Thursday, July 28, 2016

Orders from on High

Welp. The guys we are launching our rockets with are a touch nervous about a bunch of college students bringing rockets sporting G-motors to national forest for launch, and asked us to reduce our target apogee to 1,250 feet. Not much we can do about that except comply. Now it gets interesting!

After a short redesign, our fins have grown, and we have decided to attach 37.6 grams of weight to our motor mount. Yes. The motor mount. Down by the bottom of the rocket. This is to offset the insane stability resulting from having 14-inch-long, 5-inch-high fins cartoonishly jutting out of our rocket. And this was necessary after already moving our fins forward a quarter inch.

I can't say I'm displeased with this, since it does let us use even more ridiculously large fins, but their size makes me a little nervous. If they experience too much drag, the potential exists for the fins to rip the body apart. We plan on mitigating this partially with a 5-inch fin tab bonded to the motor mount, plus another 4 inches of root cord bonded to the rocket tube. We also will create a fillet between the fins and the body tube to help stabilize the fins and distribute any forces originating from them. I just hope no serious vibrations set in. The rocket should look amazing, but if it doesn't fly safely, it will be for nothing.

The next update should include pictures of our construction progress.

Saturday, July 23, 2016

Rocket Design Competition: Summer 2016 Begins!


It's that time again!

And as Project Chair for the AIAA (American Institute of Aeronautics and Astronautics) at UCF, I find myself viewing the Rocket Design Project in a slightly different light. It's still the same ball of fun - design a rocket to meet a specific goal, model it's flight, build the rocket, launch the rocket and measure your performance against your model and the goal - but seeing the behind the scenes, I understand some of the limitations that have been placed on the project this summer.

Because the project is being completed in half the time, there are more design restrictions to ensure rockets that will fly safely. Additionally, we are launching in a national forest, so the risk of starting a fire is a touch higher. So I'll concede and not aim for 2,200 feet like I was planning. Maybe next semester. They are also basically only letting us design our fins, this time. No cutting down (or completely discarding...ehem) body tubes or motor tubes. But since our goal is to get as close to 1,500 feet (457.2 meters) as possible, we want the weight. We are using the same formula as last time, although I want to modify it to account for any crookedness in the launch rod and do a weighted average of it and OpenRocket's prediction. We are also using SolidWorks - which I am trying to remember after using nothing but Creo Parametric for about six months now - to obtain a coefficient of drag via FlowSim.

So summary completed, it's time to talk about our plan. Our team intends to run headlong off a cliff and never look down, because that's how you fall! I'm not saying that I tried to get permission to launch a small anvil-shaped payload that would also serve as our weight, or that our rocket will be a dismal failure, either. But I am suggesting that if it does fail, no one should be surprised. After all, it is an ACME rocket....

"An ACME rocket?" I hear you say. Yes. The ACME Rocket Team is attempting to produce one ACME rocket (probably less the cross-hairs) this semester, slip it past all inspections, and see just what it does. Powered by a G40-7W, it will do something. And it will be memorable. We are hoping it'll be the good kind of memorable.

At this point, we have created a model of the rocket in OpenRocket, a rather nice open source program for modeling the flight of rockets. While it's predictive capabilities are pretty good, it does tend to be about 10% optimistic, so we are going to also do hand calculations and use a weighted average of the two to set our weight. But for now, we have a rocket design and fin design that will overshoot the mark. Once we get our hand calculations going, we will add weight to lower ACME 1's apogee and tweak its stability. I'm personally aiming for a modeled stability of 1.3 calibers, so any slop in manufacturing won't push us too stable or unstable.

I've also been working up a CAD of our rocket in SolidWorks. This has been a "fun" process, especially since I never tried to make such curvy fillets between things like concentric tubes (launch lugs). The process has been a good learning experience, and by that, I mean I have lost much hair and a touch of sanity over this. So where does the design stand right now? Right about here:


So what do you think? Does it look like an ACME rocket? Is the inspiration at least present? Heck, do you think this will get off the launch pad?

Thursday, July 21, 2016

Peryton

CER 57 (OR 42 and PR 15)
A loud snorting sniff rang through the treetops. Jack heard the scuffle of rabbits and squirrels running for their dens. Another sniff, closer this time, sent the boar he was stalking into a startled retreat. Then with a swift stoop, the peryton struck Jack, grabbed him by the belly and thigh, and lifted the boy into the air.
Perytons are omnivorous beasts with the front half of a stag and the back half of a bird. They are fleet of foot and swift of wing, often taking to flight when startled. Perytons supplement their largely herbivorous diet with protein from small deer, lambs, and other mid-sized mammals. They have been known to take children when
ST: 18                                                     HP: 18                                                    Speed: 6.00
DX: 13                                                    Will: 10                                                  Ground Move: 7/14
IQ: 4                                                       Per: 12                                                   Air Speed: 14/28
HT: 11                                                    FP: 11                                                     SM: 1 (4.5 feet)

Dodge: 10                                             Parry: N/A                                             DR: 2 (Tough Skin)

Bite (14): 1d crushing. Reach C
Hooves (14): 1d+2 crushing. Reach C, 1.
Talons (14): 1d+2 cutting or impaling. Reach C.
Antlers (14): 1d+4 impaling. Reach C, 1.

Traits: Bad Sight 4 (Motion Sensitive); Bad Temper (12); Discriminatory Smell; Flight (Cannot Hover, Winged); Night Vision 6; Panic (12); Parabolic Hearing 2; Perfect Balance; Peripheral Vision; Quadruped; Temperature Tolerance 1 (Cold); Terrain Adaptation (Undergrowth); Ultrahearing; Wild Animal.
Skills: Brawling-14; Intimidation-10; Jumping-12; Stealth-12; Swimming-11; Wrestling-14.
Encumbrance: None 64.8 lbs.; Light 129.6 lbs.; Medium 194.4 lbs.; Heavy 388.8 lbs.; Very Heavy 648 lbs.