SRBs
23 Sep
The space shuttle has two propulsion systems, the main engines, which run on liquid fuel (SSMEs), and the solid rocket boosters (SRBs). The SRBs are the two thinner rockets on either side of the external fuel tank, and they provide most of the thrust that the space shuttle uses to get into orbit. You may have seen video of them dramatically separating from the shuttle, which they do once they are finished boosting the shuttle.
The thing about the SRBs is that because they are solid fuel, there is no easy way to turn them off. The ignition system sets the fuel on fire and it burns until it is used up. When you see the space shuttle launch, you see the SSMEs turn on about 6 seconds before liftoff. The purpose of this is to test SSMEs to make sure that they are operating correctly before the SRBs are lit.
Once the SRBs are lit, they will burn for 123 seconds, and until that time, NASA has no ability to abort the ascent of the space shuttle. It is going for a trip. Once the burn is done, there are several abort options, usually landing in Europe or attempting to turn around and return to Florida. But for those 123 seconds, the shuttle is going to fly on its course.
There are many times in life where you don’t know if everything is going to work perfectly. The shuttle was never tested in unmanned flight before its first launch. Any number of things can and do fail immediately after takeoff. However, sometimes in order to do something important or difficult, you need to take a chance that problems may arise. Launching the space shuttle would be next to impossible on liquid fuel alone, and far more costly. So in order to reap the benefits some great undertaking, sometimes you have to fire the SRBs and hope for the best.
