current Formula 1 structural safety factors

[bill shoe]

What's the cause of it springing back? Is it because of the so called dynamic overshoot and the resulting reduction in moment once for shuttle thrust reaches steady state?

Before engine-start the shuttle sits in one position, call it rest position. Then if you start the shuttle engines and hypothetically let everything sit there with shuttle engines running (but not side boosters) for 10 or 20 seconds it would reach a relatively static alternate position, call it running position.

When the shuttle engines fire up during a real launch, the assembly goes from rest position to running position in about 1 or 2 seconds, but when it first reaches running position the top of the assembly has horizontal velocity and inertia and it keeps going past there. It overshoots running position by a few more feet. It reaches a max overshoot position and starts coming back toward running position. At some point before this swaying is complete, the side boosters fire and the whole thing lifts off.

The horizontal overshoot at the top puts mega bending-stress on the bottom which is constrained in rest position until subsequent launch/release. This is what caused NASA to eventually add 20,000 lbs of structure to the launch assembly without knowing why it was necessary.

One of many lessons that can be learned from this: Fixing a problem should begin with a thorough visual inspection. If possible inspect the stuff dynamically and in use.

[Cold Fussion]

That makes sense. What was the reasoning behind not firing the solid boosters at the same time as the shuttle engines? If the main engine 'spooling time' was less than a second, wouldn't firing the boosters at the same time go a long way to balancing the moments and forces? Or is the way it was done truely the only stable way of launching?

[bill shoe]

The shuttle main engine are liquid-fueled and take a few seconds to build up. The boosters are solid-fuel and light off quickly.

One of the report links in this thread describes how NASA originally planned a shorter time between main engine light-off and booster light-off. However, there was some secondary issue that was improved with a slower/longer main engine fire-up, so the gap between main engine vs. boosters was increased. This allowed the point of maximum overshoot to be reached before launch, it would not have been reached with the earlier quicker timing gap.

[Cold Fussion]

The shuttle main engine are liquid-fueled and take a few seconds to build up. The boosters are solid-fuel and light off quickly.

One of the report links in this thread describes how NASA originally planned a shorter time between main engine light-off and booster light-off. However, there was some secondary issue that was improved with a slower/longer main engine fire-up, so the gap between main engine vs. boosters was increased. This allowed the point of maximum overshoot to be reached before launch, it would not have been reached with the earlier quicker timing gap.

I thought I read in that report posted earlier that the SSME took 600 milliseconds to reach full thrust but that must have been for the SRB's.

[riff_raff]

The Shuttle RS-25 main engines took almost 5 seconds to generate full thrust. The SSME's were attached to the aft end of the Orbiter. The Orbiter was attached to the ET using just three large bolts. One at the "bipod" located at the fwd end of the orbiter, and two at the L/R "aft attachments" located towards the rear/mid area of the vehicle. The fwd bipod and aft attachments were designed to compensate for thermal expansion differences between the orbiter and ET structure during fueling and launch. The ET could experience several inches of "cryo shrinkage" when being filled with liquid propellants. The LH2 feed between the ET and Orbiter used a 17" diameter butterfly valve to cut off the flow at separation.

Here's a quote from a https://history.nasa.gov/columbia/Troxe ... Report.pdf: "The physical cause was damage to Columbia’s left wing by a 1.7 pound piece of insulating foam that detached from the left “bipod ramp” that connects the External Tank1
to the orbiter, and struck the orbiter’s left wing 81.9 seconds after launch. The foam strike created a hole in a Reinforced Carbon-Carbon (RCC) panel on the leading edge of the wing, allowing superheated air (perhaps exceeding 5,000oF) to enter the wing during reentry. The extreme heat caused the wing to fail structurally, creating aerodynamic forces that led to the disintegration of the orbiter."