Terminal Speed For A Flying Object Not Fall On The Ground

Do you mean "to stay in orbit"?

Aerodynamics, we do not use such in outer space actually. Well, if "fly" definition require such condition of yours as stated, what I meant is not anymore flying. I agree.

I believe he said neglecting aerodynamic factors. So how fast without any lift.

16,200 MPH

16,200 MPH

Does this vary with altitude? Is this speed relatively greater at high altitude or at lower heights?

Well, I believe the speed would increase with altitude.

Well,

Yes it does come down to that. It is all relative.

I think this is what you are looking for...

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

If it's thrust upwards is equal to its weight, like a helicopter or a Hawker Harrier in hover, then its minimum speed is zero.

All speed is relative. (To my knowledge none of my relatives have any speed.) Speed implies a common inertial reference frame between two objects. So any object not part of our inertial frame really should not be considered as having a known speed until it enters our inertial frame. Then you think about it, flying requires at least three objects and one of the two must be a fluid. If you remove the fluid versus smallest mass speed component from consideration then it becomes impossible to fly. It is tempting to try to remove the drag component that will reduce the speed during flight, but without drag there cannot be flight. So you've asked for a quantitative value for something that cannot exist.

Sorry but I cannot help you any further than that.

"If you remove the fluid versus smallest mass speed component from consideration then it becomes impossible to fly....but without drag there cannot be flight"

So does that mean a space ship is not considered flying as it goes between Earth and Mars? What do we call it? Being propelled?

I'd accept propelled while it was under some form of propulsion. I expect though that most of the time it will be actually coasting. To me, flight implies a heavier than air object fighting gravity to stay aloft in the air.

Sounds reasonable.

You didn't specify the mass of the flying/orbiting object. It gets interesting if the object is as massive as, or more massive than, Earth.

Actually, take for instance an astronaut is bringing a 0.45mm pistol to the moon then fired it there. How much velocity does the bullet need in order not to fall to the ground. I thought that bullet can stay rotating around the moon forever at a certain elevation from the ground.

Weight of the bullet = Centrifugal force (angular velocity)

Weird... =)

Just for learning sake. not so much about.

No oxygen on the moon, projectile powder will not oxidise to form gas. therefore no movement. Unless your astronut drops the gun your bullet will stay at the same evation as the gun.

The chemical Equation for gun powder, you might try to look at is

2 KNO3 + S + 3C => K2S + N2 + CO2

I never see, O2 from air on the left side, except that the oxygen needed for the bullets to explode or ignite is from KNO3.

Bullets will be working just fine on the moon.

Actually, they don't use gun powder in firearms, and haven't used it in a very long time over 100 years. Smokeless powder is used, typically a nitrocellulose based compound with some additives.

Not true! Welcome to the dark side.

Let me clarify then, they haven't used gun powder in modern firearm created in the over 100 year. I guess you are correct it that they still employ it for some minority of hobbyist who like to play a bit with old black powder historical replicas (though i suspect even they use modern firearms and bullets more frequently then the historic black powder replicas).

Whatever is used, I think we're in agreement that it would do its job just as well in vacuo as in an oxygen-rich atmosphere.

How (be asked, rhetorically,) could enough oxygen possibly be drawn in quickly enough for such a reaction to complete so quickly?

Hmm, while I agree atmospheric oxygen may not be necessary, I would not want to commit to the comment that a gun would fire in space. The bullets may not be stable under vacuum, the pressure inside the bullets from being loaded udner atmospheric conditions and the possibility of sublimation of some of the components could lead to excessive but not explosive gas pressures early that cause some issues.

Giggle.

Now what could possibly make the bullets become unstable in a vacuum? The lack of friction as it hurtles through space. There should not be any gas to pressurize inside the bullet. Now I'll grant you that a cartridge that was not intended to be placed in a vacuum might have a bullet seated so lightly that the 15PSI pressure might dislodge the bullet from the cartridge but I'm certain that any cartridge intended to be used in space will not have a bullet so lightly pressed in place.

If you read, you will notice no where did i state it will never work, but rather that it may not work consistently. You are trying to create a false context for the basis of your argument to better support your position.

