[AlphaKilo]

Yes, all you respected Ladies and Gentlemen read it right. I am going to talk about the so-called "Rocket Science"! Don't worry, one doesn't need to be a rocket scientist to understand rocket science.
Lets start with a bit of history lesson.

Go through this video when you have time:

http://topdocumentaryfilms.com/space-race/

So first let me start with this small video: How does a Rocket engine work?

http://www.youtube.com/watch?v=tyq6WSvlB-M

This will be an exact translation,following the sequence as seen in the video.

Translation:
1. Initially, the bottle is filled with water upto the brim and then immersed into a tank.

2. Followed by that the bottle is filled to 2/3rd its capacity with H2 (hydrogen)

3. Remaining 1/3rd is filled with O2.

4. So now a spark/ignition mechanism is placed and once sparks, boom - lift off!
This is the basic principle for the working of the rocket engine(cryogenic - liquid fuelled)

So now, for the next part:

5. The bell shaped dome (see image below) is the exhaust nozzle (in our car terms the silencer! its not silent though nor it suppresses sound! its job is to guide the exploded gases into the atmosphere and generate thrust out of it.(how it does, will be explained in the coming posts).


6. The confused portion above the bell dome is the actual engine! (haathi ke daanth dikhne mein alag aur khaane mein alag - elephant's teeth might look small but are capable of crushing bamboos!).

7. So, now back to the video, the small engine, basically is made up of injectors (565 in number) - these are just for O2 injection into the combustion chamber.

8. These are carefully screwed to the base plate, everything happens inside a clean room to avoid any dust.


9. Once the injectors are screwed onto the base plate they are mounted on the combustion chamber, carefully and precisely.

10. The small copper bullet like things is precision machined to have 142 bores all around its body and this is also screwed to the O2 injectors.

11.The huge copper flower pot like structure is the combustion chamber, which is machined to have groove/cut-outs running along its length vertically all around.

12. These grooves direct the hydrogen into the combustion chamber. In order to prevent gas from leaking, the steel/chromed housing covers the inner copper metal portion.

13. Once the machining is over, the base plate containing the injector is carefully screwed onto this, thus forming the complete engine.

14. Now, the working. The blue gas(oxygen) comes through the huge opening and is injected into the combustion chamber through the nozzles and the hydrogen is pumped from below(lighter than air so rises) through those precisely cut grooves into the injector base plate.

15. Those small copper bullet like struts, act as mixers, mixing o2 and h2 and injecting through further specifically designed pores into the combustion chamber.

16. The middle portion in the combustion chamber houses the spark plug or the ignition mechanism.

so, there you go, Ka-boom and lift-off! but then, there is a catch, one cannot lift off only with the main engines. You need boosters for that initial acceleration to escape the gravity. That boosters are the ones attached along the side. This contains solid propellant (read: diwali crackers!) and are used for only 2 minutes, but you achieve more than 4 kms of altitude within 2 minutes. Mind you once you ignite the solid boosters there is no stopping, therefore, always during launch, the liquid main engine is ignited first and after a few seconds the solid ones are ignited.

Now the first of the game is over. you all know how a rocket motor(its called motors! solid motors and liquid motors ) works. now the next part will be to understand the forces and speeds and different types of orbits available.

Please feel free to ask questions and comment on the quality of the content. If anyone feels, its too high-end, please feel free to say so, I will try to dilute it and if someone feels its too childish, do please feel free to say so, and I will be happy to ask questions and learn more.

[GTO]

Thread moved from the Assembly Line to Shifting Gears. Thanks for sharing!

[roy_libran]

Thanks for sharing. Always understood the concept but never delved into the specific engineering aspects of Rocket construction.
So, I hope, somewhere down the line in this thread, there is a plan on how to integrate the above with an automobile?

[AlphaKilo]

Originally Posted by GTO

Thread moved from the Assembly Line to Shifting Gears. Thanks for sharing!

Thanks GTO for moving it.

Originally Posted by roy_libran

Thanks for sharing. Always understood the concept but never delved into the specific engineering aspects of Rocket construction.
So, I hope, somewhere down the line in this thread, there is a plan on how to integrate the above with an automobile?

Wish granted! Will be done once i am done with the basics.

Now for the next part: I shall be posting this in the evening, but before that I would like to understand somethings from your side:

1. Are there any specific topics that people here wish to discuss about?

2. I will try to keep it as entertaining as possible, but anymore ideas from other space enthusiasts? I know a few are here, and if someone wishes to share this space of contributing with, we can discuss and split topics among ourselves.

