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Why Falcon 9FT is a masterpiece
Material posted: Publication date: 06-02-2018
Despite the resounding success of F9 in the commercial market are abled citizens who claim that it is based on the technology of 60 years. I will try to show, by means of open data and simple math that this is absolutely a giant misconception.

On the one hand it is difficult to argue that the whip injector (pintle) to ensure stable operation of the Merlin in a wide range, developed by TRW (which escaped Thomas müller, grab all the technology in the suitcase) in the framework of the lunar program. On the other hand, you notice that the principles of most of the rest of the injectors was developed 10 years earlier. The problem is that the missile is a complex system, the effectiveness of which will need to evaluate the whole thing. And looking at this estimate, we can estimate the technology level that gave a particular result. Formulate stricter -only the analysis of the results allows to assess the technological level.

Falcon 9 is a two-stage rocket (the Falcon Heavy is not going). First and foremost we need to understand the role played by these degrees. Here we help stream the launch of the Intelsat 35e, where there was the landing of the first stage and it worked at maximum capacity. The first step turned off the engine at a speed of 2.3 km/s. Second stage gave the satellite to GTO. The speed of the output gap approximately 10,33 km/s ( 7.8 — 1st space + 2.53). This avoids the aerodynamic and gravitational losses, since almost all of them have got the first stage. And so the first step was dispersed in 2.3, second by 7.73. Obviously, the second step is much more important, but first decided to call contemptuously "booster" because its purpose is to raise the second level higher, where it turns on the vacuum motor and will do all the work. Because then we won't have to consider the first step, and to focus all our attention on the second stage.

The more interesting second step? Foolishly devoured every kilogram second step is lost pounds of load. Because the second stage are true masterpieces of design and weight well show the technological level.

Come on very useful site and write down the weight in the plate. The ratio of the structural mass to the mass of fuel is called the coefficient of structural perfection.

Fuel mass Structural weight The full mass of the stage Design excellence The ratio of empty to full
107,5 Four 111,5 Of 26.88 27.88

The coefficient of structural perfection 26 is a true fantasy! But to appreciate this fantastic, we have to do some calculations. For the convenience of further calculations, note the ratio of the total mass of the stage empty.

Try to understand, don't fool us with that fiction. Take the site of the manufacturer with a maximum load weight of 8 tons and see how the second stage will be able to disperse. Let's use the formula of Tsiolkovsky with the specific impulse 345с:



A very good agreement with the earlier data. Try them with something to compare. The problem is that kerosene PH in the same class as the Falcon is not many and they are all represented by the family of Zenith, a masterpiece of technology of the 80s.

We go to the same useful site the data of the Zenit 3SL and issued the plate:

Fuel mass Structural weight The full mass of the stage Design excellence The ratio of empty to full
81,74 8,31 90,04 Of 9.84 10,84

As you can see, the coefficient of structural perfection is much lower. But we all remember that the Zenith of UI 350C, and we were told that 5 seconds is a lot! Forget about the steering engine of Zenit and will try to calculate using the same formula rate for 8 tons of load. I got it 6.15 km/s. Of course, the comparison is not completely fair, because the step of Falcone and more costly to the output of the first stage. As well as meet new rocket Falconet second stage which has the same total mass 111.5 tons and the coefficient from the Zenith 9.84, MI 350 C. Dividing the total mass at 10.84 find the mass of the empty PH.

Fuel mass Structural weight The full mass of the stage Design excellence The ratio of empty to full
101,21 10,29 111,5 Of 9.84 10,84

This step disperses 8 tons:



...6,4387 km/s. Alas, the GPO will not reach. Will try to put the question differently — what kind of mass it can deliver to GTO? Some tedious calculations show that the speed of palmanovas of 7.77 km/s is achieved at a load of... 1.43 tons. This value can be checked:



Comparison of figures 8 and 1.43 puts the bullet in the issues of "technologies of the 60's". Of course, Zenith is able to display a decent load, but for this he have to use a third stage, which according to Soviet tradition, called the upper stage (the Americans always call it the upper stage and consider how the stage of the rocket. this is clearly seen in the family of the Minotaur). That is why the second stage of the Zenit less, because she has the backs to pull a lot of the upper stage, which is an expensive and complex design, failure is an inexhaustible source of lulz the last 10 years. No wonder flightmanual Falcon says that a smaller number of steps greatly improves the reliability.

The higher weight culture gave the opportunity to create a two-stage kerosene media (i.e., to abandon hydrogen, hi Atlas-5), which covers all the available niches of medium and heavy carrier. And this does not need a closed-loop motor and squeezing the last seconds of specific impulse.

Tags: USA , space

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