Rocket on fire. Delta-IV Heavy - FireBall
The inspiration to write this post about rocket technology came from the most interesting topics about the “imperceptible complexities of rocket technology”. And if I'm not mistaken, the question about the "lighters" in the topics was not considered. I am writing for the first time, perhaps the topic is banal, but it seemed interesting to me.
On June 11, 2016, the Delta-IV Heavy heavy rocket was successfully launched with the Orion9 spacecraft (as part of the NROL-37 mission). Why start this particular rocket? Firstly, because the most powerful active rocket was launched once again, secondly, it was just the 9th launch of Delta Heavy, and thirdly, the Delta Heavy Start is very beautiful and spectacular (low thrust-to-weight ratio, slow ascent through burning clubs hydrogen).
Launch of ILV Delta-IV Heavy NROL-37:
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Although the launch can be considered an ordinary one, even an ordinary routine, but I would single out the launches of this type of missiles, which have their own zest - the so-called Fireball - the flames of flaming hydrogen vapor, through which the rocket starts. Although for the observer it is a highlight, for engineers it is a problem that must be dealt with. And how it happens is written below.
The “problem” (or feature) of the launch of the RS-68 hydrogen engine rockets (on other types the cyclogram may be different, and the effect is also excellent as a result) is as follows:
Before starting the RS-68 engine (with oxygen-hydrogen steam), 5 seconds (T-5) before the PH is removed from the table, fuel (in this case, hydrogen) is fed to the engine lines. This is necessary for cooling down (with colder hydrogen in comparison with liquid oxygen) highways and engine components before starting (to avoid sudden temperature changes on pipelines, valves, etc.). As a result of this procedure, a cloud of hydrogen vapor is formed around the rocket, gradually mixing with air, which can both burn and explode.
Then, after 3 seconds, the liquid oxygen valve opens and the engine starts. At this point, the engine flame ignites the resulting explosive mixture around the rocket and it all starts to blaze. Like that:
Or so:
As a result, the rocket has such a “coal” look:
Of course, even the first missile launches did not lead to malfunctions and the rocket, although charred, successfully left the launch. But even though it looked spectacular, it was quite dangerous and abnormal (as a maximum, there is a danger of a volumetric explosion).
Naturally, this effect was clear before the first launch. Moreover, the Americans have enough experience with hydrogen engines (within the framework of the Space Shuttle with an RS-25 engine). Based on this, there were at least two engineering solutions to reduce the effect of burning hydrogen on the rocket shell.
First , powerful thermal insulation (orange areas on the rocket modules). It works as an insulating material of oxidizer and fuel tanks from external atmospheric heat, as well as protection from burning hydrogen vapors. In some launches, this isolation partially burns when a rocket is flying:
The second necessary solution is the installation of "lighters".
On the launch pad, the so-called lighters - Radial Outward Firing Igniters (ROFIs, or “sparklers”) are mounted. Similar were on the launch platform for the Space Shuttle. True, these lighters do not save from the spectacle of a rocket escaping from the fire: the fact is that their main purpose is to prevent hydrogen vapors from mixing with air (or minimizing the concentration of these vapors), that is, to prevent the formation of an explosive mixture. They cope with this - so far all launches have taken place without explosions.
But still, the problem of severe burning remained and carried the potential threat of thermal insulation and tank shells.
They could reduce the effect of excessive burnout by an elegant and inexpensive engineering solution: launching the engines of PH blocks at different times.
A simplified start-up sequence diagram looks like this: one of the RS-68 engines starts first on the starboard unit (one of the side panels), after 2 seconds the engines on the other blocks start: “port” (the other side bar) and “core” (central). The point is this: the early start of one of the engines leads to a decrease in the release of excess hydrogen into the atmosphere (the lighters are still burned), at the same time the gas jet flowing into the gas duct (venting channel) creates an ejection air flow that runs like a vacuum cleaner, sucking in everything around the table and the rocket. Therefore, with the further launch of the remaining 2-x engines, the total emission of hydrogen vapors decreases and most of it is entrained by the air flow, which flows around the rocket and table elements and leads the excess flame to the gas duct.
This approach made it possible to reduce the effect of a fireball ʻa to a similar one when launching Delta-IV M with one hydrogen engine. And indeed, the latest launches (Orion EFT-1 and yesterday) were held in a "gentle" mode. But nevertheless, the launch of the rocket turns out spectacular and unusual for the eyes of the layman.
Launch of the Delta-IV-H EFT-1 (the first with the start of engines at different times):
For clarity, the photo-statistics of the Delta Hevi launches from the author Jason Davis are given. It is worth noting that the rocket burns differently from different sides. Also, the flue duct at Cape Canaveral has a two-channel scheme, and at Vandenberg there is one channel. This difference can also affect the nature of a burnout (asymmetry when sucking in ambient air).
However, it is worth recalling that such a problem was not only in the Delta. Probably for the first time this problem appeared in the domestic ICBM R-7 (the progenitor of the current Union), which also “suffered” from the effect of burning out vapors (now kerosene and oxygen) due to the long process of starting the first and second stages (more than 10 seconds). And the first launches of missiles of this type also passed through the flame and did not add nerves to engineers. The solution was found in the gas system (although initially it had to be water, but this is a separate story) of ejection, which, before starting the engines, created an air flow in the duct that entrained burning fumes to the side of the gases.
That's how it looked then: R-7 through the flames.
Here is a brief post about some of the complexities of rocket technology. If I liked the material, then I have an idea to write more about some interesting points that accompany the launches of space rockets.
Thanks for attention.
