Lunar Rover

[k0ua]

If you had a room with a vaccume and released an air filled balloon, would it propel itself?

Absolutely. But you didn't say the room had no gravitational forces. So this room would not be an analogue for deep space. The balloon would fly about the room and fall to the floor. But it would not fly like it does in an air filled room as the lifting surface of the balloon would not come into play here as it does in an air filled room.

Also if you blew up the balloon in air pressure and then put it into the vacuum chamber it may burst as the air pressure inside the balloon would inflate it further in the vacuum.

 

[Industrial Toys]

I am having a hard time comprehending this. I could see that a firearm fired in a vaccume, would eject the projectile normally. If the back of the cartridge was open, not so sure.

 

[/pine]

In this clip from 'The Martian' at about the .30 mark the protagonist punctures the glove in his space suit and uses the pressurized suit like a thruster rocket to propel himself close enough to be rescued...(FWIW the writer is very keen on keeping all the science in his stories authentic)

The Martian (215): Mark Rescue Final Scene - YouTube

 

[k0ua]

I am having a hard time comprehending this. I could see that a firearm fired in a vaccume, would eject the projectile normally. If the back of the cartridge was open, not so sure.

Well a cartridge case that was not contained would never develop any chamber pressure vacuum or no, and never propel the projectile out of the chamber, let alone down the barrel.

 

[Industrial Toys]

I can see if you eject mass, there is an opposite reaction. But thrust isn't mass. At lease not very much except in the medium comprising that thrust.

 

[k0ua]

I can see if you eject mass, there is an opposite reaction. But thrust isn't mass. At lease not very much except in the medium comprising that thrust.

I am not sure what you just said. But I do agree that thrust is NOT mass. You eject mass in one direction and you will have thrust in the opposite direction. Works just as well down here on earth with gravity and air too. Take your shotgun with an 1 1/2 ounce turkey load. fire it South, and tell me if your shoulder doesn't move North. And better yet put your shoulder firmly up against a good big tree and fire it again, and tell me if you don't have one heck of a bruised shoulder and a lot of pain.

 

[Industrial Toys]

If you fired the shotgun in a vaccume, you would still feel the kick, but I'm still thinking if you removed the shot, you might not.

 

[4570Man]

If you fired the shotgun in a vaccume, you would still feel the kick, but I'm still thinking if you removed the shot, you might not.

If you removed the shot and wad most of the powder won’t burn and the primer isn’t strong enough for you to feel anything. If you left the wad most of the powder still won’t burn.

 

[k0ua]

If you fired the shotgun in a vaccume, you would still feel the kick, but I'm still thinking if you removed the shot, you might not.

If you removed the shot and step out your back door and fire it, it will have very little recoil as the mass ejected will just be the gas and the burned and unburned propellant being ejected. You would not even feel it. The vacuum has nothing to do with it one way or another.

It is all about that Newtons 3rd law of motion. The Vacuum doesn't matter. You don't have to have air to push against. All you have to do is eject mass. and when you are totally weightless you don't need to eject much mass to set a body in motion and once in motion it will stay in motion unless another force acts upon it.

If you are inside a space craft of course and it if filled with breathable air, the air resistance will slow and eventually stop your motion. but without the air resistance, you are the energizer bunny. Except for solar wind, and other forces even in deep space.

 

[k0ua]

If you removed the shot and wad most of the powder won’t burn and the primer isn’t strong enough for you to feel anything. If you left the wad most of the powder still won’t burn.

And for darn sure it wont activate any automatic action of any kind or cock any internal hammers. and will leave a mess of unburned propellant particles to clean up.

 

[k0ua]

So Industrial Toys, are we all good ?

 

[MossRoad]

Think about it this way... no air involved.

In space, rockets zoom around with no air to push against. What's going on?

Rockets and engines in space behave according to Isaac Newton's third law of motion: Every action produces an equal and opposite reaction.

When a rocket shoots fuel out one end, this propels the rocket forward no air is required.

NASA says this principle is easy to observe on Earth. If you stand on a skateboard and throw a bowling ball forward, that force will push you and the skateboard back. However, because your weight on the skateboard is heavier than that of the bowling ball, you won't move as far.

That's the challenge engineers face when designing space engines. Yes, a small amount of thrust does push the spacecraft forward, but it often takes a great deal of fuel to get going anywhere quickly. More fuel means more weight, which adds to the cost of a mission.

from here: How Do Space Rockets Work Without Air?

