Does Rocketry Work beyond Earth's atmosphere?

[simonshack]

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THE VACUUM THRUST CHALLENGE

TrainPropulsion_01.jpg (38.89 KiB) Viewed 16487 times

Dear Cluesforum members and readers,

I am hereby announcing my proposal for "THE VACUUM THRUST CHALLENGE", an earthly enterprise / experiment which may (or may not) allow NASA, ESA (and the various space agencies of this world) to prove / demonstrate to the public, once and for all, that their space-going rockets work as advertised.

To be sure, ESA (the European Space agency) claims, for instance, that their big "ARIANE 5" rockets (weight: 760.000 kg) will not only take off vertically from the ground, keep accelerating in the atmosphere and reach speeds up to 35.000kmh/ - but also that these speeds will be maintained as they reach the so-called vacuum of space.

Ariane5_launch01.jpg (99.16 KiB) Viewed 16487 times

Let us remind ourselves about a few basic / standard NASA & ESA claims, which can roughly be transcribed as follows:

-"Rockets do not push against air. Atmospheric pressure is of no consequence to the ascent of rockets. What propels them is the fuel mass being ejected downwards and out of the engine nozzle - thus exerting an upwards, opposite & equal force / reaction (as of Newton's 3d law) against the rocket itself or, more precisely, against the top of their combustion chambers."
-"Rockets are actually more efficient in the vacuum of space (where aerodynamic drag drops to zero)".
-"Rockets maneuver at will in the vacuum of space thanks to smaller, directional rockets (Vernier thrusters)."


So, with the above statements in mind, I have designed the below experimental contraption. It is an Ariane 5 rocket whose three nozzles are attached (via three valves) onto a standard railroad gas tank car. Instead of gas, it 'contains' vacuum. The objective of the experiment is, of course, to verify whether this contraption will be propelled forward, once the valves are opened - and, simultaneously, the rocket engines are fired:

TrainPropulsion_01.jpg (38.89 KiB) Viewed 16487 times

I will now only half-jokingly suggest that this experiment is well within feasibility. See, if everyone of our approx 1400 Cluesforum members chips in with a small contribution, we might well raise the budget needed to buy / rent an old railroad gas tank. As for the ESA rocket, I will do my best to lobby / convince the folks at ESA-Italy (whose offices just happen to be down the road from my house) to provide us with an old Ariane rocket...

Hey, we may then recoup our monies / investment by staging a public event where people can place their bets as to exactly WHAT will happen!

In any case, the gambling box office is already open: place your bets! What do YOU think will happen ?

[Flabbergasted]

I don´t see the point in the experiment. The moment the rocket engines are started, the tank will cease to be a "vacuum tank". In fact, it makes no difference what is or isn´t in the tank to begin with. It will explode and the rocket will ram into the nearest obstacle, killing 11 scientists.

The whole point of "space vacuum" is that it is "infinite". No gas or surface to interact with. No transfer of force between the rocket and the environment. No propulsion.

[queuebert]

In the thread One thing no one can disprove... at the Living Moon forum "Logos" makes the same case presented in this thread, namely that rockets won't work in a vacuum, starting on page 4:

http://www.thelivingmoon.com/forum1/ind ... ic=7474.45

As could be expected, one finds the usual (calculated?) obtuseness, non-replys and going-in-circles goofiness. It's hard to tell whether it's genuine misunderstanding or misdirection--probably both.

Anyhow, I wonder if the PowersThatBe (PTB) really need a lot of shills or if the public mostly does a sufficient job of thought policing itself, such that merely having a few operatives in key positions as "sheepherders" is enough to keep the people spellbound.

[Pilgrim]

I don´t see the point in the experiment. The moment the rocket engines are started, the tank will cease to be a "vacuum tank". In fact, it makes no difference what is or isn´t in the tank to begin with. It will explode and the rocket will ram into the nearest obstacle, killing 11 scientists.

The whole point of "space vacuum" is that it is "infinite". No gas or surface to interact with. No transfer of force between the rocket and the environment. No propulsion.

I guess the question is, in the micro second to fill the tank would any thrust be produced, once it's at equilibrium with the same pressure as the combustion chamber then (assuming for the sake of argument it does not explode) it will go nowhere but according to NASA and their apologetics some thrust should be produced even if for a micro second before the tank fills. Assume a much larger vacuum tank, perhaps a train of a thousand such vacuum tanks all connected.
The experiment could be done on a much smaller scale of course using a very small amateur rocket against a large tank of vacuum or even a firework rocket.