As I stated clearly in previous posts, "Hmm, while I agree atmospheric oxygen may not be necessary, I would not want to commit to the comment that a gun would fire in space." and "To be honest i suspect most of the time it might work, but would not want to guarantee it. I also suspect the misfire rate would increase significantly (unless these were special shells)." The statements were very clear, a gun may not fire in space at least a significant portion of the time more frequently than is typical for misfires on earth.

You are creating a simple argument of black and white, it will or it won't work, and on your basis if it only worked once that would prove your argument. However, that does not disprove my contention that it may not work as it would on earth, and I would not want to commit to it would work, as it may fail the one time I guaranteed it. A guarantee would mean I would be responsible if it failed even one time more than is typically expected. There are many reasons it may fail to function properly in space unrelated to the exothermic reaction of the basic component of the propellant. As stated I do not have sufficient information about all the considerations to make that determination absolutlely. Apparently, however, you are a explosive ordinance chemical engineer with the experience in munitions operation in space and do have the expertise derived from that experience and training, so you may be correct. It may well function with not less frequency of misfire than it would on earth. I am guessing you would be willing to guarantee that and sign your name to such a guarantee.

While I have never thrown a loaded bullet into a vacuum chamber, I'll say with some authority that the bullet to case crimp would probably be "air tight".

However, the primer/primer pocket seal(or lack of) may allow equalization of pressure over a short period of time. Primer/powder initiation on firing would deform the primer to seal the pocket.

I agree Lyn

It's all fairly silly that bullets won't work in a vacuum - or need 'air' to burn the charge.

They work fine at any altitude - 100,000 ft for example - what's the pressure and O₂ availability? Damn near 'space'.

They also work underwater http://world.guns.ru/assault/rus/aps-underwater-e.html

and though it's been said by formula - all explosives carry their own oxidizer - or they couldn't achieve the burn rates that make them "explosive".

And, the amount of air in the casing or between the 'granules' would contribute zilch in O₂ provision.

And "16,200" seems as good a number as any to "answer" this OP.

Just don't be shooting that thing at my peddle plane

bear in mind there is a pressure insire the casing of 1 atmosphere and near 0 outside it. So then how long does the seal hold, and what happens once it loses pressure inside? It is probably true that if you use the fire arm rapidly enough after placing it in a vacuum, it will operate fine, as it takes time for decompression and sublimation to occur. Though sublimation (or evapoartion as some components of the mopdern explosive used are liquids) may not occur, or the sublimation (evaporation) that does occur might just make the explosive more reactive. Vacuum is much like firing a bullet under water, except shell casings might not leak water when they can leak gases. Leave the bullet under water long enough and you may have a problem. To be honest i suspect most of the time it might work, but would not want to guarantee it. I also suspect the misfire rate would increase significantly (unless these were special shells).

BTW, where does the 100,000 foot altitude example come from, that you are absolutely sure they will work in vacuum? 19 miles seems a bit high for a dog fight.

Salient point is, as said;

"the amount of air in the casing or between the 'granules' would contribute zilch in O₂ provision".

You write;"(or evapoartion as some components of the mopdern explosive used are liquids)"

Can you give an example of a liquid explosive this hand gun's ammunition might use?

Or are you obfuscating to cast H.E.? E.g. RDX

topic 2. "Leakage"

Since some 'bitter lessons' in WW1, military small arms ammunition has been required to undergo 'environmental testing' covering arctic, jungle, desert, altitude and immersion. The technology rapidly become 'default' in ammunition production.

For example; some 30 years after Kokoda, people were still finding loaded Lee-Enfield .303's in the mud, which would fire.

And - I'm reasonably sure it's a near enough figure

McDonnell Douglas F-15 Eagle - Wikipedia, the free encyclopediaThe requirements called for single-seat fighter having a maximum take-off ...... altitude as over 94000 ft (29000 m), well above the F-15's service ceiling. ...

and someone would have noticed the weapons tests failed.

As I recall part of the process to making pyrocellulose is to mix gun cotton with alcohol to gelatinize it. Plus depending on the mix they may be nitroglycerine, nitroguanidine, diphenylamine, etc. added to the smokeless gun powder.

