How do we get supersonic bullets?
$begingroup$
I recently answered a question on the WorldBuilding forum about grenades and bullets. One of the things that came up was that I argued smokeless powder in a rifle round could detonate, but was challenged on that. Commenters said that smokeless powder only deflagrates during normal use.
This, however, leaves me with a question. How can we accelerate a bullet to supersonic speeds using only a sonic speed pressure wave? As the bullet approaches the speed of sound, shouldn't the pressure wave be pushing the bullet less effectively? It strikes me that a bullet traveling at the speed of sound should not be able to be pushed by a pressure wave at the speed of sound.
How does this work?
pressure acoustics projectile explosions shock-waves
edited Feb 4 at 16:14
Qmechanic♦
105k121921207
asked Feb 4 at 14:50
Cort AmmonCort Ammon
23.3k34778
$endgroup$
add a comment |
$begingroup$
I recently answered a question on the WorldBuilding forum about grenades and bullets. One of the things that came up was that I argued smokeless powder in a rifle round could detonate, but was challenged on that. Commenters said that smokeless powder only deflagrates during normal use.
This, however, leaves me with a question. How can we accelerate a bullet to supersonic speeds using only a sonic speed pressure wave? As the bullet approaches the speed of sound, shouldn't the pressure wave be pushing the bullet less effectively? It strikes me that a bullet traveling at the speed of sound should not be able to be pushed by a pressure wave at the speed of sound.
How does this work?
pressure acoustics projectile explosions shock-waves
edited Feb 4 at 16:14
Qmechanic♦
105k121921207
asked Feb 4 at 14:50
Cort AmmonCort Ammon
23.3k34778
$endgroup$
4
$begingroup$
Black powder can send a bullet supersonic, too. My understanding is that it deflagrates.
$endgroup$
– Don Branson
Feb 4 at 19:45
2
$begingroup$
Deflagration (Lat: de + flagrare, "to burn down") is subsonic combustion propagating through heat transfer; hot burning material heats the next layer of cold material and ignites it. Most "fires" found in daily life, from flames to explosions such as that of Black powder, are deflagrations. This differs from detonation, which propagates supersonically through shock waves, decomposing a substance extremely quickly. wikipedia.
$endgroup$
– Captain Giraffe
Feb 5 at 2:10
add a comment |
$begingroup$
I recently answered a question on the WorldBuilding forum about grenades and bullets. One of the things that came up was that I argued smokeless powder in a rifle round could detonate, but was challenged on that. Commenters said that smokeless powder only deflagrates during normal use.
This, however, leaves me with a question. How can we accelerate a bullet to supersonic speeds using only a sonic speed pressure wave? As the bullet approaches the speed of sound, shouldn't the pressure wave be pushing the bullet less effectively? It strikes me that a bullet traveling at the speed of sound should not be able to be pushed by a pressure wave at the speed of sound.
How does this work?
pressure acoustics projectile explosions shock-waves
edited Feb 4 at 16:14
Qmechanic♦
105k121921207
asked Feb 4 at 14:50
Cort AmmonCort Ammon
23.3k34778
$endgroup$
I recently answered a question on the WorldBuilding forum about grenades and bullets. One of the things that came up was that I argued smokeless powder in a rifle round could detonate, but was challenged on that. Commenters said that smokeless powder only deflagrates during normal use.
This, however, leaves me with a question. How can we accelerate a bullet to supersonic speeds using only a sonic speed pressure wave? As the bullet approaches the speed of sound, shouldn't the pressure wave be pushing the bullet less effectively? It strikes me that a bullet traveling at the speed of sound should not be able to be pushed by a pressure wave at the speed of sound.
How does this work?
pressure acoustics projectile explosions shock-waves
pressure acoustics projectile explosions shock-waves
edited Feb 4 at 16:14
Qmechanic♦
105k121921207
asked Feb 4 at 14:50
Cort AmmonCort Ammon
23.3k34778
edited Feb 4 at 16:14
Qmechanic♦
105k121921207
asked Feb 4 at 14:50
Cort AmmonCort Ammon
23.3k34778
edited Feb 4 at 16:14
Qmechanic♦
105k121921207
edited Feb 4 at 16:14
Qmechanic♦
105k121921207
edited Feb 4 at 16:14
Qmechanic♦
105k121921207
105k121921207
asked Feb 4 at 14:50
Cort AmmonCort Ammon
23.3k34778
asked Feb 4 at 14:50
Cort AmmonCort Ammon
23.3k34778
asked Feb 4 at 14:50
Cort AmmonCort Ammon
23.3k34778
23.3k34778
4
$begingroup$
Black powder can send a bullet supersonic, too. My understanding is that it deflagrates.
