In the proposed CLV and SDHLV there are the 4 and 5 segment SRB combinations. Just what is the the difference between the two as far as burn times go. I suspect not much as the solid fuel is burning from the inner surface out.
From what Griffin has said they are the same. <br /><br /><font color="yellow">DR. GRIFFIN: What you see is the first piece of what is basically a one and a half launch concept, a shuttle-derived vehicle, where we use the solid rocket boosters, but extend it to five segment boosters and show an external tank, lengthened, but fundamentally the same tank, with five shuttle main engines on the back. The booster stage in the normal way after two minutes or so, two minutes and seven seconds of burn.</font>
Well, OK<br />That is exactly backwords from what I would have expected.<br /><br />I had expected that the more segments = more total length = longer burn time<br /><br />and more width = more surface area to burn.<br /><br />I assumed that a SRB only burns at the surface of the fuel. If it the flame front travelled faster than the surface was eroded you would get burning inside the solid material. Wouldn't that cause an explosion?<br /><br />I assumed that the surface area available was proportional to the width of the SRB. Now I've heard some talk of a "star configuration", could somebody tell me what that means.
The solid fuel in the SRB is in a star patern, the yellow stuff in the cross section below. As the fuel burns from the inside out the surface area changes and therefore so does the thrust. The inital thrust decreases as the vehicle climbs and loses mass and therefore this and throtteling the SSME keeps the acceleration under 3g.<br /><br />Adding an extra section increases thrus as the time take for the fuel to burn from the middle out is the same, there is more fuel burning hence more thrust in the same time. Similary making the SRB wider and a thicker layer of fuel increases the burn time.<br /><br />It's all rather clever.
I never understood it until I found this wonderful air & space museum in Paris when I travelled there with my husband. The museum is at Orly Airport and has a fantastic section on space travel with a strong emphasis on the rockets themselves. It had a fun little interactive video display where you would be told what the rocket's mission parameters where (how fast it had to climb, when to throttle up or down, etc) and then it would ask you to design the shape of the hole down the center of the propellant in the SRB. It was extremely informative.<br /><br />If you ever go to Paris, check that museum out. It's awesome. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>
This of an SRB as a tube full of fuel, but with a long hole cut down the length of the tube. The whole surface of that hole, which runs the entire length of the booster, is lit at once....and the fuel burns radially outward. When it reaches the edge (circumference) of the casing is when it burns out.<br /><br />Thus increase diameter, increase burn time since it takes longer to reach the edge. <div class="Discussion_UserSignature"> <p>-Ben</p> </div>
Yea.<br /><br />Also, as SG pointed out, you can also alter both parameters by changing the composition/grain of the fuel itself. But keeping it the same, the above applies.<br /><br />Shuttle Guy, can you (or anyone) explain how the Shuttle's SRB is designed so that it produces less thrust at Max-Q? What exactly is it in the fuel or SRB casing that lessens the thrust? That's one thing I can't explain well. <div class="Discussion_UserSignature"> <p>-Ben</p> </div>
Yep....propulsions = extremely cool stuff.<br /><br />We just finished covering rocket propulsion (solid, liquid engines, hybrid, and electric) in my propulsion class. Sparked a few of our intersets and now there are a few of us trying to build a liquid rocket engine for our senior project. <br /><br />But its funny...cuz I learn stuff here as well...that I can apply at school and thats pretty cool.<br /><br />This class though, is centerd more on air breathing...so jet engines will be the bulk. Come spring, there's a grad level class on rocket engines...can't wait.<br /><br />
Good explanation, certaily clarified itfor me. I did not know that the star pattern was not cut all the way through.<br /><br />Any idea what shapes or bores were/are used in Titans and Deltas? <div class="Discussion_UserSignature"> <p>-Ben</p> </div>