[Flabbergasted]

The experiment could be done on a much smaller scale of course using a very small amateur rocket against a large tank of vacuum or even a firework rocket.

No, it could not, because nobody would expect a tiny firework rocket to tow an enormous tank.

When I said "No gas or surface to interact with" I was including the internal walls of the tank and the tracks on which the contraption is supposed to run.

There truly is no way to physically simulate conditions of "space travel". All we have is physics and computer models.

[Cobra Commander]

I don´t see the point in the experiment. The moment the rocket engines are started, the tank will cease to be a "vacuum tank". In fact, it makes no difference what is or isn´t in the tank to begin with. It will explode and the rocket will ram into the nearest obstacle, killing 11 scientists.

The whole point of "space vacuum" is that it is "infinite". No gas or surface to interact with. No transfer of force between the rocket and the environment. No propulsion.

Ha! You got that wrong. It would reportedly kill 9 scientists, with 11 injured.

In all seriousness though, if you guys could ever figure out how to make that experiment work, I would be able to get us a discount on a railroad gas tank car, since I have a lot of family in the railroad industry. That being said, it still wouldn't be cheap, and you can bet your ass NASA would do everything in their power to shut us down.

[Selene]

full link: http://www.youtube.com/watch?v=WLJpOAl2RRM

Pretty funny simple video where a British guy explains what process he (and as far as I understand also the others including me in this topic) thinks rockets move as opposed to the NASal Propaganda "Physics".

Simple experiment with a balloon car shows the NASagonising "explanation" doesn't hold.

Selene

Knowledge is the sure and undoubted resolution by experiment of all opinions concerning the truth....Experiment is manifest demonstration of the truth, and resolution the putting away of doubt. We cannot be resolved of any doubt save by experiment, and therefore is no better way to make it than on ourselves. Let us therefore verify what we have said above concerning the truth, beginning with ourselves.
Gerhard Dorn (c. 1530-1584)

[pmb]

Someone told me about this forum and thread when they asked about thrust and I provided an answer. I was told that many, if not all, of the people in this thread assert that Newton's third law can't be used to show that a rocket engine works in a vacuum. May I ask those of you with this opinion why you think that?

I also understand that everyone rejects the notion that rockets have never been put into "space" (i.e. the vacuum above the Earth's atmosphere) because you hold that NASA has been lying to everyone all these decades about rocket engines. What evidence do you have to support that position? Since there were close to 400,000 scientist, engineers etc. who worked on the Apollo project in one way or another do you also hold that those 400,000 people have been lying all these years as well?

Since its very easy to show that a rocket engine works in a vacuum has anyone ever tried it? I.e. have you ever tried to build a vacuum chamber and fired a rocket engine in the vacuum chamber? Since the rocket engine would have to be small due to the large forces of pressure on such a chamber for large chambers one would have to use a very small engine. One could also model it using something other than a gas such as a chamber firing rubber pellets.

Have you considered that anybody who could prove that you were right experimentally would win a Nobel prize, which is about $1,000,000 if I recall correctly. That's a strong motivation for those with a large vacuum chamber at their place of business to try it. I know I would.

Since things like Direct TV works by satellites and you need a satellite dish in your yard pointing at it in its geostationary position in space, how did it get there?

When private corporations launch a rocket, where does it go if not into space? It should land and crash, right? Why has that never been seen? We all saw the results of it when Challenger crashed. The same thing would happen after it passed out of visual range. Has any of you ever thought of buying cheap radar equipment and tracking such a rocket launch?

How did the mirrors that are on the moon that we bounce laser beams off of get there?

Last question: Are you folks open to hearing the standard textbook derivation of the rocket equation? If you've already seen the derivation and claim that it's wrong then can you please show me the post in which that was done? I'm assuming that everyone here has an open mind, correct? I can tell you that I do. I had to in order to become a physicist. One has to in order to grasp quantum mechanics and relativity.

Thanks everyone. I appr

[Selene]

Hi Pete, welcome to Cluesforum. Have you read quite a bit before registering?

On satellites ("geostationary" and others) there's a separate thread where you find info on how to obtain the huge amounts of satellite data and signals (including your DirectTV) we receive on Earth.

