Does Rocketry Work beyond Earth's atmosphere?

[simonshack]

*

40 MILLION HP
The Wondrous Power of Air

I woke up this morning wondering: "how much horsepower would a Porsche Carrera sports car (which is shaped a bit like a rocket plume) need to reach a speed of 16.000km/h (4.4km/s) in our atmosphere?" Remember, that's the velocity at which hydrogen/oxygen propellant is ejected from a rocket nozzle.

To my delight, I found a handy Drag Coefficient/to Horsepower calculator. It basically calculates for you how much horsepower a given car (with a given Cx /aerodynamic drag - and a given weight) would need to reach a given speed. Wonderful! This calculator was just what I was looking for:
http://www.wallaceracing.com/Calculate% ... 0Speed.php

I then looked up the drag coefficient of a Porsche, and found it here : the Cx of a Porsche is 0.3. For the frontal area of the car, I used the figure of 20 Sq/Ft - which I found here. Ok, so it's that of a Chevrolet Corvette - but it should be pretty similar to that of a Porsche. It also approximately matches the stated area of a Space Shuttle main engine nozzle:


http://en.wikipedia.org/wiki/Space_Shuttle_Main_Engine

Then, I looked up the weight of a Porsche Carrera, and found that it is 3230lbs. But I decided to 'cheat' a little, and went with the weight of the larger Porsche Cayenne (4400lbs- or 2000kg) - since it perfectly matches the weight of the fuel mass claimed to be released every second* by large rockets such as Ariane and the Space Shuttle.

*(To be sure, a horsepower unit is defined as a force produced over one second of time. One metric horsepower, for instance, is the power needed to raise a mass of 75 kg against the earth's gravitational force over a distance of one metre in one second).

So, these are the figures I inserted into my wonderful calculator:

Drag coefficient: 0.3 (Cx of Porsche Carrera)
Frontal area of car (think rocket nozzle area): 20Sq/Ft)
Weight of car (think fuel mass ejected per second): 4400Lbs(2000kg)
Velocity of car (rocket exhaust velocity of 4,4km/s): 9941mph (16.000km/h)

Here's what the calculator came up with:



40.239.275 HP - or roughly 40million HP ! Wow! it certainly looks like the REACTIVE FORCE of air, fighting the ACTIVE POWER of a car travelling at hypersonic speeds produces an awful lot of resistance/ counter-power! I honestly didn't think it would amount to as much as 40million HP. But then again, NO Porsche - nor any car - can go as fast as 16.000km/h...
^ NOTE that the rolling resistance (1,516) is absolutely negligible in comparison to the colossal force of AIR. ^



So finally, I decided to look up how much horsepower NASA claims the Space Shuttle engines produce...and... LO AND BEHOLD ! - it isn't far off my above, approximated figure of "40million HP"! Here's from the official NASA website:

"The engines' exhaust is primarily water vapor as the hydrogen and oxygen combine. As they push the Shuttle toward orbit, the engines consume liquid fuel at a rate that would drain an average family swimming pool in under 25 seconds generating over 37 million horsepower."
http://www.nasa.gov/returntoflight/syst ... _SSME.html

Or, if you prefer:

Standing about the same height as the Statue of Liberty but weighing three times as much,
the two white Solid Rocket Boosters ignite in anger and push out a combined 6.6 million pounds of thrust (equivalent to 44 million horsepower.)
http://www.roadandtrack.com/special-rep ... our-ov-105

So I guess we can now tranquilly say - without fear of sounding stupid or ignorant - that rockets do indeed push against air - or rather - air pushes against the rockets to propel them up through our atmosphere. Yet, one mystery remains: NASA claims that their rockets reach speeds of 8km/s - almost DOUBLE the 4.4km/s exhaust velocity. Yet, NASA clearly states that their rockets LOSE efficiency as they reach higher altitudes. They even have a name for it: "UNDEREXPANSION":


Source of original rocket nozzle over/under expansion diagram: http://en.wikipedia.org/wiki/Rocket_engine

Oh well, that's NASA for you I guess... In any case, it should be obvious that when air/atmosphere gradually thins out and eventually goes missing altogether(vacuum), no more counter-force (as of Newton's laws)is available for the rocket to keep ascending. Much like a dolphin jumping out of the sea - and briefly flying before gravity brings it plunging back into its own, denser fluid for which it was 'designed for'. Just like a rocket attempting to leap into the void of space.

****
An interesting article about aerodynamic drag: http://phors.locost7.info/phors06.htm

[simonshack]

Only the Ariane 5 works. So no cute girls are required to wave off the Ariane 5s in videos of the blast offs.

Allright, Heiwa.

So only ESA's Ariane5 works. While NASA has been fooling the world with their bullcrap for half-a-century.

