space shuttle

[kevdog1245]

I have a question. When a shuttle takes off what gives it the power to lift off the ground?

 

[drwayne]

Chemical reactions in the liquid and solid fueled engines cause ejection of high velocity gases from
the rocket motors.

Now, I am sure that there is more to your question than that, as you could have easily googled on
"how does a rocket work" or the like, and gotten a better, more entertaining answer - so I would
encourage a more specific question that will help get you a better answer.

Wayne

 

[MeteorWayne]

And interestingly, the main engine chemical reaction is one of the most basic; combining hydrogen and oxygen to make water, in VAST quantities. The propellant (Liquid hydrogen and liquid oxyen for the main engines) is consumed at a rate of 5.5 TONS per second.

The SRB (Solid Rocket Boosters), which provide additional thrust for the first2 minutes or so, are a more complex reaction that Dr Rocket would be more qualified to describe.

 

[drwayne]

Understood about the solids...

Tangent alert - there is a good free program out there for looking at some elements of propulsion chemistry
called "propep". You can even find some GUIs for the frontend.

Wayne

 

[DrRocket]

And interestingly, the main engine chemical reaction is one of the most basic; combining hydrogen and oxygen to make water, in VAST quantities. The propellant (Liquid hydrogen and liquid oxyen for the main engines) is consumed at a rate of 5.5 TONS per second.

The SRB (Solid Rocket Boosters), which provide additional thrust for the first2 minutes or so, are a more complex reaction that Dr Rocket would be more qualified to describe.

The solids provide most of the thrust at liftoff. That is their purpose.

Each solid contains about 1.3 million pounds of solid propellant and much more thrust than weight. The thrust-time profile is determined by the burn rate of the propellant and the geometry of the propellant grain, which is very roughly a cylinder with a center hole. There are other additional features, such as internal fins to provide the precise thrust-time curve that is required.

The propellant itself is composed primarily of aluminum (fuel), ammonium perchlorate (oxidizer) and a polymer binder called PBAN (polybutadiene acrylonitrile)). There are some other ingredients to enhance the burn rate, cure the polymer, etc. It burns at between 5000 and 6000 degrees F.

The solids burn for about 2 minutes and then are separated by some small rocket motors designed for that purpose.

The shuttle motors are relatively old technology, as reflected in the PBAN propellant and the steel cases. More modern solid boosters for space launchers use graphite composite cases and HTPB propellant.

Here is a Wiki article on the solids. I do not vouch for its total accuracy, but it gets across the main ideas.
http://en.wikipedia.org/wiki/Space_Shut ... et_Booster

 

[kg]

Each solid contains about 1.3 million pounds of solid propellant.... composed primarily of aluminum (fuel), ammonium perchlorate (oxidizer) and a polymer binder called PBAN (polybutadiene acrylonitrile....

With all that aluminum in that 1.3 million pounds of propellant it kinda begs the question, how may spent 16oz cans of Budwiser would it take to get the space shuttle into orbit and how long would it take a college campus the size of Umass to produce that many?

 

[DrRocket]

[

The aluminum is about 20% of the propellant, so that would be about 260,000 lbs. That is a lot of beer cans (and the aluminum should be small spherical particles). An empty beer can weights about .57 lb so that is about 456,000 cans.

Given the reputation of Umass, a long weekend ought to do the trick.

At LSU that could be accomplished before half-time at any football game. Geaux Tigers !!!

 

[andrew_t1000]

I have a question about intense vibration that the Shuttle SRB's produce.
Is that because they are core burning? It must be one hell of a flame front!

 

[tanstaafl76]

My understanding is that the vibrations are a result the casings themselves resonating as the solid propellant burns from the inside out through the entire length of the booster. Combined with the inability to stop the burn once it has started, I know it would certainly take someone with a lot more guts than I to sit atop one and cross their fingers while they light the candle.

 

[Eman_3]

The one reason I have misgivings about solid rockets is the fact that once they are lit, you have no control. In large solid rockets such as the ones for the shuttle or Aries, the internal cutout is critical.

http://www.teachengineering.org/vie.../lessons/cub_rockets/cub_rockets_lesson04.xml

As the exposed surface burns away, it reveals what is below, and thus the shape and cross-sectional area changes. And if you alter the surface area, you alter the thrust. If you had a clean hole like a donut, the surface area would increase as time goes by, and you would have maximum thrust at end of burn, and least thrust at start of burn. Considering that you want as much grunt as possible to lift off the ground and start gaining speed, maximum thrust is desired at start of burn.

http://www.nasa.gov/mission_pages/constellation/multimedia/12mold_1.html

 

[neutrino78x]

I was reading a book of "hard science fiction" a long time ago, and I recall that it had them rendering nuclear waste safe by blasting it with main engines from the Space Shuttle. Would that really destroy it enough that it would no longer be radioactive (beyond background)? Can shuttle engines produce temperatures approaching that of the surface of the Sun?

 

[neutrino78x]

here's another question, if you built a rocket the same height and diameter as the Saturn V, and put as many Shuttle Main Engines as would fit on the bottom, and used, say, 80% of the remaining height of the rocket to store liquid H2 and O2, could you achieve SSTO that way? If not, how much of the remaining height of the rocket would have to be used for fuel, do you think?

here are some links related to the subject, from Atomic Rockets (I love that web site!!!!! )

Surface to Orbit

Sea Dragon

 

[Eman_3]

The temperature inside the space shuttle main engine is 3,300 degrees C. The surface temperature of the sun is 5,510 °C. The interior of the sun, where all the fission and fusion goes on, is estimated at 13,600,000 Kelvin.

So if you fired an SSME at radioactive waste, all it would do is scatter it around, and would not alter it's nuclear properties.

Currently, the accepted method for chamical rockets is to use multiple stages. The first stage fires, doe sit's job, burns out, and is discarded becaus eonce used it's nothing but dead weight. The second is designed for the altitude and velocity it is to operate in, and so on and so on. The Space Shuttle is actually a three stage rocket.

There are two key points in this system. First, each stage is designed only for it's specific application. For instance, the conditions at sea level are entirely different than at 100,000 meters. Secondly, as each stage is used up, it becomes dead weight that is discarded.

If you attempt a single stage to orbit by using just brute force, it could work, but it would be terribly inefficient. The engines would either work at low altitude but high air pressure, or at high altitude. Either way, it would be inefficient at one portion of it's journey. And you would have to haul the entire vehicle into space. All those tons built in for launch are just there as extra baggage, eating up precious fuel.