Why the Falcon 9FT is a masterpiece
Despite the deafening success of the F9 in the commercial market, there are alternatively gifted citizens who claim that it was built on the technologies of the 60s. I will try to show, using open data and simple mathematics, that this is a completely gigantic delusion.
On the one hand, it is difficult to argue that the pin injector (pintle), which ensures the stable operation of merlin in a wide range, was developed by the famous company TRW (from which Thomas Muller escaped, will catch all the technologies in the suitcase) as part of the lunar program. On the other hand, it can be noted that the principles of most of the remaining injectors were developed 10 years earlier. The problem is that the rocket is a complex system, the effectiveness of which must be assessed entirely. And looking at this assessment, we can estimate the technological level, which gave one or another result. We formulate more strictly - only the analysis of the result allows us to estimate the technological level .
Falcon 9 is a two-stage rocket (we’re not going to talk about Falcon Heavy yet). First of all, we need to figure out what role these stages play. Here we will be helped by the broadcast of the launch of the satellite Intelsat 35e, where there was no landing of the first stage and it worked in maximum mode. The first stage turned off the engine at a speed of 2.3 km / s. The second stage brought the satellite to GPO. The speed of access to the GPO is approximately 10.33 km / s (7.8 - 1st cosmic + 2.53 transitions). It does not take into account the aerodynamic and gravitational losses, since almost all of them went to the first stage. And so - the first step broke up at 2.3, the second at 7.73. Obviously, the second stage is much more important, and the first is usually called contemptuously “booster”, because its purpose is to raise the second degree higher, where the vacuum engine will turn on and do all the work. Therefore, we will not consider the first stage at all, but concentrate all our attention on the second stage .
What is another interesting second stage? Every stupidly devoured kilogram of the second stage is a lost kilogram of load. Therefore, the second stages are genuine masterpieces of weight design and perfectly show the technological level.
Let's go to a very useful site and write down the weight characteristics in the table. The ratio of the mass of the structure to the mass of fuel is called the coefficient of structural perfection.
The coefficient of constructive perfection at 26 is genuine fiction! But in order to appreciate this fantasy, we have to do some calculations. For convenience of further calculations, let us remember the ratio of the total mass of the step to the empty one.
Let's try to understand if we are not fooled by this fiction. Take from the manufacturer's website the maximum load weight of 8 tons and see how much the second stage can overclock it. We use the formula of Tsiolkovsky with a specific impulse of 345s:
It agrees very well with the data presented earlier. Let's try to compare them with anything. The problem is that kerosene PH in the same class with the falcon is not much and they are all represented by the family of Zenith, a masterpiece of technology 80s.
Go to the same useful site for the data Zenith 3SL and write out a sign:
As we see, the coefficient of constructive perfection is much lower. But we all remember that the Zenith UI 350c, and we were told that 5 seconds is a lot! Let's forget about Zenith steering engines and try to calculate the speed for 8 tons using the same formula. I got 6.15 km / s . Of course, the comparison is not entirely fair, because the falcon stage is larger and requires a lot of input for the first stage. Well, therefore, meet the new Falconit rocket, the second stage of which has the same total mass of 111.5 tons and a coefficient from Zenith 9.84, UI 350 s. Dividing the total mass by 10.84, we find the mass of the empty PH.
This stage accelerates 8 tons by:
... 6.4387 km / s. Alas, it will not reach GPO. We will try to put the question differently - and how much mass can it deliver to GPO? Several chore calculations show that a speed equal to 7.77 km / s of the falcon speed is achieved with a load of ... 1.43 tons. This value can be checked:
Comparison of the numbers 8 and 1.43 puts a fat point in questions of "technology from the 60s." Of course, Zenit can take decent workloads, but for this it has to use the third stage, which, according to the Soviet tradition, is called the upper stage (Americans always call it the upper stage and count as a rocket stage, this is clearly seen in the Minotaur family). That is why the second stage of Zenith is less, because it has to drag the hump into a mass of overclocking unit, which is an expensive and complex structure, failures in its work are an inexhaustible source of lulz last 10 years. It is not for nothing that in the falcon flytmanual it is written that a smaller number of steps significantly increases reliability.
It was the highest weight culture that made it possible to create a two-stage kerosene carrier (that is, to give up hydrogen, hi Atlas-5), which covers all the existing niches of medium and heavy media. And for this, a closed-cycle engine and squeezing the last seconds of a specific impulse are not needed.
Upd. Corrected a number of typos and unsuccessful turnovers, thank you all.
