Does Rocketry Work beyond Earth's atmosphere?

[simonshack]

*

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?


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 to that of a slow-pedalling 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?

[hoi.polloi]

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?

[totalrecall]

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?

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 ... -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.

[Frost]

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.

[I, Gestalta]

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!

[casper]

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.

[Heiwa]

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.

[simonshack]

(...) 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?

[Heiwa]

(...) 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).

[simonshack]

(...) 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?

http://www.youtube.com/watch?v=uxgMhHOaUSY

[pov603]

I'd posted this question on the Moon Hoax discussion [with an answer from Heiwa which I shall add shortly] and am still unsure as to why, if rockets are capable of leaving the Earth or entering high atmosphere/vacuum, more 'effective' and less cumbersome methods are not used by NA(one)SA(w).

Re: The Moon Hoax
by pov603 on 07 Jan 2013, 15:03

@Heiwa
This is one thing that has puzzled me regarding take off weight.
Why would they launch [any] rockets completely vertically, when even early V1 rockets were launched on sleds/ramps of a shallow angle?
Should that be bogus anyhow, even the BAe Harrier 'Jump Jet' started to be launched from the Aircraft carriers by use of a ramp when it became apparent that there would be a huge operational saving generated on fuel consumption rather than launching 'straight up'.

Re: The Moon Hoax
by Heiwa on 07 Jan 2013, 15:46

@pov603

According NASA/Apollo info the Apollo 11 space ship + rocket third stage was first sent into Earth orbit, i.e. up and then sideways, by the rocket first (with fins) stage and second stage (w/o fins) using plenty, plenty fuel and then ... after 1.5 orbit at 7 500 m/s speed and maybe 400 000 m altitude ... at the right moment - the third stage with Apollo 11 space ship on top was sent off direction Moon burning a lot of more fuel resulting in 11 200 m/s departure speed.
And then Apollo 11 and the empty of fuel third stage rocket separated and went on to the Moon slowed down by Earth gravity most of the way.
The empty third stage missed the Moon with a tight margin, while Apollo 11 had to slow down to get inte Moon orbit ... using 10-11 tons of fuel to reduce speed that was increasing at the end of trip due to Moon gravity pulling it along.

According my simple calculations maybe 40-50-60 tons of fuel was required to slow down ... and that's the first problem (as Apollo 11 didn' carry so much fuel). Asking NASA if it is possible to slow down a 32 ton space craft (ex fuel) from 2 400 to 1 500 m/s speed with a rocket engine using only 10-11 tons fuel results in no answer. So I made the popular web page. It seems NASA then informed their crazy friends at Apollohoax.net which in turn told me in their forum that I was a criminal idiot asking such questions insulting them. And there we are today. I was then banned at Apollohoax.net so I haven't got a clue what is happening there.

[simonshack]

*

Ok, folks - let's get this rocket-power issue out of the way - once and for all !



ARE ROCKETS PROPELLED BY "RECOIL POWER" - as claimed by NASA?

You see, NASA claims that their rockets do NOT push against air ( "at all!") - and this is why they can also operate in the vacuum of space. They claim that their rockets are propelled by "recoil force" - the same force which a bullet exerts on a gun as it gets shot out from its muzzle. But would that force be strong enough to propel a huge, 760.000kg rocket up into the skies?

Here's how Wickedpedia can help us wrap our minds around this intriguing issue:

"A bullet fired from an M16 rifle has approx 1763 Joules of kinetic energy as it leaves the muzzle,
but the recoil energy exerted on the gun is less than 7 Joules."
http://en.wikipedia.org/wiki/Recoil

Right away, we see that the kinetic energy exerted on the rifle is 250 times less than the energy exerted on the bullet :

Weight of M16 RIFLE: 4kg https://en.wikipedia.org/wiki/M16_rifle
Weight of M16 bullet: 3.6g http://www.defencetalk.com/forums/army- ... -a-4686-7/

