Terminal velocity of bombs?

BackToNormal wrote:

William Hughes wrote:

On Mon, 22 Sep 2003 15:20:05 +1200, in rec.aviation.military
(BackToNormal) wrote:

Was half paying attention to a TV doco on the Dambusters a few mins ago
and thought I heard the narrator say the Earthquake bomb designed by
Barnes Wallis broke the sound barrie on its way down.
Comments anyone?

Methinks you may have misinterpereted something.

Nope. It was on the National Geographic channel in a prog called
"Dambusters".

Iron bombs have the same
terminal velocity as everything else, about 135 mph, IIRC.

Not really, but my ears pricked up at the sound barrier ref. By luck, my
vcr was running for the first part of the show, and here's the relevant
bit.

"In the Spring of 1941, he (Barnes Wallis) was ready to unveil a bomb
which was as unique as it was powerful, the 10 ton earthquake bomb. An
aerodynamic masterpiece, it would break the sound barrier on its
descent, while its offset tailfins would make it spin like a giant
dart".

There was no a/c capable of carrying it, so he had already designed a
six engined bomber which never eventuated because the Lancaster was on
the way, and the earthquake bomb design never saw fruition. The program
was a fascinating story on development of the cylindrical bombs which
breached the Ruhr dams, but that sound barrier reference had me
thinking. Responses (some) from other posters indicate it was/is
possible.

Actually the 12,- 22,- 44,000lb "earthquake" bombs were built, and the
12,- and 22,000 lb weapons were used in combat, dropped from
Landcasters. They were supersonic, I seem to recall something like 1,200
mph or so?

On Mon, 22 Sep 2003 21:44:48 GMT, Juvat
wrote:

Ed Rasimus remarked:

Beside the supersonic freefall that Joe did, he also got a MiG in SEA
and spent some time as a guest of the North Vietnamese.

That POW part had a great deal to do with duplicating the MiG kill
part...Fangs out, Hair on Fire...

The reports of his free-fall records...scary. Mas Cajones.

Juvat

Dare I say it was a "Triple-Nickel" thing. Lots of competition.

Something strange about what a MiG airborne will do to your common
sense. I always said I was happy killing SAM sites, never had no
argument with no MiG. Live and let live was my philosophy. Then one
day a pair of -21s came blowing through between my element and the
Weasels. Didn't take but a second. I called blow the tanks and stroked
the burners. Larry Cary, on my wing, called "six is clear" and we had
our coifures fully engulfed in a heartbeat.

Unfortunately, Madden and Ritchie interposed themselves between us and
the designated morts for the day. Back to rooting around in the dirt.

In article ,
BackToNormal writes
"In the Spring of 1941, he (Barnes Wallis) was ready to unveil a bomb
which was as unique as it was powerful, the 10 ton earthquake bomb. An
aerodynamic masterpiece, it would break the sound barrier on its
descent, while its offset tailfins would make it spin like a giant
dart".

According to Brickhill in The Dam Busters, the offset fins were added
after the test Tallboy went supersonic, wobbling off target as it did
so. Barnes offset the fins to stabilise it (the original reason for the
back spin on the 'bouncing bomb').

The Tallboy and Grand Slam were extremely aerodynamic and built to very
tight tolerances. Tirpitz received three direct hits and at least a
dozen very near misses, from bombs dropped from 16,000ft.

--
John

steve gallacci wrote:

BackToNormal wrote:

William Hughes wrote:

On Mon, 22 Sep 2003 15:20:05 +1200, in rec.aviation.military
(BackToNormal) wrote:

Was half paying attention to a TV doco on the Dambusters a few mins ago
and thought I heard the narrator say the Earthquake bomb designed by
Barnes Wallis broke the sound barrie on its way down.
Comments anyone?

Methinks you may have misinterpereted something.

Nope. It was on the National Geographic channel in a prog called
"Dambusters".

Iron bombs have the same
terminal velocity as everything else, about 135 mph, IIRC.

Not really, but my ears pricked up at the sound barrier ref. By luck, my
vcr was running for the first part of the show, and here's the relevant
bit.

"In the Spring of 1941, he (Barnes Wallis) was ready to unveil a bomb
which was as unique as it was powerful, the 10 ton earthquake bomb. An
aerodynamic masterpiece, it would break the sound barrier on its
descent, while its offset tailfins would make it spin like a giant
dart".

There was no a/c capable of carrying it, so he had already designed a
six engined bomber which never eventuated because the Lancaster was on
the way, and the earthquake bomb design never saw fruition. The program
was a fascinating story on development of the cylindrical bombs which
breached the Ruhr dams, but that sound barrier reference had me
thinking. Responses (some) from other posters indicate it was/is
possible.

Actually the 12,- 22,- 44,000lb "earthquake" bombs were built, and the
12,- and 22,000 lb weapons were used in combat, dropped from
Landcasters.

True. Where I wrote "never saw fruition" I should have written "was
sidelined". Instead, he designed the spherical bomb and refined that
into the cylindrical bomb used to breach the dams.

The Barnes Wallis Trust site quotes Wallis -- "After the dams had been
burst (1943) , Sir Wilfred Freeman, the Chief Executive at the Ministry
of Aircraft Production, asked me if I remembered my mad idea of a 10-ton
bomb which I had put up in 1939. I said 'Yes, indeed, Sir Wilfred, I
do'. 'Well', he said, 'how soon could you let me have one?' I said
'June, July, August, September, October, five months if I have all the
labour available in Sheffield'".