As a physicist you also should know one doesn't need a 50x50 cm mirror to bounce back signals (radio waves, lasers or sunlight) from the surface of the Moon; the celestial body itself reflects signals easily, otherwise they wouldn't be able to do so before the Apollo "moon" missions (1963 the Soviets did it and radio wave bouncing was done already in 1946 (!) and you wouldn't be able to see a thing at nights with (full) Moonlight...

On the rockets in 'space', apart from purely mechanical physics you have a chemical-physical challenge due to not only the Pressure problem (the supposed vaccuum) but more importantly a Temperature problem. See for elaboration my first post in this topic.

As a physicist you know that material properties are highly T-dependent, so a "rocket" in "space" would have the problem that ~50% of the surface (sun-lit) suffers from very high T's (due to radiation) and the other half or even more of the "rocket" would suffer near-zero T's.

Take the thermal conductivity for instance. Could you as physical expert make a calculation on how this works?

50% aluminium rocket surface @ -let's say- +270 C and the other part at -NASA-claimed- -270 C, or some mere 3 K!

What effect should those extreme conditions have on the rocket and everything inside it, you think?

I really look forward to your physical explanation Pete.

Best of luck and thank you in advance for your contributions,

Selene

[Selene]

Professor Pete, specialised expert in a field of relative relativity, I answer in a separate post because quoting doesn't work well on this smartphone...

"Rude comments"? Can you point out where I've been rude? I may be demanding, but that's not rude and only logical after your own claims and call for quantity.

I simply asked for some basic physical explanations in your own words. I am not (interested in) discussing with Wikipedia and yes, I know how to look up stuff there.

You were the one presenting yourself as an educator, as someone who is used to explain relatively advanced and hard subjects in an easy-to-grasp way. Using sketches, equations and simple language to bring across a point you think you have.

On top of the pretty ridiculous hints that "Apollo was real and they placed a mirror on the Moon", your understanding of satellites and their data and more things quoted by Flabbergasted, it was you and only you who started with the Mickey Mouse magical words "heat shield" that would "solve the problem of the extreme T differences and thus very high heat flow from very hot to stone cold". You really want me to believe you I suppose (otherwise starting a discussion would be a bit useless) but give no explanation whatsoever. While you complain about the lack of quantitative content on a forum you just "skimmed", you seem to refrain from providing that quantitative reflections (pun intended) yourself and refer to Wickedpedia instead.

Do you do that in your lessons too? "Hey student with a critical remark, here you have the collection of human wisdom called Whiskypedia, I will not use this whiteboard behind me, you can just look up what you want to know"...?

Then please don't be surprised I claim my education money back, ok? I'd rather spend it on an Aldrin puppet or cardboard LEM, if you don't mind.

In short; you claim a lot but seem impossible to back up the claims with the quantitative explanations that you claim to care about so much....

Coming back to Simons post; what about some quantitative work on your own words Simon quotes from your email? I am all ears and as I recall well it was your motivation to join here in the first place?

Some progress, and not leaving us in the cold dark space?

Selene

PS: I agree with the others. While English is my third language, it should be your first... My English is far from perfect but the numerous mistakes you made in just a few posts don't really convince me you're a US American. I cannot change that; only you can do that...

[hoi.polloi]

Well, pmb, you didn't bother to finish your post, but I guess we are meant to assume you were about to type something about what you appreciate about us. It would have been a welcome comment since you entered waving your finger at everyone.

I for one would love to hear what you have to say about rocket formulas that take into account atmospheric resistance and pressure and so on. Please lay it on us. You don't have to read all threads on the entire forum to get a picture of the problems with rocketry. You can simply read this thread. The one you are commenting on. (If you had actually read it in instead of just bursting on the scene making accusations, you would see that there have already been attempts to explain and design vacuum experiments. And you would know that the experiments that you imply as being authoritative are actually very ineffectual, and in quite an amateur way at that.)

To summarize for those wishing to catch up with pmb's out-of-context complaints, the "free expansion of gas in a vacuum" (as Boethius posited) is one explanation for gaseous rocket fuels (which already conceptually would have to be shown to be capable of igniting adequately) escaping an implement with no work being done on the implement. In short, bursts of spray would not navigate anything. Since the bursts are also said to occur in the near perfect void of outer space, this would be nigh impossible to test on Earth, especially with the rocket models of several stories (heh, stories) in height that we are shown. Therefore, the enigma of the claims of NASA and ESA and other so-called "space explorers" is that their formulas cannot actually be tested without a great deal of money and/or access to incredibly special privileges. Many of those privileges are, in turn, actually also not possible for the average person to test, making even the claims of the science of "space explorers" as dubious as the claims made without adequate scientific explanation.