Let us now build an imaginary, GIANT M16 ROCKET/RIFLE - and see how these energies would compare at a larger scale.
I will use a factor of 190.000 - which brings my standard M16 to the weight of a French "ARIANE 5" rocket (760.000kg):



WEIGHT OF GIANT M16 ROCKET: 4kgX 190.000 = 760.000kg

... whereas a to-scale M16 bullet will weigh:

WEIGHT OF GIANT M16 BULLETS: 3.6gX 190.000 = 684kg

This means that, if our GIANT M16 ROCKET could fire a steady flow of 3 giant bullets each second, it would expel a mass of 684 X 3 =2052kg per second - which is about the same fuel mass allegedly ejected by the ARIANE each second (2000kg) - as claimed by ESA / NASA.

If we now multiply (by our 190.000 factor) the known kinetic energy exerted on an M16 rifle by a bullet exiting its muzzle (about 7 joules) we get (7X190.000= 1.330.000 joules).

Well, 1.330.000 joules is about 1782 hp - slightly less than the horsepower of this special, 1800hp twin-turbo Chevrolet Camaro:


http://www.lsxtv.com/news/video-1800-ho ... -the-dyno/

Let's imagine the power of three of these Camaros exiting the ARIANE rocket nozzle each second : would this be enough to make the French 760.000kg ARIANE ROCKET lift off from the launch pad?



Probably yes. But only at sea level - and up to some 50/70 km altitude - until the air becomes so thin that the bullet-flow pressure (against the surrounding air's pressure) drops below the necessary force to sustain the rocket aloft - as it combats the force of gravity. In other words, all rockets will hit a physical boundary - beyond which they will stop ascending. Yes, this would mean that mankind has no means to exit the atmosphere - and that NASA has fooled us all, ever since its inception.

"Likewise, as elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation. On average, a column of air one square centimeter in cross-section, measured from sea level to the top of the atmosphere, has a mass of about 1.03 kg and weight of about 10.1 N (2.28 lbf)."

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

When studying aeronautics and astronautics in the 1950s, Kármán calculated that above an altitude of roughly 100 km (62 mi), a vehicle would have to fly faster than orbital velocity to derive sufficient aerodynamic lift from the atmosphere to support itself. At this altitude, [100km]the air density is about 1/2200000 the density on the surface.
http://en.wikipedia.org/wiki/Kármán_line

[CitronBleu]

Even though I agree much of the rocket launch footage appears to be staged, I will have to agree with Heiwa that rockets can theoretically work in a vacuum.

By quoting the analogy of the energy produced by firing an M16 bullet, you are in fact validating the idea that a rocket can "push against its own fuel."

Newton's Law states that "for every action there is an equal and opposite reaction." This statement is expressed by the following formula:

M(1) x V(1) = M(2) x V(2)

Where M stands for mass and V stands for velocity.

We are using meters and Kg.

Let's calculate the recoil distance involved in firing an M16 rifle:

Weight of M16 = 4Kg; Weight of M16 bullet = 0.004Kg; velocity of M16 bullet = 950m/s

If we plug in the numbers:

4Kg x V(M16 rifle) = 0.004Kg x 950m/s

So using this formula the recoil, or the velocity of the M16 rifle going in the opposite direction to the bullet = (0.004Kgx950m/s)/4 = 0.95m/s

Thus the bullet is fired 950m/s in one direction, and the M16 rifle "travels" 1m/s in the opposite direction, which seems intuitively about right when considering rifle recoil.

Let's use the same formula to calculate the speed of Ariane 5 one second after lift-off (T=1):

Weight of Ariane 5= 760,000Kg; Fuel mass ejected = 3,925Kg/s; Average exhaust velocity (all 3 engines) =2,415.42m/s *

If I plug the numbers in the formula:

(760,000Kg-4,000) x V(Ariane 5 at T=1) = 4,000Kg/s x 2,400m/s

I get:

V(Ariane 5 at T=1) = 12.7m/s

The Ariane 5 is accelerating at 12.7m per second per second. This acceleration is larger than the effect of gravity (9.8m per second per second), so the rocket is indeed rising.

