double or nothing sonic booms

Why is there no sonic booms during ascent?





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Lynndel Humphreys wrote:

Why is there no sonic booms during ascent?
^are

There are.
They are just much less audible than on descent.
The boom actually gets focussed in some places (out to sea) as the
ascent track curves somewhat.
Most of the "boom" goes sideways, and not down, so it doesn't
hit the ground.


--
http://inquisitor.i.am/ | | Ian Stirling.
---------------------------+-------------------------+--------------------------
Windows 2000, software for next millenia. latin pun alert - Ian Stirling.

From Ian Stirling:
Lynndel Humphreys wrote:

Why is there no sonic booms during ascent?
^are

There are.
They are just much less audible than on descent.
The boom actually gets focussed in some places (out to sea) as the
ascent track curves somewhat.
Most of the "boom" goes sideways, and not down, so it doesn't
hit the ground.

Funny to think of sonic booms in terms of being "audible". The one's
I've experienced were *FELT* much more than heard. Might just as well
be called...

Sonic bombs.


~ CT

On 6 Oct 2003 23:03:41 -0700, (Stuf4)
wrote:

From Ian Stirling:
Lynndel Humphreys wrote:

Why is there no sonic booms during ascent?
^are

There are.
They are just much less audible than on descent.
The boom actually gets focussed in some places (out to sea) as the
ascent track curves somewhat.
Most of the "boom" goes sideways, and not down, so it doesn't
hit the ground.

Funny to think of sonic booms in terms of being "audible". The one's
I've experienced were *FELT* much more than heard. Might just as well
be called...

Sonic bombs.

During launch, would a sonic boom be all that noticeable anyway,
considering the tremendous noise the shuttle engines are making?

-- David

Ian Stirling wrote:

Lynndel Humphreys wrote:

Why is there no sonic booms during ascent?
^are

There are.
They are just much less audible than on descent.
The boom actually gets focussed in some places (out to sea) as the
ascent track curves somewhat.
Most of the "boom" goes sideways, and not down, so it doesn't
hit the ground.




Right, at Mach 1 the shock wave is moving away from the ground (in the same
direction as the vehicle), not towards it. So, it won't hit the ground.

Later on when the vehicle is flying more parallel to the ground and the
shockwave is more of a cone, it's very high. Plus, it's moving away from
land. You would have to be in the Atlantic to hear it.

Craig Fink

Funny to think of sonic booms in terms of being "audible". The one's
I've experienced were *FELT* much more than heard. Might just as well
be called...

Has the military ever tried using such noise as a weapon?

Stuf4 wrote:

From Ian Stirling:
Lynndel Humphreys wrote:

Why is there no sonic booms during ascent?
^are

There are.
They are just much less audible than on descent.
The boom actually gets focussed in some places (out to sea) as the
ascent track curves somewhat.
Most of the "boom" goes sideways, and not down, so it doesn't
hit the ground.

Funny to think of sonic booms in terms of being "audible". The one's
I've experienced were *FELT* much more than heard. Might just as well
be called...

Sonic bombs.

Boom, not bomb.

Takeoff, full power, climb subsonically to 20 or 30 thousand feet. Point
the nose down toward the ground to get a gravity assist to help the
underpowered aircraft break through the sound barrier. That invisible wall
(plane not cone) of sound at Mach 1 that must be penetrated. Then continue
to climb supersonically to cruise altitude. Want to fly the fastest
intercept possible? It would be best to minimize the subsonic portion of
flight. Pushing the nose over as soon as possible to push through the sound
barrier and get moving supersonically. The aircraft may spend more time
near Mach 1, and it's at a lower altitiude, but time to target is minimized.

To me this profile seems like a good way to send a "BIG" sonic boom towards
the ground. Want to make it louder, fly at Mach 1 longer, adding energy to
the boom that's collecting at the nose of the aircraft.

Talk about crazy, a bunch of government employees (Military fighter pilots)
rattling windows around the country. Instead of addressing the problem with
the offending branch of government that was rattling windows, a different
branch of government outlaws flying supersonic over the United States? Then
gives the offending branch of government an exemption? While, at the same
time, limiting the non-offending commercial Concord's usefulness and
profitablity?

The prohibition on supersonic flight over the US needs to be repealed.

Craig Fink

With Columbia's damaged wing, might detect a change in the sonic pattern, if
this data was available.




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From David Ball:
On 6 Oct 2003 23:03:41 -0700, (Stuf4)
wrote:

Funny to think of sonic booms in terms of being "audible". The one's
I've experienced were *FELT* much more than heard. Might just as well
be called...

Sonic bombs.

During launch, would a sonic boom be all that noticeable anyway,
considering the tremendous noise the shuttle engines are making?

I don't see how the exhaust pressure waves could get in front of the
sonic boom generated from the front of the stack, so even if the
magnitude of the exhaust pressure waves were higher (which I would
agree with, as a guess) I expect that the leading sonic boom would
still be -noticeable-.


For anyone interested...

Here's a bit to help understand why so much energy gets transmitted in
a sonic boom compared to, say, a bomb blast:

A point source will radiate in three dimensions. When a bomb blasts,
the pressure wave expands spherically and the energy dissipates
similar to those 1/r^2 forces that have been discussed here in recent
days.

Sonic booms are not generated from a point source. They are generated
from the "line source" that is the vehicle's flight path. This
constrains propagation of the pressure wave to a two dimensional
expansion, not three. Energy dissipation therefore is along the lines
of 1/r, not 1/r^2.

The worst case pressure wave transmission occurs with the waveguide.
Here the wave is physically constrained so that expansion occurs in
one dimension. Energy will tend to remain constant over distance:
~1, and not 1/r or 1/r^2. A common example of 1-d pressure wave
propagation is the barrel of a gun, and this explains why the muzzle
velocity of a rifle is so much higher than the bullet from a handgun.
As soon as the bullet leaves the barrel, the pressure wave goes from
1-d expansion to 3-d expansion.


~ CT

Hallerb wrote:


Funny to think of sonic booms in terms of being "audible". The one's
I've experienced were *FELT* much more than heard. Might just as well
be called...

Has the military ever tried using such noise as a weapon?

Yes, they make the biggest one out of hydrogen. If it's an air burst, the
shock wave reflects off the ground, making the boom twice as big at ground
level.

Craig Fink