prototype Archives - Castle Point Rocketry

News

Recent Developments

August 2, 2019June 5, 2020
by Dakota

The rocket you’ve seen in photos isn’t complete. In the weeks since testing, we have received good news regarding our remaining parts. Three main pieces of the rocket remain in fabrication: (1) the nose cone (2) the fins (3) the fuselage.

Nose Cone

In order for our rocket to reach the Karman Line, it needs to pierce the atmosphere. A flat top is inconducive to flight, since particles of air would slam into the top of the rocket and slow it down. On the other hand, an inverted cone would shed air particles like a boat’s hull through water.

Our cone, which is being turned out of a titanium sheet, is currently in the final stages of completion. Though we don’t have photos of it, the cone will be ready by next week.

Fins

As the rocket goes upwards, a certain amount of spin will be added to its flight. Spin is necessary to guide it in a general upwards direction — a flight without rotation could easily complicate and meander off course. However, since spin requires energy, too much spin can shorten the rocket’s distance traveled. In order to find middle ground, we designed fins to assign a fixed amount of spin.

These fins will live at the bottom of the rocket, 90 degrees from one another, just above the engine. Designed with a very slight tilt, they will ever so slightly nudge the rocket into a slow spin. They were precision-machined for us on a 5-axis CNC machine. (That’s pretty expensive stuff.)

Fuselage

The fuselage, the “skin” of the rocket, is the single largest component. Essentially a really wide pipe, this carbon fiber composite cylinder was designed to slide over the outside of our aluminum air frame. (The air frame can be seen in various photos of our rocket.) Since it is both large and rigid, the fuselage also houses our antenna.

The fuselage runs the entire length of our rocket — from nose cone to fins. It keeps all of the guts of the rocket inside the air frame. Most importantly, it provides a smooth outer surface to reduce vibration and aerodynamic drag.

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.

Uncategorized

Full Circle

February 12, 2019June 5, 2020
by Dakota

One of the most competitive facets of our rocket is the engine assembly. Rather than the hundreds (and sometimes thousands!) of parts used to create a traditional rocket engine, our team has streamlined the process into just two: an injector and a nozzle.

Since they’re so integral — and so specialized — we’ve spent hours upon hours designing, modeling, and simulating these parts. And we’ve come full circle.

Phase One: Solidworks

The CAD starter kit for any Stevens engineering student, Solidworks helped us make our first few rounds of injectors. It was pretty cool. Tom spent a lot of time on it.

Injector, Mk. 1. It was bulky, but it got the job done.

Phase Two: COMSOL

Once happy with the geometry, we needed to simulate fluid flow through the manifold. What better software to use than a COMSOL, taught to grad students and marketed as a multi-physics program with a hefty computational fluid dynamics (CFD) engine. Dakota’s self-taught COMSOL regimen came to a standstill when, no matter how finely we meshed the part, physics kept saying, “Nope.”

COMSOL needed the injector flipped inside out. Crazy, right? This part seemed okay…

… But this one obviously had some problems.

They ended up both not working out. One kept growing gnarly spikes, the other had faces that wouldn’t meet up. In the end, no amount of curve smoothing could fix it.

Phase Three: Ansys Fluent

So, what now? Let’s try another CFD! Stevens also offers Ansys to its students, which comes with the handy Fluent plug-in. Abe and Dakota worked on modeling the part in early January, only realizing after returning to campus why it wouldn’t work: Even when simplifying the models by excluding symmetrical pieces, the parts were MUCH, MUCH too big for our Ansys versions to handle. (If years of math has taught me one thing, it’s that 1.1 million “cells” is larger than 512 thousand “cells.”)

Phase Four: Back to Solidworks

The most recent iteration of the injector. We’ve come quite a long way!

We were lost. What do we do? Our school’s CFD programs weren’t working. We had tried simplifying the parts to no avail. Were we just going to hope our applications of what we read in NASA journals would work? Would our rocket engine be held together by dreams and back-of-the-napkin calculations?

Of course not. In the words of Professor Aziz, who teaches courses in Modeling and Simulation at Stevens, “You started
in Solidworks. Why did you leave?”

This simulation tracks individual particles traveling through the injector manifolds. Red means high speed, blue means low speed. Good news: They don’t stop!

So we’ve come full circle. We’re back where we started. We’ve been running fluid flow simulations fairly smoothly, these last couple of weeks. Sure, we keep iterating and optimizing. But at least it’s all built-in, now.

And boy, are the simulations colorful.

News

Prototyping!

November 15, 2018June 5, 2020
by Nate

The team has been busy developing and testing prototypes of critical sub-systems. Most recently the team completed pressure testing a scale model of our 3D printed engine! This print allowed us to learn about the way our design geometry interacts with the 3D printing process. The team was able to gather a significant amount of data from the print and subsequent tests. We used this data to refine our design and improve our printability.

The avionics team has also been working on prototyping. Pictured below is the first iteration of our flight computer! The flight computer will handle all flight functions of the rocket, including actuators and data acquisition.