 

[buickanddeere]

I'm having a hard time understanding that. If I push my hand out quickly into the air, I don't go anywhere. Push it against a wall and different story. Same with a jet ski. Feed it some water when the jet isn't submerged and it won't have (much) forward movement.

Doesn稚 work that way. Push your hand against something that weighs 200lbs .

 

[Industrial Toys]

I thought about it and take back the jet ski remark. With that kind of MASS, a jet ski would operate in the air if supplied by water. Witness hanging onto a fire hose!

So my question still stands. How does Rocket exhaust constitute MASS? You are not firing bowling balls out the end of the spacecraft.

And you James, said so yourself. Take the projectile out of a gun and you have appreciably no more action/reaction, aka "kick".

 

[k0ua]

I thought about it and take back the jet ski remark. With that kind of MASS, a jet ski would operate in the air if supplied by water. Witness hanging onto a fire hose!

So my question still stands. How does Rocket exhaust constitute MASS? You are not firing bowling balls out the end of the spacecraft.

And you James, said so yourself. Take the projectile out of a gun and you have appreciably no more action/reaction, aka "kick".

Rocket exhaust consist of a considerable mass. All of the thousands of pounds of hydrazine (one type of rocket fuel) and oxygen combine in the rocket nozzle and every bit of that mass is blown out the back of the nozzle in the gaseous state. When you burn matter in a fire , you do not destroy it. you simply transform it. Matter is neither created nor destroyed in a chemical reaction like a "fire" for instance. Lets say you take a stick of wood that weighs 10 pounds. and you burn it as completely as you can. You will have an amount of "ash" or that chemical part of the wood that that will not oxidize like heavy metals for instance, and you will have a large amount of combustion gasses given off. The mass of all of the gasses and all of the Ashes PLUS the amount of oxygen will add up to more than 10 pounds because of the oxygen added to the chemical reaction. You might be hard pressed to collect and weigh all of the components in a fire, but trust me that is what happens. And trust me again when you see an old Saturn 5 lighting off or the space shuttle or what ever there are tons and tons of mass thrown out those rocket nozzles.

 

[k0ua]

We are going to need to get these basics about thrust and mass down before we start talking about theoretical things like Alcubierre warp drives and such. Industrial Toys, are you with me? Or do we have a ways to go..

 

[k0ua]

And you James, said so yourself. Take the projectile out of a gun and you have appreciably no more action/reaction, aka "kick".

Yes, I did, but but words like appreciable need to be quantified. In other words, we have to actually measure the thrust from out shotgun with no shot, and nothing but a "little' gas and some unburned particles shoved out the barrel. Of course there is "some" thrust backwards, but in our limited "senses" we would be hard pressed to quantify or measure it. We would need delicate actual instrumentation to do those measurements. Often what seems like "common sense" "seat of the pants" perceptions do not hold up to the hard cold science of actual measurements of scientific principals.

 

[/pine]

Since this thread is basically about moving in space etc...and it's o/t anyway...

What about UFOs?
I've personally never seen a UFO...but have read and heard about a lot of folks that have (not just fake crap like bigfoot etc.)...

You hear a lot of reports about the speed and maneuverability along with the lights/colors etc...but you never hear anything about exhaust trails etc or anything exiting the vessels...no glowing ion trail or radiation streams etc., etc...

Any thoughts on out of this world propulsion systems that would allow something to move with speed and in ways unknown to humans? (or terrestrial humans anyway)...

 

[Industrial Toys]

Zero Point Energy? What do I know?

I like to see stuff demonstrated although I know even that means little.

Of all the spacecraft and satalites, you know (apparently) there isn't a single photograph of Earth? Don't believe me? Look into it. Some stiched together and filled in ones from satalites. That's it!

And why does the UN logo use the flat earth map? All very strange!

 

[k0ua]

Zero Point Energy? What do I know?

I like to see stuff demonstrated although I know even that means little.

Of all the spacecraft and satalites, you know (apparently) there isn't a single photograph of Earth? Don't believe me? Look into it. Some stiched together and filled in ones from satalites. That's it!

And why does the UN logo use the flat earth map? All very strange!

Are you kidding? Tell me you are not a flat earther?