Just like if I attempt to run faster and faster, or paddle harder and harder, or if my free-moving M16 rifle fired a continuous and steady stream of bullets, my speed will continually increase, as my acceleration is cumulative.

Not only that, but my rocket acceleration will also increase over time as a result of the decrease in my total rocket mass due to fuel consumption:

Let's consider the weight of Ariane 5 at T=120 seconds, right before the two boosters are jettisoned.

M(Ariane 5 at T=120) = 760,000Kg - (120s x 4,000Kg/s) = 280,000Kg

At 120 seconds after launch, Ariane 5 will have total mass 280,000Kg.

Let's plug this mass in our initial formula M(rocket) x V(rocket) = M(Fuel) x V(fuel):

280,000Kg x V(Ariane 5 at T=120) = 4,000Kg/s x 2,400m/s

This gives us:

V(Ariane 5 at T=120) = 34.3 m/s

At time T = 120 seconds, Ariane 5 will be accelerating 34m every second, minus the effects due to gravity and air drag.

Now is the fuel exhaust velocity of the Ariane 5 correct? How does such a large rocket slowly rise and not tumble? I don't know, but on paper rockets can work in a vacuum.

* Data from https://campus.tum.de/tumonline/LV_TX.w ... DocNr=7357

[simonshack]

^
Dear Citronbleu,

Here's a short and simple question which I'd like to submit to ESA (if they actually do take questions, that is) - but maybe you can help me out and double-check my question's pertinence and validity, as I may well just be missing something :

°°°°°°°°°°°

Dear ESA,

According to the pdf linked below (describing the specs of the ARIANE 5 rocket), I read that the main stage of the rocket burns for 535 seconds (or almost 9 minutes):

"The main stage burns continuously for about 535s, and delivers the essential part of the kinetic
energy required to place the payloads into orbit."
http://www.astrium.eads.net/media/docum ... ht-191.pdf

I have also read that the Ariane 5 ejects 2000kg of propellant every second - and that each of the two boosters contains 240 tons solid propellant - for a total of 480tons. Now, since 480tons of propelllant ejected at a rate of 2000kg/s will only last for 4 minutes, what keeps the ARIANE 5 going for the remaining 5 minutes?

***********************

Again, Citronbleu, I may be missing something right now - but please let me know exactly what!

[CitronBleu]

^
Dear Citronbleu,

Here's a short and simple question which I'd like to submit to ESA (if they actually do take questions, that is) - but maybe you can help me out and double-check my question's pertinence and validity, as I may well just be missing something :

°°°°°°°°°°°

Dear ESA,

According to the pdf linked below (describing the specs of the ARIANE 5 rocket), I read that the main stage of the rocket burns for 535 seconds (or almost 9 minutes):

"The main stage burns continuously for about 535s, and delivers the essential part of the kinetic
energy required to place the payloads into orbit."
http://www.astrium.eads.net/media/docum ... ht-191.pdf

I have also read that the Ariane 5 ejects 2000kg of propellant every second - and that each of the two boosters contains 240 tons solid propellant - for a total of 480tons. Now, since 480tons of propelllant ejected at a rate of 2000kg/s will only last for 4 minutes, what keeps the ARIANE 5 going for the remaining 5 minutes?

***********************

Again, Citronbleu, I may be missing something right now - but please let me know exactly what!

Hi Simon,

Each solid-fuel booster ejects approximately 2,000kg of fuel per second. In the link I provided above in my previous post the exact figure is 1,835kg ejected every second by each booster, while at lift-off the main stage engine is ejecting its own liquid fuel at a rate of 255Kg per second.

The two boosters are said to only last a little over two minutes (120s x 4,000Kg = 480,000Kg), and provide 90% of the propulsion, at the end of which they are said to fall back to Earth and propulsion is provided by the main stage only. The numbers are right.