example:

> Days after the touchdown, the rover will roll off the lander. Like Spirit and Opportunity, Zhurong will be powered by solar panels, which are retractable so that it can periodically shake off any accumulated dust.

I'd love to learn more.

The ramp approach was used by the 1997 Sojourner rover: https://flickr.com/photos/rhubarble/268583624

> It's an interesting design, in someways the ramp is a deceptively simple concept but I'm not sure if it's safer than the US approach.

I think its closer to the Sojourner rover approach. It works fine for lower weight rovers but at higher weight you need a rocketpack or something.

I don't think the technical data being hard to find is that surprising. China has a pattern of not talking about their space missions unless they go well. Since they control their press the party only ever gets good press. It's also worth noting that the CNSA is not a civilian agency like NASA or the ESA. It's a military agency and treats programs as if they're secret military projects.

Here's a video from Chinese TV in Feb before the landing that someone else posted in this thread: https://www.youtube.com/watch?v=rBhVaihkDvc

I realize it doesn't have English subtitles, so I'll summarize some highlights of what's in there:

* interviews with scientists and engineers working on the project

* trajectory of the spacecraft and lots of talk about the challenges of reducing velocity for landing

* historical overview and context for why Mars exploration is important for science

* what to expect in the future landing and when it'll happen

It's pretty similar to video programs that NASA produces. Not sure what information you're expecting that isn't out there, but I think you're attributing to secrecy what is more easily attributable to people not translating open public reports into English.

Here's a technical review of the (engineering, not science) imaging system for Perseverance, published in November 2000 before a touchdown in February 2021:

https://link.springer.com/article/10.1007/s11214-020-00765-9

Here's the process for how the landing site was selected:

https://mars.nasa.gov/mars2020/mission/science/for-scientist...

I think this is more open than the Zhurong information has been, but I'd be happy to learn more.

CNSA is under MIIT (Ministry of Industry and Information Technology) not PLA.

> CNSA is not a cilivllian agency

Look at Wikipedia: CNSA is under the jurisdiction Ministry of Industry and Information Technology (工信部）, which itself is a civilian department, at least not less so than US department of energy.

What's the proof for your claim that CNSA is not a civilian agency?

I am no expert in china, I don't know what exactly it means. But if my country had a "State Administration for Science, Technology and Industry for National Defense", and the national space adminstration reported to them, i would assume the national defense was military.

According to https://en.wikipedia.org/wiki/State_Administration_for_Scien...

"State Administration for Science, Technology and Industry for National Defense" is a civilian ministry within the State Council of the People's Republic of China and is a subordinate agency of the Chinese Ministry of Industry and Information Technology and the superseding agency of the Commission for Science, Technology and Industry for National Defense (COSTIND).

You might as well think Ministry of Industry and Information Technology is in charge of civilian and military application of relevant tech in manufacturing and information tech. Just like DoE also manages nuclear weapons.

The DOE/NNSA has federal responsibility for the design, testing and production of all nuclear weapons. According to https://en.wikipedia.org/wiki/United_States_Department_of_En...

I am unhappy about the parent, is that people are commenting things without sensible realization of their own limitations. I frequent here, is because of people are far more sensible about their limitations on almost all topics.

But that sensibility is non-surprisingly low in China-related topics.

>China has a pattern of not talking about their space missions unless they go well

Not only space. This is the reason it always feels like the west is collapsing while Chinese hegemony is inevitable. Western news outlets publish hyper-critical editorials about western governments that wouldn't be allowed on state run media in the east.

Go read the book manufacturing consent.

Case in point, would that book have been published if all publishers were ideologically controlled by the state?

The whole point of the book is that it's not necessary for publishers to be controlled by the state for the state to control public opinion.

So, go read the book.

This is totally simplistic. If you think western journalists are incentivised to criticize basic societal norms and systemic problems, I have a bridge to sell you. I'm also not sure where you're getting these 'hyper-critical' editorials from - where I come from, nearly 150 thousand people just died in a pandemic, and the media has barely said a critical word.

Obviously, in China, they are allowed to criticize even less, but westerners do not read chinese news.

What's more, nor does anybody else.

So the image of China doing very well is not for a lack of bad press. If you read publications about China over the last decade or so, it's a constant slew of doomsaying, and negativity, mostly about problems that turned out to be very surmountable or insubstantial.

The image of China becoming more and more hegemonic is simple: look at their economic growth. Look at the size of the nation. Look at their intellectual culture. China being a very powerful country is a return to a historical norm, and is a totally reasonable development given how big their population is, how skilled it is, and its values.

Meanwhile, the west is seen as falling apart because it is having a massive identity crisis which involved things like the leader of the free world bragging about how big his nukes were on Twitter.

I'm not frankly particularly enthusiastic about China as a world power - I'm not a fan of confucianism, for example, and CCP spokespeople talk like politicians from dystopian sci-fi, but I think it's profoundly wrong to think China is deceiving the world with its masterful press controls. Far from it - the direct censorship and press controls are very blunt mechanisms most states have given up on because they don't work and if you're good at media, you don't need them anyway.

China was never really a world power, even at its height. Look back at Western history: Alexander the Great, the Roman Empire, the British Empire, or the Mongols, or further back, the Xiongnu. Han China mostly stayed confined to its own self imposed borders, with the exception of the acquisition of Xinjiang and the Tibetan plateau, and some voyages by Zheng He.

I guess what I'm saying is, if China becomes a hegemonic power, it won't be militarily, it'll be economically, sort of like monopolies/oligopolies today, and those kinds of powers can be resisted much more easily by soft power methods.

The economic growth argument fails to impress it. Every nation that goes through an agrarian->industrial conversion experiences huge economic growth until they transition to a developed service sector economy.

Much is made about Chinese infrastructure building, but did you ever look at what was done by FDR under the New Deal? 1 million kilometers of roads built. 10,000 bridges. 40,000 schools. etc. The Tennessee Valley Authority built tens of thousands of miles of electric grid. Or take progress in the Space Program of China. It looks impressive, but Von Braun founded the US rocket program in 1945, and NASA was founded in 1958. 11 years later, there were men standing on the moon.

Things only look fast now, because developed Western economies have settled into long term 2-3% service oriented economy growth. With China's declining birth rate, rising cost of living and wages, it too will experience a slowdown.

> It's also worth noting that the CNSA is not a civilian agency like NASA or the ESA

Given how many classified Shuttle missions[1] took place over the decades it was in service, and how the Hubble Space Telescope was likely a clone of a spy satellite, I don't think it's fair to say that NASA is entirely a civilian agency.

[1] https://www.space.com/34522-secret-shuttle-missions.html

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