Finding a Lee Enfield in the mud that may fire doesn't mean it will perform within accepted limits (without consideration for conditions). Also, that is only indicative of a water tight seal, not a absolute vacuum tight seal. So the question becomes how do they perform after being placed in the vacuum of space (or that of the moons atmosphere). It is not clear to me that there is any evidence of test results that clarify the question sufficiently for me to agree that the shells would perform consistently under those conditions, like they would on earth. I think this would need to be tested. I would not want to depend on this in a crisis with out better infromation.

So 94,000 is the maximum elevation? So substantially less than 100,000 (6%).

Oh give it up. You've gone from "it will never work" to "it will never be consistent" over a hypothetical thought experiment.

My apologies; I should have googled the published number before running off at the keyboard with a rounded illustrative attitude density number.

"Also, that is only indicative of a water tight seal, not a absolute vacuum tight seal"

A vacuum is ^_(about) - 14.7 psi

What do you estimate the pressure change would be in the casing, if it was loaded at 20 C⁰ at sea level, then left out in a desert for 24 hours? Say 45C⁰ to - 5C⁰

What would you estimate the pressure change; if it was left on the moon for a night and day?

Maybe we you should be asking "what happens to guns and ammunition near absolute zero?"

Perhaps the action shattered or the whole thing shattered in his hand?

Which would be another valid consideration that could adversely effect performance, since the moon has much larger temperature swings than the surface of the earth.

Another question to consider I believe is eluding you, will a can a gas penetrate a water tight seal if you do not have water surface tension to deal with? does a water tight seal exclude water from entering or gases from exiting?

"eluding"?

The desert 'question' eluded to gas tight (& not wet)

The jungle eluded to 'don't breath in humidity' (and time).

The altitude eluded to 'vacuum' (and temperature).

But taking your question on seals, in isolation;

A water tight seal is not necessarily gas tight. Water is a larger molecule than most gasses. A 'wet' water seal can obviously transmit a smaller gas molecule via the water film, given a suitable pressure differential (inc. osmotic potential).

Seals may be 'directional'. As mentioned earlier by another poster, the primer cap might vent. "Re-loaders" look for this, along with other signs, of a casing 'reaching life'. Shooters look for it as a sign of a 'crap manufacturer'

But perhaps our astronaut cowboy is a re-loader? (well at least that rules out a '45 rim fire') Or maybe buys 'job lot rubbish'?

But if you are worried that a metal-to-metal seal is not 'gas tight', or needs to be 'wet' to be so - it's time for you to look at pneumatic and gas fittings.

Does anybody know what magical explosive charge was used in those explosive bolts used in so many science fiction movies that NASA, the Soviet Space Program, and the European Space Agency used. We all know that those movies can't be real because those rockets would just fly off the back of the great turtle. I mean if they really could go as far as they claim, the great turtle would just swat them out of the sky. He's just a bit shy. He doesn't like people taking his picture.

Sounds like homework Red?

Me? Oh no. I don't want to make the great turtle angry. Besides we all know that explosive charges can never work in a vacuum. There are no vacuums. The great turtle abhors vacuums. He can't breath to well in a vacuum. Oops. Forgive me, maybe she can't breath well in a vacuum.

Wrong. The gun powder chemistry implies that it does not need external Oxygen to burn and produce the gas! The chemical mix of the powder has all the required oxygen to burn produce the gas and explode the bullet out of the barrel. Sorry.

This was already pointed out by Noudge79 , along with the chemical formula to prove it, in post #15. I was gonna jump on that one, too, till I saw his comment.

Cheers.

Gunpowder is a solid propellant. It contains both the fuel and oxidizer for the chemical reaction to occur. That's why it can work in a chamber sealed by to breach block at one end and a bullet at the other.

Firearm propellants (and explosives) function by the decmposition and recombination of nitrogen compounds and other elements, such as sulfur and carbon. No external oxidized nacessary. This is why this stuff is so dangerous to play with.

Simplified equations for calculating your "no atmosphere bullet orbit velocity" example were provided in post #8 wiki link. Using those equations...

