The level of denial by many here of China's accomplishments here is just laughable. They're only the second country to ever land a working rover on Mars. They've right now got astronauts on their brand new space station which is being assembled in orbit via 12 launches on 3 different types of homegrown rockets over the course of 18 months.
If not for SpaceX NASA would right now have no way to even send its astronauts to ISS and the US military would be having trouble putting payloads in orbit with ULA dependent on the Russian RD-180 until they can get BE-4 working (see: Starliner/NSSL mess). Let's not even talk about SLS.
China's space program has leapfrogged into second place globally and would be pulling into first if not for the (unexpected just a handful of years ago) US ability to lean on Falcon 9/Heavy and Crew/Cargo Dragon and the hoped-for success of Starship.
The idea China is simply "copying" US accomplishments is absurd and willful blindness. We are lucky to still be barely ahead.
Chine has nailed execution at the highest level, no doubt.
But it is not yet an innovation machine. They are consistently a step behind in technological capabilities. This is not just in space technologies, it is hard to find areas where China invented and refined something truly innovative first.
Happy to be convinced otherwise with counter examples.
IIRC you can get into the tens of microseconds with an x86 box running a heavy linux graphic desktop with real time patches. Single digits with core pinning on a light headless system.
Bear in mind that real time performance and throughput are perpetually at odds with each other. Long story short, scheduling things such that everything happens in a tight time window means you need to leave gaps in the timeline.
This tradeoff is variable so you can loosen requirements for running something like a rover where there isn't really all that much need for tight realtime control, it's not trying to achieve micron positioning as it drives around. That means you can use a more efficient CPU and lower your idle current which is probably the real constraint here.
Looks like Kylin OS uses the Linux kernel. While not impossible to use in a real-time application (SpaceX Falcon 9 uses it) there's definitely work involved in stripping it down enough to work as an RTOS. NASA Perseverance uses VxWorks instead, which was designed from the beginning as an RTOS. VxWorks is also proprietary and looks like it's US export restricted.
8 ms isn't hard to hit. 8 ms with 100% reliability is.
Less than 1us is relatively straightforward on an embedded system.
My application was simulcast for a software defined radio. It was running on a TMS320 DSP (192MHz) with DSP/BIOS as the operating system. Timing was driven by a GPS 1PPS pulse connected to an interrupt pin. The absolute response time was around 100ns and repeatability was of the order of 10 nanoseconds (dominated by the drift between the 1PPS and the processor's clock).
Seriously depends on what you do. Iq you're doing really low-level stuff, you could probably get in the microsecond range quite easily (for trivial stuff). But 8 milliseconds doesn't sound that impressive to me.
It's only impressive in the sense that they have to use really shitty computers to achieve that number. Playing around with Rust on a reasonably powerful x86 box, you'll have no problem writing programs with a response time in microseconds, but they aren't using the same computers you and I do (or Rust for that matter). Word on the street is that most space tech is based on PowerPC, since you can buy decently powerful radiation-hardened RISC chips without breaking the bank (only $300,000 or so).
If based on anything described here https://en.wikipedia.org/wiki/Kylin_(operating_system) I'm unimpressed, the same way I'm unimpressed by Space-X using Linux. OTOH, who really cares if it flies, works, whatever without crashing?
If my impression is correct, this is based on Linux kernel.
Since other comments appearing not mentioning that, just add here in case someone mistaken it with a custom embedded OS. (Although I know little about embedded OS either).
In some "hard real time" systems failure to meet the deadline is treated as system failure. Vs "soft real time" where its a transient error. So the goal is bounded response time/latency/jitter at the 100th percentile.
Users interesting in this story may also be interested in this great 55 minute documentary covering the first few years of NASA's Curiosity rover: https://www.youtube.com/watch?v=qaUhLXolGaI (the active rover before NASA's more recent Perseverance landing).
Can anyone explain the sound in the clip? So Mars atmosphere is different, making sound travel different? But the weird echo and metallic muffle, what explains that - why would the machine be particular noisy?
How did China know how to make their rover without sending a bunch of probes onto Mars? Did NASA share its data and info with China so that they knew what specs to make the solar panels, etc?
