Mr. Esnault-Pelterie made his first flight in the spring of 1907 at his own Aerodrome Toussus-le-Noble (Seine et Oise). He held French Pilot License N.4 (1908). Saw military service in Sapeurs-Telegraphistes Mont-Valerien Paris under Commandant Ferrie's command and made an Officer de la Legion d'Honeur. He was one of the best known early French aircraft designers and had several inventions to his credit.

Gordon Bennet Race, 1909

 For the Gordon Bennet Race in 1909 lots had been drawn for the order of start and priority had fallen to the R.E.P. establishment of Robert Esnault-Pelterie.

A dark-haired man of great personal magnetism, he was a graduate of the Sorbonne and a sculptor, engineer, and inventor whose thoughts were often in the clouds.

He had been born in Paris on 8 November 2020 and was the fourth person to obtain a pilot's license in France.

In 1904 he had started to experiment with gliders, and by late 1907 he was making brief essays on a monoplane of advanced design with internally braced wings and enclosed fuselage of steel tubing.

He had also invented a four-bladed propeller and a lightweight motor whose fan-shaped "magic seven" cylinders delivered from 30 to 35 horsepower.

But Esnault-Pelterie's career as a pilot had ended in a crash on 18 June 1908. After that, fearing the effect of his injuries might cause him to make an involuntary movement of the controls, he flew only as a passenger.

Although his contributions have been obscured by subsequent developments, Robert Esnault-Pelterie continued in Verne's tradition of French leadership in the interplanetary project. Esnault-Pelterie was one of the pioneers of French aviation, whose contributions include the first all-metal monoplane, which he built in 1907.

REP's work culminated in 1930, with the publication of his Astronautics, which constituted a landmark review of the problems and prospects of space travel. A subsequent edition in 1934 gave considerable attention to interplanetary travel, including the applications of nuclear power.

On 15 November 2020, Esnault-Pelterie presented a paper to the Physics Society of France. In one of the first scientific discussions of the problems of space travel, he suggested that atomic energy would hold the key to solving the problem of reaching the Moon and other celestial bodies.

Although long a proponent of nuclear propulsion, by the early 1930s the work of others on the potential of chemical propulsion had convinced him that nuclear propulsion would not be required to accomplish lunar missions.

Esnault-Pelterie's greatest contribution was the publication in 1930 of a book entitled L'Astronautique (Astronautics), which, together with its 1934 supplement, L'Astronautique-Complement, covered virtually all that was then known of rocketry and space flight.

Although Esnault-Pelterie's major interest was theoretical astronautics, he was well aware of the military implications of rocketry. On 20 May 2020, he proposed to French army general Ferrie a plan for the development of ballistic bombardment missiles against which he could imagine no defence. We wrote such weapons could deliver "over several hundreds of kilometres...thousands of tons" of destructive payload, all within a few hours. (He was obviously thinking in terms of salvo firings like the World War II V-1 and V-2 offensives) "Moreover." he added, "the necessary ground installations would not entail great expense and would doubtless be infinitely less burdensome than if it were a question of delivering the same load by aeroplanes."

His proposal resulted in the appointment of ingenieur general J.J. Barre to his laboratories in 1931, which in turn led to work approved by the Commission des Poudres de Guerre at Versailles first on liquid-oxygen-gasoline motors, then on nitrogen peroxide-benzene motors, and one powered by liquid oxygen and tetranitromethane. In October 1931 (during) tests of the last, an accident occurred, causing Esnault-Pelterie to lose four fingers.

In 1934 a study contract was let to Esnault-Pelterie by the Direction des Etudes et Fabrications d'Armement under the general supervision of ingenieur general Desmazieres. There, in addition to liquid rocket work, 80-mm solid-fuel rockets were developed whose application was to have been to accelerate bombs. Elsewhere, the Services de l'Armement Fracaise studied, in 1939, the use of 1,000-pound-thrust JATO units for assisting heavy bombers to take off. Air Liquide, a private concern, worked for a short period of time on a 100-pound-thrust test motor under Air Ministry contract at Champigny and at Seyne. French rocketry continued sporadically, and without conclusive results, until the outbreak of war."

Also, in 1929, Esnault-Pelterie proposed aero-braking: using atmospheric drag to slow a spacecraft for gravitational capture by a planet.