Does Rocketry Work beyond Earth's atmosphere?

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Re: Why Rocketry Doesn't Work in the Vacuum

Postby Boethius on June 25th, 2013, 11:48 am

simonshack wrote:*

Whereas we may conclude that no motion can be applied to a stationary rocket in a vacuum - this old NASA movie seems to 'prove' that humans do indeed get around when exposed to near-zero pressure ! :lol:

Image

From the Science Channel:

SPACESUIT TESTING
"The instantaneous effects on a human when exposed to near-vacuum conditions"


full link: http://www.youtube.com/watch?v=KO8L9tKR4CY


This OSHA report of a death in a vacuum chamber seems to disagree with the NASA video

OSHA GE Accident Report wrote:Employee #1 went into a vacuum chamber testing area to look through the porthole opening in a pressurized vacuum chamber and observe the condition of a nose cone that was being tested. The 12 in. diameter glass in the porthole opening imploded, causing Employee #1's head and one arm to be pulled into the vacuum chamber. He died of crushing head injuries and asphyxia.


So, with the NASA vacuum chamber just open the door and run on in, no wait, no fuss, no problem. Also, there doesn't seem to be any indication of air flowing into the vacuum (re-pressurization), seen either in the technician's clothing or on the hose dangling off to the side. So what happened to the studies that say air flows into the vacuum at 2 km/s? (Note that because of free expansion this fast moving air doesn't create thrust).

With the GE chamber if there's a pressure failure and you're anywhere near the vacuum, you're dead. I tend to think that NASA is more likely to fake a vacuum chamber test than GE is to fake an employee death (Peter Lanza notwithstanding... :P )

Good call on the Ridiculum Absurdum Simon.

http://www.osha.gov/pls/imis/accidentse ... d=14321087
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby Heiwa on June 25th, 2013, 3:54 pm



This is a very strange accident. Outside pressure is abt 1000 hP and inside the vacuum chamber on the other side of the the porthole is vacuum and pressure 0 hP as all or 99% of the air inside has been pumped out. Why the porthole suddenly implodes by being looked at, is not clear. The pressure difference is not big. The porthole should have been tested to manage 1000 kP.
We do not know the volume of the vacuum chamber, but if the port hole glass suddenly bursts the broken glass and external air are sucked into the vacuum chamber . Why a persons solid head attached to a body with arms resting against the chamber should be sucked in is not clear. It sounds like a fairy tale.

Anyway - it is clear that air doesn't like vacuum and fills it. Same with hot rocket engine gases inside a combustion chamber.
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby simonshack on June 25th, 2013, 5:09 pm

^


"ROCKETS DO NOT PUSH AGAINST AIR (1)"

I would like to dedicate this post to those who still embrace the absurd notion that "rockets do not push against air", a trite NASA-promoted quackery - tediously parroted by their many 'apollogists'. As it is, it appears to be the most audacious and aggressively-guarded fallacy ever concocted - in order to uphold in our minds the very feasibility of (outer) space travel. Here it is proclaimed once again, this time in an 'educational' article from major space contractor Northrop Grumman:

Does the rocket push down on the surrounding air?
A common misconception regarding rockets is that they push against the air surrounding them. In fact, rockets work best [!] in a vacuum like outer space. There’s no air or atmosphere in a vacuum. Fortunately for us, we are surrounding by a breathable atmosphere. Unfortunately for the rocket, our atmosphere pushes against its movement upwards.

http://www.northropgrumman.com/CorporateResponsibility/CorporateCitizenship/Education/Documents/pdfs/Rocketry_Guide.pdf


"Unfortunately for the rocket, our atmosphere pushes against its movement upwards".

Well, yes - dear Northrop Grumman 'educators'... : this is, in fact, what is commonly known as aerodynamic drag. It is air resistance exerted on the frontal area of the rocket - PUSHING against it. It is a force - and it increases exponentially with speed. And yes, this pesky force unfortunately slows the rocket's progress through the air. Luckily though, if a rocket is travelling at, say, 3000km/h in the atmosphere - this exponentially increasing air drag will always be far inferior to the formidable power of the rocket thrust (a massive "counter-drag", if you will) which undoubtedly PUSHES against the air below it - with a high-speed 'wall' of burning propellants ejected at 16.000km/h (4,4km/s).