Yeah - makes perfect sense... Vive la France!

[totalrecall]

I just lost a big long post due to letting my reply sit on the computer for too long. Ok, second attempt.

I've just been on holiday for 2 weeks doing nothing so my brain is fried. I left this thread at page 14 and have read up to page 16, so I may have missed something important.

I am with heiwa and lux on this one. If you look at the flyboard video from 05:18 to 05:21, you will see the man attempting to fly up further than the water cable allows. If it hadn't been for the weight of the jet machine and lack of water to pump, the man would have flown up high in the sky.



Secondly, I don't think a rocket pushes against the air underneath it to cause it to rise. A firework rocket has little air under it to push against when it is several meters high, especially compared to the several tons of air pushing down on it from above. Rocket propulsion must use another method.

Perhaps the ultimate questioning should be along the lines of "What is movement?", "What causes movement?", "Is there a common source behind all movement?". These are question about perception and reality and are not for the topic of this thread. It would be interesting to research it nevertheless.

Lastly, we all must be careful when using theory to try and define reality or possible reality. Recently, not related to this topic, I have been looking into why an airplane flies and why light refracts in a denser medium. Surprisingly when delving deep into the subject I found that nobody knows the answer for sure, even physicists. There are plenty of guesses on the physics forums, some good ones IMO, but again nobody really knows.

Observation and experimentation are the only real tools we have for perceiving reality correctly, and this rocket subject obviously doesn't allow that. We know when we do x, y happens, and engineers have developed mathematical formula to predict the outcome based on these past experiences. But maths can't tell us why something happens, nor foolproofly predict the outcome when another variable is involved, such as vacuum as a medium.

Therefore I don't think I will ever be able to know whether a rocket travels in a vacuum due to my own theories on how a rocket may work.

Theory is schmery after all.

[Flabbergasted]

If it hadn't been for the weight of the jet machine and lack of water to pump, the man would have flown up high in the sky.

A firework rocket has little air under it to push against when it is several meters high, especially compared to the several tons of air pushing down on it from above. Rocket propulsion must use another method.

I have been looking into why an airplane flies [...] I found that nobody knows the answer for sure, even physicists.

I've just been on holiday for 2 weeks doing nothing so my brain is fried.

I was going to write something in response, but by your own confession I see it won´t be necessary.

No offense, totalrecall. Your comments on theory vs. perception of reality are interesting.

[Boethius]

Lastly, we all must be careful when using theory to try and define reality or possible reality. Recently, not related to this topic, I have been looking into why an airplane flies and why light refracts in a denser medium. Surprisingly when delving deep into the subject I found that nobody knows the answer for sure, even physicists. There are plenty of guesses on the physics forums, some good ones IMO, but again nobody really knows.

Observation and experimentation are the only real tools we have for perceiving reality correctly, and this rocket subject obviously doesn't allow that. We know when we do x, y happens, and engineers have developed mathematical formula to predict the outcome based on these past experiences. But maths can't tell us why something happens, nor foolproofly predict the outcome when another variable is involved, such as vacuum as a medium.

This is the essence of science. You don't really know until you run the experiment. Until then all you have are hypotheses.

As far as I can see nobody, not even NASA, has ever run a serious space rocket experiment. Where are the zero-gravity vacuum chambers big enough to fly rockets? There's a 17-mile long supercollider but the largest vacuum chamber is 120 feet.

Therefore I don't think I will ever be able to know whether a rocket travels in a vacuum due to my own theories on how a rocket may work.
Theory is schmery after all.

And nobody can ever go out and investigate NASA claims around rockets in the vacuum independently of NASA.

Space science is like a cult run by ancient priests who speak to the Gods in private. We're not supposed to think for ourselves. We only wait until the NASA oracle tells us the great truths divulged only to them. This is not how science, nor modern, information-based, educated society is supposed to function. The goal of education is for us to learn how to figure things out for ourselves; to examine, to evaluate and to reason with the facts and data. What good is that training if, in the end, we can only shut up and believe what we are told with no proof, no solid theory behind it and no way to check the results or repeat their experiments ourselves?

Rocketry is not unique in this regard. Pretty much all the big results in science follow this pattern. Anyone who challenges the status quo is labeled an "idiot" or a "religious nut" which is ironic because science is behaving more and more like a religion based on faith and less and less of a method based on observation.

[totalrecall]

And nobody can ever go out and investigate NASA claims around rockets in the vacuum independently of NASA.

Space science is like a cult run by ancient priests who speak to the Gods in private. We're not supposed to think for ourselves. We only wait until the NASA oracle tells us the great truths divulged only to them. This is not how science, nor modern, information-based, educated society is supposed to function. The goal of education is for us to learn how to figure things out for ourselves; to examine, to evaluate and to reason with the facts and data. What good is that training if, in the end, we can only shut up and believe what we are told with no proof, no solid theory behind it and no way to check the results or repeat their experiments ourselves?

