China's Space Program News Thread

[by78]

A series of high-resolution images marking the successful maiden launch of CZ-8.

 

[by78]

 

[by78]

 

[eprash]

So since Long March 5's success this year I've been looking up its stats, and particularly the engines and it soon jumped out at me that YF-100 engine is a goddamn work of art. Oxygen-rich staged combustion is already hard enough but on top of this YF-100 has variable mix ratio and variable thrust.

It's little wonder than they took this engine and made Long March 6 by building a 3.35m core with one YF-100, then Long March 7 with a 3.35m core with two YF-100. Then they basically took four Long March 7 core, added nose cones to them and made them into boosters for Long March 5.

So that brings us to Long March 8R:
View attachment 66787
Notice how it lands with one engine firing on the core. The Long March 8 core is basically identical to Long March 7, 3.35m diameter with two YF-100. The two "boosters" that remain attached are not actually solid fuel, but instead liquid fuel 2.25m (Long March 1 diameter) rockets powered by a single YF-100 - basically the "boosters" are Long March 6 core, but made skinnier and longer.

Then it occurred to me: those aren't boosters at all, that whole contraption is actually just a single rocket stage with four YF-100 engines split into three separate stacks instead of crammed into a single tube. By firing 1/4 engine at launch at landing it allows you to throttle a single YF-100 low enough to land the whole thing safely, like how Falcon lands with 1/9 engines firing.

So why not design a new 5m first stage using tooling from Long March 5 and put four YF-100 on the bottom? Well because the core is already done from Long March 7 and is mature and the "boosters" can be made with Long March 1 tooling based on the work done on Long March 6 core. They basically came up with a way to build a more powerful first stage with enough engines to work for stage recovery by playing lego with existing parts.

Why would they go for such an unorthodox nozzle configuration the weight distribution is just weird on one side you have two engines and the other side have one not to mention the two sides that doesn't have any engines at all, a Soyuz style one longmarch 6 core and four long march 6 boosters configuration makes way more sense

 

[by78]

A dense and comprehensive paper on the CZ-8 program published in the Journal of Deep Space Exploration, titled CZ-8: The Forerunner of Long March Rocket Series on the Innovations of Commercialization and Intelligence. The paper is completely beyond my ability to translate. It seems to cover several planned variants of CZ-8 and lays out a roadmap for its future development, including intelligent launch guidance and reusable launcher (with autonomous landing).

Please, Log in or Register to view URLs content!

Please, Log in or Register to view URLs content!

Here's an English abtract:
This paper reviews the latest innovations of the Long March 8(LM-8)launch vehicle. The launcher fully inherits the achievements of Chinese in-service and new generation rockets, and focuses on launching satellites to the sun-synchronous orbit(700-1 000 km), taking into account the launch services for LEO and GTO satellites. LM-8 is available in both combinatorial and integrative configurations for a variety of missions. In order to enhance market competitiveness, a series of innovative practices have been taken, including agile manufacturing, system integration, responsive launch, autonomous and unattended operation, and simplified launch site infrastructure. In response to the future trend of intelligent rocket, LM-8 actively explores the autonomous technologies such as onboard dynamic trajectory planning, active control of take-off drift, and automated launch window correction. It also paves the way for reusable launcher in steps, conducts the demonstration for vertical landing with side and core boosters strapped together, and makes progresses in large-scale light landing mechanism, autonomous guidance method, etc. These innovations forge the LM-8 into a cost effective, easily handled, and highly reliable and safe launch vehicle.

 

[taxiya]

Why would they go for such an unorthodox nozzle configuration the weight distribution is just weird on one side you have two engines and the other side have one not to mention the two sides that doesn't have any engines at all, a Soyuz style one longmarch 6 core and four long march 6 boosters configuration makes way more sense

First of all, the LM-6 has nothing to do with LM-8, see #6332 for details. There is no LM-6 core or booster. LM-6 is an off-shoot specific purpose vehicle.

The off-center for LM-8R reusable variant is: 1. a have-to-do choice. 2. It is not really a problem either.

1. YF-100 is rated at 65% down-throttling. In test, it has been claimed to go as deep as 50%. LM-8 has totally 4 YF-100, turning off all three will give 25% of lift-off thrust with one YF-100 in full thrust, with the last engine running at 50%, we get 12.5% thrust. This is the maximum allowed thrust for landing. There is no other way than this before a YF-100 variant that can do deeper throttling at 20%-30%.

2. off-center TVC control just need the engine's TVC being slightly compensated when restarted. This is not difficult, the recent SpaceX SN8 test has demonstrated it. Note, CNSA had this idea in LM-8R without waiting for SpaceX to demonstrate it, I say this to prevent some SpaceX fans to claim the credit.

 

[Dante80]

2. off-center TVC control just need the engine's TVC being slightly compensated when restarted. This is not difficult, the recent SpaceX SN8 test has demonstrated it. Note, CNSA had this idea in LM-8R without waiting for SpaceX to demonstrate it, I say this to prevent some SpaceX fans to claim the credit.

Booster engine off-center TVC control has been around since at least the mid 2000s, with the Atlas 411. CNSA or SpaceX certainly cannot claim something like that.

(click for awesome res)

Please, Log in or Register to view URLs content!

 

[ZeEa5KPul]

What's the propellant used by LM-8? There's no condensation from cryogenics like LOX, but there's no orange fumes from hypergolics.

 

[Dante80]

What's the propellant used by LM-8? There's no condensation from cryogenics like LOX, but there's no orange fumes from hypergolics.

It is the standard kerolox mix (RP1 and LOX) for the first two stages.
The last one uses hydrolox (LH2 and LOX)

The condensation we tend to witness in rocket stages depends on a lot of different factors (like air humidity, tank insulation, temperature or wind speed).

 

[taxiya]

Booster engine off-center TVC control has been around since at least the mid 2000s, with the Atlas 411. CNSA or SpaceX certainly cannot claim something like that.

(click for awesome res)

Please, Log in or Register to view URLs content!

Neither I nor CNSA is claiming credit or tried to. I said "prevent SpaceX fan".

Besides, your example of Atlas 411 is nothing unique of off center TVC control. At take off, a lot of rockets do so. What was talked about originally was "off center vertical landing". It is unique issue of its own.