China's Space Program News Thread

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Colonel
plawolf said:
Liquid fuel provide more thrust.

Solid fuel is preferred for quick reaction launches like missiles, which you don't want to spend hours to fuel before launching, but for civilian applications, the extra efficiency of liquid fuel more than outweighs the small delay refuelling causes.
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It's true that liquid fuel has a better specific impulse than solid fuel but for similar size rocket boosters, the solid fuel type has higher thrust than the liquid fuel type since for the former it's more a matter of exposing more of the solid fuel surface and burning more of the fuel for higher thrust, whereas for liquid type the thrust is limited by the the rocket engine.

What happened is, although the solid fuel would burn off faster than the liquid fuel, the greater thrust it provides in initial stages does improve the overall payload fuel efficiency which is sort of counter intuitive because the type of fuel itself is less efficient in terms of specific impulse.
 
SinoSoldier

SinoSoldier

Colonel
plawolf said:
Liquid fuel provide more thrust.

Solid fuel is preferred for quick reaction launches like missiles, which you don't want to spend hours to fuel before launching, but for civilian applications, the extra efficiency of liquid fuel more than outweighs the small delay refuelling causes.
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Interesting; I had always presumed that solid-fueled boosters provide far greater thrust (but at a lower specific impulse), judging from preliminary specifications of the Ariane 5's P241, GSLV Mk. III's S200, and SRBs. Launch vehicles powered by solid-fueled boosters also seem to have greater initial acceleration (at least visually).

The advantage of liquid engines, as far as I know, is that their thrust can be controlled and the engine can be shut off.
 
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no_name

Colonel
I see it this way: Liquid fuel rockets contain more energy for the amount of fuel carried, but solid fuel rockets release energy faster.

So solid fuel stage is useful at the beginning when you need as much push to accelerate fast to reduce your time in the atmosphere combating drag.
 
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Colonel
no_name said:
I see it this way: Liquid fuel rockets contain more energy for the amount of fuel carried, but solid fuel rockets release energy faster.

So solid fuel stage is useful at the beginning when you need as much push to accelerate fast to reduce your time in the atmosphere combating drag.
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The thrust generated really depends on the rocket engine capacity, whether it's solid or liquid fuel .

Having said that, each of the solid fuel boosters of the Ariane 5 is about 6 to 7 times the thrust of its single core liquid fuel engine. So it would appear that it's easier to build a reliable solid fuel booster of a higher thrust than a liquid fuel type.
 
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delft

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There is a lot more about the choice for solid or liquid fuelled rocket. The choice for liquid rockets by the Soviet Union was among other things influenced by the fact that these are more easily transported by rail. Only when the rocket became too large they used aircraft to carry them, first a remodelled Bison bomber them the An-225. The Soviets also had the advantage of having developed the best liquid rocket engines.
The US transports rockets more by sea just as China will be doing to the new space launch base. But there are those huge solid fuel rockets for the Space Shuttle and also to be used in the next large booster. These consist of segments that are stacked and these travel by rail. I think it was among other things, like less able liquid rockets, chosen to provide work to a company that usually produced military solid fuelled rockets.
 
escobar

escobar

Brigadier
China put a new-generation satellite into orbit to support its global navigation and positioning network at 3:29 pm Monday. It is the 21st satellite in the Beidou Navigation Satellite System, and takes China one step closer to providing an alternative to the United States' GPS system.

The first 16 Beidou satellites formed a network that only covered China and nearby regions. The first new-generation satellite in the series, or the 17th in total, was launched in March last year to help the network transition from regional to global coverage.

Once in orbit, Monday's satellite, the fifth of the new generation, will join its four predecessors in testing inter-satellite crosslinks and a new navigation-signalling system that will set the framework and technical standards for global coverage.According to Xiang Libin, commander-in-chief of the Beidou project, the latest satellite is crucial to integrating the two signal systems for regional and global navigation and switching between the two.

"Our new intersatellite crosslink system, featuring strong disturbance resistance and high-level privacy, is the core technology to compete with other countries' navigation networks. The new satellite will fully verify our technology," said Lin Baojun, the satellite's chief designer. According to Lin, the satellite will operate without the help of ground control and broadcast continually, key requirements for navigation services.

Designed for medium Earth orbit, the satellite will fly at an altitude of around 20,000 kilometers to detect high energy particles, which abound in the orbit and threaten satellite components and functions, so that the Beidou project can better avoid their interference.

Also, the satellite carries a China-made chip that will, if proved successful, help in the design of smaller, better integrated, more reliable satellites, deputy commander-in-chief Li Guotong said.
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