China's Space Program Thread II

[jli88]

Does anybody have any idea of how many LEO SAR or optical satellites it will take to have 24/7 coverage of every square kilometer of the globe? It is economical or feasible to have such widespread coverage?

It depends on a lot of things, like what kind of resolution is desired, what kind of tech the satellites are using, what is meant by constant coverage, how much redundancy is needed to be baked in etc.

Strictly in principle, you can attain a 90%+ coverage of the globe with just 72 satellites placed at 1000km in LEO.

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This above essentially means that there will be atleast one satellite that is able to monitor 90% of the globe.

However, this doesn't mean 24/7 coverage since even though a satellite can say monitor 1 million km2, a single image is not that large.

The recently launched Gaojing-3 has a swath width of 130 km for example (50 cm resolution). Swath width have a trade off with resolution desired. Assuming a square image, the image is ~3,0000 km2. A very crude calculation using the Earth's surface area (510 million km2) gives 17000 satellites. Factoring in some redundancy, and the fact that you can't have the satellites perfectly aligned always, you get ~50000 satellites.

 

[by78]

New Yuanwang space tracking ship.

 

[tacoburger]

The recently launched Gaojing-3 has a swath width of 130 km for example (50 cm resolution). Swath width have a trade off with resolution desired. Assuming a square image, the image is ~3,0000 km2. A very crude calculation using the Earth's surface area (510 million km2) gives 17000 satellites. Factoring in some redundancy, and the fact that you can't have the satellites perfectly aligned always, you get ~50000 satellites.

If each satellite weights around the same as a Taijing satellite at around 250kg, then a 15ish ton to LEO rocket that multiple private companies are making can carry 60 of them per launch. Assuming that fairing space isn't an issue of course. So 50,000 satellites would need 830 launches. The launch costs alone at $2500/kg would be around $30 billion. Probably double the cost when you account for the cost of the satellite itself.

So not impossible, especially if it's build out over a decade. But probably not worth it. Around 10k sats providing 24/7 coverage over strategically important areas like the Pacific, Indian ocean etc seems more then doable though.

 

[by78]

The selection process for the fourth batch of taikonauts is almost complete. After the selection, the new taikonauts will join the current ones and participate in future missions to the Chinese space station as well as manned mission to the moon.

 

[by78]

China has signed agreements with 12 countries and organizations on the International Lunar Research Station project, including three recently added partners: Nicaragua, the Asia-Pacific Space Cooperation Organization, and the Arab Alliance for Astronomy and Space Sciences.

 

[by78]

Shenzhou-18 crew official portrait + pre-flight news conference.

 

[by78]

One year progress update on the construction of Hainan Commercial Spaceport.

 

[by78]

Chang'e-7 lunar mission will carry seven international payloads from Bahrain, Egypt, Italy, Russia, Switzerland, Thailand, and the International Association of Lunar Observatories:

– Laser corner reflector array from the Italian National Institute of Nuclear Physics.
– Lunar Dust and Electric Field Detector from the Russian Academy of Space Sciences.
– A telescope from the International Association of Lunar Observatories that will observe the Milky Way galaxy from the lunar surface.
– Lunar surface material hyperspectral imager from the Egyptian Space Agency and the Bahrain National Space Science Agency.
– Dual-channel Earth Radiation Energy Spectrometer from the Physical Meteorological Observatory (World Radiation Center) in Davos, Switzerland.
– Space weather global monitoring and sensing system from the Ministry of Higher Education, Research and Innovation of Thailand and the National Institute of Astronomy of Thailand.

 

[by78]

An official update on the manned lunar mission from by Mr. Lin Xiqiang, deputy director of the China Manned Space Engineering Office:
– All design work on the mission systems (Long March 10, Mengzhou spacecraft, lunar lander, spacesuits, etc.) have been completed and have all entered prototyping stage, with extensive testing already carried out on the many components and subsystems. Progress has been smooth. Also, the launch complex for the manned lunar mission has begun construction.

P.S. He also mentioned that China will soon welcome foreign astronauts and space tourists to the Chinese Space Station.

 

[by78]

Beijing RocketPi/Rocketπ has successfully completed the first ignition test of the Xiangnong

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LOX/Methane engine intended for the company's Darwin-1 launch vehicle.

RocketPi has successfully conducted multiple tests on its 3D-printed elbow pipes used in ignition systems. RocketPi wants to maximize the use of 3D printing in building all components of rocket engines, eventually achieving the goal of building one engine every seven days through 3D printing.