Rockets of Today

LONG MARCH (Chángzhēng, 长征) — new models — China, 2015

Long March 5

The Chinese finally got tired of hypergolic fuel, what with its toxicity and pollution and mediocre performance, so they started working on some more modern rockets with cryogenic fuels. They’re also tired of dropping spent rockets onto rural villages, so they’re finally building some launch facilities on the coast — Wénchāng Space Launch Site (文昌航天发射场) on the island of Hainan. And to start off this new era, they decided to build something big to launch from there. They called it the Long March 5 — informally, the “fat five” (pàng-wū). And as before, they are making a modular system out of it.

Like the heavier versions of the Long March 2 and 3, the 5 has four liquid fueled strap-on boosters, but these burn kerosene and lox instead of hypergolics. Each side booster has two YF-100 staged combustion engines, and is the size of a core stage from a classic Long March 2, 3, or 4. And later, there are supposed to be two versions of the side booster, with the other being a skinny version with only one engine, but that has yet to fly. They even talk about an in-between version of the rocket, using two fat boosters and two skinny ones. The new king-sized core stage also has two engines, and as in the Ariane 5, they burn hydrogen. This new engine is called the YF-77. The upper stage also has two hydrogen engines, in a much smaller size, and there’s an optional hypergolic third stage. This rocket has plenty of muscle, and thanks to the hydrogen, plenty of delta-V for high orbits. It can throw six tons at Mars. But its second flight was a failure due to a bad YF-77 turbopump, so it has been a struggle to get the thing into regular use. After three launches they added a 5B version, which has no upper stage. It’s intended for heavy loads in low orbit, which go directly atop the hydrogen core. They use this for space station modules. And they started working on a triple core version called the 5G or 5 Dengyue, which they intend to use to send people to the moon, but that ended up becoming the Long March 10 instead — see below.

Long March 6

Long March 6

They also wanted a small modern rocket, so they tried to make one based on the skinny version of the new side booster. But that proved too weak, so they made the Long March 6 by taking one of the fat side boosters, shortening it, removing one engine, and using that as a first stage. This was the first rocket in the new family to fly, and it launches from the Taiyuan spaceport in the mountains, rather than the new coastal site. It’s designed for rapid preparation. It used no strap-ons of its own in its original version, and had dinky upper stages, sized to fit the narrow booster instead of the one they ended up using. The second stage also burns kerosene, and the third (if present) is a hypergolic kick stage. Given the contradictory information given about it, I suspect that two different kick stages have been used: one being similar to a Yuanzheng (see below) and burning UDMH, and the other having four dinky thrusters in lieu of a main engine, burning kerosene with peroxide.

There is also now a 6A version which uses the full length two-engine version of the booster, and is their first rocket to use solid strap-ons. It also has a fatter second stage than the original 6, but as yet I have not been able to get any figures on how much larger these stages are. Add up all those upgrades and the 6A can do four tons to sun-synchronous orbit (the only figure they give), where the original only did one ton. It is getting some commercial use.

The 6 and 6A have no failures at delivering sats correctly, but they do have a post-delivery mishap, in which an upper stage was supposed to reenter but instead blew up into a cloud of orbiting shrapnel.

Long March 7

And between these extremes, they wanted a midsize rocket to carry forward the classic design of the old school Long March models, reusing many of the old parts — specifically, those of the 2F — with the new motors. This became the Long March 7, though at first it was provisionally just called the 2F/H. This also uses YF-100 engines (or a very similar related model), and essentially they just put four of the new skinny boosters around one of the fat ones. This means the 6A would pretty much be just a 7 without the liquid strap-ons... at least superficially. Behind the scenes, though the 6 and the 7 use compatible dimensions and engines, the two were actually developed by different teams, and have many differences — the 7 being a direct offshoot of the Long March 5 project and the 6 being done by the Shanghai Academy of Spaceflight and Technology.

In 2020 they added a 7A which has a hydrogen-burning upper stage, updated from the one used on the Long March 3. You could say that the original 7 replaces the Long March 2 and the 7A replaces the Long March 3. I guess the 6 could be considered as the new Long March 4, though it’s a step down in capacity. So the new system covers a wider range than the old, at both ends. Between the 6 and 7, they ended up cancelling the lighter versions of the 5 — they had originally planned to not only include a version with no side boosters, but also to make the core stage in two different diameters.

With the Long March 5/6/7 project they also debuted a new kick stage, the Yuanzheng-1, which can deposit satellites in high or multiple orbits. It uses hypergolics, and flies on the old rockets as well as the new ones. It has variants for each different rocket it’s used on, such as YZ-1A for the 7, YZ-1S for the 2C, YZ-2 for the 5, and YZ-3 for the 2D. It uses a single UDMH-burning engine called the YF-50D, which may be pressure-fed, I’m not sure.

Long March 8 (and 12?)

