by iamlucky13 » Mon Feb 11, 2008 8:12 pm
rafa wrote:One point that I have always wondered about Where does the Shuttle stands when it is upright on the pad? It seems clear that the orbiter "hangs" from the bipod and the tail suport on the External tank (flimsy as the look). The ET is not suported anywhere on its base, so it also "hangs" from the two SRBs. That means that whole weight of the loaded vehicle rests just on the skirts of the SRBs. They must be really strong. Is that so, or is there any other support point that I am mising, such as the big gray box in front of the Atlantis starboard wing??
Good question, and yes. The Solid Rocket Boosters support the entire stack. If you think about it, this actually makes sense. With 5.6 million pounds of combined thrust (the shuttle's main engines only contribute 1.2 million pounds together), the entire assembly is "supported" by the SRB's in flight, as well as on the pad. In fact, before the external tank is fueled, the stack only weighs about 3 million pounds (4.6 million fueled).
The stack is nearly balanced, but the 240,000 pound orbiter hanging on the side does give it a slight tendency to tip. I'm not sure if there are additional supports around that box, or if the hold-down bolts (which are blown as soon as the SRB's ignite) are able to support that...it's only 5% of the fully fueled weight.
One of the challenges in designing the external tank was making it lightweight enough to go almost all the way to space, yet strong enough to support the two SRB's hanging on the side and the shuttle on the back. Considering it weighs only 60,000 pounds, but supports 6.8 million pounds of total thrust and holds 1.6 million pounds of fuel, I'd say the engineers did an amazing job on a seemingly simple piece of hardware.
emc wrote:I wonder if the angled "almost appears to be suspended" white rectanglar structure near center is an emergency escape "slide"?
That's actually a cover to protect the wing from inclement weather when the rotating service structure is closed over the orbiter. This cover is why a severe hailstorm which caused enough damage to the foam on the tank on STS-117 to warrant a rollback to the vehicle assembly building for repairs left the delicate thermal tiles basically untouched.
The tower escape system is on the other side of the fixed service structure. If they had to use it, they'd unbuckle, blow the hatch, run across the gantry, jump into a pair of 4-person gondolas, and be whisked down a 1200 foot long zipline into the safety of a concrete bunker. I saw a video of this once on an IMAX screen. It made me dizzy just watching it.
I can't seem to find any good pictures of this escape system from afar, but here's one showing the rotating service structure in the closed position:
![Image](http://www.floridatoday.com/floridatoday/blogs/spaceteam/uploaded_images/mrb-Endeavour-on-pad-3-725220.jpg)
[quote="rafa"]One point that I have always wondered about Where does the Shuttle stands when it is upright on the pad? It seems clear that the orbiter "hangs" from the bipod and the tail suport on the External tank (flimsy as the look). The ET is not suported anywhere on its base, so it also "hangs" from the two SRBs. That means that whole weight of the loaded vehicle rests just on the skirts of the SRBs. They must be really strong. Is that so, or is there any other support point that I am mising, such as the big gray box in front of the Atlantis starboard wing??[/quote]
Good question, and yes. The Solid Rocket Boosters support the entire stack. If you think about it, this actually makes sense. With 5.6 million pounds of combined thrust (the shuttle's main engines only contribute 1.2 million pounds together), the entire assembly is "supported" by the SRB's in flight, as well as on the pad. In fact, before the external tank is fueled, the stack only weighs about 3 million pounds (4.6 million fueled).
The stack is nearly balanced, but the 240,000 pound orbiter hanging on the side does give it a slight tendency to tip. I'm not sure if there are additional supports around that box, or if the hold-down bolts (which are blown as soon as the SRB's ignite) are able to support that...it's only 5% of the fully fueled weight.
One of the challenges in designing the external tank was making it lightweight enough to go almost all the way to space, yet strong enough to support the two SRB's hanging on the side and the shuttle on the back. Considering it weighs only 60,000 pounds, but supports 6.8 million pounds of total thrust and holds 1.6 million pounds of fuel, I'd say the engineers did an amazing job on a seemingly simple piece of hardware.
[quote="emc"]I wonder if the angled "almost appears to be suspended" white rectanglar structure near center is an emergency escape "slide"?[/quote]
That's actually a cover to protect the wing from inclement weather when the rotating service structure is closed over the orbiter. This cover is why a severe hailstorm which caused enough damage to the foam on the tank on STS-117 to warrant a rollback to the vehicle assembly building for repairs left the delicate thermal tiles basically untouched.
The tower escape system is on the other side of the fixed service structure. If they had to use it, they'd unbuckle, blow the hatch, run across the gantry, jump into a pair of 4-person gondolas, and be whisked down a 1200 foot long zipline into the safety of a concrete bunker. I saw a video of this once on an IMAX screen. It made me dizzy just watching it.
I can't seem to find any good pictures of this escape system from afar, but here's one showing the rotating service structure in the closed position:
[img]http://www.floridatoday.com/floridatoday/blogs/spaceteam/uploaded_images/mrb-Endeavour-on-pad-3-725220.jpg[/img]