Sources:
1. www.americaspace.com/?p=21832
2. www.planetary.org/blogs/jason-davis/2014/20141126-ula-burning-questions.html
3. kollektsiya.ru/raketi/335-r-7-8k71-dvukhstupenchataya-mezhkontinentalnaya-ballisticheskaya-raketa.html
On June 11, 2016, the Delta-IV Heavy heavy rocket was successfully launched with the Orion9 spacecraft (as part of the NROL-37 mission). Why start this particular rocket? Firstly, because the most powerful active rocket was launched once again, secondly, it was just the 9th launch of Delta Heavy, and thirdly, the Delta Heavy Start is very beautiful and spectacular (low thrust-to-weight ratio, slow ascent through burning clubs hydrogen).
Launch of ILV Delta-IV Heavy NROL-37:
')
Although the launch can be considered an ordinary one, even an ordinary routine, but I would single out the launches of this type of missiles, which have their own zest - the so-called Fireball - the flames of flaming hydrogen vapor, through which the rocket starts. Although for the observer it is a highlight, for engineers it is a problem that must be dealt with. And how it happens is written below.
The “problem” (or feature) of the launch of the RS-68 hydrogen engine rockets (on other types the cyclogram may be different, and the effect is also excellent as a result) is as follows:
Before starting the RS-68 engine (with oxygen-hydrogen steam), 5 seconds (T-5) before the PH is removed from the table, fuel (in this case, hydrogen) is fed to the engine lines. This is necessary for cooling down (with colder hydrogen in comparison with liquid oxygen) highways and engine components before starting (to avoid sudden temperature changes on pipelines, valves, etc.). As a result of this procedure, a cloud of hydrogen vapor is formed around the rocket, gradually mixing with air, which can both burn and explode.
Then, after 3 seconds, the liquid oxygen valve opens and the engine starts. At this point, the engine flame ignites the resulting explosive mixture around the rocket and it all starts to blaze. Like that:
Or so:
As a result, the rocket has such a “coal” look:
Of course, even the first missile launches did not lead to malfunctions and the rocket, although charred, successfully left the launch. But even though it looked spectacular, it was quite dangerous and abnormal (as a maximum, there is a danger of a volumetric explosion).
Naturally, this effect was clear before the first launch. Moreover, the Americans have enough experience with hydrogen engines (within the framework of the Space Shuttle with an RS-25 engine). Based on this, there were at least two engineering solutions to reduce the effect of burning hydrogen on the rocket shell.
First , powerful thermal insulation (orange areas on the rocket modules). It works as an insulating material of oxidizer and fuel tanks from external atmospheric heat, as well as protection from burning hydrogen vapors. In some launches, this isolation partially burns when a rocket is flying:
The second necessary solution is the installation of "lighters".
On the launch pad, the so-called lighters - Radial Outward Firing Igniters (ROFIs, or “sparklers”) are mounted. Similar were on the launch platform for the Space Shuttle. True, these lighters do not save from the spectacle of a rocket escaping from the fire: the fact is that their main purpose is to prevent hydrogen vapors from mixing with air (or minimizing the concentration of these vapors), that is, to prevent the formation of an explosive mixture. They cope with this - so far all launches have taken place without explosions.
But still, the problem of severe burning remained and carried the potential threat of thermal insulation and tank shells.
They could reduce the effect of excessive burnout by an elegant and inexpensive engineering solution: launching the engines of PH blocks at different times.
A simplified start-up sequence diagram looks like this: one of the RS-68 engines starts first on the starboard unit (one of the side panels), after 2 seconds the engines on the other blocks start: “port” (the other side bar) and “core” (central). The point is this: the early start of one of the engines leads to a decrease in the release of excess hydrogen into the atmosphere (the lighters are still burned), at the same time the gas jet flowing into the gas duct (venting channel) creates an ejection air flow that runs like a vacuum cleaner, sucking in everything around the table and the rocket. Therefore, with the further launch of the remaining 2-x engines, the total emission of hydrogen vapors decreases and most of it is entrained by the air flow, which flows around the rocket and table elements and leads the excess flame to the gas duct.
This approach made it possible to reduce the effect of a fireball ʻa to a similar one when launching Delta-IV M with one hydrogen engine. And indeed, the latest launches (Orion EFT-1 and yesterday) were held in a "gentle" mode. But nevertheless, the launch of the rocket turns out spectacular and unusual for the eyes of the layman.
Launch of the Delta-IV-H EFT-1 (the first with the start of engines at different times):
For clarity, the photo-statistics of the Delta Hevi launches from the author Jason Davis are given. It is worth noting that the rocket burns differently from different sides. Also, the flue duct at Cape Canaveral has a two-channel scheme, and at Vandenberg there is one channel. This difference can also affect the nature of a burnout (asymmetry when sucking in ambient air).
However, it is worth recalling that such a problem was not only in the Delta. Probably for the first time this problem appeared in the domestic ICBM R-7 (the progenitor of the current Union), which also “suffered” from the effect of burning out vapors (now kerosene and oxygen) due to the long process of starting the first and second stages (more than 10 seconds). And the first launches of missiles of this type also passed through the flame and did not add nerves to engineers. The solution was found in the gas system (although initially it had to be water, but this is a separate story) of ejection, which, before starting the engines, created an air flow in the duct that entrained burning fumes to the side of the gases.
That's how it looked then: R-7 through the flames.
Here is a brief post about some of the complexities of rocket technology. If I liked the material, then I have an idea to write more about some interesting points that accompany the launches of space rockets.
Thanks for attention.
Sources:
1. www.americaspace.com/?p=21832
2. www.planetary.org/blogs/jason-davis/2014/20141126-ula-burning-questions.html
3. kollektsiya.ru/raketi/335-r-7-8k71-dvukhstupenchataya-mezhkontinentalnaya-ballisticheskaya-raketa.html
Source: https://habr.com/ru/post/395305/
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