Oobleck

We have had a number of requests now to try Oobleck ( aka Magic Mud / Slime / Cornstarch & Water). This is what's also known as a Non-Newtonian liquid. It has the unusual property that when you apply pressure to it its viscosity significantly increases and when you remove that pressure it becomes liquid again.

Highlights Video

For this test we used our smaller Axion III rocket as we didn't want to have to make up a great deal of Oobleck. For the first flight we made it a little thicker and it took quite a while to pour into the rocket. I think we ended pouring only about 600mL into it.

2Kg of Cornstarch

Mixing is slow

Pouring is also slow

Waiting for Oobleck to settle

Mmmmm ... tasty

Ready to go

We also used our old launcher for this as we knew it was going to get really messy. The rocket was pressurised to 120psi and we launched. The rocket popped up a little out of the launcher and sat back down on the pad with the guide rail holding it facing up.. We suspect it was just the pressure in the air hose that allowed it to separate. The rocket then proceeded to ooze out the Oobleck for the next 12 seconds. You could see the level dropping in the rocket. When it was sufficiently low the rocket sputtered and then took off. It looked very much like an air only launch at that point. The rocket didn't go very high and although the parachute deployed right around apogee there just wasn't enough time for it to fully inflate. But the rocket landed safely sideways without damage.

We made up some more Oobleck with a somewhat more runny consistency but still exhibiting the right properties. We again launched the rocket at 120psi only for the rocket to again repeat what it did last time. The rocket just popped out of the launcher and sat there oozing the Oobleck. and then 1:20 minutes later it launched by itself. Again there was not enough time for the parachute to fully inflate, but because the rocket did not fall from a great height it survived without damage.

What was interesting that after the rocket had landed there were a couple of sizable lumps of dried Oobleck in the rocket. This would have added considerable weight to the rocket as well. The air must have made its way past the remainder of the Oobleck still in the rocket.

For the third attempt we made it even more runny and added a little food colouring. Had we added a couple of eggs we could have had a nice cake..We debated whether to set the delay to one second, but there was a chance the rocket might go better this time so we left it set at two seconds. Nope, the rocket repeated what it did last time  With more Oobleck in it this time the rocket took 1:28 minutes before it launched itself and again not very high. This time the nosecone hit first and bucked the top bottle.

Launching at 120psi

Post landing

More runny consistency

Not going anywhere fast

Someone needs to clean this up...

... and this too!

Conclusion

You can't use a non-Newtonian liquid in a water rocket and expect it to behave itself. Though you have to wonder if this could be used as a launcher-less launcher. You simply pour some Oobleck into the rocket and then just quick fill it with water and air through a thin tube? ... Now we need to go wash everything off. At least the cornstarch cleans up easily with water.

Miscellaneous

We also flew a couple of more flights today related to the experiment from Day 172 so the detail of those are covered in the day 172 report..

Flight Details