In 1944 the RAF got its first 'earthquake' bomb, the Tallboy, which at
12,000lbs was a scaled down version of the 10 tonner. 854 Tallboys were
dropped by Bomber Command Lancasters. The 10 ton Grand Slam bomb
followed in 1945.

ronh

--
"People do not make decisions on facts, rather,
how they feel about the facts" Robert Consedine

In article ,
BackToNormal writes
True. Where I wrote "never saw fruition" I should have written "was
sidelined". Instead, he designed the spherical bomb and refined that
into the cylindrical bomb used to breach the dams.

Apparently the diameter of the spherical bomb with the right amount of
RDX would have been too large to fit under a Lanc. It was changed to a
cylinder to reduce the diameter and the spinning used to give it
gyroscopic precision so it hit the water horizontal each time.

--
John

Apparently the diameter of the spherical bomb with the right amount of
RDX would have been too large to fit under a Lanc. It was changed to a
cylinder to reduce the diameter and the spinning used to give it
gyroscopic precision so it hit the water horizontal each time.

--
John

I believe it was changed to a cylinder because the sphere would sometimes skip
off to one side.


Dan, U. S. Air Force, retired

John Halliwell wrote:

In article ,
BackToNormal writes
"In the Spring of 1941, he (Barnes Wallis) was ready to unveil a bomb
which was as unique as it was powerful, the 10 ton earthquake bomb. An
aerodynamic masterpiece, it would break the sound barrier on its
descent, while its offset tailfins would make it spin like a giant
dart".

According to Brickhill in The Dam Busters, the offset fins were added
after the test Tallboy went supersonic, wobbling off target as it did
so. Barnes offset the fins to stabilise it (the original reason for the
back spin on the 'bouncing bomb').

Interesting. The program I saw showed a design drawing incorporating the
offset tailfins. I'm sure the program makers were saying THAT design was
the one presented by Barnes to Whitehall in 1941 (and he had proposed as
a weapon in 1939).

ronh
--
"People do not make decisions on facts, rather,
how they feel about the facts" Robert Consedine

John Halliwell wrote:

In article ,
BackToNormal writes
True. Where I wrote "never saw fruition" I should have written "was
sidelined". Instead, he designed the spherical bomb and refined that
into the cylindrical bomb used to breach the dams.

Apparently the diameter of the spherical bomb with the right amount of
RDX would have been too large to fit under a Lanc. It was changed to a
cylinder to reduce the diameter and the spinning used to give it
gyroscopic precision so it hit the water horizontal each time.

Phew John. I opened a can of worms here by mentioning the program I saw.
It said the bomb was designed to hit the dam wall, bounce away, and then
the gyroscopic motion would claw the bomb back to and down against the
wall to detonate at predetermined depth.

The spin was primarily designed to work the same as spin put on a golf
ball to keep the bomb against the wall, and not as a trajectory aid.
No?

ronh


--
"People do not make decisions on facts, rather,
how they feel about the facts" Robert Consedine

In article ,
BackToNormal writes
Phew John. I opened a can of worms here by mentioning the program I saw.
It said the bomb was designed to hit the dam wall, bounce away, and then
the gyroscopic motion would claw the bomb back to and down against the
wall to detonate at predetermined depth.

It's hard to be sure exactly what led to what (cause & effect) of the
various techniques used in designing the bomb. My understanding (mostly
gained from Brickhill), is that originally Barnes used a sphere to
ensure each bounce would present the same surface to the water. He found
it would be too big and stretched it to a cylinder, adding spin to
stabilise it. Not sure if he tried forward spin or not, but he found
back spin allowed it to 'skip' off the water. The crawling down the dam
wall was discovered during testing as an additional benefit.

Highball, the smaller anti-shipping version which didn't go into
service, was pretty much spherical (only the very ends were flat to
allow it to be attached to the spinning gear).

It sounds like there are different accounts, and the whole thing was
probably muddied by wartime secrecy (the 1954 film was not allowed to
mention anything of the back-spin as that was still secret). It is also
possible that later editions of The Dam Busters might have more
information as more was released.

The spin was primarily designed to work the same as spin put on a golf
ball to keep the bomb against the wall, and not as a trajectory aid.
No?

Different accounts suggest different developments, but at the end of the
day, they're all correct when it comes to the operation of the bomb.
There is also the possibility of each account being tailored to a given
audience or compiled to fit the 'established history'. Brickhill's
account is probably incomplete or inaccurate in many ways.

A good, more recent account is given in 'The Dambusters Raid', one of
the 'Cassell Military Paperbacks' series (sorry haven't got more details
to hand). It clears up a number of points and tries to identify where
many of the 'missing' aircraft were shot down.

Just out of interest, what was the angle Nat Geo used in the programme,
seems a bit out of character (I only read the magazine, haven't seen any
of their TV progs)?

--
John

There's a Tall Boy at at the USAF museume at Dayton. There's a 44,000
pound T12 standing door guard at the Aberdeen Proving Ground Museum
building. ISTR both have canted fins. (I trust both are inert shapes.)
Quite a few 'drop models' of weighted models of proposed aircraft went
supersonic when released at high altitude. Telemetry relayed what
happened on the way down. ISTR the Miles M52 was tested this way.
FWIW Mk 82 slicks separate just fine and hit the target accurately
when released supersonic - (G).
Walt BJ