We are still in ‘Space Town’ at Space Center Houston’s SEEC conference, and shoulder-rubbing with astronauts leaves little time for blogging. So we have borrowed this space-themed item from the latest issue of HackSpace magazine in which they show us some cool homemade rockets.
A rocket maker keen to make use of thrust vector control (TVC), Cole Purtzer heads up Delta Space Systems. Improving on his previous Frontier rocket, the one-metre-tall Unity is constructed from carbon fibre. It stabilises itself in flight with the use of a servo-actuated TVC mount – made with machined shoulder screws pivoting on ball bearings, this has a range of ±12°.
To ensure a gentle return to earth, a parachute is automatically deployed by a servo-driven mechanical ejection system – which can also be tested on the ground, pre-launch.
In addition, Unity features a new avionics unit that incorporates a high-res gyroscope and accelerometer package, along with a BMP280 barometer to determine vehicle state. A 4K camera can be mounted on the back of the PCB for in-flight footage.
After several successful test flights, Cole has moved up to a larger G25 rocket motor to reach higher altitudes – he’s now aiming for 250 metres.
Scout F rocket
When Joe Barnard set out to build a rocket that could land safely back on terra firma, SpaceX style, little did he know that it would take him seven years. “I wouldn’t have done it if I knew it’d take so long,” he admits, “but I’m glad I did it anyway. There’s this weird benefit to being naive about a daunting project because the thought that you’re ‘almost there’ keeps you motivated when things aren’t working.”
Shunning the fins found on many a model rocket, Scout F is built around the concept of thrust vector control (TVC). “Landing a rocket requires some type of attitude control at slow speed and fins only work when the rocket is moving fast. Right when the rocket is about to touch down you need a way to keep it pointed upright, so thrust vector control seemed like a straightforward way to solve that problem.”
To this end, Joe created a thrust vectoring mount from machined aluminium to fit around the rocket motor, rotated by servos to control the direction of thrust. He also ended up designing a custom flight controller board, Signal R2 (available from his BPS.Space website).
While the project involved a bunch of elements, Joe tells us the most challenging part was the software. “Determining the rocket’s orientation on the ground and in flight is a rabbit hole of problems, knowing exactly how high and how fast the rocket is moving is way more complex than just having good sensors, and all of the logic related to when the motor needs to light, how to throttle the motor [using a pair of ceramic pincers], and how to move through different flight phases is really tricky.”
Reach for the stars
After finally landing a rocket, Joe’s next big goal is to soar a whole lot higher than Scout F’s 30-metre altitude: he aims to build a ‘space shot’ rocket over the next few years. “Going above 100 km is a goal for lots of amateur rocketeers as it puts you above the Kármán line, which is the internationally recognised boundary of space. It’s sorta the final boss of amateur rocketry. It’s a major challenge for lots of reasons, but some of the big issues are the speeds the rocket needs to survive, and having powerful enough rocket motors to get you there. For a rocket using solid motors with fins for stabilisation, it’s hard to make that happen without going at least Mach 4, sometimes closer to Mach 5, which puts a crazy amount of stress on the vehicle.
“As for the motors, depending on how much your rocket weighs, there aren’t many commercial options, which means you have to manage building a controlled explosion yourself, without, you know… exploding yourself in the process.”
Joe has come a long way since the days of launching model rockets with his dad when he was a kid, and the thrill never fades. “You get this really cool feeling seeing something you built fly. Even when it doesn’t work perfect, it’s very rewarding.”
For rocketry beginners, he advises starting out with a kit from Estes Rockets. “Rockets are expensive, but you can grab a small kit from a hobby shop with everything you need for under $50. You can do a ton of experimentation and learning at the small scale without spending hundreds or thousands of dollars, and it’s easy to fly those rockets at most public parks. I did lots of small projects getting started that way, and it’ll be a lot more fun and rewarding than trying to build something massive right off the bat.
Build a rocket
If you feel inspired to launch your own rocket, check out the big feature back in HackSpace #12. It’ll give you lots of useful information on how to get started, including how to design your own personalised rocket using OpenRocket.
Flat pack rocketry
Rockets don’t have to be high-tech or expensive. In HackSpace #60, Jo Hinchliffe took us through how to build a mini ‘flat-pack’ rocket from bits of balsa wood and plywood. He used a similar lo-fi approach to make a swing-wing rocket glider in issue 56, too.