Terminal velocity of bombs?

[BackToNormal]

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?

ronh

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

[William Hughes]

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

[Juvat]

After an exhausting session with Victoria's Secret Police,
BackToNormal blurted out:

>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?

Try http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html

[Juvat]

After an exhausting session with Victoria's Secret Police,
BackToNormal blurted out:

>Comments anyone?

Also try this http://hypertextbook.com/facts/JianHuang.shtml

[Juvat]

BackToNormal asked:

>Comments anyone?

How 'bout this
http://www.saltspring.com/brochmann/math/Ballistic/Ball-1.00.html

[Kerryn Offord]

When dropped from (IIRC) 40,000' it was supposed to become supersonic
(original design spec). As it was dropped from a much lower altitude
(<20,000'??) it didn't(?).

The Tallboys and Grandslams had a well designed ballistic shape and
could accelerate to these velocities

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?
>
> ronh
>

[Thomas Schoene]

"William Hughes" > wrote in message

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

I think you're the one misinterpreting. Terminal velocity varies widely for
different objects -- it's a function of density, drag, and weight.

http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html

--�
Tom Schoene Replace "invalid" with "net" to e-mail
"If brave men and women never died, there would be nothing
special about bravery." -- Andy Rooney (attributed)

[[email protected]]

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

Hey guys...lookit that feather fallin there!...is it ever friggen
moven !!
--

-Gord.

[Scott Ferrin]

On Mon, 22 Sep 2003 00:02:55 -0500, 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. Iron bombs have the same
>terminal velocity as everything else, about 135 mph, IIRC.
>


Think a bit about how gravity works and what "terminal velocity"
actually *is*. A human might fall about that fast because of their
density and drag. And that's at low altitude. Someone bailing out at
high altitude where the air is thinner will fall much faster.
Something with less drag or higher density will too.

[Ed Majden]

"Kerryn Offord"
> The Tallboys and Grandslams had a well designed ballistic shape and
> could accelerate to these velocities
>
Seems to me I heard somewhere that a high altitude parachutist was going
to try and break the sound barrier! Anyone know anything about this?

Ed

[Juvat]

After an exhausting session with Victoria's Secret Police "Ed Majden"
blurted out:

> Seems to me I heard somewhere that a high altitude parachutist was going
>to try and break the sound barrier! Anyone know anything about this?

Try this
http://observer.guardian.co.uk/international/story/0,6903,754911,00.html

[WDA]

An analysis I did some years ago showed that a Mk-84 dropped from about
30,000 ft and about 500 knots will become just about supersonic before
striking the ground. However, that analysis did not account for the
relatively small lift force occurring as the bomb centerline transitions
from horizontal to near vertical during the bomb's flight.

WDA

end

"BackToNormal" > wrote in message
zz...
> 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?
>
> ronh
>
> --
> "People do not make decisions on facts, rather,
> how they feel about the facts" Robert Consedine

[Ed Majden]

"Juvat"
> After an exhausting session with Victoria's Secret Police "Ed Majden"
> blurted out:
>
I don't get this "Victoria's Secret Police" crack! Please enlighten
me????

[Juvat]

Ed Majden implored me thusly:

>I don't get this "Victoria's Secret Police" crack! Please enlighten
>me????

Oy...imagine if you will that somebody is interrogating you, perhaps
the Gestapo, perhaps the KGB. No a pretty thought.

Now imagine scantily clad lingerie models trying to get something from
you...

YMMV

[BackToNormal]

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.

ronh


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

[Yeff]

On Mon, 22 Sep 2003 19:43:07 GMT, Ed Majden wrote:

> I don't get this "Victoria's Secret Police" crack! Please enlighten
> me????

http://www.victoriassecret.com/
http://www.loc.gov/exhibits/archives/secr.html

-Jeff B.
yeff at erols dot com

[Ed Rasimus]

On Mon, 22 Sep 2003 17:06:26 GMT, Juvat >
wrote:

>After an exhausting session with Victoria's Secret Police "Ed Majden"
>blurted out:
>
>> Seems to me I heard somewhere that a high altitude parachutist was going
>>to try and break the sound barrier! Anyone know anything about this?
>
>Try this
>http://observer.guardian.co.uk/international/story/0,6903,754911,00.html

And, that link mentions that Joe Kittinger did it around 30 years ago.
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.

Ooops. I've fallen into the trap that Ed Majden set. Here's yet
another claim that either a Yank or a Russian did everything worth
doing first!

Yep, Kittinger did it already.

[Andrew Chaplin]

"Ed Majden" > wrote in message
...
>
> "Juvat"
> > After an exhausting session with Victoria's Secret Police "Ed
Majden"
> > blurted out:
> >
> I don't get this "Victoria's Secret Police" crack! Please
enlighten
> me????

Ed, you really need to get out more. :^)
--
Andrew Chaplin
SIT MIHI GLADIUS SICUT SANCTO MARTINO
(If you're going to e-mail me, you'll have to get "yourfinger." out.)

[Juvat]

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

[Paul J. Adam]

In message >,
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".
>
>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.

It was developed, fielded and used (from that very Lancaster)- the
ten-ton "Grand Slam" and the smaller "Tallboy" were useful niche weapons
with a few famous successes to their names..


--
When you have to kill a man, it costs nothing to be polite.
W S Churchill

Paul J. Adam MainBox<at>jrwlynch[dot]demon{dot}co(.)uk

[steve gallacci]

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?

[Ed Rasimus]

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.

[John Halliwell]

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

[BackToNormal]

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

[John Halliwell]

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

[B2431]

>
>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

[BackToNormal]

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

[BackToNormal]

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

[John Halliwell]

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

[Walt BJ]

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

[John Mullen]

Walt BJ wrote:
> 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

http://www.johnmullen.org.uk/aerospce/pics/bombs.htm

[Matt]

The bomb was always intended to have a backspin, as that would enable it to
bounce over the torpedo nets. When it hit the wall of the dam, the spin
would ensure that it remained there as it sank to it's detonation depth,
rather than bounce away from it.

Wallis intended that the bomb would be a sphere, but a cylinder was the
easiest shape to manufacture out of sheet metal. To maintain the spherical
shape, they initally surrounded the cylinder with a wooden sphere, but this
disintergrated the instant the first test bomb hit the water. No matter ...
the cylinder bounced just as well!

"John Halliwell" > wrote in message
...
> 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

[BackToNormal]

John Halliwell > wrote:

> 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)?

I've had another look at the bit of the Nat Geo program I managed to
tape.

They do say the spin was put on the bomb to make it claw its way back to
the dam wall (after its initial bounce off) and there were animations to
demonstrate this. There was no mention of spin helping to control bounce
or direction. Some of the original footage showed one of the bombs
hitting and going from backspin, to sideways, to forwards spin. Their
hair must have turned white while they were experimenting.

Regarding backspin, I'd have thought forward gyroscopic spin would have
worked better against the dam wall (which probably explains why I am not
a scientist).

After the prog finished, my wife (avid low handicap golfer) commented
that she was unaware that golf balls have dimples as a result of
Wallis' experiments with dimples on his spherical bombs. Actually, I
thought the program suggested that too, but golf balls had dimples a
long time before Wallis did his thing. Maybe we both misinterpreted the
program.

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