$endgroup$
– Don Branson
Feb 4 at 19:45
2
$begingroup$
Deflagration (Lat: de + flagrare, "to burn down") is subsonic combustion propagating through heat transfer; hot burning material heats the next layer of cold material and ignites it. Most "fires" found in daily life, from flames to explosions such as that of Black powder, are deflagrations. This differs from detonation, which propagates supersonically through shock waves, decomposing a substance extremely quickly. wikipedia.
$endgroup$
– Captain Giraffe
Feb 5 at 2:10
add a comment |
4
$begingroup$
Black powder can send a bullet supersonic, too. My understanding is that it deflagrates.
$endgroup$
– Don Branson
Feb 4 at 19:45
2
$begingroup$
Deflagration (Lat: de + flagrare, "to burn down") is subsonic combustion propagating through heat transfer; hot burning material heats the next layer of cold material and ignites it. Most "fires" found in daily life, from flames to explosions such as that of Black powder, are deflagrations. This differs from detonation, which propagates supersonically through shock waves, decomposing a substance extremely quickly. wikipedia.
$endgroup$
– Captain Giraffe
Feb 5 at 2:10
4
4
$begingroup$
Black powder can send a bullet supersonic, too. My understanding is that it deflagrates.
$endgroup$
– Don Branson
Feb 4 at 19:45
$begingroup$
Black powder can send a bullet supersonic, too. My understanding is that it deflagrates.
$endgroup$
– Don Branson
Feb 4 at 19:45
2
2
$begingroup$
Deflagration (Lat: de + flagrare, "to burn down") is subsonic combustion propagating through heat transfer; hot burning material heats the next layer of cold material and ignites it. Most "fires" found in daily life, from flames to explosions such as that of Black powder, are deflagrations. This differs from detonation, which propagates supersonically through shock waves, decomposing a substance extremely quickly. wikipedia.
$endgroup$
– Captain Giraffe
Feb 5 at 2:10
$begingroup$
Deflagration (Lat: de + flagrare, "to burn down") is subsonic combustion propagating through heat transfer; hot burning material heats the next layer of cold material and ignites it. Most "fires" found in daily life, from flames to explosions such as that of Black powder, are deflagrations. This differs from detonation, which propagates supersonically through shock waves, decomposing a substance extremely quickly. wikipedia.
$endgroup$
– Captain Giraffe
Feb 5 at 2:10
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
The speed of sound increases with increasing pressure. Assuming ideal behaviour the relationship is:
$$ v = sqrt{gammafrac{P}{rho}} $$
or equivalently:
$$ v = sqrt{frac{gamma RT}{M}} $$
where $M$ is the molar mass.
In a gun barrel just after the charge has gone off the gas is under very high pressure and very hot, so the speed of sound is much higher than under ambient conditions.
answered Feb 4 at 15:55
John RennieJohn Rennie
276k44549792
$endgroup$
3
$begingroup$
Re, "very high pressure", see en.wikipedia.org/wiki/Chamber_pressure
$endgroup$
– Solomon Slow
Feb 4 at 17:41
2
$begingroup$
And SAAMI recommended chamber pressures.
$endgroup$
– TKK
Feb 5 at 15:16
add a comment |
$begingroup$
Deflagration means that the combustion moves through the fuel slower than the speed of sound in the fuel. It doesn't say anything about the speed of the resulting gas, or how it compares to the speed of sound in that gas (and the speed of sound in solids is generally higher than that of gasses). The gas that is released from the combustion isn't at equilibrium, so properties such as "pressure", "temperature", and thus "speed of sound" aren't fully defined for it.
answered Feb 4 at 17:34
AcccumulationAcccumulation
2,566312
$endgroup$
1
$begingroup$
This does limit the combustion process though. If the medium is moving faster than the flame front, unburned fuel downstream of the flame front isn't ever burned. This is a huge oversimplification. There is a lot of nuance to this speed relative to what etc, but the upshot is that unconfined there is a limit on the speed of the resulting gas dependent on among other factors the speed of combustion.
$endgroup$
– drjpizzle
Feb 6 at 14:47
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "151"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f458828%2fhow-do-we-get-supersonic-bullets%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
The speed of sound increases with increasing pressure. Assuming ideal behaviour the relationship is:
$$ v = sqrt{gammafrac{P}{rho}} $$
or equivalently:
$$ v = sqrt{frac{gamma RT}{M}} $$
where $M$ is the molar mass.
