Saturn V acceleration

[Sus_pilot]

This is one of the few times I can speak with authority - they were shipped by rail from Utah to Florida.

[Bob B.]

This is one of the few times I can speak with authority - they were shipped by rail from Utah to Florida.

I should have known better, I know Thiokol (presently ATK) is in Utah.  I was thinking of the external tanks, which were made at Lockheed Martin's Michoud Assembly Facility in New Orleans.

[JayUtah]

I should have known better, I know Thiokol (presently ATK) is in Utah.  I was thinking of the external tanks, which were made at Lockheed Martin's Michoud Assembly Facility in New Orleans.

Officially, ATK Wasatch Propulsion Division.  The shipping containers are still at the siding in the Corinne, Utah rail depot.  They are the long, white rectangular objects seen in this aerial view.

https://www.google.com/maps/place/Corinne,+UT/@41.5622323,-112.1320478,326m/data=!3m1!1e3!4m2!3m1!1s0x8753639505cb521f:0xee6c1390c36ddc66

The segments were transported from the vast ATK complex by highway to Corinne and placed on rail cars there.  Here is the main ATK site.

https://www.google.com/maps/place/Corinne,+UT/@41.6586852,-112.4276487,5205m/data=!3m1!1e3!4m2!3m1!1s0x8753639505cb521f:0xee6c1390c36ddc66

The roadway between the remote Thiokol site and Corinne is very smooth and flat for that purpose, and very infrequently patrolled by highway patrol.  Hence the speed limit is rarely obeyed.

Here's someone else's photo page of the ATK rocket garden in Utah.  You can see the grain of the Minuteman first stage with its central cavity.
http://www.ahpra.org/thio.htm

[Bob B.]

Cool!  Thanks.

I see the Minuteman uses a 6-pointed star.  A few years ago I did some calculations with some different shapes to see what kind of thrust profile they gave.  I concluded that a 6-pointed star produced the most even thrust over the duration of the burn.

[JayUtah]

The STS SRM used a grain that altered the thrust to match the programmed SSME throttling profile for dealing with max Q, etc.

[Bob B.]

The STS SRM used a grain that altered the thrust to match the programmed SSME throttling profile for dealing with max Q, etc.

Yes, I've seen of the SRB thrust versus time (see link below) and it definitely drops around max Q and then rises again.  It's my understanding that they used a variety of geometries to get it to do that.

http://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster#mediaviewer/File:Srbthrust2.svg

[JayUtah]

Yes, it's a star pattern with a variable taper on the star points.  Plus, the forward and aft sections of the motor have different cavity shapes.

[ka9q]

The reduced thrust period around max-Q in the shuttle SRBs was called the "thrust bucket".

I'm old enough that I still got a lump in my throat every time I heard the Capcom call out "go at throttle up" at the end of the thrust bucket during a shuttle launch.

My understanding is that solid rocket boosters are still popular because they can provide a lot of thrust (as opposed to specific impulse) fairly cheaply. High thrust is important early in a launch when gravity losses are greatest (because the launcher is still pointed mostly up) and the stack is still pretty heavy. I still don't like to see them launching humans, though.

Gravity losses decrease as the launcher pitches down and mass quickly declines to only a small fraction of that at liftoff. High specific impulse then becomes more important than high thrust as the launcher builds most of its velocity. This is why high performance liquid fueled engines (especially those burning H₂) are popular in upper stages, though there are many exceptions.

[Noldi400]

I'm old enough that I still got a lump in my throat every time I heard the Capcom call out "go at throttle up" at the end of the thrust bucket during a shuttle launch.

I hear you, brother. I can't hear the phrase without getting a mental flash of that fireball and the Y shaped cloud that followed.