Vo ~ sqrt { G M / r }
Vo ~ sqrt {(6.67428e-11) [m^3 1/kg 1/s^2] (7.36e22)[kg] / 1737400 [m]}
Vo ~ sqrt { 2.827e6 [m^2/S^2] }
Vo ~ 1681 [m/s]

45 cal pistol ~ 370 [m/s]
50 cal sniper rifle ~ 850 [m/s]

You need to ~double the velocity of the 50 cal to orbit the moon near the surface.

I bet superman has to achieve more velocity than the 50 cal sniper riffle in order to fly on air, looking at his mass is more than 100 times than that of the bullet.

In air he might have more lift per unit mass, of course he may well have more air resistance due to the large cross-section.

Did y'all notice that the original poster says he wants his autronaut to be bringin' a .45 mm pistol to th' moon???

I be sure he's meanin' a .45 caliber pistol, but I, being the ol' cop on the beat noticed the 'lil bullet he's mentioning.

Whoo wee! That's a lil' ol bullet at .45 mm!!! More like a pen refill!

you got me there CrimeCrusher, that was a mistake actually, really sorry. My hands are up with the cops. hahaha

That is a very fine point indeed.

I was once very interested in this question.

http://cr4.globalspec.com/thread/2714/A-Question-of-Orbital-Velocity

chris

But how fast will the Astronaut be traveling after he/she fires that .45???

Since action and reaction forces are equal impulses will be also equal so that Astronaut velocity will be bullet velocity x ratio of masses (bullet mass /Astronaut mass).

Assuming a non anchored, relatively inelastic astronaut

Wot demi-soixante-neuf sed.

If the man with the gun was standing on (i.e. rigidly bolted to) the surface of the moon, you'd have to include the moment of inertia of the moon in your calculations.

If he jumped and fired at the highest point of his jump (so that vertical components of velocity of the bloke and the departing slug can be neglected) then you only need to consider the change in the tangential component of his velocity.

Anything in between (e.g. the gunman standing on the surface of the moon, or pulling the trigger too early or too late) would complicate the issue.

when affected by gravity (neglecting aerodynamic factors) there is no speed in which and object can remain flying. Do you recall projectile motion??? Inerita will not allow it in a gravitational field. the faster you go the further you travel along the X-axis however you still fall at G along the Y-axis.

Are you a member of the Flat Earth Society, by any chance?

Thats why we have to reposition our space craft from time to time. Other wise they make nice fire works.

Think Geosynchonous orbit, which is no aerodynamics, just a matter of flying as fast as the object is falling towards the gravitational point (earth). Keep in mind acceleration due to gravitational force is a vectored quantity. So if you move fast enough on the y axis by the time you fall far enough on the x axis, you will have moved past the central body you are orbiting and have velocity in the y axis and gravitational acceleration on the x axis. If this didn't work this way the moon would have fallen a long time ago.

From the surface of the Earth, escape velocity (ignoring air friction) is about 7 miles per second, or 25,000 miles per hour. Given that initial speed, an object needs no additional force applied to completely escape Earth's gravity.

Extract from this : http://www.physlink.com/Education/AskExperts/ae158.cfm

I think this is the slowest one to fly - but I could be wrong. And of course, kites can fly at zero ground speed.

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

Vous avez perdu le plot, mon ami. L'OP a dit "négliger les facteurs aérodynamiques"...

Comment peut voler un kite sans air?

You wrote; "You lost the plot, my friend. The OP said "neglecting the aerodynamic factors" ... How can fly a kite with no air?"

How about your typical college dynamics problem "neglecting friction"? Does than mean fiction does not exist? No it does not. It means skip that set of parameters.

So - lets look at the OP question.

Terminal Speed For A Flying Object Not Fall On The Ground

The word "flying".

How is this achieved?

Can one 'fly' in a vacuum?

Therefore it is perfectly reasonable to consider the question as: 'what flying device has the lowest velocity without stall?'

"velocity" is relative, so both air speed and ground conditions are addressed.

Or to paraphrase in French; Vous assumé la parcelle, mon ami. Le PO a dit "en négligeant les facteurs aérodynamiques" ... pas "dans le vide"

Comment fonctionne un satellite voler?

