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News

Successful First Igniter Test

April 26, 2019June 5, 2020
by Dakota

As those of you who follow our Facebook and Instagram (@cprocketry) pages might know, we had an exciting night this past Monday.

After several weeks of deliberation on how to ignite, we settled upon a cocurrent jumpstart from a solid rocket motor. Imagine our large engine housing a smaller engine. The heat of combustion of the small engine ignites the rush of fuel traveling through our bigger engine and — POOF. We have lift-off.

Capturing footage of a solid rocket motor — plain, and without our igniter design.

The Theory

Combustion theory is hard. A good assumption to make, one that doesn’t need a Ph.D., is that our oxidizer and fuel will both need to be vaporized before burning. That is: They need to be a gas. This, at least, is handled by the injector.

The second part is the orientation of the starter flame. To summarize many, many studies and papers in one quick sentence: “The igniter should be oriented the same direction as fluid flow.” (Downwards.) Doing so reduces turbulence inside the engine, reducing the chances of the engine exploding. It also orients the igniter flame away from the shower-head face of the injector, which could cause some orifices to close up.

The big question, then, is how to take a solid, put it inside a liquid shower, turn it all into a gas, and light the whole thing on fire.

The Model

A few ideas came to mind. Do we hang it from a shepherd’s crook? Adhere it to the bottom of a plate? Stick it to the side of a wood pole? The problem with each of these ideas was two-fold. One: With the relatively small size of our engine, how do we ensure that these bulky geometries don’t increase the turbulence? Two: How do we take the straight flame from a solid motor and fan it out in all directions to ignite as much fuel as possible?

Luckily, a little bit of CAD helped solve all of these problems. We settled on a cylindrical igniter plug. This design allows for a variety of motors to be installed and incorporates a diverter to spread flames in all directions. (You can see the outline of our model in the video below.)

The Test

After a watching our first prototype plug print for a few hours, we couldn’t wait to test it out. Even though it was printed from polylactic acid (a plastic which melts at 220°C) and solid motors burn MUCH hotter than that, we figured we could get a few seconds of slow-motion burn time on camera.

And boy, did we get a show.

Proof of concept: The igniter plug design works!

After slowing five seconds of burn time down to several minutes, we had 10 seconds worth of good footage. You can see in the video that each of the radial flame outlets has even distribution and steady flow. Which is just what we want!

You can also tell when the melting plastic starts to disrupt the flame dispersion — about 7 seconds in. The result of that were the smoking, charred remains of our plastic igniter plug. It gave renewed meaning to the word “pungent.”

The Future

Though the test was a success, we began optimizing our design immediately. We inverted the design to allow for ease of access during testing and launch. Loading the motor from the bottom required the flame to shoot upwards, though. This, in turn, required us to reorient the flame outlets.

The team also bought several cylindrical bars of aluminum. After a successful test of our new design, we plan to machine a couple out of aluminum — which hopefully won’t be reduced to a smoky pile of ooze.

Currently, the greatest design hurdle is how to remove the igniter from the engine during testing. Since the rocket is attached to the ground and the current igniter design doesn’t move, we’re back to square one — disrupted Mach flow in the engine. (A result of turbulence.) Luckily, we’ve got a crack team of young rocket scientists working on it.

So that’s where we stand! Proof of concept confirmed, future planned out, and a moveable design in the works. Just in time for our rapidly-approaching testing timeline.

News

Ready, Set… Launch Stand!

April 3, 2019June 5, 2020
by Dakota

A few weeks ago, we shared how excited we were about our truss being delivered. Now, the fun of building it.

Throughout our interview with techdrawer this past Saturday, Nathan was hard at work assembling the launch stand that our truss will stand on. When our day with techdrawer came to a close, he convinced Dakota and Ben to run through the hoisting process with him.

You can see the launch stand in the photo below to the right of the blur-that-is-Nathan. It’s rectangular and made of steel.

Behind the Griffith Building preparing to hoist the truss onto the launch stand.

The hoisting process involved several meters of cable, two steel structures, nineteen cinder blocks, three humans, one ladder, and three three-meter lengths of aluminum truss.