Rocketry is not unique in this regard. Pretty much all the big results in science follow this pattern. Anyone who challenges the status quo is labeled an "idiot" or a "religious nut" which is ironic because science is behaving more and more like a religion based on faith and less and less of a method based on observation.

I couldn't agree more. I'm often finding that the 19th century was the last time experiments were conducted which produced results going against our esteemed priests' doctrines. They locked down science pretty well after that.

This forum is like a renaissance of 19th century reason. We're doing a good job at calling out their bullshit. The next step is doing a few experiments of our own perhaps. Thank goodness for the internet.

[brianv]

And nobody can ever go out and investigate NASA claims around rockets in the vacuum independently of NASA.

Space science is like a cult run by ancient priests who speak to the Gods in private. We're not supposed to think for ourselves. We only wait until the NASA oracle tells us the great truths divulged only to them. This is not how science, nor modern, information-based, educated society is supposed to function. The goal of education is for us to learn how to figure things out for ourselves; to examine, to evaluate and to reason with the facts and data. What good is that training if, in the end, we can only shut up and believe what we are told with no proof, no solid theory behind it and no way to check the results or repeat their experiments ourselves?

Rocketry is not unique in this regard. Pretty much all the big results in science follow this pattern. Anyone who challenges the status quo is labeled an "idiot" or a "religious nut" which is ironic because science is behaving more and more like a religion based on faith and less and less of a method based on observation.

I couldn't agree more. I'm often finding that the 19th century was the last time experiments were conducted which produced results going against our esteemed priests' doctrines. They locked down science pretty well after that.

This forum is like a renaissance of 19th century reason. We're doing a good job at calling out their bullshit. The next step is doing a few experiments of our own perhaps. Thank goodness for the internet.

Who was it wot said : "The art of thinking and reasoning in strict accordance with the limitations and incapacities of human misunderstanding." ?

[iCONOCLAST]

Ambrose Bierce

[brianv]

Ambrose Bierce

Giggle perchance?

edit: BTW The question was a rhetorical one!

[Flabbergasted]

I'm often finding that the 19th century was the last time experiments were conducted which produced results going against our esteemed priests' doctrines. They locked down science pretty well after that.

This forum is like a renaissance of 19th century reason. We're doing a good job at calling out their bullshit. The next step is doing a few experiments of our own perhaps. Thank goodness for the internet.

A topic for another thread, but, yes, I think you are right: around or just after the turn of the century, a number of scientific disciplines were "locked down" through the adoption of paradigms to which all future research would have to conform. Anthropology and archeology are particularly gross examples. These paradigms have since served as "knowledge filters", preventing alternative world views and a lot of solid facts and findings from being evaluated, published and discussed by researchers and laymen alike.

[hoi.polloi]

I thought it might be pertinent to add one more step to Simon's proposed graduation of rocket chamber pressures.

RocketExpansionDiagram2.JPG (46.83 KiB) Viewed 12133 times

In this model, given the role of theoretical free expansion in the void, gases in the combustion chamber cannot even be pushed to the nozzle, since — by virtue of being in vacuum — they are already headed to the nozzle and interacting with themselves at maximum freedom. Once in the vacuum, they would bounce off one another and go in every direction available, forming billowing clouds of uselessly massed pseudo-gas. Since nothing would be preventing the gas from moving, there would probably not even be measurable swirls on the edges of this instant ever-expanding "cloud".

Even liquid reactions that took place in the combustion chamber that resulted in exploding gases would create gas. This gas would instantly be under the laws of free expansion before they reached the nozzle. Perhaps NASA is hoping the cold of outer space will freeze the gas and cause it to be more effective?

Anyway, work being done on the traditional combustion chamber and nozzle is lost.

Only shooting compressed, extremely dense liquid such as mercury, would move the rocket quickly and effectively in space. And then, how would you get that enormous mass of dense material up into space in the first place?

Ergo, is there no present rocket design that satisfies the required efficiencies of being operational in both atmosphere and void according to this free expansion theory? Well ...

I am with heiwa and lux on this one. If you look at the flyboard video from 05:18 to 05:21, you will see the man attempting to fly up further than the water cable allows. If it hadn't been for the weight of the jet machine and lack of water to pump, the man would have flown up high in the sky.

