《卫星工程》英文版 22 reentry

Reentry Col John e Keesee MIT Dept of Aeronautics and Astronautics November 25 2003

Reentry Col John E. Keesee MIT Dept of Aeronautics and Astronautics November 25, 2003

Background An ICBM with a range of 6500 miles has a stagnation temperature of 12, 000F, 2000 of hotter than the surface of the sun Calculations showed that the optimum design for structural strength, resistance to heating, and free flight stability was a long, needle nosed reentry body But it would vaporize during reentry

Background • An ICBM with a range of 6500 miles has a stagnation temperature of 12,000 ºF, 2000 ºF hotter than the surface of the sun • Calculations showed that the optimum design for structural strength, resistance to heating, and free flight stability was a long, needle nosed reentry body – But it would vaporize during reentry

Background Harry julian allen proposed an alternate solution, using pencil and paper Contradicted 50 years of research Suggested a blunt body would better put more of the heat the air and less into the body Strong bow shockwave

Background • Harry Julian Allen proposed an alternate solution, using pencil and paper – Contradicted 50 years of research – Suggested a blunt body would better put more of the heat the air and less into the body – Strong bow shockwave

Background Still needed unusual materials to survive the extreme heating conditions Heat sinks Copper, tungsten, molybdenum, beryllium · Shuttle ablators Teflon, nylon, fiberglass Mercury, Gemini, apollo, IcBMs

Background • Still needed unusual materials to survive the extreme heating conditions – Heat sinks • Copper, tungsten, molybdenum, beryllium • Shuttle – Ablators • Teflon, nylon, fiberglass • Mercury, Gemini, Apollo, ICBMs

Thermal barrier KE=-my2 2 Material Energy to Melting Vaporize Temperature BTU/b R Tungsten 1870 6500 Titanium 3865 3700 Beryllium oxide13, 400 2900 Graphite 28,700 6800

Thermal Barrier 2 2 1 2 2 c c V m Q KE mV Q = = = Material Energy to Vaporize BTU/lb Melting Temperature ºR Tungsten 1870 6500 Titanium 3865 3700 Beryllium oxi d e 13,400 2900 Graphite 28,700 6800

Stagnation Temperature CT=CT+v4/2 T=v/2C V(fps) To°R 10000 8.325 20.000 33.300 26.000 56.277

Stagnation Temperature o p p o p T V C C T C T V / 2 / 2 2 2 ∞ ∞ ∞ = = + V (fps) To ºR 10,000 8,325 20,000 33,300 26,000 56,277

How Much Heat Actually Enters the body

How Much Heat Actually Enters the Body

Reentry body shapes http://kittyhawk.publichq.nasagov/essay/ Evolution of Technoogy/reenti try/Tech19h tm

Reentry Body Shapes • http://kittyhawk.public.hq.nasa.gov/essay/ Evolution_of_Technoogy/reentry/Tech19.h tm