CNSA did acknowledge that they benefited from prior explorations to mars done by everyone, including NASA, soviet union, ESA and more. They are able to find general scientific data on mars, such as atmospheric density, composition, potential weather events, general topography in the public domain (I mean, wikiepdia has a lot of these information). For these, they should and are appreciating scientists going before them are sharing these information in the public domain. But I am sure NASA and everyone else did not release all super detailed data, such as detailed topology maps. And from public available info, they also know about general designs of NASA's landers and rovers, and the troubles NASA has faced operating these crafts on mars. If they learn from NASA's experiences, they can avoid a huge amount of unknowns and negative encounters. These are significant assistance when you are engineering systems. The pioneer is always way more difficult. So of course respect is paid and hats off to NASA and other pioneers.
But knowing these are not enough for you to build and operate a fully successful mission. Even if you had the entire CAD file of a NASA lander and rover, you don't know why they are designed that way, you will not operate, use and troubleshoot issues correctly. You need to build the system from ground up, so the people on your teams have full understanding of every single "why" and "how". Only then will you have full control and ensure the mission is success.
I am sure you had experience taking ownership to a software project written by others. You always have go to the original designer to ask "why" and "how". The knowledge transfer often last months and countless meetings. If you don't fully understand, you can't fix issues or build new features. Most people would rather build their own then to fix something they don't fully understand.
For CNSA, they can access public available data. Then they have to simulate, wind tunnel tests, how to land, what shape of lander they need, how to balance and control the lander etc. They need to build up their understanding of the entire system. They actually has been improving their technology and understanding of atmospheric and controlled powered landing from earth and moon missions. One of things they did differently is adding a flap to the lander to stabilize it in flight, they said it was to increase the lander's robustness when encountering more extreme weather.
For solar panels, knowing the distance to the sun, the atmospheric density, pressure, composition, force of gravity on mars, you can estimate the theoretical max of the solar energy available per unit of area. Then you could say assume only 30% is available due to weather. I am sure they have more advanced ways to estimate. Interesting fact about the rover, it has a solar heat capture and retention system. And they use the heat for thermo-control at night instead of electricity captured from solar panels, saving electricity use.
For where to land, topology and maps of mars is in public domain. You can find a general region where to land but these data are not detailed enough to actually land. And mars surface could have changed since these were captured. So tianwen-1 contains a orbiter and the lander. The orbiter has instruments such has high resolution imaging. They arrived mars orbit in February, and the 3 months since the orbiter was collecting data on mars. From these data they finalized their landing plans.
This is China's first spacecraft to ever travel this far. They also don't have communication network between mars and earth. So Tianwen-1's orbiter is also a communication satellite.
The impressive thing is the engineering side, how they engineered the system that each component all worked correctly in one go. The rocket: the rocket required to launch tianwen-1 (weighs 5 tons) to mars orbit was only tested successfully in dec 2019. China also doesn't have earth mars communication satellites and fully operational deep space communication system before this mission. This the first time all these system are tested live. To fly a spacecraft to mars for the first time, have it being captured by mars, and orbit mars correctly. Take data on mars. Release the lander. The lander going through atmosphere, releasing parachute at super sonic speeds, the lander detaches from parachute and uses a rocket engine to fly. At height of 100m, optical imaging and laser maps out the ground and autonomously navigate the craft to soft land on flat ground. Orbiter forms communication link between mars rover and earth. Mars rover collects sun light, drives, survives the elements of mars (so far).
Overall, they are standing on the shoulders of people who went before them. One shouldn't look down on their success, nor should they over-hype their success.
CNSA said Zhurong landed 3km away from their designed coordinate. For the first 42 mars days, zhurong traveled 236m.
That's why the rover landing happened 3 months after the probe reached Mars orbit. They spent that time to do all the reconnaissance work to prepare the landing.
Also this is the reason this mission is considered to be a great success, it shows their ability to landing on a totally unknown planet.
Once you've got that down pat, it's not that different to land one on Mars, especially since the Chinese rover was small enough not to require the elaborate skyhook approach.
Also, NASA is legally prohibited from cooperating with China on anything space-related.
> How did China know how to make their rover without sending a bunch of probes onto Mars?
Why would they need probes? The Mars atmospheric composition isn't exactly classified information, they know it's a solid surface. The rest is just math and some very complex engineering.
I'm curious about the use of a wireless camera to photograph the lander and the rover. It seems like extra weight and complexity for purely PR reasons.
Yes, you need to inspect each vehicle, but the rover can clearly examine the lander and move around it, while the lander needs only one camera, possibly an existing descent one, to inspect the rover.
Possibly a technology test? I don't think it's any more or less silly than a helicopter that also doesn't actually do any science other than testing out the concept for future missions.