Based on this cheery and optimistic report, perhaps we shouldn't say rocketry is impossible. Maybe we should just say its purpose and functionality should be reconsidered. Water's proven effectiveness according to Heiwa should mean if we pump enough water quickly enough, a rocket that works like the jet board could surpass all previous ineffective and cumbersome models of rocketry. Hell, we could even have geostationary orbiting "satellites" (above places used to rain fail such as England or the Amazon).

rocket_for_outerspace.JPG (30.23 KiB) Viewed 12133 times

[Heiwa]

Water's proven effectiveness according to Heiwa should mean if we pump enough water quickly enough, a rocket that works like the jet board could surpass all previous ineffective and cumbersome models of rocketry.

Not really!
A water jet on a boat just pumps water from the sea and adds some extry energy to the water to create thrust (force) driving the boat.
A propeller (attached to a vehicle) in water or air - when rotated by some engine - creates a thrust (force) to drive the vehicle.
A rocket engine does not pump anything or does not rotate any propeller - it just ejects a mass of hot gases (previously liquid or solid fuel) at high velocity through a nozzle into the environment (gas or vacuum) - which creates the thrust (force) driving the rocket. Doing so the rocket loses mass (the burnt/ejected fuel) and gets lighter and lighter.
I cannot understand that it is so difficult to grasp? Clever USSR rocket and rocket engine designers (assisted by some Germans) managed to build a working model in the 1950's that put a little 80 kg sputnik in very LEO so it crashed a month or so later. USA got nervous and tried to be better. And there we are. It seems we all agree that the French Ariane 5 is the best rocket today (at €150 M a shot to put 16 tons (200 sputniks) in LEO).

[hoi.polloi]

My ridiculous water rocket above is operating on the ridiculous notion of a pump that is so powerful, and a hose so strong, that it can actually blast off 40 kilometers or more into the air and keep an object hovering because that object does not actually require any fuel on board, it just has to support the incredible pressures of this contraption. I was not talking about existing rockets but proposing a new one based on the jet board. Apparently, my sarcasm was lost in the bad drawings; the inherent superiority of two examples of equal work is in the eye of the beholder, I guess.

But surely, you're not disagreeing with me that (by the physics you believe in and have been describing in this topic) ejecting liquid mass at a high enough velocity and volume could do the same work as gas, given appropriate mechanisms to each? And it would also be the same for solid matter?

Or are you now ascribing a special quality to gas in a vacuum that is the opposite of free expansion, whereby gas does more work in a vacuum than any of gas, liquid or solid do in an atmosphere?

I don't think any of our concepts are that difficult to grasp. That's not the problem. The problem is experimental data to prove each of our predictions.

By the way, your political stories are interesting but sound a bit naive to my ear. Perhaps the 'space race' is another topic that needs your particular world view on. But I guess I am of a more jaded generation?

[Heiwa]

My ridiculous water rocket above is operating on the ridiculous notion of a pump that is so powerful, and a hose so strong, that it can actually blast off 40 kilometers or more into the air and keep an object hovering because that object does not actually require any fuel on board, it just has to support the incredible pressures of this contraption. I was not talking about existing rockets but proposing a new one based on the jet board. Apparently, my sarcasm was lost in the bad drawings; the inherent superiority of two examples of equal work is in the eye of the beholder, I guess.

Whatever - pumping water from the sea via a long hose to a rocket ejecting the water back to the sea evidently doesn't provide any thrust/force on the rocket, which will never take off. The thrust of the water ejected is balanced by the forces in the hose between sea/rocket.
The water jet on the sea works because the engine on the boat adds energy to the water scooped up and then ejected producing a thrust.
Evidently the engine driving the vehicle must be attached to the vehicle. But do not forget removing and mooring lines when going off with a water jet.
Compare water hose + fire man holding hose and thrust/force pushing fire man back by water ejected from hose. That force cannot be used to drive the fire man to the fire. Rather the opposite. Or not at all depending on the length of the hose.

When a bomb explodes anywhere and the solid low volume gun powder is transformed into great volumes of hot gases due combustion, the hot gases can be used for many things, e.g. killing people, blowing down houses, blowing up enemy, etc, etc, ... and it works also in vacuum. Same basic principle is used in a rocket engine that sometimes even blow up.

[hoi.polloi]

The water jet on the sea works because the engine on the boat adds energy to the water scooped up and then ejected producing a thrust.
Evidently the engine driving the vehicle must be attached to the vehicle. But do not forget removing and mooring lines when going off with a water jet.

Of course the water is ejected at high volume producing thrust. That's the point of the pump or engine or whatever you want to add energy to the water. Is my English really that incomprehensible to you?

I don't think you can really understand anything I'm saying or else I missed somewhere where you felt attacked and felt the need to re-educate everyone on the most basic premises we've already established. I feel like you are just using every post as an opportunity to rehash the most obvious information instead of trying to sympathize and understand what I'm saying to you. Please, take a break from this thread until you can.

Whatever

Indeed. Dismiss everything I'm saying and talk about whatever is on your mind. Just not in this thread.