Rocket sausages and wieners or the curse of non-universality

The super heavy boosters of the lunar race are beautiful. "Saturn-V" looks so rational and engineering beautiful that one can understand the origin of the argument of the supporters of the "lunar conspiracy" - it seems that such a wonderful rocket would have to fly to this day. But the problem of super-heavy rockets is that they are unsuitable for ordinary space tasks that require a lower payload. In simple terms, you have a Ural truck on which you take fertilizer, bricks or boards to the country a couple of times a year. Will you ride it to the office every day? Theoretically, this is possible, but very inefficient - a powerful engine “eats” dozens of liters of diesel per hundred kilometers, not to mention the associated costs or parking problems. With space, the same thing - “heavy” began to be called rockets with a carrying capacity of twenty tons to a low near-earth orbit, and “super-heavy” are now called a rocket with a carrying capacity of more than 50 tons per NOU. But one should not think that resourceful mankind easily abandoned the dream of getting a universal rocket, which can launch small satellites every month, but once or twice a year go to the Moon or further.

Historical option - remove one step

Here are the three steps of the Saturn V booster:


From left to right: the first stage is the S-IC, the second is the S-II, the third is the S-IVB and the payload (the ship Apollo)

The obvious option is to remove the first, most difficult and powerful stage. But there was a problem - the second stage was designed to launch at high altitude after separation from the first stage, and its engines simply could not tear the rocket from the launch pad. In the Saturn INT-17 variant, it was planned to replace five J-2 engines with seven prospective HG-3 engines. However, the creation of the HG-3 was quickly abandoned, and the developments on this engine in a few years will be used to create the RS-25 engine for the Space Shuttle. In the Saturn INT-18 variant, they wanted to add two or four solid-fuel boosters to the rocket from the Titan launch vehicle. The maximum payload would have reached 66 tons, and in some lighter versions it was intended to remove the third stage S-IVB, and the rocket would consist only of the second stage S-II and solid-fuel boosters. The Saturn INT-19 variant was also supplemented with solid fuel stages, but of a smaller size - it was supposed to use the first stages of Minuteman intercontinental missiles. In the lightest version, 4 TTUs were going to be delivered, in the heaviest version - 12, and four were to be switched on already in flight after dumping eight, launched with S-II engines on the ground. In this embodiment, the capacity of the rocket would be 34 tons.
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From left to right: Saturn INT-17, INT-18, INT-19

The second, less obvious option is to remove the second step. In this case, the main problem was excessive thrust-to-weight ratio of the first stage. A rocket with the first stage without changes would have experienced very serious aerodynamic loads, and the payload would be subject to undesirable overloads. The option of saving five F-1 engines and turning off some of them in flight looked bad — in this case, after only 88 seconds, three engines that had become dead weight would have to be turned off. But if the number of engines was reduced to four, then two of them would have to be turned off at 146 seconds, and the two remaining ones would have been fully refined to 212 seconds. In this embodiment, the rocket would take about 60 tons into low Earth orbit. If you go further and reduce the number of engines to three, then none of them would have to be turned off earlier. Although the payload would have dropped significantly - up to 35 tons.


Saturn INT-20

And the last option is to remove the third step. In a sense, this variant even flew once - instead of the third stage, in 1973, the Skylab orbital station with a mass of 77 tons was developed into space. For another payload, the control system would have to be moved from the third stage to the second, but this would be a very small change. This option received index Saturn INT-21.


Photo launch station Skylab

In the USSR, the situation was more orderly. Initially, the H-1 rocket project wanted to build such modularity - the H-111 rocket should have started from the third stage and would have put five tons into orbit. The H-11 missile was supplemented with the second stage and would output about 20 tons. And the full version, an H-1 rocket with a huge first stage, would have put 90 tons into orbit.


H-111, H-11, H-1

Unfortunately, these interesting projects on both sides of the ocean were waiting for the same fate - for political reasons they were closed. In the United States, they began to create a shuttle, and in the USSR, the new chief designer Glushko was nurturing the idea of ​​his universal rocket, from which Energia later grew.

Modern option - modular steps package

Twenty-first century mainstream has become a different approach. And what if universal rocket modules are made, and to get the necessary load-carrying capacity, to use their different number? They wanted a light missile - they put one module, the middle one - three, the heavy one - five or seven. By changing the upper stages, you can even more flexibly adjust the rocket for a specific payload. In Russia, of course, this is the Angara rocket with a range from two to 25 tons, with possible variants of 35 tons (5 with the upper hydrogen block) and 50 tons (version 7 of the URM, which will require a separate start).


Various options "Hangars"

In addition, as an initiative, TsSKB Progress is developing a project for the Soyuz-5 launch vehicle in variants from 8 to 22.5 tons on methane





In the USA, this is the Delta IV PH with a payload range of 8.5-25.9 tons



Atlas V PH, for which in 2006 they proposed a variant with three blocks. Load capacity in this case will be in the range of 9.7-29.4 tons.


Starts heavy single-block version with side solid fuel boosters

And the Falcon 9 (13 tons) with the Falcon Heavy variant of 53 tons, the first test flight of which moved to 2016.


Single block option

An inquisitive reader will ask me, and where are the "sausages" and "wieners" in the title? The fact is that the version with modular units has its own difficulties. First of all, the fate of the rocket is determined by how well the size of the universal module is chosen. If you make it too small, then the heavy version will be irrational, because the modules will need too much. If you make it too large, you may lose the flexibility of customization for a specific payload. Of the existing rockets, the smallest units of the Angara are only 2.9 meters in diameter. Therefore, the 25-ton variant requires as many as five blocks, while the heavier variants are not yet implemented in metal. Falcon will be the rocket with the biggest blocks, where only three blocks promise as much as 53 tons of payload. It's funny that for a long time on the forums of people keen on astronautics, the idea of ​​a “trizenite” was discussed - a rocket with modular units based on the Zenit launch vehicle. Alas, the life of "Zenith" is actually over, but by its characteristics Falcon is most similar to this option. Guessing about the future of these missiles makes no sense now - too much is unknown to us.
In addition to the global choice of module size, there are other technical challenges. For example, the central module is in fact the second stage and must have an engine capable of being throttled (to change the level of thrust) over a wide range - in order not to be forcedly dropped along with the side blocks. The modulation of fuel from the side modules to the central one, which has not yet been implemented anywhere, will help the modular missiles very much. The side blocks of the first stage can be tried to be reusable and returned, and this is a completely new difficulty.
Now we are waiting for an interesting time - modular rockets are just starting to fly. Let's see how they show themselves in the coming decades.

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