Autori: R. D. Rugescu
Editorial: 56th IAC Paper D4.P.04 “Infrastructure”, 17-21 October 2005, Fukuoka, Japan, 2005.
Robert H. Goddard was the first to observe, by physical reasoning, that, if a rational
ascent speed policy is followed, a rocket vehicle might reach a given altitude with a
minimal starting mass, meaning with the least possible fuel consumption. He
published his observations in 1919, suggesting a variational approach could be used
to find the solution, but gave any. This is the famous Goddard problem of rocket
ascent. Only four years later, Hermann Oberth had independently published a
similar discussion on the optimal atmospheric ascent and gave in 1929 the first,
approximate solution of the problem, strikingly resembling the later, more evolved
ones. The German mathematician Georg Hamel formulated in the meantime (1927)
the problem in strong variational terms, but incomplete due to the assumption of
drag continuity (partial problem), assimilated up to the present by all eventual
researchers. Tsien and Evans are the first to publish a detailed variational solution
of the partial Goddard problem in 1951. A stream of developments in atmospheric
ascent optimization burst, with none of them escaping from the limiting circle of drag
continuity at burn out, although additional discontinuous phenomena were further
identified and valuable approaches were rendered again by the German school.
Hundreds of sophisticated contributions in flight control appeared. It happens
however that the full solution with discontinuous drag is still missing at the distance
of 86 years after the first formulation of the optimal rocket ascent by Goddard.
Cuvinte cheie: History of Astronautics