In October 1914,
Wilhelm von Siemens
suggested what became known as the
Siemens torpedo glider
, a wire-guided flying missile which would essentially have comprised a naval torpedo with an attached airframe. It was not intended to be flown into a target, but rather at a suitable altitude and position, a signal would be transmitted, causing the airframe components to detach from the torpedo which would then enter the water and continue towards its target. Guidance signals were to be transmitted through a thin copper wire, and guide flares were to be carried to help control.
Siemens-Schuckertwerke
was already occupied with remote controlled boats (the
FL-boats
or
Fernlenkboote
), and had some experience in this area. Flight testing was performed under the supervision of an engineer called Dorner from January 1915 onwards, using airships as carriers and different types of biplane and monoplane glider airframes to which a torpedo was fitted. The last test flight was performed on February 8, 1918.
It was planned to use the
Siemens-Schuckert R.VIII
bomber as a carrier craft, but the
Armistice
stopped the project.
[4]
During World War II, the first operational glide bombs were developed by the Germans as an anti-shipping weapon. Ships are typically very difficult to attack: a direct hit or an extremely near miss is needed to do any serious damage, and hitting a target as small as a ship was difficult in this period. At first
dive bombers
were used with some success in this role, but their successes were countered by ever-increasing anti-aircraft defenses on the
Royal Navy
ships they were attacking. By 1941, accurate bombing was as difficult as ever, with the added problem of evading anti-aircraft fire.
The German solution was the development of a number of glide bombs employing
radio control
guidance. One was created by fitting a control package on the rear of an otherwise standard bomb, starting with their 1400?kg
armor-piercing bomb
to create the
Ruhrstahl SD 1400
, commonly referred to as
Fritz
-X
. This weapon was designed specifically to pierce the deck armor of heavy cruisers and battleships. The bomb aimer dropped the bomb from high altitude while the aircraft was still approaching the ship, and guided it to impact with the target by sending commands to spoilers attached to its rear. This proved to be difficult to do, because as the bomb dropped toward the target it fell further behind the launch aircraft, eventually becoming difficult to see. This problem was solved by having the launch aircraft slow down and enter a climb to avoid overtaking the bomb as it fell.
In addition it proved difficult to properly guide the bomb to impact as the angle of descent changed, and if the bomb was not aimed accurately so as to end up roughly right over the target, there was little that could be done at later stages to fix the problem. Nevertheless, the Fritz X proved useful with crews trained on its use. In test drops from 8,000?m (26,000?ft), experienced bomb aimers could place half the bombs within a 15?m (49?ft 3?in) radius and 90% within 30?m (98?ft 5?in).
Design work started as early as 1939, and a version of the guidance package mounted to standard 500?kg bombs was tested in September 1940. It was found that the bomb was unable to penetrate a ship's armor, so changes were made to fit an armor-piercing warhead before the system finally entered service in 1943. The basic A-1 model was the only one to be produced in any number, but developments included the B model with a custom armor-piercing warhead, and the C model with a conical warhead which was designed to hit the water short of the ship and then travel a short distance underwater to hit the ship below the waterline. The guidance system for the Hs 293 series was the same as the Fritz-X unpowered munition; it used a
Funkgerat
FuG 203
Kehl
radio control transmitter with a single two-axis joystick in the deploying bomber, and an FuG 230
Straßburg
receiver in the munition.
Following the
capitulation
of Italy in 1943, Germany damaged the Italian battleship
Italia
and sank the
Roma
with Fritz-X bombs. Attacks were also made on the
USS?
Savannah
, causing much damage and loss of life.
HMS
Warspite
was hit by three Fritz-X, and although casualties were few, the ship had to be towed to
Malta
for repairs and was out of action for six months. The cruiser
USS?
Philadelphia
was very slightly damaged by several near misses from Fritz-X bombs. The light cruiser
HMS
Uganda
was also hit and put out of action for thirteen months as a result.
A more widely employed weapon was the
Henschel Hs 293
, which included wings and a rocket motor to allow the bomb to glide some distance away from the launch aircraft. This weapon was designed for use against thinly armored but highly defended targets such as convoy merchantmen or their escorting warships. When launched, a small liquid-fueled rocket fired to speed the weapon up and get it out in front of the releasing aircraft, which was flown to approach the target just off to one side. The bomb then dropped close to the water and glided in parallel to the launch aircraft, with the bomb aimer adjusting the flight left or right. As long as the bomb was dropped at roughly the right range so it did not run out of altitude while gliding in, the system was easy to use, at least against slow-moving targets.
