NASA's RS-25 Engines shut down time
$begingroup$
As a follow up to my other question about RS-25's ramp-up time, I was wondering what would be the ramp-down times for the RS-25, i.e. what would be the time that takes to go from 100% thrust to 0% thrust.
Also, were the engines "allowed" to shut down as a result of running out of propellant? Or were they issued a shut down command with some propellant left?
nasa sls ssme
asked 7 hours ago
Mitch99Mitch99
674
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Mitch99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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add a comment |
$begingroup$
As a follow up to my other question about RS-25's ramp-up time, I was wondering what would be the ramp-down times for the RS-25, i.e. what would be the time that takes to go from 100% thrust to 0% thrust.
Also, were the engines "allowed" to shut down as a result of running out of propellant? Or were they issued a shut down command with some propellant left?
nasa sls ssme
asked 7 hours ago
Mitch99Mitch99
674
New contributor
Mitch99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
As a follow up to my other question about RS-25's ramp-up time, I was wondering what would be the ramp-down times for the RS-25, i.e. what would be the time that takes to go from 100% thrust to 0% thrust.
Also, were the engines "allowed" to shut down as a result of running out of propellant? Or were they issued a shut down command with some propellant left?
nasa sls ssme
asked 7 hours ago
Mitch99Mitch99
674
New contributor
Mitch99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
As a follow up to my other question about RS-25's ramp-up time, I was wondering what would be the ramp-down times for the RS-25, i.e. what would be the time that takes to go from 100% thrust to 0% thrust.
Also, were the engines "allowed" to shut down as a result of running out of propellant? Or were they issued a shut down command with some propellant left?
nasa sls ssme
nasa sls ssme
asked 7 hours ago
Mitch99Mitch99
674
New contributor
Mitch99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 7 hours ago
Mitch99Mitch99
674
New contributor
Mitch99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 7 hours ago
Mitch99Mitch99
674
New contributor
Mitch99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 7 hours ago
Mitch99Mitch99
674
asked 7 hours ago
Mitch99Mitch99
674
674
New contributor
Mitch99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Mitch99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Mitch99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
(This is all for shuttle, not SLS)
Running the engine out of propellant was a Big Bad Thing. There were sensors in the External Tank (for hydrogen) and in the orbiter feedlines (for oxygen) that would trigger a shutdown if the sensor registered dry. The placement of the sensors was such that the engine should shut down before they ran out of prop.
Normally the engines shut down on commands issued by guidance and the system had a small amount of prop remaining. (note: carrying extra prop to orbit wastes payload capacity, carrying too little means you don't go to space)
(reference)
Here's some simple linear data for shutdowns from different power levels. This is for the (rather old) FPL version of the SSME (see the taxonomy of the SSME in my answer to Which STS mission raised the normal engine throttle above 100%, and what change to the SSME made that possible?) but should be somewhat representative. It's based on data supplied for use in simulator models at Johnson Space Center. This is chamber pressure data but thrust should be roughly proportionate. Y axis in psi, X axis in seconds.
answered 7 hours ago
Organic MarbleOrganic Marble
58.4k3160250
$endgroup$
2
$begingroup$
Excellent, thanks! Roughly the same as ramp-up times... Great, I don't need to change my code. However, I now have to put "shut down engine" checks for "fuel level < 1%" instead of " == 0%...
$endgroup$
– Mitch99
6 hours ago
add a comment |
$begingroup$
were the engines "allowed" to shut down as a result of running out of propellant? Or were they issued a shut down command with some propellant left?
Shutdown was commanded when the appropriate trajectory was reached.
Even in multistage rockets, rocket engines are not run to complete depletion of propellant. The fuel/oxidizer mix ratio must be closely controlled to avoid damage to the engine; if the fuel ran out early the mixture ratio would go ox-rich, increasing combustion chamber temperature. The "trickling" flow of the last little bit of propellant would also produce rough combustion, which could be damaging. As Tristan notes, the turbopump would also be catastrophically damaged if propellant flow trickled.
answered 7 hours ago
Russell BorogoveRussell Borogove
87.1k3291376
$endgroup$
4
$begingroup$
Not just that, but if the inlet of a turbopump impeller runs dry, it would overspeed with blinding alacrity.
$endgroup$
– Tristan
7 hours ago
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
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active
oldest
votes
$begingroup$
(This is all for shuttle, not SLS)
Running the engine out of propellant was a Big Bad Thing. There were sensors in the External Tank (for hydrogen) and in the orbiter feedlines (for oxygen) that would trigger a shutdown if the sensor registered dry. The placement of the sensors was such that the engine should shut down before they ran out of prop.
