February 2019 - Castle Point Rocketry

Designing a Circuit Board

February 28, 2019June 5, 2020
by ben

Over the past few weeks, we have been developing our first version of our Printed Circuit Board (PCB). We chose to use Eagle, a PCB Design Software, as it had an easy learning curve as well as an easily attainable educational license. In Eagle, we had to first design and import all the different electronic components that were going to be used into the rocket. We then had to figure out the correct electrical requirements for each component and how to link up each one correctly to the entire system.

The next step was to design the PCB layout itself. We started off with a circular design so it would fit into the rocket base. We then traced the connections so that they didn’t interfere with each other or cross each other. The blue and red lines below show different “levels” of connection. The red traces are the top copper connections, while the blue traces are the bottom copper connections.

We’ve spent a lot of time on it so far, but this is still only our initial design. It still needs to go under testing and multiple iterations to be ready for launch day.

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

Impinging Jet Test #1

February 22, 2019June 5, 2020
by Dakota

In order for our preferred combustion theory to happen correctly, we designed the injector to shoot multiple iterations of two miniature jets at one other. When the jets collide a few millimeters into the body of the engine, the liquid spreads out into a “droplet fan,” making it easier for the fuel and oxidizer to mix. (And ultimately, burn.)

The CAD was designed, the part was printed — all that remained was to verify it worked. So, three members of Castle Point Rocketry’s mechanical engineering team stayed up into the wee hours of Thursday morning to test our injector.

A five-gallon water jug, some flexible tubing, and one high-speed camera later, the team had a pretty good idea that our brain child was a go. The test differed from final implementation in five keys ways, but the fact that it didn’t — well, explode — is a good sign.

(1) The test was run on an 85% scale model printed on campus at Stevens’s PROOF Lab. (2) Our final injector will be solid metal but the test part was made of plastic shells. (3) We ran a lower operating pressure and fluid flow rate than the real part will encounter. (4) The part was not meticulously deburred before testing. Little shards of print plastic could have been partially obscuring the outlet orifices. (5) Water was used as our test fluid but the rocket will burn jet fuel in pure oxygen.

A still from a test of the model’s liquid oxygen manifold.

Over the course of the day (and night), six runs were performed over a range of water pressures. The first two, performed in a lab sink, were a public spectacle for the whole team. Monica, our resident injector design chemical engineer, spent most of that time with her head in the sink watching the impingement for defects.

Our next steps: Print a new model and find a test liquid with properties closer to that of jet fuel.

You can find a nice slow-motion video on our Facebook page (http://www.facebook.com/CPRocketry/).

Uncategorized

It’s Official!

February 22, 2019June 5, 2020
by Dakota

The Experimental Sounding Rocket Association (ESRA) has recognized Castle Point Rocketry as a team at this year’s Spaceport America Cup.

This hit our inbox late last week:

Teams 200, 201, 202, and 204, we’ll see you there.

Uncategorized

Snow Day!

February 12, 2019June 5, 2020
by Dakota

When most Stevens students get an e-mail saying the day’s classes have been cancelled, they celebrate because it gives them a free day to relax, play Super Smash Bros., or whip up a nice long meal.

Castle Point Rocketry celebrated because it gave us a full day to meet.

So here we all are, gathered together in Dakota’s apartment, calculating blast radius, zeroing in on a test site, and finalizing a plumbing and instrumentation diagram. (Hopefully, the former won’t ever be needed — and the latter is on its last iteration.)

Stay tuned for more exciting news. Until then, we’re holed up hiding from the cold!

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.

Uncategorized

New Year, New Injector II

February 8, 2019June 5, 2020
by Nate

After a phone call with our printing partner SLM, we have made a few final tweaks for printability to our nozzle and injector. Our engine is now fully self-supporting. This is a huge step forward as we continue to run simulations and refine the design’s performance. Very soon, we will be sending finalized part files out to be printed in Inconel.

Uncategorized

Carbon Fiber (almost) Composite

February 1, 2019June 5, 2020
by Nate

One of the really exciting features of our launch vehicle is the carbon fiber composite fuselage. Woven or braided carbon composites have structural properties similar or better than steel, at a fraction of the weight. Our team has partnered with A&P Technology to source the braided tubing for our composite. This stuff is cool!

The carbon braid we’ve selected from A&P has a braid angle designed to take much of the force the rocket will experience in flight. This allows us to make the whole rocket ultra light. In the coming days the raw carbon braid will be shipped to our manufacturing partner and infused with a resin to make a super strong and light composite. Stay tuned for more!