#1
|
|||
|
|||
Throttling SRB's
How are the SRB's throttled? I was reading the Rogers report and it says
this: "Both the Shuttle main engines and the solid rockets operated at reduced thrust approaching and passing through the area of maximum dynamic pressure of 720 pounds per square foot. Main engines had been throttled up to 104 percent thrust and the Solid Rocket Boosters were increasing their thrust when the first flickering flame appeared on the right Solid Rocket Booster in the area of the aft field joint." http://history.nasa.gov/rogersrep/v1ch3.htm TIA. -- Alan |
#2
|
|||
|
|||
Throttling SRB's
Alan Pretre no@spam wrote in message
... How are the SRB's throttled? I was reading the Rogers report and it says this: "Both the Shuttle main engines and the solid rockets operated at reduced thrust approaching and passing through the area of maximum dynamic pressure of 720 pounds per square foot. Main engines had been throttled up to 104 percent thrust and the Solid Rocket Boosters were increasing their thrust when the first flickering flame appeared on the right Solid Rocket Booster in the area of the aft field joint." Via innovative engineering design, i.e., by molding the shape of the solid fuel for different flight regimes. -- John Thomas Maxson, Retired Engineer (Aerospace) Author, The Betrayal of Mission 51-L (www.mission51l.com) |
#3
|
|||
|
|||
Throttling SRB's
Alan Pretre no@spam wrote:
How are the SRB's throttled? I was reading the Rogers report and it says this: "Both the Shuttle main engines and the solid rockets operated at reduced thrust approaching and passing through the area of maximum dynamic pressure of 720 pounds per square foot. Main engines had been throttled up to 104 percent thrust and the Solid Rocket Boosters were increasing their thrust when the first flickering flame appeared on the right Solid Rocket Booster in the area of the aft field joint." Geometry. If you have a simple solid rocket with a cylindrical hole up the middle and it burns from the inside to the outside, then the thrust generally increases as the area of burning fuel increases. Making funny shapes in the core to begin with (star shaped hole, or other shapes or varying the composition) can all be used to trim the thrust profile. The SRBs cannot be throttled. -- http://inquisitor.i.am/ | | Ian Stirling. ---------------------------+-------------------------+-------------------------- If God hadn't intended us to eat animals, He wouldn't have made them out of MEAT! - John Cleese |
#4
|
|||
|
|||
Throttling SRB's
"Alan Pretre" no@spam wrote in message ... How are the SRB's throttled? It's not something actually done in real time, it's the construction of the SRB themselves that, I presume, have less propellant at that stage of burning than at other times Doug |
#5
|
|||
|
|||
Throttling SRB's
"Ian Stirling" wrote in message
... How are the SRB's throttled? Geometry. If you have a simple solid rocket with a cylindrical hole up the middle and it burns from the inside to the outside, then the thrust generally increases as the area of burning fuel increases. Making funny shapes in the core to begin with (star shaped hole, or other shapes or varying the composition) can all be used to trim the thrust profile. The SRBs cannot be throttled. Thanks. I thought perhaps they diluted the fuel in places with nonfuel matter. Does the burning in the cylindrical hole happen all along the length of the SRB or does it work its way from one end to the other? -- Alan |
#6
|
|||
|
|||
Throttling SRB's
"Doug Ellison" wrote in message
... "Alan Pretre" no@spam wrote in message ... How are the SRB's throttled? It's not something actually done in real time, it's the construction of the SRB themselves that, I presume, have less propellant at that stage of burning than at other times Thanks. I'm wondering then, that if you had a SME failure very early in the launch sequence but after SRB ignition (ie can't abort launch yet), that the shuttle would be at a lower altitude than it should be at a given T+x instant. Is it possible, with the SRB's thrust profile timed for 3 working engines, can the the SRB profile get out of whack, that is, for the boosters to get out of sync with respect to where the shuttle is in max Q? Or perhaps it is not possible for the shuttle to reach max Q with an engine out, even with the SRB's at full thrust. -- Alan |
#7
|
|||
|
|||
Throttling SRB's
Alan Pretre no@spam wrote:
"Ian Stirling" wrote in message ... How are the SRB's throttled? Geometry. If you have a simple solid rocket with a cylindrical hole up the middle and it burns from the inside to the outside, then the thrust generally increases as the area of burning fuel increases. Making funny shapes in the core to begin with (star shaped hole, or other shapes or varying the composition) can all be used to trim the thrust profile. The SRBs cannot be throttled. Thanks. I thought perhaps they diluted the fuel in places with nonfuel matter. Does the burning in the cylindrical hole happen all along the length of the SRB or does it work its way from one end to the other? The SRB burns from the inside out. One advantage of this method is that the fuel insulates the casing until the last of it burns, so you only have to have insulation on the inside that can cope with the very end of the burn and any asymmetries in burning, rather than that which can cope with (at the nozzle end) several minutes. There is a complex "starter", which IIRC is basically a small rocket engine in the nose of the SRB pointing down the core, engineered for utter reliability. You can have combinations, where the core burns outwards from the middle but only half-way up the rocket and then transitions to end burning, so that you get a large burst of thrust at the beginning then a long sustained burn. (also, the propellant does not burn fast enough to allow a "end burner" of the SRBs size to generate enough thrust.) -- http://inquisitor.i.am/ | | Ian Stirling. ---------------------------+-------------------------+-------------------------- "The theory of everything falls out trivially." -- Etherman, sci.physics kook. |
#8
|
|||
|
|||
Throttling SRB's
"Alan Pretre" no@spam wrote in message ...