Normally the engines shut down on commands issued by guidance and the system had a small amount of prop remaining. (note: carrying extra prop to orbit wastes payload capacity, carrying too little means you don't go to space)
(reference)
Here's some simple linear data for shutdowns from different power levels. This is for the (rather old) FPL version of the SSME (see the taxonomy of the SSME in my answer to Which STS mission raised the normal engine throttle above 100%, and what change to the SSME made that possible?) but should be somewhat representative. It's based on data supplied for use in simulator models at Johnson Space Center. This is chamber pressure data but thrust should be roughly proportionate. Y axis in psi, X axis in seconds.
answered 7 hours ago
Organic MarbleOrganic Marble
58.4k3160250
$endgroup$
2
$begingroup$
Excellent, thanks! Roughly the same as ramp-up times... Great, I don't need to change my code. However, I now have to put "shut down engine" checks for "fuel level < 1%" instead of " == 0%...
$endgroup$
– Mitch99
6 hours ago
add a comment |
$begingroup$
(This is all for shuttle, not SLS)
Running the engine out of propellant was a Big Bad Thing. There were sensors in the External Tank (for hydrogen) and in the orbiter feedlines (for oxygen) that would trigger a shutdown if the sensor registered dry. The placement of the sensors was such that the engine should shut down before they ran out of prop.
Normally the engines shut down on commands issued by guidance and the system had a small amount of prop remaining. (note: carrying extra prop to orbit wastes payload capacity, carrying too little means you don't go to space)
(reference)
Here's some simple linear data for shutdowns from different power levels. This is for the (rather old) FPL version of the SSME (see the taxonomy of the SSME in my answer to Which STS mission raised the normal engine throttle above 100%, and what change to the SSME made that possible?) but should be somewhat representative. It's based on data supplied for use in simulator models at Johnson Space Center. This is chamber pressure data but thrust should be roughly proportionate. Y axis in psi, X axis in seconds.
answered 7 hours ago
Organic MarbleOrganic Marble
58.4k3160250
$endgroup$
2
$begingroup$
Excellent, thanks! Roughly the same as ramp-up times... Great, I don't need to change my code. However, I now have to put "shut down engine" checks for "fuel level < 1%" instead of " == 0%...
$endgroup$
– Mitch99
6 hours ago
add a comment |
$begingroup$
(This is all for shuttle, not SLS)
Running the engine out of propellant was a Big Bad Thing. There were sensors in the External Tank (for hydrogen) and in the orbiter feedlines (for oxygen) that would trigger a shutdown if the sensor registered dry. The placement of the sensors was such that the engine should shut down before they ran out of prop.
Normally the engines shut down on commands issued by guidance and the system had a small amount of prop remaining. (note: carrying extra prop to orbit wastes payload capacity, carrying too little means you don't go to space)
(reference)
Here's some simple linear data for shutdowns from different power levels. This is for the (rather old) FPL version of the SSME (see the taxonomy of the SSME in my answer to Which STS mission raised the normal engine throttle above 100%, and what change to the SSME made that possible?) but should be somewhat representative. It's based on data supplied for use in simulator models at Johnson Space Center. This is chamber pressure data but thrust should be roughly proportionate. Y axis in psi, X axis in seconds.
answered 7 hours ago
Organic MarbleOrganic Marble
58.4k3160250
$endgroup$
(This is all for shuttle, not SLS)
Running the engine out of propellant was a Big Bad Thing. There were sensors in the External Tank (for hydrogen) and in the orbiter feedlines (for oxygen) that would trigger a shutdown if the sensor registered dry. The placement of the sensors was such that the engine should shut down before they ran out of prop.
Normally the engines shut down on commands issued by guidance and the system had a small amount of prop remaining. (note: carrying extra prop to orbit wastes payload capacity, carrying too little means you don't go to space)
(reference)
Here's some simple linear data for shutdowns from different power levels. This is for the (rather old) FPL version of the SSME (see the taxonomy of the SSME in my answer to Which STS mission raised the normal engine throttle above 100%, and what change to the SSME made that possible?) but should be somewhat representative. It's based on data supplied for use in simulator models at Johnson Space Center. This is chamber pressure data but thrust should be roughly proportionate. Y axis in psi, X axis in seconds.
answered 7 hours ago
Organic MarbleOrganic Marble
58.4k3160250
edited 7 hours ago
answered 7 hours ago
Organic MarbleOrganic Marble
58.4k3160250
answered 7 hours ago
Organic MarbleOrganic Marble
58.4k3160250
answered 7 hours ago
Organic MarbleOrganic Marble
58.4k3160250
58.4k3160250
2
$begingroup$
Excellent, thanks! Roughly the same as ramp-up times... Great, I don't need to change my code. However, I now have to put "shut down engine" checks for "fuel level < 1%" instead of " == 0%...
$endgroup$
– Mitch99
6 hours ago
add a comment |
2
$begingroup$
Excellent, thanks! Roughly the same as ramp-up times... Great, I don't need to change my code. However, I now have to put "shut down engine" checks for "fuel level < 1%" instead of " == 0%...
$endgroup$
– Mitch99
6 hours ago
2
2
$begingroup$
Excellent, thanks! Roughly the same as ramp-up times... Great, I don't need to change my code. However, I now have to put "shut down engine" checks for "fuel level < 1%" instead of " == 0%...
