The Separation of SRB from ET

Hello everyone!

I just got a question from readers on "How long till booster separation" by my Formspring's inbox.

So, here is the answer :

Basically, NASA's space shuttle is consists of Orbiter, External Tank (ET) and Solid Rocket Boosters (SRBs).

I had post a few articles about space shuttle.

• For more infos about the space shuttle, click here.
• For more infos about the SRBs, click here.

The launching of the space shuttle needs help from the SRBs as they are solid rockets that provide most of the main force or thrust (71 percent) needed to lift the space shuttle off the launch pad. In addition, the SRBs support the entire weight of the space shuttle orbiter and external fuel tank on the launch pad.

Insert question : How the space shuttle countdown operates?

After 2 minutes Space Shuttle is launch from it's launching pad (at T-0) , the SRBs will separates from shuttle (T+2 min).

At T+2min , SRBs separates from the orbiter and external fuel tank at an altitude of 28 miles (45 km). Main engines continue firing.

1. Parachutes deploy from the SRBs.
2. SRBs will land in the ocean about 140 miles (225 km) off the coast of Florida.
3. Ships will recover the SRBs and tow them back to Cape Canaveral for processing and re-use.

This separation occurs after about 2 minutes of burn time of the reusable solid rocket motors, and firing of the booster separation motors takes less than a second. The Space Shuttle Solid Rocket Booster separation rocket motors must be used in conjunction with the release of the motors from the External Tank (ET).

At T +7.7 min - main engines throttled down to keep acceleration below 3g's so that the shuttle does not break apart.

T +8.5 min - main engines shut down.

T +9 min - ET separates from the orbiter. The ET will burn up upon re-entry.

The ET is made of aluminum and aluminum composite materials. It has two separate tanks inside,

• the forward tank for oxygen
• and the aft tank for hydrogen, separated by an intertank region.

Each tank has baffles to dampen the motion of fluid inside. Fluid flows from each tank through a 17-inch (43 cm) diameter feed line out of the ET through an umbilical line into the shuttle's main engines. Through these lines, oxygen can flow at a maximum rate of 17,600 gallons/min (66,600 l/min) and hydrogen can flow at a maximum rate of 47,400 gallons/min (179,000 l/min).

The ET is covered with a 1-inch (2.5 cm) thick layer of spray-on, polyisocyanurate foam insulation. The insulation keeps

• the fuels cold,
• protects the fuel from heat that builds up on the ET skin in flight,
• and minimizes ice formation.

When Columbia launched in 2003, pieces of the insulating foam broke off the ET and damaged the left wing of the orbiter, which ultimately caused Columbia to break up upon re-entry.

T +10.5 min - OMS engines fire to place you in a low orbit.

T +45 min - OMS engines fire again to place you in a higher, circular orbit (about 250 miles/400 km).

Ok, this is a summarize form on how actually the space shuttle is launced. Now, I have a question for you. If you had read about the space shuttle before, you may answer my simple question ;).

Which of these shuttle's components (ET, SRBs and Orbiter) is not reusable?

If you knew the answer, let me know. =]