Waiting to hear some feedback!

[RS_DEL]

Originally Posted by roy_libran

Thanks for sharing. Always understood the re is a plan on how to integrate the above with an automobile?

There has been work done on turbine powered alternators/battery chargers for Hybrid EVs'. However I am not going to hazard guessing the OP's intent starting this thread. Maybe it is just a Turbine tech for Dummies or maybe there is a specific objective he is working to? Let us wait and see shall we?

[AlphaKilo]

Originally Posted by RS_DEL

There has been work done on turbine powered alternators/battery chargers for Hybrid EVs'. Let us wait and see shall we?

Well, I am not going to talk about Turbines, rather about Rocket powered engines time for some ka-boom not for some woosh woosh whining!

Next part: Different Orbits
Let me give you a small intro into different orbits that are used:

Although the image shows circular orbits, they are not circular in most cases, rather they are mostly elliptical, that is why there is always a farthest point(apogee) and the nearest point(perigee) - same like in elliptical geometry, which many of us learned to forget during our school days. The "gee" in the words means "Earth" in greek, from which the latin is derived. we will talk more on this in the coming days.



This link gives a detailed view on various altitudes and compared with the moon. (image is too big, hence not posting here!) please follow the following link:

http://upload.wikimedia.org/wikipedi...laltitudes.jpg

1. Low Earth Orbit(LEO):

Any where above 100kms(there is actually no fixed boundary where the atmosphere ends and actual space starts! a topic with never ending discussion) so, lets assume 100kms is where atmosphere ends and space starts. So, the low earth orbit, as name suggests means the zone near the earth's upper atmosphere between 100 kms and 2000 kms. The main advantage of this orbit is that the orbital time(time taken to go around the earth once) is between 90 -120 minutes (1.5 hrs to 2 hrs @ ~7.7 km/s - 27,743.8 km/h).

Advantages of this orbit:

1. Easy to reach with normal ICBM(Inter-Continental Ballistic Missiles) which became the rockets(launch vehicles)!.

2. World-wide coverage, able to see any point on earth.(when and how is a different topic, will discuss it when we see about satellites and orbit determination!)

3. Useful for telephonic, navigation, remote-sensing, spy and gravity measurement and atmospheric analysis missions.

Some notable satellites using this orbit:
International space station(s), many RADAR and remote sensing satellites, almost all early manned space missions (SPACELAB, MIR, Gemini, early Apollo and Soyuz programs), most of the Indian Remote sensing and RISAT-1,2, Iridium satellites, Hubble space telescope, chandra X-ray observatory.

Disadvantages:
1. Too low, suffers from drag (thermal and atmosphere).

2. Too low view time over a point on earth

3. make a mistake, and plunge into a suicidal dive into the earth and end result burn up in the atmopshere.

4. needs constant attitude control and orbital corrections

5. Less contact times with the ground station - needs many ground stations spread all over the earth.

2. Medium Earth Orbit(MEO):

The orbit above the Low earth and between the High earth or the Geo-stationary orbit is the medium earth orbit. Though the orbital time period is longer than LEO, but one gets more time over a particular place due to the high altitude.
Advantages:

1. Larger area coverage over the face of the earth visible to the satellite.

2. Longer orbital periods - the object at earth sees the satellite stationary over its position for longer durations - good for navigation receivers.

Most prominent satellites: GPS, GLONASS, Galileo and Telstar 1.

Disadvantage:
1. Needs larger rockets(larger than ones used for LEO)

2. Space debri - blocks access to GEO orbit

3. When the satellite is dead(end of life), the issue of de-orbiting (either to make a suicidal plunge into earth or raise the orbit into graveyard orbit!) problem while coming down: Might have no control and might damage satellites in LEO orbit.
Problem going up into graveyard: blocks GEO transfer and needs fuel and some amount control to reach there in the first place.

3. Geostationary-transfer Orbit(GTO):

Used by satellites intended to be stationed in the Geostationary orbit. This is a sort of intermediate path towards its final destination. Quite often, even recently during the GSAT-10 launch we heard that its on its way and needs couple of days to reach its final orbit. So this is that "on-its way" orbit. This is otherwise also known as a "Hohmann transfer orbit" (click on it to read more on Hohmann transfer! -again saving space and not to bore you with too much text, avoiding the explanation.)