Lol, neglecting means for the purposes of this problem (or any problem so stated) it does not exist. Neglecting aerodynamics is obvious, no lift and no air resistance. Just like neglecting friction in a problem means no heat generated and no resistance to movement due to friction. This is a simple college physics problem to apply various concepts like transposing coordinate systems and simple vector analysis, spherical/cartesian.

Since you use French I allow myself a small correction to make it even better: "assumé" is a "participe passé" so that it requires a verb as for instance "avez" to make the right form as : "Vous avez assumé...". If you want to consider it as present tense then you should use the right end for the second person : " Vous assumez...". I do not yet understand what you mean with "parcelle"? This word means a small part and it is usually used related to a small ground area : "une parcelle de terrain.." thus my problem.

Thanks for that - but the French structure is not of my origin. It's that of the post I was responding to.

To your query;

"Parcelle", as in "une parcelle de terrain.." a small ground area.

In English this is "a plot", as say in garden plot. However the word also means 'story line' (histoire?, conte?, or intrigue?)

"You have lost the plot" is a fairly common phrase in English. In that context it doesn't mean the "small ground area" has been 'mislaid', or 'seized by a creditor'.

In the story line use, it means you are failing to follow events, so are misdirected on a spurious agenda.

E.g. it can happen to people who don't read what I'm responding to, and consider source and my response, as a 'story line', or "in context".

The higher above the earth's surface the "flying" object, the less the speed required. At the earth's surface, the centripetal acceleration on a (circularly) orbiting object is v²/r, which equals the gravitational acceleration of 32.16 ft/s². Approximating r as 4000 miles = 21,120,000 ft, simple arithmetic gives an orbital speed of a bit less than 18,000 mph. The ISS might be about 16,000 mph.

16,200 MPH for a cannon ball.

How high is the cannonball? I haven't yet seen calcs or citations in support of this.

Assuming no aerodynamic effects, the object is irrelevant; it could just as well be a feather.

I'll have to look for the reference I saw that made me mouth off in the first place.

I'll get back to you.

Newtonian Mountain

Don't know how authoritative it is.

It looks like they blew it; but I can't tell where, because no formulas, calculations, or basis numbers were given. However, I have found a fair amount of contrary material.

"... contrary material ..." ?

Post 66 was based on Googling "ISS orbital speed" and "geosynchronous orbital speed." Post 59 gave some basic numbers, but did not explicitly carry out the arithmetic.

I realize that it would be a bit lame to say "every schoolboy knows that low-orbit speed is about 18,000 mph, and escape velocity is about 25,000 mph--even though both are true.

Never mind. That's not a cannon ball.

Even the ISS orbital speed > 17,000 mph; so 16,200 is not a good number except for some as yet unspecified higher altitude.

Geosynchronous orbital speed ≈ 6880 mph.

The Moon seems slow

Same equation, though.

So how come the Sun makes round every day?

Because the earth rotates, not because the sun has a high orbital speed. <sigh>

Hey - what's with the "<sigh>"? How could "earth rotates" come into it - cannons don't have rifling

That's even more irrelevant than before. The earth's rotation might make it appear the sun orbits us in 24 hours, but that's just baloney.

If you wish to engage in witticisms, that may be fine (I try to do it too), but beware that some attempts are grotesquely inferior.

Sorry - I shall try to do better

Not that the whole thread isn't a "witticism"

Maximu speed in space

http://www.google.co.uk/search?q=maximum+speed+in+outer+space&sourceid=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8&rlz=1I7ADFA_en&redir_esc=&ei=4sVfTZOZF8iy8QP_yOhZ

Mimimum Speed to stay in orbit

http://www.google.co.uk/search?q=whats+the+mimimum+spped+needed+to+stay+in+orbit&sourceid=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8&rlz=1I7ADFA_en&redir_esc=&ei=IMZfTZKjBcew8QOExola

Minimum speed needed to stop orbit decaying ( this is the one i think you need)

http://www.google.co.uk/search?hl=en&rls=com.microsoft:en-US&rlz=1I7ADFA_en&&sa=X&ei=c8ZfTdLMIYG44gaIury9CQ&ved=0CBUQBSgA&q=what%27s+the+minimum+speed+needed+to+stop+orbit+decaying&spell=1