It may be scientifically worthless, but the public pays for these missions and the public likes pretty pictures. JunoCam on NASA's Jupiter orbiter, Juno, was added in order to give the public pretty pictures of Jupiter.[1] I personally think that's really cool.
Something could go wrong with any of those and cameras can be pretty light these days since we put them in doorbells, so I doubt they're sweating it when there are multiple potential benefits to having it there. :)
Curiosity weighed almost 2000 lbs, so it's not like rovers on Mars are afraid to weigh anything which is not to say they don't run the numbers.
These missions usually have scientific AND engineering objectives. Having a spare camera that the hover put anywhere may not be very valuable scientifically, but it validates the engineering of all communication, power and mechanical systems involved. That will allow more advanced scientific objectives in the future.
Space exploration is a prestige game among world powers since the very beginning. China needs good PR pictures to show they can do just as well as NASA. If we are lucky they will try to one up each other for decades to come.
I would be very interested in seeing any technical info on exactly what solar cells it uses, since the top-quality triple junction 30%+ efficient GaAS cell manufacturers (space qualified) are not based in east asia anywhere, but in the USA. Spectrolab is a subsidiary of Boeing last I checked.
[+] [-] themgt|4 years ago|reply
If not for SpaceX NASA would right now have no way to even send its astronauts to ISS and the US military would be having trouble putting payloads in orbit with ULA dependent on the Russian RD-180 until they can get BE-4 working (see: Starliner/NSSL mess). Let's not even talk about SLS.
China's space program has leapfrogged into second place globally and would be pulling into first if not for the (unexpected just a handful of years ago) US ability to lean on Falcon 9/Heavy and Crew/Cargo Dragon and the hoped-for success of Starship.
The idea China is simply "copying" US accomplishments is absurd and willful blindness. We are lucky to still be barely ahead.
[+] [-] gpt5|4 years ago|reply
But it is not yet an innovation machine. They are consistently a step behind in technological capabilities. This is not just in space technologies, it is hard to find areas where China invented and refined something truly innovative first.
Happy to be convinced otherwise with counter examples.
[+] [-] vmception|4 years ago|reply
I would like their program to share data with the world. The more the merrier!
[+] [-] lazarohcm|4 years ago|reply
[+] [-] eunos|4 years ago|reply
real-time response accurate to 8 milliseconds range. I am not that familiar with embedded software, but does that value really difficult to achieve?
[+] [-] edrxty|4 years ago|reply
Bear in mind that real time performance and throughput are perpetually at odds with each other. Long story short, scheduling things such that everything happens in a tight time window means you need to leave gaps in the timeline.
This tradeoff is variable so you can loosen requirements for running something like a rover where there isn't really all that much need for tight realtime control, it's not trying to achieve micron positioning as it drives around. That means you can use a more efficient CPU and lower your idle current which is probably the real constraint here.
[+] [-] magicsmoke|4 years ago|reply
8 ms isn't hard to hit. 8 ms with 100% reliability is.
[+] [-] femto|4 years ago|reply
My application was simulcast for a software defined radio. It was running on a TMS320 DSP (192MHz) with DSP/BIOS as the operating system. Timing was driven by a GPS 1PPS pulse connected to an interrupt pin. The absolute response time was around 100ns and repeatability was of the order of 10 nanoseconds (dominated by the drift between the 1PPS and the processor's clock).
[+] [-] danhor|4 years ago|reply
[+] [-] smoldesu|4 years ago|reply
[+] [-] LargoLasskhyfv|4 years ago|reply
[+] [-] justicezyx|4 years ago|reply
If my impression is correct, this is based on Linux kernel.
Since other comments appearing not mentioning that, just add here in case someone mistaken it with a custom embedded OS. (Although I know little about embedded OS either).
[+] [-] carlsborg|4 years ago|reply
[+] [-] grawprog|4 years ago|reply
[+] [-] crazypython|4 years ago|reply
[+] [-] Black101|4 years ago|reply
HFTs are in the nanosecond range... so probably not that hard.
Also, my ping to remote servers is often 5ms...
[+] [-] slmjkdbtl|4 years ago|reply
[+] [-] someperson|4 years ago|reply
[+] [-] throwaway4good|4 years ago|reply
[+] [-] plank_time|4 years ago|reply
[+] [-] russli1993|4 years ago|reply
But knowing these are not enough for you to build and operate a fully successful mission. Even if you had the entire CAD file of a NASA lander and rover, you don't know why they are designed that way, you will not operate, use and troubleshoot issues correctly. You need to build the system from ground up, so the people on your teams have full understanding of every single "why" and "how". Only then will you have full control and ensure the mission is success.
