Question about 1986 Challenger incident

[nmsurobert]

I've been doing a bit of googling and reading, and I don't understand why the space shuttle broke apart. To my understanding nothing exploded. Instead there was a massive leak of fuel that created a fire ball. If the space shuttle could handle Earth reentry, why couldn't it handle the fire ball produced by the fuel leak?

thanks!

sorry if this is in the wrong section.

 

[phinds]

I've been doing a bit of googling and reading, and I don't understand why the space shuttle broke apart. To my understanding nothing exploded. Instead there was a massive leak of fuel that created a fire ball. If the space shuttle could handle Earth reentry, why couldn't it handle the fire ball produced by the fuel leak?

thanks!

sorry if this is in the wrong section.

The breakup was caused by aerodynamic forces after the O-ring failure and the fireball followed

 

[nmsurobert]

The breakup was caused by aerodynamic forces after the O-ring failure and the fireball followed

thats what I've read. "aerodynamic forces" and similar words. can you elaborate a little bit? like i said, it handles reentry and the forces exerted on it while its leaving earth, but the forces it experienced after the during were different or stronger? how? was it flipping and spinning out of control and that caused it rip itself apart?

 

[Drakkith]

The shuttle and launch equipment (boosters, external fuel tank, etc) are only designed to handle the stress of high-speed flight through the atmosphere when flying forwards. Small attitude changes are acceptable, but the incident caused the shuttle to veer well off-center and the resulting aerodynamic forces tore it to pieces. It's a bit like sticking your hand out a car window when traveling down the freeway at 80 mph. If you keep your hand and fingers oriented like a wing with the wind coming edge-on, there's not that much resistance. But if you twist your hand so that it's more like a sail than a wing, your arm is suddenly jerked backwards from the increased resistance.

Now imagine the shuttle, flying at multi-mach speeds, being forced off-center so that the airflow is suddenly slamming into its side instead of its nose. It just wasn't designed to handle flying sideways at that speed and was torn apart.

From wiki:

The breakup of the vehicle began at T+73.162 seconds and at an altitude of 48,000 feet (15 km).^[28] With the external tank disintegrating (and with the semi-detached right SRB contributing its thrust on an anomalous vector), Challenger veered from its correct attitude with respect to the local airflow, resulting in a load factor of up to 20 (or 20 g), well over its design limit of 5 g and was quickly ripped apart by abnormal aerodynamic forces (contrary to popular belief, the orbiter did not explode as the force of the external tank breakup was well within its structural limits).

As this quote says, the sudden deceleration (from the drastically increased air resistance due to the vehicle's attitude change) was about 4 times the designed limit.

 

[nmsurobert]

The shuttle and launch equipment (boosters, external fuel tank, etc) are only designed to handle the stress of high-speed flight through the atmosphere when flying forwards. Small attitude changes are acceptable, but the incident caused the shuttle to veer well off-center and the resulting aerodynamic forces tore it to pieces. It's a bit like sticking your hand out a car window when traveling down the freeway at 80 mph. If you keep your hand and fingers oriented like a wing with the wind coming edge-on, there's not that much resistance. But if you twist your hand so that it's more like a sail than a wing, your arm is suddenly jerked backwards from the increased resistance.

Now imagine the shuttle, flying at multi-mach speeds, being forced off-center so that the airflow is suddenly slamming into its side instead of its nose. It just wasn't designed to handle flying sideways at that speed and was torn apart.

From wiki:
As this quote says, the sudden deceleration (from the drastically increased air resistance due to the vehicle's attitude change) was about 4 times the designed limit.

ahhhhh that makes total sense. thank you!

 

[Drakkith]

thats what I've read. "aerodynamic forces" and similar words. can you elaborate a little bit? like i said, it handles reentry and the forces exerted on it while its leaving earth, but the forces it experienced after the during were different or stronger? how? was it flipping and spinning out of control and that caused it rip itself apart?

I believe the launch only exposed the shuttle to about 3 g's at maximum. I wasn't able to find a number for the g's forces experienced during re-entry, but I guarantee you they aren't anywhere close to 20 g's.

 

[nmsurobert]

Awesome. Thanks everyone.
Im talking about the space shuttle in my high school astronomy class and i could already hear a student asking me a question (this question) that i don't exatly know the answer to haha.