By the way, some mathematical proofs are not very good explanations about how something works. Telling us, for example, that a telescope's ability to read a stop sign from 12 miles away is derived from the formula for the arbitrary resolution of any device with a resolution, does not answer the question of how the resolution is achieved.

A simpler way of putting it is: please do not dodge questions by forwarding us to a different question that apparently grants access to the knowledge you claim there is. Especially when it does not actually do so but only claims to. Use and respect and answer respectfully the questions asked.

Moving on, another issue with rocketry is the lack of strong visual evidence to replace all the fake footage. Since many of the rocket launch videos appear to be manipulated imagery, and people who search for it cannot seem to come up with reliable, undoctored evidence of an actual rocket launch to space, many people have also come to ask questions about why space-faring rockets cannot be filmed or video taped presuming they were real.

As for topics not having to do with rocketry, and for which you can actually speak on with any expertise or speciality/specialty, I have made this special thread for you. Since you seem content to enlighten us about so many topics, feel free to change topics quickly and do not be afraid to try to convince people that your knowledge of outer space is based on a solid foundation (excepting of course if your only argument will be that many people agree with you so explanations are unnecessary) : http://cluesforum.info/viewtopic.php?f=23&t=1812

As for being open minded, I am not sure what you mean exactly. I think we may use those words differently. To us, open minded means lending some brain waves to hard questions and working on answering them. To you, it might mean accepting (and widely promoting) the most well-funded looking answer. No offense or judgment is meant at all in this statement. I am simply observing that that may be the case based on your posts so far.

Please, proceed with your rocket explanation using your own words on how we're all wrong in doubting that they achieve what NASA claims. Text book explanations are welcome, as long as you yourself are prepared to demonstrate your understanding of any given text. Useful understanding of a text (as opposed to the understanding of an insane individual or someone with a disabling mental handicap) would be qualified as something which you can explain to others in your own words so that they can understand it and confidently know that they understand it.

If you used to be able to explain it, but — due to injury — you can now no longer explain it, I am afraid nobody will find much use for that. And it would be a pretty convenient excuse to hide behind, for someone who just wanted to berate innocent researchers who are genuinely curious about the world they inhabit.

[simonshack]

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This is the forum mentioned by pmb, "The Naked Scientists" - where they have a (now locked) 9-page thread titled:

"Topic: thrust does not work in space": http://www.thenakedscientists.com/forum ... #msg449749

Our new member Pmb (who I assume is "PmbPhy" on that forum) seems to have been quite active on that thread - and has worked hard to share his views about physics and how rocketry would work in space. Here are some interesting excerpts of pmb's reasonings :

"(...) Sit down on the skate board and make sure its on a very flat smooth surface. Make sure that you and the skateboard are at rest before you throw the stone. Then throw the stone as hard as you possibly can parallel to the ground. The exact moment the rock leaves your hands the whole system of thrower + skateboard will recoil. You and skateboard won't wait until the rock see if there's something to hit because the rock and skateboard doesn't think."

"The easiest way to understanding this is to look at the simplest situation. In a vacuum, think of a coin with a firecracker next to it right above its flat side. When the firecracker detonates the fragments smash against the coin and bounce off of it. Newton's third law tells us that the coin will rebound. You can look at a rocket engine as a controlled continuous explosion. This has nothing to do with the presence of an atmosphere. In fact it doesn't work as well with an atmosphere present."

[in response to a Naked Scientist forum member who doubts that rockets would work in the void of space]:
"The example I myself gave to him is the fact that in order for the space shuttle to achieve orbit the thrust of the rocket's engine must work in the absence of an atmosphere. Otherwise it wouldn't work. When the space shuttle wants to return to earth it must ignite the engines so that the thrust will slow it down enough to enter the earth's atmosphere".

Impeccable logic, n'est-ce-pas? Let's take a deep breath - and read that again: "(...)for the space shuttle to achieve orbit the thrust of the rocket's engine must work in the absence of an atmosphere. Otherwise it wouldn't work." In other words: it HAS to work, otherwise it WOULDN'T work, you see?

