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Posted by Nomen Nescio on July 17, 2005, 10:10 am
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Its stated the depletion sensors cut off the engines at 5% fuel remaining
because if the tanks were allowed to run dry the engines might explode.
Why is that? When a motorcycle fuel tank runs down, the engine just
sputters and quits when the carburetor fuel bowl level drops, with no
damage done. Can't they make a rocket engine more robust?
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Posted by Scott J on July 17, 2005, 10:57 am
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show/hide quoted text
> Its stated the depletion sensors cut off the engines at 5% fuel remaining
> because if the tanks were allowed to run dry the engines might explode.
> Why is that? When a motorcycle fuel tank runs down, the engine just
> sputters and quits when the carburetor fuel bowl level drops, with no
> damage done. Can't they make a rocket engine more robust?
The real problem, I suspect, is not the engines exploding rether it's the
turbopumps.
The high pressure fuel turbopump runs at 34,290rpm, boosts the fuel pressure
from 303psi to 5945psi, and operates at the temperature of liquid hydrogen
(IIRC -422F). Can you imagine what the overspeed would be like if the pump
suddenly went dry while operating at full power?
Is there anything on a motorcycle that even remotely operates under these
conditions?
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Posted by Dan Foster on July 17, 2005, 5:18 pm
Please log in for more thread options show/hide quoted text
>> Its stated the depletion sensors cut off the engines at 5% fuel remaining
>> because if the tanks were allowed to run dry the engines might explode.
>> Why is that? When a motorcycle fuel tank runs down, the engine just
>> sputters and quits when the carburetor fuel bowl level drops, with no
>> damage done. Can't they make a rocket engine more robust?
> The real problem, I suspect, is not the engines exploding rether it's the
> turbopumps.
Yep, you'd be correct.
Direct quote from:
http://www.theandyzone.com/launchzone/se104.htm
One of the most critical thing the crew would do for the rest
of powered flight would be to monitor MPS propellant remaining.
When flying on a single SSME, if the propellant depletes before
MECO is commanded, the SSME stands a chance of blowing up.
It's a function of NPSP or Net Positive Suction Pressure.
This is the "head pressure" at the inlet to a pump, and in this
case the NPSP on the High Pressure Oxidizer Turbopump is the
limiting factor.
NPSP is proportional to the engine’s power level, e.g., the
higher the engine power level or throttle setting the more NPSP
required to keep the pump from cavitating.
Cavitating the pump will destroy the engine and probably the Orbiter.
-Dan
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Posted by Brian Gaff on July 17, 2005, 5:26 pm
Please log in for more thread options I often wondered about how such pumps are primed. Presumably, someone has to
be damn sure there are no gas inclusions in the line before they start them
up or there could be a nasty mess.
Brian
--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email: briang1@blueyonder.co.uk
______________________________________________________________________________________________________________
show/hide quoted text
>> Its stated the depletion sensors cut off the engines at 5% fuel remaining
>> because if the tanks were allowed to run dry the engines might explode.
>> Why is that? When a motorcycle fuel tank runs down, the engine just
>> sputters and quits when the carburetor fuel bowl level drops, with no
>> damage done. Can't they make a rocket engine more robust?
> The real problem, I suspect, is not the engines exploding rether it's the
> turbopumps.
> The high pressure fuel turbopump runs at 34,290rpm, boosts the fuel
> pressure from 303psi to 5945psi, and operates at the temperature of liquid
> hydrogen (IIRC -422F). Can you imagine what the overspeed would be like
> if the pump suddenly went dry while operating at full power?
> Is there anything on a motorcycle that even remotely operates under these
> conditions?
>
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Posted by Mike Dennis on July 17, 2005, 5:54 pm
Please log in for more thread options This actually happened in an SSME test early in the program, IIRC.
________
show/hide quoted text
>> Its stated the depletion sensors cut off the engines at 5% fuel remaining
>> because if the tanks were allowed to run dry the engines might explode.
>> Why is that? When a motorcycle fuel tank runs down, the engine just
>> sputters and quits when the carburetor fuel bowl level drops, with no
>> damage done. Can't they make a rocket engine more robust?
> The real problem, I suspect, is not the engines exploding rether it's the
> turbopumps.
> The high pressure fuel turbopump runs at 34,290rpm, boosts the fuel
> pressure from 303psi to 5945psi, and operates at the temperature of liquid
> hydrogen (IIRC -422F). Can you imagine what the overspeed would be like
> if the pump suddenly went dry while operating at full power?
> Is there anything on a motorcycle that even remotely operates under these
> conditions?
>
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> because if the tanks were allowed to run dry the engines might explode.
> Why is that? When a motorcycle fuel tank runs down, the engine just
> sputters and quits when the carburetor fuel bowl level drops, with no
> damage done. Can't they make a rocket engine more robust?