In a gun barrel just after the charge has gone off the gas is under very high pressure and very hot, so the speed of sound is much higher than under ambient conditions.
answered Feb 4 at 15:55
John RennieJohn Rennie
276k44549792
$endgroup$
3
$begingroup$
Re, "very high pressure", see en.wikipedia.org/wiki/Chamber_pressure
$endgroup$
– Solomon Slow
Feb 4 at 17:41
2
$begingroup$
And SAAMI recommended chamber pressures.
$endgroup$
– TKK
Feb 5 at 15:16
add a comment |
$begingroup$
The speed of sound increases with increasing pressure. Assuming ideal behaviour the relationship is:
$$ v = sqrt{gammafrac{P}{rho}} $$
or equivalently:
$$ v = sqrt{frac{gamma RT}{M}} $$
where $M$ is the molar mass.
In a gun barrel just after the charge has gone off the gas is under very high pressure and very hot, so the speed of sound is much higher than under ambient conditions.
answered Feb 4 at 15:55
John RennieJohn Rennie
276k44549792
$endgroup$
3
$begingroup$
Re, "very high pressure", see en.wikipedia.org/wiki/Chamber_pressure
$endgroup$
– Solomon Slow
Feb 4 at 17:41
2
$begingroup$
And SAAMI recommended chamber pressures.
$endgroup$
– TKK
Feb 5 at 15:16
add a comment |
$begingroup$
The speed of sound increases with increasing pressure. Assuming ideal behaviour the relationship is:
$$ v = sqrt{gammafrac{P}{rho}} $$
or equivalently:
$$ v = sqrt{frac{gamma RT}{M}} $$
where $M$ is the molar mass.
In a gun barrel just after the charge has gone off the gas is under very high pressure and very hot, so the speed of sound is much higher than under ambient conditions.
answered Feb 4 at 15:55
John RennieJohn Rennie
276k44549792
$endgroup$
The speed of sound increases with increasing pressure. Assuming ideal behaviour the relationship is:
$$ v = sqrt{gammafrac{P}{rho}} $$
or equivalently:
$$ v = sqrt{frac{gamma RT}{M}} $$
where $M$ is the molar mass.
In a gun barrel just after the charge has gone off the gas is under very high pressure and very hot, so the speed of sound is much higher than under ambient conditions.
answered Feb 4 at 15:55
John RennieJohn Rennie
276k44549792
answered Feb 4 at 15:55
John RennieJohn Rennie
276k44549792
answered Feb 4 at 15:55
John RennieJohn Rennie
276k44549792
answered Feb 4 at 15:55
John RennieJohn Rennie
276k44549792
276k44549792
3
$begingroup$
Re, "very high pressure", see en.wikipedia.org/wiki/Chamber_pressure
$endgroup$
– Solomon Slow
Feb 4 at 17:41
2
$begingroup$
And SAAMI recommended chamber pressures.
$endgroup$
– TKK
Feb 5 at 15:16
add a comment |
3
$begingroup$
Re, "very high pressure", see en.wikipedia.org/wiki/Chamber_pressure
$endgroup$
– Solomon Slow
Feb 4 at 17:41
2
$begingroup$
And SAAMI recommended chamber pressures.
$endgroup$
– TKK
Feb 5 at 15:16
3
3
$begingroup$
Re, "very high pressure", see en.wikipedia.org/wiki/Chamber_pressure
$endgroup$
– Solomon Slow
Feb 4 at 17:41
$begingroup$
Re, "very high pressure", see en.wikipedia.org/wiki/Chamber_pressure
$endgroup$
– Solomon Slow
Feb 4 at 17:41
2
2
$begingroup$
And SAAMI recommended chamber pressures.
$endgroup$
– TKK
Feb 5 at 15:16
$begingroup$
And SAAMI recommended chamber pressures.
$endgroup$
– TKK
Feb 5 at 15:16
add a comment |
$begingroup$
Deflagration means that the combustion moves through the fuel slower than the speed of sound in the fuel. It doesn't say anything about the speed of the resulting gas, or how it compares to the speed of sound in that gas (and the speed of sound in solids is generally higher than that of gasses). The gas that is released from the combustion isn't at equilibrium, so properties such as "pressure", "temperature", and thus "speed of sound" aren't fully defined for it.
answered Feb 4 at 17:34
AcccumulationAcccumulation
2,566312
$endgroup$
1
$begingroup$
This does limit the combustion process though. If the medium is moving faster than the flame front, unburned fuel downstream of the flame front isn't ever burned. This is a huge oversimplification. There is a lot of nuance to this speed relative to what etc, but the upshot is that unconfined there is a limit on the speed of the resulting gas dependent on among other factors the speed of combustion.
