Rockets of Today

R-7 / SOYUZ (Союз) — Russia, 1957

Most of the older orbital rockets originally started out as designs for intercontinential ballistic missiles. The R-7 is no exception. In fact, it was the daddy, the original ICBM — the first rocket in the world able to throw a heavy payload at a target 8000 miles away. In that role it was known as the Semyorka (Семёрка), which just means Seven. It wasn’t long before they made bombs able to be ICBMed on significantly smaller rockets, making the R-7 obsolete for that role, so they improved it and used it to launch Sputnik. Then they improved it some more and launched Yuri Gagarin on it. Its creator, the legendary Sergei P. Korolev (Королёв), had this in mind all along; he designed it so that the military goals would end up also supporting space exploration. For this reason, he is called the father of spaceflight.

The R-7 in its early days was far ahead of any other country’s rockets, and it has been evolving and improving ever since. This one rocket is why the Soviet Union won all the early stages of the space race, despite America soon having better vehicles and satellites to put on top. It has done far more orbital launches than any other rocket family, both manned and unmanned (though the Shuttle has launched far more people). Recently, as the Soyuz FG (taking on the name of the crew capsule it is famous for carrying), it had a nine year run as the only rocket able to transport astronauts to the International Space Station, until the Dragon 2 capsule was ready. The current Soyuz 2 versions are distinguished from their predecessors mainly by the fact that they’ve finally thrown out the analog automation circuitry and put in some modern control logic. The FG, which used the old analog system, was kept in service for crewed flights until 2019, when the 2.1a finally took over. The original system was so crude that the rocket’s target orbital inclination could only be set by rotating the entire launch pad on a giant turntable. In the old days it had been known to do things like ignite the upper stage while the rocket was still on the ground, half an hour after an aborted launch. Don’t look down on the FG, though: until its highly publicized launch abort in 2018 where a booster failed to detach cleanly, it had never failed, and in that incident the abort system worked perfectly to save the passengers.


The bottom stage is wrapped with four liquid-fueled side boosters which drop away — a so-called “stage and a half” design. They actually referred to the core part as the second stage — it’s as if the upper stage just had a long thin tube extending downward between the boosters, which are considered the true first stage. The reason they approached it this way is because in those early days, they wanted to avoid the problem of making sure that the upper stage could ignite in midflight. They did not add a proper upper stage above the core until developing the “Vostok” version which launched Gagarin, though the “Luna”, which launched the first lunar probe and got the first look at the far side, had a tiny one. Since then, the R-7 family went through a number of evolutions before finally becoming the Soyuz, some being called the Molniya (Молния), the Polyot (Полёт), and the Vozhkod (Восход).

Each side booster has four nozzles, plus two mini-sized ones on the outer edge for steering, all being part of a single engine. It’s called the RD-107A and was originally made by Kuznetsov (Кузнецова), but they went bust and the factory is now run by NPO Energomash (НПО Энергомаш). Their main business is equipment for power plants, but their V.P. Glushko division makes the engines of a large share of the world’s active rockets, though that share is now decreasing. The RD-107A’s turbine pumps are powered by a separate tank of peroxide, as in the ancestral V-2 engine built by the Nazis. The fuel is refined kerosene (or in some versions, a synthetic substitute), combined with liquid oxygen. Why does each engine have four main nozzles? Because they hadn’t yet gotten the hang of controlling destructive oscillations in a single large one. The central booster’s engine, called the RD-108A, is the same except it has four minis stuck in the corners instead of two. The mini nozzles each pivot on only one axis, so they have to work in pairs.

That’s a total of 32 rocket nozzles ignited at launch... a task which is accomplished by sticking a giant wooden match up each one before starting the fuel pumps. Recently they have worked on using a more modern igniter, but when or if this new ignition system is coming into use is not clear. (Kerosene is difficult to ignite and requires something rather pyrotechnic to get it going — a spark plug won’t work. This is a safety advantage for kerosene over volatile fuels.)

The side boosters taper toward the top, giving the lower part of the rocket a conical outline. The Russian engineers nickname them “markovkas” (carrots). When they peel away at high altitude, they make a pattern in the sky which is called the “Korolev Cross”. That tapered profile is rarely used by anyone other than the Russians, despite some advantages such as lower coefficient of drag. The main disadvantage to a conical shape would be less tank capacity for its weight.

Traditionally, up through the Soyuz 2.1a, the second stage uses an RD-0110 engine, which is a quad nozzle design like the main stage’s RD-108, but smaller and with a preburner instead of peroxide to power the turbine. Like the main engines, it burns kerosene. But in the 2.1b this is replaced with the RD-0124, which looks similar but uses a fully modern staged-combustion cycle for substantially higher specific impulse, and gimbals as a unit so it does not need separate vernier nozzles. This improved engine raised the total payload capacity by fifteen percent. (The new Angara rocket uses a version of this same upper stage engine, and the Irtysh might use another version.) A third stage is optional, and typically one of the “Fregat” (frigate) line, which burns hypergolic fuel.

Historically, Soyuz launches have been quite inexpensive, but lately there have been some sharp increases. Some are muttering about price gouging, but it’s probably due mostly to a rise in the value of the ruble (until 2022 sent it down the toilet), plus a stiff increase in insurance costs as the Russian space program in general has become less reliable, and several troubling incidents occurred for the Soyuz in particular.

