Does Rocketry Work beyond Earth's atmosphere?

If NASA faked the moon landings, does the agency have any credibility at all? Was the Space Shuttle program also a hoax? Is the International Space Station another one? Do not dismiss these hypotheses offhand. Check out our wider NASA research and make up your own mind about it all.
Maat
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by Maat »

▲ Ah, it's going to be "launched" from French Guiana, huh? How very convenient :rolleyes:

Per Wiki:
The Guiana Space Centre, located a short distance along the coast from Kourou, has grown considerably since the initial launches of the "Véronique" rockets. It is now part of the European space industry and has had commercial success with such launches as the Ariane 4 and Ariane 5
The Guiana Space Centre or, more commonly, Centre spatial guyanais (CSG) is a French and European spaceport near Kourou in French Guiana. Operational since 1968, it is particularly suitable as a location for a spaceport as it fulfills the two major geographical requirements of such a site:

• it is quite close to the equator, so that the spinning earth can impart some extra velocity to the rockets for free when launched eastward, and
• it has uninhabited territory (in this case, open sea) to the east, so that lower stages of rockets and debris from launch failures cannot fall on human habitations.

The European Space Agency, the French space agency CNES, and the commercial Arianespace company conduct launches from Kourou.[1][2][3] This is the spaceport used by the ESA to send supplies to the International Space Station using the Automated Transfer Vehicle.

The location was selected in 1964 to become the spaceport of France.[4][5] When the European Space Agency (ESA) was founded in 1975, France offered to share Kourou with ESA.[4][5] Commercial launches are bought also by non-European companies. ESA pays two thirds of the spaceport's annual budget and has also financed the upgrades made during the development of the Ariane launchers.
I'd love to know how it's supposed to propel itself all the way to and then "hang out at the L2 Lagrange point" :P
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by Heiwa »

simonshack wrote: can a hydrojet engine on a ship push the vessel forward if the water jet is sprayed above the water surface?
Yes, water ejected into air (or vacuum or any space) from a hydrojet (attached to a boat) will push the boat forward. Reason is that the ejected water applies a force on the boat. The engine just accelerates the water ejected out of the hydrojet.

As I have said many times - water ejected from a fire hose nozzle into air/vacuum/space applies a force on the nozzle/hose/person holding the nozzle/hose. Easy to verify. The water is evidently accelerated by a pump at the other end of the hose.

What is the problem? Only fools believe that Rocketry Doesn't Work in the Vacuum. :P
hoi.polloi
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by hoi.polloi »

I feel like every time we have tried to draw a parallel to Earth physics, we have fallen in the trap of using Earth physics for direct comparison. Maybe we can stop replacing our hypotheticals (water for gas, boats for rockets) and stick to Boethius' main allegations.

Such as the point that gas simply does not remain gas in the vacuum.

The point is lost when we start calling each other fools for merely asking questions and challenging those questions.
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by simonshack »

Heiwa wrote:
simonshack wrote: can a hydrojet engine on a ship push the vessel forward if the water jet is sprayed above the water surface?
Yes, water ejected into air (or vacuum or any space) from a hydrojet (attached to a boat) will push the boat forward.
Would a waterjet ferry thrusting the jet above the waterline go as fast as with the jet kept below the waterline?

See, I just called this company : http://www.jetserviceteam.com/contatti

I asked to talk with their in-house technician. The short convo went a bit like this:

Me: Hello, I'd like to know if a water scooter would work if the jet was directed above the sea surface.
Tech: Huh?? (brief pause) Why would you want to do that? You wanna make a fire hydrant?
Me: Oh no, my question is only whether the scooter would still move forward.
Tech: (laughing) Of course not! The scooter wouldn't move but someone would probably get very wet!
Me: (*blushing somewhat*) Oh, ok - that's what I figured... Well, thanks a lot for your time, sir - bye!