Then they started on a Long March 8. The basic idea of the 8 is to be the 7 but cheaper. It uses the same core stage as the 7, and for now the same side boosters, though only two. The only real difference from the 7 is in the second stage, which is the hydrogen burning third stage from the Long March 3 and 7A, bumped down to second position. They could have just called it the 7B, but they intend that over time it will diverge more significantly from the 7. The original plan was to replace the liquid side boosters with solid ones, but now they intend to make it reusable, and land the core stage with the boosters still attached. If that works, the 7 may become obsolete. As yet the 8 has only made expendable flights, and this will apparently be true for some time to come. They apparently plan to put grid fins on the core stage, like a Falcon; such fins have been added to a Long March 4 booster to try them out. They want to achieve reuse by 2025.

Apparently they are also working on a similar rocket to the 7 in a maderately larger diameter, to be called the Long March 12. It hasn’t yet been described as reusable. Its purpose is just to carry somewhat heavier loads than the 7, up to ten tons.

They also want to increase the smarts of their automation, using AI techniques. They say at least a third of historical rocket failures could have been prevented if the guidance control had been more intelligent and adaptable. These improvements will be tested in the old Long March series, which will be upgraded for as long as they stay in service.

Long March 9 and 10

For the longer term, they are also working on a Long March 9, which is much more ambitious. If built, it will be enormous, with a capacity larger than the Saturn V and a mass of over 4000 tons. In their preliminary designs, they were apparently looking at having four kerosene engines on each of the four side boosters, and four really big dual-nozzle kerosene engines on the core. The core would be 9.5 or 10 meters across — as thick as a Saturn V first stage, and a lot taller — and each booster five meters wide, like the core stage of the 5. The Russian Yenisei would look puny next to it, though the 9’s gain in capacity over the Yenisei would be only about 40 percent. Even the upper stage would be not much smaller than Apollo’s second stage. They’re building a new staged-combustion hydrogen engine for that derived from the YF-77 gas generator used in the 5’s core stage, but with triple the thrust. They will try for some reuse in the 9, but not at first.

No wait, that design has now been dropped, along with the big YF-133 kerosene engine it would have used, which was apparently already well along in development. They’re starting over with a new plan: imitate SpaceX. The new tentative design is a methane-burning reusable first stage ten meters in diameter, with grid fins but no visible legs. The expendable second stage would be enormous, and a third stage atop that would give it a 150 ton capacity. The methane engine will use full flow staged combustion just like SpaceX’s, and the booster will have 26 of them in current plans. We shall see how this evolves. If they start actually building and testing it, I’ll give it a separate page.

They might still cancel the Long March 9. The alternate plan is the Long March 10, which as mentioned was originally just going to be a triple-core 5G, but has now changed substantially, though it still looks superficially similar to that idea, as the bottom layer consists of three side-by-side boosters which are five meters in diameter. But where the original fat-five core was mostly full of hydrogen, which takes up a lot of volume for the amount of propellant it produces, the cores of the 10 are packed with kerosene and lox, giving it about three times the fuel mass. And instead of the two YF-77 hydrogen burners on the 5, which are built for specific impulse rather than for thrust, each core of the 10 has seven YF-100K staged-combustion engines, each one of which is more powerful than a YF-77. With all that junk in its triple trunk, it’s going to weigh somewhere toward 2000 tons even before any upper stages are added, and the thrust will be over 26,000 kilonewtons, or around three quarters of a Saturn V’s worth.

And the second stage also burns kerosene, with two vacuum-belled YF-100M engines. Only in the third stage do we start using hydrogen, so it can go out to the moon with some efficiency. It’s similar to the second stage of the 5, but with three engines instead of two. And what goes on top of that? Their new Mèngzhōu crew capsule. Or, a yet-to-be-built Lǎnyuè (揽月) lunar lander. To put people on the lunar surface, they’ll send the lander on one Long March 10 and the crew capsule on another, to dock in lunar orbit, similarly to how the US Artemis program sends the lander up separately. I should probably also move this one to a separate page once it gets real enough.

And the 10 isn’t just for the moon. Reduce it to a single core, and the 10A becomes the new launcher to send the Mengzhou capsule up to their space station. And for such light work, it has fuel to spare, so they’re going to make the booster reusable. By that time they should have reusability working already in the Long March 8, so they don’t expect that to be difficult. I suppose they’ll have to develop a smaller second stage for the 10A.

And the 9 is still going ahead alongside this, though perhaps less aggressively now that the 10 has been selected for the lunar program. They want to use it to send a sample return mission to Mars, and eventually people. But they don’t expect the 9 to fly until at least 2030. With that big boy, they also hope to put huge solar arrays into geosynchronous orbit.

(There’s also a Long March 11, which is a quick and dirty solid fuel job with four stages. This was covered in the earlier article on China’s missile-derived solid fuel launchers.)

Speaking of ambition, two early missions for the 5 were a Mars lander, and a lunar lander that successfully brought moon rocks back to Earth. Then they commenced building their space station with the 5B. They’re planning a second moon-rock flight, and two orbital telescopes. And note that the maiden 5B flight was a test of a new crew capsule. They’re counting on this beast for the kinds of high-prestige missions which will put China solidly in the front rank of space powers. And China is already so active and ambitious in space that Russia is now only the number three spacefaring nation.