Image


To acknowledge the existence of air drag in front of the rocket while, at the same time, deny the existence of the opposite air displacement exerted by the exhaust plume below it - is an utter contradiction in terms and a crude offense to common sense. If this were to be true (that "rockets do not push against air"), this would mean that the formidable, explosive thrust of a rocket's exhaust plume does not encounter any air resistance - a preposterous and outlandish contention, if there ever was one. Instead, as the NASA quackery goes, we are asked to believe that rockets are propelled solely by the "recoil force" generated by the rapid expulsion of fuel mass from rocket tanks. If this were true, we should all hover above our toilet seats when stricken with explosive diarrhea - yet I doubt that anyone has ever had the (mixed) fortune of experiencing such a thrill.

To be sure, if one were to supply propellant to a tankless rocket from a container anchored on Earth (via a very, very long hose), the rocket would take off just as well - and indeed, much better and faster - given its considerably inferior weight. The truth is that, to uphold the idea that rockets can be niftily propelled in the vacuum of outer space, NASA's propaganda wizards have had no option but to hammer into our brains the absurd notion that rocket jets "do not push against air"! It is now time for this mainstay of NASA's hypnotic brainwashing machine to be flushed out of our skulls.

"Does not push against air" (NASA claims):
Image
http://www.youtube.com/watch?v=uxgMhHOaUSY
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby brianv on June 25th, 2013, 5:47 pm

Rockets work in the vacuum that is some people's minds. Remember the child's game leap-frog? You leap over your playmate by forcing down on him/her with your hands, NASA's rockets leap-frog into space by forcing down on themselves. Ridiculous.
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby Maat on June 26th, 2013, 11:35 pm

brianv wrote:Rockets work in the vacuum that is some people's minds. Remember the child's game leap-frog? You leap over your playmate by forcing down on him/her with your hands, NASA's rockets leap-frog into space by forcing down on themselves. Ridiculous.

________Image
Cartoon-physics-coyote1.png

[For more looney toon physics comparisons: http://www4.ncsu.edu/~gsparson/Physics/forces.html]
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby simonshack on July 3rd, 2013, 8:15 pm

*

BACK TO BASICS

As we go about our rocketry musings ("can rockets work in a vacuum?" - and so forth) I believe we should take a step back and ask ourselves: "Do the space-going rockets we have seen taking off on countless videos over the years even look realistic?" Are the depictions of allegedly space-bound rockets real and legit in the first place? Given the vast amount of fake imagery we have exposed on this forum over the years, this question certainly merits serious and prioritary consideration. To be sure, the various alleged rocket-launching sites (in the Kourou jungle, the Baikonur or Kazakhstan deserts, the Cape Canaveral marshlands, the Vandenberg Air Force Base, etc) are all far-flung locations with extremely limited access to the common person - if any. So do 'spacebound rockets' really ever actually take off from those sites?

Here's a recent ATLAS rocket allegedly being launched from the Vandenberg Air Force Base - on February 11 2013. As we can easily measure and calculate, this ATLAS rocket appears to take off at the incredibly leisurely speed of about 20mph - or 32km/h. That is, in fact the AVERAGE speed of this rocket in its first 100m of flight. This means that, in its first 50meters of flight, it travels even slower than 20mph. Imagine that - and try envisioning the real-world physics involved in maintaining this heavy, 58-meter tall rocket upright - against the forces of gravity. Does this sound plausible to you - even if you are (most probably) not a rocket scientist?

Image
http://www.youtube.com/watch?v=PYwQPBFl6TA
(Please also note the absurdly low/grainy quality of this video purportedly shot this year - in 2013!)

We have all seen military missiles (Tomahawks/Cruise/Scuds, etc) taking off from their launch platforms. Now, I have no problems believing that such deadly weapons of destruction exist and that they are - sadly - very real. Well, they certainly do not take off at slow, bicycle speeds. If you'd put a human being inside them, he/she will immediately be killed by the massive G-forces of the sudden acceleration of these powerful rocket devices. Instead, ever since the ol' Apollo launches shown on TV in the sixties, we have been conditioned to think/accept that bigger rockets ("because of their superior mass", we are told) will take off at initial speeds comparable to that of a running man - or cyclist.

Could these rather absurd, "slow-motion" lift offs we have seen for decades possibly have been dictated by the need to imprint in our minds the plausibility of asstronots surviving such rockets' G-loaded acceleration?

So - ladies and gents - please think about it. Are any of the images depicting NASA-ESA-Russian rocket launches even real?
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby hoi.polloi on July 4th, 2013, 2:57 am

Solid logic and good question as usual, Simon.