Something I have noticed in various forums discussing the subject of space propulsion is exemplified by this other comment - by "alancalverd", a supporter of PmbPhy's arguments on the Naked Scientists forum. At one point, alancalverd says :

"Have you ever fired a rifle? The recoil force is exactly the same whether you fire it under water or in air. Recoil force is independent of the surrounding medium. Conservation of momentum is demonstrated in many ways: billiard balls, "Newton's Cradle", spinning tops and skaters.... and in no case is there any requirement of "something to push against". Rockets work by conservation of momentum, nothing else. You chuck stuff out of the back and the rocket moves forward so that the net change in momentum is zero."

In fact, I have often seen this 'bullet-recoil' argument being brought up by folks convinced by the feasibility of space propulsion - and I remember reading on some other forum that burning rocket fuel basically works like the flow of bullets fired out of a machine gun: what propels a spacecraft, it is argued, is the mass of the exploding fuel recoiling against the combustion chamber coupled with the momentum of the exhausts rapidly expelled out of the nozzle, yet - ( and this is clearly / strongly argued ) - these same, supersonic exhausts do no work whatsoever as they impact the atmosphere (not even at sea-level). As it is, the consensus among these people seems to be that rockets work exclusively by 'recoil effect' and 'rapid mass / momentum transfer' (excuse my figurative layman's terminology) - and that no analogy whatsoever can be made between a jet engine and a rocket engine - as far as the very nature of their propulsion forces is concerned. I believe the following sentence (that I once read and saved in my 'space notebook') correctly sums up their basic theory: "If you know the rocket's mass, the amount of fuel burnt per second and the exhaust velocity then you can calculate the rocket's gain in velocity per second interval which is also therefore equal to its acceleration."

Fair enough. So with this theory in mind, I have decided to set up an experiment. On the beach.


THE MIDGET-SOLDIER ROCKET PROJECT

I have this midget soldier (my little Italian trooper only weighs in at 50kg or so) that I wish to launch and briefly propel upwards (in the atmosphere, that is - am not even thinking of reaching the 'vacuum' of space for now!). Looking around for the 'world's fastest machine gun' I have also found this remarkable Russian machine gun, the "SKHAS Ultra" used in WWII - capable of firing 3000 (yes, three-thousand) rounds per minute - i.e. 50 rounds per second.

ShKAS machine gun specifications: https://en.wikipedia.org/wiki/ShKAS_machine_gun




Now, I already know the basic specifications of the Ariane 5 rocket - having already looked into it / discussed in this thread some time ago:


Weight of Ariane 5 rocket: 760.000 kg
Mass of fuel ejected per second : 2000 kg / s
Ratio of fuel-weight expelled per second / vs vessel weight: 1/380
(in other words, 0.263 % of total vessel weight is expelled every second)
Exhaust velocity (at sea level) : 2749 m/s

As compared to :

Weight of midget soldier + machine gun + 650 rounds of ammunition: 50+10+40 = 100 kg
Mass of 50 rounds (of 24g each) fired per second : 1.2 kg
Ratio of rounds expelled each second / vs soldier+gun assembly: 1/83
(in other words, 1.2 % of total vessel weight is expelled every second)
Muzzle exit velocity : 825 m/s


So, let's see: my 'vessel' (i.e. the midget soldier and his machine gun & ammunition) is :

About 4.5 X superior (more efficient) in terms of mass expelled per second / vs vessel weight
About 3.3 X times inferior (slower) in terms of 'muzzle / exhaust exit velocity'.

By the looks of it - and since my mass-ejected-per-second-ratio is 4.5 X superior to that of the Ariane rocket - this looks promising, yet I'm a bit worried that my exit velocity (of my 'rocket fuel' - i.e. the bullets of my machine gun) is inferior to the Ariane rocket's.

However, not being a physicist, I'm currently stuck at a more profound / momentous question:

Will my midget soldier take off at all - and briefly soar up in the skies? If not - WHY NOT?

Hopefully, Pete (our new member 'pmb') or any other helpful physicist will be able to help me out here. Anyone?

[Farcevalue]

Simon, aside from your midget soldier rocket being propelled by the mass ejection of shells (perhaps plausible, however marginally, when he is already in the vacuum) he also has to escape the gravitational field of the earth. According to Wickipedia, the ShKAS machine gun fires cartridges with muzzle velocity of a paltry 2710 ft/s, as opposed to, say a .220 Swift Cartridge that can exceed 4000 ft/s (commonly cited as the fastest available production model cartridge).

