Hans Jacob Reissner was a German aeronautical engineer whose avocation

Avocation

An avocation is an activity that one engages in as a hobby outside one's main occupation. There are many examples of people whose professions were the ways that they made their livings, but for whom their activities outside of their workplaces were their true passions in life...

 was mathematical physics. During World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 he was awarded the Iron Cross

Iron Cross

The Iron Cross is a cross symbol typically in black with a white or silver outline that originated after 1219 when the Kingdom of Jerusalem granted the Teutonic Order the right to combine the Teutonic Black Cross placed above a silver Cross of Jerusalem....

 second class (for civilians) for his pioneering work on aircraft design.

Background

During the Third Reich he was able to work in the aircraft industry although he did not have an Arierzeugnis. In 1938 he emigrated from the country to which he had contributed so much. He taught at the Illinois Institute of Technology

Illinois Institute of Technology

Illinois Institute of Technology, commonly called Illinois Tech or IIT, is a private Ph.D.-granting university located in Chicago, Illinois, with programs in engineering, science, psychology, architecture, business, communications, industrial technology, information technology, design, and law...

 (1938-44) and the Polytechnic Institute of Brooklyn (1944-54).

Curiously, it was this engineer, rather than a physicist or mathematician, who first solved Einstein's equation for the metric of a charged point mass. His Reissner-Nordstrom metric

Reissner-Nordström metric

In physics and astronomy, the Reissner–Nordström metric is a static solution to the Einstein-Maxwell field equations, which corresponds to the gravitational field of a charged, non-rotating, spherically symmetric body of mass M.-The metric:...

 demonstrated that an electron has a naked singularity rather that an event horizon

Event horizon

In general relativity, an event horizon is a boundary in spacetime beyond which events cannot affect an outside observer. In layman's terms it is defined as "the point of no return" i.e. the point at which the gravitational pull becomes so great as to make escape impossible. The most common case...

.

His son - Eric Reissner - developed the Reissner shear-deformation plate theory.