The name "Atlas" also denotes someone upholding the Earth. Or is it their inside-joke that the simulated rocket attempts to uphold the simulated model of fake cosmology?
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby totalrecall on July 11th, 2013, 10:43 am

Yeah, I must admit I've also wondered why firework rockets accelerate really fast practically immediately on launch and "space" rockets don't.

Just to play devil's advocate, could it be that space rockets aren't fully on when they are ignited? Is there a fuel restriction at the beginning to try and emulate a slow and more controlled launch? :wacko:

I just found this on an amateur rocket forum:

If your rocket really scoots off of the pad, you can get a way with flying up to the 20 mph limit. But slow-liftoff, long-burn rockets are a bad idea above about 10 mph. (E9 in a Blue Ninja, for example).


http://www.rocketryforum.com/showthread.php?12442-is-there-a-max-wind-speed-you-should-not-launch-you-rocket-in

I'd have to look more deeply into model rockets and see what is what. It does seem to point to some rockets being long-burn while others aren't.
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby Frost on July 11th, 2013, 10:47 pm

Maybe little models can create a tunnel in the air which keeps it straight even with the smaller initial speed, but the big, heavy rocket can't cut the air in half to prevent wobbling about with such a slow launch. The only thing to keep it vertical would be the gases being ejected perfectly evenly. I don't believe it's possible.
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby I, Gestalta on July 11th, 2013, 10:53 pm

Frost wrote:Maybe little models can create a tunnel in the air which keeps it straight even with the smaller initial speed, but the big, heavy rocket can't cut the air in half to prevent wobbling about with such a slow launch. The only thing to keep it vertical would be the gases being ejected perfectly evenly. I don't believe it's possible.


The animation department at SpaceX would tend to disagree!
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby casper on July 20th, 2013, 4:11 am

If I understand this free expansion proposition, it's that the vacuum essentially sucks the exhaust out the back of a rocket too fast and robs it of any forward effect. That would mean a rocket requires back pressure to work correctly, where the exhaust would actually have to do some work in getting to atmospheric. Too high a back pressure, however, and there's no flow, which requires pressure differential. I can imagine sucking the air out of a balloon really fast would prevent it from moving forward without having to hold it back.
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby Heiwa on July 25th, 2013, 5:38 pm

Actually the liquid rocket fuel is burnt and becomes a hot gas that is ejected through a nozzle into the external environment, e.g. the vacuum of space. As the liquid fuel has a mass that becomes a gas with same mass that is ejected from the rocket, the rocket, while losing mass/fuel, will accelerate in the other direction, i.e. why rocketry works everywhere.
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby simonshack on July 25th, 2013, 7:52 pm

Heiwa wrote: (...) i.e. why rocketry works everywhere.


Everywhere?

So why do NASA / ESA rockets proceed at about 20km/h (bicycle speed) in their first 100m of flight, Heiwa? How can that be?
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby Heiwa on July 26th, 2013, 4:48 am

simonshack wrote:
Heiwa wrote: (...) i.e. why rocketry works everywhere.


Everywhere?

So why do NASA / ESA rockets proceed at about 20km/h (bicycle speed) in their first 100m of flight, Heiwa? How can that be?


It is because the rockets accelerate from start velocity 0 km/h when burning fuel, ejecting mass and losing weight. After 100 m flight the velocity is evidently > 0 km/h. Earth gravity tries to pull the rocket back to ground at this stage and that's why the start is slow (and plenty mass is ejected).

In space and away from Earth gravity and when the rocket has a velocity of X m/s, any ejection of rocket fuel/mass in the shape of hot gas, will produce a change in velocity of the rocket (while the rocket's total mass is reduced).
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Re: Why Rocketry Doesn't Work in the Vacuum

Postby simonshack on July 26th, 2013, 8:58 am

Heiwa wrote:
simonshack wrote:
Heiwa wrote: (...) i.e. why rocketry works everywhere.


Everywhere?

So why do NASA / ESA rockets proceed at about 20km/h (bicycle speed) in their first 100m of flight, Heiwa? How can that be?


It is because the rockets accelerate from start velocity 0 km/h when burning fuel, ejecting mass and losing weight. After 100 m flight the velocity is evidently > 0 km/h. Earth gravity tries to pull the rocket back to ground at this stage and that's why the start is slow (and plenty mass is ejected).


1: Have you ever assisted to such a slow-launching rocket personally?

2: Does this rocket built by amateur Steve Eves escape to the 'slow start' rule? If so, why?
Or would you say that this Steve Eves video is fake, while all ESA launch videos are real?
Image
http://www.youtube.com/watch?v=uxgMhHOaUSY
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