The Hs 293 was first used operationally in the
Bay of Biscay
against RN and RCN destroyers, sloops and frigates. Its combat debut was made on August 25, 1943, when the sloop
HMS
Bideford
was slightly damaged by a missile which failed to fully detonate, but killed one crewman. Another sloop,
HMS
Landguard
, survived a near miss with slight damage. The Germans attacked again two days later, sinking
HMS
Egret
on August 27, 1943; they also seriously damaged
HMCS
Athabaskan
. Over one-thousand Allied soldiers died on 25 November 1943 when a Hs 293 sank the troopship
HMT?
Rohna
from Mediterranean
convoy KMF 26
.
[5]
Allied countermeasures
edit
Several defensive measures were implemented right away. Ships capable of maneuvering at high speed were instructed to make tight turns across the weapon's flight path in order to complicate the missile operator's efforts. Attacking aircraft were interdicted with air patrols and heavy-caliber
anti-aircraft weapons
, disrupting either the visual or radio links to the guided weapons. Smoke was used to hide ships at anchor. Allied aircraft also attacked the home bases of the special German units equipped with these weapons, primarily (
Gruppen
II and III of
Kampfgeschwader
100 and
Gruppe
II of
Kampfgeschwader
40
).
American, British and Canadian scientists also developed sophisticated
radio jammers
to disrupt the guidance signal. Ultimately nine different jamming systems were deployed in the
European theater
against these weapons. While early models proved inadequate, by the time the Allies were preparing for the invasion of France in 1944 more capable systems were deployed, and the success rate of guided weapons declined considerably. Even more important to the defeat of the weapons was Allied command of the airspace and the interception of incoming bombers by Allied fighter aircraft.
The Hs 293 was also used in August 1944 to attack bridges over the
River See
and
River Selume
at the southern end of the Cherbourg peninsula in an attempt to break US general
Patton
's advance, but this mission was unsuccessful. A similar mission against bridges on the
river Oder
, designed to slow the Soviet advance into Germany, was made in April 1945 but failed.
The Germans also experimented with
television
guidance systems on the Hs 293D models. The use was problematic ? as the bomb approaches the target, even tiny amounts of control input would cause the target to jump around the TV display, so much of the difficulty was in developing control systems that would become progressively less sensitive as the pilot required. A wire-guided version was also developed, but this Hs 293B variant was never deployed.
In 1939 Sir
Dennistoun Burney
and
Nevil Shute Norway
, worked together on an air-launched gliding torpedo, the "Toraplane", and a gliding bomb, "Doravane". Despite much work and many trials the Toraplane could not be launched with repeatable accuracy and it was abandoned in 1942.
The
US Army Air Force
started a wide-spanning development program of both glide bombs, known as "GB", and similar systems designed to fall more vertically, as "VG". Several models of both concepts were used in limited numbers during WWII.
The first to be used operationally was the
Aeronca
GB-1
, essentially an autopilot attached to a small glider airframe carrying a bomb. It was intended to allow the
8th Air Force
bombers to drop their payloads far from their targets and thus avoid having to overfly the most concentrated areas of
anti-aircraft artillery
fire. It was first used on 28 May 1944 against the Eifeltor marshalling yard in
Cologne
, but only 42 of 113 bombs released reached anywhere near the target; most "spun in and exploded 15 miles from the target... many of the batteries failed to hold [their] charge").
[6]
More advanced models in the GB series included the
television guided
GB-4
,
GB-5
,
GB-12
, and
GB-13
, which used
contrast-seekers
for anti-ship use, and the
command-guided
GB-8
, '
Azon
', '
Razon
', as well as the
infrared-guided
'Felix'
.
US Navy
glide bombs included the
'Bat'
and its earlier variant, the
'Pelican'
. The longer-range Bat used an active radar seeker and was used in the Pacific on August 13, 1944, but could not distinguish between targets in a cluttered environment and could be easily spoofed by even simple radar countermeasures.
[
citation needed
]
Only four examples of an experimental glide bomb, the '
Pratt-Read LBE
', were produced.