The guy must have thought I was nuts. :P
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by brianv »

Heiwa wrote:
simonshack wrote: can a hydrojet engine on a ship push the vessel forward if the water jet is sprayed above the water surface?
Yes, water ejected into air (or vacuum or any space) from a hydrojet (attached to a boat) will push the boat forward. Reason is that the ejected water applies a force on the boat. The engine just accelerates the water ejected out of the hydrojet.

As I have said many times - water ejected from a fire hose nozzle into air/vacuum/space applies a force on the nozzle/hose/person holding the nozzle/hose. Easy to verify. The water is evidently accelerated by a pump at the other end of the hose.

What is the problem? Only fools believe that Rocketry Doesn't Work in the Vacuum. :P
I don't think your brain is working -- atmosphere or vacuum!
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by Heiwa »

simonshack wrote:
Heiwa wrote:
simonshack wrote: can a hydrojet engine on a ship push the vessel forward if the water jet is sprayed above the water surface?
Yes, water ejected into air (or vacuum or any space) from a hydrojet (attached to a boat) will push the boat forward.
Would a waterjet ferry thrusting the jet above the waterline go as fast as with the jet kept below the waterline?

See, I just called this company : http://www.jetserviceteam.com/contatti

I asked to talk with their in-house technician. The short convo went a bit like this:

Me: Hello, I'd like to know if a water scooter would work if the jet was directed above the sea surface.
Tech: Huh?? (brief pause) Why would you want to do that? You wanna make a fire hydrant?
Me: Oh no, my question is only whether the scooter would still move forward.
Tech: (laughing) Of course not! The scooter wouldn't move but someone would probably get very wet!
Me: (*blushing somewhat*) Oh, ok - that's what I figured... Well, thanks a lot for your time, sir - bye!

The guy must have thought I was nuts. :P
Evidently any water ejected by a water scooter or fire hose hitting a person will wet the person. Great fun! But at the same time the water ejected from the scooter or fire hose applies a force on the scooter or fire hose.
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by simonshack »

Heiwa wrote: Evidently any water ejected by a water scooter or fire hose hitting a person will wet the person. Great fun! But at the same time the water ejected from the scooter or fire hose applies a force on the scooter or fire hose.
Come on now, Heiwa.

My question is: would a ferry/or water scooter be propelled at the same speeds with the jet BELOW and with the jet ABOVE the waterline? Please no more 'jokes', thanks!
Heiwa
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by Heiwa »

simonshack wrote:
Heiwa wrote: Evidently any water ejected by a water scooter or fire hose hitting a person will wet the person. Great fun! But at the same time the water ejected from the scooter or fire hose applies a force on the scooter or fire hose.
Come on now, Heiwa.

My question is: would a ferry/or water scooter be propelled at the same speeds with the jet BELOW and with the jet ABOVE the waterline? Please no more 'jokes', thanks!
Answer is evidently YES! Any ejected water from a ferry/scooter will apply a (reaction) force on the ferry/scooter. The resulting change of speed depends on that force and, e.g. friction of the ferry/scooter. Pls, do not suggest Newton is wrong.
Take a rocket A in space with total mass m. Rocket A is equipped with a rocket engine and a fuel tank - all part of total mass m. When the rocket engine is fired and ejects parts of rocket A mass m as combusted fuel at high speed into space/vacuum surrounding the rocket A, the result is that the rocket A with reduced mass (fuel burnt) is subject to a force that changes its speed. The rocket engine works and does its job.
If you believe that the combusted fuel leaving the rocket A at high speed as a hot gas just disappears into space/vacuum not affecting the rocket A at all, i.e. the rocket engine does not work in vacuum - it fizzles, I feel you are wrong.
But I agree I have not tested rocket engines in space. :P
On the other hand I have tested many propulsion systems designed to work in water and they work all right. :rolleyes:
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by simonshack »

Heiwa wrote:
simonshack wrote:
Heiwa wrote: Evidently any water ejected by a water scooter or fire hose hitting a person will wet the person. Great fun! But at the same time the water ejected from the scooter or fire hose applies a force on the scooter or fire hose.
Come on now, Heiwa.