$endgroup$
– Mitch99
6 hours ago
$begingroup$
Excellent, thanks! Roughly the same as ramp-up times... Great, I don't need to change my code. However, I now have to put "shut down engine" checks for "fuel level < 1%" instead of " == 0%...
$endgroup$
– Mitch99
6 hours ago
add a comment |
$begingroup$
were the engines "allowed" to shut down as a result of running out of propellant? Or were they issued a shut down command with some propellant left?
Shutdown was commanded when the appropriate trajectory was reached.
Even in multistage rockets, rocket engines are not run to complete depletion of propellant. The fuel/oxidizer mix ratio must be closely controlled to avoid damage to the engine; if the fuel ran out early the mixture ratio would go ox-rich, increasing combustion chamber temperature. The "trickling" flow of the last little bit of propellant would also produce rough combustion, which could be damaging. As Tristan notes, the turbopump would also be catastrophically damaged if propellant flow trickled.
answered 7 hours ago
Russell BorogoveRussell Borogove
87.1k3291376
$endgroup$
4
$begingroup$
Not just that, but if the inlet of a turbopump impeller runs dry, it would overspeed with blinding alacrity.
$endgroup$
– Tristan
7 hours ago
add a comment |
$begingroup$
were the engines "allowed" to shut down as a result of running out of propellant? Or were they issued a shut down command with some propellant left?
Shutdown was commanded when the appropriate trajectory was reached.
Even in multistage rockets, rocket engines are not run to complete depletion of propellant. The fuel/oxidizer mix ratio must be closely controlled to avoid damage to the engine; if the fuel ran out early the mixture ratio would go ox-rich, increasing combustion chamber temperature. The "trickling" flow of the last little bit of propellant would also produce rough combustion, which could be damaging. As Tristan notes, the turbopump would also be catastrophically damaged if propellant flow trickled.
answered 7 hours ago
Russell BorogoveRussell Borogove
87.1k3291376
$endgroup$
4
$begingroup$
Not just that, but if the inlet of a turbopump impeller runs dry, it would overspeed with blinding alacrity.
$endgroup$
– Tristan
7 hours ago
add a comment |
$begingroup$
were the engines "allowed" to shut down as a result of running out of propellant? Or were they issued a shut down command with some propellant left?
Shutdown was commanded when the appropriate trajectory was reached.
Even in multistage rockets, rocket engines are not run to complete depletion of propellant. The fuel/oxidizer mix ratio must be closely controlled to avoid damage to the engine; if the fuel ran out early the mixture ratio would go ox-rich, increasing combustion chamber temperature. The "trickling" flow of the last little bit of propellant would also produce rough combustion, which could be damaging. As Tristan notes, the turbopump would also be catastrophically damaged if propellant flow trickled.
answered 7 hours ago
Russell BorogoveRussell Borogove
87.1k3291376
$endgroup$
were the engines "allowed" to shut down as a result of running out of propellant? Or were they issued a shut down command with some propellant left?
Shutdown was commanded when the appropriate trajectory was reached.
Even in multistage rockets, rocket engines are not run to complete depletion of propellant. The fuel/oxidizer mix ratio must be closely controlled to avoid damage to the engine; if the fuel ran out early the mixture ratio would go ox-rich, increasing combustion chamber temperature. The "trickling" flow of the last little bit of propellant would also produce rough combustion, which could be damaging. As Tristan notes, the turbopump would also be catastrophically damaged if propellant flow trickled.
answered 7 hours ago
Russell BorogoveRussell Borogove
87.1k3291376
edited 6 hours ago
answered 7 hours ago
Russell BorogoveRussell Borogove
87.1k3291376
answered 7 hours ago
Russell BorogoveRussell Borogove
87.1k3291376
answered 7 hours ago
Russell BorogoveRussell Borogove
87.1k3291376
87.1k3291376
4
$begingroup$
Not just that, but if the inlet of a turbopump impeller runs dry, it would overspeed with blinding alacrity.
$endgroup$
– Tristan
7 hours ago
add a comment |
4
$begingroup$
Not just that, but if the inlet of a turbopump impeller runs dry, it would overspeed with blinding alacrity.
$endgroup$
– Tristan
7 hours ago
4
4
$begingroup$
Not just that, but if the inlet of a turbopump impeller runs dry, it would overspeed with blinding alacrity.
$endgroup$
– Tristan
7 hours ago
$begingroup$
Not just that, but if the inlet of a turbopump impeller runs dry, it would overspeed with blinding alacrity.
$endgroup$
– Tristan
7 hours ago
add a comment |
Mitch99 is a new contributor. Be nice, and check out our Code of Conduct.
Mitch99 is a new contributor. Be nice, and check out our Code of Conduct.
Mitch99 is a new contributor. Be nice, and check out our Code of Conduct.
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