The primary heavy bombers used by the United States Army Air Forces (USAAF) bomber squadrons of World War 2 (1939-1945) were the Consolidated B-24 "Liberator", the Boeing B-17 "Flying Fortress", and - towards the end of the war - the Boeing B-29 "Superfortress". All three were heavy hitters and hugely instrumental in bringing about an end to the war in favor of the Allies. In-between these classic designs there proved a slew of studies put forth by the usual big airplane-makers like the Glenn L. Martin Company which drew up their "Model 194" as a study.
The Model 194 appeared before the end of 1942 which, by this time, the advanced B-29 was still some months away from completing its development phase and entering service (arriving in 1944). The Model 194 was billed as a heavy bomber with inherently excellent range, able to carry an impressive war load (internally) over the vast distances required of the European and, more importantly, the Pacific campaigns.
The design was given an aerodynamically-refined shape with a rounded nose section (containing the flight deck with side-by-side seating), a tubular fuselage, and single-finned tail unit. The mainplanes were positioned near shoulder height and of straight design with tapering towards the curved tips. There was some noticeable sweepback (about 20 degrees) of the leading edges but none was used at the trailing edges. The tail unit used a large-area, rounded vertical fin (similar to that as used by the B-17 and B-29 by Boeing engineers) and these members were positioned on the fuselage below the fin itself. The general fuselage shape was of a stretched teardrop in which the rear was the tapered end. A retractable tricycle undercarriage would have been featured for ground-running and, considering the weight projection of this large aircraft, all of the legs were double-tired.
As a heavy bomber, the Model 194 would have carried four engines across four nacelles embedded (in pairs) at each wing mainplane. Rather interestingly, the bomber was drawn up with the engines arranged in "pusher" configuration, the propeller units seated behind the wing's trailing edge "pushing" the aircraft through the sky. Another interesting quality of the propulsion scheme was the proposed use of contra-rotating propellers at each engine for additional driving force (two three-bladed propeller units for a total of six blades at each engine. Another alternative design of this aircraft was to have the engines arranged in a more traditional "puller" / "tractor" approach.
For standard armament, the bomber was to have two remotely-controlled dorsal turrets seated inline, one fore and the other aft, and each position was to be outfitted with 4 x 0.50 caliber Browning Heavy Machine Guns (HMGs). Another remotely-controlled turret was positioned under the frontal section of the fuselage, also showcasing 4 x 0.50 caliber HMGs. The tail was home to 2 x 37mm autocannons to protect the aircraft's more vulnerable "six". This meant that the large aircraft would carry no fewer than twelve machine guns and two autocannons in four gun positions.
Using the B-29's capability as a guide, the bombload of Martin's Model 194 would have been in excess of 20,000lb, most likely between 20,000lb and 30,000lb. The bomb bay was to take up most of the internal volume of the aircraft and consist of two individual spaces at the ventral fuselage line.
Choice of engine make, model, and output power was not defined in the design study from what is known of this Martin proposal. Performance estimates can, however, be garnered by observing its contemporary, the aforementioned B-29 from Boeing, with a maximum speed going beyond 350 miles-per-hour, a range between 3,000 and 5,000 miles, and a service ceiling between 30,000 feet and 35,000 feet (requiring pressurization of crew spaces). Rate-of-climb would have been near 1,000 feet-per-minute.
Specifications included an overall length of 119 feet, a wingspan of 171 feet, and a height of 31 feet (author's estimate).
As with other proposed, advanced aircraft projects of the World War 2 period, the Martin Model 194 was not evolved beyond its design study, leaving its capabilities and impact on the war to the imagination.