Regardless, both of these speeds are still quite short of the escape velocity required to leave the gravitational field of earth which according to NASA, is 36,960 ft/s. (http://www.nasa.gov/audience/foreducato ... ty_prt.htm)

At some point after your midget soldier rocket leaves the ground, he will have to gain more than 13 times the rate of speed his ammo is leaving the barrel of his "propulsion system".

(Incidentally, regarding the Apollo rockets, it just me or is the idea of executing the untested maneuver of the untethering, rotation and re-attachment of of the command module pictured below at the speed of 36,960 ft/s a tad fanciful?)



Anyway, last month there was a bit of buzz about the possibility of new unmanned "hyper sonic" rockets changing the nature of warfare by the year 2040, the projected date of the perfection of these projectiles that can reach the currently unprecedented (except when talking about Apollo rockets, that is) 5573 ft/s:

http://www.ibtimes.co.uk/arms-race-betw ... ft-1508241

We have all seen the slow acceleration of the Apollo rockets that the camera follows until they are out of sight, yet they are evidently all the while picking up enough speed to become virtually invisible to any cameras that might attempt to capture them as they entered the "vacuum". And yet, if all goes according to plan, the military will have unmanned rockets capable of achieving speeds approaching less than one sixth the speed of Apollo rockets by the year 2040. That gives them another thirty years or so to achieve what they had already done one hundred years prior.

So, I submit my vote in favor of your midget soldier rocket achieving orbit. Maybe next we will see pigs achieving orbit by ejecting cotton candy from their snouts, why not?

[Kham]

Came across this first video and thought it had promise as a demonstration of Newton's 3rd Law of Motion. I also thought the video did a good job of explaining the differences between the two camps, Pro Spacers versus Pro Earthers, in layman's terms. My diagrams are not nearly as eloquent as Simon's, probably because they were lifted from the video, but I too am waiting for a physicist to explain the results of the demonstration from the video.

Definitions: Pro Spacer believes rockets can fly in a vacuum. Pro Earther believes rockets need atmosphere to fly.





Consider the standard balloon car.



When you fill the balloon with air and release it out the back, what will happen?



What will happen if the air exiting the balloon gets diverted, will the balloon still move forward?



You will have to watch the video to see if the balloon car moves forward when the exiting air is diverted.

NASA SPACE PROGRAM HINGES ON 1 LIE

The big question is this: Is this a valid experiment? Does it demonstrate that for movement to take place, the air exiting the balloon must push against the atmosphere? Watch the whole experiment at the link below which will start at 6:27. The explanations, should you care to listen to them, are at the beginning of the video.

There is another video that demonstrates the idea of how thrust works also using a standard balloon car. Although this clip does not disprove that rockets can operate in a vacuum, it does demonstrate the pushing against air idea, in that air exiting the balloon must push on the atmosphere behind it in order for the balloon car to move forward. I included this link because it was a second demonstration of that same idea from the first video and it’s entertaining. The experiment at the link below will start at 9:20. The explanations are at the beginning of the video.

NERD ACCIDENTALLY PROVES ROCKETS DON'T WORK IN SPACE!

[rusty]

There is another video that demonstrates the idea of how thrust works also using a standard balloon car. Although this clip does not disprove that rockets can operate in a vacuum, it does demonstrate the pushing against air idea, in that air exiting the balloon must push on the atmosphere behind it in order for the balloon car to move forward. I included this link because it was a second demonstration of that same idea from the first video and it’s entertaining. The experiment at the link below will start at 9:20. The explanations are at the beginning of the video.

NERD ACCIDENTALLY PROVES ROCKETS DON'T WORK IN SPACE!

Thanks so much for bringing this up. Amazing experiment - so simple and yet so telling.

You're right that it does not fully "disprove that rockets can operate in a vacuum". But it's probably the closest we can get under atmospheric conditions. We know that the defenders of "rocket science" will come up with some lame excuses, something along the line of "we already told you that rockets are less effective in vaccuum, but they still work quite well, and you can't simulate that with something as simple as a balloon and a vacuum cleaner, yadda yadda yadda...".

To me that's pretty much it. Game over for all of THEIR space clown fantasies. Once and for all.