$endgroup$
– drjpizzle
Feb 6 at 14:47
add a comment |
$begingroup$
Deflagration means that the combustion moves through the fuel slower than the speed of sound in the fuel. It doesn't say anything about the speed of the resulting gas, or how it compares to the speed of sound in that gas (and the speed of sound in solids is generally higher than that of gasses). The gas that is released from the combustion isn't at equilibrium, so properties such as "pressure", "temperature", and thus "speed of sound" aren't fully defined for it.
answered Feb 4 at 17:34
AcccumulationAcccumulation
2,566312
$endgroup$
1
$begingroup$
This does limit the combustion process though. If the medium is moving faster than the flame front, unburned fuel downstream of the flame front isn't ever burned. This is a huge oversimplification. There is a lot of nuance to this speed relative to what etc, but the upshot is that unconfined there is a limit on the speed of the resulting gas dependent on among other factors the speed of combustion.
$endgroup$
– drjpizzle
Feb 6 at 14:47
add a comment |
$begingroup$
Deflagration means that the combustion moves through the fuel slower than the speed of sound in the fuel. It doesn't say anything about the speed of the resulting gas, or how it compares to the speed of sound in that gas (and the speed of sound in solids is generally higher than that of gasses). The gas that is released from the combustion isn't at equilibrium, so properties such as "pressure", "temperature", and thus "speed of sound" aren't fully defined for it.
answered Feb 4 at 17:34
AcccumulationAcccumulation
2,566312
$endgroup$
Deflagration means that the combustion moves through the fuel slower than the speed of sound in the fuel. It doesn't say anything about the speed of the resulting gas, or how it compares to the speed of sound in that gas (and the speed of sound in solids is generally higher than that of gasses). The gas that is released from the combustion isn't at equilibrium, so properties such as "pressure", "temperature", and thus "speed of sound" aren't fully defined for it.
answered Feb 4 at 17:34
AcccumulationAcccumulation
2,566312
answered Feb 4 at 17:34
AcccumulationAcccumulation
2,566312
answered Feb 4 at 17:34
AcccumulationAcccumulation
2,566312
answered Feb 4 at 17:34
AcccumulationAcccumulation
2,566312
2,566312
1
$begingroup$
This does limit the combustion process though. If the medium is moving faster than the flame front, unburned fuel downstream of the flame front isn't ever burned. This is a huge oversimplification. There is a lot of nuance to this speed relative to what etc, but the upshot is that unconfined there is a limit on the speed of the resulting gas dependent on among other factors the speed of combustion.
$endgroup$
– drjpizzle
Feb 6 at 14:47
add a comment |
1
$begingroup$
This does limit the combustion process though. If the medium is moving faster than the flame front, unburned fuel downstream of the flame front isn't ever burned. This is a huge oversimplification. There is a lot of nuance to this speed relative to what etc, but the upshot is that unconfined there is a limit on the speed of the resulting gas dependent on among other factors the speed of combustion.
$endgroup$
– drjpizzle
Feb 6 at 14:47
1
1
$begingroup$
This does limit the combustion process though. If the medium is moving faster than the flame front, unburned fuel downstream of the flame front isn't ever burned. This is a huge oversimplification. There is a lot of nuance to this speed relative to what etc, but the upshot is that unconfined there is a limit on the speed of the resulting gas dependent on among other factors the speed of combustion.
$endgroup$
– drjpizzle
Feb 6 at 14:47
$begingroup$
This does limit the combustion process though. If the medium is moving faster than the flame front, unburned fuel downstream of the flame front isn't ever burned. This is a huge oversimplification. There is a lot of nuance to this speed relative to what etc, but the upshot is that unconfined there is a limit on the speed of the resulting gas dependent on among other factors the speed of combustion.
$endgroup$
– drjpizzle
Feb 6 at 14:47
add a comment |
Thanks for contributing an answer to Physics Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f458828%2fhow-do-we-get-supersonic-bullets%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
4
$begingroup$
Black powder can send a bullet supersonic, too. My understanding is that it deflagrates.
$endgroup$
– Don Branson
Feb 4 at 19:45
2
$begingroup$
Deflagration (Lat: de + flagrare, "to burn down") is subsonic combustion propagating through heat transfer; hot burning material heats the next layer of cold material and ignites it. Most "fires" found in daily life, from flames to explosions such as that of Black powder, are deflagrations. This differs from detonation, which propagates supersonically through shock waves, decomposing a substance extremely quickly. wikipedia.
$endgroup$
– Captain Giraffe
Feb 5 at 2:10