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Question about SRBs and the S-IC

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VincentMcConnell:

--- Quote ---Each Shuttle SRB had a liftoff thrust of 12 MN; the F-1, only 6.77 MN.
--- End quote ---
-Kaq9

I knew the thrust was comparable, but double? Why do we say the Saturn V was the most powerful rocket to leave the ground if the shuttle has a stronger SRB stack?
Thanks for any and all answers.

Peter B:

--- Quote from: VincentMcConnell on June 17, 2012, 12:17:41 PM ---
--- Quote ---Each Shuttle SRB had a liftoff thrust of 12 MN; the F-1, only 6.77 MN.
--- End quote ---
-Kaq9

I knew the thrust was comparable, but double? Why do we say the Saturn V was the most powerful rocket to leave the ground if the shuttle has a stronger SRB stack?
Thanks for any and all answers.

--- End quote ---
Five F-1s per S-1C.

Two SRBs per Shuttle.

VincentMcConnell:
Oh... Duh... Silly me. I forgot that the entire assembly wasn't the F1. The five F1's make up the assembly. Got it. Thanks!

Jason Thompson:
For a number of reasons. First, the combination of two SRBs and three SSMEs still comes in below the combined thrust of the of five F-1 engines used in the Saturn V first stage. Second, the SSMEs and the SRBS are pretty much all the shuttle has. Once they're gone it's shot its bolt and only has the OAMS system for small course corrections. The Saturn V still has the second and third stages to be added to its total power after the five F-1 engines have shut down.

The N-1 rocket generated more liftoff thrust even than the Saturn V, at about 10 million pounds, but because the whole thing used kerosene/LOX for fuel it was overall a lot less powerful than the Saturn V.

ka9q:
Right. My point in comparing the F-1 to a SRB was to compare the thrust per engine and to show that single solid rocket motors can be made with much more thrust than single liquid rocket motors.

The main drawback to solid rockets vs liquid rockets is their much lower specific impulse. The propellant doesn't contain as much chemical energy per kilogram as the modern liquid propellants, especially liquid hydrogen and oxygen.

Solids have a few other problems. They emit chlorine compounds that may damage the ozone layer. Their exhaust contains solid particles (e.g., aluminum oxide) that, in space, could constitute hazardous orbital debris. They have to be handled fully loaded, increasing weight and hazards. They cannot be shut down or throttled once ignited, though they can produce a predetermined thrust-vs-time curve. And when they fail, they tend to do so suddenly and catastrophically.

But working against all these drawbacks is the simplicity and low cost of solid rocket motors and the fact that they can be built with much more thrust than an individual liquid rocket engine. And at launch, high thrust is often everything. That's why they're so popular as boosters, with upper stages usually burning more energetic liquid propellants.

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