On the one hand, it is difficult to argue that the pin injector (pintle), which ensures the stable operation of merlin in a wide range, was developed by the famous company TRW (from which Thomas Muller escaped, will catch all the technologies in the suitcase) as part of the lunar program. On the other hand, it can be noted that the principles of most of the remaining injectors were developed 10 years earlier. The problem is that the rocket is a complex system, the effectiveness of which must be assessed entirely. And looking at this assessment, we can estimate the technological level, which gave one or another result. We formulate more strictly - only the analysis of the result allows us to estimate the technological level .
Falcon 9 is a two-stage rocket (we’re not going to talk about Falcon Heavy yet). First of all, we need to figure out what role these stages play. Here we will be helped by the broadcast of the launch of the satellite Intelsat 35e, where there was no landing of the first stage and it worked in maximum mode. The first stage turned off the engine at a speed of 2.3 km / s. The second stage brought the satellite to GPO. The speed of access to the GPO is approximately 10.33 km / s (7.8 - 1st cosmic + 2.53 transitions). It does not take into account the aerodynamic and gravitational losses, since almost all of them went to the first stage. And so - the first step broke up at 2.3, the second at 7.73. Obviously, the second stage is much more important, and the first is usually called contemptuously “booster”, because its purpose is to raise the second degree higher, where the vacuum engine will turn on and do all the work. Therefore, we will not consider the first stage at all, but concentrate all our attention on the second stage .
What is another interesting second stage? Every stupidly devoured kilogram of the second stage is a lost kilogram of load. Therefore, the second stages are genuine masterpieces of weight design and perfectly show the technological level.
Let's go to a very useful site and write down the weight characteristics in the table. The ratio of the mass of the structure to the mass of fuel is called the coefficient of structural perfection.
| Mass of fuel | Mass of construction | Gross weight | Constructive excellence | Attitude empty to complete |
| 107.5 | four | 111.5 | 26,88 | 27.88 |
The coefficient of constructive perfection at 26 is genuine fiction! But in order to appreciate this fantasy, we have to do some calculations. For convenience of further calculations, let us remember the ratio of the total mass of the step to the empty one.
Let's try to understand if we are not fooled by this fiction. Take from the manufacturer's website the maximum load weight of 8 tons and see how much the second stage can overclock it. We use the formula of Tsiolkovsky with a specific impulse of 345s:
It agrees very well with the data presented earlier. Let's try to compare them with anything. The problem is that kerosene PH in the same class with the falcon is not much and they are all represented by the family of Zenith, a masterpiece of technology 80s.
Go to the same useful site for the data Zenith 3SL and write out a sign:
| Mass of fuel | Mass of construction | Gross weight | Constructive excellence | Attitude empty to complete |
| 81.74 | 8.31 | 90.04 | 9.84 | 10.84 |
As we see, the coefficient of constructive perfection is much lower. But we all remember that the Zenith UI 350c, and we were told that 5 seconds is a lot! Let's forget about Zenith steering engines and try to calculate the speed for 8 tons using the same formula. I got 6.15 km / s . Of course, the comparison is not entirely fair, because the falcon stage is larger and requires a lot of input for the first stage. Well, therefore, meet the new Falconit rocket, the second stage of which has the same total mass of 111.5 tons and a coefficient from Zenith 9.84, UI 350 s. Dividing the total mass by 10.84, we find the mass of the empty PH.
| Mass of fuel | Mass of construction | Gross weight | Constructive excellence | Attitude empty to complete |
| 101.21 | 10.29 | 111.5 | 9.84 | 10.84 |
This stage accelerates 8 tons by:
... 6.4387 km / s. Alas, it will not reach GPO. We will try to put the question differently - and how much mass can it deliver to GPO? Several chore calculations show that a speed equal to 7.77 km / s of the falcon speed is achieved with a load of ... 1.43 tons. This value can be checked:
Comparison of the numbers 8 and 1.43 puts a fat point in questions of "technology from the 60s." Of course, Zenit can take decent workloads, but for this it has to use the third stage, which, according to the Soviet tradition, is called the upper stage (Americans always call it the upper stage and count as a rocket stage, this is clearly seen in the Minotaur family). That is why the second stage of Zenith is less, because it has to drag the hump into a mass of overclocking unit, which is an expensive and complex structure, failures in its work are an inexhaustible source of lulz last 10 years. It is not for nothing that in the falcon flytmanual it is written that a smaller number of steps significantly increases reliability.
It was the highest weight culture that made it possible to create a two-stage kerosene carrier (that is, to give up hydrogen, hi Atlas-5), which covers all the existing niches of medium and heavy media. And for this, a closed-cycle engine and squeezing the last seconds of a specific impulse are not needed.
Upd. Corrected a number of typos and unsuccessful turnovers, thank you all.
Source: https://habr.com/ru/post/410125/