Soyuz 2.1v

There have been some efforts to update the Soyuz line. So far, the one concrete result of this effort is the Soyuz 2.1v, a light-duty version which omits the four side boosters and uses a tiny “Volga” upper stage. It has a new version of the core stage which uses a modern engine — the RD-193, which is more efficient and has more thrust than the old RD-108A, and has only one bell. It’s a variant of the RD-191 used by the Angara. Except not yet, because early iterations of the 2.1v are instead using refurbished old Kuznetsov NK-33 engines, which are relics of the failed Soviet moon rocket program. The new engine is now ready but the old ones will be used until the supply runs out. Since it doesn’t gimbal, it has to be augmented with a set of verniers, namely the RD-0110R (which started as a sea-level version of the RD-0110 used on the old version of the upper stage, but adds very wide gimballing to the main nozzles), which also supplies pressurization gases for the tanks. This pseudo-Soyuz is not used very often. At one time it looked like it would gradually grow into a new Soyuz 3 which would replace the whole line, but now that’s looking unlikely. Now it’s apparently just a replacement for the Rokot, which was having production difficulty — at first it was just the Rokot’s backup.

Soyuz 7?

The makers of the R-7 family, RKTs Progress, proposed an all-new rocket called the Soyuz 5, which would be entirely unrelated to the R-7 legacy design. It would be a simple two-stage with no side boosters, with one nozzle on each stage, burning liquid methane instead of kerosene. Later they could expand its capacity by adding extra first stage cores on the sides. By using a simple design and modern fuel, they hoped to come up with something that would compete fairly well on cost with the Falcon 9, and would be cheaper as a replacement for the Soyuz 2 than any iterative evolution of the old design could be.

But this methane-fueled replacement idea was put aside, at least for the shorter term, and the new Soyuz replacement will instead be based on the Zenit, the powerful kerosene-burner which started out as a side booster on the huge Energia, and may return to that role at some indefinite future time when Russia re-enters the heavy lift market. Apparently this Zenit replacement is going to end up using the Soyuz 5 name, which would be odd... but then, it’s been talked about under four different names, so it’s not clear which one is final. This may be why RKTs Progress then floated a Soyuz 7 proposal, which looked like a revival of the methane-fueled Soyuz 5 idea under a different name. But it appears that Putin has personally chosen the Zenit-based approach as the way forward. Not only is the Zenit proven technology, it also has fifty percent more capacity than the Soyuz. The Angara, which is supposed to replace the heavy Proton, is better suited to lighter payloads than any Zenit would be. It replaces the Proton not in terms of payload, but in terms of giving new work to the Kruchinev Center which builds it.

But hold on — since Russia obviously needs to go reusable, and come up with an answer to the Falcon 9, Roscosmos announced in 2020 that they would be building something called the Amur for that job, based on the Soyuz 7 concept though with substantial changes, and that the Progress company will make it. Some sources suggest it might keep the Soyuz 7 name. An addendum to the Angara page has more details on the proposal. So on paper there are three future rocket families, and plenty of work to distribute among spaceflight contractors (the biggies being Progress, Kruchinev, and Energia), but I doubt they will find the money for all of them. Something will have to go.

Soyuz-2.1b: mass 312 t, diam 2.95 m (10.3 m at base), thrust 4150 kN, imp 3.14 km/s, independent turbine (kerosene), payload 8.2 t (2.6%), cost $12M/t?, record for “2” (through end of 2023) 159/1/5 (9 crewed) — for legacy versions about 1656/9/101 (151 crewed)
Records by R-7 version:
Sputnik ’57–’58  3/0/1
Luna ’58–’60 2/0/7
Vostok ’60–’91 146/0/10 (6 crewed)
Molniya ’60–’10 288/0/35
Polyot ’63–’64 2/0/0
Voskhod ’63–’76 276/1/23 (2 crewed)
Soyuz (early) ’66–’76 33/8/2 (19 crewed)
Soyuz-U/U2 ’73–’17 837!/0/22 (68 crewed)
Soyuz-FG ’01–’19 69/0/1 (56 crewed)
— so far: —
Soyuz-2.1a/ST-A ’04– 75/1/2 (9 crewed)
Soyuz-2.1b/ST-B  ’06– 84/0/3
Stage name Block B,V,D,G (≤2.1b) Block A (≤2.1b) Block A (2.1v) Block I (≤2.1a) Block I (2.1b,v) Fregat-M Fregat-MT Volga
Role (pos) count booster (S) ×4 core (1) core (1) upper (2) upper (2) kick (3), opt kick (3), opt kick (3), opt
Diameter (m)   2.68   2.95   2.95   2.66   2.66   3.35   3.80   3.20
Liftoff mass (t) 44.4 99.5 129.0  27.8 27.8  6.6  8.2  1.7
Empty mass (t)  3.8  6.6 10.0  2.4  2.4  1.0  1.1  0.8
Fuel mass (t) 11.3 26.3 ~31     7.6  7.6 ~1.9 ~2.4 ~0.3
Oxidizer mass (t) 27.9 63.8 ~88    17.8 17.8 ~3.7 ~4.7 ~0.6
Fuel type kerosene kerosene kerosene kerosene kerosene UDMH UDMH UDMH
Engine Energomash
NK-33A *
or RD-193
S5.92 l-n
S5.92 l-n
Power cycle independent * independent * staged gas gen staged gas gen gas gen ?
Chamber pres. (bar) 61   60   148    68   157    96   96  
Ox./fuel ratio   2.47   2.47   2.80   2.20   2.60   2.00   2.00   2.0?
Thrust, vac max (kN) 1020     920    1680     298    294    19.9 19.9  2.9
Thrust, SL initial (kN) 840    790    1510    
Spec. imp, vac (km/s)   3.14   3.14   3.25   3.20   3.52   3.27   3.27   3.01
Total imp, vac (t·km/s) 123    283    385    80.5 ~89    21.7 23.2  2.7