4. Geo-stationary Orbit(GEO):

The final and the highest point any earth-observation satellite could reach.(so far!!) The orbit altitude is around 35000kms above earth's surface(add 6384 kms -earth radius to it!). So this is where one satellite or when a human placed, keeps revolving around the earth, basically, at the same time-period as the earth. What that means? One is stationary above a fixed point. Mostly used by television/telephone/internet transpoding satellites. Its like the object is let afloat over a place, tied by a string, its always there.

Advantages:

1. Ability to cover huge land area(sometimes whole country)

2. Satellite visibility is 24x7(both ways!)

3. Satellite never has eclipse or lack of sunlight (except for some time in summer) due to the inclination of the earth (11°). Hence, satellite has access to solar power 24x7.

4. No complex orbit maneuvers required - read saving costly on-board fuel and there by saving weight(important for launch).

5. Only one ground station is enough to communicate with the satellite.

Disadvantage:
1. reaching the orbit needs a huge rocket or an extra stage(4th or sometimes 5th stage).

2. The transmission needs high power antennas and receivers, due to the distance.

3. The satellite needs to be radiation hardened as it is easily exposed to cosmic radiation and harmful sun's rays. (on the way it crosses Van-Allen belts!)

4. Decomissioning the satellite needs a orbit-raising maneouvre! To be put into the Graveyard orbit, above the normal GEO orbit.

I hope I have covered all the basic aspects of orbits, coming up next, we will read more into how rockets are designed, staging, fuels, shapes and some physics of reaching the space.

The orbits I left are:

1. Molniya

2. Tundra

(Image courtesy: Wikipedia)

Questions??

Edit: Mods, sorry about the huge images. These images explain the concept to the best and are simple, hence used them!

[dhawcash]

Just when i thought T-Bhp is getting a bit monotonous!

I have Loads of questions for you, sir alpha kilo!



1. Are All main rocket engines propelled by liquid Hydrogen and Oxygen? or can they use solid fuels as well? and is all that smoke actually steam? (refferin only to liquid fueled rocket motors) (hydrogen and oxygen combined should produce water vapour) apologies if i sound lame, but im not very good at chemistry. (actually i do understand the concepts but need to brush up before i can get deeper )

2. In LEO Orbits, the satellites need to constantly adjust their position. How do they do it? i mean a normal rocket motor would run out of fuel soon. what is the source of the occasional thrust required to maintain orbit?

3. Err..this one is specially lame. How do rockets change direction? i mean there are no fins (nor would they work in vaccum of space). i guess its done by changing the direction of thrust? (which, again, would be possible within limits, but the mechanism to make that big a** swivel would be pretty complex)

many more questions to come...

[AlphaKilo]

Originally Posted by dhawcash

Just when i thought T-Bhp is getting a bit monotonous!

I have Loads of questions for you, sir alpha kilo!

I know, even I felt the same, thats the inspiration for this thread! (Now I am going to be executed by GTO and all other mods for this!!

-Please, no Sir! Don't make me feel like an uncle! I am just 25. -Nobody is Lame. The lamer the question is, the better one learns. I am too still learning, so please feel free to correct me.

1. Are All main rocket engines propelled by liquid Hydrogen and Oxygen? or can they use solid fuels as well? and is all that smoke actually steam? (refferin only to liquid fueled rocket motors) (hydrogen and oxygen combined should produce water vapour) apologies if i sound lame, but im not very good at chemistry. (actually i do understand the concepts but need to brush up before i can get deeper )

Yes, they are huge steam engines. Not all liquid engines are powered by LH2 and LOX(L-Liquified). There are ones using harmful chemicals like hydrazine too. But LH2, LOX combination produces one of the highest thrust and is safe to operate. Hence, the most preferred engine. (read: Bharat stage/Euro stage norms adhering - well to a certain extent!)

You can use solid fuels, but, with liquid fuels one gets the advantage of re-ignition/restart capability. So if something goes wrong, you just cut-off the fuel supply and shut the engine down - which is not possible in solid motors - once ignited they burn till they run out of fuel supply.

2. In LEO Orbits, the satellites need to constantly adjust their position. How do they do it? i mean a normal rocket motor would run out of fuel soon. what is the source of the occasional thrust required to maintain orbit?

Rockets are basically only launch vehicles.(we will learn more about this in the next post where I will talk about designing and other aspects of rockets). Satellites carry their own propellants(fuel) on-board, use small thrusters(mini-rocket motors) to do orbit corrections.