My question is: would a ferry/or water scooter be propelled at the same speeds with the jet BELOW and with the jet ABOVE the waterline? Please no more 'jokes', thanks!
Answer is evidently YES!
Ok, many thanks. I'll keep that in mind for future reference. <_<
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by brianv »

Answer is evidently YES!

Why the supporting adverb and captitalisation? To buttress that castle you are building on sand?

And why without question must we accept your nutty professor theories?
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by simonshack »

Heiwa wrote: On the other hand I have tested many propulsion systems designed to work in water and they work all right. :rolleyes:
I have my own propulsion system coming up this summer, Heiwa - and I can only thank you for the inspiration.

Hopefully NASA will help me fund this project, but if not - I'll gladly accept donations from you and any other Cluesforum members/readers. The objective of this experiment is, of course, to determine once and for all if a water-against-air jet will propel this scooter at the same speeds as the currently popular, water-against-water jets.

Image

It should be fun to see how it fares in water scooter races - where speeds up to 100km/h are reached.
Image

Hey - if it kicks ass, it may even end up being exhibited at the Smithsonian along with the Apollo scraps ! :)

***************
Just for the record:

My question was:
"Would a ferry/or water scooter be propelled at the same speeds with the jet BELOW and with the jet ABOVE the waterline?"

Your answer was:
"Answer is evidently YES! Any ejected water from a ferry/scooter will apply a (reaction) force on the ferry/scooter. The resulting change of speed depends on that force and, e.g. friction of the ferry/scooter. Pls, do not suggest Newton is wrong."
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by Heiwa »

Waterjets are designed to work in water. Propellers work in water or air as they shift water or air to apply a force on the vehicle. Cars or bikes are designed to work on streets and use friction between wheels and street to apply force on the car or bike (and the street). And rocket engines work in space/vacuum by ejecting hot gases at high speed through a nozzle into the vaccum. And all follow Newtons laws to accomplish their objectives.
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by Boethius »

Heiwa wrote:Waterjets are designed to work in water. Propellers work in water or air as they shift water or air to apply a force on the vehicle. Cars or bikes are designed to work on streets and use friction between wheels and street to apply force on the car or bike (and the street). And rocket engines work in space/vacuum by ejecting hot gases at high speed through a nozzle into the vaccum. And all follow Newtons laws to accomplish their objectives.
Space rockets are designed to work only in fantasies presented to us by production companies like NASA and Disney.

Science is against rockets working in space:
1. Gas can't push a rocket through space because:
  • i. Releasing gas into space does no work, creates no force.

    ii. Gas ceases to exist once it enters the nozzle of a rocket in space and is exposed to the vacuum. Without pressure gas becomes only unrelated molecules swiftly dispersing into the void.

    iii. A rocket can't push against something that doesn't exist nor can it use scattered, unrelated molecules as a propulsive force.
2. A rocket in space can only transfer energy from engine to hull and back again. No motion is generated. It is a giant battery connected to nothing.

3. Everything that moves must make an energy exchange with an object apart from itself (via a push or a pull). This is why a 90kg man can't pull himself off the floor and into the air but he can lift a 90kg weight off the same floor. A rocket cannot "push against itself" anymore than you can "lift yourself off the floor".


Rockets, like cars, boats and airplanes only function on the earth and in its atmosphere. Imaging them working anywhere else is science fiction.
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by Flabbergasted »

Despite its immensely important implications, this discussion has been extended beyond any usefulness. There is nothing left to say which hasn´t been explained, reiterated and reworded over and over. I would call it a day and put a period to it.
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Re: Why Rocketry Doesn't Work in the Vacuum

Post by idschmyd »

Image

Something like this (though not this, exactly) would pose a challenge to the WaveRunner up there, wouldn't it? (I'm not 100% on this, such is my scientific ignorance). I'm guessing it would shift on earth, forwards at first, propelled by the same force that makes an unattended hosepipe go crazy when you turn the tap on full. Couldn't tell you if it would work in a vacuum
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