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B52 bomber; converting thrust to horse power...?

B52 bomber; converting thrust to horse power...? - Physics Forum

B52 bomber; converting thrust to horse power...? - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


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  #1  
Old 06-01-2004, 12:47 AM
**bg**
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Default B52 bomber; converting thrust to horse power...?



There was an experimental aircraft developed by Germany in WW2, the Ju390
V2, which flew non-stop from Europe to US east coast and back again. It's
ceiling was in the low 20k.

It had six engines developing 1700 hp each, currently under discussion at
the moderated group soc.history.war.world-war-ii, subject 'German Bombers to
NYC'.

I want to compare the 390's power to the 17000 pounds thrust available from
each of the eight Pratt & Whitney engines TF33-P-3/103 turbofans on the B52.

How does this 17000 pounds translate to hp?

BTW, a most fascinating site for the B52, especially in the charts appearing
about 2/3 of the way down is
[Only registered users see links. ]

TIA.

-bg-
[Only registered users see links. ]


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  #2  
Old 06-01-2004, 02:48 PM
DaveL
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Default B52 bomber; converting thrust to horse power...?

There is no direct conversion between hp and thrust. These are two
different things. It basically depends on the efficiency of the propellers.
That would help determine how many pounds of thrust they would make.

Horse Power is the indication of how much power the engine makes. Pounds of
thrust is how much pushing force the engine imparts to the aircraft. As you
can see, the difference between the two is the propeller for the prop
engine.

DaveL


"**bg**" <[Only registered users see links. ]> wrote in message
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  #3  
Old 06-01-2004, 05:37 PM
Mark Fergerson
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Default B52 bomber; converting thrust to horse power...?

**bg** wrote:

<snippage>


Dimensional analysis. In what units (M,L,T etc) are the
two quantities expressed?

Remember that pounds of thrust is a force, and that you
have to take the drag (another force) on the aircraft into
account. (There are four forces operating on an aircraft;
lift vs. weight, and thrust vs. drag.)

The hp applied as thrust is only useful in telling you
how fast the aircraft will move at a constant velocity _if_
you know the drag (assuming lift and weight also balance).

Mark L. Fergerson

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  #4  
Old 06-03-2004, 06:41 AM
wavelength
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Default B52 bomber; converting thrust to horse power...?


**bg** <info@thelittlecanadaheadphoneband.ca> wrote in message
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to
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B52.
appearing

Nevertheless the ' effective power ' can be calculated by knowing how heavy
the planes are and how fast they accelerate
although this takes into the opposing forces of drag.

Best






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  #5  
Old 06-03-2004, 11:07 PM
tadchem
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Default B52 bomber; converting thrust to horse power...?


"**bg**" <[Only registered users see links. ]> wrote in message
news:JmQuc.632435$oR5.519689@pd7tw3no...

Wrong.

[Only registered users see links. ]

Only one Ju390 was ever completed and flown, (Prototype V1) in the bomber
configuration. A second was started but not completed. The designed range
was 9700 km in the Reconnaisance version, but that was ever actually
performed. Given a bomb payload, the Ju390 version 1 would never have
completed the Berlin-New York round trip. Given only one completed test
flight, the "service ceiling" was never established. It probably would have
been limited by Germany's available human factors technology - how high
could the *crew* stand to go and remain for 20-30 hours (without pressure
suits and with limited O2 availability)?

The revelation that Germany *was* working on a long-range heavy bomber that
*could* have reached NYC from Berlin caused a lot of sweaty American palms,
however:
[Only registered users see links. ]


Make that 1970 hp.

from
B52.

It doesn't. Apples aren't oranges. Horsepower is "power" - energy times
time. Thrust is force - energy per unit distance. Given a good hydraulic
jack I could generate 17000 pounds of thrust with my personal 1/4 horsepower
body. Just don't expect it *fast*.


Tom Davidson
Richmond, VA


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  #6  
Old 06-04-2004, 09:06 PM
Gordon
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Default B52 bomber; converting thrust to horse power...?

On Thu, 3 Jun 2004 19:07:32 -0400, "tadchem" [snip]
I think what he is talking about is this constant force from each
of 8 engines, sustained at some constant velocity and altitude
(cruising conditions). This would be force X distance/time, and
would equate to power. The choice of units could give an answer
in hp. 33,000 foot pounds per minute is one hp.

Or, stated differently, 33,000 pounds applied to an object, in
the direction of its velocity, and moving it at one foot per
minute is producing one hp.

One engine, producing 16,500 pounds of thrust and moving an
object 2 feet per minute would equate to one hp.

All 8 engines moving this object 2 feet per minute would produce
8 hp.

Now, increase the speed to 36,900 feet per minute (450 mph) and
you get 147,600 hp equivalent...unless I miss keyed my
calculator.
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  #7  
Old 06-05-2004, 08:23 PM
The Boerg
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Default B52 bomber; converting thrust to horse power...?


"**bg**" <[Only registered users see links. ]> wrote in message
news:JmQuc.632435


Thrust and power ratings are probably done at a standard altitude and
velocity. The two are not constant and depend on many variable. But the
instantaneous power of an engine is basically the thrust it produces
multiplied by the planes air speed.

17000 pounds at 300 mph would equate to 13,600 hp. I don't think they push
that hard, but that's an example.


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