Moon Rings

[Thunderbird]

If one were to fire a rifle bullet from the surface of the moon would it go into orbit ?
The reason I ask is that I was thinking about asteroid strikes on the surface of the moon and wondering if it would allow for the formation of a ring like Saturns. So the real question is, if it is possible the moon had a ring around it in the past ? Would the weak gravity and electromagnetic field allow for such a formation ?

[freeztar]

Originally Posted by Thunderbird

If one were to fire a rifle bullet from the surface of the moon would it go into orbit ?

I don't think you can fire a bullet on the moon. The lack of O2 would prohibit any kind of ignition.

Presuming you had a rifle sealed in an oxygenated chamber, I believe the bullet would travel away from the moon in a straight line, eventually leaving the Moon's gravity.
But, this is just a guess as I'm uncertain how do do the math for this.

The reason I ask is that I was thinking about asteroid strikes on the surface of the moon and wondering if it would allow for the formation of a ring like Saturns. So the real question is, if it is possible the moon had a ring around it in the past ? Would the weak gravity and electromagnetic field allow for such a formation ?

I don't think the moon's mass is enough to allow for 'moon rings'.
In fact, it seems that moons themselves may be the originators of planetary rings.

Originally Posted by wiki

There are three ways that planetary rings have been proposed to have formed: from material of the protoplanetary disk that was within the Roche limit of the planet and thus could not coalesce to form moons; from the debris of a moon that was disrupted by a large impact; or from the debris of a moon that was disrupted by tidal stresses when it passed within the planet's Roche limit. Most rings are thought to be unstable and to dissipate over the course of tens or hundreds of millions of years, but it appears that Saturn's rings might be quite old, dating to the early days of the Solar system.

Planetary ring - Wikipedia, the free encyclopedia

Good questions TBird.

[Thunderbird]

The gun powder is its own fire triangle.

a nitrate—typically potassium nitrate (KNO3)—which supplies oxygen for the reaction;
charcoal, which provides fuel for the reaction in the form of carbon (C);
sulfur (S), which, while also a fuel, lowers the temperature of ignition and increases the speed of combustion.
Potassium nitrate is the most important ingredient in terms of both bulk and function because the combustion process releases oxygen from the potassium nitrate, promoting the rapid burning of the other ingredients

[freeztar]

Originally Posted by Thunderbird

The gun powder is its own fire triangle.

Interesting. Thanks for the info.
My gun tech knowledge is obviously close to zilch.

I still think that a bullet fired on the moon would escape the moon's gravity. (assuming it is fired 'straight-up')
Still waiting on the mathematicians for this one.

[Moontanman]

Originally Posted by freeztar

Interesting. Thanks for the info.
My gun tech knowledge is obviously close to zilch.

I still think that a bullet fired on the moon would escape the moon's gravity. (assuming it is fired 'straight-up')
Still waiting on the mathematicians for this one.

The minimum orbital velocity of the moon is 0.968 km/s, escape velocity is 2.38 km/s as far as I know no regular gun has a muzzle velocity that high so a bullet fired from rifle would come back down just like it would on the earth. Objects can orbit the moon but the Earth makes a moon orbit unstable and such a orbit wouldn't last long in geological terms.

[Janus]

Originally Posted by Thunderbird

If one were to fire a rifle bullet from the surface of the moon would it go into orbit ?
The reason I ask is that I was thinking about asteroid strikes on the surface of the moon and wondering if it would allow for the formation of a ring like Saturns. So the real question is, if it is possible the moon had a ring around it in the past ? Would the weak gravity and electromagnetic field allow for such a formation ?

A rifle just doesn't have the muzzle velocity needed. Orbital velocity for the Moon is about 1.675 km/sec, and a high velocity rifle muzzle velocity would be under 1 km/sec. There are some tank guns that can have muzzle velocities of 1.8 km /sec and could put a shell into orbit.

Because the Moon has a lot of "lumpiness" in its mass distribution, there are no really stable long term orbits around it. A ring system would be short lived.

[Janus]

Just for the fun, I did a quick calculation as to how far a bullet fired at a 45° angle at 1000m/sec would travel, on the Moon. It works out to be a little over 784 km.

EDIT: I refined my numbers a little and came up with 735.899 km (I originally used a slightly too large radius for the Moon). I also determined that after taking the curvature of the Moon into account and the sub-orbital trajectory, you actually get the longest range firing at a angle of 39° which gives a distance of 752.889 km

[Moontanman]

Another way to look at planetary rings is that none of them are permanent features, they are transitory phenomena in geologic terms. Even the beautiful rings of Saturn will disappear eventually. Our moon cannot have a satellite that would last over geological time spans, as Janus has pointed the moon isn't even gravitationally and the Earth's gravity interferes with it's ability to hold on to satellites as well. It's is conceivable that a moon could orbit both the earth and the Moon or lie in one of the Lagrange points of the Earth moon system.