One controversial aspect of these missions is that they don’t control where the stages reenter the atmosphere. Most rockets save a drop of fuel for the upper stage to put itself back into the atmosphere when and where it’s safest to come down. But the Chinese don’t, and with the 5B especially, this means that a really big core stage with heavy engines might come down in an inhabited area.

Long March 5: mass 854 t, diam 5 m (11.7 at base w/o fins), thrust 10600 kN, imp 4.2 km/s, gas generator (hydrogen) + staged combustion (kerosene), payload 25 t (2.9%), cost unknown, record 11/0/1 through April 2024.
Stage name CZ-5-300 CZ-5-500 CZ-5-HO Yuanzheng-2
Role (pos) count booster (S) ×2?|4 core (1) upper (2), opt kick (3), opt
Diameter (m)   3.35   5.00   5.00
Liftoff mass (t) 150    171    33.6
Empty mass (t) 13   15    6.7
Fuel mass (t) ~37    ~24    ~4.5
Oxidizer mass (t) ~100     ~132     ~22.4 
Fuel type kerosene hydrogen hydrogen UDMH
Engine YF-100 ×2 YF-77 ×2 YF-75D ×2 YF-50D
Power cycle staged gas gen closed expander ?
Chamber pres. (bar) 180    102    41  
Ox./fuel ratio   2.70   5.45   5.00
Thrust, vac max (kN) 2680     1400     166nbsp;    6.5
Thrust, SL initial (kN) 2380     1020    
Spec. imp, vac (km/s)   3.30   4.20   4.30   3.09
Total imp, vac (t·km/s) 445    658    117   
Long March 6: mass 103 t (6A 530 t), diam 3.3 m, thrust 1200 kN (6A 7200 kN), imp 2.9 km/s, staged combustion (kerosene), payload 1.5 t (6A ~6 t?), cost unknown, record 17/0/0 through April 2024.
Stage name ? (6A) L-77? (6) ? (6A) L-14? (6) ? (6A) PBV? (6?)
Role (pos) count booster (S) ×4 core (1) core (1) upper (2) upper (2) kick (3), opt
Diameter (m)   2.00   3.35   3.35   2.25   3.35   2.25
Liftoff mass (t) 84   15   1.0?
Empty mass (t)  1.6
Fuel mass (t) ~20.8  ~3.8
Oxidizer mass (t) ~56.2  ~9.6
Fuel type ? kerosene kerosene kerosene kerosene UDMH? kerosene?
Engine ? YF-100 YF-100 ×2 YF-115 YF-115 YF-50E? YF-85 ×4?
Power cycle solid staged staged staged staged pressure-fed?
Chamber pres. (bar) 180    180    120    120   
Ox./fuel ratio   2.70   2.70   2.50   2.50
Thrust, vac max (kN) 1210     1340     2680     180    180    16?  6.5?
Thrust, SL initial (kN) 1190     2380    
Spec. imp, vac (km/s)   3.30   3.30   3.28   3.28    2.80?
Total imp, vac (t·km/s) 248    44  
Long March 7 (four added boosters): mass 597 t, diam 3.35 m (7.8 at base w/o fins), thrust 7200 kN, imp 2.9 km/s, staged combustion (kerosene), payload 13.5 t (2.3%), cost unknown, record 13/0/1 through April 2024.
Long March 8 (two boosters): mass 356 t, diam 3.35 m (7.8 at base w/o fins), thrust 4800 kN, imp 2.9 km/s, staged combustion (kerosene), payload 8.1 t (2.3%), cost unknown, record 3/0/0 through April 2024.
Stage name L-67 or K2 L-137 or K3 L-72 (7 or 7A) unnamed (7A or 8) Yuanzheng-1A
Role (pos) count booster (S) ×0|2|4 core (1) upper (2) upper (2|3) kick (3|4?), opt
Diameter (m)   2.25   3.35   3.35   3.00
Liftoff mass (t) 73   150    90   ~20   
Empty mass (t) 13   19  
Fuel mass (t) ~18.1  ~37    ~20.3   ~2.98
Oxidizer mass (t) ~48.9  ~100     ~50.7  ~15.2 
Fuel type kerosene kerosene kerosene hydrogen UDMH
Engine YF-100 YF-100 ×2 YF-115 ×4 YF-75(D) ×2 YF-50D
Power cycle staged staged staged? gas gen ?
Chamber pres. (bar) 180    180    120    37.6
Ox./fuel ratio   2.70   2.70   2.50 ~5.1
Thrust, vac max (kN) 1340     2680     590    167.7   6.5
Thrust, SL initial (kN) 1200     2400    
Spec. imp, vac (km/s)   3.30   3.30   3.30   4.30   3.09
Total imp, vac (t·km/s) 215    445    235    ~78.2