"Ian Stirling" wrote in message ... How are the SRB's throttled? Geometry. If you have a simple solid rocket with a cylindrical hole up the middle and it burns from the inside to the outside, then the thrust generally increases as the area of burning fuel increases. Making funny shapes in the core to begin with (star shaped hole, or other shapes or varying the composition) can all be used to trim the thrust profile. The SRBs cannot be throttled. Thanks. I thought perhaps they diluted the fuel in places with nonfuel matter. Does the burning in the cylindrical hole happen all along the length of the SRB or does it work its way from one end to the other? The try and make the fuel as uniform as they can, and go to fairly significant effort to ensure uniformity -- no part of the fuel is intentionally "diluted" or otherwise weaker than any other part. The burning is essentially simultaneous along the entire length of the booster (I believe the igniters are at the top, IIRC). It burns from the center toward the outside casing. So all the control of the thrust profile is done by the geometry of the initial hole down the middle. --Rich |
#9
|
|||
|
|||
Throttling SRB's
Richard Cochran wrote:
"Alan Pretre" no@spam wrote in message ... "Ian Stirling" wrote in message ... How are the SRB's throttled? Geometry. If you have a simple solid rocket with a cylindrical hole up the middle and it burns from the inside to the outside, then the thrust generally increases as the area of burning fuel increases. Making funny shapes in the core to begin with (star shaped hole, or other shapes or varying the composition) can all be used to trim the thrust profile. The SRBs cannot be throttled. snip burns from the center toward the outside casing. So all the control of the thrust profile is done by the geometry of the initial hole down the middle. There are however designs of solid rocket that can vary the thrust in other ways. Burning rate typically depends on pressure. Exactly how much depends on which propellant. The nozzle throat can be designed to erode, and reduce the pressure in the casing over that of an uneroding nozzle. You can also open large vents, and practically shut down the burn. Depending on what sort of propellant you are using, it might even stop burning altogether. In theory if you could reclose the vent, you could then restart the motor. -- http://inquisitor.i.am/ | | Ian Stirling. ---------------------------+-------------------------+-------------------------- The fight between good and evil, an epic battle. Darth vader and Luke, suddenly in the middle of the fight, Darth pulls Luke to him, and whispers "I know what you'r getting for christmas!" Luke exclaims "But how ??!?" "It's true Luke, I know what you'r getting for christmas" Luke tries to ignore this, but wrenches himself free, yelling "How could you know this?", Vader replies "I felt your presents" -- The Chris Evans breakfast show ca. 94 |
#10
|
|||
|
|||
Throttling SRB's
Alan Pretre wrote:
"Ian Stirling" wrote in message ... How are the SRB's throttled? Geometry. If you have a simple solid rocket with a cylindrical hole up the middle and it burns from the inside to the outside, then the thrust generally increases as the area of burning fuel increases. Making funny shapes in the core to begin with (star shaped hole, or other shapes or varying the composition) can all be used to trim the thrust profile. The SRBs cannot be throttled. Thanks. I thought perhaps they diluted the fuel in places with nonfuel matter. Does the burning in the cylindrical hole happen all along the length of the SRB or does it work its way from one end to the other? Along the entire length. At the same time. As the propellant burns, the interior radius and therefore the exposed surface increases therefore the thrust increases. BTW as the propellant is burned the mass of the SRB decreases so accelleration goes up Julian |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Atlas SRBs | LooseChanj | Space Science Misc | 17 | February 27th 04 01:03 AM |
How Many "Hot" SRBs on Mission 51-L? | John Maxson | Space Shuttle | 1 | September 11th 03 11:57 PM |