Thread View: sci.aeronautics
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Started by Brent R Phillips
Wed, 27 Jan 1993 04:20
***Help w/ aero HW(hodograph problem)***
Author: Brent R Phillips
Date: Wed, 27 Jan 1993 04:20
Date: Wed, 27 Jan 1993 04:20
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Hello, I am a undergraduate student in the aerospace program here at Ohio State. I am in the second quarter aero class and I am having a problem will a assingment question. Here's the problem I have a high aspect ratio, high altitude, powered sailplane. I need to construct a Hodograph(Vv vs. Vh). I am given that the THP = 600 HP at 50,000ft. The problem I am running into is that I have a equation to use for lbs. of thrust but, none for THP. I do not know a V(infinity) for a convertion. Nor do I know enough about the A/C to calculate R/C(max) for a given V(infinity). Please contact me! at bphillips@magnus.acs.ohio-state.edu or on the net. Thanks!!!!!(a frustrated student)
Re: ***Help w/ aero HW(hodograph problem)***
Author: Mark Drela
Date: Wed, 27 Jan 1993 23:51
Date: Wed, 27 Jan 1993 23:51
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In article <1993Jan27.042024.17478@magnus.acs.ohio-state.edu>, bphillip@magnus.acs.ohio-state.edu (Brent R Phillips) writes:
|> Here's the problem
|> I have a high aspect ratio, high altitude, powered sailplane. I need to
|> construct a Hodograph(Vv vs. Vh). I am given that the THP = 600 HP at
|> 50,000ft. The problem I am running into is that I have a equation to use for
|> lbs. of thrust but, none for THP. I do not know a V(infinity) for a
|> convertion. Nor do I know enough about the A/C to calculate R/C(max) for a
|> given V(infinity).
potential energy increase rate = excess thrust power
mgV = V (T - D)
v
mg = weight T = thrust D = drag
2 2
V = vertical velocity V = horizontal velocity V = speed = sqrt(V + V )
v h v h
If the flight path angle is shallow, i.e. V << V , you can approximate
v h
Lift = mg and V = V , so
h
V = V (T/mg - D/L)
v h
Mark Drela First Law of Aviation:
MIT Aero & Astro "Takeoff is optional, landing is compulsory"
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