3. Err..this one is specially lame. How do rockets change direction? i mean there are no fins (nor would they work in vaccum of space). i guess its done by changing the direction of thrust? (which, again, would be possible within limits, but the mechanism to make that big a** swivel would be pretty complex)

Good question! Rockets have their whole engine sitting upon a gimbals(swivel mechanism) that can swing the engine in all directions. Thus varying the force vector's direction and changing direction mid air. All those complex gimbals are computer controlled and they do split second calculations to maintain their direction vector to the pre-set course. Imagine TBHP's (Newton's) second law:

"All objects continue to bla bla bla, unless a moderator interrupts and starts issuing infractions, it continues to bla bla bla."

Same way, due to the moment gained from the rocket, satellites continue their orbit and due to aerodynamic drag, drift away slowly, this is counteracted with the help of thrusts in the opposite direction. This may not necessarily always be achieved from fuelled motors, there are other fuel less methods to do this too!

Enjoy the image: (source)

[vina]

Great thread and nice to have an expert.

So far you have written mainly about huge engines. Lots of such information is available on wikipedia and internet in general an while it helps to have an expert point to it, I would love to hear more on a subject on which information is relatively scarce in generic sources - small rocket applications.

Outside of fireworks, what are the applications of rocket motors and what kind of motors are used? can you put some light on that?

[vivekiny2k]

Thanks Alphakilo.

In my mind space was the place between earth and moon. Now I realize going to moon vs going to space is like going to shanghai vs going to chicago from here. a hell lot of jet lag

[AlphaKilo]

Originally Posted by vina

Great thread and nice to have an expert.

So far you have written mainly about huge engines. Lots of such information is available on wikipedia and internet in general an while it helps to have an expert point to it, I would love to hear more on a subject on which information is relatively scarce in generic sources - small rocket applications.

Outside of fireworks, what are the applications of rocket motors and what kind of motors are used? can you put some light on that?

Good point sir. I will surely write more on this. coming up in this post.

Originally Posted by vivekiny2k

Thanks Alphakilo.

In my mind space was the place between earth and moon. Now I realize going to moon vs going to space is like going to shanghai vs going to chicago from here. a hell lot of jet lag

hehe! sory of yeah!

Next part
So now as promised, we will see more on how a rocket is designed and what are its types:

Basically rockets were initially used by Chinese and very famous Tippu Sultan (the Tippu sultan used was the first missile/artillery attack). But then the real idea behind rockets came up during WW 2, as you rightly guess, under the Nazi regime. Now it makes me wonder, if not for them, how many things would we have missed today?
Well, history apart, the V2 (vengence 2) cruise missile was the first ever official cruise missile which bombed london. This was a liquid fuel propelled rocket (75% ethanol and rest being liquid oxygen used as oxidizer). So basically all the rockets developed by both USA and USSR are based on the V-2 design.(well because they both simply either copied the design using the drawings or used the engineers who worked in it. For eg. US had the treasure of the brain behind all these, Mr. Werner van Braun himself surrendered to the US).
So, basically, rockets are of two types:

1. Liquid propelled rockets,
Liquid propelled rockets are those which uses liquid flammable chemicals as fuels to produce thrust. The early fuel was ethanol, and mostly alcohols and kerosene for their good high inflammability and ability to sustain flame for a longer period. They are huge, smoky, poisonous, risky and produced lots and lots of thrust. But being liquid fuels, did have its own drawback in terms of burning efficiency, that we normally even have with our IC engines.

2. Solid propelled rockets:
Oldest of the fuels used for rocket propulsion. Even said to have been used by the chinese and Indians. Easy to use, safe to handle, produced large thrust within a very short time. Doesnt need complex storage, pumping systems. But the one major disadvantage being, once ignited will burn through without a break! Cannot restart if need shall arise.

Liquid propulsion is mostly preferred as main engines, just for their restart capability, where as always boosters use solid propellants.

So far to the introduction.

Now the next point being sizing and design of rockets themselves.

I hope mods won't mind if I make back to back posts, as this is going to be extremely long post.

[nkrishnap]

Fantastic thread!

Always wondered how the missiles have certain range when they can actually launch a sateliite which way far than the any of the targets on earth. Would you please throw more light on these aspects.

[AlphaKilo]

@nkrish sir, thats very simple:

Missiles or rockets both have a limited range.
1. Difference is the weight of the payload.
2. The amount of force(gravity) that the launch vehicle has to over come.
3. how precise you need to adhere to the orbit.

