Re: How Rockets Differ From Jets

in article 1129541964.017517.213760@xxxxxxxxxxxxxxxxxxxxxxxxxxxx, tomcat at
jlavine@xxxxxxxxxxxxx wrote on 10/17/05 2:39 AM:

> George Evans wrote:
>
>> Airfoils don't magically create energy. The only source of energy are the
>> motors. A good airfoil can *minimize* the added energy necessary to achieve
>> orbit over that necessary for a vertical launch. But flying to orbit is
>> still going to cost you more.
>
> Your 'frictionless surface' though experiment is interesting and I shall give
> it some thought. And, yes, nothing magically creates energy.
>
> Yet, I am still intrigued by the B-29 that won WWII.
>
> With an engine thrust of 1/10 it's takeoff weight it could fly thousands of
> miles, drop tons of bombs, and return. It's thrust to weight ratio only
> increased a little when it dropped the bombs, but with substantially less than
> a 1:1 thrust to weight it would fly it's mission again and again.
>
> Nothing magically creates energy but far less thrust than weight could take
> this plane to 20,000 feet and hold it there for hours. This is 'interesting'
> too.

All of the energy from the engines of the cruising B-29 went to counteract
drag. When the engines are throttled up, the extra energy goes into
increasing height. The climb is very slow compared to a rocket launch but
the amount of extra energy necessary to climb to 20,000 feet is the same
used to lift the vehicle vertically to that height.

The reason it seems confusing is that a B-29 flying at 350 mph at 20,000
feet has a very very small energy compared to orbital energy.

George Evans

.

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