After bolting the lengths of truss together, we lifted it with an engine hoist and attempted to lever it up with cables and pulleys. The first attempt didn’t go so well. The truss ended up balanced on Dakota’s head while Ben, up the ladder, steadied it and Nathan retied it to the hoist with a complicated series of climbing knots

The final product. Excited Nathan, to boot.

72 hours later, CPR tried once again. We had a modified launch stand, two more Mechanical Engineering majors, and better lighting to help this time. And were we successful? Well, Nathan’s smile in the picture above should answer that!

Uncategorized

Changing Plans

February 28, 2019June 5, 2020
by Dakota

If you look at our BOM (Bill of Materials, keep up!) you’ll catch us in the middle of a very important decision. How are we going to test our rocket?

The Purpose:

To be sure our design works, we need to have data on-record from a simulated run. This includes measuring the lifting force generated from combustion, the temperature of the engine chamber, and the fluid pressure at a few key points along the plumbing.

It’s also an excellent chance to test our dump, abort and kill sequences in case of emergency down the line.

Plan A:

From Day One, it’s been clear we would need to test the full stack. Otherwise, how could we be convinced it would work before launch? Since our propulsion system is pressure-fed, the tanks need to be tested vertically. (If the rocket were horizontal, our high-pressure helium would be able to flow right through the tanks when they’re half full, rendering the test futile.)

Proof that a horizontal test is no good. We would lose pressurant before we were halfway done.

This means we have to test vertically. Right-side up. Which, with rockets, is also the direction you point them if you want them to leave the ground. Not as much the plan, with a static fire test.

To get around this pesky bit of physics, the team designed, modeled, and specified the materials in our BOM for a full-height, vertical test stand. Essentially, we designed a cylindrical sheath (for containing the rocket) inside a rectangular frame (to provide structure) weighed down with water, sand, and concrete (so it didn’t fly away).

A full CAD render of our initial vertical test stand, complete with counterweight barrels.

The Problem:

Upon igniting the engine, the nose of the rocket would be forced upwards into the integrated force sensor. This is unrealistic launch behavior, since it puts the entire rocket in compression. Alternatively, the rocket pushing upward into the stand can be viewed as the stand forcing the rocket down

Plan B:

Back to the drawing board. We needed to come up with a test mechanism that would better simulate launch by placing the rocket in tension, rather than compression. As it turns out, the best place to turn for inspiration is still the Internet.

The verdict? “Tie it down.” Plain and simple. All that’s needed is a rocket, something tall to hang it from, and a few (very strong!) wires to secure it to the ground. It may sound silly, but there are plenty of videos detailing the process and showing positive results.

A quick sketch of our new vertical testing plan.

It requires less logistically, too, as it no longer requires us to maneuver an expensive rocket inside a bulky steel cage. Sold.

What Now?

Now we continue the process of finding a place to launch. We have yet to nail down an official location, but we’re zeroing in pretty quickly. (A few amazing spots have jumped out at us this week and we’re following up.)

And after that? We build, we go, we test.

Uncategorized

It Go Up, It Come Down… Slower

December 18, 2018June 5, 2020
by Dakota

Imagine it’s June 2019. Castle Point Rocketry is on the launchpad at Spaceport America.

The timer goes *beep*. The valves go *click*. The propulsion system goes *ffffshshshhhh*. The engine goes *bbbbhgggghgggghhh*. The rocket goes up. The engine stops. The rocket hits 100km. (The ground crew cheers.)

The rocket turns over and comes back down… and luckily isn’t traveling at terminal velocity when it hits the ground. Why? Our friends at Fruity Chutes, Inc.

After a rigorous set of tests carried out in our Global HQ on Stevens campus, we were satisfied that Fruity Chutes, Inc. had made us suitable chutes.

For those unfamiliar with our current design, we will be employing a double-chute system. Way up in the uninhabited region of the atmosphere, our handy nosecone will pop off and deploy a drogue chute. This helps make sure the rocket doesn’t tumble and snap in two. Much closer to the ground, our bigger chute (not shown) will snap out of hiding, adding drag to give our rocket enough air resistance to fall at a slow enough pace that we can track it and make sure it lands in one piece.

Thanks, Fruity Chutes. We couldn’t do it without you.