1. How to design a rocket?

Rocket is designed in stages. Each stage is capable of delivering a certain amount of thrust (read: can lift a certain amount of weight to a certain height!).

2. So, now how do I know how many stages I need to put my satellite into orbit?

Well, that's a trial and error method only. Although, not exactly its trial and error, but one needs to know, how heavy is the satellite and what is the target orbit. So based on this knowledge and by using a empherical formula(who ever needs to know in detail, please ask, I will post it seperately or PM) the numbers of stages necessary is calculated.

3. Hmm, so now I know the number of stages I need, how do I calculate them exact weight?

well, very simple. In order to lift an object with a mass X kg, and overcome the gravity, I need some velocity over time(acceleration). This acceleration defines the type of engine and type of fuel.
Type of engine? - every engine has a specific burn time which is called as "Specific Impulse Isp". Hence for this Isp, the engine delivers the nameplate thrust, this thrust, helps the launcher achieve the required acceleration. Hence, to bring my X kg into Z kms orbit, lets say I need a single stage rocket. what is single stage? see image below:


So this is just one full piece, with the satellite or warhead on the top. When launched this whole piece goes into the orbit, finally ejecting the satellite into its required orbit or making a reentry into the atmosphere over its targe location to deliver its warhead.
In case of a two stage rocket, the payload(our satellite), sits atop the second stage. Understand it similar to seeing a two storeyed building. Two floors on top of one another, with the water tank being on the terrace of the building.(water tank - our satellite). So, the first stage or the ground floor burns upto a certain height and once the fuel is empty, it seperates itself from teh second floor and falls back into the earth/ocean. Exactly at this point, engine/motor mounted in the second stage ignites and continues to thrust the water tank towards space. Once after reaching the specific orbit, the water tank is ejected through a ejection mechanism, and the second stage falls back into the atmosphere, burning up in the upper atmosphere and the watertank/satellite, orbits around the earth happily.

Two stage rocket:

Source:wiki

4. Ok, I have now got a basic idea of launching and designing, but still not understand those strap-on stuff attached to the rocket. What engine does second stage have? or third stage have? (Vina sirs' question: other places where solid boosters are used?)

a. Those strap-on thingies are called strap-on motors or boosters. We have discussed about this in my first post. They use solid propellant(aluminium and some other mixture)

b. Second,thrid or further stages - may either use liquid or solid, depends on the acceleration required, type of orbit, amount of technology available(India is still developing cryogenic engine tech on its own!!), weight of the satellite.

c. Solid propelled stuff, are used as boosters, second/thrid stage, even as apogee kick motors for propelling satellites from GTO into GEO orbit. Mostly used in missile technology where reusability is not a factor to be considered and speed is more important.

Different stages:(source: lecture notes:Prof. Steckemetz)


One important point: In any rocket, the long tube is not the rocket, its just the fuel tank! the engine, as you see in the V-2 image above, stands way at the bottom. So you may ask, how much can I stage a rocket? can I add infinite stages to make it go to deep space, may be next galaxy?

Answer is NO. There is a limit to the scalability. Rockets, I wish, were rubberbands, with unlimited elasticity! But unfortunately we will reach a point where, the weight of the payload to be carried seems neglible when compared with the amount of fuel necessary to bring into its required altitude. This is where rocket engineers stop scaling one single rocket and start to look for more powerful engines or other fuel combinations or even completely other designs.

Further questions??
Next chapter will be basics of satellites.

[im_srini]

Originally Posted by AlphaKilo

I am going to talk about the so-called "Rocket Science" ! Don't worry, one doesn't need to be a rocket scientist to understand rocket science.

Hi AlphaKilo, thanks for starting this thread !

I've always wondered about the shower of sparks that are shot off beneath the Shuttle's main engines on launch (can be seen in the following video about 10 seconds in).

http://www.youtube.com/watch?v=6XSl1whWQso

Is it to ignite the liquid Hydrogen & Oxygen pumped into the engine ?

[AlphaKilo]

Originally Posted by im_srini

Hi AlphaKilo, thanks for starting this thread !

I've always wondered about the shower of sparks that are shot off beneath the Shuttle's main engines on launch

Is it to ignite the liquid Hydrogen & Oxygen pumped into the engine ?

Its called as "Roman Candles" - to burn off any hydrogen formed/settled below the engine which might cause a sudden explosion if not controlled properly.

For more:

http://quest.nasa.gov/qna/questions/...are_the_sparks