I am sure you had experience taking ownership to a software project written by others. You always have go to the original designer to ask "why" and "how". The knowledge transfer often last months and countless meetings. If you don't fully understand, you can't fix issues or build new features. Most people would rather build their own then to fix something they don't fully understand.
For CNSA, they can access public available data. Then they have to simulate, wind tunnel tests, how to land, what shape of lander they need, how to balance and control the lander etc. They need to build up their understanding of the entire system. They actually has been improving their technology and understanding of atmospheric and controlled powered landing from earth and moon missions. One of things they did differently is adding a flap to the lander to stabilize it in flight, they said it was to increase the lander's robustness when encountering more extreme weather.
For solar panels, knowing the distance to the sun, the atmospheric density, pressure, composition, force of gravity on mars, you can estimate the theoretical max of the solar energy available per unit of area. Then you could say assume only 30% is available due to weather. I am sure they have more advanced ways to estimate. Interesting fact about the rover, it has a solar heat capture and retention system. And they use the heat for thermo-control at night instead of electricity captured from solar panels, saving electricity use.
For where to land, topology and maps of mars is in public domain. You can find a general region where to land but these data are not detailed enough to actually land. And mars surface could have changed since these were captured. So tianwen-1 contains a orbiter and the lander. The orbiter has instruments such has high resolution imaging. They arrived mars orbit in February, and the 3 months since the orbiter was collecting data on mars. From these data they finalized their landing plans.
This is China's first spacecraft to ever travel this far. They also don't have communication network between mars and earth. So Tianwen-1's orbiter is also a communication satellite.
The impressive thing is the engineering side, how they engineered the system that each component all worked correctly in one go. The rocket: the rocket required to launch tianwen-1 (weighs 5 tons) to mars orbit was only tested successfully in dec 2019. China also doesn't have earth mars communication satellites and fully operational deep space communication system before this mission. This the first time all these system are tested live. To fly a spacecraft to mars for the first time, have it being captured by mars, and orbit mars correctly. Take data on mars. Release the lander. The lander going through atmosphere, releasing parachute at super sonic speeds, the lander detaches from parachute and uses a rocket engine to fly. At height of 100m, optical imaging and laser maps out the ground and autonomously navigate the craft to soft land on flat ground. Orbiter forms communication link between mars rover and earth. Mars rover collects sun light, drives, survives the elements of mars (so far).
Overall, they are standing on the shoulders of people who went before them. One shouldn't look down on their success, nor should they over-hype their success.
CNSA said Zhurong landed 3km away from their designed coordinate. For the first 42 mars days, zhurong traveled 236m.
[+] [-] sinxccc|4 years ago|reply
Also this is the reason this mission is considered to be a great success, it shows their ability to landing on a totally unknown planet.
[+] [-] Clewza313|4 years ago|reply
https://en.wikipedia.org/wiki/Chinese_Lunar_Exploration_Prog...
Once you've got that down pat, it's not that different to land one on Mars, especially since the Chinese rover was small enough not to require the elaborate skyhook approach.
Also, NASA is legally prohibited from cooperating with China on anything space-related.
[+] [-] EMM_386|4 years ago|reply
Why would they need probes? The Mars atmospheric composition isn't exactly classified information, they know it's a solid surface. The rest is just math and some very complex engineering.
[+] [-] spaetzleesser|4 years ago|reply
[+] [-] Vaslo|4 years ago|reply
[+] [-] pseudolus|4 years ago|reply
[+] [-] tluyben2|4 years ago|reply
[+] [-] eunos|4 years ago|reply
[+] [-] imglorp|4 years ago|reply
Yes, you need to inspect each vehicle, but the rover can clearly examine the lander and move around it, while the lander needs only one camera, possibly an existing descent one, to inspect the rover.
Is Earth in an ideology war again?
[+] [-] iso1631|4 years ago|reply
And that's the thing that gets a public supportive of your space program and thus the resources keep flowing.
Drop the PR and you drop the funding.
[+] [-] luma|4 years ago|reply
[+] [-] DiogenesKynikos|4 years ago|reply
1. https://en.wikipedia.org/wiki/JunoCam
[+] [-] CMay|4 years ago|reply
Curiosity weighed almost 2000 lbs, so it's not like rovers on Mars are afraid to weigh anything which is not to say they don't run the numbers.
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